REDUCED ELECTROCORTICAL RESPONSES TO PLEASANT PICTURES IN DEPRESSION: A TIME-DOMAIN AND TIME-FREQUENCY DELTA ANALYSES

The late positive potential (LPP) to pleasant content is
an electrocortical indicator of blunted emotional reac-
tivity in depression. Additional insight into emotional
reactivity can be provided using time- frequency decom-
position. The present study examined time- frequency
delta in depression and investigated whether the com-
bination of time-domain and time-frequency data would
explain additional variance in the depression status. The
study was a secondary analysis of data collected during
a passive viewing task of pleasant and neutral pictures
in a community-based sample of 75 participants with
a current depressive disorder and 42 controls. A time-
frequency analysis on event- related changes within delta
frequency band was conducted. Cluster- based statistics
revealed a centro-parietal increase in delta power to
pleasant relative to neutral pictures in the control group
but not within the depression group. Moreover, a fronto-
centro-parietal reduction in delta power to pleasant pic-
tures emerged in depression relative to controls. Both a
smaller LPP and delta power to pleasant pictures were
related to depression status. The combination of LPP and
delta power explained a greater amount of variance com-
pared to the model where LPP was entered as the only
predictor of depression status. These data suggest that
delta power might be a promising correlate of the hypo-
activation of the approach motivational system in depres-
sion. A combination of these measures can be leveraged
together to enhance clinical utility and to shed light on
the underlying mechanisms associated with depression.