title: Double peaked P1 visual evoked potentials in healthy ageing.
abstract: OBJECTIVE
  To robustly examine the prevalence of the double peaked P1 visual evoked potential in healthy younger and older adult populations.
  
  
  METHODS
  The evoked potentials and spectral power changes to simple visual stimuli of 26 healthy younger (M=20.0 y) and 26 healthy older adults (M=76.0 y) were examined.
  
  
  RESULTS
  Group and individual analyses showed a clear effect of age on P1 morphology and amplitude. Older adults showed significantly lower P1 amplitude and 44% of older adults showed a double peaked P1 compared to 12% of younger adults. Double peaked P1 responses were associated with an increase in spectral power in the gamma range.
  
  
  CONCLUSIONS
  The double peaked P1 may be more prevalent in older adults than previously demonstrated and may represent a de-synchronisation of the cortical sources of the visual P1 in healthy ageing. Increased power in post stimulus gamma in the double peak group may be indicative of compensatory neural processing.
  
  
  CONCLUSIONS
  Clinically the prevalence of the double peaked P1 may have been underestimated, and its reflectance of demyelinating disease overestimated. Experimentally the results suggest that any investigation of visual processing in older adults must control for early changes in P1 morphology.
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK. Electronic address: George.Stothart@bristol.ac.uk.
authors.forename: G
authors.initials: G
authors.lastname: Stothart
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK.
authors.forename: A
authors.initials: A
authors.lastname: Tales
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK.
authors.forename: C
authors.initials: C
authors.lastname: Hedge
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK.
authors.forename: N
authors.initials: N
authors.lastname: Kazanina
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D010775:Photic Stimulation / Q000379:methods; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
keywords: Ageing; Compensation; Double peak; Gamma; P1; Visual evoked potentials