Hemisphere differences in the mood state-dependent effect for recognition of emotional faces.

Forty subjects viewed 10 pictures of facial expressions of emotion while they experienced a happy mood and 10 pictures while they experienced a sad mood. Later, while re-experiencing either a happy or sad mood, they were tested for recognition of these 20 target pictures intermixed with 20 distractors. Recognition of the 10 pictures seen earlier in a disparate mood was impaired significantly when they were presented at testing to the right hemisphere, but not when presented to the left. The right hemisphere appears to store the subject's mood as an integral part of a memory representation for an emotionally expressive face. When that face is presented at testing to the right hemisphere, recognition depends on whether the subject's test mood matches the mood stored in the representation. In contrast, the left hemisphere appears to store the subject's mood separately from encoded visual information about a face, and so recognition of a face presented at testing to the left hemisphere is unaffected by changes in mood.