title: Characterizing the roles of alpha and theta oscillations in multisensory attention.
abstract: Cortical alpha oscillations (8-13Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4-7Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta's association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention.
authors.affiliation: Volen Center for Complex Systems, Brandeis University, 415 South Street, Waltham MA 02453, USA. Electronic address: arielleskeller@gmail.com.
authors.forename: Arielle S
authors.initials: AS
authors.lastname: Keller
authors.affiliation: Swarthmore College, 500 College Ave, Swarthmore PA 19081, USA. Electronic address: lpayne1@swarthmore.edu.
authors.forename: Lisa
authors.initials: L
authors.lastname: Payne
authors.affiliation: Volen Center for Complex Systems, Brandeis University, 415 South Street, Waltham MA 02453, USA. Electronic address: vision@brandeis.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Sekuler
mesh_terms: D000328:Adult; D000513:Alpha Rhythm / Q000502:physiology*; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D012815:Signal Processing, Computer-Assisted; D013826:Theta Rhythm / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Alpha; Attention; EEG; Multisensory; Oscillations; Theta