Biomedical subjects

Roy P C Kessels

Publications and source records attributed to Roy P C Kessels.

At least 19 recordsLinked to original sources

PubMed2006

The modified Location Learning Test: norms for the assessment of spatial memory function in neuropsychological patients.

This study examines the applicability of the modified Location Learning Test (mLLT) as a test of spatial memory in neuropsychological patients. Three groups of participants were examined: stroke patients, patients with diabetes mellitus and healthy participants (N=411). Three error measures were computed, the Total Score (index of overall performance), the Learning Index (the learning curve over subsequent trials) and the Delayed Recall Score, measuring decay over time. The Learning Index was the most sensitive measure, showing differences between the three groups as well as lateralization effects within the stroke group. Also, the mLLT correlated significantly with the Rey Auditory Verbal Learning Test, as well as with age and education level. Regression-based normative data were computed based on the healthy participants. In all, the mLLT appears to be a sensitive and valid test for the detection of object-location memory impairments in clinical groups.

Adolescent↗

PubMed2006

The right hippocampus participates in short-term memory maintenance of object-location associations.

Doubts have been cast on the strict dissociation between short- and long-term memory systems. Specifically, several neuroimaging studies have shown that the medial temporal lobe, a region almost invariably associated with long-term memory, is involved in active short-term memory maintenance. Furthermore, a recent study in hippocampally lesioned patients has shown that the hippocampus is critically involved in associating objects and their locations, even when the delay period lasts only 8 s. However, the critical feature that causes the medial temporal lobe, and in particular the hippocampus, to participate in active maintenance is still unknown. This study was designed in order to explore hippocampal involvement in active maintenance of spatial and non-spatial associations. Eighteen participants performed a delayed-match-to-sample task in which they had to maintain either object-location associations, color-number association, single colors, or single locations. Whole-brain activity was measured using event-related functional magnetic resonance imaging and analyzed using a random effects model. Right lateralized hippocampal activity was evident when participants had to maintain object-location associations, but not when they had to maintain object-color associations or single items. The present results suggest a hippocampal involvement in active maintenance when feature combinations that include spatial information have to be maintained online.

Adult↗

PubMed2006

Perception of emotional facial expressions at different intensities in early-symptomatic Huntington's disease.

BACKGROUND: While there is abundant evidence that patients with Huntington's disease (HD) have an impairment in the recognition of the emotional facial expression of disgust, previous studies have only examined emotion perception using full-blown facial expressions. OBJECTIVE: The current study examines the perception of facial emotional expressions in HD at different levels of intensity to investigate whether more subtle deficits can be detected, possible also in other emotions. METHOD: We compared early symptomatic HD patients with healthy matched controls on emotion perception, presenting short video clips of a neutral face changing into one of the six basic emotions (happiness, anger, fear, surprise, disgust and sadness) with increasing intensity. Overall face perception ability as well as depressive symptoms were taken into account. RESULTS: A specific impairment in recognizing the emotions disgust and anger was found, which was present even at low emotion intensities. CONCLUSION: These results extend previous findings and support the use of more sensitive emotion perception paradigms, which enable the detection of subtle neurobehavioral deficits even in the pre- and early symptomatic stages of the disease.

Adult↗

PubMed2006

Processing of emotional facial expressions in Korsakoff's syndrome.

Interpersonal contacts depend to a large extent on understanding emotional facial expressions of others. Several neurological conditions may affect proficiency in emotional expression recognition. It has been shown that chronic alcoholics are impaired in labelling emotional expressions. More specifically, they mislabel sad expressions, regarding them as more hostile. Surprisingly, there has been relatively little research on patients with Korsakoff's syndrome as a result of chronic alcohol abuse. The current study investigated 23 patients diagnosed with Korsakoff's syndrome compared to 23 matched control participants. This study is the first to make use of a newly developed sensitive paradigm to measure emotion recognition for several emotions (anger, disgust, fear, happiness, sadness and surprise). The results show that patients with Korsakoff's syndrome are impaired at recognizing angry, fearful and surprised facial emotional expressions. These deficits might be due to the reported sub-cortical brain dysfunction in Korsakoff's syndrome.

Adult↗

PubMed2006

Spatial and temporal order memory in Korsakoff patients.

This study directly compared how well Korsakoff patients can process spatial and temporal order information in memory under conditions that included presentation of only a single feature (i.e., temporal or spatial information), combined spatiotemporal presentation, and combined spatiotemporal order recall. Korsakoff patients were found to suffer comparable spatial and temporal order recall deficits. Of interest, recall of a single feature was the same when only spatial or temporal information was presented compared to conditions that included combined spatiotemporal, presentation and recall. In contrast, control participants performed worse when they have to recall both spatial and temporal order compared to when they have to recall only one of these features. These findings together indicate that spatial and temporal information are not automatically integrated. Korsakoff patients have profound problems in coding the feature at hand. Moreover, their lower recall of both features at the same time suggests that Korsakoff patients are impaired in binding different contextual attributes together in memory.

Adult↗

PubMed2006

Cognitive performance, psychological well-being, and brain magnetic resonance imaging in older patients with type 1 diabetes.

Modest cognitive impairment has been reported in young-adult patients with type 1 diabetes. In older patients with type 2 diabetes, cognitive impairments are more pronounced, which might be due to age but also to differential effects of type 1 diabetes and type 2 diabetes on the brain. This study therefore assessed cognitive performance and magnetic resonance imaging (MRI) of the brain in older type 1 diabetic patients. Forty type 1 diabetic patients (age >50 years) and 40 age-matched control subjects were included. Neuropsychological assessment included all major cognitive domains, and psychological well-being was assessed with questionnaires. Atrophy, white-matter abnormalities, and infarcts were rated on MRI scans. Type 1 diabetic patients performed slightly (effect sizes <0.4) worse on cognitive tasks, but only "speed of information processing" reached statistical significance. No significant between-group differences were found on any of the MRI parameters. Type 1 diabetic patients tended to report more cognitive and depressive problems than control subjects, but this did not correlate with the performance on cognitive tests. We conclude that cognition in older type 1 diabetic patients is only mildly disturbed. Chronic exposure to hyperglycemia is in itself, even at older age, apparently not sufficient to have considerable impact on the brain.

Aged↗

PubMed2006

Brain magnetic resonance imaging correlates of impaired cognition in patients with type 2 diabetes.

The structural correlates of impaired cognition in type 2 diabetes are unclear. The present study compared cognition and brain magnetic resonance imaging (MRI) between type 2 diabetic patients and nondiabetic control subjects and assessed the relationship between cognition and MRI findings and blood pressure and metabolic control. The study included 113 patients and 51 control subjects. Brain MRI scans were rated for white matter lesions (WMLs), cortical and subcortical atrophy, and infarcts. Neuropsychological test scores were divided into five cognitive domains and expressed as standardized Z values. Type 2 diabetes was associated with deep WMLs (P = 0.02), cortical (P < 0.001) and subcortical (P < 0.05) atrophy, (silent) infarcts (P = 0.06), and impaired cognitive performance (attention and executive function, information-processing speed, and memory, all P < 0.05). Adjustment for hypertension did not affect the results. Within the type 2 diabetic group, cognitive function was inversely related with WMLs, atrophy, and the presence of infarcts (adjusted for age, sex, and estimated IQ), and there was a modest association with HbA1c and diabetes duration. This association was strongest for age, even more so than in control subjects. We conclude that cognitive impairments in patients with type 2 diabetes are not only associated with subcortical ischemic changes in the brain, but also with increased brain atrophy.

Aged↗

PubMed2005

Neural correlates of human wayfinding in stroke patients.

Wayfinding is a complex cognitive function involving different types of information, such as knowledge about landmarks and direction information. This variety of processes suggest that multiple neural mechanisms are involved, e.g., the hippocampal system, the posterior parietal and temporal cortical areas. Although patient studies and imaging studies have given important insights in the exact neural circuitry underlying wayfinding, many controversies remain. Therefore, the current study sets out to further examine the neuroanatomical correlates of wayfinding in a sample of 31 stroke patients with unilateral lesions, tested with a series of different wayfinding tasks, including landmark recognition, landmark ordering, route reversal and route drawing. For all patients, the exact location of their lesion was determined using CT or MRI scans. Based on existing literature, a number of relevant brain areas were demarcated, after which the extent of damage to these areas was determined for each patient separately. Performance on the landmark recognition task was impaired by damage to the right hippocampal formation, whereas a weak correlation was found between damage to the dorsolateral prefrontal cortex and processing the order of the landmarks. Several brain areas were found to be involved in retracing a route from the end to the beginning, including the right hippocampal formation, the right posterior parietal cortex, the right dorsolateral prefrontal cortex and the right temporal lobe. Finally, damage to the right temporal lobe impaired the ability to draw the route.

Brain↗

PubMed2005

Brain areas involved in spatial working memory.

Spatial working memory entails the ability to keep spatial information active in working memory over a short period of time. To study the areas of the brain that are involved in spatial working memory, a group of stroke patients was tested with a spatial search task. Patients and healthy controls were asked to search through a number of boxes shown at different locations on a touch-sensitive computer screen in order to find a target object. In subsequent trials, new target objects were hidden in boxes that were previously empty. Within-search errors were made if a participant returned to an already searched box; between-search errors occurred if a participant returned to a box that was already known to contain a target item. The use of a strategy to remember the locations of the target objects was calculated as well. Damage to the right posterior parietal and right dorsolateral prefrontal cortex impaired the ability to keep spatial information 'on-line', as was indicated by performance on the Corsi Block-Tapping task and the within-search errors. Moreover, patients with damage to the right posterior parietal cortex, the right dorsolateral prefrontal cortex and the hippocampal formation bilaterally made more between-search errors, indicating the importance of these areas in maintaining spatial information in working memory over an extended time period.

Brain↗

PubMed2005

Effects of errorless and errorful face-name associative learning in moderate to severe dementia.

BACKGROUND AND AIMS: The prevention of errors during learning has been found to be effective in overcoming memory problems in patients with amnesia compared with errorful or trial-and-error learning, possibly as a result of intact implicit memory function. Although errorless learning is a clinically promising technique used in cognitive training settings, to date only a few studies have examined errorless learning in patients with dementia. METHODS: The current study examined errorless and errorful learning using a face-name associative memory task in a group of moderate to severe dementia patients suffering from probable Alzheimer's disease (MMSE < or = 22; n = 10) using a fully counterbalanced within-subject design. RESULTS: Errorless learning had a significantly beneficial effect after two consecutive learning trials (p = 0.01). However, after an unfilled delay of 10 minutes, no significant differences in memory performance were found between errorless and errorful learning. Furthermore, current effects were much smaller compared with previous findings in healthy adults and early-stage dementia patients. CONCLUSIONS: Although errorful learning resulted in better performance in a face-name associative memory task in patients with dementia, this effect was only short-lived. Thus, the beneficial effects of errorless learning are probably not due to intact implicit memory function, but may also be subserved by explicit memory, a memory system that is typically impaired in dementia. Also, the clinical applicability of errorless learning in teaching patients with moderate to severe dementia face-name associations is limited.

Aged↗

PubMed2005

The contribution of implicit and explicit memory to the effects of errorless learning: a comparison between young and older adults.

There is evidence that the prevention of errors during learning might be helpful in improving an impaired memory performance, both in amnesia as well as in normal age-related memory decline. Although errorless learning is a promising technique for use in rehabilitation practice, the underlying mechanisms are unclear. That is, it has been suggested that the beneficial effects of errorless learning operate through implicit memory, whereas others implicate that it is explicit memory that is responsible for the enhanced memory performance after errorless learning. The current study examined the contribution of implicit and explicit memory function to the memory performance after errorless and errorful learning using the process-dissociation procedure. A group of young adults (N=40) was compared to a matched group of older individuals (N=40) on a spatial memory task (i.e., learning the locations of everyday objects in a room). The results clearly show age-related decline in explicit spatial memory, while implicit spatial memory was unaffected. Furthermore, the young group benefited from errorless learning compared to errorful learning, while the older group did not show a difference between the two learning conditions. Also, it was found that the effects of errorful learning were related to explicit memory function, and not implicit processing, corroborating and extending recent findings.

Adult↗

PubMed2005

Spatial working memory and contextual cueing in patients with Korsakoff amnesia.

The current study investigated the effect of Korsakoff syndrome on memory for spatial information and, in particular, the effect of contextual cueing on spatial memory retention. Twenty Korsakoff patients and a comparison group of 22 age- and education- matched participants were tested with a newly developed spatial search task (the Box task). Participants were asked to search through a number of boxes shown at different locations on a touch-sensitive computer screen to find a target object. In subsequent trials, new objects were hidden in boxes that were previously empty. Two conditions were used: the boxes were either completely identical or had different colors serving as a cue. Within-search errors were made if a participant returned to an already searched box; between-search errors occurred if a participant returned to a box that already contained a target item. Moreover, the use of a strategy to remember the locations of the target objects was calculated. The results show that Korsakoff patients make more within and between-search errors than the comparison group, and although they were able to apply a search strategy, it did not help them to remember the locations of the targets. Interestingly, whereas the comparison group benefited from color cues that were given to the boxes, Korsakoff patients failed to do so.

Adult↗

PubMed2005

The effects of type 1 diabetes on cognitive performance: a meta-analysis.

OBJECTIVE: To investigate the exact nature and magnitude of cognitive impairments in patients with type 1 diabetes and the possible association with other disease variables, such as recurrent episodes of hypoglycemia and metabolic control. RESEARCH DESIGN AND METHODS: MedLine and PsycLit search engines were used to identify studies on cognitive performance in patients with type 1 diabetes. Effect sizes (Cohen's d), which are the standardized differences between the experimental and the control group, were calculated. In the meta-analysis, a combined d value was calculated, expressing the magnitude of associations across studies. RESULTS: A total of 33 studies were identified that met the inclusion criteria. Compared with nondiabetic control subjects, the type 1 diabetic group demonstrated a significantly lowered performance on the following cognitive domains: intelligence (d = -0.7), speed of information processing (d = -0.3), psychomotor efficiency (d = -0.6), visual (d = -0.4) and sustained attention (d = -0.3), cognitive flexibility (d = -0.5), and visual perception (d = -0.4). Lowered cognitive performance in diabetic patients appeared to be associated with the presence of microvascular complications but not with the occurrence of severe hypoglycemic episodes or with poor metabolic control. CONCLUSIONS: In patients with type 1 diabetes, cognitive dysfunction is characterized by a slowing of mental speed and a diminished mental flexibility, whereas learning and memory are spared.The magnitude of the cognitive deficits is mild to moderate, but even mild forms of cognitive dysfunction might hamper everyday activities since they can be expected to present problems in more demanding situations.

Attention↗

PubMed2004

Emotional processing in a non-clinical psychosis-prone sample.

Symptoms of psychosis have been proposed to form part of a continuous distribution of experiences in the general population rather than being an all-or-nothing phenomenon. Indeed, schizotypal signs have been reported in subjects from non-clinical samples. Emotional processing has been documented to be deficient in schizophrenia. In the present study, we tested the hypothesis whether putatively psychosis-prone subjects would show abnormalities in emotion processing. Based on the extremes of Launay-Slade Hallucination Scale (LSHS) ratings of 200 undergraduate students, two groups of subjects (total N=40) were selected. All 40 participants filled in the Schizotypal Personality Questionnaire (SPQ). We compared both groups on an alexithymia questionnaire and on four behavioral emotional information processing tasks. Hallucination-proneness was associated with an increased subjective emotional arousal and fantasy-proneness. Although no differences between the high and low group were observed on three behavioral emotion processing tasks, on the affective word-priming task presentation of emotional stimuli was associated with longer reactions times to neutral words in high schizotypal subjects. Also, SPQ scores correlated with several emotion processing tasks. We conclude that these findings lend partial support to the hypothesis of continuity between symptoms characteristic of schizophrenia and psychosis-related phenomena in the normal population.

Adult↗

PubMed2004

Cerebral dysfunction in type 1 diabetes: effects of insulin, vascular risk factors and blood-glucose levels.

Type 1 diabetes can lead to several well-described complications such as retinopathy, nephropathy and peripheral neuropathy. Evidence is accumulating that it is also associated with gradually developing end-organ damage in the central nervous system. This relatively unknown complication can be referred to as "diabetic encephalopathy" and is characterised by electrophysiological and neuroradiological changes, such as delayed latencies of evoked potentials, modest cerebral atrophy and (periventricular) white matter lesions. Furthermore, individuals with type 1 diabetes may show performance deficits in a wide range of cognitive domains. The exact mechanisms underlying this diabetic encephalopathy are only partially known. Chronic metabolic and vascular changes appear to play an important role. Interestingly, the differences in the "cognitive profile" between type 1 and type 2 diabetes also suggest a critical role for disturbances of insulin action in the central nervous system.

Animals↗

PubMed2004

Salivary cortisol and short and long-term memory for emotional faces in healthy young women.

Elevated levels of the stress hormone cortisol are associated with increased episodic memory for emotional events. Elevated levels of cortisol are also seen in anxiety and depression disorders. Because it is well documented how both depression and anxiety are related to valence-specific biases in attention and memory, the present study sought to establish relations between basal cortisol levels and episodic memory for neutral, positive and negative stimuli. Thirty-nine healthy young women performed an immediate recall and long-term (20 min) version of a task measuring spatial memory for neutral, happy and fearful faces. The sample as a whole showed a valence-specific better performance for happy faces than for neutral faces in the immediate recall condition, and a better performance for all emotional faces in the long-term condition. Salivary cortisol measures were found to be related to better memory for emotional faces in the long-term condition. This relation to cortisol was not valence-specific and is similar to effects predicted by a model on long-term consolidation and the influence of cortisol in this process.

Adolescent↗

PubMed2004

Sex differences for selective forms of spatial memory.

In the present study, a systematic comparison of sex differences for several tests of spatial memory was conducted. Clear evidence for more accurate male performance was obtained for precise metric positional information in a wayfinding task and in an object location memory task. In contrast, no sex difference characterized topological information processing (object-to-position assignment). Together, these findings provide further insight in the specificity of sex differences in spatial memory and in the functional architecture of spatial memory. Implications for the relevant evolutionary basis are discussed.

Adult↗

PubMed2004

A single administration of testosterone improves visuospatial ability in young women.

Previous research has documented correlations between endogenous testosterone levels and visuospatial cognitive function. Some causal relations have also been established in treatment designs in which testosterone was administered to elderly subjects for a number of weeks. Particularly, one study reported a selective effect of a single administration of testosterone on some aspects of spatial memory in 15 women. The present study tested the hypothesis whether a single administration of 0.5 mg of sublingual testosterone would improve visuospatial ability in healthy young women on a test that has consistently been associated with male superiority. Twenty-six women participated in a double-blind placebo-controlled cross-over trial of single administration of testosterone and placebo. Subjects were tested in the same phase of the menstrual-cycle. Four to five hours after both administrations, subjects completed a standardized measure of visuospatial ability (3-D Mental Rotations Test). Visuospatial ability improved significantly after testosterone administration compared to placebo, after controlling for learning effects due to repeated testing. Testosterone is suggested to be causally related to visuospatial ability in young women.

Adult↗