Attention systems and the organization of the human parietal cortex

Abstract

Event-related functional magnetic resonance imaging was used to compare activity in the human parietal cortex in two attention-switching paradigms. On each trial of the visual switching (VS) paradigm, subjects attended to one of two visual stimuli on the basis of either their color or shape. Trials were presented in blocks interleaved with cues instructing subjects to either continue attending to the currently relevant dimension or to switch to the other stimulus dimension. In the response switching (RS) paradigm, subjects made one of two manual responses to the single stimulus presented on each trial. The rules for stimulus-response mapping were reversed on different trials. Trials were presented in blocks interleaved with cues that instructed subjects to either switch stimulus-response mapping rules or to continue with the current rule. Brain activity at "switch" and "stay" events was compared. The results revealed distinct parietal areas concerned with visual attentional set shifts (VS) and visuomotor intentional set shifts (RS). In VS, activity was recorded in the lateral part of the intraparietal region. In RS, activity was recorded in the posterior medial intraparietal region and adjacent posterior superior and dorsomedial parietal cortex. The results also suggest that the basic functional organization of the intraparietal sulcus and surrounding regions is similar in both macaque and human species. Key words: LIP; MIP; PE; conditional motor selection; intraparietal sulcus; set-switchingThere is no definite consensus on the correspondence between monkey and human parietal cortex. Brodmann (1909) argued that, in the monkey, the superior parietal lobule (SPL) and inferior parietal lobule (IPL) consist principally of areas 5 and 7, respectively. In the human, however, he suggested that both areas 5 and 7 are in the SPL, whereas new areas 39 and 40 are found in the IPL. Other anatomists, however, have identified a correspondence between the cytoarchitecture of the human and macaque IPL and the human and macaque SPL (Von Bonin and Bailey, 1947;Eidelburg and Galaburda, 1984). According to this view, the IPL and SPL are organized similarly in both species, and the intraparietal sulcus divides the parietal cortex similarly in both species.Functional imaging has not resolved this debate. Such studies suggest that visuospatial attention is correlated with posterior parietal activity in human subjects, but different studies locate the critical region in the SPL or IPL, and some even suggest that an extensive region including both lobules is associated with visuospatial attention (Corbetta et al., 1993(Corbetta et al., , 1995Nobre et al., 1997;Coull and Nobre, 1998;Corbetta and Shulman, 1999;Gitelman et al., 1999). It is therefore not clear if the human parietal cortex has a similar or dissimilar functional organization to that of the macaque, in which visuospatial attention and oculomotor control depend on the posterior IPL and adjacent lateral intraparietal sulcus Colby and Goldberg, 1999).In studies of visual attent...

Delirium as a disorder of consciousness

“…Of particular interest, work on attentional orienting to time shows preferential activation of the left inferior parietal lobule and the left inferior lateral premotor cortex,59 60 a pattern notably similar to that found in motor attention studies 61 – 63. Although the regions activated in attention and egocentric representation frames show many similarities, there are equally relevant differences.…”

Top–Down Enhancement and Suppression of Activity in Category-selective Extrastriate Cortex from an Act of Reflective Attention

“…Although this study did not include a functional visual short-term memory (VSTM) localizer task, the pattern of activity in this area and its coordinates suggest that it is anatomically and functionally the same region that has been previously isolated in studies of covert visual attention (e.g., Kincade, Abrams, Astafiev, Shulman, & Corbetta, 2005; Rushworth, Paus, & Sipila, 2001; Culham et al, 1998) and VSTM (e.g., Xu, 2007; Xu & Chun, 2006; Todd & Marois, 2004, 2005). In particular, this region appears to be close to Xu and Chun’s (2006) (also see Xu, 2007) “superior IPS” region.…”

A Parcellation Scheme for Human Left Lateral Parietal Cortex

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“…In humans, parietal cortex has traditionally been linked to processing mechanisms involving attention (Corbetta et al, 1998; Corbetta and Shulman, 2002; Dosenbach et al, 2007; Dosenbach et al, 2006; Rushworth et al, 2001; Yantis et al, 2002). Other accounts of parietal cortex function, particularly focused on the left hemisphere, have examined its role in reading (Turkeltaub et al, 2002), as well as numerosity judgments and arithmetic (Göbel and Rushworth, 2004; Hubbard et al, 2005).…”