Modification of the rat's startle reaction by an antecedent change in the acoustic environment.

Abstract

A series of experiments related inhibition and facilitation of the startle response, elicited by an intense auditory signal, to a change of the frequency characteristic of a 70-db. continuous acoustic signal. The data indicated that if a frequency change occurs in the acoustic environment 64 msec, before the startle-eliciting stimulus, the amplitude of the startle response is reduced; and if frequency change occurs 4 msec, prior to the startle-eliciting stimulus, the response latency is reduced. These results extend the generality of previous research employing weak antecedent acoustic signal onset and offset. The results indicate that neural mechanisms mediating the startle reflex may be activated by any change in the acoustic environment and that these mechanisms may be a component of the orienting reflex arc.

Tonal frequency shifts and gaps in acoustic stimulation as reflex-modifying events

“…The amount of inhibition produced by the offset condition was equal to that produced by the gap-no shift condition and less than that produced by the shiftgap and onset conditions. The finding that the onset condition produced more inhibition than did the offset condition is contrary to previous reports of equivalent amounts of inhibition (Hoffman & Stitt, 1980;Stitt, Hoffman, & Marsh, 1973;Stitt et at, 1974). The differences may lie in the nature of the stimuli employed; for instance, the previous studies used bands of noise, whereas the present study employed pure tones.…”

“…Each subject received 12 blocks of trials, each block containing a different randomization of the four stimulus condiThe next step in this series of studies was to determine whether a shift in tonal frequency across a gap in acoustic stimulation would lead to any further reflex inhibition than a gap condition with no frequency shift. Previous work (Marsh, Hoffman, Stitt, & Schwartz, 1975;Stitt et al, 1974) had already indicated that shifts between high-and low-frequency bands of noise could inhibit a startle reflex; the question addressed here was whether similar effects could be obtained when the basic acoustic signal was a tone rather than noise, and when the frequency shift occurred across a gap in a signal that had a slow enough rise time (20 msec) that it would be transient free.…”

“…The bulk of this research was conducted by the first author as part of her doctoral dissertation at Bryn Mawr College. Requests for reprints should be sent to Howard S. Hoffman, Department of Psychology, Bryn Mawr College, Bryn Mawr, PA 19010. nals is that by Stitt, Hoffman, Marsh, & Boskoff (1974). These investigators reported a reduction in startle amplitude in rats following instantaneous shifts between low-band and high-band random noise just prior to a startle-eliciting stimulus.…”

Reflex modification in the rat: The inhibitory effects of intensity and frequency changes in steady tones.

“…Previous work (Marsh, Hoffman, Stitt, & Schwartz, 1975;Stitt et al, 1974) indicated that shifts between high-and lowfrequency bands of noise could inhibit a startle reflex. The question addressed in this experiment was whether similar effects could be obtained when the basic acoustic prestimulus was a pure tone rather than narrowband.…”

“…Investigation of the reflex modification afforded by complex acoustic events began with the work of Stitt, Hoffman, Marsh, and Boskoff (1974). They found that if a small change in the intensity or the frequency of This research was supported by Grant HD 10511 to Howard S. Hoffman from the National Institutes of Health.…”