title: Least-squares (LS) deconvolution of a series of overlapping cortical auditory evoked potentials: a simulation and experimental study.
abstract: OBJECTIVE
  To evaluate the viability of disentangling a series of overlapping 'cortical auditory evoked potentials' (CAEPs) elicited by different stimuli using least-squares (LS) deconvolution, and to assess the adaptation of CAEPs for different stimulus onset-asynchronies (SOAs).
  
  
  METHODS
  Optimal aperiodic stimulus sequences were designed by controlling the condition number of matrices associated with the LS deconvolution technique. First, theoretical considerations of LS deconvolution were assessed in simulations in which multiple artificial overlapping responses were recovered. Second, biological CAEPs were recorded in response to continuously repeated stimulus trains containing six different tone-bursts with frequencies 8, 4, 2, 1, 0.5, 0.25 kHz separated by SOAs jittered around 150 (120-185), 250 (220-285) and 650 (620-685) ms. The control condition had a fixed SOA of 1175 ms. In a second condition, using the same SOAs, trains of six stimuli were separated by a silence gap of 1600 ms. Twenty-four adults with normal hearing (<20 dB HL) were assessed.
  
  
  RESULTS
  Results showed disentangling of a series of overlapping responses using LS deconvolution on simulated waveforms as well as on real EEG data. The use of rapid presentation and LS deconvolution did not however, allow the recovered CAEPs to have a higher signal-to-noise ratio than for slowly presented stimuli. The LS deconvolution technique enables the analysis of a series of overlapping responses in EEG.
  
  
  CONCLUSIONS
  LS deconvolution is a useful technique for the study of adaptation mechanisms of CAEPs for closely spaced stimuli whose characteristics change from stimulus to stimulus. High-rate presentation is necessary to develop an understanding of how the auditory system encodes natural speech or other intrinsically high-rate stimuli.
authors: HEARing Co-operative Research Centre, Australia. Department of Linguistics, Macquarie University, NSW, Australia. National Acoustic Laboratories, NSW, Australia.
authors: Fabrice
authors: F
authors: Bardy
authors: Bram
authors: B
authors: Van Dun
authors: Harvey
authors: H
authors: Dillon
authors: Robert
authors: R
authors: Cowan
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000465:Algorithms; D001303:Auditory Cortex / Q000502:physiology*; D003198:Computer Simulation; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D059629:Signal-To-Noise Ratio