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PubMed1989

A behavioral quantal theory of brain function: an alternative to Lashley's continuity theory of mass action.

A behavioral quantal theory of brain function is formulated on the basis of a newly discovered step-wise relationship invariably present among the findings of three experiments by Tsai, et al. on the effects of (1) cerebral decortication, (2) cranial x-radiation, as well as (3) insulin, metrazol, and electroconvulsive shocks upon white rats' adaptive behavior during their learning of successive habit reversals and one-trial reversal problems. Confirmatory results from earlier investigators who studied effects of various current strengths of ECS upon learning and retention of various maze habits are also cited in support of the behavioral quantal theory of brain function which is proposed here as a close-up, more refined alternative to Lashley's continuity theory of mass action.

Animals↗
PubMed2002

Effect of excitotoxic lesions of rat medial prefrontal cortex on spatial memory.

The involvement of medial prefrontal cortex (mPFC) in spatial learning was examined in two memory tasks using spatial components, the Morris water maze and the three-panel runway. Using the Morris water maze task, with an invisible platform, the effects of NMDA mPFC lesions were assessed in a procedure reflecting spatial learning and memory, including a spatial reversal. In the three-panel runway, a delayed matching-to-position procedure was used in which rats were required to find food at the end of the runway after passing through one of three panel gates set into four barriers spaced equally apart along the maze. In addition, mPFC lesions were assessed behaviorally in two behavioral tests known to be sensitive to mPFC dysfunction: the food hoarding paradigm and spontaneous locomotion in the open field. Consistent with the documented effects of mPFC damage, NMDA mPFC lesions impaired food hoarding behavior and increased spontaneous exploratory locomotion. In the Morris water maze and the three-panel runway, mPFC-lesioned rats showed relatively few effects, supporting the conclusion that the damage inflicted to the mPFC had no consequence for the processing of spatial information. However, mPFC lesioned animals showed slower acquisition during both the training trial in the three-panel runway and the reversal training in the Morris water maze. These results suggest that spatial memory did not depend on mPFC integrity in the Morris water maze and the three-panel runway experiments, and address the issue of deficits induced by mPFC lesions in memory tasks dependent on non-mnemonic processes such as attentional processes and/or a reduced behavioral flexibility to environmental changes.

Animals↗
PubMed1980

Reversal of paradoxical sleep deprivation by amygdaloid stimulation during learning.

Rats were subjected to a partial, selective paradoxical sleep (PS) deprivation. Two groups were trained in a shuttle avoidance task, one receiving posttraining amygdaloid stimulations (AS). A third group received AS, but was not trained. Levels of PS in the AS trained group were higher than in the AS non-trained controls, while the reverse was true for the slow wave sleep (SWS) measure. Both AS groups had levels of PS and SWS superior to the non-AS trained rats. In a second experiment, a group of normally rested AS animals was trained in the same task with a non-AS control group. These groups did not differ in terms of learning performance. Results were believed to support the hypothesis of a close relationship between sleep and learning.

Amygdala↗
PubMed1975

Hyperstriatal function in the pigeon: response inhibition or response shift?

Experiment 1 showed that pigeons with lesions of the anterior or posterior hyperstriatum were impaired relative to unoperated controls and to control operates having neostriatal lesions on both acquisition and reversal of a simultaneous position discrimination. The observation that hyperstriatal birds showed more tendency than controls to halt responding altogether in this situation cast doubt on the notion that the reversal deficit was due to a loss of response inhibition. A second experiment supported an alternative hypothesis, that hyperstriatal birds have a deficit in the ability to shift responding to an alternative stimulus as a consequence of nonreinforcement.

Animals↗
PubMed1968

Stimulus function in simultaneous discrimination.

In discrimination learning, the negativity of the stimulus correlated with nonreinforcement (S-) declines after 100 training trials while the stimulus correlated with reinforcement (S+) is paradoxically more positive with lesser amounts of discrimination training. Training subjects on two simultaneous discrimination tasks revealed a within-subjects overlearning reversal effect, where a more-frequently presented discrimination problem was better learned in reversal than was a discrimination problem presented less frequently during training.

Animals↗
PubMed1965

LATERAL HYPOTHALAMIC STIMULATION IN SATIATED RATS: T-MAZE LEARNING FOR FOOD.

It is well known that electrical stimulation in portions of the lateral hypothalamic area is positively reinforcing and induces eating in satiated rats. We have found that continuous stimulation of this kind can also motivate satiated and previously untrained rats to learn the location of food in a T-maze. Efficient acquisition and reversal of discriminations for food indicate that lateral hypothalamic stimulation exerts motivational effects which are functionally equivalent to those of food deprivation.

Brain↗
PubMed2001

Olfactory discrimination conditioning in the moth Spodoptera littoralis.

We used a proboscis extension reflex (PER) to study the olfactory discrimination capability in the moth Spodoptera littoralis. Already after a single experience, moths were capable to discriminate a rewarded from an unrewarded odor. In the first experiment, when rewarded and unrewarded odors were substituted for each other, moths were able to undergo reversal conditioning already after two experiences. Both shorter and longer inter-trial intervals (ITIs) supported high degrees of learning. In a second experiment, moths could solve both feature-positive and -negative discrimination tasks. Two hypotheses for the way in which these associations exert their discrimination performance are considered. The moth's olfactory physiology has been extensively studied. This animal thus provides a powerful system in which to study the neurobiology of olfactory discrimination and odor recognition.

Animals↗
PubMedDate not supplied

Vasopressin and vasotocin facilitate reversal of a brightness discrimination.

Male albino rats received vasopressin, vasotocin, pressinoic acid or placebo and were tested on an aversively motivated brightness discrimination task. Treatment with both vasopressin and vasotocin had no effect on acquisition but facilitated the reversal of the discrimination. Pressinoic acid had an inconsistent effect. The results are interpreted to show that the C terminal of the peptides vasopressin and vasotocin influence potency of these peptides. Furthermore, the results are interpreted as showing that both vasotocin and vasopressin influence selective attention during aversively motivated tasks.

Animals↗
PubMed1990

Reversible inactivation of the medial septum differentially affects two forms of learning in rats.

The contribution of the medial septum to different aspects of spatial information processing was assessed by examining the effects of reversible septal inactivation on radial maze performance of rats. In addition, the selectivity with which the medial septum affects learning was studied by testing the effects of septal inactivation on the acquisition of non-spatial information. Rats were first trained according to a spatial working memory procedure that included a 30-min delay between the first 4 (forced) choices and subsequent test (free) choices. The forced choices comprised the sample phase of the experiment while the free choices comprised the test phase. Saline or tetracaine (a local anesthetic) was injected into the medial septal area either before the sample phase, after the sample phase (i.e. at the beginning of the delay period), or just before the test phase. In contrast to the saline injections, tetracaine injected just before the sample or test phases produced a significant increase in errors at test. Tetracaine injection at the beginning of the delay period did not affect test choice accuracy. EEG records showed that septal inactivation drastically, yet temporarily, reduced the hippocampal theta rhythm. Thus, when septal inactivation occurred either before the sample phase or at the beginning of the delay period, hippocampal theta recovered by the time of the test phase. Septal inactivation also produced a significant retardation of learning on a non-spatial reference memory task, although clear improvement over trials did occur. Moreover, the results of subsequent saline injections suggest that at least some of the performance deficit was due to variables other than learning per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1981

Quality of learning of severely retarded adolescents.

A modified discrimination-reversal task identical to that used by Rumbaugh (1971) was employed to assess the quality of learning of severely retarded adolescents. Subjects initially were trained to criterion on a series of multi-dimensional object-discrimination problems (A+B-). Subsequent to one reversal trial on each problem (A-B+), one of three postreversal conditions was introduced: (a) a standard discrimination-reversal condition (A-B+), (b) a condition that substituted a novel stimulus for A (B+C-), or (c) a condition that replaced B with a novel stimulus (A-C+). Subjects' performance on the modified discrimination-reversal task was the same level for all three conditions. In comparison to earlier findings with nonhuman primates, results were interpreted as indicative of mediational learning processes.

Adolescent↗
PubMed2001

Reversibility of n-3 fatty acid deficiency-induced alterations of learning behavior in the rat: level of n-6 fatty acids as another critical factor.

Rats fed a semipurified diet supplemented with 3% (w/w) safflower oil [Saf, n-3 fatty acid deficient, high linoleic acid (18:2n-6)] through two generations exhibit decreased correct response ratios in a brightness-discrimination learning test compared with rats fed 3% perilla oil [Per, high alpha-linolenic acid (18:3n-3)]. This is associated with a decreased DHA (22:6n-3)-to-arachidonic acid (20:4n-6) ratio in brain lipids. In the first set of experiments, dietary oil was shifted from Saf to a mixture of 2.4% safflower oil plus 0.6% DHA after weaning (Saf-DHA), but all parameters measured in the learning test were essentially unchanged. Brain 22:6n-3 content of the Saf-DHA group reached that of the Per group but the levels of 20:4n-6 and docosatetraenoic acid (22:4n-6) did not decrease to those of the Per group at the start of the test. In the second set of experiments, dietary oil was shifted to a mixture of 0.6% safflower oil plus 1.2% oleic acid (OA) plus 1.2% DHA (Saf-OA-DHA group) with 18:2n-6 content comparable to that of the Per group. The Saf-OA-DHA group exhibited a learning performance similar to that of the Per group; brain 22:6n-3, 20:4n-6, and 22:4n-6 contents were also comparable to those of the Per group. These results indicate that the altered learning behavior associated with a long-term n-3 fatty acid deficiency is reversed by supplementing 22:6n-3 after weaning, when the levels of competing n-6 fatty acids in the diet and brain lipids are limited.

Aging↗
PubMed1990

Visual impairments in macaques following inferior temporal lesions are exacerbated selectively by additional damage to superior temporal sulcus.

The present study examined the behavioural effects of removing the inferior temporal cortex (area TE) either on its own or in combination with the adjacent fundus and upper bank of the superior temporal sulcus (area STP). Comparisons with preoperative behaviour showed that the addition of superior temporal sulcal damage led to an increase in visual components of the Klüver-Bucy syndrome, i.e. an increased tendency to touch and examine objects coupled with a decrease in emotional reactivity, but no excessive orality, changes in food preference, or coprophagia. No group differences were found in the learning of 3 pattern discriminations, but the animals with additional superior temporal sulcal lesions were more impaired than the others on 3 colour discriminations, successive reversals of an object discrimination, and a learning-set task. These findings indicate that STP provides an important route, independent of the route via TE, by which visual information can reach limbic structures to evoke affective responses and contribute to visual learning.

Amygdala↗
PubMed1969

Learning in fish with transplanted brain tissue.

Material taken from fish embryos during gastrulation was implanted at prospective tectal sites in host embryos of the same age and species. When mature, the hosts were trained in a series of habit reversals. Two of six animals showed progressive improvement in reversal (a phenomenon not typically found in fish, but characteristic of higher animals), two showed unusually few errors, and two behaved normally. Differences in performance were correlated with differences brain structure.

Animals↗
PubMed1990

Behavioral effects of MK-801 in the rat.

Several experiments were conducted to study the effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, on learning and memory in the rat. Rats displayed impaired performance on several sensorimotor tests and appeared grossly intoxicated when treated IP with 0.2 mg/kg MK-801, but not when treated with lower doses (0.05 or 0.1 mg/kg). Postacquisition performance on two spatial learning tasks involving working memory protocols (reinforced alternation and radial arm maze) was impaired by MK-801 at intoxicating doses (greater than or equal to 0.2 mg/kg) but not at lower doses (0.05 or 0.1 mg/kg). Using a position habit reversal task, we found that rats could learn to reverse a position habit while under the influence of a nonintoxicating dose of MK-801 (0.1 mg/kg), but when tested on the following day performed as if they did not recall what they had learned. Thus, acute administration of a nonintoxicating dose of MK-801 disrupts the retention of new information learned under the influence of the drug but does not interfere with the performance of tasks that are well learned before the drug is administered. Whether the performance deficits on the spatial learning tasks observed only following intoxicating doses of MK-801 reflect an effect on memory is not clear.

Animals↗