• Neurolinguistics is the study of the relationship between language and the brain.

• The field dates back to the nineteenth century, with the challenge of establishing the location of language in the brain.

• An incident involving a construction foreman named Phineas P. Gage in 1848 provided a clue.

• Gage survived a severe brain injury caused by an iron rod that went through the front part of his brain, with no apparent damage to his senses or speech.

• This incident suggested that while language may be located in the brain, it is not situated right at the front.

• Discoveries have been made about the specific parts in the brain related to language functions, primarily located around the left ear.

• The left hemisphere of the brain is primarily involved in language functions.

• The shaded areas in Figure 12.1 indicate the general locations of language functions involved in speaking and listening.

• Broca’s area (1 in Figure 12.1), discovered by Paul Broca, is crucially involved in the generation of spoken language.

• Wernicke’s area (2 in Figure 12.1), discovered by Carl Wernicke, is crucially involved in the understanding of spoken language.

• The motor cortex (3 in Figure 12.1) controls the articulatory muscles of the face, jaw, tongue, and larynx, hence the physical articulation of speech.

• The arcuate fasciculus (4 in Figure 12.1), also discovered by Wernicke, forms a crucial connection between Wernicke’s and Broca’s areas.

• The localization view suggests that specific aspects of language ability can be accorded specific locations in the brain.

• The process of hearing a word, understanding it, and then saying it, is believed to follow a definite pattern involving Wernicke’s area, the arcuate fasciculus, Broca’s area, and the motor cortex.

• This view is an oversimplified version of what may actually take place, but it is consistent with much of what we understand about simple language processing in the brain.

• Any proposal concerning processing pathways in the brain is considered a form of metaphor that may turn out to be inadequate once we learn more about how the brain functions.

• We use metaphors because we cannot obtain direct physical evidence of linguistic processes in the brain and have to rely on indirect methods.

• Most of these methods involve attempts to work out how the system is working from clues picked up when the system has problems or malfunctions.

• Speech production difficulties may provide clues to how our linguistic knowledge is organized within the brain.

• The “tip of the tongue” phenomenon occurs when we know a word but can’t recall it. This suggests that our word-storage system may be partially organized based on phonological information.

• Mistakes in word retrieval, often with strong phonological similarities to the target word, are referred to as malapropisms.

• Another type of speech error, known as a slip of the tongue or spoonerism, involves expressions like “a long shory stort” (instead of “make a long story short”).

• Other examples are word substitutions, where a similar but inappropriate word is used instead of the target.

• There are three general types of everyday slips: perseveration (one sound is carried over to the next word), anticipation (a sound is used before its occurrence in the next word), and exchange (sounds change places).

• These slips are mostly treated as errors of articulation, but they may actually result from slips of the brain as it tries to organize and generate linguistic messages.

• “Slips of the ear” are another type of slip that may provide clues to how the brain tries to make sense of the auditory signal it receives.

• These slips can result in misheard words or phrases, such as hearing “great ape” instead of “gray tape”, or “My uncle has a pimple” instead of “My uncle has a pit bull”.

• Some malapropisms may originate as slips of the ear.

• These humorous examples of slips may give us a clue to the normal workings of the human brain as it copes with language.

• However, some problems with language production and comprehension are the result of much more serious disorders in brain function.

• Aphasia is an impairment of language function due to localized brain damage, leading to difficulty in understanding and/or producing linguistic forms.

• The most common cause of aphasia is a stroke, though traumatic head injuries can also cause similar effects.

• Aphasia can lead to interrelated language disorders, with difficulties in understanding leading to difficulties in production.

• Broca’s aphasia, also known as motor aphasia, is characterized by reduced speech, distorted articulation, and slow, often effortful speech. It often results in agrammatic speech, where grammatical markers are missing.

• Wernicke’s aphasia, sometimes called sensory aphasia, results in difficulties in auditory comprehension. Individuals with this disorder can produce fluent speech that is often difficult to understand and may have difficulty finding the correct word (anomia).

• Conduction aphasia is a less common type of aphasia associated with damage to the arcuate fasciculus.

• Individuals with this disorder sometimes mispronounce words, but typically do not have articulation problems. They are fluent, but may have disrupted rhythm due to pauses and hesitations.

• Comprehension of spoken words is normally good, but repeating a word or phrase creates major difficulty.

• Many of these symptoms, such as word-finding difficulty, can occur in all types of aphasia and can also occur in more general disorders such as dementia and Alzheimer’s disease.

• Difficulties in speaking can be accompanied by difficulties in writing, and impairment of auditory comprehension tends to be accompanied by reading difficulties.

• These language disorders are almost always the result of injury to the left hemisphere, which is dominant for language.

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• The dichotic listening test is an experimental technique that demonstrates a left hemisphere dominance for syllable and word processing.

• The test is based on the fact that anything experienced on the right-hand side of the body is processed in the left hemisphere, and vice versa.

• In the test, a subject is given two different sound signals simultaneously, one through each earphone. The subject more often correctly identifies the sound that came via the right ear.

• This process shows that the language signal received through the left ear is first sent to the right hemisphere and then to the left hemisphere for processing. This non-direct route takes longer than a linguistic signal received through the right ear, which goes directly to the left hemisphere.

• The right hemisphere appears to have primary responsibility for processing non-linguistic signals. In the dichotic listening test, non-verbal sounds are recognized more often via the left ear, meaning they are processed faster via the right hemisphere.

• These specializations may have more to do with the type of processing rather than the type of material that is handled best by each of the two hemispheres. The essential distinction seems to be between analytic processing, done with the “left brain,” and holistic processing, done with the “right brain.”

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• The left hemisphere of the brain is usually specialized for language, a process known as lateralization.

• The lateralization process begins in early childhood, during the “critical period” for language acquisition, which lasts from birth until puberty.

• If a child does not acquire language during this period, it becomes almost impossible to learn language later on.

• The case of “Genie,” a girl who was deprived of linguistic input during her critical period, provides insight into this phenomenon.

• Genie was able to develop some speaking ability and understand a number of English words, suggesting that language can be acquired to some extent after the critical period.

• However, her diminished capacity to develop grammatically complex speech supports the idea that the left hemisphere of the brain is open to accepting a language program during childhood, and if no program is provided, the facility is closed down.

• Tests indicated that Genie was using the right hemisphere of her brain for language functions, suggesting that our capacity for language is not limited to only one or two specific areas, but is based on more complex connections extending throughout the whole brain.

• When Genie began to use speech, she went through some of the same early stages found in normal child language acquisition.