Neural dynamics underlying impaired autonomic and conditioned responses following amygdala and orbitofrontal lesions.

Abstract

A neural model is presented that explains how outcome-specific learning modulates affect, decision-making and Pavlovian conditioned approach responses. The model addresses how brain regions responsible for affective learning and habit learning interact, and answers a central question: What are the relative contributions of the amygdala and orbitofrontal cortex to emotion and behavior? In the model, the amygdala calculates outcome value while the orbitofrontal cortex influences attention and conditioned responding by assigning value information to stimuli. Model simulations replicate autonomic, electrophysiological, and behavioral data associated with three tasks commonly used to assay these phenomena: Food consumption, Pavlovian conditioning, and visual discrimination. Interactions of the basal ganglia and amygdala with sensory and orbitofrontal cortices enable the model to replicate the complex pattern of spared and impaired behavioral and emotional capacities seen following lesions of the amygdala and orbitofrontal cortex.

Dopaminergic and non-dopaminergic value systems in conditioning and outcome-specific revaluation

“…It does so by showing how the MOTIVATOR model simulates observed changes in blood pressure, saccadic reaction times, learning, extinction, reversal, choice behaviors, and electrophysiological responses of identified cell types in multiple brain regions that are devoted to cognitiveemotional processes. The consequences of lesions to model AMYG and ORB components are detailed in a companion article (Dranias, Grossberg & Bullock, 2007).…”

“…ITA inputs play a critical role in driving saccadic behavior when ORB inputs are silent or after ORB has been lesioned. Such behaviors are simulated in Grossberg et al (2007). A.7 Initialization of Variables.…”

Autism as a neural systems disorder: A theory of frontal-posterior underconnectivity

“…The resulting exemplars are “hyperspecific”. To take another example, CogEM learns associations between the objects in the world and the internal emotional states that give those objects value (Dranias et al, 2008; Grossberg et al, 2008). According to iSTART, parametric imbalance in autism causes the threshold for emotional response by the amygdala to be abnormally high, resulting in underarousal depression.…”

A Local Circuit Model of Learned Striatal and Dopamine Cell Responses under Probabilistic Schedules of Reward

“…It does not treat LH cells that show learned responses to CS onsets. However, the network embedding and role of such cells were treated recently in a complementary model (Grossberg et al, 2008) of LH-amygdala-orbitofrontal interactions that mediate such processes as simultaneous visual discrimination, motivational/attentive enhancement of stimulus representations, and rapid selective devaluations of stimuli after satiety.…”