Background Following injury to the right parietal cortex (e.g. right-sided stroke), patients typically show unilateral spatial neglect, a complex syndrome associated with a reduced capability to orient attentional resources toward the contralateral side of space. One of the most prominent symptoms is the visual extinction in which a transient stimulus presented in the right hemifield ‘extinguishes’ from awareness an homologue stimulus simultaneously presented in the left hemifield. This is thought to be a consequence of the residual activity of the left – non damaged – parietal cortex. Surprisingly, however, this hypothesis has been largely unexplored to date in real neglect patients. In this study we used functional magnetic resonance imaging (fMRI) to identify brain regions contributing to visual extinction assessing three groups of subjects: right-sided stroke patients with (N = 3) or without unilateral spatial neglect (N = 3) and age-/gender-matched healthy controls (N = 10). Method 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 appearance of the target, left, right, or bilateral. Results We found 100% accuracy in control subjects, irrespective of the target side, left, right or bilateral. By contrast, neglect patients failed to detect bilateral targets (16,3% of accuracy). Importantly, “bilateral” targets were perceived by neglect patients as “right” targets in the great majority of trials (66,25%). Moreover, neglect patients showed a decreased capability in detecting left (48,8%) vs. right targets (86,3%). The fMRI analysis revealed a greater task-related activity of the left fronto-parietal cortex in neglect vs. non-neglect patients and controls. Conclusions Our findings provide empirical evidence that confirm the crucial role played by the residual neural resources in the left fronto-parietal cortex during visual extinction in spatial neglect, providing important insights for the current models of unilateral spatial neglect in patients with right-sided stroke.
Mapping spatial neglect symptoms in patients with stroke / Salsano, Ilenia; Valerio, Santangelo; Alessandro, Matano; Rita, Vadala’; Giovanni, Giulietti; Maria De Luca, ; Davide, Nardo; Carlo, Caltagirone; Antonucci, Gabriella; Barbara, Spano’. - (2018). (Intervento presentato al convegno ISMRM - Italian Chapter tenutosi a Padua).
Mapping spatial neglect symptoms in patients with stroke
SALSANO, ILENIA;Gabriella Antonucci;
2018
Abstract
Background Following injury to the right parietal cortex (e.g. right-sided stroke), patients typically show unilateral spatial neglect, a complex syndrome associated with a reduced capability to orient attentional resources toward the contralateral side of space. One of the most prominent symptoms is the visual extinction in which a transient stimulus presented in the right hemifield ‘extinguishes’ from awareness an homologue stimulus simultaneously presented in the left hemifield. This is thought to be a consequence of the residual activity of the left – non damaged – parietal cortex. Surprisingly, however, this hypothesis has been largely unexplored to date in real neglect patients. In this study we used functional magnetic resonance imaging (fMRI) to identify brain regions contributing to visual extinction assessing three groups of subjects: right-sided stroke patients with (N = 3) or without unilateral spatial neglect (N = 3) and age-/gender-matched healthy controls (N = 10). Method 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 appearance of the target, left, right, or bilateral. Results We found 100% accuracy in control subjects, irrespective of the target side, left, right or bilateral. By contrast, neglect patients failed to detect bilateral targets (16,3% of accuracy). Importantly, “bilateral” targets were perceived by neglect patients as “right” targets in the great majority of trials (66,25%). Moreover, neglect patients showed a decreased capability in detecting left (48,8%) vs. right targets (86,3%). The fMRI analysis revealed a greater task-related activity of the left fronto-parietal cortex in neglect vs. non-neglect patients and controls. Conclusions Our findings provide empirical evidence that confirm the crucial role played by the residual neural resources in the left fronto-parietal cortex during visual extinction in spatial neglect, providing important insights for the current models of unilateral spatial neglect in patients with right-sided stroke.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
