Cognitive Neuroscience Social Cognition

The case of Phineas Gage

The role of the brain in social cognition was first documented by John Harlow, a physician who attended Phineas Gage, a railroad construction supervisor who was injured by a tamping rod.

The rod entered the head through his lower left jaw, traveled through the eye socket, and damaged parts of orbitofrontal and ventromedial prefrontal cortex before exiting through the top of the skull.

Gage recovered from the accident, but underwent pronounced changes in his behavior and personality.

He had previously been friendly and reliable. After the accident, he became irritable, profane, short-tempered, and inconsiderate of others. He also was incapable of making plans. He was not able to keep his job as supervisor and became a wandering drifter. For a time, he was a side-show attraction with a traveling carnival.

1 Gage’s skull and the rod are on display at a medical museum at Harvard University.

Adaptation to the social environment

Since the time of Harlow, evidence as accumulated that the brain plays essential roles supporting social interactions.

Adaptation to the social environment is critical for humans. From the time of birth, humans require social interaction for survival. fMRI studies show that cooperation among humans activates the same neural systems as do appetitive stimuli and symbolic rewards. Thus, cooperative activity in a social group can have significant reward value.

In order to function in a social environment, many demands are placed on the brain’s information processing systems. Functions are required that promote self-interest, self-enhancement, and self-protection. Like the study of language, the study of these functions depends on modern methods for investigating brain function in humans: fMRI, ERP, as well as facial electromyography.

Is social information processed by specialized neural circuitry?

Specific regions of the brain are involved in processing social information.

(1) The cortex around the superior temporal sulcus has been proposed to be involved in processing behavior of conspecifics (i.e. individuals of the same species).

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(2) The amygdala and orbitofrontal cortex have been proposed to be involved in determining the socio-emotional relevance of social information.

(3) The fusiform gyrus has been implicated in processing of faces.

(4) Ventromedial cortex, along with orbitofrontal cortex and amygdala, insular and somatosensory cortex, are involved in social perception, cognition, and decision-making.

Although all of these areas are involved in processing social information, none is specifically dedicated to that processing.

Reward system

A reward is an appetitive stimulus given to a human or animal to alter its behavior. Rewards typically serve to reinforce certain behaviors, i.e., to increase the likelihood that the behavior will occur.

The reward system is a group of brain structures that are critically involved in mediating the effects of reinforcement.

The brain structures in the reward system are mostly contained in the cortical-basal ganglia-thalamic loop.

The subcortical structures of the reward system include the amygdala, ventral tegmental area (VTA), substantia nigra, ventral striatum (mostly nucleus accumbens), dorsal striatum (caudate & putamen), globus pallidus, hippocampus, and parts of thalamus & hypothalamus. The cortical areas include orbitofrontal and ventromedial parts of prefrontal cortex, anterior cingulate cortex, and insular cortex. The mesolimbic dopamine pathway is a critical part of this system that connects VTA and nucleus accumbens.

Electrical stimulation of reward system regions in the rat can substitute for external appetitive stimuli, e.g., food. In humans, electrical stimulation of these areas produces pleasurable sensations.

3 Together with the amygdala, the orbitofrontal cortex is associated with abstract reward representation. As part of this role, orbitofrontal cortex may determine the socio-emotional relevance of social information. This means that it may determine the social propriety of action schema, i.e. whether a particular action schema is socially appropriate or not.

Is the amygdala critical for social cognition?

Kluver & Bucy first demonstrated emotional and social effects in monkeys of bilateral surgical lesions to the anterior temporal lobes, which included the amygdalae. The Kluver-Bucy syndrome is also seen in humans.

The Kluver-Bucy syndrome consists of: 1. affective blunting (flat affect, inappropriate response to stimuli) 2. hypersexuality & atypical sexual behavior, e.g. mounting inanimate objects & members of same sex 3. oral compulsion (often resulting in hyperphagia) 4. visual agnosia (inability to visually recognize objects); also called “psychic blindness”

Monkeys with surgically modified temporal lobes have great difficulty in knowing what prey is, what a mate is, what food is and in general what the significance of any object might be.

The view of amygdaloid function that seems to be required from consideration of the Kluver-Bucy syndrome is that the amygdala is essential for effective social interactions. When it is damaged, the normal perception and production of expressive behaviors is impaired.

An alternative view comes from the studies of Amaral on the social behavior of monkeys in which the amygdalae were chemically lesioned.

The main result was that the monkeys had reduced social inhibitions. They appeared to engage in social interactions without the normal period of evaluation, resulting in more initiation of interactions.

The conclusion was that lesioning the amygdalae impairs normal evaluative behavior in which the social context is considered. Without the amygdalae, the animal’s ability to properly assess social behavior is impaired.

4 Redundant systems for evaluative processing

Evaluative processes are responsible for an organism’s ability to differentiate hostile from hospitable stimuli.

Remember John Hughlings Jackson, the 19th century neurologist.

He stressed the re-representation of functions at multiple levels of the nervous system. This means that evaluative processing is organized in multiple redundant systems.

At the lowest level are primitive reflex behaviors organized in the spinal cord and brainstem. These behaviors ensure that the organism approaches or avoids certain classes of stimuli, and provide metabolic support for such actions.

These reflex behaviors are “hard-wired” fixed-action patterns. Examples seen in the human infant: (1) startle response to sudden intense noise (2) withdrawal reflex for retreat from nociceptive stimuli, e.g. pungent odors

The evaluative discrimination of stimuli can be shaped in humans by cultural learning. For example, people in some cultures learn to like chaw tofu.

The primitive protective reactions are expanded and elaborated at higher levels of the nervous system.

At progressively more rostral levels of organization (spinal, brainstem, limbic, neocortical), the range and relational complexity of contextual controls expands, as does the flexibility of discriminative and adaptive responses.

5 Development of higher structures (e.g. limbic structures like the amygdala and hippocampus, and the cerebral cortex in general) provide the organism with an expanded behavioral repertoire, including: (1) escape reactions (2) aggressive responses (3) the ability to anticipate and avoid aversive encounters

This greater flexibility requires more neural resources. With greater adaptive ability, there is a less rigid relation between stimuli and responses, with potentially more intervening processing steps.

The layering of systems is efficient in that it allows utilization of the lower, more rigid systems when they are sufficient (in simple situations), and only invokes the higher, more flexible systems as needed (in more complex situations) to override the lower systems.

Sometimes, these systems may be in conflict. In the study by Boysen et al (1996), chimps viewed two pans containing candy rewards. They were rewarded with the contents of the pan to which they did not point.

Since the chimps liked the candy rewards, it was in their best interest to select the smaller of the two candy arrays. However, despite extensive training, their performance continued to be significantly below chance, i.e., they picked the larger one.

The authors hypothesized that the perceptual features of the candy arrays interfered with the chimps’ ability to perform optimally based on the rule structure of the task.

They tested the hypothesis by having the chimps perform the same task with the candy arrays replaced by placards having the corresponding Arabic numerals (which they could interpret). The result was an immediate change to above-chance performance.

The chimps apparently could acquire the rules of the task, but their actions based on the rules were blocked by the “potent competing disposition” that came from the “intrinsic incentive properties” of the candy arrays.

6 In humans, the capacity to work with symbolic representations of the world may have evolved because of its survival value for minimizing powerful but “maladaptive dictates of lower evaluative dispositions”.

The rapid, perception-driven responses of the chimps to the candy stimuli were probably organized by subcortical limbic structures, e.g. amygdala, nucleus accumbens, etc.

The chimps’ responses to the symbols, involving a reverse contingency between stimulus and reward, probably required intervention by the prefrontal cortex. The ventromedial and lateral orbitofrontal prefrontal cortices have been associated with the abstract representation of reward.

Projections of the basal forebrain cholinergic system to the neocortex plays an important role in setting the “functional tone” of cortical processing. It may serve to activate the medial prefrontal cortex to cause that area to intervene in mediating emotional responses to contextual stimuli (and override lower processes).

When this system is suppressed by pharmacological agents such as anxiolytic benzodiazepine agonists (e.g. Librium), the intervention by higher levels is thwarted and there is a relative downward shift in processing levels.

The rapid operation of lower evaluative processes may affect higher, but slower processes in the cerebral cortex. By priming cortical networks, inputs from lower evaluative systems could emotionally predispose the perceptual processing of stimuli in the cortex.

This may help explain why socially relevant postures (arms pulling towards vs arms pushing away) affect the emotional interpretation of initially neutral stimuli (Chinese ideographs) (Cacioppo et al 1993).

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