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J L Signoret

Publications and source records attributed to J L Signoret.

At least 19 recordsLinked to original sources
PubMed1992

Functional and anatomical decomposition of face processing: evidence from prosopagnosia and PET study of normal subjects.

Studies of brain-damaged patients have revealed the existence of a selective impairment of face processing, prosopagnosia, resulting from lesions at different loci in the occipital and temporal lobes. The lesions are often extensive, and it is unclear what functional aspects of face processing are normally served by the damaged areas, and whether they are uniquely devoted to the processing of faces. These issues are further addressed through a combined magnetic resonance imaging (MRI) and positron emission tomography (PET) study of regional cerebral blood flow (rCBF) in normal subjects performing different tasks of face and object processing. The results indicate different patterns of cerebral activation depending on the requirements of the tasks within the processing of faces, as well as a clear dissociation of the neural substrates underlying face and object processing. These results are compared with radiological data from prosopagnosic patients, and are put in relation with the patterns of deficits observed in the patients as a function of the location of their lesions. Together, the findings offer new evidence regarding the functional neuroanatomy of face and object processing.

Agnosia↗
PubMed1992

Cognitive functions in Duchenne muscular dystrophy: a reappraisal and comparison with spinal muscular atrophy.

In order to clarify cognitive functions in Duchenne muscular dystrophy (DMD), we performed a new controlled neuropsychological study. IQ (WISC-R), verbal skills (fluency, confrontation naming and syntax comprehension) and memory abilities (BEM) were studied in two matched groups; 24 DMD children and 17 spinal muscular atrophy (SMA) children aged 12-16 yr. A significant difference appeared between the DMD and SMA patients: only in the DMD group were there significant disabilities in certain specific functions and normal scores in others. Despite similar education, the DMD children more often had significantly greater learning disabilities. There were more DMD left-handers. Verbal IQ was significantly low whereas performance IQ was at a normal level. DMD children also performed poorly in reading tasks and in some memory functions such as story recall and verbal recognition. Specific cognitive disabilities in certain DMD children, not seen in SMA children, suggest a relationship with a DMD genetic disorder.

Adolescent↗
PubMed1992

[Selective sensitivity of cysts to praziquantel and albendazole in a case of cerebral cysticercosis].

A case of neurocysticercosis in a Zaïrian patient with clinical and neuro-radiological follow-up is reported. Treatment with praziquantel resulted in the regression of only some of the cysts. Subsequent treatment with albendazole was effective, eliminating most of the remaining lesions. This case illustrates a selective sensitivity of cysts to praziquantel and albendazole in a single patient.

Adult↗
PubMed1991

[Examination and memory].

Examining memory is required in various circumstances. A simple rule never to be forgotten is that the examination of mnemonic capacities must not be separated from examination of other cognitive capacities. The first stage is clinical. The evaluation of mnemonic efficiency--i.e. the ability to store and retrieve new information--is the essential part of the examination and is carried out by means of standardized tests. Old memory, short-term memory, semantic memory and procedural memory must also be evaluated.

Humans↗
PubMed1991

The commissuro-mamillary plane in MRI of the brain (preliminary communication).

MRI sections of the brain in the coronal plane through the line joining the anterior commissure and the mamillary bodies display the constituent parts of the basal forebrain. The visualisation of the septal nuclei and the anterior columns of the fornix show the importance of this plane in the study of behaviour disorders and amnesic syndromes.

Corpus Striatum↗
PubMed1991

[Illusion of visual tilt: a case].

A 21-year-old man experienced sudden and intense rotational vertigo. A moment later, he was amazed to see the whole visual world rotate clockwise progressively by about 160 degrees. On the following day, the visual tilt was only 30 degrees, and it soon receded completely, while headache appeared. CT scan, magnetic resonance imaging, vertebral arteriography, and cerebrospinal fluid analysis were normal, and the aetiology could not be ascertained. Illusions of visual tilt are an unusual consequence of disorders affecting the vestibular system. The locus of the impairment is usually in the brainstem, particularly in association with Wallenberg's syndrome. However, the peripheral vestibular pathways or the vestibular projections into the cerebral cortex may occasionally be involved. In the latter case, the visual tilt is part of a vestibular epileptic seizure.

Adult↗
PubMed1991

[Amnesic syndrome caused by limited infarction in the right anterior thalamus].

A case of global and persistent amnesia due to a right polar and anterior thalamic infarction is reported. There was a moderate impairment of attention and categorization ability. The amnesia was primarily anterograde, with partial disturbance of short-term memory and severe deficit of long-term memory for verbal and visuo-spatial materials. A severe increase of pro-active interference was present. Retrograde memory was mildly affected. Two years later, a second infarction in the right thalamo-sub-thalamic territory occurred, increasing the deficits of attention, short-term memory and recall.

Adult↗
PubMed1991

[Slowly progressive apraxia: a MRI and positron tomography in 4 cases].

Four right-handed patients (69, 58 and 68 year-old men; 85 year-old woman) complained of motor difficulties with their left hand (3 cases), or both hands predominant on the left side (1 case). Continuous (1 case) or intermittent (2 cases) myoclonus was noted in the left arm. These disorders gradually progressed for 3 to 10 years. Clinical examination disclosed absence of motor, sensory (except in 1 case), or visual deficit. There were no cerebellar signs, no parkinsonian features (except for mild rigidity in 1 case), and no oculomotor abnormality. On the other hand, neuropsychological examination showed evidence of visuo-constructive apraxia in all cases, dressing apraxia in 3/4 cases and writing impairment in 3/4 cases. There was no amnesia, no aphasia and no intellectual impairment. MRI showed atrophy of the parietal areas, predominant on the right side. A positron emission tomography study was performed in all cases, and twice in 1 case. Cortical energy metabolism was measured using either 18 F-fluorodeoxyglucose or 15 O-Oxygen, to calculate the cerebral metabolic rate of glucose (CMRglu) or oxygen (CMRO2) respectively. Cortical metabolism was significantly decreased in the whole cortex of the right hemisphere in 3 cases, and was also reduced in the cortex of the left hemisphere, significantly in 1/3 studied planes. Moreover, regional metabolic indices (CMRO2 or CMRglu/cortex) showed a significant decrease in both the right and left posterior associative areas (temporo-parieto-occipital cortex), predominantly marked on the right side in 3 cases, indicating bilateral cortical dysfunction. At follow-up, one patient became progressively demented, another had visuo-spatial disorders indicating a lesion of both parietal areas. The relationships of our cases with the slowly progressive apraxia syndrome and with corticobasal degeneration are discussed.

Aged↗
PubMed1990

The commissuro-mamillary plane in MRI of the brain (preliminary communication)

MRI sections of the brain in the coronal plane through the line joining the anterior commissure and the mamillary bodies display the constituent parts of the basal forebrain. The visualisation of the septal nuclei and the anterior columns of the fornix show the importance of this plane in the study of behaviour disorders and amnesic syndromes.

Brain↗
PubMed1990

Acute or subacute alcoholic neuropathy mimicking Guillain-Barré syndrome.

Over the last 10 years we have encountered 8 patients with chronic alcoholism who presented with severe symmetrical polyneuropathy, primarily proximal in 6, which evolved over a period of 24 h to 3 weeks. In 3 cases, artificial ventilation was required. Sensory symptoms were in all instances intense, and tendon reflexes absent. CSF protein levels were normal. The course was one of gradual improvement, often incomplete with residual motor and distal sensory deficits. Three patients died within 2 months to 2 years with multiple and severe pathologies attributable to chronic alcoholism. There was no evidence for disorders other than the alcoholism and malnutrition. Electrophysiological findings were consistent with predominantly axonal lesions and nerve biopsy specimens confirmed acute and severe axonal lesions. Several of these patients had been referred to us with a possible diagnosis of Guillain-Barré syndrome due to the severity of the neuropathy and the rapidity of its onset (Landry syndrome). Acute alcoholic neuropathy is distinguishable, however, on clinical, electrophysiological and morphological grounds.

Acute Disease↗
PubMed1990

[Psychic life and awakening from coma in neurosurgical intensive care].

What is knowable concerning the lived experience and the psychopathology of patients during the border state between coma and waking? The waking up period appears divided in two parts: "apparent incommunicability" and "waking in strangeness". A pluridisciplinary follow-up seems necessary for patients beginning with the neurosurgical reanimation process.

Coma↗
PubMed1989

[Neuropsychological evaluation].

The neuropsychological evaluation of Alzheimer's disease relies on a functional analysis of the various mental or cognitive activities (memory, speech, etc.). It demands the use of standardized and usually quantifiable methods such as mental tests, standard test batteries and behaviour scales. The objective of evaluation is threefolds: (1) to provide an early or difficult diagnosis (elderly or depressed patients); (2) to establish a qualitative and quantitative typology of demential state, and (3) to assess the effects of drugs on behaviour in therapeutic trials.

Alzheimer Disease↗
PubMed1989

Brain potentials reveal covert facial recognition in prosopagnosia.

Brain potentials were recorded in a prosopagnosic patient, in response to familiar and unfamiliar faces he was asked to recognize. The amplitude of the P300 component was found to be an inverse function of probability for each category of faces despite the patient's inability to consciously recognize the familiarity of these faces. In addition, P300 latency varied from 700 to 800 msec according to the familiarity of the faces, and P300 scalp location was different as a function of faces probability and overt recognition. The results imply that covert facial recognition may be evidenced in using event-related potentials of the brain. They also demonstrate that automatic and covert processing of face familiarity are preserved, but prolonged in this patient.

Agnosia↗
PubMed1989

[Cerebral evoked potentials and conscious and unconscious recognition of faces: application to the study of prosopagnosia].

Twelve normal subjects and a prosopagnosic patient were tested in a classification task of a random display of well-known among unknown faces. Each face was presented several times. Event-related potentials (ERP) and reaction time (RT) were studied as a function of face repetition and familiarity. For normal subjects, the greater the repetition level, the more positive ERPs were on both hemispheres: between 250 and 600 msec. Moreover, the familiarity of faces modified ERPs between 350 and 600 msec. In contrast for the patient, the greater the repetition, the more negative the ERPs were. This "negative effect" was maximum on right parieto-temporal leads and was longer for unrecognized well-known than for unknown faces. These results support a differential processing of faces as a function of their memory representations for both normal subjects and patients. They further demonstrate the existence of covert face recognition processes in prosopagnosia.

Adult↗
PubMed1989

[Are the lesions responsible for prosopagnosia always bilateral?].

To localize the lesions responsible for prosopagnosia one must first consider how recent anatomico-physiological data have modified our view of the visual system: the visual cortex has been parceled into a mosaic of visual areas, each of them processing preferentially a particular feature (form, colour, movement); there is evidence of a face area in the monkey temporal lobe, and a new model of the inferior longitudinal fasciculus has been offered. It is currently accepted that face recognition deficits are due to bilateral occipito-temporal lesions, but in view of several recent reports in which the lesions were localized on CT or MRI one may doubt that these lesions are necessarily bilateral. In some cases a right unilateral lesion seemed to be sufficient to induce prosopagnosia.

Agnosia↗
PubMed1989

[Visual object agnosia: current conceptions].

Visual agnosia for objects is a difficulty in recognizing objects presented visually. This difficulty can not be explained by a mental deterioration, a disorder of attention or a lack of familiarity with the object. Two criteria are essential but disputed: the absence of visual sensory difficulty necessary for adequate perception; possible recognition of the object by another sensory modality. An object is characterized by a triple representation: formal, semantic, lexical. The clinical, cognitive, pathophysiological analysis lead to distinguish 3 types of visual agnosia. 1) Aperceptive visual agnosia: patients see badly with morphological errors; the disorder concerns visual informations processing that is a necessary condition for identifying the formal representation of the object; the lesions are bilateral and involve the occipito-temporal cortex. 2) Associative visual agnosia: patients can copy, are not aphasic, but give erroneous verbal responses; the disorder concerns the links between formal representations and semantic, lexical representations; the lesions are unilateral and involve the left gyrus angularis connections. 3) Asemantic visual agnosia: patients have lost the meanings of objects and words; the disorder concerns semantic representations; the lesions are bilateral and involve the temporo-limbic cortex.

Agnosia↗