Biomedical subjects

J M Annoni

Publications and source records attributed to J M Annoni.

At least 19 recordsLinked to original sources

PubMed2006

[Neurodegeneration and cerebrovascular disease: causal or incidental link?].

Neurodegenerative and cerebrovascular diseases have been related for more than a century. Epidemiological data show that main vascular risk factors are also risk factors for Alzheimer disease. Experimental evidences demonstrate that some of those risk factors accelerate the progress of Alzheimer lesions, mainly by acting on the amyloid cascade. Recent advances in understanding the basic mechanisms of CADASIL and familial amyloid angiopathy reveal that these forms of vascular dementias are degenerative disease of brain vessels. Modern neuroimaging techniques will allow to better understand relations between symptomatic strokes, silent infarcts, leukoaraiosis, microbleeds and degenerative pathology before the stage of dementia.

Cerebrovascular Disorders↗

PubMed2006

Chronic posttraumatic stress symptoms after nonsevere stroke.

OBJECTIVE: To determine whether posttraumatic stress disorder (PTSD)-related symptoms were present 1 year after a nonsevere stroke and, if so, to examine the relationship between PSTD, coexisting cognitive variables, and infarct localization METHODS: The authors assessed 49 patients using standard measures of memory, trauma experience, neurologic deficit, depression, anxiety, and PTSD. RESULTS: Fifteen (31%) patients had significant PTSD symptoms on the Impact of Event Scale (IES > 30). PTSD-like syndrome was independent of neurologic impairment, peristroke amnesia, long-term memory impairment, nosognosia, hypochondriac preoccupations, and physical pain during hospitalization, but was more frequent in women, less educated patients, and patients with more negative appraisals of the stroke experience. Intrusions were increased after basal ganglia strokes, suggesting that the re-experiencing phenomena may be modulated by frontosubcortical pathways. CONCLUSIONS: Posttraumatic stress disorder symptoms seem frequent in patients with nonsevere stroke and were associated with the subjective intensity of the stroke experience and accompanied by a depressive and anxious state.

Adult↗

PubMed2005

Changes in artistic style after minor posterior stroke.

BACKGROUND: Two professional painters experienced significant changes in their art as the main consequence of minor stroke located in the left occipital lobe or thalamus. METHODS: The features of this artistic conversion were analysed on the basis of extensive neurological, neuropsychological, and psychiatric evaluations. RESULTS: Both painters, initially unaware of the artistic changes, exhibited mild signs of executive dysfunction, but no general cognitive decline. The first painter, who showed mild visual-perceptive difficulties (dyschromatopsia and scotoma in his right upper visual field after left occipital stroke), together with increased anxiety and difficulty in emotional control, switched to a more stylised and symbolic art. The second painter, who also presented features of emotionalism related to his left latero-thalamic stroke, switched from an impressionist style to a more joyous and geometric, but more simplistic, abstract art. CONCLUSIONS: These findings show that mild cognitive and affective modifications due to focal posterior brain lesions can have significant repercussions on artistic expression.

Aged↗

PubMed2003

Pure imagery hemi-neglect of far space.

Patients with hemispatial neglect restricted to near (within reaching distance) or to far space (beyond reaching distance) have been described. This constitutes a double-dissociation considered by current neurocognitive thinking as compelling evidence for separate networks. However, a similar double-dissociation exists with respect to perceived as opposed to imagined space. If the organization of represented space was similar to that of perceived space, it should contain a far/near dissociation as well. This paper describes a patient with pure representational neglect restricted to far space.

Aged↗

PubMed2003

Pure global acalculia following a left subangular lesion.

We describe the case of a right-handed patient who presented a severe acalculia in the context of a pure Gerstmann syndrome following a subangular lesion that spared the left inferior parietal lobule (IPL). The patient showed impairments in Arabic and verbal codes, in number production and comprehension, as well as in numerical facts and problem solving. By using the EC301 calculation battery, semantic and syntactic tasks in Arabic and verbal codes, we tested the different hypotheses raised by the cognitive neuropsychological models of acalculia. The patients' difficulties, which were not associated with a general intellectual deterioration, and those affecting number processing as a particular semantic class, were indicative of a "global acalculia". This deficit, which exceeded the anarithmetia usually described in Gerstmann syndrome following left IPL lesion, suggested that the isolation of this area may constitute a sufficient condition for producing such a global acalculia. These results are discussed in terms of a disorder in the manipulation of mental images of spatially related objects.

Brain↗

PubMed2002

[Variability of right hemisphere activation during semantic word processing in aphasic patients: an electrophysiologic study in three patients].

After stroke, the interhemispheric reorganisation of the neural network implicated in language is hypothesized to be a function not only of the site of lesion but also of the residual impairment. With a multiple case approach, we tested this hypothesis in three chronic aphasic patients. Two patients, GE (capsulo-lenticular stroke) and JHN (fronto-temporal stroke) showed formal residual semantic difficulties, while the third patient (EG, large sylvian lesion) did not. Brain electric activity was analysed during a categorisation task of tachistoscopically presented words in the left and the right visual field. The temporal analysis of brain activity showed that both patients with semantic residual difficulties activated the right hemisphere (RH) during some steps of word processing. In the third patient, without semantic impairment, the RH was activated only during a short time period. Further more, RH activation was shown to be dependent on the visual field of word presentation. Phonological impairment was not predictive of RH activation. These results suggest that RH activation, particularly anterior regions, can occur during semantic processing of words as a function of semantic residual impairment.

Adult↗

PubMed2001

Language representation in a patient with a dominant right hemisphere: fMRI evidence for an intrahemispheric reorganisation.

Studies have suggested that congenital left hemispheric (LH) frontal arteriovenous malformations (AVMs) are associated with an early transfer of language to right hemisphere (RH) frontal regions. The question remains whether such anatomofunctional reorganisation is due to RH compensatory abilities or to a general principle of lateral shift. In this study, we used fMRI language paradigms to investigate the case of a patient presenting aphasic symptoms following an haemorrhage due to a right frontal AVM. Prior to surgery, fMRI showed that language processing was confined to the RH, suggesting that language had not shifted during childhood from this congenitally dominant RH to the LH. After surgery, the patient presented severe aphasia that recovered to presurgical level within 70 days. At this time, fMRI showed that language tasks were still not associated with activations in the LH. These results suggest that the principles of early cerebral reorganisation after congenital lesions may differ in the RH and the LH. In addition, they support the idea that efficient restoration of language is achieved if a sufficiently large neuronal network is preserved around the lesion.

Adult↗

PubMed2001

So near yet so far: neglect in far or near space depends on tool use.

The study of unilateral spatial neglect has shown that space can be dissociated on a peripersonal versus extrapersonal basis. We report a novel type of dissociation based on tool use in a patient suffering from left neglect. Line bisection was carried out in near and far space, using a stick and a laser pointer. A rightward bias was always found for the former, but not for the latter. Neglect thus appears to be contingent not only on distance, but also on the motor action required by the task.

Aged↗

PubMed2001

Pure representational neglect after right thalamic lesion.

After a right thalamic stroke, an 86-year-old man presented an acute pure left representational neglect in the absence of any perceptual neglect. On spatial mental imagery tasks, the patient systematically omitted items located on his left side, but only when a vantage point was given. This suggests that (1) pure representational neglect is not just a residual finding after recovery from global (perceptual and representational) neglect; (2) space representation can be coded by two independent processes: in viewer-centered or world-based (allocentric) coordinates; and (3) the right thalamus serves as a relay in the processing of spatial visual imagery.

Aged↗

PubMed2001

Brain energy metabolism in Alzheimer's disease: 99mTc-HMPAO SPECT imaging during verbal fluency and role of astrocytes in the cellular mechanism of 99mTc-HMPAO retention.

The central hypothesis of the study which has been carried out as part of the NRP38 program, is that perturbations of brain energy metabolism are critically involved in the neurodegeneration occurring in Alzheimer's disease (AD) and that they may correlate with early cognitive dysfunctioning. In the present multidisciplinary study we set out to monitor brain energy metabolism using FDG-PET and HMPAO-SPECT imaging in a cohort of individuals over 65 years of age, drawn from the general population. HMPAO-SPECT imaging, which is a simpler and more widely accessible imaging procedure than FDG-PET, was performed under basal conditions and during the performance of a cognitive task (verbal fluency test). Three groups were studied. Two groups (groups I and II) included individuals age 65 or more, with no cognitive impairment and carrying an APOE4 positive or APOE4 negative phenotype, respectively; a third group (group III) included patients with clinical signs of AD. Each subject entering the study underwent an FDG-PET, an HMPAO-SPECT and an extensive battery of neuropsychological tests which assess various aspects of cognitive functioning, with a strong emphasis on working memory, divided attention and executive functions. A total of 101 participants were submitted to brain imaging and neuropsychological testing. Among these, 60 participants received the same set of imaging and neuropsychological tasks 24-36 months after the first set (phase II). In this article, we present a preliminary analysis performed on ten subjects from groups I and II and nine subjects from group III: activation (verbal fluency task) induced a specific pattern of increase in HMPAO retention (including BA 9/10, BA 18 bilaterally and right BA 17). In contrast to controls, in nine AD subjects no significant differences in HMPAO retention were observed when comparing activation and basal conditions. The cellular and molecular mechanisms that underlie the retention of HMPAO, the tracer used for single photon emission computed tomography (SPECT) imaging, has been studied in vitro in purified preparations of neurons and astrocytes with the aim of investigating the contribution of different cell types to hexamethyl-propyleneamineoxime labeled with technetium-99m (99mTc-HMPAO) retention in vitro. Results show that 99mTc-HMPAO retention predominates in astrocytes over neurons by a factor of approximately 2.5. Diethyl maleate, ethacrynic acid and buthionine sulfoximine, three agents which significantly reduce glutathione levels, also decreased 99mTc-HMPAO retention in both astrocytes and in neurons. Decrease did not always correlate with glutathione levels however, thus suggesting that other factors could be involved. The data presented indicate that astrocytes might constitute a prominent site of 99mTc-HMPAO retention and most likely contribute significantly to the SPECT signal. In addition, they also suggest that specific alterations in glial cell metabolism could explain flow-independent changes in 99mTc-HMPAO retention in the brain as observed by SPECT in certain pathologies (including Alzheimer's disease). In particular, these observations suggest a key role of astrocytes in the signal detected with the imaging procedure, which is altered in the Alzheimer's cohort subjected to the verbal fluency activation task.

Aged↗

PubMed2001

The time course of semantic category processing in the cerebral hemispheres: an electrophysiological study.

Using visual half-field presentations of words to the right (RVF) and to the left visual field (LVF), this study investigated the time course of the hemispheric involvement in the processing of semantic category information. Multi-channel event related brain potentials (ERPs) were recorded from 15 healthy subjects during a categorisation task of sequentially presented word pairs. Subjects had to judge mentally after the appearance of the second word whether the words of a pair were semantically related (SR) or not (SU). ERPs were computed, from 100 ms before the onset of the second word to 600 ms, for SR and SU conditions in the LVF and in the RVF separately. The temporal segmentation of ERP map series into sequences of quasi-stable map configurations revealed a total of seven segments in each visual field of which only the first five (S1-S5, appearing between 70 and 400 ms) showed different map configurations as a function of visual field but presented a similar temporal sequence in both visual fields. By contrast, of the last two segments (S6 and S7) which appeared between approximately 400 and approximately 600 ms, only S7 differentiated SR and SU conditions in terms of its duration. Source localisation analysis of the segments showed that following the initial activation of posterior brain regions as a function of the visual field of presentation, a common neural network was activated in the left hemisphere (LH) although the dynamics of activation varied as a function of visual field. Concerning the role of the right hemisphere (RH) in lexico-semantic processing, the results presented here appear to be compatible with a 'callosal relay model' and suggest that, in healthy subjects, information is transferred rapidly ( approximately 150 ms) from the RH to the language dominant-LH.

Adult↗

PubMed2001

(133)Xe SPECT cerebral blood flow study in a healthy population: determination of T-scores.

UNLABELLED: Dementia is becoming a major health problem as the population of the Northern Hemisphere ages. Early differential diagnosis between normal cognitive decline and dementia is particularly difficult. If psychometric evaluation can contribute to the diagnosis, quantitative cerebral functional imaging would play an important role. We therefore proposed, first, to constitute a normative dataset that could later be used to identify subjects at risk for neurodegenerative processes and, second, to describe the risk of abnormal global cerebral blood flow (gCBF) by defining categories based on the standardized cutoff scores of a young, healthy population (T-score). METHODS: Of a total of 203 healthy volunteers, 187 were included in the protocol, which included evaluation of medical history, neurologic and neuropsychologic status, and body composition; analysis of blood; and measurement of gCBF by means of (133)Xe SPECT. RESULTS: With ANOVA analysis using age and sex as between-subject factors and gCBF as a within-subject factor, a significantly higher gCBF was found in women than in men. In addition, a linear reduction as a function of age was observed for both sexes (-0.3%/y). T-score was determined for the 18- to 28-y-old age group, for whom gCBF was found to be 46.7 +/- 5.1 mL/min/100 g tissue in men and 49.0 +/- 5.0 mL/min/100 g tissue in women. The age-dependent decrease could thus be expressed in T-scores and, in the 29- to 38-y-old, 39- to 48-y-old, and >48-y-old age groups, averaged -0.63, -1.29, and -1.92, respectively, in men and -0.63, -0.83, and-2.40, respectively, in women. Cognitive performance, body composition, and blood analysis revealed the expected significant effects from sex and age. CONCLUSION: The large-scale reference database of gCBF measurements constituted from a healthy, well-controlled population enabled age and sex stratification, which showed significant differences between the sexes and a significant decline as a function of age. T-scores were determined and warrant further studies on the prospective identification of early dementia by (133)Xe SPECT in elderly individuals.

Adolescent↗

PubMed2000

New insights into the Stroop effect: a spatio-temporal analysis of electric brain activity.

Recent clinical and imaging studies suggest the involvement of anterior brain regions in the Stroop effect without providing consensus on the hemisphere being involved. Here, we investigated the dynamics of brain activation during a modified Stroop task using behavioural, event-related potential map series, and source localization analysis. Behavioural analysis showed an increased RT in the interference (IC) as compared to the neutral (NC) and congruence conditions (CC). Map series analysis in these conditions displayed a similar sequence of 10 stable segments. From these, only segment S6, occurring at approximately 300 ms and displaying a dominant right anterior activation, was of increased duration in IC. Furthermore, in IC only, RT was shown to correlate with S6 duration. These results are discussed in terms of increased duration of an attentional process needed to solve the conflict.

Adult↗

PubMed2000

Lack of anticipatory gaze-orienting responses in patients with right brain damage.

OBJECTIVE: To study eye movements during cervical proprioceptive stimulation by passive body rotation in darkness, with the head held stationary, in patients with right brain damage and hemineglect. BACKGROUND: At very low frequency, this stimulation is reported to produce an illusion of head turning in space and eye deviations directed opposite to trunk rotation (in the direction of the illusory head rotation). METHODS: Ten normal subjects and seven patients with unilateral cerebral lesions (five right brain-damaged patients with mild to moderate visuospatial neglect, two left brain-damaged patients without neglect) were included in the study. Subjects were seated on a rotating chair. Stimuli consisted of slow sinusoidal passive trunk rotations (+/-30 degrees, 0.01 Hz) while the head was fixed in space. RESULTS: Eye movements directed opposite to trunk rotation were typical for normal subjects and for left brain-damaged patients. In contrast, all right brain-damaged patients showed either eye movements in the direction of trunk rotation or no eye deviations at all. CONCLUSION: This result could characterize a lack of anticipatory coordinating gaze behavior in patients with right brain damage.

Aged↗

PubMed2000

Semantic category and rhyming processing in the left and right cerebral hemisphere.

In this study, the question of hemispheric abilities in processing explicit semantic and phonological information was addressed by measuring response latencies and performances in two judgement tasks. In the semantic task, word pairs were sequentially presented to the left or right visual field and subjects were asked to judge whether these words were categorically related or not. In the phonological task, the same subjects were asked to decide whether pairs of orthographically dissimilar words rhymed or not. Statistical analysis showed that reaction times (RT) were significantly shorter in both tasks when words were presented to the right visual field. Furthermore, in the semantic task, faster responses were observed in both visual fields when the words were related than when they were unrelated. This response facilitation tended to be stronger when words were presented to the left visual field. This result is in accordance with other results obtained by lexical decision studies showing that priming in the right hemisphere is due to controlled processing. By contrast, RT differences between rhyming and non-rhyming word pairs in the phonological task did not reach significance. This supports previous findings showing that phonological facilitation cannot occur when orthographic and phonological indices are in conflict.

Journal Article↗

PubMed1999

Spatio-temporal analysis of electric brain activity during semantic and phonological word processing.

There is an ongoing debate in cognitive neuroscience about the time course and the functional independence of the different processes involved in encoding written language material. New data indicate very fast and highly parallel language analysis networks in the brain. Here we demonstrate a methodological approach to study the temporal dynamics of this network by searching for time periods where different task demands emphasize different aspects of the network. Multi-channel event related potentials (ERPs) were recorded during a semantic and a phonological reading task from 14 healthy subjects. Signals were analyzed exclusively on the basis of the spatial configuration of the electric potential distributions (ERP maps), since differences in these spatial patterns directly reflect changes in the configuration of the active sources in the brain. This analysis did not reveal any differences of the evoked brain electric fields between the two tasks up to 280 ms post-stimulus. The ERP maps then differed for a brief period between 280 and 380 ms, before they were similar again. The analysis of the maps using a global linear localization procedure revealed a network of areas, active in both tasks, that mainly involved the left postero-temporal and left antero-temporal regions. The left posterior activation was found already around 100 ms post-stimulus, indicating that language-specific functions appear early in time. We therefore conclude that phonological and semantic processing are essentially performed in both tasks and that only late decision-related processes influence the relative strength of activity of the different modules in the complex language network.

Adult↗

PubMed1999

Parenchymatous cerebral neurocysticercosis in a quadriplegic patient.

OBJECTIVE: To present and discuss a case of cerebral neurocysticercosis in a quadriplegic patient. DESIGN: Case report of a case of neurocysticercosis in a high level spinal cord injury (SCI) patient who developed episodes of autonomic dysreflexia and orthostatic hypotension associated with transient neurologic deficits and seizures. SETTING: Spinal Cord Unit of the University Hospital of Geneva, Switzerland. SUBJECT: Single patient case report. MAIN OUTCOME MEASURE: Clinical and radiological magnetic resonance imaging follow-up of the patient between July 1995 and October 1997. RESULTS: Treatment of cysticercosis with praziquantel relieved the patient from autonomic dysreflexia, symptomatic orthostatic hypotension, transitory neurological deficits and seizures. CONCLUSION: Diagnosis of neurocysticercosis in a quadriplegic patient might be difficult because of frequent overlaps with some usual symptoms occurring in high level SCI, mostly autonomic dysreflexia and orthostatic hypotension. Neurocysticercosis should be kept in mind when a SCI patient living in, or coming from endemic zones presents with new neurological abnormalities and seizures. Magnetic resonance imaging appears to be more sensitive than computerised tomography to confirm the diagnosis of active cysticercosis. Treatment with praziquantel associated with cimetidine to increase the drug bioavailability and prednisone to reduce the inflammatory reaction gives good results.

Animals↗

PubMed1999

A pure case of Gerstmann syndrome with a subangular lesion.

The four symptoms composing Gerstmann's syndrome were postulated to result from a common cognitive denominator (Grundstörung) by Gerstmann himself. He suggested that it is a disorder of the body schema restricted to the hand and fingers. The existence of a Grundstörung has since been contested. Here we suggest that a common psychoneurological factor does exist, but should be related to transformations of mental images rather than to the body schema. A patient (H.P.) was studied, who presented the four symptoms of Gerstmann's syndrome in the absence of any other neuropsychological disorders. MRI showed a focal ischaemic lesion, situated subcortically in the inferior part of the left angular gyrus and reaching the superior posterior region of T1. The cortical layers were spared and the lesion was seen to extend to the callosal fibres. On the basis of an extensive cognitive investigation, language, praxis, memory and intelligence disorders were excluded. The four remaining symptoms (finger agnosia, agraphia, right-left disorientation and dyscalculia) were investigated thoroughly with the aim of determining any characteristics that they might share. Detailed analyses of the tetrad showed that the impairment was consistently attributable to disorders of a spatial nature. Furthermore, cognitive tests necessitating mental rotation were equally shown to be impaired, confirming the essentially visuospatial origin of the disturbance. In the light of this report, the common cognitive denominator is hypothesized to be an impairment in mental manipulation of images and not in body schema.

Brain↗