RT Journal Article
SR Electronic
T1 Early Neural Correlates of Conscious Somatosensory Perception
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 5248
OP 5258
DO 10.1523/JNEUROSCI.0141-05.2005
VO 25
IS 21
A1 Satu Palva
A1 Klaus Linkenkaer-Hansen
A1 Risto Näätänen
A1 J. Matias Palva
YR 2005
UL http://www.jneurosci.org/content/25/21/5248.abstract
AB The cortical processing of consciously perceived and unperceived somatosensory stimuli is thought to be identical during the first 100-120 ms after stimulus onset. Thereafter, the electrophysiological correlates of conscious perception have been shown to be reflected in the N1 component of the evoked response as well as in later (>200 ms) nonstimulus-locked γ-band (28-50 Hz) oscillatory activity. To evaluate more specifically the time course and correlation of neuronal oscillations with conscious perception, we recorded neuromagnetic responses to threshold-intensity somatosensory stimuli. We show here that cortical broadband activities phase locked to the subsequently perceived stimuli in somatosensory, frontal, and parietal regions as early as 30-70 ms from stimulus onset, whereas the phase locking to the unperceived stimuli was weak and primarily restricted to somatosensory regions. Such stimulus locking also preceded the perceived stimuli, indicating that the phase of ongoing cortical activities biases subsequent perception. Furthermore, the data show that the stimulus locking was present in the θ- (4-8 Hz), α- (8-14 Hz), β- (14-28 Hz), and γ- (28-40 Hz) frequency bands, of which the widespread α-band component was dominant for the consciously perceived stimuli but virtually unobservable for the unperceived stimuli. Our results show that the neural correlates of conscious perception are already found during the earliest stages of cortical processing from 30 to 150 ms after stimulus onset and suggest that α-frequency-band oscillations have a role in the neural mechanisms of sensory awareness.