The neurology of saccades and covert shifts in spatial attention - An event-related fMRI study

Authors
Citation
Rj. Perry et S. Zeki, The neurology of saccades and covert shifts in spatial attention - An event-related fMRI study, BRAIN, 123, 2000, pp. 2273-2288
Citations number
66
Categorie Soggetti
Neurology,"Neurosciences & Behavoir
Journal title
BRAIN
ISSN journal
00068950 → ACNP
Volume
123
Year of publication
2000
Part
11
Pages
2273 - 2288
Database
ISI
SICI code
0006-8950(200011)123:<2273:TNOSAC>2.0.ZU;2-B
Abstract
Visual neglect occurs most frequently and persistently after lesions that i nclude the right supramarginal gyrus (SMG), a part of the inferior parietal lobule, Patients with this syndrome make very few saccades to the left, an d show abnormal performance on tasks in which they must covertly shift thei r attention to the left, suggesting that the right SMG is involved in the g eneration of saccades and attention shifts, Functional imaging studies of s accades and covert attention shifts in the normal brain, however, have show n weak or absent responses in both SMGs, We used event-related functional M RI to rec examine the responses to saccades and attention shifts within a s ingle experiment, and to assess responses to left- and right-sided stimuli independently. When subjects made saccades to peripheral stimuli, the expec ted responses were seen in striate and prestriate cortex, the superior pari etal lobules, the frontal eye fields, the supplementary motor area and the anterior insulae, In addition there was a response in the right SMG but not in the left SMG, as predicted from the clinical literature. When subjects made a covert visual assessment of the peripheral stimulus without any sacc ade, greater activity was seen in all of the areas in the frontoparietal ne twork, Each area showed a bias towards contralateral stimuli, with two exce ptions: the anterior insulae gave mainly ipsilateral responses, whilst the right SMG gave equal responses to right- and left-sided stimuli. These find ings are discussed in the context of current theories pertaining to the cli nical syndrome of neglect.