Limits...
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.

Show MeSH

Related in: MedlinePlus

Sustained attention task with pattern stimuli. (A) This task was analogous to that displayed in Fig. 5, only patterns were used instead of letters. On the non-spatial variant of the task, participants were asked to respond only when presented with one of two target patterns, regardless of their spatial location (illustrated here). On the spatial task, they were asked to respond when pattern stimuli appeared in one of the two target locations, regardless of their identity. (B) Neglect patients’ error rates over time on spatial and non-spatial pattern tasks (Error Bars = SEM). (C) Target sensitivity (d′) for neglect patients across time on the spatial and non-spatial (pattern) tasks.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2664449&req=5

Figure 8: Sustained attention task with pattern stimuli. (A) This task was analogous to that displayed in Fig. 5, only patterns were used instead of letters. On the non-spatial variant of the task, participants were asked to respond only when presented with one of two target patterns, regardless of their spatial location (illustrated here). On the spatial task, they were asked to respond when pattern stimuli appeared in one of the two target locations, regardless of their identity. (B) Neglect patients’ error rates over time on spatial and non-spatial pattern tasks (Error Bars = SEM). (C) Target sensitivity (d′) for neglect patients across time on the spatial and non-spatial (pattern) tasks.

Mentions: Task conditions were identical to those in Experiment 2, but instead of being presented with a sequence of black letters participants were shown a series of separate pattern stimuli (15 × 15 mm) at the same five vertical locations on the laptop screen. As in Experiment 2, they were asked to respond to individual locations on the spatial variant of the task, whereas they were now asked to respond to two (out of a possible 5) patterns on the non-spatial task (Fig. 8A).Figure 8


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

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

Sustained attention task with pattern stimuli. (A) This task was analogous to that displayed in Fig. 5, only patterns were used instead of letters. On the non-spatial variant of the task, participants were asked to respond only when presented with one of two target patterns, regardless of their spatial location (illustrated here). On the spatial task, they were asked to respond when pattern stimuli appeared in one of the two target locations, regardless of their identity. (B) Neglect patients’ error rates over time on spatial and non-spatial pattern tasks (Error Bars = SEM). (C) Target sensitivity (d′) for neglect patients across time on the spatial and non-spatial (pattern) tasks.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 8: Sustained attention task with pattern stimuli. (A) This task was analogous to that displayed in Fig. 5, only patterns were used instead of letters. On the non-spatial variant of the task, participants were asked to respond only when presented with one of two target patterns, regardless of their spatial location (illustrated here). On the spatial task, they were asked to respond when pattern stimuli appeared in one of the two target locations, regardless of their identity. (B) Neglect patients’ error rates over time on spatial and non-spatial pattern tasks (Error Bars = SEM). (C) Target sensitivity (d′) for neglect patients across time on the spatial and non-spatial (pattern) tasks.
Mentions: Task conditions were identical to those in Experiment 2, but instead of being presented with a sequence of black letters participants were shown a series of separate pattern stimuli (15 × 15 mm) at the same five vertical locations on the laptop screen. As in Experiment 2, they were asked to respond to individual locations on the spatial variant of the task, whereas they were now asked to respond to two (out of a possible 5) patterns on the non-spatial task (Fig. 8A).Figure 8

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