title: Differentiating pathologic delta from healthy physiologic delta in patients with Alzheimer disease.
abstract: OBJECTIVE
  In patients with Alzheimer disease, the electroencephalogram during wakefulness shows pathologic signs of abundant, diffuse, large-amplitude delta activity. The carryover of this abnormal delta activity into non-rapid eye movement sleep raises the question of whether the observed delta electroencephalographic activity during sleep in Alzheimer disease in any way reflects normal physiologic delta activity slow-wave sleep. The objective of the study was to compare patients with Alzheimer disease with age-matched controls using an experimentally controlled procedure that can test the capacity of the nervous system to generate physiologic delta-frequency responses during sleep.
  
  
  METHODS
  Research sleep laboratory.
  
  
  METHODS
  Seven ambulatory patients with Alzheimer disease (mean age = 70.0 +/- 5.77 years) meeting the National Institute of Neurological and Communicative Diseases and Stroke and Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer disease and 8 controls (mean age = 69.25 +/- 4.95 years), underwent at least 1 night of evoked-potential recordings.
  
  
  RESULTS
  Data were collected during stage 2 sleep. Responses to stimuli were classified based on whether they produced a K-complex. Averages of K-complex responses were calculated, latencies and amplitudes of components evaluated, and K-complex incidence was determined. Relative to controls, subjects with Alzheimer disease produced significantly fewer evoked K-complexes (P < .001) and had substantially smaller N550 amplitudes than controls (P < .05). A lower probability of eliciting a K-complex correlated with greater dementia severity, as measured by the Mini Mental State Examination and Dementia Rating Scale.
  
  
  CONCLUSIONS
  Despite observed increases in pathologic delta-frequency electroencephalographic activity, patients with Alzheimer disease have an impaired capacity to generate normal physiologic delta responses during non-rapid eye movement sleep.
authors.affiliation: Compumedics Limited, Melbourne, Australia. kate@compumedics.com.au
authors.forename: Kate
authors.initials: K
authors.lastname: Crowley
authors.forename: Edith V
authors.initials: EV
authors.lastname: Sullivan
authors.forename: Elfar
authors.initials: E
authors.lastname: Adalsteinsson
authors.forename: Adolf
authors.initials: A
authors.lastname: Pfefferbaum
authors.forename: Ian M
authors.initials: IM
authors.lastname: Colrain
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D003700:Delta Rhythm; D004569:Electroencephalography; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests