Amygdala's "unfelt" emotions?

Abstract

Participants saw “hybrid” pictures of faces composed by superimposing neutral expression in high spatial frequencies (HSF, 7-128 cycles/image) over different emotional expressions in low spatial frequencies (LSF, 1-6 cycles). While explicitly judging them as neutral, participants rated the hybrids as friendly when the emotion showed in the low frequencies was positive, and as unfriendly when the emotion shown in the low frequencies was negative. A young female patient (S.S.), whose left anterior temporal lobe had been surgically removed to treat a brain tumor, showed a change in unconscious preferences in the above test when the hybrids’ low frequency emotion was either sadness or fear, while she failed to explicitly label both fear and anger. Given (1) the amygdala’s sensitivity only to lowest spatial frequencies, and its “blindness” to the highest frequency, and (2) fusiform’s sensitivity to the highest frequencies and not to the lowest ones, as indicated by previous neuroimaging studies (Vuilleumier, Armony, Driver, & Dolan, 2003; Winston, Vuilleumier, & Dolan, 2003), the present study confirms the amygdala’s fundamental role in the response to fear, while suggesting its role in the unconscious response to other ‘negative’ emotions like anger and sadness.