Neurons in the OFC encode the sensory properties, magnitude and subjective value of expected and received outcomes, typically foods and fluids. For this reason, OFC has been studied for it role in learning and reward-based choice. The estimated values of choices, and therefore decision making based on those values, is influenced by both the chance that the chosen items or goods can be obtained (availability) and their current worth (desirability). OFC is thought to be essential for both these aspects of stimulus-reward learning. Yet the ventrolateral prefrontal cortex (VLPFC), a region adjacent to OFC, has also been implicated in learning about the availability of outcomes. To explore the functional specializations of these two frontal cortex regions, we trained animals on two tasks: one required updating representations of a predicted outcomes desirability, as measured by the devaluation task; the other required updating representations of an outcomes availability, as indexed by performance on a probabilistic 3-choice visual discrimination. We evaluated performance on both tasks in three groups of animals: unoperated controls and those with selective, fiber-sparing lesions of either OFC or VLPFC. We found that VLPFC but not OFC plays an essential role in making choices based on outcome availability; in contrast, OFC but not VLPFC is essential for making choices based on outcome desirability. Additional analyses indicated that VLPFC is essential for the ability to link particular outcomes with particular choices, a process sometimes called credit assignment. The separate processing of outcome availability and desirability in VLPFC and OFC, respectively, has implications for models of prefrontal cortex function during choice behavior. As indicated above, neurons in the OFC encode the sensory properties, magnitude and subjective value of expected and received rewarding outcomes. Subjective value is reflected not only in neural activity, but also in autonomic responses. Indeed, both neural activity and pupil diameter, a measure of sympathetic autonomic arousal, are correlated with the magnitude of expected reward. However, previous research has not identified whether the value coding in OFC is linked with autonomic arousal. To answer this question, we compared animals with bilateral excitotoxic lesions of OFC and unoperated controls on a reward magnitude task in which five visually presented images were assigned to five different fluid reward amounts (0, 0.2, 0.4, 0.8 and 1.6 ml). Animals were required to maintain fixation at the center of a monitor screen for the duration of each trial, which consisted of image presentation (cue period), an unfilled interval with no cue (delay period), and reward delivery. Animals received the amount of reward assigned to the single image displayed on that trial. Pupil size served as our measure of autonomic arousal. We found that the two groups did not differ in their rate of acquisition of significant autonomic responses during the cue period. In addition, both groups exhibited a pupil size that was positively related to reward magnitude. Compared to the controls, however, animals with OFC lesions showed a late onset of differentiated pupillary responses during the cue period and a significant impairment in sustaining arousal during the delay period. At the same time, autonomic responses to unsignaled reward and to changes in luminance were intact, demonstrating that OFC lesions did not affect the basic physiology of the pupil. Our findings show that OFC is necessary for acquiring the normal pattern of autonomic arousal in anticipation of different reward magnitudes. In particular, the data suggest that subjective value representations in OFC sustain autonomic arousal for biologically significant events. For decades, it has been known that lesions of OFC and surrounding white matter produce blunted affective responses to threatening stimuli. Recent evidence involving restricted (excitotoxic, fiber-sparing) damage to OFC has shown contradictory effects of either no involvement of OFC or heightened affective responses, but these studies differ with respect to the species studied and the extent of OFC damage. To address these discrepancies and further examine the putative role of OFC in emotional regulation, we studied animals with restricted bilateral excitotoxic lesions targeting either lateral OFC or medial OFC. The performances of these groups and a group with total bilateral lesions of OFC were compared to that of a group of unoperated controls on defensive responses to the presentation of a rubber snake, rubber spider, and neutral objects for comparison. Both subtotal lesion groups showed heightened defensive responses as indexed by latency to retrieve a food reward in the presence of the spider and snake. Surprisingly, the group with medial OFC lesions showed greater food-retrieval latencies even in the presence of neutral objects, compared to unoperated controls. Our data indicate that medial and lateral OFC make dissociable contributions to emotional regulation. In addition, the findings strongly suggest that any emotional blunting associated with OFC damage is due to a disruption of fibers of passage (that is, fibers passing nearby OFC), as opposed to damage to cell bodies residing in OFC. A considerable body of evidence suggests a role for the amygdala in processing emotionally salient information in faces. For example, patients with amygdala damage fix their gaze on the eye region of faces to a lesser extent than controls. In our earlier work we used an attentional capture task to assess the role of the amygdala in attending to different aspects of facial expressions of emotion. In that study, and in most studies of face viewing, eye movements are monitored while face images are presented singly in the center of a monitor screen. If the amygdala plays a role in the prioritization of faces in natural viewing behavior, however, then the amygdala might be essential for guiding eye movements toward face images when they are competing with other images for attention. To test this possibility, we assessed the effects of bilateral amygdala damage on viewing preferences for faces, illusory faces, and non-face objects when two images were presented simultaneously, side by side. We collected two dependent measures: how long a subject looked at each of the images in a given pair and where they fixated within each image. Unlike intact animals, who showed robust preferences for both real and illusory faces, animals with amygdala damage showed no preference for either real or illusory faces over non-face objects. Further, whereas intact animals showed classic face viewing patterns prioritizing discrete facial features, such as the eyes and mouth, animals with amygdala damage showed disorganized viewing patterns better described by models of perceptual salience. These results identify the amygdala as critical for our earliest specialized response to faces, a behavior thought to be a precursor for efficient social communication.
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