Biomedical subjects

Matthew C Bell

Publications and source records attributed to Matthew C Bell.

3 recordsLinked to original sources

PubMed2006

Effect of signaling reinforcement on resistance to change in a multiple schedule.

This study evaluated the effect of a signal on resistance to change using a multiple schedule of reinforcement. Experiment 1 presented pigeons with three schedules: a signaled delay to reinforcement schedule (a two-link chain schedule with a variable-interval 120-s initial link followed by a 5-s fixed-time schedule), an unsignaled delay schedule (a comparable two-link tandem schedule), and an immediate, zero-delay variable-interval 125-s schedule. Two separate disruption procedures assessed resistance to change: extinction and adding a variable-time 20-s schedule of reinforcement to the inter-component interval. Resistance to change tests were conducted twice, once with the signal stimulus (the terminal link of the chain schedule) present and once with it absent. Results from both disruption procedures showed that signal absence reduced resistance to change for the pre-signal stimulus. In probe choice tests subjects strongly preferred the signal stimulus over the unsignaled stimulus and exhibited no reliable preference when given a choice between the signal stimulus and immediate stimulus. Experiment 2 presented two equal signaled schedules where, during resistance to change tests, the signal remained for one schedule and was removed for the second. Resistance to change was consistently lower when the signal was absent.

Animals↗

PubMed2006

Memory and perseveration on a win-stay, lose-shift task in rats exposed neonatally to alcohol.

OBJECTIVE: It is important to understand the relationship between perseverative responding resulting from perinatal exposure to alcohol and potential underlying causes, including attention, memory, or response-inhibition problems. The present study was designed to examine the relationship between perseveration and memory. METHOD: Rats exposed neonatally to 6 g/kg/day alcohol from postnatal day (PD) 4 through PD 9 using an artificial rearing technique (n = 8) were compared with an artificially reared gastrostomy control group (n = 8) and a suckle control group (n = 8). Activity levels were assessed from PD 18-21. Beginning on PD 45, subjects were deprived of food and responded for food on a two-lever win-stay, lose-shift task in which reinforcement probability was a function of reinforcement delivery on the previous trial. If reinforcement was delivered, only a response on the same lever (stay) was reinforced. If reinforcement was not delivered, only a response on the opposite lever (shift) was reinforced. Effective responding depended on subjects remembering whether a reinforcer was delivered on the preceding trial. The intertrial interval varied across conditions (5 seconds or 60 seconds). RESULTS: Alcohol-exposed rats showed increased activity during activity testing but did not differ from controls on win-stay, lose-shift accuracy. All groups showed a performance decrease at longer intertrial intervals. Alcohol-exposed rats showed increased lever pressing during the intertrial interval compared with suckle control rats but not with gastrostomy control rats. CONCLUSIONS: Choice behavior was comparable for all groups on the win-stay, lose-shift task, indicating that memory, as assessed by this task, was not differentially affected by alcohol exposure. Alcohol-exposed rats responded more during the intertrial interval compared with suckle controls, suggesting increased activity without increased response inhibition. The win-stay, lose-shift procedure is a potentially useful tool for separating simple activity level effects, memory-related effects, and response-inhibition effects. This study also highlights the need for additional research describing the relationship between perseverative responding and underlying mechanisms.

Animals↗

PubMed2002

Preference and resistance to change in concurrent variable-interval schedules.

Pigeons were trained on a multiple schedule in which separate concurrent schedules were presented in the two components of the schedule. During one component, concurrent variable-interval 40-sec variable-interval 80-sec schedules operated. In the second component, concurrent variable-interval 40-sec variable-interval 20-sec schedules operated. After stable baseline performance was obtained in both components, extinction probe choice tests were presented to assess preference between the variable-interval 40-sec schedules from the two components. The variable-interval 40-sec schedule paired with the variable-interval 80-sec schedule was preferred over the variable-interval 40-sec schedule paired with the variable-interval 20-sec schedule. The subjects were also exposed to several resistance-to-change manipulations: (1) prefeeding prior to the experimental session, (2) a free-food schedule added to timeout periods separating components, and (3) extinction. The results indicated that preference and resistance to change do not necessarily covary.

Animals↗