Prestimulus Effects on Human Startle Reflex in Normals and Schizophrenics

TLDR

Graham (1975) demonstrated that a weak prestimulus could effectively inhibit or facilitate the eyeblink component of the startle reflex in humans, depending on the temporal duration of the prestimulus. This study had three goals: to replicate Graham’s findings, to establish the reliability of this phenomenon by a test‑retest comparison, and to compare the eyeblink reflex response of normal subjects with schizophrenic subjects. Seven prestimulus durations of continuous tone (from 0 to 2000 msec) were presented to 20 normal subjects, confirming that maximal inhibition of eyeblink amplitude occurred at the 120‑msec prestimulus condition. The study found that maximal inhibition of eyeblink amplitude occurred at 120 msec, increased amplitude was nonsignificant at 2000 msec, the effect was reliably reproduced in 14 of 20 normals on retest, and schizophrenic subjects showed significantly different blink amplitude and latency at 60 msec, supporting sensory overload theories and suggesting that the blink reflex is stable yet altered in schizophrenia and/or by antipsychotic medication.

Abstract

ABSTRACT Graham (1975) demonstrated that a weak prestimulus could effectively inhibit or facilitate the eyeblink component of the startle reflex in humans, depending on the temporal duration of the prestimulus. This study had three goals: 1) to replicate the findings of Graham, 2) to establish the reliability of this phenomenon by a test‐retest comparison, and 3) to compare the eyeblink reflex response of normal subjects with schizophrenic subjects. Seven prestimulus durations of continuous tone (from 0 to 2000 msec) were presented to 20 normal subjects and the results confirmed that maximal inhibition of eyeblink amplitude occurred in the 120 msec prestimulus condition. Increased amplitude occurred nonsignificantly when the prestimulus lasted for 2000 msec. On retest, 14 normal subjects showed a significant degree of reliability. When 20 normal subjects were compared to 12 schizophrenic subjects, significant differences in eyeblink response were found for blink amplitude and latency in the 60 msec prestimulus condition. This change is consistent with information processing “overload” theories of sensory overstimulation in schizophrenia. The blink reflex is a rather stable phenomenon and is probably altered in schizophrenia and/or by antipsychotic medication.