Why does a caress from a trusted partner feel so good? Our attempt to answer this question rests on the premise that touch stimuli received by the somatosensory cortex acquire affective (emotional) salience when they reach the amygdala.
To test this hypothesis, monkeys received innocuous air puffs and gentle grooming-like touch while we monitored their heart rate and neural activity in the somatosensory cortex and the amygdala. When monkeys are groomed by a trusted partner, they stop paying attention to the outside stimuli.
This may explain our finding that grooming stimuli, unlike the air puffs, fail to activate the touch-responsive neurons in the amygdala. It appears that the predictability of stimuli and the recipient's autonomic state contribute to 'gating' neural responses to affective touch in the amygdala.
This project rests on the premise that in hierarchical societies the rank, or social status, of an individual is a unique identifier, akin to physical appearance, sex, or age.
The first objective of this project is to demonstrate that monkeys can learn the status of previously unfamiliar individuals by watching videos of pairwise interactions among the members of a virtual hierarchy. The next step is to determine whether the subject monkey can be included in this virtual social hierarchy. Once the status of others and of the self is learned, we can change the interactions to induce a rise or fall in the status of select individuals.
We expect that the amygdala and the medial prefrontal cortex will respond to experimental manipulation of social status, whether it pertains to the self or to others.
Our brains are constantly receiving information from our bodies, called interoceptive signals, including blood pressure, breath rate, and heart rate. Our lab is interested in understanding how interoceptive signals influence the way we make decisions and process information. To do this, we take advantage of drugs that change body physiology (for example increasing heart rate) without changing brain physiology.
Our animals perform an approach-avoidance conflict task (a type of task where animals weigh the experience of paired positive and negative stimuli and decide to approach or avoid the paired stimuli) while under the influence (or lack thereof) the aforementioned drugs. Thus far, we have observed that animals are less willing to tolerate negative stimuli when a drug shifts the body into a sympathetic-dominated state (i.e., increased heart rate).
Future work will include evaluating the neural mechanisms by which interoceptive signals bias decision making, evaluating the effects of changes in interoceptive signals on social behavior, and determining if interoceptive signals influence neural representations of context (as seen in the tactile project).
Primate adolescence is a period of drastic changes in body, brain, and behavior. How do these three aspects of adolescence play together to support the transition to adult-like self-sufficiency and social maturation? To answer this question, we will examine the functional connectivity between the amygdala and prefrontal cortex, an area associated with social cognition that continues developing through adolescence.
We are monitoring macaques from pre-adolescence to adulthood through MRI, hormonal measures, behavioral performance, and electrophysiological recordings. We will compare physiological measures, reward valuation, and prosocial behavior at different stages of development.
As the animals approach adulthood we expect the emergence of cognitive control that resets the directional connectivity between the amygdala and the prefrontal cortex.