Biomedical subjects

I Daum

Publications and source records attributed to I Daum.

At least 55 records · Page 3Linked to original sources

PubMed1996

Impaired procedural learning after damage to the left supplementary motor area (SMA).

Two paradigms of procedural learning, serial reaction time and tracking tasks, were given to a patient with damage to the supplementary motor area (SMA) of the left mesiofrontal cortex. This patient exhibited impaired procedural learning during the serial reaction time test and mirror reversed tracking. Unreversed tracking performance was normal. Therefore the SMA--as well as the cerebellum and the striatum--participate in the development of skills requiring internal elaboration of motor behaviour.

Adult↗

PubMed1995

Pain-related cerebral potentials in patients with frontal or parietal lobe lesions.

The present study investigated the processing of painful electrical stimuli in patients with unilateral frontal or parietal lobe damage and matched control subjects. Patients with frontal lesions showed increased pain thresholds when the stimuli were administered contralateral to the lesion. While the peak-to-peak amplitudes of the N150/P250 components of the somatosensory potentials increased linearly with stimulus intensity in the control subjects, the responses in the frontal group did not change significantly between stimulation at pain and tolerance threshold. There was no evidence for altered pain processing in patients with parietal lobe lesions. The findings of the present study support the hypothesis of an involvement of the frontal cortex in pain perception in humans.

Adult↗

PubMed1995

Cerebellar contributions to cognition.

This review summarises the present evidence for the contribution of the cerebellum to cognition. While a data base from both animal and human clinical research supports the hypothesis of an important cerebellar role in motor adaptation, motor learning and timing, the evidence for the implication of the cerebellum in psychopathology and non-motor cognitive functions is incomplete and does not allow unequivocal conclusions. Methodological shortcomings and the lack of theoretical models on the nature of the cerebellar contribution to cognition limit the interpretation of the empirical studies available so far.

Animals↗

PubMed1995

Memory and skill acquisition in Parkinson's disease and frontal lobe dysfunction.

Animal experiments and human neuropsychological studies have provided evidence for the hypothesis that skill acquisition may be regulated by the basal ganglia. In the present studies, perceptual and cognitive skill acquisition as well as a number of explicit verbal memory functions were investigated in patients in early and more advanced stages of Parkinson's disease (PD) and in patients with frontal lobe lesions. Patients in more advanced stages of PD were impaired at cognitive skill acquisition as well as during recall conditions that involved active semantic organisation of the stimulus material. Similar explicit memory deficits were present in frontally lesioned patients. PD patients with unilateral symptoms showed a selective impairment in acquiring a cognitive skill. Perceptual skill acquisition was preserved in all groups. The overall pattern of memory impairment in PD is largely consistent with dysfunction of fronto-striatal circuitry.

Corpus Striatum↗

PubMed1995

[The cerebellum and cognition--psychopathological, neuropsychological and neuroradiological findings].

It is a classical topic of clinical neurology that cerebellar dysfunctions give rise to motor deficits but spare the sensory and mental domains. Since the last century, however, cognitive decline occasionally has been attributed to diseases and lesions of the cerebellum. In recent years this assumption has gained in importance. The recent literature puts forward four arguments in favour of this suggestion: a) The neocerebellum has large reciprocal fibre connections with the association areas of the cerebral cortex. b) Functional imaging studies revealed activation of circumscript cerebellar regions during cognitive tasks. c) Patients with cerebellar malformations and diseases, respectively, may present with psychopathological signs and neuropsychological deficits. d) Atrophy of the cerebellum has been reported in schizophrenic and autistic syndromes. The present review aims at a critical evaluation of the relevant clinical and neuropsychological literature. So far there is no convincing evidence that lesions and diseases restricted to the cerebellum give rise to dementia or to impaired verbal and visual memory functions. With respect to specific perceptual tasks such as the discrimination of time intervals, problem solving, and visuospatial functions, no definite conclusion is possible so far. Some studies revealed cerebellar atrophy in schizophrenic and autistic patients. However, the functional relevance of these findings must be questioned since cytoarchitectonic alterations in extracerebellar areas, e.g. the basal forebrain, are present in these disorders as well.

Brain Damage, Chronic↗

PubMed1994

Category-specific semantic impairment in Alzheimer's disease and temporal lobe dysfunction: a comparative study.

In this paper we report an in-depth case study of a patient suffering from Alzheimer's disease who presented with a category-specific disorder relating to processing of knowledge about animate objects in the presence of spared knowledge of inanimate objects. Impairments appeared not only in a confrontation naming task but also on a range of visual knowledge tasks, such as drawing from memory or part-whole matching. The pattern of impairment was compared to that shown by a post-encephalitic patient who manifested a well-documented category-specific deficit for animate objects. Both patients' performance was compatible with an interpretation in terms of impairment at the level of the structural description of objects within the semantic system, as general encyclopaedic knowledge was largely preserved. Temporal lobe damage may be the cause of memory breakdown in both patients.

Adult↗

PubMed1994

Frontal-type memory impairment associated with thalamic damage.

The present case report adds further evidence to the hypothesis that material-specific memory problems arise from unilateral thalamic damage and that frontal cortical dysfunction may affect the nature of the memory disorder. A 64-year old patient who had suffered an ischemic lesion limited to the right anterior thalamus showed marked deficits in immediate and delayed recall of visuospatial material and face recognition. In addition, there was evidence of frontal-type memory problems including impaired spatial working memory, increased forgetting rates, poor prospective memory and inadequate elaborative encoding. Concomitant behavioral changes characterized by increased irritability and disinhibition also supported the hypothesis of frontal lobe dysfunction after thalamic damage.

Brain Diseases↗

PubMed1994

Dissociation of declarative and nondeclarative memory after bilateral thalamic lesions: a case report.

The case of a 63-year-old woman who suffered bilateral ischemic damage in the region of blood supply of the paramedian thalamic arteries is reported. She displayed severe deficits on immediate and delayed recall of both verbal and visuospatial material in the presence of intact IQ and attentional abilities. Performance on tests of all major components of nondeclarative memory (skill acquisition, perceptual priming, classical conditioning) was also preserved. The present report, thus, provides a further example for dissociations of declarative and nondeclarative memory functions following bilateral thalamic damage.

Conditioning, Classical↗

PubMed1993

Proximal and distal reaction times (RTs) are not differentially affected in Parkinson's disease.

The hypothesis was tested that proximal and distal reaction times (RTs) might be differentially affected in Parkinson's disease (PD). Twelve patients with PD were compared with 12 age-matched healthy controls on tests of finger-, hand-, leg-, and torso-RTs. Patients were significantly slower in initiating all movements and were slower in executing all movements except for the leg (stepping) task. Choice- versus simple-RTs were also not differentially affected in the PD group. In the healthy subjects, age was significantly positively correlated with response initiation times (RITs) but not with movement times (MTs).

Aged↗

PubMed1993

Cortical self-regulation in patients with epilepsies.

The present study aimed at investigating to what extent the regulation of excitability in cortical networks, as indicated by surface-negative slow cortical potentials (SCPs), is impaired in epileptic patients and to what extent training of SCP self-regulation by means of biofeedback and instrumental learning procedures might affect seizure frequency. Twenty-five patients suffering from drug-refractory epilepsies (complex focal, grand mal, and absence type of seizures) participated in 28 1-h sessions of feedback and instrumental conditioning of their SCPs. Subjects' EEGs were obtained from the vertex. Depending on discriminative stimuli DC shifts towards increased or suppressed negativity relative to the pre-trial baseline were demonstrated by on-line visual feedback during intervals of 8 s each; each session comprised 110 trials. While performance on the SCP self-regulation task was initially below normal (as compared to healthy subjects), significant increases in SCP control were achieved by the patients across the 28 training sessions. In 18 patients at least 1-year follow-up data are available. Changes in seizure frequency were related to transfer of SCP control with six of the patients becoming seizure-free. Age affected the ability to acquire SCP control and its impact on seizure frequency.

Adolescent↗

PubMed1993

Operant conditioning after temporal lobe lesions in man: conditional and simple discrimination learning.

Temporal lobe lesions have been found to impair the acquisition of classical conditional discrimination learning in an eyelid conditioning paradigm, with sparing of simple eyelid conditioning. In the present study, subjects with left or right temporal resections were compared with normal controls on two operant conditioning tasks using a conditional and a simple discrimination paradigm analogous to the previously reported classical conditioning tasks. Subjects with right temporal lesions, and to a lesser extent those with left temporal lesions, were impaired relative to frontal lobe and control subjects in the acquisition of a conditional discrimination within an operant conditioning setting. A subsequent experiment showed that both left and right temporal lobe subjects were unimpaired on a simple operant discrimination task. These findings are compatible with theory relating hippocampal function to the learning of if-then rules.

Adult↗

PubMed1993

The cerebellum and cognitive functions in humans.

Recent neuropsychological studies have given rise to the hypothesis that the cerebellum is involved in nonmotor cognitive functions. The interpretation of these findings is, however, restricted by methodological problems, such as heterogenous patient samples. The present study compared patients with pathology confined to the cerebellum and patients with combined cerebellar and brainstem lesions to matched normal controls on a range of memory and learning tasks. Two procedural learning tasks were also conducted, involving perceptual (mirror reading) and conceptual skill acquisition (the Tower of Hanoi task). Patients with damage to both cerebellum and brainstem, but not patients with cerebellar pathology alone, showed impairments on memory and visuoconstructive tasks and evidence of frontal lobe dysfunction. Cerebellar damage had no effect on skill acquisition. These results do not support the hypothesis of cerebellar involvement in procedural learning per se.

Adult↗

PubMed1993

Classical conditioning after cerebellar lesions in humans.

We explored classical conditioning in human subjects who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control subjects underwent simple delay tone-airpuff conditioning. Eyelid conditioned response (CR) acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between conditioned stimulus (CS) and the unconditioned stimulus (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.

Adult↗

PubMed1993

Behavioural treatment of slow cortical potentials in intractable epilepsy: neuropsychological predictors of outcome.

The study aimed to explore the predictive value of neuropsychological tests within the context of acquisition of slow cortical potential (SCP) self-control, a technique which has beneficial effects on seizure frequency in epilepsy. Patients with epilepsy who successfully achieved SCP control had longer digit or block-tapping spans than less successful patients. Patients who showed a better learning rate across training also displayed better verbal memory and learning abilities. Seizure reduction was related to block-tapping spans only. The results indicate that measures of attention, as indicated by digit spans or block-tapping spans, offer some predictive value for acquisition of SCP control and treatment outcome, whilst measures of visuospatial or frontal lobe function are unrelated to SCP acquisition and seizure reduction.

Adolescent↗

PubMed1992

Classical conditioning after temporal lobe lesions in man: sparing of simple discrimination and extinction.

Recent reports of impaired conditional discrimination learning in temporal lobectomy subjects have raised the question of response inhibition deficits in these patients. In the present study, left and right temporal lobectomy subjects and healthy controls completed an eyelid conditioning task, which required simple two-tone discrimination learning, followed by extinction. There were no group differences with regard to discrimination learning or extinction. General deficits in response inhibition are therefore not likely to account for the impairment in conditional discrimination observed in temporal lobectomy patients.

Acoustic Stimulation↗

PubMed1992

The Maudsley Mentation test: a method for extended monitoring of mental status after aneurysmal subarachnoid hemorrhage.

A new scale for the repeated, rapid assessment of mental function in patients with subarachnoid hemorrhage is described. Its reproducibility is evaluated and early experience with its use in the intended clinical setting is reported. The test (Maudsley Mentation Test) proved to be more sensitive to fluctuations in cerebral functioning than existing measures of conscious level, and the results were reproducible among observers with different backgrounds (surgeons, nurses, and psychologists). The results suggest a relationship between performance on mentation testing and quality of outcome. The Maudsley Mentation Test is thought to offer a suitable measure with which to monitor patients during the acute phase of their illness to supplement clinical assessment and provide evidence of deterioration at an early stage. It is also potentially useful as an end point in acute protection and treatment studies.

Adult↗

PubMed1991

Incidence and clinical risk factors for bleeding and thrombotic complications in myeloproliferative disorders. A retrospective analysis of 260 patients.

Bleeding and thrombosis are frequent complications in myeloproliferative disorders (MPD) and are associated with severe organ damage and a high mortality. Elevated platelet count, elevated hematocrit, and patient age are regarded as risk factors for bleeding and thromboembolic events in MPD, although the significance of these parameters was not confirmed by clinical studies. We retrospectively analyzed vascular complications in 260 patients with MPD and tried to identify parameters predictive for bleeding and thrombembolic events. Our cohort consisted of 115 patients with chronic myeloid leukemia (CML), 84 patients with polycythemia vera (PV), 26 with essential thrombocythemia (ET), 25 with osteomyelofibrosis (OMF), and 10 patients with unclassifiable MPD. During a median follow-up period of 31 months, 126 patients with chronic MPD suffered bleeding or thrombotic events. Bleeding was observed in 57% of patients with OMF, 23% with PV, 20% with chronic phase CML, and 16% with ET. Thrombotic events were most common in patients with PV (36% of patients), followed by ET, OMF, and chronic phase CML (20%, 17%, and 6% of patients, respectively). Recurrent thrombotic episodes frequently occurred in patients with PV and ET, whereas patients with OMF often had more than one bleeding event. Thirty patients died of thrombohemorrhagic complications during follow-up. Multivariate analysis, including all patients with chronic MPD, revealed that elevated red blood cell count, higher hemoglobin level, and increased percentage of segmented neutrophils at the time of diagnosis were associated with thrombosis, whereas patients with bleeding complications were characterized by low red cell count, lower hemoglobin, and a lower percentage of segmented neutrophils. However, when analyzed by MPD subgroup, none of these parameters retained a predictive value for bleeding or thrombotic events. Moreover, elevated platelet count and patient age were not risk factors for bleeding complications. Thrombotic events were less frequent in patients below the age of 40, and were increased in patients aged 70 and above. However, this was primarily due to the high percentage of elderly patients in subgroups mainly affected by thrombosis (PV and ET). In most MPD subgroups, the rate of bleeding and thrombosis was highest just before and during the first months after diagnosis, and declined thereafter. Thrombohemorrhagic complications were less frequent after phlebotomy in PV and after therapy with alkylating agents in CML. The institution of cytoreductive therapy soon after the diagnosis was made may explain the reduced incidence of complications later in the disease. We conclude that morbidity and mortality from thrombohemorrhagic complications are high in myeloproliferative disorders.(ABSTRACT TRUNCATED AT 400 WORDS)

Bloodletting↗

PubMed1991

T-maze discrimination and reversal learning after unilateral temporal or frontal lobe lesions in man.

The interpretation of conditional discrimination and reversal learning as acquisition of declarative knowledge suggests that subjects with temporal lobe/hippocampal lesions are likely to be impaired on such tasks. Patients with unilateral left or right temporal lobectomy (and small hippocampal excisions) and patients with unilateral frontal lobe resections were compared with healthy controls on a discrimination reversal task, embedded in a computer game modelled on T-maze tasks traditionally used in animal experiments. The right temporal group showed a deficit in acquiring an initial conditional discrimination, and the frontal group tended to display a marginal impairment in discrimination reversal. These findings are compared with results from animal studies in terms of the mechanisms underlying reversal learning.

Adult↗