Functional neuroanatomy of pleasant and unpleasant emotion

Abstract

To investigate the basic neural circuitry underlying emotion, three brain imaging studies were performed using positron emission tomography and 15O-water. In each study subjects viewed pictures from the International Affective Picture System (IAPS). Study #1 examined the neural correlates of pleasant and unpleasant emotion in 12 healthy women. Compared to viewing neutral stimuli, viewing pleasant and unpleasant pictures were each associated with activation of thalamus, hypothalamus, midbrain and medial prefrontal cortex. Viewing pleasant pictures was also associated with activation of the head of the caudate nucleus and viewing unpleasant pictures was associated with activation of left medial temporal structures (amygdala, hippocampus and parahippocampal gyrus), bilateral extrastriate visual cortex, bilateral temporal poles and cerebellum. Study #2 examined the neural substrates of emotional valence, arousal and attention. Six healthy men were studied in twelve scan conditions generated from a 3 x 2 x 2 factorial design: 3 levels of valence (pleasant, unpleasant and neutral), 2 levels of arousal (high and low) and 2 levels of attention (easy and difficult distraction tasks). Subtraction of the low arousal pleasant and unpleasant conditions from the high arousal pleasant and unpleasant conditions revealed activation in the dorso-medial region of the thalamus and the medial prefrontal cortex. Activation of the medial prefrontal cortex was greater during the low distraction compared to the high distraction conditions. These results suggest that the thalamus and medial prefrontal cortex are activated as a function of the intensity of emotional arousal independent of valence. Study #3 examined the neural substrates of the experiential component of emotion using a selective attention paradigm. Ten healthy men viewed IAPS pictures as they attended either to their subjective emotional responses or the spatial location of the depicted scene. During attention to subjective emotional responses increased neural activity was elicited in rostral anterior cingulate cortex (BA32) and medial prefrontal cortex, right temporal pole, insula and ventral cingulate. Under the same stimulus conditions when subjects attended to spatial aspects of the pictures activation was observed in parieto-occipital cortex bilaterally. The findings indicate that the rostral anterior cingulate cortex participates in representing subjective emotional responses.