PubMed Health⌕ Search

Biomedical subjects

H F Durwen

Publications and source records attributed to H F Durwen.

At least 19 recordsLinked to original sources
PubMed2001

[Word generation in bilinguals--fMRI study with implications for language and memory processes].

For over a century the cerebral representation of language functions is a matter of debate. In Neuroscience language is regarded as one of the most lateralized cognitive functions. Thus, while the language which is acquired first in most cases is processed by the left hemisphere some studies in brain damaged but also experimental investigations propose a pivotal role of the right hemisphere in second language processing. By the advent of modern neuroimaging it is now possible to study language lateralization and bilinguality also in healthy subjects. We studied first and second language abilities in a group of bilingual, healthy individuals by means of functional magnetic resonance imaging (fMRI) with a word-fluency paradigm. While we found a predominantly left prefrontal activity during both first and also second language processing an additional right prefrontal activation was registered during the use of second language. Our findings are discussed on the basis of an interaction between language and memory processes.

Adult↗
PubMed1999

Retrograde amnesia for world knowledge and preserved memory for autobiographic events. A case report.

A patient (PC) with severe and chronic retrograde amnesia for world knowledge (tested with famous events and famous faces), but unimpaired autobiographical memory is described. The 64-year-old man had traumatic brain injury four years prior to the present evaluation. Current brain imaging showed principally damage involving the infero-lateral prefrontal and the lateral temporal regions of the left-hemisphere. PC was of average intelligence, had no depression and only minor language problems, but manifested some additional anterograde memory deficits and performed subaverage in various frontal lobe-sensitive tests. Patient PC represents one of the very few cases with a preserved retrograde episodic and an impaired retrograde knowledge system, showing a dissociation between preserved retrieval of autobiographical events and amnesia for nonpersonal famous events. It is hypothesized that the sparing of autobiographical memories can be linked to the integrity of the right frontal and temporo-polar cortices.

Amnesia, Retrograde↗
PubMed1997

Impaired episodic memory retrieval in a case of probable psychogenic amnesia.

A patient with severe, selective retrograde amnesia for personal material diagnosed as probable psychogenic amnesia, was investigated intensively neuropsychologically with cranial computed tomography (CCT), magnetic resonance imaging (MRI), and single photon emission tomography (SPECT). The patient was of average intelligence and memory with no anterograde amnesia. No evidence for structural brain damage was detected in CCT and MRI. SPECT, performed about 3 weeks after the onset of symptoms, demonstrated reduced perfusion in right temporal and frontal areas, that is, in areas which have been suggested as critical for episodic memory retrieval. To study episodic memory retrieval, positron-emission-tomography (PET) blood flow (rCBF) measurements were performed 6 months after the onset of symptoms. During episodic memory retrieval bilateral neuronal activations were observed in the precuneus, the lateral parietal and the right dorsolateral and polar prefrontal cortex. Compared to the results of previous functional imaging studies on episodic memory retrieval, our findings suggest an underlying functional disturbance of brain areas previously demonstrated to be involved in episodic memory retrieval.

Adult↗
PubMed1996

Right temporofrontal cortex as critical locus for the ecphory of old episodic memories.

A 54 year old patient of average intelligence with a severe and enduring loss of old autobiographical memories after herpes simplex type 1 infection is described. She was tested with a comprehensive neuropsychological battery two years after the infection. Special emphasis was laid on examining different aspects of retrograde memory. The neurological examination involved MRI and SPECT. Brain damage was found mainly in the right temporofrontal region, but minor left sided damage to this region seems possible. The patient was in the normal or slightly subnormal range for all tested anterograde memory functions, but manifested severe retrograde memory deficits with respect to episodic old memories and more moderate deficits in tests of general knowledge (semantic old memories). It is concluded that the ecphory of old autobiographical memories relies heavily on an activation of the right lateral temporofrontal junction area, but that probably only some complementary left hemispheric damage to these regions will lead to major and persistent retrograde amnesia. Alternatively, the disconnection between major prefrontal and posterior cortical regions may provide a basis for retrograde amnesia.

Amnesia, Retrograde↗
PubMed1995

[Neuropsychological aspects in idiopathic Parkinson disease].

Patients with Parkinson's disease can suffer from neuropsychological deficits which, in most cases, are already demonstrated at the very beginning (53). Primarily, they are characterized by impairments associated with frontal lobe function affecting psychomotor speed and mental flexibility. Furthermore they show circumscribed impairment of memory functions as well as deficits of visuospatial information processing. Sets of neuropsychological dysfunction of that kind are called subcortical dementia in the American literature. In addition, Parkinson's disease is quite often associated with depressive states which are independent of the neuropsychological deficits. Application of L-Dopa helps to improve the cognitive impairment.

Aged↗
PubMed1994

The amygdala's contribution to memory--a study on two patients with Urbach-Wiethe disease.

The consequences of primary amygdaloid damage on memory performance are described in terms of neuropsychological, CT, MRI and PET results of two patients, a brother and a sister. Both had circumscribed, bilaterally symmetrical damage confined to the amygdaloid region, while the hippocampal formation and other brain structures were intact. PET-imaging furthermore revealed an overall decrease in glucose metabolism which was particularly apparent at the cingular and thalamic levels. Although neither patient was amnesic, both showed memory impairments in selective tests. In one patient these impairments were more pronounced and they were accompanied by marked affective-emotional fluctuations. Our results suggest that the amygdaloid region is a bottle-neck structure that confers an affective flavour to memories, thereby enhancing the probability of their long term storage.

Adult↗
PubMed1994

Left hemispheric neuronal heterotopia: a PET, MRI, EEG, and neuropsychological investigation of a university student.

A 21-year-old left-handed medical student had a prominent unilateral cerebral cortical malformation due to an ontogenetic migration disorder. We performed neuropsychological studies, EEG, T1- and T2-weighted and proton-density MRI, and positron emission tomography (PET) (under both the resting condition and neuropsychological activation). Neuropsychological testing revealed normal intelligence and generally normal memory functioning but selective deficits in tests of verbal fluency and spatial-figural relationships. Proton-density and T2-weighted MRI revealed extensive left cortical heterotopia that included parts of the Wernicke area. PET under the resting condition revealed a small interhemispheric difference with slightly reduced glucose metabolism in the left temporoparietal cortical zone. An activation PET (with the patient performing a verbal fluency test) resulted in a normal overall increase in metabolism but marked deviations in cortical areas. The highest activity changes were in the Broca and Wernicke areas of the right hemisphere, and there was very little activation in those regions of the left hemisphere that were expected to respond well to the activation--the temporal, parietal, and temporo-occipital cortical zones. We conclude that there can be large compensations for unilateral heterotopia.

Adult↗
PubMed1993

[Medical, psychosocial rehabilitation and prevention in patients with epilepsy].

Patients suffering from epilepsy and quite frequently reversible impairment of personality and individual development are in need of specific, disease-related measures of rehabilitation. Particularly, the complexity of the disorder prevents from a responsible and successful self-management. In order to obtain effective rehabilitation and reintegration into all aspects of social life it is essential to initiate a comprehensive treatment plan for the patients at the earliest possible stage considering personality, the distinct form of seizures, education and training as well as the condition of the environment. It requires various programs of precise examination and preventive treatment at specific facilities to ensure the desired success of rehabilitation. Thus multiple social disadvantages as well as unnecessary longterm costs may be avoided and mainly that kind of therapy will result in a better life quality and prolonged life expectancy for the epileptic patients.

Adaptation, Psychological↗
PubMed1993

Searching for the anatomical basis of retrograde amnesia.

The case of a patient with profound retrograde and minor anterograde amnesia is described and used to discuss the kind of brain damage which will most likely result in persistent retrograde amnesia as the principal symptom. The patient was an industrial manager who had fallen off a horse four years prior to the present neuropsychological and neuroradiological investigation. MRI examination revealed an injury to both temporal poles and to the latero-ventral portion of the right prefrontal cortex. The prefrontal and temporal cortical damage on the right side deeply invaded the white matter while the temporal cortical damage on the left side was much smaller; here, however, portions of the temporo-parietal transition zone were affected as well. The patient was of average intelligence. His attention, short-term memory, and learning ability were average or somewhat below average. His old memories were severely affected in the personal-episodic domain, and much less so in that of semantic remote memory. We conclude from this case that the necessary anatomical substrate for the retrieval of old episodic memories lies within the anterior temporal regions (including deeper situated fiber projections) and possibly involves an interaction with the prefrontal cortex, and that this damage is dissociable from the medial temporal-lobe damage leading to anterograde amnesia.

Amnesia, Retrograde↗
PubMed1993

Verbal learning differences in epileptic patients with left and right temporal lobe foci--a pharmacologically induced phenomenon?

A total of 27 patients with medically intractable complex partial seizures has been investigated for effects of anticonvulsant drugs on mental abilities, particularly on verbal memory performance. Fourteen patients with right (RTLE) and 13 with left (LTLE) temporal lobe epilepsy have been tested with a word list learning paradigm under the conditions of full and reduced anticonvulsant medication. Memory performance has significantly improved with drug reduction, however only for the LTLE group. In addition, significant group differences for verbal memory between LTLE and RTLE subjects under full medication have completely disappeared with drug reduction. Finally this investigation demonstrates, that very specific and circumscribed steps of verbal memory processing, particularly retrieval abilities after interference, are affected by anticonvulsants. These findings underline the importance of pharmacological effects on cognition and suggest to reevaluate their relevance compared to other contributing factors.

Adolescent↗
PubMed1993

Retrograde amnesia after traumatic injury of the fronto-temporal cortex.

An industrial manager had severe retrograde and variable but usually mild anterograde amnesia four years after a head injury. MRI showed damage of both temporal poles and the lateral portion of the right prefrontal cortex. The prefrontal and temporal cortical damage on the right side extended deeply into the white matter while the temporal cortical damage on the left side was much smaller. There was an additional left temporo-parietal lesion. The patient was of average intelligence. His attention, short term memory and learning ability were average or somewhat below average. His old memories were severely affected for the personal-episodic domain and less so for semantic remote memory abilities. Therefore an anatomical dissociation between anterograde and retrograde amnesia is possible at the anterior temporal regions, possibly interacting with the prefrontal cortex; these regions seem necessary for the retrieval of old episodic memories.

Amnesia, Retrograde↗
PubMed1992

Anticonvulsant drugs affect particular steps of verbal memory processing--an evaluation of 13 patients with intractable complex partial seizures of left temporal lobe origin.

Thirteen patients with intractable complex partial seizures of left temporal lobe origin were tested for verbal memory performance under the conditions of full and reduced anticonvulsant medication. As suggested by previous investigations memory performance improved significantly with the reduction of anticonvulsants. However, our observations refute assumptions that the effects of antiepileptic drugs act primarily by non-specific mechanisms affecting attention and/or memory diffusely. Our data rather suggest that very specific and circumscribed steps of verbal memory processing, particularly retrieval abilities after interference, are affected by anticonvulsants. The possible implications of these findings in relation to morphological and electrophysiological aspects in patients with temporal lobe epilepsy are discussed.

Adolescent↗
PubMed1992

Early signs of cognitive deficits among human immunodeficiency virus-positive hemophiliacs.

A total of 181 human immunodeficiency virus (HIV)-seropositive hemophiliacs and 28 hemophilic controls were evaluated by psychometric tests and by electroencephalogram (EEG). Patients were classified from stages 1-6 according to the immunological criteria of the Walter Reed staging system. Statistical analysis of psychometric data showed an effect of the stage of the disease on test performances, indicating a decline in attention, accumulation of perceptual interferences, decline in visuoperceptual speed and visuomotor response speed and reduced verbal memory performance, especially in stage 6 patients. Comparison of performance levels with normative test data already revealed cognitive deficits in about 20-30% of the patients in stages 2-5. As regards verbal memory, especially learning and recognition of new verbal information were impaired. In contrast, there was no significant deficit for nonverbal memory processing. Compared with the controls, patients exhibited an increasing number of abnormal EEG findings in stages 2-6. As a conclusion, in the stages before acquired immunodeficiency syndrome (AIDS) develops, EEG findings as well as psychometric findings indicate central nervous system involvement of AIDS in about 20-30% of cases, whereas in full-blown AIDS there is a marked increase to 80%. Besides a more general deficit of attention and psychomotor speed as is seen in subcortical dementia, there is evidence for a particular verbal learning disorder, suggesting additional selective impairment of the brain.

AIDS Dementia Complex↗
PubMed1992

[A case of apraxia and global aphasia without apraxia for axial body movement].

The case of a right handed 58 year old woman is presented who suffered an ischemic stroke after angiography following a vasospasm in the left internal carotid artery. The neuropsychological examination revealed global aphasia and severe apraxia for movements of the face and the extremities. However, the patient was able to carry out adequately axial movements to imitation and also to verbal command. These particular findings are discussed and explained within the context of the existing literature.

Aphasia↗
PubMed1991

Technetium-99m-HMPAO brain SPECT in medically intractable temporal lobe epilepsy: a postoperative evaluation.

The aim of the present study was to evaluate the predictive value of interictal single-photon emission computed tomography (SPECT) using technetium-99m-labeled hexamethyl propyleneamine oxime (HMPAO) for the outcome after temporal lobectomy in patients with complex partial seizures. Out of 40 patients, 21 underwent right-sided and 19 left-sided temporal lobectomy. EEG and CT/MRI were primarily used to select the side of surgery. SPECT results correlated with temporal lobectomy in 68% of the patients. After surgical intervention, memory function was tested for both sides. Following left-sided temporal lobectomy, verbal memory was impaired in 8% of the patients, if SPECT agreed with the side selected for surgery, but in 83%, if it diverged from it. In the present study, there was no relationship between SPECT concordance with the side of temporal lobectomy and outcome as to seizure frequency and non-verbal memory. We conclude that preoperative interictal HMPAO/SPECT can contribute to the prediction of postoperative verbal memory function and that this method should be considered for use prior to temporal lobectomy.

Adolescent↗
PubMed1990

Activation of the epileptic focus by transcranial magnetic stimulation of the human brain.

To establish whether transcranial magnetic stimulation is able to activate the primary epileptic focus preferentially, 13 patients who had medically intractable complex partial seizures were examined prior to surgical therapy. Single or a series of magnetic stimuli were applied to various regions of the skull. The effects of transcranial magnetic stimulation were monitored via subdurally implanted electrodes. In the process of presurgical evaluation, the dosage of anticonvulsant medication had been reduced in all patients but one. Transcranial magnetic stimulation was able to activate the epileptic focus (or foci) in 12 of the 13 patients. Distinct patterns of focal activation were observed in 3 patients who had several foci. No epileptiform potentials were induced outside epileptic foci, which had been identified by corticographic recordings. In one patient a complex partial seizure that was induced was identical to her habitual seizures. In another patient, a complete transition from a nonactive theta focus to a self-sustained epileptic focus occurred. A facilitation of epileptiform afterdischarge was seen with sequential stimulation. No adverse effects were either reported by the patients or observed by the investigators. In summary transcranial magnetic stimulation is able to activate the epileptic focus (or foci) and consequently may be an additional tool for the localization of epileptic foci in presurgical evaluation.

Adolescent↗
PubMed1990

Crossed cerebellar diaschisis in intracarotid sodium amytal procedures: a SPECT study.

Eight patients with drug-resistant complex-partial seizures were subjected to left- and right-sided intracarotid sodium amytal (ISA) procedures during preoperative investigations for surgical treatment. Regional changes of cerebral and cerebellar blood flow during barbiturization were measured by [99mTc]-HMPAO-SPECT. Crossed cerebellar diaschisis (CCD) was observed in 13 out of 16 tests (81%) as well as ipsilateral cerebral hypoperfusion (87%). Thus CCD occurred more frequently in ISA procedures than in previously studied patients with cerebral infarctions and tumors. Since intracarotid injections of sodium amytal lead to hypoperfusion mainly in those areas of the brain that are supplied by the middle cerebral artery, functional suppression of these regions is supposed to be one of the main preconditions of CCD. Our findings suggest that CCD as demonstrated by the SPECT-technique is a common phenomenon in ISA procedures.

Adolescent↗