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Role of right posterior parietal cortex in maintaining attention to spatial locations over time.

Malhotra P, Coulthard EJ, Husain M - Brain (2009)

Bottom Line: We found evidence of an overall deficit in sustaining attention associated with PPC lesions, even for a simple detection task with stimuli presented centrally.Lesioned voxels in the right PPC spanning a region between the intraparietal sulcus and inferior parietal lobe were significantly associated with this deficit.Again, we found a vigilance decrement but only when attention had to be maintained on spatial information.

View Article: PubMed Central - PubMed

Affiliation: UCL Institute of Cognitive Neuroscience, London, UK. p.malhotra@imperial.ac.uk

ABSTRACT
Recent models of human posterior parietal cortex (PPC) have variously emphasized its role in spatial perception, visuomotor control or directing attention. However, neuroimaging and lesion studies also suggest that the right PPC might play a special role in maintaining an alert state. Previously, assessments of right-hemisphere patients with hemispatial neglect have revealed significant overall deficits on vigilance tasks, but to date there has been no demonstration of a deterioration of performance over time--a vigilance decrement--considered by some to be a key index of a deficit in maintaining attention. Moreover, sustained attention deficits in neglect have not specifically been related to PPC lesions, and it remains unclear whether they interact with spatial impairments in this syndrome. Here we examined the ability of right-hemisphere patients with neglect to maintain attention, comparing them to stroke controls and healthy individuals. We found evidence of an overall deficit in sustaining attention associated with PPC lesions, even for a simple detection task with stimuli presented centrally. In a second experiment, we demonstrated a vigilance decrement in neglect patients specifically only when they were required to maintain attention to spatial locations, but not verbal material. Lesioned voxels in the right PPC spanning a region between the intraparietal sulcus and inferior parietal lobe were significantly associated with this deficit. Finally, we compared performance on a task that required attention to be maintained either to visual patterns or spatial locations, matched for task difficulty. Again, we found a vigilance decrement but only when attention had to be maintained on spatial information. We conclude that sustaining attention to spatial locations is a critical function of the human right PPC which needs to be incorporated into models of normal parietal function as well as those of the clinical syndrome of hemispatial neglect.

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Related in: MedlinePlus

Performance over time on spatial and non-spatial tasks. (A) Errors over time epoch on spatial task (Error bars = SEM). Total time = ∼8 min. (B) Errors over time on non-spatial task (Error bars = SEM). Total time = ∼8 min. (C) Sensitivity of target detection (d′) across time on the spatial task. Neglect patients begin with lower target sensitivity than control patients, and this decreases substantially after the fourth epoch. Note log scale.
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Figure 6: Performance over time on spatial and non-spatial tasks. (A) Errors over time epoch on spatial task (Error bars = SEM). Total time = ∼8 min. (B) Errors over time on non-spatial task (Error bars = SEM). Total time = ∼8 min. (C) Sensitivity of target detection (d′) across time on the spatial task. Neglect patients begin with lower target sensitivity than control patients, and this decreases substantially after the fourth epoch. Note log scale.

Mentions: A mixed design ANOVA was completed for errors with epoch and task as within subject factors (Fig. 6). There was a significant effect of group [F(2,21) = 21.58, P < 0.001], with the neglect group making more errors than right-hemisphere stroke patients without neglect (Post hoc Tukey's HSD test, P < 0.001). There was also a significant effect of task [F(1,21) = 38.95, P < 0.001], with all groups making more errors on the spatial than the non-spatial task. Neglect patients were not significantly worse than the two control groups on the non-spatial task (One way ANOVA, [F(2,21) = 2.24, P = 0.133]. In addition, there was also a significant interaction between task and group [F(2,21) = 17.67, P < 0.001] but no significant interaction for epoch versus group.Figure 6


Role of right posterior parietal cortex in maintaining attention to spatial locations over time.

Malhotra P, Coulthard EJ, Husain M - Brain (2009)

Performance over time on spatial and non-spatial tasks. (A) Errors over time epoch on spatial task (Error bars = SEM). Total time = ∼8 min. (B) Errors over time on non-spatial task (Error bars = SEM). Total time = ∼8 min. (C) Sensitivity of target detection (d′) across time on the spatial task. Neglect patients begin with lower target sensitivity than control patients, and this decreases substantially after the fourth epoch. Note log scale.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2664449&req=5

Figure 6: Performance over time on spatial and non-spatial tasks. (A) Errors over time epoch on spatial task (Error bars = SEM). Total time = ∼8 min. (B) Errors over time on non-spatial task (Error bars = SEM). Total time = ∼8 min. (C) Sensitivity of target detection (d′) across time on the spatial task. Neglect patients begin with lower target sensitivity than control patients, and this decreases substantially after the fourth epoch. Note log scale.
Mentions: A mixed design ANOVA was completed for errors with epoch and task as within subject factors (Fig. 6). There was a significant effect of group [F(2,21) = 21.58, P < 0.001], with the neglect group making more errors than right-hemisphere stroke patients without neglect (Post hoc Tukey's HSD test, P < 0.001). There was also a significant effect of task [F(1,21) = 38.95, P < 0.001], with all groups making more errors on the spatial than the non-spatial task. Neglect patients were not significantly worse than the two control groups on the non-spatial task (One way ANOVA, [F(2,21) = 2.24, P = 0.133]. In addition, there was also a significant interaction between task and group [F(2,21) = 17.67, P < 0.001] but no significant interaction for epoch versus group.Figure 6

Bottom Line: We found evidence of an overall deficit in sustaining attention associated with PPC lesions, even for a simple detection task with stimuli presented centrally.Lesioned voxels in the right PPC spanning a region between the intraparietal sulcus and inferior parietal lobe were significantly associated with this deficit.Again, we found a vigilance decrement but only when attention had to be maintained on spatial information.

View Article: PubMed Central - PubMed

Affiliation: UCL Institute of Cognitive Neuroscience, London, UK. p.malhotra@imperial.ac.uk

ABSTRACT
Recent models of human posterior parietal cortex (PPC) have variously emphasized its role in spatial perception, visuomotor control or directing attention. However, neuroimaging and lesion studies also suggest that the right PPC might play a special role in maintaining an alert state. Previously, assessments of right-hemisphere patients with hemispatial neglect have revealed significant overall deficits on vigilance tasks, but to date there has been no demonstration of a deterioration of performance over time--a vigilance decrement--considered by some to be a key index of a deficit in maintaining attention. Moreover, sustained attention deficits in neglect have not specifically been related to PPC lesions, and it remains unclear whether they interact with spatial impairments in this syndrome. Here we examined the ability of right-hemisphere patients with neglect to maintain attention, comparing them to stroke controls and healthy individuals. We found evidence of an overall deficit in sustaining attention associated with PPC lesions, even for a simple detection task with stimuli presented centrally. In a second experiment, we demonstrated a vigilance decrement in neglect patients specifically only when they were required to maintain attention to spatial locations, but not verbal material. Lesioned voxels in the right PPC spanning a region between the intraparietal sulcus and inferior parietal lobe were significantly associated with this deficit. Finally, we compared performance on a task that required attention to be maintained either to visual patterns or spatial locations, matched for task difficulty. Again, we found a vigilance decrement but only when attention had to be maintained on spatial information. We conclude that sustaining attention to spatial locations is a critical function of the human right PPC which needs to be incorporated into models of normal parietal function as well as those of the clinical syndrome of hemispatial neglect.

Show MeSH
Related in: MedlinePlus