Peter J. Livesey

Enrichment-isolation, cortex length and the rank order effect

In a previous paper we have proposed a developmental theory to account for the neurological changes which result from differntially rearing animals in either enrichment or isolation. On the basis of brain weight measurements we suggested that the primary cause of the differential development could be traced to retarded neurological growth in the isolated animals. The present 9 studies test the generality of this theory by applying it to the cortex length changes induced in rats by differential rearing periods of between 18 and 160 days. In the light of this new data the theory has been revised to the extent that the developmental ceiling for the dependent variable is now considered to change with age instead of being fixed. Two major consequences of this revision are as follows. Firstly that the environmentally induced changes in cortical development are seen as persistent. Secondly that the Rank Order Effect is shown to be transitory phenomenon which exists only when some, but not all of the isolate values have been restricted in their development.

Environmental Enrichment Influences Survival Rate and Enhances Exploration and Learning But Produces Variable Responses to the Radial Maze in Old Rats

Wistar rats at 7 (mature), 16 (aging), and 22 (old) months of age spent 70 days in normal laboratory (Social), impoverished (Isolated) or dynamic Enrichment cages. The Enriched cage emphasized spatial re-arrangements of significant items, and the learning of new routes. Subsequently, Enriched rats at all ages entered a novel environment and escaped from a bright light with significantly shorter latencies than rats from either of the other environments. Mature, aging and some of the old Enriched rats also significantly outperformed their Isolated and Social counterparts in the radial maze. However old Enriched and Isolated animals showed significant variability in relation to the measure of the proportion reaching criterion on this task, and a significantly lower proportion than of old Social rats reached criterion. Enriched rats had a significantly higher survival rate than Social and Isolated animals. These findings are discussed in terms of learning efficiency and behaviors that conserve energy and thereby enhance survival.

Spontaneous alternation in the white rat: A learning/memory phenomenon

Spontaneous alternation of naive and of experienced rats was examined under various conditions, namely (i) intertrial intervals (ITIs) between trial 1 (T1) and trial 2 (T2) of 50 sec. 50 min and 5 hr; (ii) confinement during the ITI either in the goal box of the arm chosen on T1 or in a separate familiar container; (iii) trail and place cues available from T1 to T2 either totally removed, partially removed, or left intact. The latency of response (time from start box to goal box) on T2 was also considered. Results supported a learning/memory hypothesis for spontaneous alternation with memory of location of the arm explored on T1 being the critical factor in determining the direction of turn on T2. It appears that, as long as the rat has access to cues that indicate that it entered a particular arm on T1, it will turn to the alternate arm on T2.

The rat, rabbit and cat in the hebb‐williams closed field test of animal intelligence

Abstract Eight rats, ten rabbits and eight cats were tested in a form of the Hebb-Williams Closed Field Test. Two scoring methods, “error score” and “excess square entry score,” were employed. Resu...

Wheel running, A rewarding activity for the rat or response to increased drive following deprivation

Abstract Wheel running in the rat may be due to a specific activity drive or to increased activation arising from other drive states or both. Experiment 1 confirmed that rats satiated for food and water run spontaneously in the activity wheel and revealed that, under combined food and water deprivation, they run more actively than under either food or water deprivation or in a nondeprived state. Experiment 2 examined the reward properties of wheel running for satiated rats compared with animals both food and water deprived. Satiated animals learned the correct response in a T maze more rapidly than deprived animals when this meant access to an activity wheel. They also learned two position reversals and extinguished their response when denied access to the wheel.

AUTOMATED APPARATUS FOR THE STUDY OF LEARNING IN MONKEY AND RAT1

Abstract Automated apparatus for the study of learning in animals is desirable for various reasons yet attempts to develop such apparatus have met with variable success. In Experiment 1, 14 mature female Rhesus monkeys learned a 4 response double alternation sequence, 7 in a semi automatic WGTA and 7 in an automated two lever apparatus (ATLA) designed to give contiguity between bar-press and presentation of reward. Animals in the ATLA learned as efficiently as those in the WGTA. When animals were able to trigger the onset of each new sequence they performed significantly better than animals working with a 30 sec. delay between sequences. Incorporating the findings from this study with those from work on automated equipment for simultaneous visual discrimination learning with monkeys, an automated discrimination apparatus for rats was developed. Nine rats working in this equipment learned a simultaneous brightness discrimination task in 120-260 trials.

The rabbit and cat in the delayed alternation problem

Seven rabbits and seven cats were trained in a single alternation sequential task with minimum delay. Delay was then introduced between trials through 10-sec., 15-sec., 20-sec. and 30-sec. delay periods. Five rabbits and six cats attained criterion performance at all delay levels. On the delayed alternation trials, in contrast to alternation with minimum delay, cats learned the task significantly more rapidly than did rabbits. This result was in the anticipated direction.

Cue Significance Learning From Differentially Reinforced Prior Exposure to Shape Stimuli, in Albino and Brown Rats

Effects of prior exposure to shape stimuli on learning of a circle/triangle discrimination task were examined in three experiments. The prior exposure given was either differentially reinforced (one of the two shapes associated with food) or nondifferentially reinforced (both shapes associated with food), with exposure given either in a similar or in a different environment (context) to the discrimination task.In Experiment 1 albino rats were given 30-day prior exposure from age 28 days in a “same context” situation. Differentially reinforced exposure to circle/triangle or to rhombus/oval shapes enhanced learning of the discrimination task compared with controls, while nondifferentially reinforced exposure produced no significant change. In Experiment 2, Part A, brown rats given 30-day same environment differentially reinforced exposure to circle and triangle showed significantly enhanced learning of the discrimination task, but “different environment” exposure had no effect on learning. In Part B, same environment, nondifferentially reinforced exposure had no effect on task learning, but different environment exposure resulted in significant enhancement of learning. In Experiment 3 brown and albino rats were compared on discrimination performance following 15-day differentially reinforced prior exposure in the same environment to circle and triangle shapes. Although there was no difference in discrimination learning for the respective control groups, the pigmented differentially reinforced group showed significantly more enhancement of discrimination learning than did the albino differentially reinforced group. This finding appeared to be related to behavioral differences recorded during prior exposure which indicated that the albino group learned less than the pigmented group about the cue reinforcement relationship.

The Hebb‐Williams elevated pathway test: A comparative study of rat, rabbit and cat performance1

The objectives of this study were to compare the performance of 3 species on the Hebb-Williams Elevated Pathway Test (EPT) and to compare their EPT performance with that on the Closed Field Test (CFT). Results were considered in terms of overall performance and difficulty order of test problems. As with the CFT, the EPT did not differentiate, in terms of overall performance, between rats and rabbits. Cats performed significantly more efficiently than either rats or rabbits. The order of difficulty of problems was found to be consistent within species but differed rather markedly between species. Correlations between the two tests were found to be high and significant for rats and rabbits but not for cats.

Early rearing conditions and within-group behavioral variability

Rats were maintained in enriched or isolated conditions for periods ranging from 10 to 51 days postweaning in four experiments. Animals were subsequently run in a simple maze in acquisition and extinction trials. A measure of variability, the coefficient of variation, showed a tendency for enriched groups to be more homogeneous in their performance, especially after 30 days differential rearing, a finding analogous to some of those in the differential rearing-brain changes literature. Some additional material suggests that these findings may have some generality.