title: Attention selectively modulates cortical entrainment in different regions of the speech spectrum.
abstract: Recent studies have uncovered a neural response that appears to track the envelope of speech, and have shown that this tracking process is mediated by attention. It has been argued that this tracking reflects a process of phase-locking to the fluctuations of stimulus energy, ensuring that this energy arrives during periods of high neuronal excitability. Because all acoustic stimuli are decomposed into spectral channels at the cochlea, and this spectral decomposition is maintained along the ascending auditory pathway and into auditory cortex, we hypothesized that the overall stimulus envelope is not as relevant to cortical processing as the individual frequency channels; attention may be mediating envelope tracking differentially across these spectral channels. To test this we reanalyzed data reported by Horton et al. (2013), where high-density EEG was recorded while adults attended to one of two competing naturalistic speech streams. In order to simulate cochlear filtering, the stimuli were passed through a gammatone filterbank, and temporal envelopes were extracted at each filter output. Following Horton et al. (2013), the attended and unattended envelopes were cross-correlated with the EEG, and local maxima were extracted at three different latency ranges corresponding to distinct peaks in the cross-correlation function (N1, P2, and N2). We found that the ratio between the attended and unattended cross-correlation functions varied across frequency channels in the N1 latency range, consistent with the hypothesis that attention differentially modulates envelope-tracking activity across spectral channels.
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States. Electronic address: baltzell@uci.edu.
authors.forename: Lucas S
authors.initials: LS
authors.lastname: Baltzell
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States.
authors.forename: Cort
authors.initials: C
authors.lastname: Horton
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States; Department of Speech and Hearing Sciences, Indiana University, IN, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States.
authors.forename: Virginia M
authors.initials: VM
authors.lastname: Richards
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: D'Zmura
authors.affiliation: Department of Cognitive Sciences, University of California, Irvine, CA, United States; Department of Biomedical Engineering, University of California, Irvine, CA, United States.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Srinivasan
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001288:Attention / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D012815:Signal Processing, Computer-Assisted; D013061:Speech Acoustics; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult
keywords: Attention; EEG; Entrainment; Speech envelopes