Selective attention involves focusing on one event among many, and is largely responsible for an organism's ability to respond efficiently to the environment. The location at which attention is focused is a function of an ongoing tension between external cues and internal goals. Control over selective attention is often described as an executive process, attributable to the function of the frontal lobes of the brain. The present experiments investigated the role of the frontal cortex in attentional control, through the study of patients with focal cortical lesions and through functional neuroimaging in neurologically normal subjects. It was found that patients with unilateral surgical resections from the frontal cortex were as efficient as patients with temporal-lobe resections and normal controls at attending selectively to a visual stimulus at one location in the presence of irrelevant distracting stimuli. In fact, those patients whose lesions invaded the anterior cingulate gyrus tended to be less reactive to changes in irrelevant stimuli. However, patients with frontal cortex lesions were mildly impaired in a different task in which they used visual cues to direct attention voluntarily to a different location from one trial to the next. In addition, patients with excisions from the right frontal cortex performed less efficiently with increasing time spent on a task, suggesting an important role for this region in sustained attention. These observations prompted a further study of attention using positron emission tomography in normal subjects. This experiment was designed to identify the brain regions that were more active during trials in which cues could be used to direct attention voluntarily, relative to trials in which uninformative cues were presented. The striatum and extrastriate cortex were the only regions in which blood flow correlated positively with the proportion of trials containing informative cues. The present studies indicate that the frontal
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.37576 |
| Date | January 1999 |
| Creators | Koski, Lisa Marie. |
| Contributors | Petrides, Michael (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001687504, proquestno: NQ55350, Theses scanned by UMI/ProQuest. |
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