Paul Ellen

Hippocampal lesions and spontaneous alternation behavior in the rat

Abstract Rats with hippocampal lesions and control animals were tested for spontaneous alternation behavior in a modified T-maze under three different stimulus conditions. When intra-maze stimuli (alley brightness) and spatial direction could be used simultaneously as cues for alternation, both groups alternated at rates significantly higher than chance. However, when intra-maze stimuli were opposed to spatial direction cues, the rats with hippocampal lesions alternated at chance levels while the controls continued to alternate spatial direction. The complexity of the phenomenon of spontaneous alternation itself and the locus and extent of the lesions employed were discussed as possible sources of the discrepancy between the results of this study and others investigating the role of hippocampus in spontaneous alternation behavior.

External cue control of DRL performance in rats with septal lesions

Abstract Septally-lesioned, thalamically-lesioned, and normal animals were trained to bar-press on a DRL-20 schedule for food reinforcement. For half of the animals, a cue light signalled the end of the required delay during the first half of training. The light cue conditions were reversed for all animals in the last half of training. All animals decreased their rate of response during training, regardless of the presence or absence of the cue light. However, the septal animals, in contrast to the normal and thalamic animals, increased their reinforcement frequency only when the cue light was used. In addition, when the cue light was used, all animals had a bimodal distribution of inter-response times, with one mode at the shortest recorded delay and a mode at the 20-sec delay interval. When the cue light was not used, the thalamic and normal animals again had a bimodal distribution, while the septal animals had a unimodal distribution with the mode located at the shortest recorded delays. The results suggested that the cue light functioned as a discriminative cue for bar-pressing and secondly, as a reinforcing stimulus for behaviors which mediated the required delay. It was concluded that the septal deficit on DRL schedules results from a failure to utilize response-produced, proprioceptive stimuli as cues for bar-pressing.

Problem solving in the rat: Stay vs. shift solutions on the three-table task

Two experiments were conducted to determine the conditions under which a shift problem vs. a stay problem would be easier for animals tested on Maier’s three-table task. When animals were given a prior exploratory experience and a partial feeding during the feeding experience, the stay problem was easier. With a prior exploratory experience and a complete feeding experience, the shift solution was easier. In the absence of prior exploration, rats cannot solve either the stay or shift problem, regardless of the amount of feeding during the feeding experience.

Problem solving in the rat: Piecemeal acquisition of cognitive maps

The purpose of this experiment was to compare the problem-solving performance of rats allowed to explore either one or two tables of Maier’s three-table-problem apparatus on successive days. The feeding experience and test trial were administered on the day after all tables and runways had been explored in this piecemeal fashion. No rat that explored only one table and runway per day was able to solve the problem, whereas 60% of the rats that explored two tables and their interconnecting runways did solve the problem. All rats that explored the entire apparatus on each exploratory day were able to solve the problem. These data support the notion that animals can conceptually link objects experienced successively into cognitive representations which specify the constant relationships existing between those objects. The existence of such an absolute spatial mechanism makes it unnecessary for an organism to depend upon relative spatial mechanisms such as routes or cues.

Spatial problem solving by rats: Exploration and cognitive maps☆

Abstract Two experiments were performed in an attempt to examine the contribution of the exploratory experience to performance on Maiers 3-table spatial problem-solving task. In the first experiment, the runway configurations were altered between exploration and testing. It was found that following an initial impairment animals exposed to the altered runway configurations could perform as well as animals not confronted with an altered runway configuration on the test trial. In the second experiment, animals were allowed to explore only elements of the problem space. Exploration of either the runways only or the tables only led to unsuccessful performance on the 3-table task. The results of both experiments were related to current theory of cognitive mapping.

Problem solving in the rat: Septal lesion effects on habituation and perseverative tendencies

The performance deficit that typically occurs on Maier’s three-table spatial integration task following septal damage was examined with the view towards relating it to lesion-induced alterations in exploratory activity during the exploration phase of the task. Septals, unlike shams, failed to habituate (i.e., reduce the rate of sector entry behavior) during the 15-min exploration period. However, this failure to habituate was not the sole basis of the septal deficit on the spatial integration aspect of the task, since some animals that did habituate also failed to adopt the spatial solution. Unlike shams, septals tended to perseverate a turning response, not only on each of the three daily test trials, but also from day to day. This perseverative tendency was unresponsive to its consequences. Since the perseverative tendency did not correlate with any response bias expressed during the exploration phase of the task, it was regarded as the septal animal’s adaptation to the test trial situation.

Current Issues The place of Physiological Psychology in Neuroscience

The development of Neuroscience has raised questions about the place of Physiological Psychology in both Psychology and Neuroscience. The present paper addresses the identity crisis of Physiological Psychology by focusing on the concept of the localization of function in the explanation of brain-behavior relationships. The physiological psychologist, dependent upon the reductionistic assumption that behavior can be explained by reduction to some brain event, and the notion that we have a firm understanding of behavioral events and processes, has turned to Neuroscience for both academic identity and research sustenance. But Neuroscience lacks a molar framework, and the consequence of the flight into Neuroscience has been the deterrence of integrative theorizing about brain-behavior relationships. Only through a return to the basic intellectual tradition of our discipline can we negate this trend. By attempting to identify and understand the natural fracture lines of complex adaptive behavioral functions, physiological psychologists can begin to develop the integrative theories that will foster an understanding of brain-behavioral relationships. Doing so has significant implications for what we teach, as well as for the role we play in the Psychology-Neuroscience endeavor of the future.

Absence of temporal discrimination following septal lesions

Septally lesioned and normal rats were trained on a DRL 20 schedule, utilizing an IBM-1800 data acquisition and control system to program the reinforcement contingency and record responses. Normal animals developed a temporal discrimination (as measured by the IRTs/opportunity statistic), while septals did not. Training did not lead to any change in the frequency of reinforcements obtained by either group. These results were discussed in terms of differences in the locus of stimulation (i.e., internal or external) controlling performance.

Spatial Problem Solving in a Dual Runway Task by Normal and Septal Rats

The addition of a dual runway configuration did not disrupt the successful performance of normal animals, nor did it improve the deficit of septal rats on the Maier three-table spatial integration task. Both groups of animals displayed a preference for the outside runway configuration during exploration. During testing, however, septal animals retained this preference, whereas normal subjects attempted solution by using the inside runway configuration. This fact, in addition to the apparent lack of a habituation pattern during exploration, suggests that septal animals do not acquire a spatial representation of the test situation. It is suggested that the inability of septal rats in spatial situations is due to an inability to form rather than an inability to use spatial maps.

Cholinergic blockade effects on spatial integration versus cue discrimination performance.

A within-subjects investigation was conducted to determine the effects of central versus peripheral cholinergic blockade in animals tested either on a spatial integration task in which the possibility of rule learning was also available or on a visual discrimination task in which the daily location of food was marked by a distinctive visual stimulus pattern. All testing was conducted on the Maier three-table apparatus. It was found that the only effect of the peripheral cholinergic blockade on the performance of either task group was to produce a decrease in exploratory behavior. In contrast, central cholinergic blockade markedly impaired spatial integration performance; however, it did not impair the ability of animals in rule learning or visual discrimination learning. It was also found that central cholinergic blockade impaired the animals tendency to enter all tables before reentering a given table during the exploratory phase of the daily session. This finding was interpreted as reflecting an impairment of working memory for spatial information, rather than a general impairment in working memory, and this interpretation was applied to the explanation of the deficit in the spatial integration performance.