Biomedical subjects

Marianne Regard

Publications and source records attributed to Marianne Regard.

10 recordsLinked to original sources

PubMed2006

Disruption of right prefrontal cortex by low-frequency repetitive transcranial magnetic stimulation induces risk-taking behavior.

Decisions require careful weighing of the risks and benefits associated with a choice. Some people need to be offered large rewards to balance even minimal risks, whereas others take great risks in the hope for an only minimal benefit. We show here that risk-taking is a modifiable behavior that depends on right hemisphere prefrontal activity. We used low-frequency, repetitive transcranial magnetic stimulation to transiently disrupt left or right dorsolateral prefrontal cortex (DLPFC) function before applying a well known gambling paradigm that provides a measure of decision-making under risk. Individuals displayed significantly riskier decision-making after disruption of the right, but not the left, DLPFC. Our findings suggest that the right DLPFC plays a crucial role in the suppression of superficially seductive options. This confirms the asymmetric role of the prefrontal cortex in decision-making and reveals that this fundamental human capacity can be manipulated in normal subjects through cortical stimulation. The ability to modify risk-taking behavior may be translated into therapeutic interventions for disorders such as drug abuse or pathological gambling.

Adult↗

PubMed2006

Polyopic heautoscopy: Case report and review of the literature.

Heautoscopy, i.e., the encounter with one's double, is a multimodal illusory reduplication of one's own body and self. In its polyopic form, more than one double is experienced. In the present article, we review fourteen published cases of polyopic heautoscopy and describe in detail the case of a 41-year-old man with polyopic heautoscopy resulting from a tumor in the insular region of the left temporal lobe. Our case is illustrative in several respects: (1) The patient's five doubles were all confined to the right hemispace. Laterality in this case is discussed with reference to previous cases of unilateral heautoscopy after focal brain damage, which generally do not show a hemispatial or hemispheric bias. (2) The patient's psychological affinity with his doubles, and also the extent of their echopraxia of his movements, decreased as a function of their perceived spatial distance from the patient's body, corroborating previous observations of associations between spatial and psychological phenomenologies during autoscopic phenomena. (3) While classical heautoscopy (the reduplication of a single body and self) is considered a breakdown in the integrative processes that enable us to identify our self with our body, the phenomenon of polyopic heautoscopy (a multiplication of body and self) points to the multiple mappings of the body, whose disintegration may give rise to the illusory experience of multiple selves.

Adult↗

PubMed2006

Lipoma on the corpus callosum in a patient with schizophrenia-like episode: is there a causal relationship?

Disturbed interhemispheric communication has been proposed as responsible for schizophrenia. We present a case of a schizophrenia-like episode with no neurologic or other psychiatric symptoms. However, magnetic resonance imaging revealed a lipoma on the splenium of the corpus callosum. Neuropsychologic examination revealed normal interhemispheric transfer, but a slight dysfunction associated with right-hemispheric anterior regions. Rather than supporting the hypothesis of a causal relationship between callosal abnormality and schizophrenia-like symptoms, our findings argue against a direct causal relationship between lesion site and psychotic episode. We conclude that cerebral abnormality per se may represent a risk factor for neuropsychiatric symptoms.

Adult↗

PubMed2005

Did Fyodor Mikhailovich Dostoevsky suffer from mesial temporal lobe epilepsy?

Many scientific authors--among them famous names such as Henri Gastaut or Sigmund Freud--dealt with the question from what kind of epilepsy Fyodor Mikhailovitch Dostoevsky (1821-1881) might had suffered. Because of the tight interplay between Dostoevsky's literary work and his own disease we throw light on the author's epilepsy against the background of his epileptic fictional characters. Moreover, we attempt to classify Dostoevsky's epilepsy on the basis of his bibliography, language, and literary work.

Epilepsy, Temporal Lobe↗

PubMed2005

Cognitive and emotional processing at high altitude.

INTRODUCTION: Exposure to altitude reduces oxygen supply to the central nervous system and may cause a variety of neuropsychological impairments. We investigated the relationship between certain cognitive functions and cardiovascular and respiratory variables during acute hypobaric hypoxia. METHODS: There were three groups of seven men who were each exposed to a 2-h altitude profile (AP) involving 30 min at each of the following simulated altitudes (m): AP1, 450-1500-3000; AP2, 450-1500-4500; Control 450-650-650. The neuropsychological tests included word fluency and three word-association tasks tapping processes of cognitive flexibility and emotion regulation. A lateralized tachistoscopic lexical decision task with high and low emotional target words was also administered to assess possible shifts in hemispheric superiorities for positive and negative affect. RESULTS: No significant differences in word fluency, word association, or lateralized lexical decision performances were found, despite a significant oxygen desaturation and a drop in diastolic BP at 4500 m, indicating the beginning of central hypoxia in terms of a functional impairment of the vasomotor center. CONCLUSION: During acute exposure to hypobaric hypoxia, selected cognitive and affective functions mediated by the frontal lobe were preserved. Functional hemispheric asymmetries for emotional processes remained unchanged.

Acclimatization↗

PubMed2004

Suppressing versus releasing a habit: frequency-dependent effects of prefrontal transcranial magnetic stimulation.

When subjects are required to generate a random sequence of numbers they typically produce too many forward and backward 'counts' (e.g. 5-6, 4-3). This counting bias is interpreted as the consequence of an interference by overlearned tendencies to arrange numbers according to their natural order. Inhibition of such well-learned routines is known to rely on frontal lobe functioning. We examined differential effects of slow (1 Hz) and fast (10 Hz) repetitive transcranial magnetic stimulation (rTMS) over the left or right dorsolateral prefrontal cortex (DLPFC) on random number generation (RNG) performance. Eighteen healthy men performed an RNG task. Those subjects stimulated over the left DLPFC showed a frequency-dependent rTMS effect: counting bias was significantly reduced after the 1 Hz stimulation compared with baseline, but significantly exaggerated after the 10 Hz stimulation compared with 1 Hz stimulation. In contrast, the sequences of the subjects stimulated over the right DLPFC showed the well-known excess of counting in all conditions (i.e. baseline, 1 Hz and 10 Hz). These findings confirm the functional importance of specifically the left DLPFC in sequential response production and show, for the first time, that rTMS affects cognitive processing in a frequency-dependent manner.

Adult↗

PubMed2003

Flunarizine in prevention of headache, ataxia, and memory deficits during decompression to 4559 m.

Our purpose was to study the preventive effect of the calcium channel blocker flunarizine on headache, postural ataxia, and memory deficits occurring during decompression to high altitude in a randomized, placebo-controlled, double-blind study. After 7-day pretreatment with the study drugs, 20 healthy men were investigated at 490 m and 0.5, 2, 4, and 6 h later at a simulated altitude of 4559 m. Headache severity was evaluated on a 4-point scale. Sway path and anteroposterior and lateral sway were recorded with open and closed eyes by static posturography. Short- and long-term memory was studied by testing the recall of verbal and figural material immediately and 2 h after presentation, respectively. Blood pressure (BP) and arterial oxygen saturation (Sa(O2)) were also assessed. Headache scores showed a trend to be lower in the flunarizine group that was significant after 4 and 6 h. Headache scores expressed as difference from baseline values showed a nonsignificant trend to be lower at 4 and 6 h in subjects treated with flunarizine. Postural stance, memory, BP, and Sa(O2) were similar in both treatment groups. Although the low number of investigated subjects may have prevented the detection of a significant therapeutic effect of flunarizine, the present data do not show that flunarizine is effective for prevention of headache, postural ataxia, and neurocognitive deficits occurring at simulated high altitude.

Adult↗

PubMed2003

Brain damage and addictive behavior: a neuropsychological and electroencephalogram investigation with pathologic gamblers.

BACKGROUND: Gambling is a form of nonsubstance addiction classified as an impulse control disorder. Pathologic gamblers are considered healthy with respect to their cognitive status. Lesions of the frontolimbic systems, mostly of the right hemisphere, are associated with addictive behavior. Because gamblers are not regarded as "brain-lesioned" and gambling is nontoxic, gambling is a model to test whether addicted "healthy" people are relatively impaired in frontolimbic neuropsychological functions. METHODS: Twenty-one nonsubstance dependent gamblers and nineteen healthy subjects underwent a behavioral neurologic interview centered on incidence, origin, and symptoms of possible brain damage, a neuropsychological examination, and an electroencephalogram. RESULTS: Seventeen gamblers (81%) had a positive medical history for brain damage (mainly traumatic head injury, pre- or perinatal complications). The gamblers, compared with the controls, were significantly more impaired in concentration, memory, and executive functions, and evidenced a higher prevalence of non-right-handedness (43%) and, non-left-hemisphere language dominance (52%). Electroencephalogram (EEG) revealed dysfunctional activity in 65% of the gamblers, compared with 26% of controls. CONCLUSIONS: This study shows that the "healthy" gamblers are indeed brain-damaged. Compared with a matched control population, pathologic gamblers evidenced more brain injuries, more fronto-temporo-limbic neuropsychological dysfunctions and more EEG abnormalities. The authors thus conjecture that addictive gambling may be a consequence of brain damage, especially of the frontolimbic systems, a finding that may well have medicolegal consequences.

Adolescent↗

PubMed2003

Language in the right cerebral hemisphere: contributions from reading studies.

Evidence for a right hemispheric involvement in language processing, in particular at the level of word meaning, has emerged within the last half century. Hemispheric functional specializations are dynamic; right hemispheric language participation significantly increases under certain conditions, such as during an epileptic seizure and during recovery from stroke. Interhemispheric connections via the corpus callosum critically mediate these and other higher cortical functions.

Animals↗

PubMed2002

Affective judgments of faces modulate early activity (approximately 160 ms) within the fusiform gyri.

Functional neuroimaging studies have implicated the fusiform gyri (FG) in structural encoding of faces, while event-related potential (ERP) and magnetoencephalography studies have shown that such encoding occurs approximately 170 ms poststimulus. Behavioral and functional neuroimaging studies suggest that processes involved in face recognition may be strongly modulated by socially relevant information conveyed by faces. To test the hypothesis that affective information indeed modulates early stages of face processing, ERPs were recorded to individually assessed liked, neutral, and disliked faces and checkerboard-reversal stimuli. At the N170 latency, the cortical three-dimensional distribution of current density was computed in stereotactic space using a tomographic source localization technique. Mean activity was extracted from the FG, defined by structure-probability maps, and a meta-cluster delineated by the coordinates of the voxel with the strongest face-sensitive response from five published functional magnetic resonance imaging studies. In the FG, approximately 160 ms poststimulus, liked faces elicited stronger activation than disliked and neutral faces and checkerboard-reversal stimuli. Further, confirming recent results, affect-modulated brain electrical activity started very early in the human brain (approximately 112 ms). These findings suggest that affective features conveyed by faces modulate structural face encoding. Behavioral results from an independent study revealed that the stimuli were not biased toward particular facial expressions and confirmed that liked faces were rated as more attractive. Increased FG activation for liked faces may thus be interpreted as reflecting enhanced attention due to their saliency.

Adult↗