title: Attention-based modulation of tactile stimuli: a comparison between prefrontal lesion patients and healthy age-matched controls.
abstract: OBJECTIVE
  To investigate the role of the prefrontal cortex in attention-based modulation of cortical somatosensory processing.
  
  
  METHODS
  Six prefrontal stroke patients were compared with eleven neurologically intact older adults during a vibrotactile discrimination task. All subjects attended to stimuli on one digit while ignoring distracter stimuli on a separate digit of the same hand. Subjects were required to report infrequent targets on the attended digit only. Throughout testing electroencephalography was used to measure event-related potentials for both task-relevant and irrelevant stimuli.
  
  
  RESULTS
  Prefrontal patients demonstrated significant changes in cortical somatosensory processing based on attention compared to age-matched controls. This was evident both in early unimodal somatosensory processing (i.e. P100) and in later cortical processing stages (i.e. long-latency positivity). Moreover, there was a tendency towards a tonic loss of inhibition over early somatosensory cortical processing (i.e. P50).
  
  
  CONCLUSIONS
  The attention-based modulation noted for neurologically intact older adults was absent in prefrontal lesion patients.
  
  
  CONCLUSIONS
  The present study highlights the important role of prefrontal regions in sustaining inhibition over early sensory cortical processing stages and in modifying somatosensory transmission based on task-relevance. Notably these deficits extend beyond those previously shown to occur as a function of age.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada; Heart and Stroke Foundation Centre for Stroke Recovery, ON, Canada. Electronic address: d.bolton@qub.ac.uk.
authors.forename: David A E
authors.initials: DA
authors.lastname: Bolton
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada; Heart and Stroke Foundation Centre for Stroke Recovery, ON, Canada.
authors.forename: W Richard
authors.initials: WR
authors.lastname: Staines
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology*; D001930:Brain Injuries / Q000209:etiology / Q000473:pathology*; D016022:Case-Control Studies; D004192:Discrimination, Psychological; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory; D005260:Female; D005385:Fingers / Q000294:innervation; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000503:physiopathology*; D020521:Stroke / Q000150:complications; D014110:Touch / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*
keywords: Attention; Event-related potential; Oddball; Prefrontal lesion; Sensory-gating; Tactile