Affective modulation of the startle reflex following traumatic brain injury

Diminished emotional recognition, expression, and responsivity are frequent legacies of traumatic brain injury(TBI) that can have an adverse impact on relationships and psychosocial recovery. However, assessment of emotionresponsivity is often difficult because many patients lack insight into their altered personality. To overcome thisobstacle, we used a physiological measure of emotion responsivity, the startle reflex, to examine how this can varyaccording to the affective valence of stimuli by comparing a TBI group with a matched control group. The studyalso examined whether weaknesses of attention and speed of information processing could account for differencesin startle modulation across groups. Sixty-four TBI patients and controls completed the startle reflex procedure.Participants were presented with pictures that differed in affective valence, and measures were taken of eyeblinkstartle responses to an acoustic probe. Subjective ratings of affect and arousal for each picture were obtained, andTBI patients completed measures of attention and information processing. Results revealed that the TBI groupdid not show the pattern of startle modulation observed in the control group. Whilst pleasant pictures producedthe usual attenuation of the startle response, startle responses to unpleasant pictures were significantly lower inthe TBI group than in controls. No significant correlations emerged between startle responses and performance onneuropsychological measures in the TBI group. The TBI group also rated unpleasant pictures as significantly lessarousing than did controls. The results provide partial support for a growing body of evidence that has proposedimpaired emotion responsivity following TBI