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Biomedical subjects

E H de Haan

Publications and source records attributed to E H de Haan.

At least 19 recordsLinked to original sources
PubMed2002

Spatial and temporal characteristics of visual motion perception involving V5 visual cortex.

The anatomical substrates of the perception of motion have not yet been established in a detailed way on an individual level. The aim of this study was to develop a systematic procedure for mapping the visual cortex using Transcranial Magnetic Stimulation (TMS). The results showed that such an individual and detailed map of the spatial and temporal characteristics of motion perception can be constructed using TMS.

Adult↗
PubMed2001

Visual imagery without visual experience: evidence from congenitally totally blind people.

We explored the ability of congenitally totally blind people (who were contrasted with age-, sex- and education matched blindfolded sighted subjects) to perform tasks which are mediated by visual mental imagery in sighted people. In the first (pictorial) task, subjects had to mentally compare the shape of the outline of three named objects and to indicate the odd-one-out. In the second (spatial) task the participants were asked to memorise the position of a target cube in two- and three-dimensional matrices, based on a sequence of spatially based imagery operations. In addition, during half of the trials of both imagery tasks subjects were required to perform a concurrent finger tapping task, to investigate whether the blind subjects would be more dependent on spatial processing. Although blind participants made significantly more errors than sighted participants, they were well able to perform the spatial imagery task as well as the pictorial imagery task. Interference from the concurrent tapping task affected both groups to the same extent. Our results shed new light on the question whether early visual experience is necessary for performance on visual imagery tasks, and strongly suggest that vision and haptics may share common representations.

Adult↗
PubMed2001

Effects of slow rTMS at the right dorsolateral prefrontal cortex on EEG asymmetry and mood.

In a sham-controlled design (n = 12), slow repetitive transcranial magnetic stimulation (rTMS) was applied to the right dorsolateral prefrontal cortex for 20 min, and the subsequent effects on mood and the EEG spectrum were investigated, Analysis revealed a significant left hemisphere increase in EEG theta activity at 25-35 and 55-65 min after stimulation. In addition, participants reported significant decrease in anxiety immediately after stimulation, as well as 35 and 65 min after rTMS. These findings indicate that reductions in anxiety after slow rTMS at the right dorsolateral prefrontal cortex are associated with a contralateral increase in theta activity.

Adult↗
PubMed2001

Varieties of human spatial memory: a meta-analysis on the effects of hippocampal lesions.

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.

Animals↗
PubMed2001

Hallucinatory predisposition and vividness of auditory imagery: self-report and behavioral indices.

This study examined the relation between a subjective and a behavioral measure of the vividness of auditory imagery as well as the disposition towards hallucination in normal subjects. In addition to the Launay-Slade Hallucination Scale, subjects (57 university students) completed the Betts questionnaire in which they rated the vividness of their experienced mental images and performed a behavioral task aimed at measuring auditory imagery. The task consisted of a perception and an imagery condition in which subjects had to indicate the odd one of three everyday sounds. Performance on the behavioral task did not correlate with the auditory or scores on the Visual subscale of the Betts. In addition, neither scores on the behavioral measure nor the Auditory subscale of the Betts correlated significantly with hallucinatory predisposition as rated on the Launay-Slade Hallucination Scale. In contrast, the Visual subscale of the Betts did correlate with scores on the Launay-Slade Hallucination Scale, consistent with previous research. We conclude that there is no straightforward relationship between imagery vividness and hallucinatory experiences and that subjective and objective indices of imagery vividness measure different aspects of mental function.

Adult↗
PubMed2000

Spatial working memory performance after high-frequency repetitive transcranial magnetic stimulation of the left and right posterior parietal cortex in humans.

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.

Adult↗
PubMed2000

Laterality effects in selective attention to threat after repetitive transcranial magnetic stimulation at the prefrontal cortex in female subjects.

Recently, several experiments have indicated that the left and right prefrontal cortex (PFC) are differently involved in emotional processing. The aim of this study was to investigate the role of the left and right PFC in selective attention to angry faces by using a pictorial emotional Stroop task. Slow repetitive transcranial magnetic stimulation (rTMS) was applied to the left and right PFC of 10 female subjects for 15 min on separate days. Results showed a significant effect of stimulation position: right PFC rTMS resulted in selective attention towards angry faces, whereas left PFC rTMS resulted in selective attention away from angry faces. This finding is in accordance with theoretical accounts of the neural implementation of approach and withdrawal systems.

Adult↗
PubMed2000

Spatial localization in patients with unilateral posterior left or right hemisphere lesions.

In this study, perceptual and visuomotor spatial localization were examined in patients with unilateral right (RH) or left (LH) hemisphere lesions and in a group of control subjects. Perceptual localization was measured with a position-discrimination task; in the visuomotor localization task, subjects had to point to a visual target. Both tasks were investigated in conditions with or without background visibility and with central and peripheral targets. In the visuomotor task, hand visibility was also manipulated. In both tasks, targets were presented in the left and right visual hemifield. The perceptual task revealed impairments for both LH and RH patients in the contra-lateral visual hemifield. RH patients also revealed slightly larger impairments in conditions without a visual background. In the visuomotor task, the LH patients were not impaired, whereas the RH patients were impaired in conditions without hand visibility and/or background visibility. Hence, our data strengthen the idea that spatial localization is not a unitary function and that perceptual and visuomotor localization can be selectively impaired. We suggest that one of the important factors distinguishing between localization impairments in RH and LH patients might be absolute versus relative localization.

Adult↗
PubMed2000

Memory for object locations in Korsakoff's amnesia.

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.

Female↗
PubMed2000

Music training and mental imagery ability.

Neuroimaging studies have suggested that the auditory cortex is involved in music processing as well as in auditory imagery. We hypothesized that music training may be associated with improved auditory imagery ability. In this study, performance of musically trained and musically naive subjects was compared on: (1) a musical mental imagery task (in which subjects had to mentally compare pitches of notes corresponding to lyrics taken from familiar songs); (2) a non-musical auditory imagery task (in which subjects had to mentally compare the acoustic characteristics of everyday sounds); and (3) a comparable measure of visual imagery (in which subjects had to mentally compare visual forms of objects). The musically trained group did not only perform better on the musical imagery task, but also outperformed musically naive subjects on the non-musical auditory imagery task. In contrast, the two groups did not differ on the visual imagery task. This finding is discussed in relation to theoretical proposals about music processing and brain activity.

Adult↗
PubMed2000

Growth hormone, insulin-like growth factor I and cognitive function in adults.

This review focuses on the possible contribution of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis to cognitive function. Binding sites for GH and IGF-I are found in various areas of the brain. Their distribution suggests that GH and IGF-I contribute to the function of the hippocampus, a brain structure important for the maintenance of cognitive functions such as learning and memory. Evidence for cognitive deficits in GH-deficient individuals has been found in various studies, some of which have shown that these deficits can be reversed by GH substitution therapy. In addition to examining conditions of GH deficiency, this article reviews studies evaluating the correlation between the cognitive deficits associated with ageing and age-related decreases in GH or IGF-I secretion. Based on the available data, one might hypothesize that relative GH or IGF-I deficiency could contribute to the deterioration of cognitive functions observed in the elderly.

Adult↗
PubMed2000

Frontal-lobe involvement in spatial memory: evidence from PET, fMRI, and lesion studies.

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.

Cerebrovascular Circulation↗
PubMed2000

Mental imagery and perception in hallucination-prone individuals.

College students screened for hallucination-proneness using the Launay-Slade Hallucination Scale (LSHS) were compared on measures of self-report vividness of imagery and on behavioral measures of imagery and perception (visual and auditory). Specifically, we tested the hypothesis whether hallucination-prone individuals would show smaller differences between imagery and perception performance, which may be indicative of increased sensory characteristics of mental images. We replicated earlier findings of higher self-report imagery ratings in the high hallucination-prone group. However, the two groups did not differ on five of six behavioral imagery-perception comparisons. On one visual task, hallucination-proneness was associated with larger imagery-perception differences. Our results reveal a dissociation between the level of subjective experience and the information processing level. Although vividness of mental images may be subjectively associated with mild hallucinatory experiences, we suggest that cognitive processes associated with reality discrimination rather than increased perceptual characteristics of mental images may play a role at the information processing level.

Adult↗
PubMed2000

Spatial memory impairment in patients after tumour resection: evidence for a double dissociation.

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.

Adult↗
PubMed2000

Age-sensitive cognitive function, growth hormone and insulin-like growth factor 1 plasma levels in healthy older men.

Circulating levels of growth hormone (GH) change during the process of aging. Decline of cognitive functioning with aging is also well established. In this study, we investigated whether insulin-like growth factor 1 (IGF-1) and the GH response to a challenge of GH-releasing hormone and GH-releasing peptide 6 were associated with age-sensitive cognitive functions, but not with functions that do not decline with aging, in 17 healthy male subjects aged between 66 and 76 years. In addition, relations with anthropometric measures were examined. Neuropsychological performance was scored on tests of variables not sensitive to aging (general knowledge, vocabulary, basic visual perception and reading ability), and of variables sensitive to aging (visuoconstructive ability, perceptual motor and mental processing speed, and verbal long-term memory). After correcting for education, the serum GH response was significantly associated with two age-sensitive cognitive tests (measures of mental processing speed), but with none of the tests not sensitive to aging. However, the direction of the association was opposite to the relation between IGF-1 and these cognitive tests: higher levels of GH response were associated with poorer cognitive performance, whereas higher levels of IGF-1 were associated with better performance. GH response, but not IGF-1, was inversely correlated with body mass index. The results are in accordance with previous research suggesting a disruption of the relation between IGF-1 and GH secretion in older age.

Aged↗