Donald R. Meyer

Discrete-Trial Training Techniques and Stimulus Variables

Publisher Summary This chapter presents the factors known to govern the efficiency with which the nonhuman primates learn in situations that involve a trial-by-trial approach. The variables of interest are the nature of the cues, their modes of presentation to the subject, and the spatiotemporal relations of cues to responses and rewards. There now is a most substantial body of research related to this group of variables, and it has been shown that very powerful effects can be produced by their manipulation. The chapter also presents methods that involve the use of discriminanda and presents experiments in which the visual cues are of a fairly complex nature.

One experience with ‘lower’ or ‘higher’ intensity stressors, respectively enhances or diminishes responsiveness to haloperidol weeks later: implications for understanding drug variability

This laboratory has previously shown that acute exposure to a variety of brief stressful events can have a very long-lasting influence on subsequent responsiveness to pharmacological and non-pharmacological stressors. In some cases the response to these agents is enhanced, while in others it is diminished: the common denominator being that in each instance the influence of the initial stressor grows stronger with the passage of time. Here, we identify one factor that determines which time-dependent effect is manifest. In 3 separate experiments, male rats were subjected to a single exposure to stressors of either lower or higher intensity and their effects on haloperidol-induced catalepsy and dopamine and dihydroxyphenylacetic acid levels in the nucleus accumbens and medial frontal cortex, measured either 1-2 h or 2 weeks later. The stressors were either environmental (needle jab or 1 h of immobilization), metabolic (200 or 750 mg/kg, i.p. of 2-deoxy-D-glucose), or no effect on haloperidol-induced catalepsy when stressors preceded such behavioral testing by 1-2 h. By contrast, when the interval was 2 weeks, the lower-intensity stressors all increased haloperidol catalepsy, whereas the higher-intensity stressors decreased the same response. In other words, a process that progressed with the passage of time was observed regardless of whether sensitization or diminution of haloperidols action occurred. In contrast to the uniform bipolar behavioral effects observed, depending on the intensity of the prestressor, the neurochemical findings failed to show any evidence of bipolarity whatever.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics and bases of recoveries of functions after injuries to the cerebral cortex

A review of the principal results of a 20-year program, at Ohio State University, of quantitative studies of the problem of recovery from damage to the brain.

The septal social cohesiveness effect: Its robustness and main determinants ☆

Abstract Rats prepared with lesions of the forebrain septum and placed within an open field exhibit strong tendencies to maintain contacts with each other. The expressed doubts of other workers notwithstanding, the effect is robust and enduring, as is shown by an experiment with one pair of rats and a review of past experiments. Moreover, although septal rats are fearful when alone within a field, they will actively approach cats or rabbits, which suggests that the effect is primarily a function of release of the contact-comfort motive.

Effects of occipital neocortical lesions upon visual discriminations in the cat

Abstract Cats were trained on flux, equal-contour-pattern, unequal-contour-pattern and visual cliff discriminations. The stimuli used in the pattern discriminations either increased or decreased in the number of intersections. Subsequently, the animals were subjected to surgery with the intent to remove the neocortex from the lateral, posterolateral, suprasylvian, suprasplenial and splenial gyri. Postoperatively, all cats relearned the flux, visual cliff and unequal-contour-pattern discriminations. The most medial portions of area 17 were spared in these animals. Two of the cats also relearned the equal-contour-pattern discriminations. Different but additional sparing was noted in area 19. The results in terms of varying the number of intersections were equivocal.

Residual spatial vision of cats with lesions of the visual cortex

Abstract Cats were trained on three classes of visual discriminations. The first was a large-checks vs small-checks problem in which the stimulus panels varied both in the total amount of contour and the number of enclosed spatial figures. The second class was a contour problem in which the number of objects per panel was constant, but the amount of contour was greater in one panel than in the other. The third class was a numerosity problem in which the stimuli contained more objects in one panel than the other, but the amount of contour was the same for both panels. The discriminanda in all three classes were equated for flux and were designed to eliminate local flux and local contour differences as cues for solving the discrimination. Normal cats learned all three classes of problems and subsequently sustained removals of the visual neocortex. Postoperatively, the animals discriminated flux-equated stimuli that varied with respect to both contour and numerosity. However, when flux and contour were equated, the cats never exceeded chance performance after nearly a year of retraining on the numerosity problem. These results, together with previous findings, indicated that the animals were form-blind despite their abilities to learn some classes of flux-equated visual pattern tasks. After completion of the learning phase of the experiment, visual placing was studied in these animals. With very few exceptions, placing was absent after postoperative recovery periods of more than 1 year, but could be reinstated for periods up to three weeks following a single injection of d -amphetamine. Hence, although visually-decorticated cats fail to learn form discriminations, they nonetheless are able, if appropriately treated, to localize surfaces in space.

Approach-avoidance conflict in preweanling rats: A developmental study

Ten- and 15-day-old rat pups were trained with two procedures to approach an anesthetized mother, and then were punished for approaching. Both ages of subjects exhibited increased latencies to reapproach the mother, indicating passive inhibitions, but only the older pups retreated. All but one of the younger pups eventually reached the mother within 3 min after the punishment, while only half of the older pups did so. In a second experiment examining the development of locomotor avoidance reactions, 5- to 20-day-old rats were shocked without the mother present. Fifteen- and 20-day-old rats significantly decreased their activity patterns in reaction to shock and spent significantly less time in the shock area than either of the younger aged pups. These results suggest that flight reactions are components of a rat’s defensive repertoire that appear very rapidly between 10 and 15 days of age.

Visual form perception is a function of the visual cortex

Rats prepared with serial visual-cortical ablations can relearn the horizontal-vertical stripes discrimination problem if given interoperative training. However, they fail to discriminate between obliquely oriented stripes. The findings are discussed in relation to the concept that pattern perception is completely dependent upon the integrity of cortically related systems. Furthermore, the criteria for constructing pattern discriminanda are outlined, and reasons are presented for abandoning some of the classical stimuli used to test form perception in striate-extra-striate preparations.

Effects of simultaneous septal-visual, septal-anterior and anterior-posterior lesions upon relearning a black-white discrimination

Summary Rats were trained on a black-white discrimination task, and then were assigned to one of the following groups: (1) normal control S s; (2) S s with septal lesions; (3) S s with anterior neocortical ablations; (4) S s with visual neocortical ablations; (5) S s with anterior and visual neocortical ablations; (6) S s with anterior neocortical and septal lesions; (7) S s with visual neocortical and septal lesions. Following a 21 day recovery interval all S s were tested for retention of the black-white habit. Deficits of varying magnitude occured in operated groups. Data from the normal septal, anterior and visual groups replicated previous studies. S s with anterior neocortical and septal lesions behaved like S s with anterior neocortical lesions. S s with anterior and visual neocortical ablations and S s with visual neocortical and septal lesions relearned at about the same rate. The results suggested that the anterior neocortex and septal area might be components of the same system.

Memory, Remembering, and Amnesia

Memories, and particularly long-term memories, are the basic ingredients of knowledge. Hence it is important that we ask where their traces, or engrams, are stored within the brain, and also that we understand the possible fates of the engrams while they are in storage. Moreover, inasmuch as knowledge is worthless if it cannot be expressed, it is equally important that we understand the variables that govern the remembering of memories.