Right hemisphere dominance for auditory attention and its modulation by eye position: an event related fMRI study.
OBJECTIVE
Previous neuroimaging studies of oddball tasks and other paradigms measuring attention processes support right hemisphere dominance for attentional processes. Using an auditory selective attention task, we studied the functional asymmetry of the human brain in response to attended or unattended deviant tones. Secondly, we examined whether a congruency or a discrepancy between audio-spatial and visuo-spatial cued attentional resources may influence the activity elicited by an auditory selective attention task.


METHODS
We used event-related functional magnetic resonance imaging (fMRI) to study healthy adults as they performed an auditory oddball task in which a spatial-cued instruction indicated the ear to attend a monaural deviant tone. We addressed the question of congruency/discrepancy between attentional resources by using three different eye positions during the performance of the auditory oddball task.


RESULTS
Relative to standard tones, both attended and unattended deviant tones (DTs) presented to either ear elicit the activation of a widespread bilaterally distributed cortical and subcortical network. A subset of this network, essentially frontal and temporal areas, showed not only greater right than left activity but an enhancement of this rightward asymmetry in response to attended DTs. The only cortical region that showed a leftward asymmetry in response to attended DTs overlapped Heschl gyrus and planum temporale, unmasking a left hemisphere preference of both primary and secondary auditory cortex for processing simple attended monaural stimuli. Questioning the impact of eye position during auditory oddball task, we observed a lesser activity in right integrative crossmodal areas (superior temporal sulcus, opercular part of the inferior frontal gyrus, pre-SMA) when the eye positions were contralateral to detected DTs. These regions may be tuned to best respond when both visuo-spatial and audio-spatial attentional resources work together.


CONCLUSIONS
These results support the assumption that the right hemisphere is preferentially engaged in processing audio-spatial attentional resources and underline the interest to study the crossmodal integration of attentional resources by the mean of the detection of DTs in different eye positions.
Petit
Laurent
L
Groupe d'Imagerie Neurofonctionnelle, UMR 6194 CNRS - CEA - University of Caen and University Paris Descartes, GIP Cyceron, Bd. H. Becquerel, BP 5229, 14074 Caen Cedex, France. lpetit@cyceron.fr
Simon
Grégory
G
Joliot
Marc
M
Andersson
Frédéric
F
Bertin
Thomas
T
Zago
Laure
L
Mellet
Emmanuel
E
Tzourio-Mazoyer
Nathalie
N
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D003463:Cues; D003627:Data Interpretation, Statistical; D004292:Dominance, Cerebral / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000502:physiology; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology