Conscious auditory perception relies more on sensory brain regions than on widespread fronto-parietal networks. In an fMRI study using a no-report inattentional deafness paradigm, 63 participants performed an auditory distractor task while task-irrelevant sounds were played. Those aware of the sounds showed strong activation in secondary auditory areas (superior temporal gyrus, sulcus, and middle temporal gyrus) and nodes of attention networks. Unaware processing activated only primary auditory regions. Comparing aware and unaware participants, auditory awareness was associated with extensive sensory activation, while fronto-parietal activation was weaker and only detected in Bayesian analysis. This suggests stimulus-specific sensory activity dominates conscious auditory perception.
Inattentional numbness, the somatosensory equivalent of inattentional blindness or deafness, was studied with fMRI in 44 participants who received weak electrical stimulation on the left hand while performing a demanding visual task. Half were told the tactile stimuli would be above detection threshold, half below. Ten participants did not consciously perceive the stimuli. Prior information did not significantly affect awareness. Awareness of stimuli increased activation in the contralateral secondary somatosensory cortex but not in the primary somatosensory cortex or frontoparietal areas. The results suggest that somatosensory awareness relies on higher somatosensory cortex areas and does not require strong activation in extended anterior or posterior networks seen when stimuli are task-relevant.