Objectives: Previous literature showed that visual extinction and hemispatial neglect share common underlying mechanisms (Vuilleumier, P. O., & Rafal, R. D., 2000, A systematic study of visual extinction: Between- and within-field deficits of attention in hemispatial neglect. Brain 123,1263-1279), with common lesion patterns (Umarova, R. M., Saur, D., Kaller, C. P., Vry, M. S., Glauche, V., Mader, I., et al., 2011, Acute visual neglect and extinction: Distinct functional state of the visuospatial attention system. Brain 134, 3310-3325). However, the relationship between visual extinction and hemispatial neglect is still not fully understood. In this study we used functional magnetic resonance imaging (fMRI) to identify brain regions underlying visual extinction in right-sided stroke patients with hemispatial neglect (N = 9) and related age-/gender-matched healthy control subjects (N = 25). Materials & Methods: During fMRI, all participants were presented with a target stimulus (i.e., a black square of 2x2°; 10° apart from the central fixation point), that equiprobably appeared on either the left, right or both hemifields. Participants pressed one of three response buttons to indicate the hemifield(s) of target appearance, left, right, or bilateral. Results: Control subjects were extremely accurate in target detection, irrespective of target side (left side: 99.5%, right side: 99.5%, bilateral: 97.8%). By contrast, neglect patients failed to detect bilateral targets (22.2% of accuracy). Importantly, “bilateral” targets were perceived by neglect patients as “right” targets in the great majority of trials (56.3%). Moreover, neglect patients showed a decreased capability in detecting left (43.1%) vs. right targets (84.7%). The fMRI analysis revealed a greater involvement of the fronto-parietal cortex, bilaterally – despite most pronounced on the left hemisphere – in neglect patients as compared to healthy controls, irrespective of target side. Discussion & Conclusions: The increased activity of the fronto-parietal cortex appears to sustain the residual capabilities of neglect patients in detecting visual targets in the surrounding space. Overall, these findings provide new empirical evidence that visual extinction and hemispatial neglect are closely related, strengthening the notion that the lesion pattern underlying hemispatial neglect plays a major role in the phenomenology of visual extinction.
Mapping visual extinction in neglect patients through functional neuroimaging / Spano’, B.; Salsano, I.; Matano, A.; Briani, C.; Vadala’, R.; Nardo, D.; De Luca, M.; Giulietti, G.; Caltagirone, C.; Antonucci, G.; Santangelo, V.. - (2019). (Intervento presentato al convegno Italian Society for Neurology (SIN) tenutosi a Bologna).
Mapping visual extinction in neglect patients through functional neuroimaging
Salsano I.;Briani C.;Giulietti G.;Antonucci G.;
2019
Abstract
Objectives: Previous literature showed that visual extinction and hemispatial neglect share common underlying mechanisms (Vuilleumier, P. O., & Rafal, R. D., 2000, A systematic study of visual extinction: Between- and within-field deficits of attention in hemispatial neglect. Brain 123,1263-1279), with common lesion patterns (Umarova, R. M., Saur, D., Kaller, C. P., Vry, M. S., Glauche, V., Mader, I., et al., 2011, Acute visual neglect and extinction: Distinct functional state of the visuospatial attention system. Brain 134, 3310-3325). However, the relationship between visual extinction and hemispatial neglect is still not fully understood. In this study we used functional magnetic resonance imaging (fMRI) to identify brain regions underlying visual extinction in right-sided stroke patients with hemispatial neglect (N = 9) and related age-/gender-matched healthy control subjects (N = 25). Materials & Methods: During fMRI, all participants were presented with a target stimulus (i.e., a black square of 2x2°; 10° apart from the central fixation point), that equiprobably appeared on either the left, right or both hemifields. Participants pressed one of three response buttons to indicate the hemifield(s) of target appearance, left, right, or bilateral. Results: Control subjects were extremely accurate in target detection, irrespective of target side (left side: 99.5%, right side: 99.5%, bilateral: 97.8%). By contrast, neglect patients failed to detect bilateral targets (22.2% of accuracy). Importantly, “bilateral” targets were perceived by neglect patients as “right” targets in the great majority of trials (56.3%). Moreover, neglect patients showed a decreased capability in detecting left (43.1%) vs. right targets (84.7%). The fMRI analysis revealed a greater involvement of the fronto-parietal cortex, bilaterally – despite most pronounced on the left hemisphere – in neglect patients as compared to healthy controls, irrespective of target side. Discussion & Conclusions: The increased activity of the fronto-parietal cortex appears to sustain the residual capabilities of neglect patients in detecting visual targets in the surrounding space. Overall, these findings provide new empirical evidence that visual extinction and hemispatial neglect are closely related, strengthening the notion that the lesion pattern underlying hemispatial neglect plays a major role in the phenomenology of visual extinction.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
