Automatic Discrimination of Auditory Stimuli Perceived by the Human Brain

Humans are able to perceive small difference of sound frequency but it is still unknown how the difference in frequency information is represented at the level of the primary sensory cortex. Indeed, analysis of fMRI imaging identified tonotopic maps through the auditory pathways to the primary sensory cortex. These maps are unfortunately too coarse to show ultra-fine discrimination. Then, the hypothesis is that this small frequency differences are recognised thanks to the information coming from a large set of auditory neurons. To investigate this possibility, a multi-voxel pattern discriminating analysis of the response of BOLD-fMRI in the bilateral auditory cortex to tonal stimuli with different shift in frequency was performed. Our results suggest that small shifts in the frequency are easily classified compared with big shifts and that multiple areas of the auditory cortex are involved in the tone recognition.