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Biomedical subjects

J R Ison

Publications and source records attributed to J R Ison.

At least 37 records · Page 2Linked to original sources
PubMed1990

Inhibition of the cutaneous eyeblink reflex by unilateral and bilateral acoustic input: the persistence of contralateral antagonism in auditory processing.

The eyeblink reflex elicited by a cutaneous stimulus is inhibited by weak auditory stimuli that are heard just before the blink. It has been shown that monaural prestimuli produce more reflex depression than binaural prestimuli do, suggesting that reflex modification is sensitive to the outcome of antagonistic connections between contralateral auditory inputs. We examined the time course of this antagonism by giving unilateral versus bilateral pairs of noise pips 100 msec before the reflex eyeblink, with the noise pips separated by 0, 1, 4, or 8 msec. Unilateral stimuli were more effective in every condition, but their advantage diminished with increased delay between the two components. The extended bilateral and unilateral trends of increasing reflex depression with increased delay meet at about 15 msec; if this extrapolation is valid, 15 msec represents the upper limit on this system's retention of the location of a brief noise impulse. The rate of convergence of the two temporal functions reflects the decay of the antagonistic effect of one noise on its contralateral counterpart.

Adult↗
PubMed1990

Spectral frequency and the modulation of the acoustic startle reflex by background noise.

The rat's (Long-Evans) acoustic startle reflex to a high-frequency tone burst (10.5 kHz) was depressed by intense high-frequency band-pass noise (8-16 kHz) but enhanced by low frequency noise (1-2 kHz). However, contrary to the hypothesis that the depression of startle in intense background noise is produced by sensory masking, the reflex to a low-frequency tone burst (at 1 kHz) was depressed by both high- and low-frequency band-pass noise. Two additional hypotheses are offered to supplement sensory masking in order to explain the asymmetry in these data. The first is that the intratympanic reflex, which acts as a high pass filter on acoustic input, is elicited in intense backgrounds. The second is that acoustic startle reflexes elicited by intense low-frequency tones are in part elicited by their high-frequency distortion products and that these distortion products are then masked by high-frequency background noise.

Animals↗
PubMed1989

The acoustic startle response and disruption of aiming: I. Effect of stimulus repetition, intensity, and intensity changes.

Three experiments examined the disruption of perceptual motor performance by intense noise bursts. Subjects aimed a rifle at a fixed target for 15-s periods separated by 15 s of rest. This cycle was repeated 30 times in each of two series separated by a 15-min rest, each series containing five noise bursts. The noise bursts disrupted aiming for 1-2 s, an effect that increased with sound pressure level for 110, 120, and 130 dB stimuli. There was no difference between stimuli with energy centered on 250 Hz as opposed to 800 Hz. The effect diminished over the five bursts within the first series (but not to zero) and did not recover in the 15-min rest period. Some subjects received three days of testing; in these cases the effect of the noise bursts partially recovered after rest intervals of 24 hrs and then seven days. Other subjects received 15 trials with 110-dB stimuli, then five more trials with 130-dB stimuli. The disruption of aiming by 130 dB stimuli was not reduced by prior exposure to 110-dB stimuli.

Adult↗
PubMed1989

The acoustic startle response and disruption of aiming: II. Modulation by forewarning and preliminary stimuli.

Four experiments examined the disruption of rifle aim by intense noise bursts. In Experiment 1 a trigger pull was followed occasionally by a noise burst. Aiming was disrupted for 1-2 s, an effect that habituated within days and recovered between days. Expected stimuli were less disruptive than were unexpected stimuli. Experiment 2 demonstrated that weak auditory prestimuli 100 ms before unexpected intense sounds also reduced noise-produced errors. Experiment 3 showed that the intratympanic reflex had not played a protective role in this effect. Experiment 4 showed that a weak tactile prestimulus increased both a muscular measure of the acoustic startle reaction and the perturbing effect of the noise burst on motor performance. In general, conditions that affect the amplitude of the acoustic startle reflex similarly influence the disruptive effect of a noise burst on motor performance, but the two measures are not correlated in the detail necessary to suggest a causative relationship.

Adult↗
PubMed1986

Visual function measured by reflex modification in rats with inherited retinal dystrophy.

Developmental changes in visual function were studied in the Royal College of Surgeons (RCS) rat with inherited retinal degeneration by examining the inhibition of acoustic startle reflexes by visual prestimuli. Compared with a congenic strain of nondystrophic rat, the RCS rats showed an increase in the interstimulus interval between the inhibitory prestimulus and the eliciting stimulus that produced maximal inhibition, a result suggesting a decrease in the speed of processing. The amount of inhibition also decreased over time, which suggests a progressive loss of visual function. Simultaneous presentation of auditory and visual prestimuli was used to demonstrate that the changes in inhibition were related to alterations in visual function and that auditory function was not impaired in these rats. The results show that reflex modification is a suitable test for evaluating visual dysfunction in rats.

Acoustic Stimulation↗
PubMed1985

Cutaneous and auditory function in rats following methyl mercury poisoning.

Rats were given a total dose of 50 mg/kg (Exp. 1), 13.3 or 40 mg/kg (Exp. 2), or 40 mg/kg (Exp. 3) of methyl mercury chloride subcutaneously over a course of 5 days. At varying times after the toxic exposure, up to 1 year, their sensory functioning was assessed by reflex modulation methods: stimuli of interest were presented just before an intense tone which elicited the startle reflex, and stimulus reception was measured by the inhibitory control of the stimuli over the amplitude of the reflex. In Experiment 1 cutaneous prestimuli (electric shock to the tail) and brief acoustic transients (silent periods in noise) were less effective inhibitors of reflex activity in poisoned animals, compared to controls, indicating that the poisoned animals had impairments in cutaneous sensitivity and audition. In Experiment 2 the time course of sensory loss and subsequent recovery was studied. Impaired auditory function was shown further by a deficit in the effectiveness of weak noise pulses, and, in addition, the cutaneous deficit for weak tail shocks was accompanied by an exaggerated or hyperpathic response to more intense tail shocks. Experiment 3 confirmed the finding that the loss of sensitivity to weak shock was accompanied by an enhancement of the response to more intense shock. These data were related to peripheral neuropathy and shown to be analogous to certain clinical symptoms of Minamata disease reported in humans.

Acoustic Stimulation↗
PubMed1985

Impairment in auditory and visual function follows perinatal viral infection in the rat.

Acoustic startle reflexes are elicited by intense tone bursts but inhibited if weak bursts precede reflex elicitation. Rats were infected by intracerebral inoculation with lymphocytic choriomeningitis virus (LCMV) at birth. Compared to control animals, infected animals had higher elicitation and inhibition thresholds and showed recruitment at intense stimulus levels. Histopathology revealed both cochlear and retinal degeneration. Like some infectious agents in humans, perinatal exposure to LCMV in the rat yields a severe polysensory neuropathy.

Animals↗
PubMed1985

Genetic differences in avoidance learning by Rattus norvegicus: escape/avoidance responding, sensitivity to electric shock, discrimination learning, and open-field behavior.

The behaviors of rats selectively bred for either good or poor shuttle box avoidance learning were studied. The results of Experiment 1 indicated that the phenotypic difference in avoidance learning is not associated with differences in speed of escape or avoidance responding. Differences between the lines in frequency of intertrial responses (ITRs), which appear during training but not during pretest, suggest that ITRs in animals of the low-avoidance (SLA) line are more suppressed by electric shock than in animals of the high-avoidance (SHA) line. This result suggests that SLA animals may be more emotionally responsive than SHA animals. Experiment 2 demonstrated that the animals of the two lines do not differ in absolute sensitivity to electric shock, and Experiment 3 showed that the poor performance of the SLA line is not due to an inability to learn. Experiment 3 also provided evidence which suggests that the poor avoidance learning by SLA animals is due to their emotional reactivity. Observations of open-field behavior in Experiment 4 are consistent with this hypothesis. The major consistent correlate of the phenotypic difference in avoidance learning is greater emotionality or emotional reactivity in SLA than in SHA animals.

Animals↗
PubMed1984

Acute exposure to methyl or ethyl alcohol alters auditory function in the rat.

Effects of alcohol on audition were studied in the rat by examining the modification of acoustic startle reflexes by pure tone pulses and by gaps in white noise. Systematic inhibition of the startle reflex by variation in pulse intensity provides an objective measure of loudness perception, while variation in gap duration assesses temporal acuity. Groups of rats (n = 8) received four injections of 0.0, 0.25, 1.00, and 2.00 g/kg of either methyl or ethyl alcohol in increasing order at 1-hr intervals. One-half hour after the administration of each dose, loudness perception or temporal acuity was measured. Blood alcohol levels (mM) for the two alcohols obtained in control animals were equivalent following the final dose. Alcohol produced a dose-dependent reduction in baseline startle amplitude that was greater during exposure to ethanol than during methanol. Loudness functions associated with pulse intensity were not diminished by alcohol; however, inhibition produced by a gap in noise was reduced following the highest dose of either alcohol. These data are consistent both with behavioral studies that have suggested that alcohol does not affect loudness perception, and with electrophysiological experiments which indicate that alcohol disrupts temporal relationships along the primary auditory pathway.

Acoustic Stimulation↗
PubMed1984

Startle reflex inhibition in the rat: its persistence after extended repetition of the inhibitory stimulus.

Startle reflexes to intense sound bursts are inhibited by weak stimuli that briefly precede their elicitation. In three experiments the startle stimulus (a 110-dB SPL tone burst) was presented 100 ms after the final link in a train of stimuli, the length of the train varying from 1 to 1,000, its repetition rate varying from 1 per s to 10 per s, and its constituents being 40 dB or 50 dB white noise bursts of 25 ms duration. Inhibition was invariant across train length and repetition rate. In a final experiment the startle stimulus was presented a variable interval after the final link, from 40 ms to 1280 ms, with 1 or 100 noise bursts (50 dB) in the train. Inhibition developed more rapidly following the last member of the 100-stimulus train, suggestive of a "priming" or sensitization effect of stimulus repetition, but its overall strength and subsequent rate of decay were not different in the two conditions. The general persistence of inhibition following these extended series of stimuli reveals that reflex inhibition must be the outcome of a fixed and obligatory process associated with sensory input.

Acoustic Stimulation↗
PubMed1983

Prenatal diazepam exposure: effects on auditory temporal resolution in rats.

The maturation of temporal acuity in the auditory system of the rat was evaluated following prenatal exposure to diazepam (DZ; 0, 2.5, 10 mg/kg to the dam on each of the last 8 days of gestation). Acuity was defined by the effectiveness of brief silent periods in white noise (gaps) as in inhibitors of an immediately subject acoustic startle reflex. In uninjected control rats the gaps became effective at 25-28 days of age, and onset was delayed in prenatally exposed animals according to dose. No DZ was present in the rat offspring at animals in adulthood (0, 0.5, 1.5, 4.5 mg/kg). These injections reduced the inhibitory effect of the gap on startle behavior in all animals, but less so in those previously exposed to DZ in utero. The threshold of temporal acuity in the rat approximates that found in humans and the function matures at the same relative rate in the two species. Further, administration of DZ in the adult human has the same effect on temporal acuity in the auditory system as it does in the adult rat. There are presently no data available on the effects on human auditory development of exposure to DZ in utero. The data we present have the importance of temporal acuity in the perception of speech and, thus, in the maturation of language ability.

Animals↗
PubMed1983

Habituation and sensitization of components of the human eyeblink reflex.

The supraorbital branch of the right trigeminal nerve was stimulated with trains of electric shocks, 10 in each train, with interpulse intervals of 1, 2, or 5 sec. Electromyographic reflex activity in the palpebral musculature was measured to each pulse in the train. Each response consisted of two components, a fast brief ipsilateral burst (R1) and a slower prolonged bilateral burst (R2). Over the 10-pulse series, the amplitudes of R1 increased in strength (sensitization), whereas the allied R2 amplitudes declined (habituation). Both of these effects were enhanced as the interpulse interval was reduced. A consideration of the anatomical substrate for each reflex component, together with some other data in the literature, suggests that reflex sensitization occurred in the efferent limb of this brain stem reflex while simultaneously habituation occurred in its central link.

Adult↗
PubMed1982

Selective action of morphine on reflex expression to nociceptive stimulation in the rat: a contribution to the assessment of analgesia.

In two experiments startle reflexes to both loud noises and electric shocks were elicited in rats. The two stimuli were paired so that the inhibitory effect of each stimulus on the response to the other could be assessed. In the first study it was shown that morphine (0-16 mg/kg) had a selective and dose related depressive effect on the response to shock. The response to a leading tone and inhibition produced by the shock on the response to a following tone were minimally affected. In the second study, morphine (10 mg/kg) again depressed the reaction to shock but not to tone, and its effect was antagonized by naloxone (10 mg/kg). The selective effect on responses to shock, leaving responses to tone relatively unaffected, reveals that reflex depression should not be attributed to a loss in motor functions. Further, that morphine had little effect on reflex inhibition produced by the shock suggests that the nociceptive properties of shock were affected rather than simple sensory processes. It is proposed that the method described here is useful for assessing changes in nociception in laboratory animals, and for discriminating between nociceptive, afferent, and efferent processes.

Acoustic Stimulation↗