| |
Abstract:
Neuropsychological studies in depression have suggested right
hemisphere (RH) dysfunction. We previously found LVF RT slowing in
depression and normal sadness. We proposed that sad mood affects a
RH attentional subsystem regulating alertness to external stimuli
(Pardo et al, 1990). In support of this hypothesis, in a recent PET
study of induced sadness in normals, we found striking RH rCBF
decreases in prefrontal and parietal cortex relative to baseline
mood rest. The present study studied the ERP correlates of mood
changes in 8 unipolar depressed women in remission (>1yr).
Subjects performed a visual vigilance task at the baseline mood,
and after acute sadness provoked using personal memory scripts.
Subjects watched rapid streams of unilateral or bilateral letters
(Xs, 20%,targets; Os, 80%, distractors) while maintaining fixation,
and pressed a key to the targets. 64 channels of EEG were
simultaneously recorded. Mood ratings were collected before each
block. With mood provocation, all patients became sad, and their RT
performance was significantly impaired. The most prominent ERP
changes during the sad mood affected the P3 (350-600 ms) to
double
targets. Over the right frontal scalp, P3 amplitude was
significantly decreased independent of hemifield, suggesting an
effect on a system regulating alertness to all external stimuli.
Over right parietal scalp, P3 amplitude was selectively decreased
to double targets
in the LVF
, suggesting a mood influence on the posterior attentional system,
in agreement with studies (e.g. Posner et al, 1987) and theories
(Heilman, 1995) of human neglect emphasizing a deficit of arousal.
Supported by a grant from the McDonnell-Pew Foundation to
M.L.
|
