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C D Wynne

Publications and source records attributed to C D Wynne.

10 recordsLinked to original sources
PubMed2000

ERP correlates of response inhibition to elemental and configural stimuli in a negative patterning task.

OBJECTIVE: The present experiment examined the ERP correlates of response inhibition to elemental and configural Nogo stimuli in a Go/Nogo task. DESIGN AND METHODS: Event-related potentials (ERPs) were recorded while 8 subjects completed a visual Go/Nogo task. Nogo stimuli required the inhibition of a response to stimuli that differed from Go stimuli (A+, B+) either on the basis of each of two physical features (elemental Nogo stimuli; CD-) or on the basis of the conjunction of features represented in the Go stimuli (configural Nogo stimuli; AB-). Behavioural data and ERP component measures (amplitude and latency) were analysed using analysis of variance. RESULTS: An enhanced N2 component and an enhanced fronto-centrally distributed P3 component were elicited following elemental Nogo stimuli relative to Go stimuli, consistent with a number of studies examining ERPs during Go/Nogo tasks. In contrast, an enhanced late frontal negative/parietal positive slow wave was elicited following configural Nogo stimuli relative to Go stimuli. CONCLUSIONS: These results cast doubt on the interpretation of the N2 enhancement as reflecting response inhibition processes per se. The pattern of results was interpreted as providing support for the unique cue model of learning rather than the configural model of learning and was discussed in the context of a recent model of executive functioning.

Adult↗
PubMed1999

Preserved negative patterning and impaired spatial learning in pigeons (Columba livia) with lesions of the hippocampus.

Pigeons (Columba livia) with bilateral electrolytic lesions of the hippocampus and area parahippocampalis were compared with control pigeons on 2 tasks: negative patterning and delayed spatial alternation. Negative patterning demands configural stimulus representations for its successful solution. The only effect of hippocampal lesions on this task was an increased response rate to the rewarded stimuli. On the delayed spatial alternation task, hippocampal birds showed deficits relative to controls. Differences in the results of prior studies on negative patterning appear to be due to different response requirements to the nonreinforced stimuli. These results are consistent with prior work with rats and suggest that the avian hippocampus is essential for spatial memory and response inhibition but is not involved in configural learning.

Animals↗
PubMed1996

Dynamics of waiting in pigeons.

Two experiments used response-initiated delay schedules to test the idea that when food reinforcement is available at regular intervals, the time an animal waits before its first operant response (waiting time) is proportional to the immediately preceding interfood interval (linear waiting; Wynne & Staddon, 1988). In Experiment 1 the interfood intervals varied from cycle to cycle according to one of four sinusoidal sequences with different amounts of added noise. Waiting times tracked the input cycle in a way which showed that they were affected by interfood intervals earlier than the immediately preceding one. In Experiment 2 different patterns of long and short interfood intervals were presented, and the results implied that waiting times are disproportionately influenced by the shortest of recent interfood intervals. A model based on this idea is shown to account for a wide range of results on the dynamics of timing behavior.

Journal Article↗
PubMed1992

Waiting in pigeons: the effects of daily intercalation on temporal discrimination.

Pigeons trained on cyclic-interval schedules adjust their postfood pause from interval to interval within each experimental session. But on regular fixed-interval schedules, many sessions at a given parameter value are usually necessary before the typical fixed-interval "scallop" appears. In the first case, temporal control appears to act from one interfood interval to the next; in the second, it appears to act over hundreds of interfood intervals. The present experiments look at the intermediate case: daily variation in schedule parameters. In Experiments 1 and 2 we show that pauses proportional to interfood interval develop on short-valued response-initiated-delay schedules when parameters are changed daily, that additional experience under this regimen leads to little further improvement, and that pauses usually change as soon as the schedule parameter is changed. Experiment 3 demonstrates identical waiting behavior on fixed-interval and response-initiated-delay schedules when the food delays are short (less than 20 s) and conditions are changed daily. In Experiment 4 we show that daily intercalation prevents temporal control when interfood intervals are longer (25 to 60 s). The results of Experiment 5 suggest that downshifts in interfood interval produce more rapid waiting-time adjustments than upshifts. These and other results suggest that the effects of short interfood intervals seem to be more persistent than those of long intervals.

Animals↗
PubMed1991

Dynamics of time discrimination.

Pigeons tracked sinusoidal sequences of interfood intervals (IFIs) by pausing in each interval for a time proportional to the preceding interval. Schedules with either long (30-90 s) or short (5-15 s) values, with variable numbers of cycles and starting phase each day, were tracked about equally well. Tracking was apparently immediate and did not improve across sessions. Experiment 2, in which long and short series were presented on alternate days, showed that tracking on long was more impaired than on short. Experiment 3 showed that occasional presentation of a short IFI in a series of fixed, longer IFIs caused a reduction in waiting time in the next IFI. These effects are evidence for a fast-acting timing mechanism in which waiting time in the IFI N + 1 is strongly determined by the preceding IFI, N. Earlier IFIs have some cumulative effect, but the details remain to be elucidated.

Animals↗
PubMed1988

Typical delay determines waiting time on periodic-food schedules: Static and dynamic tests.

Pigeons and other animals soon learn to wait (pause) after food delivery on periodic-food schedules before resuming the food-rewarded response. Under most conditions the steady-state duration of the average waiting time, t, is a linear function of the typical interfood interval. We describe three experiments designed to explore the limits of this process. In all experiments, t was associated with one key color and the subsequent food delay, T, with another. In the first experiment, we compared the relation between t (waiting time) and T (food delay) under two conditions: when T was held constant, and when T was an inverse function of t. The pigeons could maximize the rate of food delivery under the first condition by setting t to a consistently short value; optimal behavior under the second condition required a linear relation with unit slope between t and T. Despite this difference in optimal policy, the pigeons in both cases showed the same linear relation, with slope less than one, between t and T. This result was confirmed in a second parametric experiment that added a third condition, in which T + t was held constant. Linear waiting appears to be an obligatory rule for pigeons. In a third experiment we arranged for a multiplicative relation between t and T (positive feedback), and produced either very short or very long waiting times as predicted by a quasi-dynamic model in which waiting time is strongly determined by the just-preceding food delay.

Journal Article↗
PubMed1979

Handwashing and antiseptic-containing soaps in hospital.

Two aspects of handwashing in hospital were considered. A study was carried out to examine the contamination of bar soap and containers, and the use of antiseptic soaps in reducing the resident flora of the skin. Swabs were collected from soap dishes on six wards and from a bacteriology laboratory on four consecutive days. The unmedicated bar soap was replaced by bar soap containing 2.5% povidone-iodine, and further swabs were collected over a period of seven days. Ninety-two isolates from 48 samples were obtained when unmedicated bar soap was used, and nine isolates from 42 samples when povidone-iodine (Betadine) soap was substituted. The number of organisms recovered when povidone-iodine soap was used was much reduced, and Pseudomonas spp were recovered in low numbers on only one occasion. Six laboratory workers took part in a study to compare bar soap with other agents-povidone-iodine soap, povidone-iodine surgical scrub, povidone-iodine alcoholic solution, chlorhexidine surgical scrub, and alcoholic chlorhexidine. Samples were collected after standard washes and after surgical gloves had been worn for 90 minutes. The effect of multiple washes was assessed by samples collected after six washes with the agent under study (three per day) followed by 90 minutes wearing surgical gloves. The average percentage reduction in normal flora obtained indicated that alcoholic chlorhexidine was superior to the other agents.

Anti-Infective Agents, Local↗