🧠 Unit 1: Biological Bases of Behavior 🧠
🧠 Unit 1: Biological Bases of Behavior 🧠
Explain the relationship between heredity and environment in shaping behavior and mental processes.
Differentiate among the subsystems of the human nervous system and their functions.
Explain how the structures and functions of typical neurons in the central nervous system affect behavior and mental processes.
Explain how the basic process of neural transmission is related to behavior and mental processes.
Explain how psychoactive drugs affect behavior and mental processes.
Explain how the structures and functions of the brain apply to behavior and mental processes.
Explain how the sleep/wake cycle affects behavior and mental processes throughout the day and night.
Explain how the process of sensation is related to behavior and mental processes.
Explain how the structures and functions of the visual sensory system relate to behavior and mental processes.
Explain how the structures and functions of the auditory sensory system relate to behavior and mental processes.
Explain how the structures and functions of the chemical sensory systems relate to behavior and mental processes.
Explain how the structures and functions of the touch sensory system relate to behavior and mental processes.
Explain how the structures and functions of the pain sensory system relate to behavior and mental processes.
Explain how the structures and functions that maintain balance (vestibular) and body movement (kinesthetic) relate to behavior and mental processes.
Introduction to Psychology
Psychology is the science of behavior and mental processes. As psychology became more popular, new approaches emerged when studying the mind and behavior.
Heredity
Biological Approach to Psychology
One of psychology's largest and most highly contested debates is the nature versus nurture issue, arguing which plays a greater role in psychological traits or behaviors - genes and heredity or environment?
The biological approach to psychology focuses on how the body and brain enable emotions, memories, and sensory experiences and how our genes and heredity influence our individual differences.
Everything psychological is biological.
Breakdown of Genes & Heredity
Chromosomes: threadlike structures made of DNA molecules that contain the genes
DNA: a complex molecule containing the genetic information that makes up the chromosomes
Genes: biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins
Genome: the complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes
Molecular genetics: the subfield of biology that studies the molecular structure and function of genes
Heritability: the proportion of variation among individuals in a group that we can attribute to genes
Epigenetics: the study of environmental influences on gene expression that occur without DNA change
Behavior Genetics
If a musician's children grow up to be superstars, can we attribute their talent to genes or environment?
Behavior geneticists are those who study the relative power and limits of genetic and environmental influences on behavior.
Heredity: the genetic transfer of characteristics from parents to offspring
Environment: every nongenetic influence, from prenatal nutrition to the people and things around us
Behavior geneticists explore the genetic and environmental roots of human differences. Evolutionary psychologists, however, focus on what makes us alike as humans, primarily by exploring the principles established by Charles Darwin.
Natural selection: the principle that inherited traits that better enable an organism to survive and reproduce in a particular environment will (in competition with other trait variations) most likely be passed on to the succeeding generations
Mutation: a random error in gene replication that leads to a change
Twin & Adoption Studies
Evolutionary psychologists presume all human behaviors reflect the influence of physical and psychological predispositions that helped human ancestors survive and reproduce. To study this, researchers observe twins.
Identical vs. Fraternal Twins
Identical or monozygotic twins develop from a single fertilized egg that splits, meaning all the genes are the same.
Fraternal or dizygotic twins develop from different eggs that were fertilized simultaneously, so they share the same genes as siblings but are not identical.
Twin studies are a favorite of psychologists because they provide the perfect opportunity to test the nature vs. nurture debate. Identical twins raised in the same household should be the same, right? Not always. Just as identical twins separated at birth and raised in different environments often have many similarities.
The nervous system is the body’s speedy, electrochemical communication network, consisting of all nerve cells and is divided into several smaller systems based on function.
Central nervous system (CNS): brain and spinal cord
Peripheral nervous system (PNS): sensory and motor neurons that connect to brain and spinal cord
Autonomic nervous system: controls involuntary functions such as heartbeat, digestion, breathing, etc.
Sympathetic nervous system → fight or flight response; Automatically accelerates heart rate, breathing, dilates pupils, slows down digestion
Parasympathetic nervous system → rest and digest; Automatically slows the body down after a stressful event
Somatic nervous system: controls voluntary functions
Afferent Nerves: sensory neurons
Efferent Nerves: motor neurons
Interneurons: neurons in the brain and spinal cord that serve as an intermediary between sensory and motor neurons; carry info around the brain for processing.
Reflexes: automatic responses to stimuli; sensory neurons take info up through the spine to the brain → Some reactions occur when sensory neurons reach just the spinal cord.
Enteric Nervous System: directly controls the gastrointestinal tract, pancreas, and gallbladder; contains efferent, afferent, and interneurons
The nervous system is made up of billions of neurons, or nerve cells. While there are several different types of neurons, their key components are the same:
Cell body: contains nucleus & DNA
Dendrites: receives signals from other neurons
Axon (covered in Myelin Sheath: insulates & protects axon): carry signals from one end to the other
Axon Terminals/Terminal Buttons: send signals to the next neuron
Schwann cells produce myelin for the myelin sheath and the Nodes of Ranvier are the spaces between Schwann cells.
Glial cells (glia) are support cells for the nervous system, providing extra protection and nourishment to neurons. If nerve cells are queen bees, glial cells are the worker bees.
Neurons transmit messages when stimulated by our senses or by neighboring neurons. Although this process has several steps, it happens in a fraction of a second.
When not firing (or at rest), a neuron has a slightly negative charge → resting potential. The ions are aligned or polarized.
If stimulation reaches the threshold (minimum stimulation needed to trigger a neural impulse), a neuron will fire. When firing an impulse, a neuron is active and ions are exchanged → action potential. The ions are scrambled or depolarized. All-or-Nothing Law/Response: a neuron’s reaction of firing or not firing is not determined by the strength of stimulation, as long as the threshold is met
Before a neuron can fire again, the ions need to return to their original position, or repolarized. This brief pause between firings is called the refractory period.
Once polarized, the neuron is back to resting potential.
Communication between neurons is chemical, while communication within a neuron is chemical, so a conversion from electrical energy to chemical and back again has to take place with each message. Axon terminals convert electrical signals to chemical messengers or neurotransmitters. These neurotransmitters are released into the synapse or synaptic gap, a small space between the neurons. Once they reach the dendrites of the next neuron, the neurotransmitters are absorbed and the chemical signal is converted back to an electrical one, which is then carried down the axon. Once the conversion is complete, the neurotransmitters are released by the neurons and travel back across the synapse to be reabsorbed by the axon terminals, in a process called reuptake.
Neurotransmitters are the chemical messengers of the nervous system. Different neurotransmitters serve a different function, and incorrect amounts can cause difficulties with movement, memory, and mood. Many drugs work because they either increase/mimic a neurotransmitters action (agonists) or block receptor sites (antagonists). Reuptake inhibitors block the reuptake process, leaving the drug/neurotransmitter in the synaptic gap longer.
The oldest part of the brain is the brain stem, found at the base of the skull above the spinal cord. Often referred to as the "reptilian brain", the structures within the brain stem are responsible for automatic survival functions.
Reticular Formation: a nerve network that travels through the brainstem into the thalamus and plays an important role in controlling arousal
If severed or damaged, you could be in a state of permanent sleep or wakefulness.
Medulla: the base of the brainstem that controls breathing and heartbeat
If severed or damaged, you’ll most likely die or be on life support.
Pons: Connects hindbrain, midbrain, forebrain together; involved in respiration and REM sleep, also serves as a communications and coordination center between the two hemispheres of the brain
Next to the brainstem is the cerebellum or “Little brain”, which coordinates movement and balance, processes sensory input, judgment of time, and enables nonverbal learning and memory.
One of the first parts of the brain impacted by alcohol, thus explaining why people stagger and struggle to react quickly when intoxicated.
Above the brainstem is the thalamus, which serves as the sensory “switchboard”, directing messages to the sensory receiving areas in the cortex and transmitting replies to the cerebellum and medulla.
Receives sensory information from all senses except smell
At the core of the brain is the limbic system, a series of structures associated with emotions and drives.
Amygdala: responsible for survival emotions of fear and aggression
Hippocampus: responsible for processing and storing explicit memories of facts and events
Hypothalamus: below the thalamus; direct several maintenance behaviors, like eating, drinking, and maintaining optimal body temperature, helps regulate the endocrine system via the pituitary gland, and is linked to emotion and reward
Connecting the two hemispheres together is the corpus callosum, a network of fibers allowing for communication between both sides of the brain and body.
Can be severed as a treatment for epilepsy, but has some interesting effects (see split-brain studies)
Any areas of the cerebral cortex that are not involved in primary motor or sensory functions, but are rather involved in higher mental functions such as learning, remembering, thinking, and speaking are known as association areas. These areas help us produce a meaningful perceptual experience of the world, enable us to interact effectively, and support abstract thinking and language.
The cerebral cortex is the intricate fabric of interconnected neural cells covering the cerebral hemispheres that functions as the body’s ultimate control and information-processing center. It plays a key role in memory, attention, perceptual awareness, thinking, speaking, and consciousness, and is organized into lobes based on function:
Frontal
Behind your forehead, largest lobe
Involved in our executive functions:
Ability to recognize future consequences
Making judgements
Planning & decision making
Abstract thought
Personality
Contains motor cortex: sends signals to our body controlling muscle movements.
Contains Broca’s Area: responsible for controlling muscles that produce speech
Broca’s Aphasia: problems with fluency in speech production due to damage
Parietal
Top of the head
Receives sensory input for touch sensations (pain, pressure, temperature) and body position
Contains somatosensory cortex: specified area of the parietal lobe that takes in sensory input from corresponding body parts
Angular gyrus: written language and number processing, spatial recognition, and elements of memory
Temporal
Above the ears
Includes auditory areas, each receiving input from the opposite ear (contralateral control)
Contains Wernicke’s Area: responsible for language comprehension
Wernicke’s aphasia: problems with meaning of speech due to damage; the syntax and grammar jumbled
Auditory cortex: organization and processing of auditory information
Assists with memory
Occipital
Back of the head, above the cerebellum
This is why a hit to the back of your head could make you “see stars” or temporarily blur your vision.
Receives information from the visual fields of opposite eyes for visual processing (contralateral control)
Visual cortex: organization and processing of visual information
Your brain is not only sculpted by your genes but by your life. Your brain is constantly changing, reorganizing itself for your needs without your awareness. Neuroplasticity refers to the brain’s ability to change, build, and reorganize after damage or experience. This process is easier for children than it is for adults. The whole “you can’t teach an old dog new tricks” thing.
Although the brain will try to mend itself by reorganizing existing tissue, it sometimes has to produce new neurons, a process known as neurogenesis.
Complications among brain structure/chemistry, damage to the nervous system, and genetic anomalies can lead to neurological disorders such as multiple sclerosis or myasthenia gravis.
While scientists have always been fascinated with studying the brain, a favorite case is that of railway worker Phineas Gage, who in the mid 1800s survived a major brain injury which caused several changes to his personality, behavior, and performance. There are mixed reports of how extensively this accident changed Phineas, but it did confirm different brain regions are responsible for different functions.
Only in recent years have scientists had the ability to view the brain in an non-invasive and painless way. Prehistoric skulls show evidence of trephination, or drilling holes into the skull to “release evil spirits”. In some cases today, skulls will be drilled into and brain tissue destroyed (lesioned), but that is for the purpose of behavior modification and only as a last resort. Otherwise, research on the brain involves the following techniques:
Electroencephalogram (EEG)
Magnetoencephalography (MEG)
Computed tomography (CT)
Positron Emission tomography (PET)
Magnetic resonance imaging (MRI)
Functional Magnetic Resonance Imaging (fMRI)
The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other.
Patients with severe epileptic seizures found treatment in the form of the split-brain procedure, where their corpus callosum was cut. It eliminated their seizures, but caused some difficulty in basic tasks as the two hemispheres couldn’t communicate with each other.
In an early experiment, Gazzaniga asked split-brain patients to stare at a dot as he flashed HE·ART on a screen. Thus, HE appeared in their left visual field (which transmits to the right hemisphere) and ART in the right field (which transmits to the left hemisphere). When he then asked them to say what they had seen, the patients reported that they had seen ART. But when asked to point to the word they had seen, they were startled when their left hand (controlled by the right hemisphere) pointed to HE. Given an opportunity to express itself, each hemisphere indicated what it had seen. The right hemisphere (controlling the left hand) intuitively knew what it could not verbally report.
The endocrine system is the body’s slow chemical communication system, which consists of a series of glands that secrete hormones into the bloodstream. Neurotransmitters are the chemical messengers of the nervous system, and hormones are the chemical messengers of the endocrine system. The nervous system has a quicker reaction, but the sensation quickly fades, while the endocrine has a slower response but lingers longer.
Hypothalamus: brain region responsible for maintaining homeostasis, regulating hunger, thirst, body temperature, and sex drive
Pituitary gland: “master gland”; regulates growth and controls all other endocrine glands (under the influence of the hypothalamus)
Adrenal glands: secrete epinephrine and norepinephrine that help the body’s response in times of stress
Adrenaline is both a neurotransmitter and a hormone.
Thyroid gland: regulates metabolism
Parathyroids: regulate calcium in blood
Pancreas: regulate sugar in blood
Ovary: female reproductive organ, secretes female sex hormones
Testes: male reproductive organ, secretes male sex hormones
Most psychologists define consciousness as our subjective awareness of ourselves and our environment. The strengths and limitations of this awareness are largely debated, and can be altered by outside influences.
Hypnosis
Meditation
Psychoactive Drugs
Sleep & Dreams
Consciousness offers a reproductive advantage by helping us cope with novel situations, read the emotions of others, and follow through on long-term goals. Cognitive neuroscience is the study of the brain activity linked with cognition, including language, perception, memory, and thinking.
At any moment, we are aware of little more than what is in our conscious awareness, but beneath the surface, unconscious information processing takes place simultaneously. This is known as dual processing. If you see a bird in flight, you’ll be consciously aware of which type of bird it is if you know, but unconsciously be taking in information about its color, size, movement, etc. Our ability to take in information about the look and movement of the bird simultaneously is known as parallel processing.
This alternative to this is sequential processing, in which we process one aspect of a problem at a time. This is used for processing new information or solving difficult problems. Move your dominant foot in a counterclockwise direction while writing the number 3 repeatedly at the same time. This difficult task will often result in your foot going in the direction of the writing the number 3 or your hand drawing circles.
Blindsight is a condition in which a person can respond to a visual stimulus without consciously experiencing it. This is used to help explain how those without sight can sense objects in their environment.
Sleep is a periodic, natural loss of consciousness - as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation. In other words, even in sleep, you still have some level of awareness, that’s why you don’t roll off the top bunk, the music from your headphones might end up in your dreams, or why that prank of putting a sleeping friend’s hand in warm water works.
Why do we sleep?
Protection
Recuperation
Restore/rebuild memory
Feeds creative thinking
Growth
What causes problems with sleep?
Age
Newborns need 16 hours of sleep, teenagers need 9, while most adults can survive on 6.
Genetics
Environment
Brain
Suprachiasmatic nucleus (SCN): a pair of cell clusters in the hypothalamus that control circadian rhythm
Pineal gland: adjust melatonin levels
Reticular formation: monitors sleep and wake cycle
Exposure to Light
Sleep is part of our circadian rhythm - our biological clock that regulates our mood, temperature, and arousal through a 24-hour cycle. As morning approaches, our body temperatures rise and we begin to wake up. Our temperature and arousal peak around midday, then start to dip as we approach dusk. This is why most people prefer to sleep in colder temperatures - it helps you fall asleep faster.
Circadian rhythms can be thrown off by a change of time zones (jetlag) or a certain work schedule. They can also vary by age and individual (night owls vs. morning larks).
Other biological rhythms include:
90-minute sleep cycles
28-day menstrual cycles
Annual → Hibernation/Migration
Mating seasons
About every 90 minus, we cycle through distinct sleep stages: NREM or non- rapid eye movement sleep and REM or rapid eye movement sleep.
NREM-1: light sleep, easily awoken → alpha waves
Can experience hallucinations (false sensory experiences) and hypnagogic sensations (bizarre experiences such as jerking with a sensation of falling)
NREM-2: fully asleep → theta waves with sleep spindles (random short bursts of activity) & k-complexes (random tall bursts of activity)
NREM-3: deep sleep → delta waves
REM: body relaxed as if paralyzed but brain as active as if it was awake (paradoxical sleep) → beta waves
Becomes longer & more frequent as night progresses
Vivid dreams occur
REM Rebound: If deprived of REM sleep, a person will spend more time in REM the next time they go to sleep.
After oxygen, food, and water, the thing our body needs most is sleep. If we do not sleep, or do not get enough sleep, our body makes it known to us how badly it needs a break. Research shows that inadequate sleep can make you more likely to:
Struggle with focus and concentration
Gain weight
Get sick
Be irritable and/or depressed
Feel old
Not-so-fun fact: Driving sleep deprived is as dangerous as driving drunk.
Insomnia: recurring problems falling or staying asleep
Narcolepsy: a sleep disorder characterized by uncontrollable sleep attacks; sufferer may lapse directly into REM sleep
Sleep Apnea: a sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings
Night Terrors: a sleep disorder characterized by high arousal and an appearance of being terrified; unlike nightmares, night terrors occur during NREM-3 sleep and are not remembered
Somnambulism: sleepwalking
Somniloquy: sleep talking
Nightmares are emotional dreams, occurring during REM sleep with our bodies still and you are able to remember it. Night terrors affect the body very strongly, causing the heart to pound, breathing rate to increase, and blood pressure rises. You are unable to remember the event, able to move during the episode, and occurs in the first 3 hours of sleep.
Dreams are sequences of images, emotions, and thoughts passing through a sleeping person’s mind. Although dreams can occur at any stage of sleep, they are most vivid during REM sleep.
Why do we dream?
Wish-Fulfillment
Suggested by Sigmund Freud
Dreams are simply ways we play out all of the things we want to do subconsciously-hidden wishes.
Believed in two parts to dreams - manifest & latent content
Manifest content: actual content of the dream
Latent content: hidden or symbolic meaning of the dream
Information Processing
A.k.a problem-solving theory
The most widely accepted theory
Dreams are a way to deal with/sort out the stresses of everyday life
This theory states that we tend to dream more when we are more stressed
Activation Synthesis
Developed by Allan Hobson and Robert McCarley.
Limbic system becomes active as we are in REM and randomly fires
Our cerebral cortex is trying to interpret random electrical activity we have while sleeping
That is why dreams sometimes make no sense
The brain's efforts to make sense out of meaningless patterns of firing in the brain as we sleep
Physiological Function
Dreams provide the sleeping brain with periodic stimulation to develop and preserve neural pathways.
Neural networks of newborns are quickly developing; therefore, they need more sleep.
Cognition
Dreams are the expression of a person's thoughts
A dream is conceived as a pictorial representation of the dreamer's conceptions, usually about himself, other people, the world, impulses, prohibitions, penalties, and conflicts
The reveal the structure of how we envision our lives
Negative Emotional Content: 8 out of 10 dreams have negative emotional content.
Failure Dreams: People commonly dream about failure, being attacked, pursued, rejected, or struck with misfortune.
Sexual Dreams: Contrary to our thinking, sexual dreams are rare. Sexual dreams in men are 1 in 10; and in women 1 in 30.
Dreams of Gender: Women dream of men and women equally; men dream more about men(their buddies or co-workers) than women.
Lucid dreaming: knowing that you are dreaming and occasionally being able to control aspects of your dream
Sleep paralysis a feeling of being conscious but unable to move, occurring when a person passes between stages of wakefulness and sleep. During these transitions, you may be unable to move or speak for a few seconds up to a few minutes.
Psychoactive drugs are chemical substances that alter perceptions and moods. While some psychoactive drugs can be used in moderation to help with concentration or pain relief, others can lead to addiction and substance use disorder (a disorder characterized by continued substance craving and use despite significant life disruption and/or physical risk.
When is drug use a disorder?
Diminished control & social functioning
More is needed to get the desired effect
It is hazardous to use
Dependence/Addiction
Many psychoactive drugs can be harmful to the body.
Psychoactive drugs are particularly dangerous when a person develops an addiction or becomes physically and/or psychologically dependent on the substance.
Factors related to addiction:
Tolerance: diminished psychoactive effects after repeated use
Withdrawal: painful symptoms of the body re-adjusting to the absence of the drug.
impact on daily life of substance use
physical and psychological dependence
Types of Drugs:
Stimulants - excite neural activity
Increase energy, decrease appetite, brief feelings of euphoria
Speed up (stimulate) bodily processes
Ex. caffeine, nicotine, cocaine, amphetamines (meth)
Depressants - reduce neural activity
Increase relaxation and pain relief, decrease mood and arousal
Slow down (depress) bodily processes
Ex. alcohol, barbiturates, opiates (heroin)
Hallucinogens - distort perception
Cause false sensory hallucinations, impair memory, feelings of relaxation and/or euphoria
Ex. marijuana, mushrooms, LSD, ecstasy/MDMA (also a stimulant)
Psychoactive drugs primarily work by stimulating, inhibiting, or mimicking neurotransmitter activity. The prolonged and excessive use of alcohol (also known as alcoholism or alcohol use disorder) can shrink the brain, disrupt memory formation, reduce inhibitions, and slow functioning.
Another state of consciousness is a near-death experience, when individuals report strange sensations or vivid visions following a close brush with death (similar to drug-induced hallucinations).
Hypnosis is a social interaction in which one person (the hypnotist) suggests to another (the subject) that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur. Hypnosis is also described as a systematic procedure that typically produces a heightened state of suggestibility.
In psychology, hypnosis has been used to unlock repressed memories, overcome traumatic experiences, treat phobias, and cure addiction. Some phenomena associated with hypnosis include:
Analgesia: treatment of acute and chronic pain (used by dentists/doctors as a substitute for anesthetic)
Sensory distortions and hallucinations: sensing things that are not present, or failing to sense things that are
Disinhibition: effect of hypnosis that removes boundaries that would typically prevent subject from performing specific actions (social norms, illegal acts, etc.)
Posthypnotic amnesia: supposed inability to recall what one experienced during hypnosis; induced by the hypnotist’s suggestion
Posthypnotic suggestion: a suggestion, made during a hypnosis session, to be carried out after the subject is no longer hypnotized; used by some clinicians to control undesired symptoms or behaviors
Meditation refers to a family of practices that train attention to heighten awareness and bring mental processes under greater voluntary control. There are two types of meditation:
Focused attention: attention is concentrated on a specific object/image/sound/sensation
Open monitoring: attention is directed to the contents of one’s moment-to-moment experience in a nonjudgmental and nonreactive way
Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. All of our senses receive sensory stimulation, transform that information into neural impulses, and deliver information to the brain. Perception is the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Under normal conditions, sensation and perception blend into one continuous process, working together to help you decipher the world around you.
Bottom-up processing: analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information (sensation first)
Top-down processing: information processing guided by higher-level mental processes , as when we construct perceptions drawing on our experiences and expectations (experience first)
While walking through an art museum, you come to the abstract art section. If you used bottom-up processing, you would stare at the piece and try to figure out what the artist was trying to create. If you used top-down processing, you would read the title of the work and look for elements of that in the painting.
The process of converting one form of energy to another (or, in this case, converting sensory stimulation into neural signals) is called transduction.
The field of psychophysics studies the relationships between the physical characteristics of stimuli and our psychological experience of them. In order for a neuron to fire, the threshold to trigger an impulse must be reached. This principle continues with sensation. The absolute threshold is the minimum amount of stimulus energy needed to detect a particular stimulus 50% of the time. The concept of absolute thresholds was studied by Gustav Fechner.
Detection of a stimulus not only relies on the strength of the stimulus, but also our psychological state - our experience, expectations, motivation, alertness, etc. Signal detection theory predicts how and when we detect the presence of a faint stimulus amid background stimulation, thus assuming there is no single absolute threshold and that detection depends on the person. Absolute thresholds deal with detection of one stimulus, while difference thresholds (a.k.a. just noticeable difference) note the minimum difference between two stimuli required for detection 50% of the time.
Ernest Weber described this phenomenon with a new principle - Weber’s law. Weber’s law states that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount.
Consider playing with light dimmers. How much do you need to move the dimmer switch to see something as darker or lighter than before?
Earlier, we stated that if our brain was giving equal attention to all the information it received, we’d go crazy. This is one of the reasons our brain is primed to detect change and ignore constants. Sensory adaptation is diminished sensitivity as a consequence of constant stimulation or exposure.
When you know the water is cold, you are hesitant to jump in, but all the adults say the same thing - “you’ll get used to it after a few minutes”. You jump in, are frozen for a moment, and then start to acclimate to the water.
Up until now, you have ignored much of your senses because they’ve been exposed to constants, but now that I’m bringing it to your attention (the smell of the room or your perfume, the feeling of the clothes on your skin), you notice it again.
Sensory interaction refers to the ability of one sense to influence or interact with another. Two senses that commonly interact with each other are taste and smell. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor.
Stimuli you cannot consciously detect 50% of the time are subliminal, or below your absolute threshold.
Can we be controlled by subliminal messages? Some advertisers sneak subliminal messages into their marketing in hopes of increasing sales.
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Priming is a phenomenon in which exposure to one stimulus influences how a person responds to a subsequent, related stimulus. Through experience, we come to expect certain results. Those expectations may give us a perceptual set - a mental predisposition to perceive one thing and not another.
A visual illusion involves an apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality.
Müller-Lyer: illusion of line length that is distorted by inward-turning or outward-turning corners on the ends of the lines, causing lines of equal length to appear to be different.
Ames Room: Due to the shape of the room-trapezoid, the person standing to the right side of the room appears much larger.
Moon Illusion: moon always appears larger on the horizon than it does overhead
Ponzo Illusion: an optical illusion in which two identical figures are made to appear of different sizes because of the effect of perspective
Light travels in waves, and the shape of those waves influences what we see. Light’s wavelength (distance from the peak of one wave to the next) determines the hue (color). The wave’s amplitude (height) determines the intensity (the amount of energy the wave contains) or brightness. The purity of the wave determines how vivid the color appears.
Light enters the cornea (the eye’s clear, protective layer) and then the pupil (adjustable opening of the eye allowing light to pass through) whose size is determined by the iris (colored ring of muscle tissue). Light is then focused by the lens (transparent structure which changes shape to focus images) on the retina (the light sensitive inner surface of the eye with layers of neurons to convert light into neural impulses). The process of focusing these images is called accommodation. These neural impulses are carried to the brain via the optic nerve.
Rods: retinal receptors that detect black, white, and gray, are sensitive to movement and are necessary for peripheral vision
Cones: retinal receptors concentrated near the center of the retina responsible for daylight/color vision
Fovea: the central focal point in the retina, around which the eye’s cones cluster → where visual acuity is greatest
Blind Spot: the point at which the optic nerve exits the eye so there is an absence of receptor cells
If you have perfect vision, you will have a perfectly spherical eyeball where all images fall perfectly on the retina. Nearsighted/myopic people (those who see things clearly up close, but struggle with things farther away) will have a longer eyeball while farsighted/hyperopic people (those who can clearly see things from far away but struggle with things up close) will have a taller eyeball.
About 1 person in 50 is “colorblind.” That person is usually male, because the defect is genetically sex linked. Most people with color-deficient vision are not actually blind to all colors. They simply lack functioning red- or green-sensitive cones, or sometimes both. Their vision—perhaps unknown to them, because their lifelong vision seems normal—is monochromatic (one-color) or dichromatic (two-color) instead of trichromatic, making it impossible to distinguish the red and green. Dogs, too, lack receptors for the wavelengths of red, giving them only limited, dichromatic color vision.
Feature detectors are nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. For humans, we have specialized feature detectors for faces.
Damage to these feature detectors or the area of the temporal lobe responsible for facial recognition could lead to prosopagnosia (also known as face blindness or facial agnosia)- a neurological disorder characterized by the inability to recognize faces.
This apple is obviously red, right? Of course! But actually, the apple is everything but red, because it rejects the wavelengths we process as red and absorbs the rest. Light waves are colorless but our brain perceives them in color.
Color vision is largely a mystery, but we have some theories to explain how we see a world in color.
Young-Helmholtz Trichromatic Theory states that the retina contains three different types of color receptors for three basic colors - red, green, and blue - which when stimulated can come together to form every color.
Why not yellow? Because when both red and green receptors are stimulated, we see yellow.
But why do people blind to red and green often still see yellow? And why does yellow appear to be a pure color and not a mixture of red and green, the way purple is of red and blue?
Opponent-process theory states that color vision depends on three sets of opposing retinal processes—red-green, blue-yellow, and white-black. As impulses travel to the visual cortex, some neurons in both the retina and the thalamus are turned “on” by red but turned “off” by green. If exposed to one color for an extended period, the opposite will appear in the afterimage.
Stare at the red circle for 30 seconds. Look at nothing else. After the 30 seconds are up, move your eyes to the X. You should see an afterimage of a red background with a green spot.
Audition is our sense of hearing. Like light, sound travels in waves. Sound waves are composed of compression and rarefaction of air molecules. The height of the wave, or amplitude, determines the volume of the sound, measured in decibels. The frequency (number of wavelengths that pass a point in a given time) determines the pitch (highness or lowness of tone).
Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound, or determine the direction of the sound’s source.
When high frequency sounds are experienced too frequently for a single neuron to adequately process and fire for each sound event, the organ of Corti combines the multiple stimuli into a "volley" in order to process the sounds. The volley principle states that groups of neurons of the auditory system respond to a sound by firing action potentials slightly out of phase with one another so that when combined, a greater frequency of sound can be encoded and sent to the brain to be analyzed.
Sound waves are funneled into the auditory canal by the pinna (exterior part of ear). Once in the ear canal, sound waves vibrate the eardrum (tight membrane preceding the middle ear), then the hammer/malleus, anvil/incus, and stirrup/stapes (also known as the ossicles), finally vibrating the oval window of the cochlea (the coiled, bony, fluid-filled tube of the inner ear responsible for transduction of sound). The cochlea is lined with a basilar membrane (a layer of hair cells which convert the sound waves into neural impulses). Neural impulses are carried to the brain via the auditory nerve.
There are two types of hearing loss or deafness:
Sensorineural hearing loss (a.k.a. Nerve deafness): inability to hear due to damage to the cochlea’s receptor cells or to the auditory nerves
Can be caused by repeated/prolonged exposure to loud sounds
Can be helped by a cochlear implant
Conduction hearing loss: inability to hear due to damage to mechanical elements of the ear (parts other than the cochlea)
Can be helped by a hearing aid
Although it has been established that the hair cells along the basilar membrane of the cochlea are responsible for transduction of sound waves, how that occurs is not fully known. Two theories propose how hair cells work:
Place theory states that the pitch of a sound we hear is due to activation of specific hair cells on the basilar membrane (like a piano).
Frequency theory states that the entirety of the basilar membrane vibrates in response to sound, and the speed of the vibration is how we perceive pitch (like a drum).
Touch, our tactile sense, is vital to our development and survival. Contact comfort helps us establish bonds with caregivers, and premature babies have a better chance of survival if they are held. The tactile sensations include pain, pressure, touch, and temperature, and are processed by our parietal lobe.
Pain tells the body that something has gone wrong, usually resulting from damage to the skin and other tissues. Pain begins at sensory neurons known as nociceptors. Melzak and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gate-control theory states that the spinal cord acts as a buffer between pain and the brain, deciding which signals will pass through; pain is a function of the balance between the information traveling into the spinal cord through large nerve fibers and information traveling into the spinal cord through small nerve fibers.
Pain is not merely a physical phenomenon of injured nerves sending impulses to a definable brain or spinal cord area. The brain can also create pain, as it does in phantom limb sensations after a limb amputation. Without normal sensory input, the brain may misinterpret and amplify spontaneous but irrelevant central nervous system activity. As the dreamer may see with eyes closed, so 7 in 10 such people feel pain or movement in nonexistent limbs.
Gustation, or our sense of taste, is a chemical sense. There are five identified taste sensations:
Sweet - helps us identify sugary foods for energy
Sour - helps us identify foods that have gone bad or could make us sick
Salty - sodium is essential for physiological functioning
Bitter - helps us identify poison or foods that could make us sick
Umami (savory) - helps us identify foods high in protein which help grow/repair tissue
Oleogustus - carbs/fats for energy, insulation, & cell growth
The small bumps on the surface of the tongue are called papillae. They serve as our taste receptors.
Olfaction, or our sense of smell, is also a chemical sense and works closely with taste through a process called sensory interaction (when one sense influences another). This is why if you plug your nose or have a bad sinus infection and can’t smell, you also lose your sense of taste.
Odorants enter the nasal cavity to stimulate 5 million receptors in the olfactory bulb to sense smell, and then it bypasses the thalamus and goes straight to the temporal lobe to be processed. Scientists suspect this is an evolutionary trait, as smell is our first indication that food has spoiled and will likely make us ill if consumed. This could also explain why smell is closely connected to memory; if something made us ill in the past, its smell will be a reminder not to eat it again (taste aversion).
The vestibular sense monitors the head and body position, as well as, our sense of balance.
Receptors in the semicircular canals and vestibular sacs of the ear
Works with cerebellum
The sense of our individual body parts’ position and movement is called kinesthetic sense.
Receptors in the muscle tissues and joints
Sensation and perception have to work together to give us a complete understanding of our surroundings, thus each side works in a continuous loop where we begin to think within the body. This is known as embodied cognition - the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.
Consider the phenomenon of synesthesia, where sensory stimulation triggers more than one sense. Have you seen the TikToks of people who see sounds, taste numbers, or hear colors?
Extrasensory Perception (ESP) - claim of perception that occurs without the use of normal sensory channels such as sight, hearing, touch, taste, or smell.
Parapsychology - the study of ESP, ghosts, and other subjects that do not normally fall into the realm of ordinary psychology.
Telepathy -ability to read another person’s thoughts, or mind reading.
Clairvoyance - ability to “see” things that are not actually present.
Precognition - ability to know something in advance of its occurrence or to predict a future event.
Unit 1 Vocabulary
absolute threshold: the minimum stimulation needed to detect a particular stimulus 50% of the time.
accommodation: in vision, the process by which the lens of the eye shifts to focus on a particular object.
acetylcholine: A neurotransmitter involved in muscle activation, memory, and learning.
action potential: a brief electrical charge that travels down the axon of a neuron, generated by the movement of positively charged atoms in and out of channels in the neuron's membrane.
activation-synthesis theory: A theory of dreaming that suggests dreams are the brain's attempt to make sense of random neural activity.
adaptation: the process by which a species becomes fitted to its environment through natural selection
addiction: a complex condition characterized by compulsive drug use or behaviors despite harmful consequences.
agonist: a drug or chemical that enhances the activity of neurotransmitters.
alcohol: A depressant that slows down the central nervous system, impairing cognitive and motor functions.
all-or-none response: the principle that a neuron either fires completely or does not fire at all.
alpha waves: the relatively slow brain waves associated with relaxation and wakefulness.
amplitude: The height of a wave, which determines the loudness of a sound.
amygdala: the limbic system structure involved in processing emotions, particularly fear and aggression.
antagonist: a drug or chemical that inhibits or blocks the action of neurotransmitters.
aphasia: A condition characterized by the loss of ability to understand or express speech.
association areas: areas of the cerebral cortex that are not involved in primary motor or sensory functions but are involved in higher mental functions such as learning, remembering, thinking, and speaking
audition: the sense of hearing
auditory Cortex: The part of the brain that processes auditory information.
autonomic nervous system: the part of the peripheral nervous system that controls involuntary functions like heart rate, digestion, and glandular secretions
axon: the extension of a neuron through which neural impulses are sent.
barbiturates: a class of drugs that depress the activity of the central nervous system, reducing anxiety but impairing memory and judgment.
behavior genetics: the study of the relative power and limits of genetic and environmental influences on behavior.
biological psychology: a branch of psychology concerned with the links between biology and behavior.
biopsychosocial approach: an integrated approach that incorporates biological, psychological, and social-cultural levels of analysis.
blind spot: the point at which the optic nerve leaves the eye, creating a small gap in the field of vision.
blindsight: condition in which a person can respond to visual stimuli without consciously experiencing them.
bottom-up processing: analysis that begins with sensory receptors and works up to the brain's integration of sensory information.
brainstem: the oldest part and central core of the brain, responsible for automatic survival functions.
Broca's Area: A region in the frontal lobe of the brain associated with speech production.
caffeine: A stimulant found in coffee, tea, and many soft drinks that increases alertness and reduces fatigue central nervous system: the brain and spinal cord, responsible for processing and coordinating information.
cerebellum: structure in the hindbrain that helps coordinate voluntary movement and balance.
cerebral cortex: the outer layer of the brain responsible for complex cognitive processes such as thinking, planning, and language.
Charles Darwin: English naturalist who proposed the theory of evolution by natural selection.
circadian rhythm: the biological clock; regular bodily rhythms that occur on a 24-hour cycle.
cocaine: A powerful stimulant drug that increases levels of dopamine in the brain, leading to intense euphoria and increased energy.
cochlea: coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.
cochlear implant: device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.
cognitive neuroscience: the interdisciplinary study of the brain activity linked with cognition (including perception, thinking, memory, and language).
computed tomography (CT): scanning technique using multiple X-rays to construct a 3D image of the brain's structure.
conduction hearing loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.
cones: photoreceptor cells in the retina that are responsible for color vision and fine detail.
consciousness: our awareness of ourselves and our environment.
consolidation theory: The theory that sleep helps strengthen the neural connections that form our memories.
contralateral control: The principle that each hemisphere of the brain controls the opposite side of the body.
cornea: the transparent outer layer of the eye that covers the pupil and iris and helps focus incoming light.
corpus callosum: the large band of neural fibers connecting the two brain hemispheres and carrying messages between them.
David Hubel: Canadian neurophysiologist known for his work with Torsten Wiesel on the processing of visual information in the brain.
delta waves: the large, slow brain waves associated with deep sleep.
dendrites: branchlike extensions of a neuron that receive messages and conduct impulses toward the cell body.
depolarization: The process by which a neuron's membrane potential becomes less negative, leading to the firing of an action potential.
depressants: drugs that reduce neural activity and slow body functions.
dichromatism: A type of color blindness where one of the three basic color mechanisms is absent or not functioning.
difference threshold: the minimum difference between two stimuli required for detection 50% of the time; also known as just noticeable difference (JND).
dopamine: A neurotransmitter involved in reward, motivation, and motor control.
dream: sequence of images, emotions, and thoughts passing through a sleeping person's mind.
dual processing: the idea that information is simultaneously processed on separate conscious and unconscious tracks.
electroencephalogram (EEG): recording of the electrical waves sweeping across the brain's surface, measured by electrodes placed on the scalp.
embodied cognition: the theory that cognition is influenced by the body's interactions with the environment.
endocrine system: the body's slow chemical communication system, consisting of glands that secrete hormones into the bloodstream.
endorphins: neurotransmitters that are natural painkillers produced by the brain.
environment: every nongenetic influence, from prenatal nutrition to the people and things around us.
epigenetics: the study of environmental influences on gene expression that occur without a DNA change.
Ernst Weber: German physician credited with the formulation of Weber's law, which describes the relationship between the magnitude of a physical stimulus and the intensity of its perceived sensation.
eugenics: A controversial and unethical movement aimed at improving the genetic quality of the human population.
evolutionary psychology: the study of the evolution of behavior and the mind, using principles of natural selection.
excitatory Neurotransmitter: A neurotransmitter that promotes the firing of neurons.
farsightedness (Hyperopia): A condition where distant objects can be seen clearly, but close objects appear blurry.
feature detectors: nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.
fMRI: technique for revealing blood flow and, therefore, brain activity by comparing successive MRI scans.
forebrain: the largest and most prominent part of the brain, including the cerebral cortex and subcortical structures.
fovea: the central focal point in the retina, around which the eye's cones cluster.
fraternal (dizygotic) twins: twins who develop from separate eggs and are no more similar genetically than non-twin siblings.
frequency: the number of complete wavelengths that pass a point in a given time.
frequency theory: the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.
frontal lobes: the portion of the cerebral cortex lying just behind the forehead, involved in planning and judgment.
GABA (Gamma-Aminobutyric Acid): The main inhibitory neurotransmitter in the brain.
ganglion cells: Neurons in the retina that relay information from the photoreceptors to the brain.
gate-control theory: the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain.
genes: the biochemical units of heredity that make up the chromosomes; a segment of DNA capable of synthesizing a protein.
genome: the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes.
glial cells: cells in the nervous system that support, nourish, and protect neurons, and play a role in learning and thinking.
glutamate: The main excitatory neurotransmitter in the brain.
gustation: the sense of taste
Gustav Fechner: German psychologist known for his work in psychophysics, particularly his development of Weber's law and the concept of the just noticeable difference.
hallucinations: perceptions that have no direct external cause, arising from disorders such as schizophrenia, sensory deprivation, or drug-induced states.
hallucinogens: drugs that alter perception and cause hallucinations or profound distortions in a person's perceptions of reality.
heredity: the genetic transmission of characteristics from parents to offspring.
heroin: An opioid drug that produces intense euphoria and pain relief, highly addictive.
hindbrain: the lower part of the brainstem, comprising the medulla, pons, and cerebellum, responsible for basic life functions.
hippocampus: a neural center located in the limbic system that helps process explicit memories for storage.
hormones: chemical messengers produced by the endocrine glands and circulated in the bloodstream, regulating the activity of target cells or organs.
hue: the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, etc.
hypnagogic sensations: experiences during the transition from wakefulness to sleep, including hallucinations, muscle jerks, and sensations of falling.
hypothalamus: a neural structure lying below the thalamus, regulating bodily functions such as hunger, thirst, body temperature, and sexual behavior, and controlling the pituitary gland.
identical (monozygotic) twins: twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms.
inhibitory neurotransmitter: A neurotransmitter that inhibits the firing of neurons.
inner ear: the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs, involved in balance and hearing.
insomnia: persistent problems falling asleep and/or staying asleep.
intensity: the amount of energy in a light or sound wave, which we perceive as brightness or loudness.
interneurons: neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs.
iris: the colored ring of muscle that regulates the size of the pupil by controlling the amount of light entering the eye.
jet lag: A temporary sleep disorder that occurs when a person's internal body clock is out of sync with the time zone they are in.
just noticeable difference (JND: The minimum difference in stimulation that a person can detect 50% of the time.
kinesthesis: the sense of the body's position and movement of body parts relative to each other.
lens: the transparent structure behind the pupil that changes shape to help focus images on the retina.
lesion: damage to body tissue, often caused by disease or injury, but can be used to modify behavior by destroying targeted areas of brain tissue
limbic system: set of structures in the brain, including the amygdala, hypothalamus, and hippocampus, involved in emotion, motivation, and memory.
magnetic resonance imaging (MRI): technique that uses magnetic fields and radio waves to produce detailed images of the brain's soft tissue.
magnetoencephalography (MEG): brain imaging technique that measures magnetic fields generated by neuronal activity in the brain.
marijuana: A drug containing THC that alters mood, perception, and cognitive function.
medulla: the base of the brainstem, controlling heartbeat and breathing.
Michael Gazzaniga: pioneering neuroscientist known for his split-brain research, which revealed insights into the functional differences between the brain's hemispheres.
midbrain: small region of the brainstem involved in auditory and visual processing and regulation of motor movements.
middle ear: the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window.
monochromatism: Complete color blindness where only shades of grey are perceived, with no ability to distinguish colors.
motor (efferent) neurons: neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.
motor cortex: an area at the rear of the frontal lobes that controls voluntary movements.
multiple sclerosis: A disease in which the immune system attacks the protective covering of nerves, leading to communication problems between the brain and the rest of the body.
mutation: a random error in gene replication that leads to a change.
myasthenia gravis: An autoimmune disorder that affects communication between nerves and muscles, leading to muscle weakness.
myelin: the fatty tissue layer that encases the axons of some neurons, speeding up the neural impulses.
narcolepsy: a sleep disorder characterized by uncontrollable sleep attacks, often triggered by strong emotions.
natural selection: the principle that heritable traits that better enable an organism to survive and reproduce in a particular environment will most likely be passed on to succeeding generations.
nature-nurture issue: the debate over the relative contributions of genetic inheritance and environmental factors to human development.
near-death experience: an altered state of consciousness reported after a close brush with death, often including out-of-body experiences and feelings of peace.
nearsightedness (Myopia): A condition where close objects are seen clearly, but distant objects are blurry.
nervous system: the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems.
neurogenesis: the formation of new neurons.
neuron: nerve cell; the basic building block of the nervous system.
neuroplasticity: the brain's ability to reorganize itself by forming new neural connections throughout life, particularly in response to learning, experience, or injury.
neurotransmitters: chemical messengers that transmit signals across the synaptic gap between neurons.
NREM sleep (Non-Rapid Eye Movement sleep): the sleep stages characterized by slow brain waves, relaxed muscles, and decreased heart rate and breathing.
norepinephrine: A neurotransmitter and hormone involved in arousal and alertness.
occipital lobes: regions of the cerebral cortex located at the back of the brain, responsible for processing visual information.
oleogustus: A proposed sixth taste sensation for the taste of fat.
olfaction: the sense of smell.
opioids: a class of drugs that act on opioid receptors to produce morphine-like effects, including pain relief and feelings of euphoria.
opponent-process theory: theory of color vision proposing that the brain processes color information in pairs of complementary colors (e.g., red-green, blue-yellow).
optic nerve: the bundle of nerve fibers that carries visual information from the retina to the brain.
parallel processing: the brain's ability to process multiple aspects of a problem or stimulus simultaneously.
parasympathetic nervous system: the division of the autonomic nervous system that calms the body, conserving its energy and promoting rest and digestion.
parietal lobes: regions of the cerebral cortex located at the top of the brain, responsible for processing sensory information such as touch and spatial awareness.
perception: the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
peripheral nervous system: the sensory and motor neurons that connect the central nervous system to the rest of the body, transmitting information to and from the brain and spinal cord.
pheromones: Chemicals secreted by animals that influence the behavior or physiology of others of the same species.
pitch: a tone's experienced highness or lowness; depends on frequency.
pituitary gland: The "master gland" of the endocrine system that regulates other glands and controls various bodily functions.
place theory: the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated.
plasticity: The brain's ability to change and adapt as a result of experience.
positron resonance tomography (PET): a brain imaging technique that measures brain activity by detecting radioactive glucose uptake in active brain areas.
priming: the activation of certain associations, thus predisposing one's perception, memory, or response.
prosopagnosia: A neurological disorder characterized by the inability to recognize faces, also known as face blindness.
psychoactive drug: a chemical substance that alters perception, mood, consciousness, cognition, or behavior.
psychophysics: the study of the relationship between physical characteristics of stimuli and our psychological experience of them.
pupil: the adjustable opening in the center of the eye through which light enters.
reflex: a simple, automatic response to a sensory stimulus, such as the knee-jerk reflex.
reflex arc: The neural pathway that controls a reflex action.
refractory period: a brief period after a neuron has fired during which it cannot generate another action potential.
REM rebound: the tendency for REM sleep to increase following REM sleep deprivation.
REM sleep (Rapid Eye Movement sleep): a stage of sleep characterized by rapid eye movements, vivid dreams, and muscle paralysis.
REM sleep behavior disorder: sleep disorder characterized by the acting out of violent or dramatic dreams during REM sleep.
resting potential: The electrical charge of a neuron when it is not active.
reticular activating system: A network of neurons in the brainstem involved in arousal and attention.
reticular formation: a network of neurons running through the core of the brainstem, involved in controlling arousal and attention.
retina: the light-sensitive inner surface of the eye, containing receptor cells (rods and cones) and layers of neurons that begin the processing of visual information.
reuptake: the reabsorption of neurotransmitters by the sending neuron after they have been released into the synaptic gap.
reuptake inhibitors: Medications that block the reabsorption of neurotransmitters into neurons, increasing their levels in the brain.
rods: retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.
Roger Sperry: A neuropsychologist who won the Nobel Prize for his split-brain research, showing functional differences between the brain's hemispheres.
semicircular canals: Structures in the inner ear involved in maintaining balance and detecting head movements.
sensation: the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
sensorineural hearing loss: hearing loss caused by damage to the cochlea's hair cells or the auditory nerve.
sensory (afferent) neurons: neurons that carry incoming information from the sensory receptors to the brain and spinal cord.
sensory adaptation: diminished sensitivity to an unchanging stimulus over time.
sensory interaction: the principle that one sense may influence another, as when the smell of food influences its taste.
sensory receptors: specialized cells that detect sensory stimuli and convert them into neural impulses to be sent to the brain.
sequential processing: the processing of one aspect of a stimulus at a time, used when we focus attention on new or complex tasks.
serotonin: A neurotransmitter that affects mood, appetite, and sleep.
signal detection theory: a theory predicting how and when we detect the presence of a faint stimulus amid background noise.
Sigmund Freud: Austrian neurologist known as the founder of psychoanalysis, a clinical method for treating psychopathology through dialogue between a patient and a psychoanalyst.
sleep: a natural state of rest for the body and mind, characterized by altered consciousness, reduced sensory activity, and inactivity of nearly all voluntary muscles.
sleep apnea: a sleep disorder characterized by pauses in breathing or shallow breaths during sleep, leading to disrupted sleep and daytime fatigue.
somatic nervous system: the division of the peripheral nervous system that controls the body's skeletal muscles and transmits sensory information to the central nervous system.
somatosensory cortex: a brain region located in the parietal lobe that processes sensory information from the skin and internal body receptors for touch, temperature, and body position.
somnambulism: A disorder in which a person walks or performs other complex behaviors while asleep.
sound localization: The process by which the position of a sound source is determined.
spinal Cord: The part of the central nervous system that transmits signals between the brain and the rest of the body.
split brain procedure: a surgical procedure that involves severing the corpus callosum, the bundle of nerve fibers connecting the brain's hemispheres, typically done to treat severe epilepsy.
stimulants: drugs that excite neural activity and speed up body functions, such as caffeine, nicotine, amphetamines, and cocaine.
subliminal: below one's absolute threshold for conscious awareness.
substance P: A neurotransmitter involved in the transmission of pain signals.
substance use disorder: a condition characterized by continued use of a substance despite significant substance-related problems.
supertasters: Individuals with heightened sensitivity to all tastes and mouth sensations.
suprachiasmatic nucleus: a tiny region of the hypothalamus that acts as the body's internal clock, regulating circadian rhythms such as the sleep-wake cycle.
sympathetic nervous system: the division of the autonomic nervous system that mobilizes the body's resources during stress and emergencies, preparing the body for "fight or flight" responses.
synapse: the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron, where neurotransmitters are released.
synesthesia: A condition in which one sense is simultaneously perceived as if by one or more additional senses.
temporal lobes: the regions of the cerebral cortex located above the ears, responsible for processing auditory information and containing areas involved in memory, language comprehension, and emotion.
thalamus: the brain's sensory control center, located on top of the brainstem, relaying sensory information (except for smell) to the appropriate areas of the cerebral cortex.
threshold: the level of stimulation required to trigger a neural impulse.
tolerance: the diminishing effect of a drug with regular use, requiring larger doses to achieve the same effect.
top-down processing: information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.
Torsten Wiesel: Swedish neurophysiologist known for his collaborative work with David Hubel, elucidating the visual processing system and its role in perception.
transduction: the process of converting one form of energy into another, such as sensory stimuli into neural impulses.
umami: One of the five basic tastes, often described as savory or meaty.
vestibular sense: the sense of body movement and position, including the sense of balance.
visual accommodation: The process by which the eye's lens changes shape to focus on objects at different distances.
visual cortex: The part of the brain that processes visual information.
volley principle: A theory of hearing which states that groups of neurons respond to sound by firing action potentials slightly out of phase with one another.
wavelength: the distance from the peak of one wave to the peak of the next wave, determining the wave's color (in vision) or pitch (in audition).
Weber's Law: the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage rather than a constant amount.
Wernicke's Area: A region in the temporal lobe of the brain associated with language comprehension.
withdrawal: the discomfort and distress that follow discontinuing the use of an addictive drug or behavior.
Young-Helmholtz (Trichromatic) Theory: the theory that the retina contains three different types of color receptors (cones)—red, green, and blue—that can produce any color by combining the three.