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Biomedical subjects

W W Henton

Publications and source records attributed to W W Henton.

12 recordsLinked to original sources
PubMed1984

Recovery of absolute threshold with UVA-induced retinal damage.

A within-trial psychophysical procedure tracked the initial loss and subsequent recovery of visual thresholds in albino rats exposed to ultraviolet light at 350 nanometers and 0.4 milliwatts per square centimeter. Absolute thresholds increased up to 5 log units immediately following the 15 hour ultraviolet exposure, with a daily recovery of 1-2 log to asymptotic thresholds over a 7-day post-exposure period. The corresponding retinal damage on Day 1 included extensive vesiculation of the photoreceptor outer segments, vacuolation of the inner segments, and pyknosis of cell nuclei. The total number of photoreceptor nuclei and outer segments was unchanged relative to control eyes through post-exposure Day 3. Both nuclei and outer segment counts then consistently decreased 15-20 percent between Days 3-7. The two-stage loss of photoreceptors but daily recovery of absolute thresholds again suggests a significant dissociation of retinal structure and psychophysical function in light-induced ocular pathology.

Animals↗
PubMed1983

Changes in absolute threshold with light-induced retinal damage.

Albino rats were trained on a mixed signalled reinforcement procedure designed to yield repeated absolute visual thresholds within each session. After threshold stability animals were exposed 12 hours per night to 1000 lux of light froma cool-white fluorescent source. Log threshold rose as an approximate linear function of exposure time to a maximum of 2.0 log units above baseline after 36 cumulative hours of exposure. Light and electron microscopic analysis of the irradiated retinas revealed vesiculated photoreceptor outer segments, with varying degrees of vacuolation of the inner segments and pyknosis of photoreceptor nuclei depending on exposure time. The various combinations of retinal pathology suggests that damage to photoreceptor outer segments and inner segments interact to jointly affect psychophysical thresholds in light-induced retinal damage.

Animals↗
PubMed1982

Control of wheel running by near-ultraviolet light.

Wheel running by mice was compared during incandescent and incandescent plus near-ultraviolet (UV) illumination in three experiments. During the daily 12-hour light period, running rates decreased with supplemental UV compared to previous incandescent only baselines. The decrements were systematically replicated in a second experiment using alternating UV exposure and recovery phases programmed across blocks of sessions. Again, running rates consistently decreased with supplemental UV irradiation of phases two and four compared to preceding baselines of phases one and three. In comparison, running rates were inconsistently affected during the 12-hour dark period in both experiments. A third experiment compared the relative decremental effects of UV, blue and red illumination. Baseline running rates monotonically decreased as an inverse function of wavelength for all subjects. The data suggest that the spectral composition of ambient illumination may affect behavior.

Animals↗
PubMed1972

Avoidance response rates during a pre-food stimulus in monkeys.

Free-operant avoidance responding was maintained by a shock avoidance schedule in three monkeys. The frequency of avoidance responses during a stimulus terminated by response-independent food pellet presentation was dependent upon the method of pellet delivery. Avoidance rates were relatively increased when food retrieval responses followed pellet delivery. Avoidance rates were decreased when retrieval responses preceded pellet delivery.

Animals↗
PubMed1970

Operant acceleration during a pre-reward stimulus.

Stimuli of 20, 40, and 80 sec duration terminated with five non-response-contingent food pellets were superimposed upon lever pressing reinforced with single pellets on a DRL 30-sec schedule. Two rhesus monkeys served as subjects. No change in response frequency was observed during the 20- and 40-sec stimuli. During the 80-sec pre-food stimulus, overall response frequency increased to approximately 150% and 220% of pre-stimulus levels, and the temporal distributions of interresponse times shifted toward the shorter intervals. When the 80-sec stimulus was no longer terminated with food, the response frequency decreased and the temporal distributions of interresponse times gradually approached pre-stimulus levels. An increased frequency of short interresponse times and an increase in response rate was again observed when the pellet termination procedure was reinstituted with the 80-sec stimulus. No change in response frequency or interresponse times was observed in the absence of the conditioning stimulus, and performance efficiency, as reflected in the ratio of responses to reinforcements during non-stimulus periods, remained stable throughout the experiment.

Journal Article↗
PubMed1969

Conditioned suppression to odorous stimuli in pigeons.

The conditioned suppression technique was employed to establish criterion discrimination of an amyl acetate concentration of 3% of vapor saturation, and to generate differential response rates in the presence of equal concentrations of amyl acetate and butyl acetate. The magnitude of suppression was also recorded as a function of amyl acetate concentration, with the concentrations presented in descending, ascending, and irregular series. The three stimulus presentation procedures generated approximately equivalent suppression versus concentration functions. Amyl acetate suppression thresholds were 0.16%, 0.50%, and 0.73% of vapor saturation for three subjects. Amyl acetate, butyl acetate, and butyric acid thresholds for two additional subjects were approximately 0.10% of vapor saturation. No suppression was recorded during control trials.

Acetates↗
PubMed1966

Odor discrimination in pigeons.

An operant procedure was employed to investigate odor discrimination in the pigeon. Amyl acetate concentrations of 6-percent saturation in air, and lower, when paired with electric shock markedly reduced key-pecking during the odor stimulus period. Sectioning the olfactory nerves eliminated this selective suppression behavior. After the operation, the suppression was again conditioned when the concentration of amyl acetate was increased to 15-percent saturation in air. This is theoretically possible through mediation by the trigeminal system.

Acetates↗