title: Dynamic attentional modulation of vision across space and time after right hemisphere stroke and in ageing.
abstract: BACKGROUND
  Attention modulates the availability of sensory information to conscious perception. In particular, there is evidence of pathological, spatial constriction of the effective field of vision in patients with right hemisphere damage when a central task exhausts available attentional capacity. In the current study we first examined whether this constriction might be modulated across both space and time in right hemisphere stroke patients without neglect. Then we tested healthy elderly people to determine whether non-pathological ageing also leads to spatiotemporal impairments of vision under conditions of high attention load.
  
  
  METHODS
  Right hemisphere stroke patients completed a task at fixation while attempting to discriminate letters appearing in the periphery. Attentional load of the central task was modulated by increasing task difficulty. Peripheral letters appeared simultaneously with the central task or at different times (stimulus onset asynchronies, SOAs) after it. In a second study healthy elderly volunteers were tested with a modified version of this paradigm.
  
  
  RESULTS
  Under conditions of high attention load right hemisphere stroke patients have a reduced effective visual field, over a significantly extended 'attentional blink', worse for items presented to their left. In the second study, older participants were unable to discriminate otherwise salient items across the visual field (left or right) when their attention capacity was loaded on the central task. This deficit extended temporally, with peripheral discrimination ability not returning to normal for up to 450 msec.
  
  
  CONCLUSIONS
  Dynamically tying up attention resources on a task at fixation can have profound effects in patient populations and in normal ageing. These results demonstrate that items can escape conscious detection across space and time, and can thereby impact significantly on visual perception in these groups.
authors.affiliation: Centre for Cognition and Neuroimaging, Department of Psychology, Brunel University, Uxbridge, UK. charlotte.russell@brunel.ac.uk
authors.forename: Charlotte
authors.initials: C
authors.lastname: Russell
authors.forename: Paresh
authors.initials: P
authors.lastname: Malhotra
authors.forename: Cristiana
authors.initials: C
authors.lastname: Deidda
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology* / Q000523:psychology*; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001767:Blinking; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000473:pathology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D020521:Stroke / Q000523:psychology*; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*