18 research outputs found
Basi nervose dell'agnosia per le parti corporee e le azioni umane
No full textLa percezione visiva di facce e stimoli corporei non facciali porta all’attivazione di
distinte aree corticali. Inoltre, nonostante sia intimamente collegata, l’azione e la
forma corporea sembrano essere rappresentate in distinti sistemi neurali. Studi di
lesioni cerebrali hanno mostrato specifici disturbi associati con l’elaborazione del
volto umano, tuttavia non vi sono nella letteratura scientifica prove dell’esistenza di
disturbi specifici per il riconoscimento di parti del corpo non facciali. Nel presente
studio è stata dimostrata, attraverso la combinazione di paradigmi psicofisici e
tecniche avanzate di analisi e mappatura lesionale, la presenza di disturbi di
riconoscimento di facce o di parti del corpo non facciali in seguito a lesioni corticali
che coinvolgono rispettivamente la corteccia occipitale ventro-mediale o la corteccia
occipitale laterale. Inoltre, sono stati documentati disturbi di riconoscimento visivo
specifici per la forma o l’azione di parti del corpo umano escluse le facce, associati
rispettivamente ad una lesione nelle regioni occipito-temporali oppure nelle aree
premotorie. Questi disturbi categoria-specifici, chiamati agnosia per il corpo e
l’azione umana, ci suggeriscono che l'analisi visiva di stimoli costituiti da parti del
corpo umano possa essere effettuata da almeno due sistemi corticali, le aree posteriori
occipitotemporali, implicate nell’elaborazione dell’identità corporea e le aree
premotorie, coinvolte nell’analisi dell’azione osservata, indipendentemente
dall’identità del soggetto agente.Visual analysis of faces and non-facial body stimuli brings about neural activity in
different cortical areas. Moreover, even if inherently linked, body form and body
action may be represented in separate neural substrates. Brain lesion studies show
specific face processing deficits but neuropsychological evidence for defective
recognition of non-facial body parts is lacking. Combining psychophysics and lesionmapping
techniques we found that brain lesions specifically affecting the ventromedial
and lateral occipital cortex induce visual recognition deficits of face and nonfacial
body parts respectively. Moreover, we discovered recognition impairments
specifically affecting the form or the action of non-facial body stimuli and causatively
associated with lesions to occipito-temporal and premotor areas respectively. These
category-specific deficits, called body form and body action agnosia, suggest that
visual processing of non-facial body parts is based on a cortical division of labour
with occipito-temporal areas actively linked to processing body identity and premotor
areas to processing body action independent from the actors’ identity
Il contributo della neuropsicologia: disturbi dello schema corporeo in seguito a lesioni cerebrali
No full text
L’uomo e la macchina. La proposta di J.G. Ballard per la contemporaneità
No full textThe aim of the article is to demonstrate how a writer can approach a living matter, the relation connecting men and technological devices. In the present day the people can’t impose on the natural environment anymore, because now it’s the technologized and inhuman world to control their lives. Ballard’s Crash was composed in 1973, but it can perfectly describe contemporary society. The author suggests a fusion between men and machines as a way to assure the survival of the human species in the present day. We’ll try to prove how his proposal could still work
Vision of the body modulates processing in primary somatosensory cortex
No full textViewing the body affects somatosensory processing, even when entirely non-informative about stimulation. While several studies have reported effects of viewing the body on cortical processing of touch and pain, the neural locus of this modulation remains unclear. We investigated whether seeing the body modulates processing in primary somatosensory cortex (SI) by measuring short-latency somatosensory evoked-potentials (SEPs) elicited by electrical stimulation of the median nerve while participants looked directly at their stimulated hand or at a non-hand object. Vision of the body produced a clear reduction of the P27 component of the SEP recorded over contralateral parietal channels, which is known to reflect processing in SI. These results provide the first direct evidence that seeing the body modulates processing in SI and demonstrate that vision can affect even the earliest stages of cortical somatosensory processing
Anosognosia for apraxia: Experimental evidence for defective awareness of one's own bucco-facial gestures.
No full textAnosognosia is a multifaceted, neuro-psychiatric syndrome characterized by defective awareness of a variety of perceptuo-motor, cognitive or emotional deficits. The syndrome is also characterized by modularity, i.e. deficits of awareness in one domain (e.g. spatial perception) co-existing with spared functions in another domain (e.g. memory). Anosognosia has mainly been reported after right hemisphere lesions. It is however somewhat surprising that no studies have thus far specifically explored the possibility that lack of awareness involves apraxia, i.e. a deficit in the ability to perform gestures caused by an impaired higher-order motor control and not by low-level motor deficits, sensory loss, or failure to comprehend simple commands. We explored this issue by testing twelve fifteen patients with vascular lesions who were assigned to one of three groups depending on their neuropsychological profile and brain lesion. The patients were asked to execute various actions involving the upper limb or bucco-facial areas. In addition they were also asked to judge the accuracy of these actions, either performed by them or by other individuals. The judgment of the patients was compared to that of two external observers.
Results show that our bucco-facial apraxic patients manifest a specific deficit in detecting their own gestural errors. Moreover they were less aware of their defective performance in bucco-facial as compared to limb actions. Our results hint at the existence of a new form of anosognosia specifically involving apraxic deficits
Implicit awareness in anosognosia for hemiplegia: unconscious interference without conscious re-representation.
No full textSome patients with anosognosia for hemiplegia, i.e. apparent unawareness of hemiplegia, have been clinically observed to show ‘tacit’ or ‘implicit’ awareness of their deficits. Here we have experimentally examined whether implicit and explicit responses to the same deficit-related material can dissociate. Fourteen stroke patients with right hemisphere lesions and contralesional paralysis were tested for implicit and explicit responses to brief sentences with deficit-related themes. These responses were elicited using: (i) a verbal inhibition test in which patients had to inhibit completing each sentence with an automatic response (implicit task) and (ii) a rating procedure in which patients rated the self-relevance of the same sentences (explicit task). A group of anosognosic hemiplegic patients was significantly slower than a control group of aware hemiplegic patients in performing the inhibition task with deficit-related sentences than with other emotionally negative themes (relative to neutral themes). This occurred despite their explicit denial of the self-relevance of the former sentences. Individual patient analysis showed that six of the seven anosognosic patients significantly differed from the control group in this dissociation. Using lesion mapping procedures, we found that the lesions of the anosognosic patients differed from those of the ‘aware’ controls mainly by involving the anterior parts of the insula, inferior motor areas, basal ganglia structures, limbic structures and deep white matter. In contrast, the anosognosic patient without implicit awareness had more cortical lesions, mostly in frontal areas, including lateral premotor regions, and also in the parietal and occipital lobes. These results provide strong experimental support for a specific dissociation between implicit and explicit awareness of deficits. More generally, the combination of our behavioural and neural findings suggests that an explicit, affectively personalized sensorimotor awareness requires the re-representation of sensorimotor information in the insular cortex, with possible involvement of limbic areas and basal ganglia circuits. The delusional features of anosognosia for hemiplegia can be explained as a failure of this re-representation
The Neural Basis of Body Form and Body Action Agnosia
No full textVisual analysis of faces and nonfacial body stimuli brings about neural activity in different cortical areas. Moreover, processing body form and body action relies on distinct neural substrates. Although brain lesion studies show specific face processing deficits, neuropsychological evidence for defective recognition of nonfacial body parts is lacking. By combining psychophysics studies with lesion-mapping techniques, we found that lesions of ventromedial, occipitotemporal areas induce face and body recognition deficits while lesions involving extrastriate body area seem causatively associated with impaired recognition of body but not of face and object stimuli. We also found that body form and body action recognition deficits can be double dissociated and are causatively associated with lesions to extrastriate body area and ventral premotor cortex, respectively. Our study reports two category-specific visual deficits, called body form and body action agnosia, and highlights their neural underpinnings
Phenomenology and neural correlates of implicit and emergent motor awareness in patients with anosognosia for hemiplegia
No full textAnosognosia for hemiplegia (AH) is characterized by a lack of awareness of motor disorders and appears associated with fronto-temporal-parietal damage. Neuropsychological evidence indicates that behavioral indices of residual forms of motor awareness may co-exist with explicit denial of impairment. Here we explore whether the attempt by AH patients to perform an action may disclose residual forms of motor awareness and whether such forms are underpinned by different neural structures. Twelve hemiplegic patients affected by AH were tested in tasks assessing: (i) implicit awareness (IA), indexed by discrepancies between verbal reports and actual motor behavior: (ii) emergent awareness (EA), indexed by increased verbal awareness induced by the attempt to perform actions. IA and EA were found in five and three patients, respectively. Lesion analysis indicates that while the lack of IA is associated with damage to subcortical white matter anterior to the basal ganglia, lack of EA is linked to damage to cortical regions including insulo-frontal, temporal and parietal structures. Our results indicate that deficits in explicit and implicit awareness are associated with lesions involving different cortico-subcortical structures. Moreover, the results show that the attempt to perform an action may ameliorate body awareness deficits and have implications for rehabilitation. (C) 2011 Elsevier B.V. All rights reserved
