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Biomedical subjects

J R Ison

Publications and source records attributed to J R Ison.

At least 55 records · Page 3Linked to original sources
PubMed1982

Conditions that affect the thresholds of the components of the eyeblink reflex in humans.

The threshold stimulus intensities for elicitation of the two EMG components of the eyeblink reflex were determined in human subjects under different conditions. In the first experiment subjects sat with eyelids open and were not warned about reflex elicitation. The threshold of R1 was substantially greater than that of R2. In four additional experiments subjects (a) triggered the eliciting stimulus, (b) were warned about the arrival of each stimulus, (c) had a conditioning stimulus presented before reflex elicitation, and (d) had their eyelids closed at the time of stimulus delivery. The conditions of these subsequent experiments reduced the difference between the reflex thresholds largely by lowering the R1 threshold. These results indicate that variations in the testing environmental contribute to the discrepancy between our data showing unequal threshold for elicitation of the R1 and R2 components and other reports showing equal thresholds. The results are also another illustration of the ability of complex psychological events to selectively affect different reflex pathways.

Adolescent↗
PubMed1982

Temporal acuity in auditory function in the rat: reflex inhibition by brief gaps in noise.

The acoustic startle reflex in the rat is inhibited if a relatively weak stimulus precedes the startle-eliciting tone burst. This research explored the effect of brief silent periods (gaps) in white noise on the startle reflex, in order to describe the limits of temporal resolution in the auditory system of the rat. Brief silent periods did depress reflex behavior, and two responsible processes were identified. One was most evident at a 190-msec lead time between gap and startle tone. It yielded a linear decrement in reflex expression over a dynamic range of 0-7 msec, and an estimate for the threshold of temporal acuity of 3.5 msec. The second was evident primarily at a 40-msec interstimulus interval and had a linear effect over a dynamic range of at least 40 msec. Very brief gaps had a greater inhibitory effect at the 190-msec interval between gap and startle stimulus; prolonged gaps had their greater effect at the 40-msec interval. The first process was identified as reflex inhibition, which is sensitive to the sensory properties of the lead stimulus. The second process was identified as sensory adaptation, produced by noise exposure but unmasked by silence.

Adaptation, Physiological↗
PubMed1981

Ontogeny of control over the acoustic startle reflex by visual prestimulation in the rat.

In Experiment I, rats 13-35 days of age were presented with acoustic startle stimuli in conjunction with light flashes or noise bursts at 4-320 msec lead times. Inhibition of the startle reflex by leading noise bursts was present on Days 13-15, whereas light flashes were not effective until Days 21-23. In Experiment II, 3 intensities of noise and 3 intensities of light preceded the reflex-eliciting stimuli on Days 16 and 35. All intensities of noise were effective on Day 16, whereas no visual stimuli were. On Day 35, all stimuli were effective. These data reveal that intrinsic visual structures and/or connections between these structures and reflex-control mechanisms mature relatively late in the rat.

Aging↗
PubMed1980

A silent period in orbicularis oculi muscles of humans.

Surface electromyographic activity was recorded bilaterally from orbicularis oculi muscles when subjects relaxed and contracted eyelid muscles. Cutaneous reflex responses were evoked during both the relaxed and contraction states. Following reflex elicitation periods of muscle silence in orbicularis oculi were observed for about 10 to 15 ms after the ipsilateral R1 response and for up to 100 ms after the bilateral R2 responses. Reflex responses appeared to be enhanced when elicited during contractions. Possible physiological mechanisms are discussed regarding the presence of silent periods in a motor system that is presumably devoid of spindles, Golgi tendon organs, and Renshaw-like interneurons.

Adult↗
PubMed1979

Development of the acoustic startle response in the rat: ontogenetic changes in the magnitude of inhibition by prepulse stimulation.

Three experiments examined the development of the acoustic startle reflex and its modification by a preliminary stimulus in the infant rat during the 2nd and 3rd postnatal weeks. The 1st experiment employed a white noise S1 (20 msec, 70 dB), the 2nd a cutaneous S1 (.5 msec, .5 mA and 1.0 mA shock), and the 3rd identical S1-S2 pairs (20 msec, 10 kHz, 110 dB tones). The results demonstrate a similar maturation of the prepulse modification pattern over days in the 3 experiments, evidenced mainly in the growth of inhibition. The findings indicate peripheral and central mechanisms that are maturing during the period of life under observation and that contribute to the developmental patterns of modification.

Acoustic Stimulation↗
PubMed1979

Conditioning auditory stimuli and the cutaneous eyeblink reflex in humans: differential effects according to oligosynaptic or polysynaptic central pathways.

Electromyographic activity of orbicularis oculi muscles in humans was elicited by percutaneous electrical stimulation of the supraorbital brahcn of the trigeminal nerve. The reflex consists of an early brief ipsilateral R1 and a later prolonged consensual R2. The threshold for R1 was considerably elevated compared to that of R2. In one experiment brief acoustic stimuli, at 70 dB SPL, were presented at various intervals, from 5 to 800 msec, prior to the eliciting stimulus. In a second experiment similar stimuli, with intensities varying from 30 to 70 dB SPL, were given at the fixed lead time of 100 msec. In each experiment the preliminary acoustic stimulus enhanced R1 and depressed R2. Potentiation of R1 developed more rapidly than did depression of R2 and exhibited an early and a late peak, whereas depression had a single intermediate trough. Both effects linearly increased with increases in the intensity of the acoustic prepulse. These restuls are discussed in relation to the neuronal circuits responsible for the expression of the two reflex components.

Acoustic Stimulation↗
PubMed1979

Modulation of the acoustic startle reflex in humans in the absence of anticipatory changes in the middle ear reflex.

If a weak tone precedes an intense tone, then the acoustic startle eyeblink reflex elicited by the stronger stimulus is inhibited. It has been suggested that the leading stimulus gives rise to a protective middle ear reflex that attenuates the effective intensity of the second. This hypothesis was tested and disproved. In seven subjects intense tone bursts sufficient to elicit both intratympanic and eyeblink responses were presented sometimes alone and sometimes preceded at various lead times (25 to 400 msec) by a weak tone. The weak tone inhibited the amplitude of the eye blink to the strong tone, maximally at intervals of 100 to 200 msec, but was never seen to produce any of the anticipatory impedance changes that would be characteristic of middle ear reflex activity during the interval between the two stimuli.

Adolescent↗
PubMed1979

Temporal integration of acoustic stimulation obtained in reflex inhibition in rats and humans.

An acoustic stimulus (S1) presented just before reflex elicitation inhibits reflex expression. The present studies questioned whether inhibition provided by initial stimuli of various durations conforms to established temporal integration functions. Initial stimuli were noise bursts varying in duration (2, 20, or 200 msec) and intensity (55 or 85 dB). Eliciting stimuli (S2) for rats were intense tone bursts, which elicited the acoustic startle reflex, and for humans electrotactile stimuli to the forehead, which elicited the eye blink. Findings revealed that inhibition was greater with the 85-dB S1 stimulus and increased linearly with log increases in duration. These latter data suggest that the acoustic substrate for reflex inhibition has a long-time constant. There was one exception to this general finding. For seven (of nine) human subjects, inhibition declined when the duration of the 85-dB S1 was increased from 20 to 200 msec. Postexperimental questioning and video monitoring suggest that this anomaly resulted from a reflex enhancing arousal process.

Acoustic Stimulation↗
PubMed1979

Reflex modulation and loudness recruitment.

Eyeblink reflexes to airpuffs to the orbit are inhibited by preliminary tones even of low intensity, and the amount of inhibition or "reflex modulation" (RM) is correlated with tone loudness. Brief pure tones were presented 100 msec prior to an airpuff to the eye and eyeblink amplitude was recorded in 7 normal-hearing adults. Tones of several levels were either in quiet or in a white noise of 73.5 dbC. As tones increased in intensity, RM increased faster to stimulation in the masked than in the unmasked ear, simulating the classical "pseudo-recruitment" in the noise-masked ear. In addition, very rapid growth of RM was found at 4 kc/s in a patient with sensorineural impairment of 70 db at that frequency as compared with the RM from a frequency with normal HTL. These data confirm the potential of RM in the objective quantification of loudness recruitment.

Acoustic Stimulation↗
PubMed1977

Inhibition of the human eyeblink reflex: an evaluation of the sensitivity of the Wendt-Yerkes method for threshold detection.

In two experiments, human subjects showed a reduced eyewink reflex to an airpuff (S2) if it was preceded by a light flash or a noise burst (S1). The first (N=6) showed that a light inhibited the blink maximally at a 100-msec lag. In the second (N=8), thresholds for noise pips were established with the method of limits. Then the pips were presented in multiples of threshold values as S1 100 msec before S2. Sujbects pressed a button whenever they heard the sound, on S1-S2 pairs, on S1 alone, or on S2 alone trials. Eyeblinks to S2 declined in amplitude and increased in latency as S1 intensity increased. The threshold S1 (approximately 2 dB over a 50-dB background) produced reliable inhibition in 7 of 8 subjects, and a weaker S1 which never evoked a button press was sufficient to produce reliable inhibition for the group as a whole. Inhibition in any particular trial was unrelated to button pressing. The sensitivity of the reflex technique and its relative invariance to task demands suggest its usefulness as a behavioral psychophysical procedure.

Acoustic Stimulation↗
PubMed1975

Combination rules for inhibitory stimuli.

Startle reactions are inhibited if their elicitation is preceded by weak neutral stimuli at lead times of fractions of a second, or by intense startle-eliciting stimuli at lead times of up to several seconds. In three experiments (a) two weak stimuli, (b) one weak stimulus and one intense stimulus, or (c) two strong stimuli were given in combination. In all three conditions the combination provided more response inhibition than did either stimulus alone. Conditions 1 and 2 gave combination effects in which the inhibited proportion of the response was described by the rule for compounding the probabilities of independent events, indicating that the stimuli had noncompetitive independent access to the inhibitory machinery. The rule over-estimated the effect of the compound in Condition c, suggesting the presence of some other summative process, perhaps involving the prolongation of the refractory period.

Acoustic Stimulation↗
PubMed1975

Acoustic startle reflexes in the rat during consummatory behavior.

Auditory startle reflexes were elicited in thirsty rats when they were drinking water or were between drinking boutsmthe reaction was greater during drinking, this enhancement developing over the first few seconds after drinking onset. The startle reaction was lowest immediately after the termination of drinking. Reflex enhancement was reduced when thirsty rats drank milk rather than the more preferred water. The reflex was smaller with increased water deprivation, but enhancement produced by drinking was apparent at all levels of deprivation studied, satiety to 4-days deprivation. The inhibitory effect of a preliminary stimulus was not affected by consummatory behavior. Attention is drawn to suggestive parallels between these behavioral effects and other consequences of consummatory activity, primarily having to do with electrophysiological events and arousal processes

Acoustic Stimulation↗