Biomedical subjects

Irene Daum

Publications and source records attributed to Irene Daum.

At least 37 records · Page 2Linked to original sources

PubMed2005

Processing of affective stimuli in alcoholism.

Investigations of neuropsychological functioning in alcoholism have revealed executive and memory deficits which have been interpreted in the light of the "frontal lobe hypothesis" which asserts that the frontal lobes are particularly vulnerable to the toxic effects of alcohol. Inspite of the known involvement of the orbitofrontal cortex in the processing of affective stimuli, only few studies concerning affective processing in alcoholism have been conducted so far. Alcoholics and healthy controls were compared by using a comprehensive neuropsychological test battery which included the measurement of facial affect as well as affective prosody perception. Analysis revealed impairments of alcoholics with respect to naming prosody with incongruent semantic content and matching affective prosody to facial expression. Alcoholics showed deficits of affective prosody processing which became evident in ambiguous situations in which no additional cues could be used simultaneously for the interpretation of emotional prosody. These deficits could contribute to interpersonal problem solving and should thus be considered in the therapy of alcoholism.

Adult↗

PubMed2005

Differential involvement of the cerebellum in biological and coherent motion perception.

Perception of biological motion (BM) is a fundamental property of the human visual system. It is as yet unclear which role the cerebellum plays with respect to the perceptual analysis of BM represented as point-light displays. Imaging studies investigating BM perception revealed inconsistent results concerning cerebellar contribution. The present study aimed to explore the role of the cerebellum in the perception of BM by testing the performance of BM perception in patients suffering from circumscribed cerebellar lesions and comparing their performance with an age-matched control group. Perceptual performance was investigated in an experimental task testing the threshold to detect BM masked by scrambled motion and a control task testing the detection of motion direction of coherent motion masked by random noise. Results show clear evidence for a differential contribution of the cerebellum to the perceptual analysis of coherent motion compared with BM. Whereas the ability to detect BM masked by scrambled motion was unaffected in the patient group, their ability to discriminate the direction of coherent motion in random noise was substantially affected. We conclude that intact cerebellar function is not a prerequisite for a preserved ability to detect BM. Because the dorsal motion pathway as well as the ventral form pathway contribute to the visual perception of BM, the question of whether cerebellar dysfunction affecting the dorsal pathway is compensated for by the unaffected ventral pathway or whether perceptual analysis of BM is performed completely without cerebellar contribution remains to be determined.

Adult↗

PubMed2005

Neuropsychological deficits after mechanical aortic valve replacement.

BACKGROUND AND AIM OF THE STUDY: Studies using transcranial Doppler monitoring have identified high-intensity transient signals (HITS) after mechanical valve replacement. Although cognitive dysfunction in relation to HITS was reported in some studies, the current data basis is inconsistent. The study aim was to investigate the long-term effects of HITS on cognitive function. METHODS: Forty patients who had undergone mechanical valve replacement (mean 5.3 years previously) participated in the study. HITS-measurements were performed on the day of neuropsychological assessment. Patients were allocated to HITS-high and HITS-low groups on the basis of the median HITS-rate. Both patient groups completed a neuropsychological test battery and were compared to healthy controls. RESULTS: Both patient groups showed verbal and visual memory deficits in comparison with controls. The HITS-high group scored lower on verbal memory compared to the HITS-low group. In addition, the HITS-high group showed executive deficits when compared to the HITS-low group and controls. The significant effects with respect to verbal memory and executive functions remained after extracorporeal circulation time differences were controlled for. CONCLUSION: The study results imply that heart valve replacement with mechanical prostheses may be associated with mild cognitive impairment. The differential impairment pattern of the high- and low-HITS groups further suggests that the number of HITS may be of critical importance. The observed memory impairments were consistent with the view that cognitive dysfunction after valve replacement may be due to temporal lobe dysfunction. However, future studies are required to investigate the association of number of HITS, cerebral changes and cognitive function in further detail.

Aged↗

PubMed2004

Remote memory in advanced Alzheimer's disease.

The present study investigated remote memory functioning in advanced dementia of Alzheimer type (DAT). Remote memory measures included the Autobiographical Memory Enquiry (AME) and autobiographical fluency (AF), as well as recognition of remote public events and famous faces. Ten DAT patients were selected with Mini-Mental State Exam (MMSE) scores less than 15. Compared to healthy controls, DAT patients were impaired on all measures of remote memory, although autobiographical fluency for names was only borderline impaired. There was no clear evidence of a monotonic temporal gradient with the AME; however, both subjects groups showed better preserved early compared to more recent public-event memory. A measure of semantic fluency was correlated with autobiographical and remote public-event memory among the patients only. Overall, results indicate a minimal outline of preserved remote memory in advanced DAT, with evidence of an association between remote memory performance and executive functioning.

Aged↗

PubMed2004

Fear, conditioning, and aging: theoretical comment on LaBar et al. (2004).

Age-related impairments in associative learning have been found in studies using classical conditioning of motor responses. However, it is as yet unclear whether conditioning of fear responses is similarly affected by aging. K. S. La Bar et al. (2004) aimed to address this issue by studying age effects on fear conditioning applying a discrimination paradigm. Considering these results, this commentary discusses methodological issues in investigating fear conditioning as well as similarities and differences between associative learning of motor and autonomic responses with respect to neuronal substrates, susceptibility to aging, and the role of awareness of stimulus contingencies in mediating aging effects.

Aging↗

PubMed2004

Effects of age and awareness on eyeblink conditional discrimination learning.

The present study aimed to assess the effects of aging and awareness on conditional discrimination learning within an eyeblink conditioning procedure by using a consecutive age-groups design (20-35 years, 36-50 years, 51-65 years, 66-80 years). Increasing age was associated with a decline in overall eyeblink conditioned response (CR) frequency and a deficit in conditional discrimination learning in the 2 older groups. Awareness of stimulus contingencies affected discrimination performance but not overall CR rates in younger subjects. Older subjects did not achieve eyeblink conditional discrimination learning, regardless of awareness. Discrimination performance correlated with measures of declarative memory. The pattern of results is discussed with respect to the involvement of hippocampal-cerebellar interactions and awareness in the mediation of age-related conditioning changes.

Adult↗

PubMed2004

Clipping versus coiling: neuropsychological follow up after aneurysmal subarachnoid haemorrhage (SAH).

Patients treated with microsurgical clipping of ruptured intracranial aneurysms often suffer from neuropsychological deficits in spite of a good neurological outcome. The purpose of this study was to explore if the deficits are related to the type of therapy. Two groups of 16 patients each suffering from aneurysmal SAH, matched for sex, age, aneurysm-site and Hunt and Hess score, and 16 control subjects were examined with a battery of neuropsychological tests including memory, attention, and executive function. Depression, mood, and quality of life were also assessed. One patient group had been treated with surgical clipping, the other with endovascular coiling. Both patient groups showed deficits in verbal and visual memory. Clipped patients were slightly more impaired than coiled patients, especially on measures of affect and on a self-assessment measure of executive function. The pattern of results suggests that the neuropsychological outcome after aneurysmal SAH is affected by both the severity of the bleeding and the type of therapy.

Affect↗

PubMed2003

Event-related potentials reflect impaired face recognition in patients with congenital prosopagnosia.

Event-related brain potentials (ERPs) to faces have been shown to be altered in patients suffering from prosopagnosia. In this report we present ERP findings from two patients suffering from a congenital form of prosopagnosia, with other visual and cognitive functions being spared and without any structural abnormalities as assessed by anatomical brain imaging. Subjects were presented with photographs of faces and houses, and they had to respond to photographs of hands. Both patients did not show a difference in N170 amplitude to faces compared to houses, whereas there was a significant N170 difference of these two stimulus classes in healthy control subjects.

Adult↗

PubMed2003

Apomorphine reduces BOLD signal in fMRI during voluntary movement in Parkinsonian patients.

Our group investigated modulatory effects of apomorphine on cerebral activation patterns during finger tapping movements in seven Parkinson's disease (PD) patients off medication. Cerebral activation was measured according to an established fMRI protocol. Apomorphine application disclosed a reduction of cerebral activation patterns to the contralateral precentral gyrus affecting both clinically affected and unaffected sides; tapping with the unaffected hand additionally revealed activation in the contralateral postcentral gyrus. These findings contradict those of similar functional imaging studies performed in PD to date, which variously found augmentation of cerebral activation patterns in Parkinsonian patients after dopaminergic stimulation. One conceivable explanation for our singular results would be preferred binding of apomorphine to presynaptic dopaminergic receptors, leading to inhibition of endogenous dopamine release and resultant diminished dopaminergic stimulation, reflected in diminished cerebral activation patterns. These findings warrant future consideration and further investigation of possible central inhibitory effects of dopaminergic therapy in functional imaging studies in PD.

Antiparkinson Agents↗

PubMed2003

Involvement of the mediodorsal thalamic nucleus in mediating recollection and familiarity.

The mediodorsal (MD) thalamic nucleus is thought to play an important role in memory processes. Distinct hippocampal-thalamic-prefrontal connections have been described as the potential neural substrate for both, recollection and familiarity. The aim of this study was to investigate whether the MD is part of the circuits underlying these two memory components. We assessed the effects of ischemic thalamic lesions with or without MD involvement on performance in a word list discrimination task and standard tests of memory and executive function. Estimates of recollection and familiarity were derived using the dual-process signal-detection model (DPSD). The results revealed impairments in both, recollection and familiarity, after unilateral thalamic damage, with recollection being more affected than familiarity. There were no significant differences in the memory performance of patients with MD lesions compared to patients with ventrolateral-thalamic lesions except for familiarity estimates, which were lower for the latter group. Lesions involving the MD led to recollection deficits, although inspection of individual cases suggested a decrease in both memory components after damage in the medial part of this nucleus. Executive dysfunction was associated with lateral MD lesions and also ventrolateral-thalamic damage. The findings suggest that MD contributes to recollection, with some preliminary evidence of a contribution of the medial MD to familiarity. The small sample size does, however, not yet allow any clear conclusions in this regard. Since damage in the ventrolateral thalamus leads to memory and executive dysfunction, further research is needed to elucidate the role of this thalamic region in cognition.

Brain Ischemia↗

PubMed2003

Narcolepsy: pathophysiology and neuropsychological changes.

Narcolepsy is now recognized as a distinctive disorder with specific pathophysiology and neurochemical abnormalities. Findings on the role of the neuropeptide hypocretin are opening new avenues of research and new strategies for therapy. Recently, neuropsychological and electrophysiological studies have provided evidence for reduced memory performance on standard memory tests in addition to subjective complaints of forgetfulness which may be related to changes in attentional processing. Further studies are, however, necessary to clarify the neuropsychological profile in narcolepsy. This review focuses on the recent advances in understanding narcolepsy.

Attention↗

PubMed2003

Developmental prosopagnosia: a review.

This article reviews the published literature on developmental prosopagnosia, a condition in which the ability to recognize other persons by facial information alone has never been acquired. Due to the very low incidence of this syndrome, case reports are sparse. We review the available data and suggest assessment strategies for patients suffering from developmental prosopagnosia. It is suggested that developmental prosopagnosia is not a unitary condition but rather consists of different subforms that can be dissociated on the grounds of functional impairments. On the basis of the available evidence, hypotheses about the aetiology of developmental prosopagnosia as well as about the selectivity of deficits related to face recognition are discussed.

Brain↗

PubMed2002

Differences in trace and delay visuomotor associative learning in cerebellar patients.

Recent studies revealed an impairment of patients with cerebellar lesions in cognitive associative learning paradigms, which could not be explained by motor deficits or increased attentional demands during performance of the motor part of the particular task. To further test the role of the cerebellum in cognitive associative learning a visuomotor associative learning paradigm was conducted, which showed some similarities to reflex conditioning. Subjects had to learn the association between a visual stimulus (i.e., a colored square) and a correct motor response (i.e., pressing a left or right target button on a specialized keyboard) in a stimulus-response paradigm. The correct side of the response was always indicated by a growing circle. The stimuli were presented in two forms: (1) the colored square ("conditioned stimulus", "CS") preceded the growing circle ("unconditioned stimulus", "US") and coterminated with the "US" (delay-condition) or (2) the offset of the colored square was separated from the onset of the circle by a short time interval (trace-condition). Eight patients with degenerative cerebellar disorders and eight age-, sex-, IQ-, and education level-matched controls participated. Both control subjects and cerebellar patients showed significant effects of learning based on reduction of decision times during performance of the task. The explicit knowledge of the correct motor response associated with each of the presented colors, however, was significantly better in control subjects. Furthermore, within-group comparisons revealed that control subjects performed significantly better in the trace-condition compared to the delay-condition, whereas no significant difference was obtained in the cerebellar group. Part of the findings in controls was explained by an age-related decline in the delay-condition. In addition, elderly control subjects appeared to benefit from cue-effects and timing-effects (i.e., fixed trace interval) in the trace-condition resulting in reduced decision times. Neither cue- nor timing-related effects fully accounted for differences between cerebellar patients and controls. The lack of a better performance in the trace-condition compared to the delay-condition in cerebellar patients suggests deficits in learning the stimulus-response association.

Age Factors↗

PubMed2002

Eyeblink conditioning indicates cerebellar abnormality in dyslexia.

There is increasing evidence that cerebellar deficit may be a causal factor in dyslexia. The cerebellum is considered to be the major structure involved in classical conditioning of the eyeblink response. In a direct test of cerebellar function in learning, 13 dyslexic participants (mean age 19.5 years) and 13 control participants matched for age and IQ undertook an eyeblink conditioning experiment in which for 60 acquisition trials an 800-ms auditory tone (conditioned stimulus, CS) was presented. On 70% of the trials an 80-ms corneal airpuff (unconditioned stimulus, US) was presented 720 ms after the tone onset. The cerebellar deficit hypothesis, uniquely of the causal hypotheses for dyslexia, predicts that the dyslexic participants would show abnormal performance in the incidence and/or timing of the conditioned response (CR) of an eyeblink in response to the tone (and before the US). Three of the dyslexic group showed no conditioning at all. Furthermore, the dyslexic group showed significantly worse "tuning" of the CR timing, together with significantly reduced habituation of the orienting response (OR) to the CS. Individual analyses indicated that 85% of the dyslexic group showed either no conditioning or abnormally poor CR tuning and/or abnormally low OR habituation. It is concluded that the findings provide further converging evidence of cerebellar abnormality in dyslexia and for the first time demonstrate that there are fundamental abnormalities in the way that dyslexic people learn. Equally important, the eye blink conditioning paradigm provides a method of investigating further both homogeneity and heterogeneity in the learning deficits underlying dyslexia and other developmental disorders.

Adolescent↗

PubMed2002

Dissociating prelexical and postlexical processing of affective information in the two hemispheres: effects of the stimulus presentation format.

Using a lexical decision task, the authors investigated whether brain asymmetries in the detection of emotionally negative semantic associations arise only at a perceptually discriminative stage at which lexical analysis is accurate or can already be found at crude and incomplete levels of perceptual representation at which word-nonword discrimination is based solely on guessing. Emotionally negative and neutral items were presented near perceptual threshold in the left and right visual hemifields. Word-nonword discrimination performance as well as the bias to classify a stimulus as a "word" (whether or not it actually is a word) were assessed for a normal, horizontal stimulus presentation format (Experiment 1) and for an unusual, vertical presentation format (Experiment 2). Results show that while the two hemispheres are equally able to detect affective semantic associations at a prelexical processing stage (both experiments), the right hemisphere is superior at a postlexical, perceptually discriminative stage (Experiment 2). Moreover, the findings suggest that only an unusual, nonoverlearned stimulus presentation format allows adequate assessment of the right hemisphere's lexical-semantic skills.

Adult↗

PubMed2002

Impaired processing of affective prosody in Korsakoff's syndrome.

In order to further characterize reported deficits in affect perception in alcoholic Korsakoff patients, selected prosody subtests from the Tübingen Affect Battery were administered to seven Korsakoff patients and seven normal control participants. Results indicated that both linguistic and affective prosody discrimination were intact in Korsakoff patients. As well, affective prosody identification was unimpaired when the semantic content of the sentence was emotionally congruent with affective prosody. In contrast, affective prosody identification was significantly impaired when the semantic content was either neutral or incongruent with prosody. These results suggest that Korsakoff patients are impaired in interpreting the meaning of affective prosody in the absence of semantic cues as to the emotional content of sentences.

Affect↗

PubMed2002

Perceptual learning in amnesia.

Evidence from experiments on perceptual learning, accumulated during the last few years, increasingly indicates that the relative 'front end' parts of the visual system are more plastic even in adults than was previously expected. Hence, it might be possible that perceptual learning is similar in several respects to procedural learning and may be achieved even without (declarative) memory traces present. Results on six patients suffering from global amnesia due to damage to hippocampal-diencephalic systems demonstrate, for the first time, that at least some amnesic patients are able to significantly improve performance in a visual hyperacuity task as a result of training, showing improvement as good as the observers in the control group. This result corroborates the notion of a relatively 'front end' location of at least some forms of perceptual learning.

Adult↗

PubMed2002

Speech perception deficits in Parkinson's disease: underestimation of time intervals compromises identification of durational phonetic contrasts.

Besides motor, vegetative, and cognitive signs, patients suffering from Parkinson's disease (PD) may show distinct perceptual deficits such as underestimation of time intervals extending across several seconds. Assuming this impairment also to affect the domain of tens of milliseconds, disrupted encoding of the acoustic speech signal with respect to segment durations conveying linguistic information must be expected. To test this hypothesis, 10 PD patients and matched controls performed an identification task using a series of 10 stimuli derived from the utterance "Boten" (/bo:tn/, 'messengers'; produced with nasal plosion) by exclusive manipulation of occlusion length (110-20 ms in steps of 10 ms). Under these conditions, word-medial silence cues the voicing category of the respective stop consonant. Seven PD subjects showed normal identification curves, i.e., categorized the shortest and longest stimuli with high probability each as the minimal pair cognates "Boden" and "Boten," respectively. In contrast, the remaining three patients labeled all items across the complete range of occlusion lengths as "Boden." A subsequent experiment found a horizontal shift of the identification curves toward larger signal durations (> 120 ms) in these three subjects. Bilateral cerebellar degeneration has been found to yield a different response pattern, i.e., near-chance level of performance. Considering recent information-processing models of scalar interval timing, striatal disorders seem to slow down an oscillatory pacemaker, whereas cerebellar dysfunctions may impair comparison of measured durations with stored reference memory traces.

Adult↗