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PubMed1988

Representation of serial order in monkeys (Cebus apella).

Cebus monkeys were trained on a five-item serial learning task, symbolized as ABCDE; the initial stages of training were on the shorter subseries AB, ABC, and ABCD. To assess the monkeys' knowledge of the sequential position of each item, pair-wise tests were given to 2 subjects after acquisition of the ABCD series and to 4 subjects after reaching criterion on the ABCDE series. In both tests, the monkeys performed at high levels on the interior pairs, which were BC for the ABCD series, and BC, BD, and CD for the ABCDE series. These results, as well as the orderly relations observed in the pair-wise tests between first-item response latency and first-item position and between second-item response latency and number of missing items, indicated that the monkeys had developed a well-organized internal representation of the four- and five-item series. Although pigeons are also capable of learning four-item and five-item series, they apparently do not develop a comparable representational structure. The disparity between the monkeys' and pigeons' representational competence for serial order is predictable from the difference in their capacities for associative transitivity.

Animals↗

PubMed1977

The effect of cyclandelate in depressed and demented patients: a controlled study in psychogeriatric patients.

In a double-blind clinical trial the effects of the vasodilator drug cyclandelate (in a dose of 1200 mg daily) were studied in a group of patients with depressive illnesses or dementing conditions. The measures used before treatment and after six weeks' treatment were: clinical rating, psychometric tests (Paired Associate Learning Test, Digit Copying Test, Digit Substitution Test, and Serial Learning Test), cortical evoked potentials, the sedation threshold and the Gresham Questionnaire. In the depressive group there were no significant differences in the changes in scores at six weeks in three groups: those who received cyclandelate plus amitriptyline, those who received placebo plus amitriptyline, and those who received neither placebo nor cyclandelate. In the demented group there were significant changes in favour of the placebo on two measures (Digit Copying test, and one component of the auditory evoked response). The results do not support the previously reported views claiming, in a number of studies, a significant improvement in the performance of both demented and normal elderly subjects treated with cyclandelate. The significance of these findings is discussed.

Aged↗

PubMed1992

A double-blind comparison of the effects of temazepam and triazolam on residual, daytime performance in elderly insomniacs.

Benzodiazepine hypnotic medications are widely prescribed for elderly patients, but there is a paucity of information available concerning the residual cognitive and psychomotor (the morning-after) effects of these drugs. We compared two commonly used hypnotics--temazepam and triazolam--in a double-blind, placebo-controlled, single-dose study with community-dwelling healthy elderly with a DSM-III-R diagnosis of primary insomnia. Forty-five subjects over the age of 65 (mean age 72.23, SD = 4.44) qualified for the study. Subjects were randomly assigned to one of five treatment groups (placebo, triazolam 0.125 mg., triazolam 0.25 mg., temazepam 15 mg., and temazepam 30 mg.). Neuropsychological testing was completed at baseline and 12-14 hours after the dosing. Patients were evaluated with a variety of tests that measured attention, concentration, motor speed, immediate memory, and learning of new information. Separate repeated measured analyses of variance were performed to assess the significant changes among the five treatment groups. We found improved performance or no change in all the measures for all medication groups except for impairment of performance on a serial learning task for both high-dose medication groups. The significance of these results and the need for further research in elderly insomniacs is discussed.

Aged↗

PubMed1991

Serial spatial reversal learning in rats: comparison of instrumental and automaintenance procedures.

Serial reversals of a spatial discrimination were trained in rats under automaintenance conditions, in which food reward occurred regardless of responding. This automaintained reversal learning was compared to instrumental reversal learning in other rats trained under a similar procedure which required responding for reward. In the automaintenance (AU) procedure, rats received food after every retraction of a "positive" response lever (S+); retraction of a second, "neutral" lever (So) was not paired with food delivery. Responses to the S+ were elicited at fairly constant rates during daily 100-trial conditioning sessions. Responses to the So occurred early in each session but rapidly diminished across trials. When the valences of the levers were reversed, responding shifted to the new S+ and diminished on the new So. Criterion for reversal was defined as a discrimination ratio (DR) of at least 90% responding to the S+ in two consecutive 10-trial blocks. With repeated reversals, acquisition of criterion performance occurred with increasing rapidity, reaching an asymptote below that required for the original discrimination. A second group of rats was trained on a similar instrumental schedule, in which at least one response to the S+ was required for food delivery. Response rates in this instrumental (IN) group were approximately double those of the AU group. However, ratios of S+ to So response rates were similar to those of the AU group, and the serial reversal curves generated were qualitatively similar. Thus rats can show improvement across serial reversals of a spatial discrimination based entirely on pairings of stimulus events (automaintenance), in a manner similar to that observed in instrumental procedures, in which reward is contingent upon correct responding.

Animals↗

PubMed1988

Behavioral deficits after intrahippocampal fetal septal grafts in rats with selective fimbria-fornix lesions.

Fetal septal transplants have been shown to promote behavioral recovery in young adult rats with aspiration fimbria-fornix lesions, rats with septal lesions and in intact aged rats. The present study examined the behavioral impact of intrahippocampal septal cell suspension transplants (T) in young female rats that had received, 10 days earlier, either medial fimbria lesions (Group FI.T), dorsal (subcallosal) fornix lesions (Group FO.T) or these two lesions together (Group FIFO.T). Relative to rats with lesions only (groups FI, FO and FIFO), grafted rats, irrespective of lesion locus, displayed unexpected impairments in (i) a serial alternation learning task, 5 weeks and 6 months after transplantation, and (ii) in a radial maze, 7 months after transplantation. In the first alternation test, Group FIFO showed impaired performance relative to Groups FI, FO and the sham-operated controls (Group S). In the second alternation test, Groups FO.T and FO showed impaired performance relative to Groups FI.T and FI, and only the performance of Group FI did not differ from that of Group S. In the radial maze, Groups FI, FO and FIFO all showed impaired performance relative to Group S. By contrast, there were no deleterious effects of lesions or of grafts in the acquisition and retention of a step-through passive avoidance task, 10 weeks after transplantation. Our findings on the effects of selective fimbria-fornix lesions did not confirm the report that rats with FI lesions but not those with FO lesions are unable to learn a serial alternation task, nor the report that FO lesions impair passive avoidance retention. Acetylcholinesterase (AChE) histochemistry revealed that grafts were present but graft-derived innervation of the host hippocampus varied from extensive to almost non-existent in all transplant groups. AChE-positivity in the dorsal hippocampus (DH) was not related to behavioral performance. However, the grafts often grew to a considerable size within the host brain and in many rats, especially those in Group FI.T, produced moderate to extreme damage of the host DH. There was a significant positive correlation between errors in the radial maze and graft-induced DH damage but no relationship between errors and graft size. The results indicate that, after partial lesions of the fimbria-fornix, intrahippocampal septal grafts survive well but are likely to damage recipient structures and result in behavioral impairments.

Acetylcholinesterase↗

PubMed1988

The effect of R 58 735 (Sabeluzole) on memory functions in healthy elderly volunteers.

The effects of chronic treatment (5 mg b.i.d. for 2 days followed by 10 mg b.i.d. for 5 days) with R 58 735 on human memory functions were studied in healthy elderly (age greater than or equal to 50 years) volunteers in a double-blind placebo-controlled study. Serial learning of nonsense syllables was better under R 58 735, and relearning 1 week after termination of the treatment was superior to relearning of similar material initially learned under placebo. Free recall of nonsense syllables was significantly better when these were learned under active compound. Proactive inhibition induced by consecutive presentation of word lists was attenuated by R 58 735. Short-term memory functions, retrieval accuracy from semantic memory and unprepared reaction times were unchanged. R 58 735 ameliorated both learning and recall in conditions of age-related mild hypofunction in healthy volunteers. The compound seems to have had positive effects on encoding and consolidation of new material.

Cognition↗

PubMed1990

Impaired verbal reasoning and constructional apraxia in subjects with right hemisphere damage.

In addition to causing visuospatial deficits, damage to the right cerebral hemisphere also impairs other cognitive abilities, including those requiring higher-order aspects of language. The present study used a standardized test battery to examine the relationship between visuospatial abilities and comprehension of narrative material in subjects having unilateral right hemisphere damage (RHD). In a series of 41 consecutively admitted RHD subjects, impairments in abstracting information from narrative passages were as prevalent and as severe in magnitude as constructional apraxia. Moreover, the extent of the visuospatial and linguistic impairments were highly correlated. Although age, educational levels, and degree of premorbid brain atrophy were all found to influence performance, analysis of a select subgroup of the population established that the covariation of visuospatial and verbal impairments is related to right hemisphere damage per se. Clinically, these findings may be of significance for understanding the pervasive cognitive impairments that are often evidenced by RHD patients.

Aged↗

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↗

PubMed1979

Differential effects of age and cerebral atrophy upon span of immediate recall and paired-associate learning in older patients suspected of dementia.

Seventy-eight patients suspected of dementia, 50 years of age or older and without evidence of focal cerebral lesion or systemic illness, were administered the Digit-Span Forward and Paired-Associate Learning subtests of the Wechsler Memory Scale. Computerized axial tomography, allowing a visualization and measurement of the lateral ventricles and cortical sulci, was employed to measure cerebral atrophy. Four groups were defined as follows: (1) age 50-69, without atrophy (N = 27), (2) age 50-69, with atrophy (N = 17), (3) age 70-89, without atrophy (N = 18), (4) age 70-89, with atrophy (N = 16). Results of analyses of variance indicate that Digit-Span is affected by cerebral atrophy but not by age, while Paired-Associate Learning is affected by both age and cerebral atrophy. No interaction effect between age and cerebral atrophy was found for either task. These results are discussed within the context of previous research, and implications for both models of memory and theories of the effects of cerebral atrophy in different ag groups are suggested.

Age Factors↗

PubMed1991

The effects of excitotoxic lesions of the nucleus accumbens on a matching to position task.

The effects of bilateral ibotenic acid lesions of the nucleus accumbens in the rat were examined on a delayed matching to position task. The lesion induced a stable delay-dependent performance deficit suggestive of a short-term memory problem. Following analysis of the impaired performance on trials with long delays, using measures akin to signal detection indices, the deficit was interpreted as being largely due to the intrusion of a side-dependent response bias. Low-dose amphetamine (0.75 mg/kg) produced a similar disruption in the sham-operated rats, both in terms of accuracy impairment and degree of strategical bias. As well as mimicking the effects of low-dose amphetamine in sham-operated rats, the lesion also protected against the disruptive effects of the drug at low doses. Whilst exhibiting no performance deficit when the matching schedule lacked a delay component, the lesioned rats were very significantly impaired in switching their response strategies when exposed to a series of reversals. In addition, the lesioned rats were remarkably resistant to an extinction procedure. Both these findings indicate that the lesioned rats were unable to exhibit flexibility in their response patterns. These results, taken together with those of the delayed matching procedure, imply that one of the functions of the intact nucleus accumbens is to inhibit habitual responding under conditions of non-reward and low stimulus control, possibly via its connections to the dorsal striatal system.

Amphetamine↗

PubMed1987

The effects of visual conspicuousness and the concept of randomness on the recognition of randomness in sequences.

In a number of studies, tendencies toward nonrepetition in judgments of randomness of visually presented sequences of events have been attributed to a biased concept of randomness. The present study proposed that such bias is due to "bottom-up" visual processes rather than a concept of randomness. Experiment 1 showed that judgments of randomness were less biased when repetitions were made less conspicuous by increasing the distance between adjacent items. Experiment 2 produced comparable results for increasing dissimilarity of categorically identical items. A third experiment showed that the bias in the judgment task was not related to a more direct measure of knowledge of random processes, the assignment of probabilities of repetition to imagined random sequences. The results supported the view that judgments of randomness are determined to a high degree by the conspicuousness of repetitions and are independent of the concept of randomness.

Attention↗

PubMed1991

Substitutability between conditioned and primary reinforcers in discrimination acquisition.

Rats and pigeons were trained on a series of reversals of a conditional simultaneous discrimination. The percentage of reinforcement for correct trials was varied across reversals. When nonreinforced correct trials produced the same feedback as incorrect trials, the number of errors to reach an acquisition criterion was greater for smaller percentages of reinforcement, but the number of reinforcers required was either approximately constant or smaller for the smaller percentages. When a stimulus paired with food (the conditioned reinforcer) was added on nonreinforced correct trials, both measures were substantially decreased. When the same stimulus was presented, but without a history of food pairing, learning rate was similar to when no stimulus was presented on nonreinforced trials. The results provide direct evidence that conditioned reinforcers may substitute, although imperfectly, for a primary reinforcer, and that pairing with the primary reinforcer is a necessary condition for such substitutability to occur.

Animals↗

PubMed1990

Differential importance of hierarchical learning, abstractness, and imagery.

This research examined the relative contribution of hierarchical sequencing, abstractness, and imagery to learning. In the past, hierarchical, logical sequencing was not shown to be superior to other modes of instruction, and the interaction of imagery, abstractness, and sequencing had not been examined, especially regarding the possible superiority of any of these as a contributor to learning. The data were produced by 108 high school students who studied sequences of hierarchically related information arranged in a 2 x 2 x 2 factorial design the dimensions of which varied according to the degree of imagery (high and low), abstractness (abstract and concrete), and type of sequencing (logical and scrambled). Analyses of the amount of learning under these conditions showed that hierarchical sequencing is not only relevant to learning but more related than either imagery or the abstractness of material to be learned. Additional suggestions are made regarding instruction and research especially in relation to matrix rather than hierarchial arrangements of information.

Attention↗

PubMed1988

Cortical function in elderly non-insulin dependent diabetic patients. Behavioral and electrophysiologic studies.

Neurobehavioral and electrophysiologic studies were carried out to determine the effect of diabetes mellitus on cognitive function in subjects over the age of 60 years. Forty-three non-insulin-dependent diabetic men were compared with 41 male nondiabetic age-matched controls. The diabetic patients were significantly inferior to the control group in the serial learning task and Benton's Visual Retention Test. The digit span test showed no difference between the groups. Electroencephalogram (EEG)-frequency-band analysis revealed slowing over the central cortex and reduction of alpha activity over the parietal area in diabetic patients. Acute hyperglycemia induced in healthy volunteers with the administration of 50 g of intravenous glucose did not have any effect on the dominant EEG rhythms. The checkerboard elicited P100 wave did not reveal a significant increase in latency nor were the P300 wave latencies significantly different in diabetic patients. However, a trend toward longer latencies in diabetics was evident at Fz and Cz recording sites. Acute hyperglycemia in healthy volunteers did not alter the P300 wave component. The results indicate that elderly type 2 diabetic patients have an impairment in retrieval of recently learned material with preservation of auditory attention and immediate recall. The EEG data suggest that there may be some central neural pathologic condition associated with diabetes.

Adult↗

PubMed1978

Operativity and reversibility in children's understanding of pictorial sequences.

The role of reversibility in children's comprehension and memory for sequences of pictures was investigated. Bidirectionality in the ability to remember and infer antecedents and consequences was assessed. Preschoolers were significantly more accurate at identifying consequences of portrayed events than the antecedents. Kindergartners and older children correctly identified beginnings and endings of sequences with equal proficiency. This developmental shift from relatively unidirectional to reversible comprehension was observed both on trials involving figurative memory and operative inference judgments.

Child↗

PubMedDate not supplied

Effect of prenatal heat stress on brain growth and serial discrimination reversal learning in the guinea pig.

Exposure of pregnant guinea pigs to an environmental temperature of 42 degrees C for 1 hr daily on Days 20-24 of gestation resulted in a significant reduction in the birthweight and brainweight of newborn offspring. These deficits persisted to early maturity and were still evident at 250 days of age following behavioral testing. Although some degree of postnatal neurogenesis and brain growth had occurred, this was not sufficient to compensate for the retarding influence of prenatal hyperthermia. Heat stress was also observed to seriously impair learning performance on the original discrimination task and this tendency persisted over the subsequent 4 reversals for both initial and perseverative errors. Impaired learning performance was related to reduction in brainweight. Animals with lower brainweights made significantly more initial, perseverative and total number of errors over the 5 problems. In addition, 12 of the 14 behaviorally tested stressed progeny had brainweights that were at least 2 standard deviations below the mean of the controls and as a result were classified as micrencephalic. Although heat stressed animals showed a significant reduction in the number of amacrine synapses in the inner plexiform layer of the retina, performance differences were not atrributed to changes in synaptic organisation of the retinal circuitry or to visual or other ophthalmic defects, but brain function. Animals with higher mean maternal poststressing core temperatures gave birth to progeny which had smaller whole and part wet-brainweights. Examination of the effect of poststressing core temperature on brainweight revealed that brain growth, independent of bodyweight, was retarded when this temperature elevated above 41.5 degrees C. This represented a rise of approximately 2.1 degrees C above normal and for each 1 degree C rise above this temperature, brainweight was reduced by 0.4227 g of the control value. Analysis of the atmospheric content of the incubator during stressing sessions ruled out the possibility that changes in level of oxygen and carbon dioxide may have contributed to the retarding influence on fetal development and learning ability in the guinea pig.

Animals↗

PubMed1990

Further evidence of the intricacy of memory span.

Memory span was measured for lists of verbal items constructed such that the items in the first half of the list were of one category and those of the second half were of another. In Experiment 1, the lists consisted of digits and words (e.g., 2, 8, 7, horse, cow, sheep or horse, cow, sheep, 2, 8, 7); in Experiment 2, they consisted of words from the same semantic domain and words from different semantic domains; in Experiments 3 and 4, they consisted of words that rhymed and words that did not rhyme. A category-order effect occurred in each experiment: Span was larger when the digits, same-domain words, or rhyming words occurred in the first half of the list than when they occurred in the second half. These findings suggest that memory span is more complex than is generally assumed.

Adult↗

PubMed1989

Repeated acquisition of behavioral chains: response sequences or conditional discriminations?

The purpose of this study was to determine whether pigeons learn a sequence of positional responses or a series of conditional discriminations under a repeated-acquisition-of-behavioral-chains procedure. Three pigeons were trained under a repeated-acquisition procedure in which three different key colors served as stimuli correlated with the three steps in a chain. The order of presentation of the three stimuli was altered during the latter part of each test session after acquisition had occurred. If the pigeons had acquired a response sequence, the pattern of responding should remain the same as in the initial portion of the test session. However, if the pigeons had acquired a conditional discrimination, the response pattern should change in accordance with the changed order of the key colors. Although the results of this study do not rule out the possibility that the subjects acquired, to some degree, a response sequence, the results suggest that the behavior of pigeons under a repeated-acquisition-of-behavioral-chains procedure is controlled primarily by conditional discriminative stimuli.

Animals↗