Biomedical subjects

V B Olszyk

Publications and source records attributed to V B Olszyk.

4 recordsLinked to original sources

PubMed1997

Auditory behavioral thresholds for Japanese macaques using insert earphones.

The goal of this study was to measure behavioral auditory thresholds in four Japanese macaques. Animals were trained using food as a reward in an operant reinforcement paradigm. Stimuli were 1-s sinusoids with 10-ms rise/fall times delivered through insert earphones (Etymotic ER-1) having expandable foam eartips. The animals generally produced threshold contours similar in shape to those reported for other macaques species, except that the low-frequency thresholds may have been slightly higher in the present studies. At middle and high frequencies, thresholds fell at the lower extreme of the range previously reported in other macaque species. The possible difference in low-frequency thresholds may have been a result of either transducer and calibration differences between studies or true species variations, or both. Though somewhat limited at high frequencies, the insert earphones used in these studies offer more reliable calibrations, less susceptibility to changes in positioning with movement of the animal, and greater interaural attenuation.

Animals↗

PubMed1995

Behavioral auditory thresholds for sinusoidal electrical stimuli in the cat.

Behavioral thresholds were measured in four cats by training them to respond behaviorally to acoustic auditory stimuli using food as a reward in an operant reinforcement paradigm. Following training, the subjects were implanted unilaterally with either a scaled-UCSF electrode containing four contacts or an electrode array containing eight intracochlear contacts and one extracochlear contact under temporalis muscle. Behavioral thresholds for electrical stimuli were obtained as a function of sinusoidal frequency, duration, and electrode configuration. Threshold functions for both electrode types and all animals had minima between 48 and 125 Hz and, in general, were relatively flat below this minima; functions increased at 3-6 dB/octave from 96 Hz to 1 kHz. Threshold varied predictably as a function of electrode configuration, with thresholds decreasing as much as 20 dB as electrode spacing was widened from a radial bipolar (200-microns separation) to a monopolar configuration (apical stimulating and temporalis return). With long-duration stimuli, increasing the electrode separation systematically increased the slope of the threshold-versus-frequency contours in all animals. Irrespective of electrode type or configuration, charge/phase thresholds for single-cycle sinusoids were relatively flat for stimulus periods up to 1-5 ms, approximating a constant charge/phase determination of threshold. At phase durations greater than 5 ms, charge thresholds increased at a rate slightly above 6 dB/octave (constant peak current), which was suggestive of neural accommodation. Thresholds for the cat share many features with those reported for implanted humans and monkeys.

Acoustic Stimulation↗

PubMed1994

Behavioral and electrophysiological responses to electrical stimulation in the cat. I. Absolute thresholds.

Estimates of electrical auditory brainstem response (EABR) thresholds are compared with behavioral thresholds for electrical stimulation in the same subject using identical stimuli and electrode configurations. Four cats were behaviorally trained to measure acoustic auditory thresholds using food as a reward in an operant reinforcement paradigm. One of the animals was then implanted, in an otherwise normal ear, with a scaled-UCSF multi-contact electrode array containing four intracochlear electrodes. Three animals were implanted with an electrode array containing eight intracochlear contacts and one extracochlear contact under the temporalis muscle following unilateral cochlear perfusion with 10% neomycin solution. Stimuli for the behavioral studies were single presentations of 200 us/phase biphasic current pulses. For the EABR studies, the same stimulus was presented at a rate of 32/s. In general, for the animal with the four-contact array and two of the three subjects with the eight-contact implant, changes in electrode configuration produced well-differentiated changes in threshold. For these three subjects, comparisons of behavioral and EABR thresholds for the majority of monopolar and bipolar electrode configurations tested showed excellent agreement (r2 = 0.88). Correlations between behavioral and EABR measures in these animals were comparable for bipolar and monopolar arrangements (r2 = 0.88 for bipolar and 0.87 for monopolar). For one subject with the eight-contact electrode, who showed similar monopolar and bipolar electrode behavioral thresholds for all tested electrode spacings or configurations, most EABR thresholds were substantially higher than, and poorly correlated with, behavioral thresholds (r2 = 0.15; r2 = 0.28 for monopolar arrangements, and r2 = 0.12 for bipolar arrangements).

Animals↗

PubMed1991

Behavioral and neurochemical changes in rats dosed repeatedly with diisopropylfluorophosphate.

Behavioral effects of organophosphates (OPs) typically decrease with repeated exposure, despite persistence of OP-induced inhibition of acetylcholinesterase (AChE) and downregulation of muscarinic acetylcholine (ACh) receptors. To characterize this tolerance phenomenon, rats were trained to perform an appetitive operant task which allowed daily quantification of working memory (accuracy of delayed matching-to-position), reference memory (accuracy of visual discrimination) and motor function (choice response latencies and inter-response times during delay). Daily s.c. injections of 0.2 mg/kg of diisopropylfluorophosphate (DFP) caused no visible cholinergic signs, did not affect body weight or visual discrimination, but progressively impaired matching accuracy and lengthened response latencies and interresponse times. These effects recovered in seven of eight treated rats after termination of DFP treatment. Resumption of daily DFP at 0.1 mg/kg caused smaller impairments of both matching accuracy and response latency. After 21 injections of 0.2 mg/kg/day of DFP, rats were subsensitive to the hypothermia induced by acute oxotremorine (0.2 mg/kg i.p.), as expected after OP-induced downregulation of muscarinic ACh receptors. Evidence for supersensitivity to scopolamine (0.03 and 0.056 mg/kg i.p.) in DFP-treated rats was mixed, with additive effects predominating on both the cognitive and motor aspects of the task. After 18 days of 0.1 mg/kg of DFP, AChE was inhibited 50 to 75% and muscarinic ACh receptor density was reduced 15 to 20% in hippocampus and frontal cortex. Progressive declines in AChE activity in hippocampus and frontal cortex across 15 daily doses with DFP at 0.1 and 0.2 mg/kg were observed in other rats; quinuclidinyl benzilate binding was significantly reduced in hippocampus after 15 doses at both levels of DFP. These results indicate that animals showing a definitive sign of tolerance to OP administration (subsensitivity to a cholinergic agonist) were also functionally impaired on both the mnemonic and motoric demands of a working memory task. The nature of this impairment suggests further that it results from compensatory changes in the central nervous system, e.g., muscarinic receptor downregulation, considered to produce "tolerance" to OPs in exposed animals.

Acetylcholinesterase↗