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PubMed1975

Verbal and non-verbal short-term memory impairment following hemispheric damage.

Short-term memory was investigated in 30 control and 125 unilaterally brain-damaged patients with a series of tests requiring the immediate reproduction of strings of items of increasing length. In three tests the items were auditorially presented digits or words: one test asked for oral repetition of digits, while the other two required the patient to point to written digits or to pictures. The fourth test aimed at measuring spatial span. On both the Digits Forward test and the two other verbal tests not requiring the use of speech, left brain-damaged patients were impaired in comparison to normals, while the right brain-damaged patients were not. Aphasics had a significantly shorter verbal span than non-aphasic patients with left hemisphere damage. Spatial span, on the other hand, was significantly affected by a lesion posteriorly located in either hemisphere, but not by aphasia. Two patients with an exceedingly poor verbal memory span were observed, one suffering from anomic aphasia and the other from conduction aphasia. There were also two right hemisphere damaged patients who showed an extreme reduction of spatial span, which could not be accounted for by space perceptual disorders and contrasted with a normal performance on a spatial long-term memory test.

Adult↗
PubMed1982

Oculomotor disturbances in Balint's syndrome: anatomoclinical findings and electrooculographic analysis in a case.

A 67-year-old man had repeated cerebral ischemic attacks, which resulted in a clinical picture combining paralysis of visual fixation, optic ataxia and impairment of visuospatial orientation, consistent with the definition of Balint's syndrome. Postmortem examination showed multiple lesions involving the occipital cortex of both sides and the white matter underlying the right insular cortex. EOG recording demonstrated a marked impairment of refixation saccades and saccades on verbal command. Smooth pursuit movements were completely abolished. Visual fixation was randomly achieved after many erratic exploratory movements and steadily maintained on the target (spasmodic fixation). During spasmodic fixation, EOG recording detected an ocular flicker resulting in a continuous instability of eye position. It is suggested that these findings may all be accounted for by the loss of panoramic vision due to a bilateral impairment of cortical areas 18 and 19.

Aged↗
PubMed2000

Weighing the evidence for cross over in neglect.

When patients with left-sided neglect are asked to bisect horizontal lines, they tend to place their marks to the right of the line's objective mid-point. However, when asked to bisect short lines they are either more accurate or paradoxically cross over and place their marks to the left of the objective mid-point. Previous explanations of the cross over phenomenon have considered specific aberrations of spatial attention. However, these explanations make no predictions about judgments of non-spatial stimuli. Two patients with right brain damage were asked to judge weights placed on both hands simultaneously. They were biased in reporting weights on the right as being heavier than those on the left. This rightward bias changed with lighter pairs of weights presented in the context of equal reference weights. In one patient the directional bias was eliminated and in the other the bias was reversed so that she was more likely to report the left weight as heavier than the right. These data suggest that a phenomenon analogous to cross over in line bisections also occurs with judgments of non-spatial stimuli. Representations of stimuli appear to be influenced by features of the stimuli encountered on-line and by memory traces of similar stimuli encountered previously. With an attentional deficit, memory traces influence the magnitude of the representation derived on-line disproportionately.

Aged↗
PubMed2001

Disruption of estimation of body-scaled aperture width in Hemiparkinson's disease.

A group of patients with left-sided symptoms of Parkinson's disease (LPD) was compared with a group of patients with right-sided symptoms (RPD) and with a group of healthy age-matched controls on body-scaled judgements of aperture width. Participants judged whether or not they would fit through a life-sized schematic doorway shown on a large screen. A staircase technique was used to find the door width for which 50% of the judgements were positive. The ratio between this measure and the width of the participant's body at the shoulders (the aperture to shoulder - A/S ratio) was calculated. The A/S ratio was approximately 1.5 in the LPD group, approximately 0.9 in the RPD group, and approximately 1.1 in the control group, suggesting that the visual representation of the doorway (or that of its relationship to perceived body-size) is compressed in LPD (and perhaps expanded in RPD). The A/S ratios were invariant with viewing distance (0.6 or 1.5 m), the contrast polarity of the display (white on dark, or vice versa) and the doorway surround (blank, or vertical or horizontal stripes). The findings are discussed with reference to the neural representation of external space and of the body, and to the motor problems of Parkinson's disease.

Aged↗
PubMed1999

Two-dimensional distortion of space representation in unilateral neglect: perceptual and response-related factors.

The paper reports the results of an experiment in which left-neglect patients were required to point at the location they judged vertically to correspond (within the frame of the visual stimulus display they were given) with a cue that was variably located along a left-right axis lying proximally or distally with respect to the left-right axis over which they had to give their response. Patients were found to make rightward errors as in a similar, single-case study. The significant positive correlation between those errors and the degree of response bias on a manual-response version of the Milner Landmark Task suggests that rightward pointing errors made by left-neglect patients in conditions such as those set in the present experiment are due to a dysfunction selectively affecting an output-related component of space representation.

Aged↗
PubMed2001

Attention induced motion blindness.

Recent studies have shown evidence for modulation of cortical activity by attention in visual areas involved in motion processing. Behavioural effects of this modulation have only been reported for high-order, but not for luminance-based motion. We show that attentional load can even affect the perception of a first-order motion inducing a short-termed motion blindness. The detection of transient coherent motion embedded in a rapid serial visual presentation was severely impaired if colour features were to be processed simultaneously. The findings reported here show attentional requirements can affect motion perception. This effect can not be explained by motion adaptation or priming and may instead arise from the suppression of irrelevant stimuli.

Analysis of Variance↗
PubMed2002

Learning disability subtypes: classification of high functioning hyperlexia.

This study examined 30 children with hyperlexic reading patterns and average intelligence to determine if established learning disability subtypes could be applied to these children with hyperlexia. Two groups emerged. One type showed language learning disorder patterns with good visual memory. This group also showed a high percentage of phonetic word errors. A second hyperlexic group showed signs of nonverbal learning disorder with visual spatial deficits and impaired visual memory. This latter subgroup showed few phonetic errors with more sight word errors. These findings suggest subtypes of high functioning hyperlexia, one showing language deficits characteristic of dysphasia and one showing patterns similar to visual spatial dyslexia.

Adolescent↗
PubMed1998

A bedside test to determine motion stereopsis using the Pulfrich phenomenon.

OBJECTIVE: Many diseases induce asymmetric delays in the visual pathway, resulting in a spontaneous Pulfrich phenomenon (PP). The PP is a visual stereoillusion that may cause difficulties in persons when traveling in cars, crossing the road, or playing ball games. The authors developed and tested a simple new bedside procedure to detect PP. DESIGN: A case series. PARTICIPANTS: Disease simulation in 2 normal subjects and 18 patients with optic neuritis (ON) was examined. Ninety normal subjects were studied to determine normal range of PP. INTERVENTION: The new test, called swinging pen test (SPT), is performed by oscillating a pen by hand. The SPT was compared to a gold standard, a mechanical pendulum (MP). MAIN OUTCOME MEASURES: The authors measured simulated PP in two normal subjects and PP in 18 patients with ON and 90 normal control subjects. The Pearson product-moment correlation (r) and the Spearman rank correlation (rs) between SPT and MP were calculated. RESULTS: The magnitudes of simulated PP determined with the SPT and the MP correlated well (r = 0.92, P < 0.005, and r = 0.96, P < 0.001). Correlation also was good in patients with ON (rs = 0.90, P < 0.05). The positive predictive value of the SPT was 100%, and the negative predictive value was 92%. The PP was absent in all control subjects testing with either pendulum. The normal range for PP varied from -1.40 to 1.52 msec. For the SPT, the intraobserver variability coefficient was 8.2%, and the interobserver variability coefficient was 10.5%. CONCLUSIONS: The authors believe that SPT will be of value to clinicians on bedside evaluation of motion stereopsis dysfunctions. The normal range of PP was approximately +/- -1.5 msec (approximately +/- -1.5 cm), corresponding to a 0.3-log unit neutral density filter).

Acute Disease↗
PubMed1985

Spatial memory in rats: electroconvulsive shock selectively disrupts working memory but spares reference memory.

In two experiments rats were trained until they displayed highly accurate spatial memories when a 4-h delay was imposed between the to-be-remembered event (TBRE) and the retention test in a 12-arm radial maze. If the procedure tested only working memory (WM) electronvulsive shock (ECS) 2 h after the TBRE produced amnesia but ECS immediately after the TBRE was ineffective. If the testing procedure also involved a reference memory (RM) component, ECS degraded WM regardless of whether it was given 0 or 2 h after the TBRE. RM was not affected. With either training procedure administering ECS 2 h before the TBRE was ineffective. Thus, in the radial maze truly old spatial RM was immune to disruption by ECS while more recent WM was vulnerable. Possible explanations of the data are presented.

Animals↗
PubMed2003

Executive function assessed by memory updating and random generation in schizotypal individuals.

Individuals scoring high (N=32) and low (N=27) on the unusual experiences (UnEx) scale of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) were selected from a large sample (N=265) of normal volunteer undergraduates. The high- and low-UnEx groups were compared on two tasks, random generation and memory updating, which target executive functions that inhibit prepotent responses and update current information. The groups differed only on the R measure of random generation that assesses inequality in the relative frequencies of response alternatives, a result attributed to superstitious behaviour rather than to executive deficit. The results suggest that the executive impairments previously observed in high schizotypal individuals using the Wisconsin Card Sorting Test and other measures are selective rather than global.

Adult↗
PubMed2003

Relationships between various behavioural abnormalities and nigrostriatal dopamine depletion in the unilateral 6-OHDA-lesioned rat.

While rotational asymmetry is used as a characteristic behavioural sign of striatal dopamine (DA) loss in unilateral animal models of Parkinson's disease (PD), there is relatively little analysis of how other common behavioural deficits relate to nigrostriatal DA depletion. We analysed the relationships between several deficits induced by unilateral 6-OHDA lesions and striatal neurochemistry, as well as neuronal loss in the dopaminergic substantia nigra (SN). Behaviour was evaluated from before until 6 weeks after surgery and abnormalities appeared in body axis, head position and sensorimotor performance as well as apomorphine-induced rotation. As expected, rotational behaviour correlated with striatal DA loss and not with other striatal neurotransmitters measured. Similar observations were found for sensorimotor deficits ('disengage task'). Both deficits were observed in rats with >70% loss of TH+ nigral neurons and >80% loss of striatal DA. Additional postural abnormalities appeared with mean losses of 87% of nigral DA neurons and 97% striatal DA, consistent with observations in patients with advanced PD. The data show that the repertoire of behavioural abnormalities manifested by hemiparkinsonian rats relate directly to the degree of nigrostriatal DA loss and, therefore, mimic features of PD. Analysis of such behaviours are relevant for chronic therapeutic studies targeting PD.

Animals↗
PubMed1982

A study of neurodevelopmental findings in early adolescent delinquents.

Subtle deficits or delays in the development of the central nervous system in young children are associated with problems affecting learning, behavior, and social adjustment. Less is known about the impact of such neurodevelopmental dysfunction in adolescents. This study assesses the possible association between neurodevelopmental delays and juvenile delinquency. An adolescent neurodevelopment examination was devised and administered to 54 delinquents and 51 secondary school students. Six areas were assessed. There were no significant differences in the prevalence of minor neurologic signs (P = 0.37) or in gross motor function (P = 0.02) and temporal sequential organization (P = 0.04). The greatest differences were in visual processing (P = 0.0002) and auditory-language function (P = 0.0001). Eighteen percent of delinquents and 4% of the comparison group were deficient in two or more neurodevelopmental areas. Nine percent of the delinquents and none of the comparison group had three or more dysfunctions. A neurodevelopmental examination may be a useful diagnostic tool for identifying endogenous factors in behavior, learning, and adjustment problems of this age group. Such findings have implications for the formulation of individualized management strategies.

Adolescent↗
PubMedDate not supplied

Visuospatial working memory in Turner's syndrome.

Turner's syndrome is a genetic disorder, specific to women, in which one of the X chromosomes is partially or completely deleted. This syndrome is associated with physical features such as short stature or failure in primary and secondary sexual development, together with a specific pattern of cognitive functions. It has been suggested that women affected by Turner's syndrome perform poorly in tasks measuring visuospatial abilities and have a verbal IQ significantly higher than performance IQ. Although this result has received strong empirical support, the nature of the visuospatial deficit is still unclear. Recent studies on visuospatial processes have highlighted that the underlying cognitive structure is more complex than previously suggested and several dissociations have been reported (e.g., visual vs spatial, sequential vs simultaneous, or passive vs active processes). In the present study we analyze in detail the characteristics of the visuospatial deficit associated with Turner's syndrome by presenting four young women with a comprehensive battery of tasks designed to tap all aspects of visuospatial working memory. Results confirm that Turner's syndrome is associated with a general visuospatial working memory deficit, but the pattern of performance of different cases can be different, with a greater emphasis on active visuospatial processes. and on either sequential or simultaneous spatial processes.

Adult↗
PubMed1999

The effect of phorbol esters on spinal cord amino acid concentrations and responsiveness of rats to mechanical and thermal stimuli.

There is now mounting evidence supporting the hypothesis that pathological perceptual disorders described as secondary hyperalgesia and allodynia may be due to sensitization of spinal cord dorsal horn neurons. Protein kinase C (PKC) is thought to be one of the factors in the cascade of events leading from peripheral tissue damage to the sensitization of central neurons. In our experiments, we have used local microdialysis administration of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to activate PKC in the spinal cord dorsal horn in awake rats. In behavioral tests the responsiveness of the animals to von Frey filaments (1-1200 mN) and to heat stimuli applied to the hindpaws was tested. Thirty minutes after the TPA infusion the threshold for the paw withdrawal response was significantly decreased (from 160 to 6 mN) and the responses to suprathreshold stimuli were more robust. An increased mechanical sensitivity was no longer present when tested 1.5 and 5 h after the TPA application was terminated. When heat stimuli were tested, the TPA infusion resulted in a significantly prolonged time during which the animals held their hindpaws above the supporting surface after the heat stimulus (0.5 and 1.5 h after TPA), and in a decreased threshold for the heat stimulus (latency of withdrawal) 5 h after TPA. HPLC analysis of the perfusate obtained by microdialysis in vivo showed a significant increase in the extracellular levels of aspartate, glutamate, glycine and taurine, and a decrease of the glutamine level during TPA infusion. The levels of asparagine, serine, threonine and alanine did not change. Application of the inactive phorbol ester (alpha-TPA) did not evoke any change from the control values either in the AA concentrations or in the behavioral tests. Our results suggest that activation of PKC in the spinal cord evokes mechanical allodynia and thermal hyperalgesia and provides further evidence that PKC is involved in the process of the modulation of nociceptive information at the spinal cord level.

Amino Acids↗
PubMed2003

Convulsive and postural effects of lesioning the mid-substantia nigra pars reticulata in naïve and 6-hydroxydopamine lesioned rats.

The subthalamic nucleus is targeted for the treatment of Parkinson's disease. Unilateral lesions improve some aspects of parkinsonism but produce postural abnormalities in animal models but the exact pathways producing these effects remain to be defined. Using a battery of tests we evaluated the effects of lesioning one of the two major subthalamic targets, the substantia nigra pars reticulata in naïve and 6-OHDA lesioned rats. Lesions targeting the mid-substantia nigra pars reticulata resulted in acute tonic-clonic seizures and intense contralateral rotational asymmetry. During the first month after substantia nigra pars reticulata lesions there was normalisation of the ipsilateral head position bias induced by unilateral 6-OHDA lesions, significant contralateral body axis bias but no significant alteration of apomorphine induced rotation and sensorimotor neglect in 6-OHDA lesioned rats. Combined with our previous data, this suggests that subthalamic projections via the substantia nigra pars reticulata are important in seizures and postural behaviours. Therefore unilateral subthalamotomy probably induces postural deficits in hemiparkinsonian animals via projections involving the substantia nigra pars reticulata. This has implications for patients undergoing subthalamotomy for treatment of Parkinson's disease.

Animals↗
PubMed1998

Inputs to a physiologically characterized region of the inferior colliculus of the young adult CBA mouse.

Presbycusis is a sensory perceptual disorder involving loss of high-pitch hearing and reduced ability to process biologically relevant acoustic signals in noisy environments. The present investigation is part of an ongoing series of studies aimed at discerning the neural bases of presbycusis. The purpose of the present experiment was to delineate the inputs to a functionally characterized region of the dorsomedial inferior colliculus (IC, auditory midbrain) in young, adult CBA mice. Focal, iontophoretic injections of horseradish peroxidase were made in the 18-24 kHz region of dorsomedial IC of the CBA strain following physiological mapping experiments. Serial sections were reacted with diaminobenzidine or tetramethylbenzidine, counterstained and examined for retrogradely labeled cell bodies. Input projections were observed contralaterally from: all three divisions of cochlear nucleus; intermediate and dorsal nuclei of the lateral lemniscus (LL); and the central nucleus, external nucleus and dorsal cortex of the IC. Input projections were observed ipsilaterally from: the medial and lateral superior olivary nuclei; the superior paraolivary nucleus; the dorsolateral and anterolateral periolivary nuclei; the dorsal and ventral divisions of the ventral nucleus of LL; the dorsal and intermediate nuclei of LL; the central nucleus, external nucleus and dorsal cortex of the IC outside the injection site; and small projections from central gray and the medial geniculate body. These findings in young, adult mice with normal hearing can now serve as a baseline for similar experiments being conducted in mice of older ages and with varying degrees of hearing loss to discover neural changes that may cause age-related hearing disorders.

Acoustic Stimulation↗
PubMed2003

Visual consciousness in health and disease.

Conscious experience is an essential part of normal human life and interaction with the environment. Yet the nature of consciousness and conscious perception remains a mystery. Because of its subjective nature, consciousness has been difficult to investigate scientifically, but clues have been gained through studies involving patients with cortical lesions. During the past decade, the development of event-related fMRI has provided insights into aspects of conscious perception in control subjects and patients with cortical lesions by correlating awareness and performance with neural activity during visual tasks. This article reviews how recent research has advanced understanding of conscious perception, its relationship to neural activity and visual performance, and how this relationship can be altered by visual dysfunction. It also presents recent research about how conscious awareness of vision might be represented at a neural level in the central nervous system.

Attention↗