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At least 91 records · Page 5Linked to original sources
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↗