Much of the recent work in the neurobiology of emotion has divided emotion into two categories of positive and negative emotion. Positive emotions involving high levels of arousal often occur in the context of the anticipation of reward, while negative emotions involving high levels of arousal often occur in the context of the anticipation of punishment. Thus, we have sought to characterize neural activity associated with the anticipation of rewards and punishments. Comparative studies have implicated a ventral forebrain dopaminergic path in the anticipation of reward.
We aim ed primarily to replicate our work from FY 1999, which verified activation of these areas during monetarily rewarded approach and avoidance behavior in humans. In addition, we examined whether these ventral forebrain areas were activated prior to motor behavior, specifically, during anticipation of reward and punishment, as opposed to during responses for reward and punishment. Twelve healthy right-handed females (age 20-40) participated in 10-minute approach and active avoidance tasks in counterbalanced order. During the approach task, subjects saw a cue indicating that they could either win money or not, waited a variable delay, and then pressed a button in response presentation of a target. If subjects responded before the target following the reward cue disappeared, they won $1.00, whereas their response to the neutral target did not affect their total. During the active avoidance task, subjects were given $20.00 and responded to targets that followed either a punishment cue or a neutral cue. If they failed to respond before the disappearance of the target following the punishment cue, they lost $1.00, whereas their response to the neutral target again did not affect their total. 200 T2*-weighted gradient echoplanar MR volumes depicting BOLD-contrast were acquired using a 1.5 Tesla GE Signa System. The volume consisted of 10 slices spanning the corpus callosum (voxel size; 3.8 X 3.8 X 7.0 mm, TR: 3000 ms). After correcting for in-plane motion, individual voxel activations were correlated with an ideal waveform corresponding to the expected activation time course using AFNI. The ideal waveform consisted of the task On-Off waveform convoluted with the hemodynamic response function. Significant voxels (r > .30, p < .0001) were highlighted on the functional images. Similar to results found in our previous male sample, group analysis indicated that anticipation of reward activated striatal areas (caudate, putamen) and mesial forebrain areas (anterior cingulate, mesial prefrontal cortex, and thalamic regions). Anticipation of punishment also activated these regions relative to anticipation of no monetary outcome. However, anticipation of reward but not punishment produced activation in the left nucleus accumbens and regions of the medial forebrain bundle near the ventral tegmental area. These results extend our previous findings with men and suggest that projections from the ventral tegmental area including the nucleus accumbens may play a selective role in the anticipation of reward.
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