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PubMedDate not supplied

Parallel and sequential information processing in animals as a function of different hemispheres.

The procedure of motor-food conditioned reflexes in conjunction with unilateral decortication of the hemispheres by means of spreading depression was used in experiments on 53 rats. Differentiation of geometric figures, combined into simultaneous complexes or chain stimuli, presented simultaneously or sequentially, was developed. It was shown that lateralization of predominant disturbances of analysis depends not on the type of stimuli used, but on the nature of their presentation. In the case of simultaneous presentation, the most profound disturbances occurred after the right hemisphere was disconnected, and in the case of sequential presentation, as a result of inactivation of the left hemisphere. The presence of a simultaneous processor in the right hemisphere of the animals and a sequential processor in the left is suggested.

Animals↗
PubMed1981

A disturbance in the conceptual organization of actions in patients with ideational apraxia.

Patients with ideational apraxia (i.a.) performed significantly worse than patients without i.a. in a task where they had to arrange pictures in correct order illustrating actions requiring the use of various objects. There was no influence of severity of aphasia nor presence or severity of ideomotor apraxia. In two similar pictorial tasks, where consecutive stages of common events are illustrated, which, however, did not include manipulation of objects, there was no difference in performance of patients with and without i.a. It is concluded that i.a. is a disturbance in the conceptual organization of actions.

Adult↗
PubMed1994

Memory for spatial location as a function of temporal lag in rats: role of hippocampus and medial prefrontal cortex.

Rats with medial prefrontal cortex, hippocampus, or cortical control lesions were tested on an eight-arm radial maze task, in order to examine memory for the temporal order of spatial locations as a function of temporal lag. During the study phase of each trial, rats were allowed to visit each of eight arms once in an order that was randomly selected for that trial. The test phase required the rats to choose which of two arms occurred earlier in the sequence of arms visited during the study phase. The arms selected as test arms varied according to temporal lag (0-6) or the number of arms that occurred between the two test arms in the study phase. The control rats performed at chance at a temporal lag of zero, but their performance was above chance for the remaining lags, improving after the temporal lag exceeded zero. The hippocampal-lesioned rats showed a marked deficit, performing at chance for all lags, with some savings for those items occurring at the end of the list. The medial prefrontal cortex-lesioned rats showed a less severe deficit. The results of these data support the notion that both the hippocampus and the medial prefrontal cortex play significant roles in memory for the temporal order of spatial locations.

Animals↗
PubMed1990

Cognitive consequences of congenital deafness.

Comparing congenitally deaf children with hearing children on a variety of information processing tasks provides a natural test of the developmental consequences accompanying the long term loss of a particular sensory input. In this experiment, two sequential and two spatial tasks were used to evaluate the way deaf and hearing individuals process these different types of information. When deaf students were asked to recall the order of a string of lights, they performed as well as hearing students. Deaf students were at a significant disadvantage, however, when processing sequentially presented digits. Deaf students performed as well as hearing students on two complex, standardized spatial tasks. The loss of a major sensory modality had minimal effect on three of the four tasks investigated in the present study. Explanations for the single task with a performance differential are considered.

Adolescent↗
PubMed1984

Reproduction memory of two-event sequences in pigeons.

Six pigeons were trained to reproduce two-event sequences in an experiment that employed a discrete-trial procedure that required subjects to peck one of four possible sample sequences (left-left, left-right, right-right, right-left) signaled on a given trial by the successive illumination of response keys. Following a retention interval (0.1 to 30 seconds), a reinforcer was delivered if a subject reproduced the prior sample sequence during a test condition in which both left and right keys were illuminated. The pigeons readily reproduced the orders in which they had just seen and pecked two illuminated keys. Reproduction accuracy declined as the retention interval was increased. Homogeneous sequences (left-left, right-right) were reproduced with greater accuracy than heterogeneous sequences.

Animals↗
PubMed1984

A corpus callosal deficit in sequential analysis by schizophrenics.

This preliminary study evaluated interhemispheric (i.e., corpus callosal) information processing by chronic schizophrenic and normal subjects. In right-handed normals the left hemisphere has been reported to be superior in temporal sequential analysis. Consequently temporal information presented to the right hemisphere requires time to cross to the left hemisphere for analysis. Measurement of hemispheric laterality and corpus callosal transfer time were evaluated by a two-pulse temporal discrimination task. Two dot stimuli were presented with decreasing temporal separation during bilateral and unilateral conditions. Subjects were required to judge perceived simultaneity and nonsimultaneity of dot onset. The results indicate that left hemisphere function in chronic schizophrenic and normal controls is superior to the right hemisphere in temporal analysis. Corpus callosal transfer time was significantly slower for chronic schizophrenics than for normal controls.

Adult↗
PubMed1982

Hemispheric differences in split-brain monkeys learning sequential comparisons.

Twelve split-brain rhesus monkeys were tested for differences in the abilities of their two cerebral hemispheres to learn discriminations based on the comparison of sequentially-presented visual stimuli. Overall there was no generalized advantage for either the left or right hemisphere. There was, however, a significant correlation between each monkey's handedness and the hemisphere that learned more readily; the more proficient hemisphere tended to be contralateral to the preoperatively preferred hand. This result raises the possibility that handedness in monkeys may be more closely related to cognitive processing than is usually believed.

Animals↗
PubMed1993

Impaired temporal context memory on anterograde but not retrograde tests in the absence of frontal pathology.

This study examined the memory performance of patient RK who developed substantial memory impairments due to a hypothalamic glioma but in the absence of any evidence of frontal disturbance. RK was evaluated on both tests of anterograde and retrograde memory for temporal context. In the first experiment he exhibited marked deficits on a list discrimination task even when recognition performance was well within control range. Experiment 2 confirmed this disproportionate impairment of temporal order memory and showed that RK's list discrimination deficit was as severe as that found in alcoholic Wernicke-Korsakoff Syndrome patients. Experiment 3 showed that RK's temporal discrimination deficit was not a general deficit in discrimination because he performed normally on a spatial discrimination test of comparable difficulty to the temporal task. Experiment 4 examined RK's memory for deceased famous people and his ability to indicate the half decade in which they died. RK's performance was indistinguishable from controls whereas WKS patients were extremely impaired. This study adds to the view that frontal damage is not a necessary condition for impairment on anterograde measures of temporal context memory. However, further evidence from this study indicates that temporal judgments about pre-existing memories may depend on intact frontal lobe functioning.

Adult↗
PubMed1982

Dividing attention within and between hemispheres: testing a multiple resources approach to limited-capacity information processing.

Two experiments tested the limiting case of a multiple resources approach to resource allocation in information processing. In this framework, the left and right hemispheres are assumed to have separate, limited-capacity pools of undifferentiated resources that are not mutually accessible, so that tasks can overlap in their demand for these resources either completely, partially, or not at all. We tested all three degrees of overlap in demand for left hemisphere supplies, using dual-task methodology in which subjects were induced to pay different amounts of attention to each task. Experiment 1 compared complete and partial overlap by combining a verbal memory load with a task in which subjects named nonsense syllables briefly presented to either the left or right visual field (LVF and RVF, respectively). Experiment 2 compared complete versus no overlap by using the same verbal memory load combined with a laterally presented same-different judgment task that did not require a spoken response. Decrements from single-task performance were always more severe when the visual field task stimulus was presented to the RVF. Further, subjects in Experiment 1 were able to trade performance between tasks on both LVF and RVF trials because there was always at least some overlap in left hemisphere demand. In Experiment 2, performance trade-offs were observed on RVF (complete overlap) trials, but not on LVF trials, where no overlap in demand existed. These results contradict a single-capacity model, but they support the idea that the hemispheres' resource supplies are independent and have implications for both cerebral specialization and divided attention issues.

Attention↗
PubMed1987

Remembering and constructing an order.

The purpose of this study was to determine whether children who could recognize a linear order would be able to use this recognition to answer new questions about the linear order. Three-, 4-, 5-, and 6-year-old children were trained to choose a series over a nonseries, a series over a series ordered in the opposite direction, or one nonseries over another nonseries. They were also given a standard seriation task. Children could recognize a series before being able to construct one, but recognition of a series was not correlated with construction of a series. Although children did not use the linear order to construct a series, they could use it to make choices between two similar stimuli, only one of which contained a feature identical to the linear order. The comparison between seriation and recognition of one nonseries over another revealed that performance on these two tasks was correlated and that one common feature between them was systematicity, which occurred either in searching for relationships or constructing them.

Attention↗
PubMed1979

An experimental analysis of the effects of d-amphetamine and cocaine on the acquisition and performance of response chains in monkeys.

In one component of a multiple schedule of food presentation, monkeys acquired a different four-response chain each session by responding sequentially on three keys in the presence of four geometric forms (learning). In the other component, the four-response chain was the same each session (performance). Both d-amphetamine and cocaine, at the higher doses, disrupted the behavior in the learning component; the overall response rate decreased, the overall accuracy was impaired (i.e., percent errors increased), and there was less within-session error reduction. The performance component was generally less sensitive than the learning component to the disruptive effects of both drugs on rate and accuracy. After pre-feeding or during an extended session, the response rate decreased in both components, but accuracy was generally unaffected. When the four discriminative stimuli in both components were removed, the behavior was disrupted to a greater extent in the performance component. The disruptive effects of both drugs on behavior in the learning component were attenuated when the drugs were administered during the session after the response chain had been acquired. It was concluded that the greater sensitivity of the learning component to disruptive drug effects is related to the relatively weak stimulus control and/or the lower rate of reinforcement associated with that component.

Animals↗
PubMed1984

Dose-response analysis of the behavioral effects of diazepam: I. Learning and memory.

A total of 120 healthy volunteers were randomly assigned to four treatments (placebo, 0.1, 0.2, and 0.3 mg/kg) and three testing times (7 AM, 1 PM and 7 PM). Immediate and delayed free recall of word lists revealed consistent decreases in performance as oral diazepam dose increased from 0.1, 0.2, to 0.3 mg/kg. Paradoxically, as the dose increased, the number of predrug list words recalled also increased. A serial number-learning task displayed a pattern of delayed improvement of acquisition as the dose increased. Response times in a semantic-categories task were prolonged as the dose increased. Parallel recovery functions were observed for all doses and tasks. Full recovery after a single administration of 0.1, 0.2, and 0.3 mg/kg doses was estimated to occur after 3.5, 4.5, and 5.5 h, respectively. Several analyses were consistent with the view that acquisition and not retrieval was impaired by diazepam. There were no circadian interactions with the effects of the drug.

Adolescent↗
PubMed1992

Skill learning in the elderly: diminished implicit and explicit memory for a motor sequence.

Explicit and implicit memory for a cognitive-motor sequence was studied in elderly and young adults. Implicit memory was examined in a serial reaction-time paradigm in which sequences of hand postures repeated cyclically, then shifted to random sequences. Two control groups received random sequences throughout. Movement times (MTs) across the first 4 blocks did not improve more in the elderly-repeated than in the elderly-random group. In contrast, the young-repeated group showed greater improvement in MT across these blocks than the young-random group. MT was less affected in the elderly than in the young by shifts between repeated and random sequences, indicating impaired implicit memory. Explicit memory, which was assessed by free recall and cued recall, also was impaired in the elderly. Diminished implicit memory in the elderly could not be explained solely by the possible intrusion of conscious recollection strategies.

Adult↗
PubMed1990

Interference with visual short-term memory.

Working memory (Baddeley and Hitch 1974) incorporates the notion of a visuo-spatial sketch pad; a mechanism thought to be specialized for short-term storage of visuo-spatial material. However, the nature and characteristics of this hypothesized mechanism are as yet unclear. Two experiments are reported which examined selective interference in short-term visual memory. Experiment 1 contrasted recognition memory span for visual matrix patterns with that for visually presented letter sequences. These two span tasks were combined with concurrent arithmetic or a concurrent task which involved manipulation of visuo-spatial material. Results suggested that although there was a small, significant disruption by concurrent arithmetic of span for the matrix patterns, there was a substantially larger disruption of the letter span task. The converse was true for the secondary visuo-spatial task. Experiment 2 combined the span tasks with two established tasks developed by Brooks (1967). Span for matrix patterns was disrupted by a visuo-spatial task but not by a secondary verbal task. The converse was true for letter span. These results suggest that the impairment in short-term visual memory resulting from secondary arithmetic reflects a small general processing load, but that the selective interference due to mode of processing is by far the stronger effect. Results are interpreted as being entirely consistent with the notion of a specialized visuo-spatial mechanism in working memory.

Adult↗