Enhanced cortical effects of auditory stimulation and auditory attention in healthy individuals prone to auditory hallucinations during partial wakefulness.
Neuroimage August 1, 2011 Lourence L Lewis-Hanna, Michael D Hunter, Tom F D Farrow et al.
People who experience auditory hallucinations while falling asleep (hypnagogic) or waking up (hypnopompic) show heightened brain sensitivity to sounds. In a behavioral study, 26 hallucinators reported greater subjective sensitivity to environmental sounds than 74 controls. Two fMRI experiments with 12 hallucinators and 12 matched controls found that hallucinators had greater speech-evoked brain activation in the left supramarginal gyrus. When directing attention to sound, they showed stronger activation in the anterior cingulate gyrus. These findings suggest that a tendency toward hallucinations involves increased auditory and polysensory cortex sensitivity, possibly due to enhanced attentional bias from the anterior cingulate gyrus, supporting the idea that top-down modulation of auditory cortex responses is key to generating auditory hallucinations.