Selective Modulation of Auditory Cortical Alpha Activity in an Audiovisual Spatial Attention Task

Abstract

Despite substantial research on attentional modulations of visual alpha activity, doubts remain as to the existence and functional relevance of auditory cortical alpha-band oscillations. It has been argued that auditory cortical alpha does not exist, cannot be measured noninvasively, or that it is dependent on visual alpha generators. This study aimed to address these remaining doubts concerning auditory cortical alpha. A magnetoencephalography study was conducted using a combined audiovisual spatial cueing paradigm. In each trial, a cue indicated the side (left or right) and the modality (auditory or visual) to attend, followed by a short lateralized auditory or visual stimulus. Participants were instructed to respond to the stimuli by a button press. Results show that auditory cortical alpha power is selectively modulated by the audiospatial, but not the visuospatial, attention task. These findings provide further evidence for a distinct auditory cortical alpha generator, which can be measured noninvasively.

Spatiotemporal dynamics of auditory attention synchronize with speech

“…Two indices of attentional modulation of neural responses were calculated for each time-frequency bin (−2 to 10 s; 1-20 Hz). First, the attentional modulation index [AMI X = (X att_left -X att_right )/(X att_left + X att_right )] revealed a spatially resolved measure of attention effects on intertrial phase coherence (1-5 Hz; AMI ITPC ) and alpha power (8)(9)(10)(11)(12) Hz; AMI α ) at each sensor (X being either ITPC or α power; Fig. 3).…”

“…5). Thus, alpha power lateralization not only codes the locus of attention in space (10,11,13) but also the structure of the stimulus in time.…”

“…Spatial attention induces increasing and decreasing power of neural alpha oscillations (8)(9)(10)(11)(12) Hz) in brain regions ipsilateral and contralateral to the locus of attention, respectively. This study tested whether the hemispheric lateralization of alpha power codes not just the spatial location but also the temporal structure of the stimulus.…”

“…The power of alpha oscillations (8)(9)(10)(11)(12) is modulated by the degree of selective attention to a behaviorally relevant stimulus (4)(5)(6). Attentive focusing to one side in auditory, visual, or tactile space leads to a relative decrease in alpha power in contralateral compared with ipsilateral sensory brain regions (7)(8)(9)(10) and governs success of selective attention, that is, of isolating one stimulus at a specific spatial location (11)(12)(13) in the context of other distracting stimuli. In speech, however, spatial selective attention alone does not suffice for successful speech comprehension given the multiple timescales (e.g., syllable and word rate) over which speech varies.…”

A right‐ear bias of auditory selective attention is evident in alpha oscillations

“…Although the majority of evidence regarding the alpha band comes from the visual and somatosensory systems, there is a suggestion that alpha rhythms signify an inhibitory process in auditory attention as well (Dubé et al, 2013; Banerjee et al, 2011). The difference in alpha power across hemispheres indicates the lateralization of auditory attention (Frey et al, 2014; Ahveninen et al, 2013; Kerlin et al, 2010). The relative increase in alpha power contralateral to unattended stimuli supports the interpretation that alpha activity represents reduced processing.…”