Biomedical subjects

I Daum

Publications and source records attributed to I Daum.

At least 37 records · Page 2Linked to original sources

PubMed2001

Executive dysfunction in spinocerebellar ataxia type 1.

Fourteen patients with spinocerebellar ataxia 1 (SCA1) and 11 controls with similar mean age and IQ estimates were submitted to a neuropsychological test battery comprising tests for IQ, attention, verbal and visuospatial memory as well as executive functions. Neuropsychological assessment yielded verbal memory and executive dysfunction while tests of visuospatial memory and attention were not significantly impaired in SCA1 as compared to controls. Test performance was neither related to the repeat length, the age of onset nor the disease duration. The profile of cognitive impairment in SCA1 with prominent executive dysfunction corresponds to the concept of "frontal-subcortical" dementia that is likely to be contingent upon disruption of a cerebrocerebellar circuitry that consists of afferent and efferent connections between the prefrontal cortex and the cerebellum.

Adult↗

PubMed2000

Sequence learning in Parkinson's disease: a comparison of spatial-attention and number-response sequences.

The serial reaction time (SRT) task has been frequently used to assess procedural learning of sequences. Patients with Parkinson's disease (PD) have been reported to show deficits on this task, but it is as yet unclear whether this impairment reflects a general sequencing deficit or a deficit in the sequencing of motor-output responses. In order to examine this issue, PD patients and controls were administered an SRT task which allowed the simultaneous and independent assessment of the procedural learning of spatial regularities and the learning of motor-response regularities. PD patients were unimpaired at learning a sequence of spatial locations, but showed a deficit at learning a stimulus-to-motor-response sequence. The results suggest that sequencing impairments in PD are not general, but specific to the type of sequential information inherent in a task.

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PubMed2000

The effect of semantic categorisation on recall memory in amnesia.

Amnesic patients were compared to a healthy control group on recall of word lists containing semantically-related or unrelated words. As expected on the basis of previous literature, the amnesic group performed below the control group on all measures of recall. When total recall scores for each list were used as the index of performance, their scores were not significantly affected by the type of list, unlike those of the control group. Comparison of serial position effects for different parts of the lists revealed that the control group derived greater benefit from semantic relatedness in recall of items from the middle positions. This effect was not shown by the amnesic group, who showed similar U-shaped serial position curves for recall of all three lists, and appeared to use a more passive recall strategy than the control group. The findings are discussed in relation to our current understanding of amnesic deficits.

Journal Article↗

PubMed1999

Long-term retention of classical eyeblink conditioning in amnesia.

The retention of classical eyeblink conditioning was investigated in amnesic patients 10 days and 2 months after original learning. During reacquisition, the first CR occurred earlier and the CR frequencies during the first 10 trials were higher than in the baseline session. The overall CR rates increased significantly across sessions during both acquisition and extinction. The amnesics did not differ from matched controls on any of these effects, although they did not recall previous conditioning sessions and did not become fully aware of CS-US contingencies. The smaller number of electrodermal responses to the CS tone during extinction in the amnesics may relate to their lack of insight into the change in the reinforcement schedule.

Amnesia↗

PubMed1999

Phonemic vowel length contrasts in cerebellar disorders.

Apraxia of speech and Broca's aphasia both affect voice onset time (VOT) whereas phonemic vowel length distinctions seem to be preserved. Assuming a close cooperation of anterior perisylvian language zones and the cerebellum with respect to speech timing, a similar profile of segment durations must be expected in ataxic dysarthria. In order to test this hypothesis, patients with cerebellar atrophy or cerebellar ischemia were asked to produce sentence utterances including either one of the German lexial items "Rate" (/ra:t(h)e/, 'installment'), "Ratte" (/rat(h)e/, 'rat'), "Gram" (/gra:m/, 'grief'), "Gramm" (/gram/, 'gramm'), "Taten" (/t(h)atn/, 'actions'), or "Daten" (/datn/, 'data'). At the acoustic signal, the duration of the target vowels /a/ and /a:/ as well as the VOT of the word-initial alveolar stops /d/ and /t/ were determined. In addition, a master tape comprising the target words from patients and controls in randomized order was played to three listeners for perceptual evaluation. In accordance with a previous study, first, the cerebellar subjects presented with a reduced categorical separation of the VOT of voiced and unvoiced stop consonants. Second, vowel length distinctions were only compromised in case of the minimal pair "Gram"/"Gramm." In contrast to "Rate"/"Ratte", production of the former lexical items requires coordination of several orofacial structures. Disruption of vowel length contrasts would, thus, depend upon the complexity of the underlying articulatory pattern.

Adult↗

PubMed1999

Cerebellar contributions to the perception of temporal cues within the speech and nonspeech domain.

A previous study (Ackermann, Gräber, Hertrich, & Daum, 1997) reported impaired phoneme identification in cerebellar disorders, provided that categorization depended on temporal cues. In order to further clarify the underlying mechanism of the observed deficit, the present study performed a discrimination and identification task in cerebellar patients using two-tone sequences of variable pause length. Cerebellar dysfunctions were found to compromise the discrimination of time intervals extending in duration from 10 to 150 ms, a range covering the length of acoustic speech segments. In contrast, categorization of the same stimuli as a "short" or "long pause" turned out to be unimpaired. These findings, along with the data of the previous investigation, indicate, first, that the cerebellum participates in the perceptual processing of speech and nonspeech stimuli and, second, that this organ might act as a back-up mechanism, extending the storage capacities of the "auditory analyzer" extracting temporal cues from acoustic signals.

Adult↗

PubMed1999

Cognitive deficits in spinocerebellar ataxia 2.

This is one of the first studies assessing the pattern of cognitive impairment in spinocerebellar ataxia 2 (SCA2). Cognitive function was studied in 17 patients with genetically confirmed SCA2 and 15 age- and IQ- matched controls using a neuropsychological test battery comprising tests for IQ, attention, verbal and visuospatial memory, as well as executive functions. Twenty-five percent of the SCA2 subjects showed evidence of dementia. Even in non-demented SCA2 subjects, there was evidence of verbal memory and executive dysfunction. Tests of visuospatial memory and attention were not significantly impaired in the non-demented group compared with controls. There was no relationship between test performance and motor disability, repeat length or age of onset, while disease duration was shown to be inversely correlated with two tests reflecting the progression of cognitive deficits during the course of the disease. Intellectual impairment should therefore not be interpreted as a secondary effect of progressive motor disability, but represents an important and independent part of the SCA2 phenotype.

Adult↗

PubMed1998

Does the cerebellum contribute to cognitive aspects of speech production? A functional magnetic resonance imaging (fMRI) study in humans.

Several positron emission tomography (PET) studies suggest a contribution of the lateral aspects of the right cerebellar hemisphere to higher-level (cognitive) aspects of speech production such as controlled verbal response selection. As an alternative, however, 'inner speech', giving rise to subliminal activity of orofacial and laryngeal muscles, might account for the observed activation effects. Eighteen subjects underwent functional magnetic resonance imaging (fMRI) during continuous silent recitation of the names of the months of the year ('automatic speech'). The right cerebellar hemisphere showed a significantly increased hemodynamic response concomitant with, among others, an asymmetric activation pattern towards the left side at the level of the motor strip. Since highly overlearned word strings, presumably, pose few demands on controlled response selection and since the projections of the right cerebellar hemisphere to the left precentral gyrus participate in motor control, the observed cerebellar activation, thus, seems to be related to the articulatory level of speech production rather than, as suggested by previous PET studies, to cognitive operations.

Adult↗

PubMed1997

Categorical speech perception in cerebellar disorders.

Keele and Ivry (1991) considered the cerebellum an "internal clock" responsible for temporal computations both in the motor and in the perceptual domain. These authors, therefore, expected that the processing of durational parameters of the perceived acoustic speech signal such as voice onset time (VOT) depends upon the cerebellum as well. However, a preliminary investigation of Ivry and Gopal (1992) revealed unimpaired phoneme-boundary effects in cerebellar patients along a continuum of monosyllabic stimuli with systematically varied VOT (/ba/-/pa/). Since the energy of the aspiration noise provides additional cues for the discrimination of voiced and voiceless stops, the present study used a series of disyllabic stimuli differing in a purely durational parameter. Both controls and patients with unilateral cerebellar lesion identified the endpoints of this continuum in nearly all instances as the counterparts of a minimal pair (Boten, /bo:tn/, "messengers" versus Boden, /bo:dn/, "floor"). Subjects with bilateral pathology of the cerebellum, in contrast, did not show a comparable phoneme-boundary effect. Our data corroborate the hypothesis of the cerebellum as an internal clock and implicate a role of this structure in speech perception.

Adult↗

PubMed1997

The NMDA antagonist memantine impairs classical eyeblink conditioning in humans.

The present study investigated the effects of a single oral dose (30 mg) of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist memantine on memory and learning in human subjects. Sixteen male healthy volunteers participated in a double blind placebo controlled study. There were no significant effects of memantine on mood, attention or immediate and delayed verbal and visuospatial memory. Memantine did, however, delay the acquisition of classical eyeblink conditioning and reduced the overall frequency of conditioned responses without affecting reflex or spontaneous eyeblinks. These findings are compatible with the higher affinity of memantine to cerebellar as compared to forebrain tissue and demonstrate the dissociability of different memory systems by pharmacological tools.

Adult↗

PubMed1997

Kinematic analysis of articulatory movements in central motor disorders.

The various components of the central motor system are expected to play a similar role in speech production and in upper limb control. Slowed articulatory performance, therefore, must be expected in disorders of the corticobulbar tracts, cerebellum, and basal ganglia. Using an optoelectronic device, the present study recorded lower lip trajectories during production of sentence utterances in patients with Parkinson's disease (PD), Huntington's disease (HD), cerebellar atrophy (CA), and pseudobulbar palsy (PB). The various subject groups showed a similar range of overall motor disability. Patients with CA and PB exhibited slowed movement execution in terms of a reduced ratio of peak velocity to maximum amplitude ("stiffness"). In contrast to upper limb motor control, the lip excursions showed an uncompromised shape of velocity profiles. Two different patterns emerged in HD. A single patient suffering from the akinetic-rigid Westphal variant of this disease had articulatory hypometria, whereas the remaining subjects showed significant bradykinesia under increased temporal demands, concomitant with normal movement amplitudes. The PD patients had unimpaired velocity-displacement relationships. Presumably, biomechanical constraints such as the rather small excursions of articulatory lower lip gestures or the scarce spindle supply of facial muscles account for the observed discrepancies between upper limb and speech motor control in PD.

Aged↗

PubMed1997

The relationship between retrograde and anterograde amnesia in patients with typical global amnesia.

An extensive battery of tests of anterograde amnesia and remote memory was given to ten amnesics with lesions either to the medial temporal lobes of the diencephalon. These showed that the patients had anterograde amnesia with deficits in verbal and non-verbal recall and recognition, but preservation of word stem completion and intelligence. Mild impairments on executive tests and digit span performance were largely caused by the poor performance of the Korsakoff patients. The amnesics also showed remote memory deficits for personal and public domain information, and temporal gradients were observed for some of the tests. These deficits probably arose because the patients' anterograde amnesia was more severe than their retrograde amnesia even for the recent pre-morbid past. They were more impaired in the recall of details about famous names in their ability to recognize such names. There was also a suggestion that performance on anterograde tests did not relate strongly to that on tests of retrograde amnesia of the remote pre-morbid past. However, this effect was less apparent with memory for personal information when the format and the information tapped were matched on pre- and post-morbid tests.

Adult↗

PubMed1997

Visual learning and memory as functions of age.

Age-related changes have been reported for a range of perceptual and cognitive functions. We investigated visual acuity and vernier acuity, as well as visual memory and learning, in four age groups, each comprising 10 subjects and ranging from adolescence to an age group up to 66 years. The groups were matched on general abilities for visuospatial information processing. Visual acuity decreased slightly with increasing age. The reproduction of more complex geometrical material which exceeded short-term memory capacities was significantly impaired in the oldest group relative to young adults. However, vernier acuity thresholds and improvement of thresholds with training did not differ in the four groups. Short-term retention of visual stimuli across 1 or 4 sec was also comparable in the different age groups. Those visual abilities that are limited primarily by cortical, not retinal, factors remained relatively unchanged in our observers despite age-related changes in the eye. Visual memory functions which tap working and long-term memory abilities, on the other hand, showed a significant age-associated decline during adulthood.

Adult↗

PubMed1997

Neuropsychological abnormalities in cerebellar syndromes--fact or fiction?

In recent years, theoretical considerations and a large number of empirical investigations have been published in support of a cerebellar involvement in cognitive processing. This chapter aims at a critical evaluation of the neuropsychological findings from clinical studies of patients with cerebellar syndromes. The discussion will mainly consider data from patients with selective cerebellar dysfunction, as data from patients with combined cerebellar and extracerebellar damage are of limited value for the issue of a cerebellar involvement in cognition. Early clinical observations indicated that degenerative diseases or selective cerebellar lesions did not necessarily give rise to general intellectual impairment such as dementia. Recent neuropsychological evidence based on standardized testing does not yet provide a clear picture. Deficits in motor learning or temporal processing are consistently observed in patients with cerebellar syndromes, while the cerebellum does not appear to be critically involved in general intellectual capacities or memory. Deficits in frontal lobe function, visuospatial processing or nonmotor skill learning have been reported in several studies, but have not been replicated in others. Such discrepancies may relate to a number of methodological problems. Future neuropsychological studies should take such methodological issues into account by using patients with selective cerebellar dysfunction, adequately matched clinical and non-clinical comparison groups, and theory-driven iesl batteries comprising a wide range of tests.

Animals↗

PubMed1997

[Nondeclarative memory--neuropsychological findings and neuroanatomic principles].

The contents of long-term memory will influence behaviour, even if the acquired knowledge or the original learning episode are not remembered. These phenomena have been termed "non-declarative" or "implicit" memory, and they are contrasted with "declarative" or "explicit" memory which is characterised by conscious search and retrieval procedures. Non-declarative memory encompasses non-associative learning, simple conditioning, priming effects as well as motor, perceptual and cognitive skill acquisition. The dissociation of both forms of memory is documented by studies in health subjects which indicated that experimental manipulations or drugs may differentially affect declarative and non-declarative memory processes. Damage to the medial temporal or the medial thalamic regions is known to result in declarative memory deficits whereas non-declarative memory is largely unaffected by such lesions. Animal research and clinical findings indicate that several components of non-declarative memory such as motor and cognitive skill acquisition or certain types of classical conditioning are dependent upon the integrity of the basal ganglia or the cerebellum. These issues are therefore of increasing importance for the understanding of extrapyramidal and cerebellar diseases. This paper presents recent neuropsychological findings and neuroanatomical data relating to the issue of non-declarative memory.

Animals↗

PubMed1996

Memory dysfunction of the frontal type in normal ageing.

In this study healthy subjects divided into five consecutive age groups (20-60 years of age) completed a series of memory tasks which had previously been shown to reveal impairments in patients with frontal lobe lesions. Significant age differences were found for free recall, retention rates for material which required effortful encoding, memory for temporal order and prospective memory. In the tests addressing these memory functions, subjects of more than 60 years of age performed more poorly than the youngest group, and they also showed evidence of false recognition (increased false alarm rates and confabulatory responses). The general pattern suggests that inefficient frontal functioning might contribute to age-related memory problems.

Adult↗

PubMed1996

Classical eyeblink conditioning in Parkinson's disease.

Patients with Parkinson's disease (PD) show impairments of a range of motor learning tasks, including tracking or serial reaction time task learning. Our study investigated whether such deficits would also be seen on a simple type of motor learning, classic conditioning of the eyeblink response. Medicated and unmediated patients with PD showed intact unconditioned eyeblink responses and significant learning across acquisition; the learning rates did not differ from those of healthy control subjects. The overall frequency of conditioned responses was significantly higher in the medicated patients with PD relative to control subjects, and there was also some evidence of facilitation in the unmedicated patients with PD. Conditioning of electrodermal and electrocortical responses was comparable in all groups. The findings are discussed in terms of enhanced excitability of brainstem pathways in PD and of the involvement of different neuronal circuits in different types of motor learning.

Adult↗

PubMed1996

Semantic memory impairment in Alzheimer's disease.

The present study investigated semantic memory and the presence of category-specific impairments in patients with dementia of the Alzheimer's type (DAT). Patients in advanced stages of Parkinson's disease (PD) and matched control subjects served as comparison groups. Semantic memory was assessed by a range of verbal and visual tasks and by direct and indirect memory tests. The DAT patients showed severe deficits on all semantic knowledge tasks. Performance was poorer on animate relative to inanimate items, on naming with and without cues, and on semantic knowledge probes, indicating a category-specific knowledge loss on these tasks. Indirect memory tests yielded significantly better preservation of knowledge compared to the traditional semantic memory tasks. Analyses of the nature of the semantic breakdown in DAT suggested combined storage and access deficits and a disturbance of the structural description and phonological output systems.

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