Attention modulates earliest responses in the primary auditory and visual cortices.
A fundamental question about the neural correlates of attention concerns the earliest sensory processing stage that it can affect. We addressed this issue by recording magnetoencephalography (MEG) signals while subjects performed detection tasks, which required employment of spatial or nonspatial attention, in auditory or visual modality. Using distributed source analysis of MEG signals, we found that, contrary to previous studies that used equivalent current dipole (ECD) analysis, spatial attention enhanced the initial feedforward response in the primary visual cortex (V1) at 55-90 ms. We also found attentional modulation of the putative primary auditory cortex (A1) activity at 30-50 ms. Furthermore, we reproduced our findings using ECD modeling guided by the results of distributed source analysis and suggest a reason why earlier studies using ECD analysis failed to identify the modulation of earliest V1 activity.
Poghosyan
Vahe
V
Laboratory for Human Brain Dynamics, AAI Scientific Cultural Services Ltd., Office 501, Galaxias Building Block A, 33 Arch. Makarios III Avenue, 1065 Nicosia, Cyprus.
Ioannides
Andreas A
AA
D000161:Acoustic Stimulation / Q000379:methods; D001288:Attention / Q000502:physiology*; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D004307:Dose-Response Relationship, Radiation; D004569:Electroencephalography; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015225:Magnetoencephalography; D008297:Male; D008960:Models, Psychological; D017711:Nonlinear Dynamics; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology*