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M Regard

Publications and source records attributed to M Regard.

At least 37 records · Page 2Linked to original sources
PubMed1997

What is the role of the corpus callosum in intermanual transfer of motor skills? A study of three cases with callosal pathology.

Intermanual transfer for a skilled motor task was studied in two patients with total callosal agenesis, and one with an acquired partial callosal lesion and clinical evidence for disturbed transfer of motor signals. Patients had to draw meaningless figures with one upper extremity (original learning, OL) and to reproduce their mirror-reversals thereafter with the other side (transfer learning, TL). Both directions of intermanual transfer were tested in two conditions, that is, between either proximal or distal muscle groups. Transfer was evaluated by comparing OL and TL performance at the same effector. The main variable of interest was movement time during the first eight trials of OL and TL. All three patients displayed a significant benefit for transfer from the dominant to the non-dominant hand but not vice versa during proximal motor activity. When compared with the performance of healthy subjects tested in almost identical conditions in a previously reported study, the proximal transfer behavior was found to be similar for all patients and the normal group. Although patients exhibited no significant benefit for distal transfer, their non-dominant-to-dominant distal transfer was above the normal range. The similar transfer pattern of the patients and healthy subjects when using proximal musculature suggests that proximal transfer may be subserved by identical extracallosal pathways, most probably by the ipsilaterally descending motor systems. Since non-dominant-to-dominant distal transfer was found to be disadvantageous in healthy subjects, the patients' relative superiority in this condition may reflect missing callosal influences of an inhibitory nature.

Adult↗
PubMed1997

Intermanual transfer of training: blood flow correlates in the human brain.

In a previous study, we found that relearning of a task with one hand might negatively be influenced by previous, opposite hand training of the analogue task, Thut G., et al., Exp. Brain Res., 108 (1996) 321-327. Drawing of a figure with the right hand, following left hand training, was slower than right hand drawing of an unknown figure. These conditions were termed right hand transfer learning (rTL) and right hand original learning (rOL). The present study aimed to identify the cerebral areas associated with these influences by measuring regional cerebral blood flow (rCBF) in 16 right-handed, healthy subjects during rTL and rOL. Positron emission tomography and statistical parametric mapping were used. Compared with rOL, rTL was associated with increased rCBF in the left medial prefrontal cortex and the right prefrontal convexity. Individual rCBF changes in the area homotopic to the right prefrontal convexity furthermore correlated with individual changes in rTL performance. While the smallest rCBF increases were found in subjects with weakest slowing of rTL relative to rOL, highest rCBF increases were present when rTL slowing dominated. Comparisons between rTL and rOL, however, revealed on average no performance differences. Our data suggest that relearning after previous opposite hand training activates neural mechanisms within the prefrontal convexity which might have an inhibitory function but that inhibition does not have to be the net final behavioral result.

Adult↗
PubMed1997

Cerebral metabolic changes (18F-FDG PET) during selective anterior temporal lobe amobarbital test.

Cerebral glucose utilisation using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) was measured in 4 patients with temporal lobe epilepsy during a selective anterior temporal lobe (TL) amobarbital test (ATLAT) and compared with their baseline values. 18F-FDG was injected intravenously immediately after administration of amobarbital into the anterior choroidal artery (acha) in the case of the superselective ATLAT and into the territories of acha, posterior communicating artery, and ophthalmic artery in the case of the ATLAT using the temporary balloon occlusion technique. A decrease in glucose uptake as a result of amobarbital application was observed in ipsilateral temporolateral (4 patients), ipsilateral temporomesial (2 patients) and bilateral frontolateral (1 patient) cortices. All patients showed decreased glucose uptake in contralateral temporolateral regions. Cerebellar diaschisis was observed in 2 patients. In conclusion, although aimed at selective inactivation of the mesiobasal TL structures, the ATLAT does not result in exclusive selective glucose hypometabolism of these structures. Relatively widespread ipsilateral and contralateral effects were observed suggesting local and remote metabolic deafferentation. No association was observed between the glucose uptake, clinical or memory performance.

Adolescent↗
PubMed1997

"Gourmand syndrome": eating passion associated with right anterior lesions.

We present a new benign eating disorder associated with lesions involving parts of the right anterior cerebral hemisphere. This "gourmand" syndrome describes a preoccupation with food and a preference for fine eating. Two exemplary case reports illustrate this new syndrome. Analysis of the clinical and anatomical data of 36 patients who displayed this behavior revealed, in 34, a strong association with lesion location in the right anterior part of the brain involving cortical areas, basal ganglia, or limbic structures. Our finding provides further evidence of a correlation between right hemispheric damage, eating, and other impulse control disorders. We conjecture that the serotonergic system subserves different functions in the left and right hemisphere.

Brain Diseases↗
PubMed1996

Intermanual transfer of proximal and distal motor engrams in humans.

We studied intermanual motor transfer for right-to-left or left-to-right direction of transfer between either proximal or distal upper extremity muscle groups. The influence of previously acquired motor engrams (original learning, OL) on learning efficiency of the contralateral side (transfer learning, TL) was examined in 26 right-handed healthy subjects. The task consisted of the drawing of meaningless figures. During TL, OL figures had to be reproduced as vertical mirror reversals. Data revealed a benefit for right-to-left but not left-to-right direction of transfer for time to complete a figure as well as a left-to-right transfer benefit for spatial motor precision. Furthermore, a benefit for intermanual transfer of training between proximal but not distal muscle groups was found when movement time to complete a figure was evaluated. Of special interest was the observation of a disadvantage due to prior contralateral learning for performance at right distal effectors. The asymmetrical transfer benefits with respect to side are in line with previous findings and support the proficiency model and the cross-activation model. Results further showed that intermanual transfer of training might differ with respect to muscle group involvement and suggest that, although primarily facilitating, previous opposite hand training may lead to inhibitory influences on subsequent contralateral reproduction.

Adult↗
PubMed1994

Hemispheric cooperation in visuospatial rotations: evidence for a manipulation role for the left hemisphere and a reference role for the right hemisphere.

A survey of mental rotation strategies in 210 normal subjects showed a strong tendency for right-handers to prefer rotating an object on the right and vice versa for left-handers. The differential functioning of the cerebral hemispheres during mental rotation was then assessed in 42 subjects by means of tachistoscopic presentation of two geometrical figures separately to the left and right visual fields--one of which was gravitationally stable and the other unstable. Performance was better when the unstable object was presented to the right visual field and the stable object to the left. This finding is interpreted as indicating more efficient hemispheric cooperation when the active manipulation of a mental image is performed by the left hemisphere, while the reference role is carried out by the right hemisphere.

Adolescent↗
PubMed1994

Singing with and without words: hemispheric asymmetries in motor control.

Singing is relatively preserved and can even improve the language production of aphasic patients who have lesions of the left hemisphere but an intact right hemisphere. In contrast, singing is impaired following lesions or anesthesia of the right hemisphere, suggesting a right hemisphere role in singing. To assess the influence of singing upon hemispheric control of articulatory output in normal subjects, we measured lip opening asymmetry by single-frame photographic analysis. Spontaneous speech, reciting the words of a song, and singing with words all showed right-side lip opening superiority, revealing a major left hemisphere role in control of verbal articulation. Singing without words, on the other hand, did not show asymmetric facial motor activation, suggesting that the right hemisphere also participates in singing. In addition, we assessed auditorily perceivable differences in articulation when lip movement on one side of the mouth was artificially restricted (hemibuccal speech). Articulation quality was higher when speaking from the right side of the mouth.

Adult↗
PubMed1994

The dynamics of cerebral dominance during unilateral limbic seizures.

An apparent discrepancy exists between the remarkable language competence of the isolated right cerebral hemisphere in some split-brain patients and the lack of language competence in some aphasic patients in whom only the left cerebral hemisphere has been damaged. This has led to a revival of the idea that the dominant cerebral hemisphere inhibits the potential functioning of its partner. We tested this model of interhemispheric inhibition in four patients with unilateral limbic seizures (three left-sided, one right-sided). While seizure activity was monitored with bilaterally implanted stereotactic EEG depth electrodes or bilateral foramen ovale EEG electrodes, the patients were tested in lateralized hemisphere-specific tachistoscopic recognition experiments. In two patients performance was correlated with the electrical pattern during prolonged unilateral subclinical limbic status epilepticus, and in two patients performance and intracranial electrical activity were compared before, immediately after and during the recovery phase of left limbic complex partial seizures with postictal aphasia. Three main findings were obtained. (i) Focal unilateral limbic seizure activity in the depth interferes with cognitive functions, even when unnoticed clinically or undetectable on the surface EEG, provided that epileptiform EEG activity lasts for several seconds. (ii) This interference is specific to the cognitive functions associated with the 'dominant' processing of the discharging hemisphere. (iii) Seizure-induced impairment of the 'dominant' functions of the discharging hemisphere is associated with improvement of performance of the same function by the other hemisphere. Although each patient's clinical and experimental situation differed, the converging results support the hypothesis of hemispheric interaction based upon functional inhibition for verbal processing in patients with a left hemispheric focus. The reverse situation, namely facial processing in a single case with a right hemisphere focus, remains inconclusive.

Adult↗
PubMed1994

Role of impaired CO2 reactivity in the diagnosis of cerebral low flow infarcts.

Previous studies on CO2 reactivity in cerebral low flow infarcts (LFIs) included patients with lesions in the frontoparasagittal area, supraganglionic white matter, and temporoparieto-occipital zone. Supraganglionic white matter LFIs are, however, difficult to separate from non-low flow induced infarcts of the lacunar type, and temporoparieto-occipital LFIs from infarcts in the territory of the inferior stem of the middle cerebral artery. The CO2 reactivity of the middle cerebral artery was studied in 56 patients with high grade stenoses and occlusions of the internal carotid artery and LFIs (n = 9) in the frontoparasagittal border zone, territorial infarcts (n = 26), no infarcts (n = 21), and normal subjects (n = 25) by means of transcranial Doppler sonography. The aim was to investigate whether patients with LFIs have significantly lower CO2 reactivity than patients with territorial infarcts, no infarcts, and normal subjects. Patients with LFIs had the most severely reduced CO2 reactivity on the symptomatic side and CO2 reactivity was significantly lower than on the asymptomatic side. It was also lower than in patients with unilateral and bilateral internal carotid artery obstructions and territorial infarcts, asymptomatic patients, and healthy volunteers. It is concluded that LFIs are associated with significantly reduced CO2 reactivity.

Adult↗
PubMed1994

Heautoscopy, epilepsy, and suicide.

Heautoscopy (the doppelgänger experience), epilepsy, and suicide is a triad primarily known from literary accounts. This paper reports a patient with complex partial seizures who tried to commit suicide during the experience of heautoscopy.

Adult↗
PubMed1994

[The "Neuropsychological Screening Test (NST)": initial validation and reliability studies].

Medical examinations only insufficiently measure cognitive impairment in neurological and neurosurgical patients. Due to costs an personnel shortages, adequate neuropsychological test methods are typically bypassed. Indeed, the very size and methodological problems of current tests impede their application in clinical practice. To resolve this dissatisfying state of affairs, we have developed a standardized, scored form of initial neuropsychological examination. The Neuropsychological Screening Test (NST) comprises 45 items, is easy to handle, and can be conducted in 15-20 min. The NST measures psychic performance along functional parameters such as orientation in place and time, primary and secondary language, visuospatial ability, attention, and memory skills. We have assessed the validity and reliability of the NST in a prospective study. 129 neurosurgical patients (60% malignant or benign cerebral tumors, 21% vascular malformations with and without subarachnoid hemorrhage, 6% traumatic brain injury, 3% hydrocephalus, 10% others) and 52 control subjects were included in the study. The difference in average total NST-scores was highly significant for the two groups (t = -7.84, DF = 177.93, p < .001). In addition, two chronologically separate subsamples of NCH patients (N = 81) and controls (N = 35) were tested using the Mini-Mental State (MMS). The correlation between total NST-score and MMS results was r = .49 (p < .001). Cross-tabulation was used to set a cut-off score, by means of which 80% of the neurosurgical patients were identified as true positive and 74% of the controls as true negative. A 24-hour retest confirmed the NST as reliable to .85 (p < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Bilateral neuropsychological deficits in unilateral paramedian thalamic infarction.

The neuropsychological deficits in 5 patients with chronic and MRI-proven unilateral infarctions in the perfusion territory of the paramedian thalamic arteries were studied. All patients showed deficits pointing to a dysfunction of frontotemporal hemispheric structures on the side of the thalamic lesion. However, 4 patients revealed additionally neuropsychological deficits pointing to a dysfunction of frontotemporal hemispheric structures overlying the nonaffected thalamus. The contralateral deficits showed (in 4 patients) signs of temporal and (in 3 patients) frontal lobe dysfunction. It is suggested that the bilaterality of the neuropsychological deficits results from additional contralateral thalamic lesions not detected by MRI and/or from bilateral cortical hypometabolism.

Adult↗
PubMed1993

Random-number generation and the menstrual cycle: preliminary evidence for a premenstrual alteration of frontal lobe functioning.

20 women (M age = 30.4 yr.) were given the "Mental Dice Task" (randomization of the numbers from 1 to 6) once during the preovulatory and once during the premenstrual phases of their menstrual cycles. In addition, for both test sessions a premenstrual-symptom score was assessed reflecting self-rated severity of cognitive, affective, and somatic complaints during the preovular and the premenstrual phases. In comparison to series of real dice throws, the Mental Dice sequences of all the subjects showed a relative lack of repetitions and an excess of counting at both times of testing. Counting bias was significantly enhanced in the sequences generated during the premenstrual testing and the size of this bias was positively correlated with the self-rated severity of premenstrual symptoms. Pronounced counting despite the instruction to randomize was interpreted as reflecting decreased ability to suppress task-irrelevant cues and indicating a relative impairment of frontal lobe functioning. Resistance of the Mental Dice Task towards expectation biases renders a sociopsychological interpretation of these results improbable. We conjecture that, like other cognitive processes, frontal lobe functions also fluctuate with hormonal changes.

Adult↗
PubMed1992

Dissociation of color from object in amnesia.

A patient with persistent amnesia after bilateral medial temporal and left inferotemporo-occipital infarction could not match colors to objects in verbal, visual, or visuoverbal tasks. A severe naming disorder for objects was present but the patient could name colors and point to colors whose name was given. The matching disorder appeared to be a deficit in the semantic classification of objects rather than a problem in identifying colors.

Aged↗
PubMed1992

Hemispheric dissociation in judging semantic relations: complementarity for close and distant associates.

In two lateralized tachistoscopic experiments, we presented (i) pairs of nouns with close or distant semantic associations or (ii) pairs of nouns which were randomly matched and later rated by the subjects as to their semantic distance. In both experiments, words presented to the right visual field were more frequently judged as semantically close in meaning than words presented to the left visual field (LVF), whereas words presented to the LVF were more frequently judged as semantically distant. The results are discussed in relation to hemispheric language functions and current models of cerebral laterality.

Adult↗