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At least 973 records · Page 54Linked to original sources
PubMed1990

Do children with a specific reading disability have a general serial-ordering deficit?

Two experiments are described in which reading disabled subjects and their normal controls were tested for their ability to abstract sequential regularities from a noisy background. Subjects were presented with an adaptation of the repeated digits task of Hebb (1961) and its spatial analogue the Corsi Blocks (Milner, B. Br. Med. Bull. 27, 272-277, 1971). Normal subjects had a digit span significantly better than their block span and also significantly better than that of the disabled readers. This suggested that normal subjects have better defined "storage filters" for digits or a specific advantage in the construction of 'transitory filters' for verbal material. There were no differences between groups on block span. On the repeated digit sequences normal readers abstracted a relatively stable "storage filter" in the first five recurrent trials whereas the disabled readers showed no discrimination until the last five recurrent trials. On the repeated blocks task the disabled group performed as well as normal readers. Taken together this date gives strong evidence for a specific deficit in verbal serial organization in disabled readers but does not support a general deficit in serial organization.

Attention↗
PubMed1990

Subjective ordering, short-term memory, and the frontal lobes.

Four tasks relying on short-term retention, i.e. digit span, missing scan, randomization span, and pointing span were presented to patients with frontal-lobe lesions and normal controls. Digit span was considered a measure of passive short-term memory, the other three tasks additionally reflect comparing processes, and two of these, the randomization and pointing spans, also measure active ordering by the subject. The results confirmed Petrides and Milner's (Neuropsychologia 20, 249-262, 1982) hypothesis that frontal-lobe patients are typically deficient in subject-ordered tasks. It is also suggested that they are deficient in a spontaneous generation, rather than comparison component of subjective ordering.

Brain Neoplasms↗
PubMed1990

Digit span and visual neglect: a puzzling relationship.

Weinberg et al. found a relationship between the presence of extinction and the discrepancy between backward and forward digit span among left hemiplegic patients. The present study replicates this finding in a group of 37 patients suffering from unilateral left visual neglect, demonstrating a strong relationship between degree of neglect and digit span discrepancy. A principal components analysis of a neurospychological examination revealed three main independent components--Neglect, Verbal Memory and Non-verbal Memory respectively. Digit Span Discrepancy had one of the highest loadings on the neglect factor, and loaded significantly on no other factor. Multiple regression analysis showed that the relationship of Digit Span Discrepancy with Degree of Neglect exists independently of visuo-spatial ability, and this is also true for paced auditory serial addition (PASAT) scores for one of the two main indices of neglect. The implications of this for understanding neglect are discussed.

Attention↗
PubMed1990

Abduction, adduction and hand differences in simple and serial movements.

Abductive or adductive movements were made either towards single targets left or right of "home", or sequentially from target to target with various levels of advance information. In the former situation the preferred hand completed responses (movement time, MT) faster than the non-preferred, while the non-preferred hand initiated them faster (reaction time, RT); these effects were in both cases stronger with harder (knob turn) than with easier (touch) responses. Abductive responses (MTs, not RTs) were faster than adductive, especially with the preferred right hand. However in the sequential task adductive responses were the faster, consistently so by MTs, while with respect to time spent motionless at each target (down time, DT) more so with the non-preferred hand, and under conditions of maximal advance information. Findings were discussed in the contexts of movement complexity, hemispatial representation, and how advance information may be utilized in the resolution of directional uncertainty. There may be an evolutionary advantage in making complex manipulative responses adductively, close to the body, while reaches are usually made abductively, to the periphery of circumcorporeal space.

Adult↗
PubMed1991

Frontal-lobe contribution to recency judgements.

Three recency-discrimination tasks (involving concrete words, representational drawings and abstract paintings) were administered to 117 patients who had undergone unilateral cortical removals, and to 20 normal control subjects. Frontal or anterior temporal-lobe excision did not impair simple item recognition, and neither left nor right anterior-temporal lobectomy affected recency judgements on any task. In contrast, excisions that encroached on the mid-lateral frontal cortex impaired verbal recency judgements, the deficit being mild after right frontal lobectomy. Patients with right frontal-lobe removals showed the greatest impairment in recency discrimination on the two pictorial tests. The results provide evidence for hemispheric specialization related to the nature of the stimulus material and some support for a functional role for the left mid-lateral frontal cortex in verbal recency judgements.

Adolescent↗
PubMed1991

Hemispheric specialization for motor sequencing: abnormalities in levels of programming.

Left and right hemisphere stroke patients and control subjects performed sequences of hand postures which varied in complexity (repetitive and heterogeneous) and length (one to five). Performance in the hand ipsilateral to the stroke was compared to a control group using the same hand. Neither stroke group had problems preprogramming sequences prior to movement. The only deficit seen for the right hemisphere group was a greater difference in movement time (MT) between heterogeneous and repetitive sequences relative to controls, regardless of sequence length. This suggested right hemisphere damage results in subtle timing but not error deficits on more complex movements, perhaps due to increased external spatial demands. The left hemisphere group was slower to execute single postures, and had difficulty scheduling motor programs for repetitive and heterogeneous movements such that inter-response times (IRTs) were more affected by sequence length than for controls. Left hemisphere patients also made more errors on heterogeneous sequences as they increased in length, and the difference in MTs between repetitive and heterogeneous sequences increased more with increasing length relative to their control group. These results suggested the left hemisphere plays a role in controlling single postures, in scheduling motor programs during repetitive and heterogeneous movements, and in processes related to sequential ordering.

Aged↗
PubMed1992

Dichotic listening: what does it measure?

Auditory lateralization was investigated in 26 right-handed and 26 left-handed, normal subjects using seven different dichotic listening tests in each proband (free recall of digit lists, free recall of consonant-vowel (CV) syllables, four different CV syllable monitoring paradigms, and free recall of Morse codes). Reliabilities calculated with the formula of Spearman-Brown were low for digit recall (0.29, corrected for test length: 0.50), but good for CV recall (0.83), CV monitoring (0.75-0.88), and Morse code recall (0.50, corrected for test length: 0.88). Nevertheless, interest correlations were low, both for right- and left-handers (negative correlations ranging from -0.44 to -0.05, positive correlations ranging from 0.01 to 0.51). Only 38-77% of the right-handed and left-handed subjects retained one direction of ear advantage across any combination of two tests. The data suggest that different dichotic tests reveal different results. This may be due to psychometric, procedural, or phonetic properties. We conclude that individual predictions of language dominance are not justified using the dichotic tests evaluated in the present study.

Adult↗
PubMed1993

Short-term memory impairments in Alzheimer-type dementia: evidence for separable impairments of articulatory rehearsal and long-term memory.

Two experiments are described which investigate the short-term memory deficits found in Alzheimer-type dementia. In the first experiment memory span for words of differing spoken duration is related to speech rate. Memory span was lower in subjects suffering from Alzheimer-type dementia than for normal elderly controls but in both cases a linear function related recall to speech rate for items of differing spoken durations. The function for Alzheimer subjects had an equivalent slope (interpreted as reflecting a contribution from a sub-vocal rehearsal process) but a lower intercept (interpreted as reflecting a contribution from a long-term memory component). The second experiment investigated the effects of repeating supra-span lists of items in a serial recall task. As predicted the control subjects showed substantial increases in recall across trials associated with elevations of the speech rate/recall functions while the Alzheimer subjects showed very little benefit from repetition of the lists. We conclude that the verbal short-term memory deficit found in Alzheimer-type dementia has two components: a deficit in the rate of rehearsal and an impairment in the long-term memory component of short-term recall.

Aged↗
PubMed1994

Perseverative motor behaviour in Parkinson's disease.

Difficulties in shifting of cognitive sets and perseverative behaviour have been shown to be part of the neuropsychology of Parkinson's disease, possibly due to frontal dysfunction. We have tested perseverative motor behaviour by assessing ability to generate random movement sequences in 15 patients with Parkinson's disease using the Breidt Perseveration Test Device (PTD). In this experiment subjects are instructed to press one of nine buttons arranged randomly on a metal board without use of systematic or repetitive strategies. The speed of this task that comprises 150 consecutive presses is determined by an acoustic go-signal appearing at 1 Hz frequency. Results were compared with 14 age-matched controls. Patients performance was impaired with intrusion of unwanted systematic strategies suggesting a decreased ability of Parkinson patients to generate random movement sequences.

Adult↗
PubMed1994

Digit span performance and unilateral neglect.

This study tested the alternative hypotheses of Weinberg et al. (J. clin. Psychol. 28, 361, 1976) and Robertson (Neuropsychologia 28, 217-222, 1990) regarding the nature of dysfunctions underlying impaired backward digit span among patients with unilateral neglect. Results support the Weinberg et al. hypothesis that visual imagery plays a primary role in performance of Digits Backward. The findings also indicate a unilateral component to the Digits Backward task. Both neglecting and non-neglecting patients with high digit span discrepancy (DD) evidenced attentional bias to right space and a specific impairment in rotating objects in left space. Results were not consistent with Robertson's hypothesis that high DD arises from a general attentional deficit. In fact, patients with low DD evidence greatest impairment on tests of attention.

Attention↗
PubMed1994

Formation and lateralization of internal representations underlying motor commands during precision grip.

The capability to store and retrieve weight-related information from a lift to scale the force output during a subsequent lift was examined in 10 healthy adults and 50 children (age 2-10 years), as well as a 22-year-old patient with corpus callosum agenesis. Subjects lifted a test object between the thumb and index finger while the isometric fingertip forces were measured. The results suggest that both healthy children and adults can transfer weight-related information between the right and left hand, although a lateralization was found. Also, the storage and retrieval of weight-related information appears to be a dynamic process dependent on both previous sensory information and knowledge of future movements. Late maturation of interhemispheric connections and asymmetric loss of some information during the transfer between hemispheres suggest a lateralization of the internal representation. The patient with a corpus callosum agenesis supported this hypothesis.

Adolescent↗
PubMed1977

Aphagia, behavior sequencing and body weight set point following orbital frontal lesions in rats.

Discrete lesions were made in the orbital frontal neocortex of rats and eating, drinking, sensorimotor responsiveness, and sequencing of motor acts were studied. Duration of aphagia was related to palatability/texture of food. Rats were aphagic for a mean of two days to palatable cookie mash presented on a spatula, six days to a high fat diet mash presented in a 4 cm high dish and for seven days to dry laboratory food. Water drinking was resumed with injestion of dry food. Rats presurgically fattened to 120% of body weight appeared stuporous and akinetic for 2-3 postoperative days, and the period for acceptance of food in tall tests was protracted. Rats presurgically dieted to 80% of normal body weight did not show accelerated recovery of feeding. Preoperatively normal, fattened and dieted rats assumed a chronic postoperative body weight level 25% lower than control rats. Rats with lesions showed sensorimotor neglect when tested on an open table top, but did not show neglect when tested in their home cages. In grooming tests, rats with lesions showed all of the components of normal grooming, but failed to exhibit the long chains of grooming characteristics of control rats. They also showed attenuated tongue extension and had difficulty manipulating food with the forepaws. The experiments suggest that following orbital frontal lesions, motor impairments, motor sequencing dysfunctions, change in body weight set point, and depending upon the test situation, sensorimotor neglect, may all be contributing factors to aphagia. The orbital frontal cortex may influence feeding and other behaviors via descending neural projections to the hypothalamus and branistem.

Animals↗
PubMed1991

Caffeine and novelty: effects on electrodermal activity and performance.

Caffeine has been shown to affect both physiological functioning and certain aspects of performance. These effects are typically attributed to a simple increase in general arousal. The present study was based on the theory that the effects of caffeine are actually multidimensional. Specifically, we hypothesized that the drug raises arousal, acts to maintain elevated arousal under conditions otherwise conductive to habituation, and enhances the impact of situational and psychological sources of arousal. Subjects were given caffeine (300 mg) or placebo and white noise or no noise and exposed to a series of pure tones and two Backwards Recall Tasks, one novel, the other repetitive. Electrodermal activity (EDA) and task performance were recorded. Caffeine increased arousal as measured by EDA. It also acted to slow habituation during repetitive stimulation, thus maintaining heightened arousal. Finally, it enhanced the effects of novel stimulation, which also independently raised arousal. These results support a multidimensional theory of caffeine effects and provide some understanding of the popularity of caffeine as a psychotropic agent.

Acoustic Stimulation↗
PubMed1993

Encoding of a nonmonotonic serial pattern: role of the dorsal hippocampus and amygdala.

The present experiment examined the effects of lesions of the hippocampus, amygdala, or combined hippocampal + amygdala lesions on the acquisition of a presumably difficult serial pattern. Lesioned rats, sham-surgical and nonsurgical control rats were trained in a runway to track one of a four-element series of Noyes food pellets consisting of 14-0-3-7 pellets, respectively. Control rats were capable of tracking the elements of the series. Tracking developed in the amygdala-lesion group by the middle stages of training, but tracking did not develop in the hippocampal-lesion group until the end of training and failed to develop in the hippocampus + amygdala-lesion group. The results are discussed in terms of hippocampus and amygdala involvement in working memory processes. The role of each structure in processing the temporal and affective attributes of the task is considered. Presumably, the hippocampus is necessary for tasks requiring the sequential coding of information. The hippocampus appears to maintain a temporal record of the elements of the series providing the rat with the ability to track which stimulus elements have been presented and which have not. In addition, by processing the affective attributes of the task, the amygdala appears to mediate mnemonic processes.

Amygdala↗
PubMed1993

Effects of caffeine and gender on physiology and performance: further tests of a biobehavioral model.

The present study extended testing of our biobehavioral model describing the effects of arousal and caffeine to include an examination of gender differences and their interactions with habitual and acute caffeine ingestion. Males and females selected as high or low habitual caffeine users were randomly assigned to receive either caffeine or a placebo and exposed to novel and repetitive recall tasks and to simple auditory stimuli. Electrodermal activity and recall task performance were recorded. The four major factors examined, including habitual caffeine use, acute ingestion, gender, and stimulus novelty, affected behavior, physiology, or both. Results showed that habitual caffeine usage systematically affected tonic arousal (skin conductance level) and improved recall task performance. Acute caffeine ingestion increased phasic arousal (skin conductance response amplitude) and reduced habituation rates. Gender interacted with other factors to significantly affect both tonic and phasic arousal, and females performed better than males on the recall tasks. These results were partially supportive of the theoretical model, and further work is needed to examine the interactions of acute and chronic caffeine intake with gender and novelty.

Adult↗
PubMed1992

Effects of atipamezole, an alpha 2-adrenoceptor antagonist, on the performance of rats in a five-choice serial reaction time task.

The present study investigates whether pharmacological activation of the noradrenergic system improves attention. The effects of atipamezole, a potent alpha 2-adrenoceptor antagonist, on the performance of adult male rats in the five-choice serial reaction time task were studied. Before drug testings, food-deprived rats were trained to detect and respond to brief flashes of light presented randomly by the computer in one of five spatially diverse locations until a stable level of performance had been reached (about 3 months). Single-dose administration of atipamezole (0.03-3.0 mg/kg) slightly increased the number of premature and perseverative responses during the intertrial interval and slightly decreased the reaction times to incorrect responses, indicating increased behavioral activation. Atipamezole did not affect discriminative accuracy. However, in a subpopulation of rats with the poorest discriminative accuracy according to pretest performance seven of eight rats improved their discriminative accuracy when treated with 0.3 mg/kg atipamezole as compared to controls. At the other doses tested, no improvement was found. The present results suggest that acute administration of atipamezole, and alpha 2-adrenoceptor antagonist, slightly increases behavioral activation, although the effects on baseline performance in the task measuring selective attention are modest.

Adrenergic alpha-Antagonists↗