Anticipatory affective startle modulation in unipolar depression

Abstract

Affective startle eyeblink modulation by unipolar depressed and nondepressed participants was assessed during the anticipation and viewing of emotional pictures. Anticipatory startle probes were presented at 2000 ms and 750 ms before picture onset. Startle probes during picture viewing were presented at 300 ms and 3500-4500 ms after picture onset. Nondepressed participants exhibited the expected arousal-dependent startle modulation to probes presented 2000 ms before picture onset, a trend towards linear valence-dependent startle modulation to probes presented 750 ms before picture onset, no relation between startle modulation and picture category to probes presented 300 ms after picture onset, and the expected linear valence-dependent startle modulation to probes presented 3500-4500 ms after picture onset. In contrast, startle modulation of depressed participants was unrelated to picture valence category at all probe intervals. Depressed participants differed from nondepressed participants in startle potentiation to pleasant pictures at the 2000 ms anticipatory interval and in linear startle modulation to probes presented 3500-4500 ms after picture onset. There were no between-group differences with respect to the other two probe conditions, self-report ratings of picture valence, or voluntary viewing time. These results replicate prior findings that late-probe blink magnitudes of depressed participants are unrelated to picture valence and demonstrate attenuated anticipation of pleasant stimuli by depressed participants. Diminished startle modulation during the anticipation of pleasant pictures in individuals with unipolar depression may represent a novel method to assess anhedonia.