Biomedical subjects
Publications and source records attributed to R P Kessels.
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The current meta-analysis included 27 studies on spatial-memory dysfunction in patients with hippocampal damage. Each study was classified on the basis of the task that was used, i.e., maze learning, working memory, object-location memory, or positional memory. The overall results demonstrated impairments on all spatial-memory tasks. Clear differences in effect size were found between positional memory on the one hand and maze learning, object-location memory, and working memory on the other hand. Lateralization was found only on maze learning and object-location memory. These findings clearly indicate that specific aspects of spatial memory can be affected in various degrees in patients with hippocampal lesions. Moreover, these results strongly support the notion that the hippocampus is important in the processing of metric positional information, probably in the form of an allocentric cognitive map.
The effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) at the left or right posterior parietal cortex were studied using a spatial working memory task. Eight subjects were stimulated over the P3 and P4 electrode site at 115% of the motor threshold (frequency 25 Hz, trains of 200 ms) during the 1000-ms delay of the spatial working memory task, or received sham stimulation. It was found that the reaction times were slower during right-parietal rTMS than during left-parietal rTMS. No differences were found between the percentages correct responses. These results are in line with recent neuroimaging findings and data from patients with cerebral lesions, suggesting that the posterior parietal cortex is especially involved in spatial processing, and provide converging evidence for recent theories on hemispheric specialization.
Deficits in spatial context memory are an important characteristic of Korsakoff's amnesia. In memory for spatial context information, there is evidence for a functional dissociation of three separate processes: (1) binding of object information to locations (i.e. binding complex memories), (2) exact, metric processing of Euclidean co-ordinates, and (3) an integration mechanism. In the present study, these sub-mechanisms were assessed experimentally in a group of Korsakoff patients (N = 20) and compared to healthy controls (N = 20) to see whether selective deficits can be demonstrated. It was found that Korsakoff patients display deficits on all three spatial-memory conditions, which are not the primary result of deficits in visuo-spatial construction and memory for object identity. No evidence for selective impairments could be observed. These impairments can be linked to damage of diencephalic regions and perhaps the parietal cortex.
Previous work has indicated that object-location memory is sensitive to sex differences as well as variations in the menstrual cycle. The goal of the present study was to further examine the hormonal basis of human spatial memory by assessing the effects of a single dose of exogenous testosterone in healthy young women on three recall conditions: positional reconstruction; object-to-position-assignment; and the combined condition in which subjects both have to reconstruct the precise locations and to link the different objects to the correct places. In the latter condition, delayed recall (3 min delay) improved with testosterone. Although the effects were only small and need further substantiation, they support the idea that testosterone may have an activational effect on selective aspects of cognitive functioning.
Complaints on cognitive functioning are often reported in patients suffering from whiplash syndrome, although objective neuropsychological test results do not always support these. In addition, radiological abnormalities and anatomical lesions are found only in a minority of these patients. This has led to a controversy about its existence in the literature. In this systematic review, the results of 22 neuropsychological studies on whiplash were quantitatively analyzed, focusing on working memory, attention, immediate and delayed recall, visuomotor tracking, and cognitive flexibility. Our findings suggest that a consistent overall pattern of cognitive dysfunction can be demonstrated after whiplash injury through neuropsychological testing, both compared to healthy and to asymptomatic controls. Six months after the accident, improvement is found in working memory, attention, immediate recall, and visuomotor tracking. The results are discussed in the light of recent findings on the effect of cerebral dysfunction, malingering, pain-related factors, and the role of coping strategies and posttraumatic stress on neuropsychological test performance.
Many studies have identified the prefrontal cortex as the brain area that is critical for spatial memory, both in humans and in other primates. Other studies, however, have failed to establish this relation. Therefore, the aim of this paper was to review the literature regarding the role of the human prefrontal lobe in spatial memory. This was done by examining the evidence obtained from neuropsychological patients and from studies using brain-imaging techniques (PET and fMRI). Evidence supporting the notion that the prefrontal cortex is extensively involved in spatial working memory was found. The majority of these studies, however, suggests that frontal-lobe involvement is not related to the type of material that is being processed (e.g., spatial vs. nonspatial), but to process-specific functions, such as encoding and retrieval. Theoretically, these functions could be linked to the central executive within Baddeley's working-memory model, or to recent theories that emphasize the various processes that play a role in working memory. Also, methodological issues were discussed. Further research is needed to enhance our understanding of the precise interaction of domain-specific and general processes.
Human spatial memory can be divided into multiple, partly separate cognitive processes. In this study, object location memory was studied using a set of tasks that assessed three different spatial memory aspects: positional memory, object location binding, and a combined process. Also, maze learning and spatial span memory were measured. Ten patients who had undergone intracranial tumour resection participated, and their individual results were compared with control data from 24 healthy subjects. Four patients showed selective spatial memory impairments; two patients were impaired at positional memory, and two other patients were impaired on object location binding and the combined process. This double dissociation provides further evidence for the notion that object location memory is not a unitary system, but consists of at least two separate mechanisms. In addition, spatial memory problems were predominantly present in the patients with lesions in either the right hemisphere or in the parietal lobe. These results are in agreement with previous findings on the involvement of the right hemisphere and the posterior parietal cortices in spatial processing.
This article describes a standardized administration and scoring procedure for the widely used Corsi Block-Tapping Task, designed to assess the visual memory span. This method was applied in a group of healthy participants (n = 70) and a group of patients with cerebral lesions (n = 70), that were categorized on the basis of lesion location (left or right hemisphere, bilateral or subcortical). The percentile distribution as well as cutoff points on the basis of the control data are provided. It was found that 20% of the patients perform in the borderline range on this task, and over 8% have an impaired performance ("retarded"). In addition, right hemisphere patients performed worse than left hemisphere patients. These data show that the Corsi Block-Tapping Task can be effectively used to assess visuospatial short-term memory in patients with brain damage, and is selective for the side of the lesion.
It was the purpose of this experiment to study interference effects of colour or luminance peripheral flicker (in order to saturate either the parvocellular or the magnocellular stream) on object identity and spatial location memory. Colour flicker interfered with object identity recognition, whereas luminance flicker affected memory for spatial location. Moreover, overall performance was worse if coloured rather than grey-scaled objects were used in the stimulus display. There was no selective effect of coloured flicker affecting coloured objects and chromatic flicker affecting chromatic objects. These results provide strong evidence for the theoretical position that the what pathway relies heavily on information derived from the P stream and the where pathway on the M stream.
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Object Relocation is a computer program for Windows 95, with which experiments on spatial memory for object locations can be designed, run, and analyzed. Because of its clear graphical user interface, no long and complex command syntax is needed. Basically, a stimulus consists of a frame that contains a chosen number of locations (i.e., the actual spatial layout) to which objects can be assigned. When the experiment is run, these stimuli are presented to the subject for a variable period of time. Subsequently (either with or without a delay), the objects are presented in a row above the frame and have to be relocated to the correct positions. Finally, the raw data can be analyzed efficiently, using various error scores, and an SPSS-ready output file can be produced. Object Relocation is a very flexible program: New objects and positions can easily be added, and various options for presentation and relocation are present.
Whiplash patients often have physical, psychosomatic and cognitive complaints, although clear neurological and neuropsychological signs of damage are absent. However, in some studies a functional loss of attention was found. In order to compare attentional dysfunctions in whiplash patients with age-matched controls, attention was measured neuropsychologically with the aid of the PASAT, and psychophysiologically with the aid of the prepulse inhibition paradigm. In addition, the reactivity for intense acoustic stimulation was investigated. The POMS and the SCL-90 were used to evaluate psychological and somatic signs. The results showed that whiplash patients (n=24) had lower scores on the PASAT and higher scores on the questionnaires compared to healthy controls (n=21). However, no group differences could be determined on the psychophysiological variables. Furthermore, the PASAT and prepulse inhibition data did not correlate. The lower PASAT scores indicate that whiplash patients seem to have deteriorated divided attention, but an attention deficit as measured with the prepulse inhibition paradigm is not disclosed. Finally, there were no signs of a heightened reactivity of the auditory system, which casts doubts on a presumed heightened sensitivity for sound in whiplash patients.