title: Envelope responses in single-trial EEG indicate attended speaker in a 'cocktail party'.
abstract: OBJECTIVE
  Recent studies have shown that auditory cortex better encodes the envelope of attended speech than that of unattended speech during multi-speaker ('cocktail party') situations. We investigated whether these differences were sufficiently robust within single-trial electroencephalographic (EEG) data to accurately determine where subjects attended. Additionally, we compared this measure to other established EEG markers of attention.
  
  
  METHODS
  High-resolution EEG was recorded while subjects engaged in a two-speaker 'cocktail party' task. Cortical responses to speech envelopes were extracted by cross-correlating the envelopes with each EEG channel. We also measured steady-state responses (elicited via high-frequency amplitude modulation of the speech) and alpha-band power, both of which have been sensitive to attention in previous studies. Using linear classifiers, we then examined how well each of these features could be used to predict the subjects' side of attention at various epoch lengths.
  
  
  RESULTS
  We found that the attended speaker could be determined reliably from the envelope responses calculated from short periods of EEG, with accuracy improving as a function of sample length. Furthermore, envelope responses were far better indicators of attention than changes in either alpha power or steady-state responses.
  
  
  CONCLUSIONS
  These results suggest that envelope-related signals recorded in EEG data can be used to form robust auditory BCI's that do not require artificial manipulation (e.g., amplitude modulation) of stimuli to function.
authors: Department of Cognitive Sciences, University of California, Irvine, CA 92697, USA.
authors: Cort
authors: C
authors: Horton
authors: Ramesh
authors: R
authors: Srinivasan
authors: Michael
authors: M
authors: D'Zmura
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000513:Alpha Rhythm; D001288:Attention / Q000502:physiology*; D001303:Auditory Cortex / Q000502:physiology*; D062207:Brain-Computer Interfaces; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007206:Individuality; D008297:Male; D015203:Reproducibility of Results; D055139:Sensory Gating / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult