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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

Spatial and non-spatial (verbal) tasks in Experiment 2. (A) In the spatial task, subjects were asked to respond whenever a letter was presented at either of the two predefined locations (indicated by red arrows in this figure, but not displayed during the actual experiment). The first test display shows a letter appearing at one of the target locations; the second display shows a letter at a non-target location. Broken-line circles indicate potential target positions; targets were displayed on a blank screen and there were no target markers. (B) In the non-spatial task, subjects responded whenever the letter ‘A’ or ‘C’ was presented regardless of their spatial location. The second test display shows a target stimulus; the first display shows a non-target.
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Figure 5: Spatial and non-spatial (verbal) tasks in Experiment 2. (A) In the spatial task, subjects were asked to respond whenever a letter was presented at either of the two predefined locations (indicated by red arrows in this figure, but not displayed during the actual experiment). The first test display shows a letter appearing at one of the target locations; the second display shows a letter at a non-target location. Broken-line circles indicate potential target positions; targets were displayed on a blank screen and there were no target markers. (B) In the non-spatial task, subjects responded whenever the letter ‘A’ or ‘C’ was presented regardless of their spatial location. The second test display shows a target stimulus; the first display shows a non-target.

Mentions: The task was developed using E-Prime software (Psychology Tools Inc.) Participants were tested using a laptop computer (Toshiba Satellite Pro XP 22), seated at a distance of ∼50 cm from the laptop screen (display 28.5 × 21.5 cm). During both spatial and non-spatial versions of the task subjects were presented with a sequence of black letters (consisting of ‘A’, ‘B’, ‘C’, ‘D’ or ‘E’, each ∼15 × 15 mm) on a uniform grey background at one of five positions along the vertical meridian of the screen (Fig. 5). Participants were asked to respond as quickly as possible by pressing the central button on a response box when they saw one of two predefined target stimuli. Stimuli were presented every 2 s, remaining on the screen for 1 s. Two hundred-fifty stimuli (targets and non-targets) were presented in total over a total period of ∼8 min, with 100 target stimuli shown during that time period. Reaction times (for button presses made within 1 s after stimulus onset) and numbers of correct responses were recorded.Figure 5


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

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

Spatial and non-spatial (verbal) tasks in Experiment 2. (A) In the spatial task, subjects were asked to respond whenever a letter was presented at either of the two predefined locations (indicated by red arrows in this figure, but not displayed during the actual experiment). The first test display shows a letter appearing at one of the target locations; the second display shows a letter at a non-target location. Broken-line circles indicate potential target positions; targets were displayed on a blank screen and there were no target markers. (B) In the non-spatial task, subjects responded whenever the letter ‘A’ or ‘C’ was presented regardless of their spatial location. The second test display shows a target stimulus; the first display shows a non-target.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 5: Spatial and non-spatial (verbal) tasks in Experiment 2. (A) In the spatial task, subjects were asked to respond whenever a letter was presented at either of the two predefined locations (indicated by red arrows in this figure, but not displayed during the actual experiment). The first test display shows a letter appearing at one of the target locations; the second display shows a letter at a non-target location. Broken-line circles indicate potential target positions; targets were displayed on a blank screen and there were no target markers. (B) In the non-spatial task, subjects responded whenever the letter ‘A’ or ‘C’ was presented regardless of their spatial location. The second test display shows a target stimulus; the first display shows a non-target.
Mentions: The task was developed using E-Prime software (Psychology Tools Inc.) Participants were tested using a laptop computer (Toshiba Satellite Pro XP 22), seated at a distance of ∼50 cm from the laptop screen (display 28.5 × 21.5 cm). During both spatial and non-spatial versions of the task subjects were presented with a sequence of black letters (consisting of ‘A’, ‘B’, ‘C’, ‘D’ or ‘E’, each ∼15 × 15 mm) on a uniform grey background at one of five positions along the vertical meridian of the screen (Fig. 5). Participants were asked to respond as quickly as possible by pressing the central button on a response box when they saw one of two predefined target stimuli. Stimuli were presented every 2 s, remaining on the screen for 1 s. Two hundred-fifty stimuli (targets and non-targets) were presented in total over a total period of ∼8 min, with 100 target stimuli shown during that time period. Reaction times (for button presses made within 1 s after stimulus onset) and numbers of correct responses were recorded.Figure 5

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