For the most part, I'm disappointed with these references. Their discussion of neuroanatomy, neurotransmitters, and neuromodulators was very vague and general. They were all from the same institution: the Department of Neurobiology, Duke University School of Medicine
Neuroethology: PubMed found 343 references - sorted by publication date
Neuroethology of reward and decision making - Abstract
"Ethology, the evolutionary science of behaviour, assumes that natural selection shapes behaviour and its neural substrates in humans and other animals. In this view, the nervous system of any animal comprises a suite of morphological and behavioural adaptations for solving specific information processing problems posed by the physical or social environment. Since the allocation of behaviour often reflects economic optimization of evolutionary fitness subject to physical and cognitive constraints, neurobiological studies of reward, punishment, motivation and decision making will profit from an appreciation of the information processing problems confronted by animals in their natural physical and social environments."
Neuroethology of reward and decision making - full article
"Recent studies have revealed elementary properties of the neural systems that process rewards and punishments as traditionally defined. Specifically, the circuit connecting midbrain dopamine neurons to the ventral striatum and prefrontal cortex appears to be crucial for processing information about rewards (Schultz 2000; Schultz & Dickinson 2000)."
"Electrophysiological recordings from dopaminergic neurons show that these cells respond to unpredicted primary rewards, such as food and water, as well as to conditioned stimuli that predict such rewards (Schultz 2000; Schultz & Dickinson 2000; figure 2). Moreover, dopamine neuron responses scale with both reward magnitude and reward probability (Fiorillo et al. 2003; Tobler et al. 2005)."
1. I did not find this article useful. It's discussion of neuroanatomy neurotransmitters and neuromodulators was very vague and general. It was focused on mathematical models.
2. The two authors, Watson KK1and Platt ML. were two of the four authors of the following paper (PMID22902613 & PMC3510321).
Neuroethology of decision-making. - PubMed - Abstract
"A neuroethological approach to decision-making considers the effect of evolutionary pressures on neural circuits mediating choice. In this view, decision systems are expected to enhance fitness with respect to the local environment, and particularly efficient solutions to specific problems should be conserved, expanded, and repurposed to solve other problems. Here, we discuss basic prerequisites for a variety of decision systems from this viewpoint. We focus on two of the best-studied and most widely represented decision problems. First, we examine patch leaving, a prototype of environmentally based switching between action patterns. Second, we consider social information seeking, a process resembling foraging with search costs.
We argue that while the specific neural solutions to these problems sometimes differ across species, both the problems themselves and the algorithms instantiated by biological hardware are repeated widely throughout nature. The behavioral and mathematical study of ubiquitous decision processes like patch leaving and social information seeking thus provides a powerful new approach to uncovering the fundamental design structure of nervous systems."
Neuroethology of Decision-making - Full Length Article
"The behavioral and mathematical study of ubiquitous decision processes like patch leaving and social information seeking thus provides a powerful new approach to uncovering the fundamental design structure of nervous systems."
"When the fitness impact of a decision is large, strong selective pressures should produce mathematically optimal behavior. Such a constraint means that the neurobiological mechanisms mediating decisions may be highly conserved or convergent across taxa for problems with similar mathematical formulations (Figure 1)."
"The study of ecological decision-making suggests the that natural selection has favored a set of simple, repeated design patterns: basic circuit elements capable of being implemented by many biological configurations."
1. I didn't find this helpful. It's conclusions were highly speculative, and it discussed physiology in only the vaguest of terms.
2. As mentioned, above, two of the four authors of this paper (Adams GK1, Watson KK, Pearson J, Platt ML.) also authored the paper, above.
Neuroethology of primate social behavior - Abstract
"A neuroethological approach to human and nonhuman primate behavior and cognition predicts biological specializations for social life. Evidence reviewed here indicates that ancestral mechanisms are often duplicated, repurposed, and differentially regulated to support social behavior. Focusing on recent research from nonhuman primates, we describe how the primate brain might implement social functions by coopting and extending preexisting mechanisms that previously supported nonsocial functions. This approach reveals that highly specialized mechanisms have evolved to decipher the immediate social context, and parallel circuits have evolved to translate social perceptual signals and nonsocial perceptual signals into partially integrated social and nonsocial motivational signals, which together inform general-purpose mechanisms that command behavior. Differences in social behavior between species, as well as between individuals within a species, result in part from neuromodulatory regulation of these neural circuits, which itself appears to be under partial genetic control. Ultimately, intraspecific variation in social behavior has differential fitness consequences, providing fundamental building blocks of natural selection. Our review suggests that the neuroethological approach to primate behavior may provide unique insights into human psychopathology."
Neuroethology of primate social behavior - Full Length Article
"Many of our behaviors are driven by reinforcement, and we and other animals seek a variety of rewards by foraging. Foraging is one of the most primitive and basic behavioral states, being a feature of essentially all motile, heterotrophic life. It is therefore unsurprising that foraging strategies are under strong selective pressure for maximizing returns on investment. Animals often forage for foods sparsely distributed in locally dense patches (39). As an animal forages in a patch, resources are depleted and the rate of energy intake slows. However, traveling to a new patch may be costly and accompanied by uncertain outcomes"
"The optimal solution, known as Charnov’s Marginal Value Theorem, is that a patch should be abandoned when the current rate of consumption falls to the average for the overall environment (39)."
"We propose that, because a major function of the brain is to seek resources, it is likely that mechanisms that evolved to support foraging are readily repurposed to solve other, formally similar computational problems. With respect to social behavior, if information about others is a valuable resource, then the biological mechanisms underlying foraging decisions will be used to support social information seeking (56). For example, opportunities and costs associated with social information foraging are likely to engage fundamental biological mechanisms for computing opportunities and costs. Foraging mechanisms seem likely to have become further specialized to cope with the unique demands of interindividual dynamics that arise as a consequence of group living."
"Ultimately, neuropeptides like OT may impact even complex social behavior via a basic set of mechanisms. The anxiolytic effects (25, 26) of OT may have served as a preadaptation for the prolonged interaction necessary for high-intensity parental care in mammals by promoting approach behavior and enhancing tolerance (27–29). These basal functions could then serve as building blocks for more complex social behaviors. Suppressing vigilance and increasing tolerance to nonoffspring may permit extended interactions with others. Ultimately, complex emotions like trust may arise via reduced social apprehension and enhanced tolerance, under the regulatory influence of neuropeptides like OT (114)."
1. Four of the seven authors of this paper, Chang SW1, Brent LJ, Adams GK, Klein JT, Pearson JM, Watson KK, Platt ML. , were also authors of the preceding two papers, so it's not surprising that it shares the vagueness and superficiality of them.
2. This paper did, however, have an interesting discussion of genetic determinism. I've copied this to: Genetics .
Toward an organismal neurobiology: integrative neuroethology. - Abstract
"Overt behavior is generated in response to a palette of external and internal stimuli and internal drives. Rarely are these variables introduced in isolation. This creates challenges for the organism to sort inputs that frequently favor conflicting behaviors. Under these conditions, the nervous system relies on established and flexible hierarchies to produce appropriate behavioral changes. The pteropod mollusc Clione limacina is used as an example to illustrate a variety of behavioral interactions that alter a baseline behavioral activity: slow swimming. The alterations include acceleration within the slow swimming mode, acceleration from the slow to fast swimming modes, whole body withdrawal (and inhibition of swimming), food acquisition behavior (with a feeding motivational state), and a startle locomotory response. These examples highlight different types of interaction between the baseline behavior and the new behaviors that involve external stimuli and two types of internal drives: a modular arousal system and a motivational state. The investigation of hierarchical interactions between behavioral modules is a central theme of integrative neuroethology that focuses on an organismal level of understanding of the neural control of behavior. "
Toward an Organismal Neurobiology: Integrative Neuroethology - Full Length Article
The Abstract, above, gave me the impression that this just reported externally visible phenomena without considering underlying physiology. So I didn't look at the full article.
The neuroethology of friendship. - Abstract
"Friendship pervades the human social landscape. These bonds are so important that disrupting them leads to health problems, and difficulties forming or maintaining friendships attend neuropsychiatric disorders like autism and depression. Other animals also have friends, suggesting that friendship is not solely a human invention but is instead an evolved trait. A neuroethological approach applies behavioral, neurobiological, and molecular techniques to explain friendship with reference to its underlying mechanisms, development, evolutionary origins, and biological function. Recent studies implicate a shared suite of neural circuits and neuromodulatory pathways in the formation, maintenance, and manipulation of friendships across humans and other animals. Health consequences and reproductive advantages in mammals additionally suggest that friendship has adaptive benefits. We argue that understanding the neuroethology of friendship in humans and other animals brings us closer to knowing fully what it means to be human. "
The neuroethology of friendship - Full Length Article
"Biochemical regulation of friendship
The hormonal and peptidergic mechanisms that modulate affiliative interactions in mammals have received extensive attention, the results of which have been summarized in a number of comprehensive reviews.5,11,55,108,109 We aim not to cover this information in detail but instead to highlight the most current findings and recent debates regarding some of the major biochemical systems that regulate friendship, namely those involving oxytocin, endorphins, dopamine, serotonin, and the hypothalamic–pituitary–adrenal (HPA) axis.
Social behavior is largely reinforcement driven. Oxytocin (OT) is a neuropeptide that stimulates lactation in mammals and is involved in bonding between mothers and infants, as well as between pair-bonded reproductive partners.110,111 OT has also been associated with social relationships outside of pair and maternal bonds. For example, OT is involved in individual recognition and social memory.112,113 Exogenous application of OT increases prosocial decisions and attention to others,114 increases feelings of trust,115 and encourages generosity.116
In addition to OT, the opioid β-endorphin is also involved in reward processes and has been associated with social behavior, especially in primates.55,117 Some researchers have proposed that while OT facilitates social interaction, it is β-endorphin that is crucial to the formation and maintenance of social bonds.55,109,118 The idea that OT facilitates social interaction, but not bonding, stems from the fact that the effects of OT are relatively short-lived119,120 and that OT reduces social vigilance,78 which may be a prerequisite for social interaction.
Although not much is known about the relationship between endorphins and social interactions,118 the results of one new study support the association between endorphins and social bonds; individuals release more endorphins when rowing a boat in a social context—a prime example of behavioral synchrony, which is a key component of friendship51—compared to when rowing alone, despite exerting the same amount of physical effort in both cases.121
Regardless of the role of endorphins, new findings contradict the idea that OT merely facilitates interactions and is not also involved in bonding itself. In one study, urinary OT levels in wild male chimpanzees were elevated following social grooming.122 Crucially, increases in urinary OT were only observed in males that had groomed a chimpanzee with whom they already possessed a bond (bonded males were kin or unrelated). What mattered in terms of OT release, therefore, was not grooming in general, but grooming with a friend.122 This observation resonates with other recent findings that the positive effects of exogenously administered OT on trust-related feelings or behaviors only occur when subjects interact with people they know or with members of their in-group.123,124 Together, the results of these studies suggest that both OT and endorphins contribute to the formation and maintenance of social bonds.
Serotonin and dopamine are also ancient and potent neuromodulators. The contribution of dopamine to the formation of social memories and social preference as part of the ventral tegmental area–dopamine projection system has been well described.109,125 Much of the work on serotonin, on the other hand, has been at the phenotypic level, exploring the association between serotonin and social behaviors. For instance, administration of selective serotonin reuptake inhibitors (SSRIs) alters the rate of affiliative and aggressive interactions.126,127 Serotonin transporter binding in the midline cortex is associated with aggressive and friendly traits in rhesus macaques,128 and genetic polymorphisms in the serotonergic pathway are associated with social integration.28 The majority of research on the correlates of serotonin points to links between this neuromodulator and sensory inputs, including social stimuli.129 This has led to the proposition that serotonin modulates how individuals perceive and respond to social information.109,129 Nevertheless, the molecular processes underlying the association between serotonin and sociality are little understood and will require concerted future research efforts to disentangle.
The stress response, produced via activation of the HPA axis, warns animals that homeostasis has been disrupted and mobilizes energy to restore a homeostatic state.130 For animals for whom social relationships are crucial to success and survival,10,27 the stress response is part of the motivational system that underpins social interaction. Many animals, including humans, exhibit smaller increases in stress hormone (cortisol) levels during exposure to averse stimuli when a friend is present compared to when alone.131 In primates, social grooming reduces heart rate,132 and individuals with more tightly-knit social networks have lower baseline levels of cortisol metabolites in their feces.133,134 For animals with tightly-knit and predictable social networks, low baseline cortisol levels may be a result of these individuals being able to cope effectively with social challenges. The acute reduction of heart rate in response to social grooming can be interpreted as a response to the fulfillment of a social need (negative feedback between endorphins, OT, and the HPA axis is also likely to play a part).
Chronic activation of the stress response has well-known negative consequences for health135 and reproduction,136 both of which may negatively affect evolutionary fitness. This has led to the suggestion that stress reduction is a selective pressure in the evolution of social bonds and is, therefore, one of the ultimate functions of social bonding.7,9,14 However, it is important to remember that an association between the stress response and social behavior reflects the role of the stress response as a proximate mechanism underlying social interactions.133 To propose that stress reduction is the ultimate reason individuals make friends is akin to suggesting that thirst is the ultimate reason we drink. Clarifying the type of biological mechanism the stress response represents (proximate, not ultimate) will positively influence how research linking the HPA axis to social behavior is interpreted and, as such, will improve our understanding of the evolution of friendship."
This paper suffers from the same vagueness and lack of physiologic detail as the other papers, above. They seem to have all been produced by the Department of Neurobiology, Duke University School of Medicine, and Platt ML was listed as one of the authors of all of them.
Searching PubMed for "foraging" identified 8,576 references: