Feeling by numbers
The amygdala is recognized as a part of the brain associated with emotions such as fear and pleasure, and also with reinforcement learning, by which sensory stimuli become associated with positive or negative values. The way that neural circuits assign emotional value to visual stimuli is perhaps the most elusive aspect of this system experimentally. […]
The amygdala is recognized as a part of the brain associated with emotions such as fear and pleasure, and also with reinforcement learning, by which sensory stimuli become associated with positive or negative values. The way that neural circuits assign emotional value to visual stimuli is perhaps the most elusive aspect of this system experimentally. Now a quantitative analysis of primate amygdala neural activity during learning has identified different amygdala neuronal populations that encode the positive or negative value of visual stimuli. What is more, these signals predict when emotional learning will occur. Thus amygdala neural signals can form the basis of behavioural and physiological responses to visual stimuli endowed with emotional meaning.
The primate amygdala represents the positive and negative value of visual stimuli during learning.
by Paton JJ, Belova MA, Morrison SE, Salzman CD in Nature. 2006 Feb 16; 439(7078): 865-70
Visual stimuli can acquire positive or negative value through their association with rewards and punishments, a process called reinforcement learning. Although we now know a great deal about how the brain analyses visual information, we know little about how visual representations become linked with values. To study this process, we turned to the amygdala, a brain structure implicated in reinforcement learning. We recorded the activity of individual amygdala neurons in monkeys while abstract images acquired either positive or negative value through conditioning. After monkeys had learned the initial associations, we reversed image value assignments. We examined neural responses in relation to these reversals in order to estimate the relative contribution to neural activity of the sensory properties of images and their conditioned values. Here we show that changes in the values of images modulate neural activity, and that this modulation occurs rapidly enough to account for, and correlates with, monkeys’ learning. Furthermore, distinct populations of neurons encode the positive and negative values of visual stimuli. Behavioural and physiological responses to visual stimuli may therefore be based in part on the plastic representation of value provided by the amygdala.
