Integration of touch and sound in auditory cortex

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Sensory Integration

Background:

• The brain integrates sensory information for a coherent environmental perception.
• Multisensory integration is known to occur in association cortices.
• Evidence suggests integration may also happen in early sensory areas.

Purpose of the Study:

• To investigate multisensory integration in early auditory cortex.
• To confirm or refute the hypothesis of early sensory integration.
• To characterize the nature of touch-sound integration in the auditory cortex.

Main Methods:

• High-resolution functional magnetic resonance imaging (fMRI) in anesthetized macaque monkeys.
• Quantification of auditory (broad-band noise) and tactile (hand/foot) stimulation.
• Localization of integration effects relative to the primary auditory cortex.

Main Results:

• Supra-additive integration of touch and sound was demonstrated.
• Integration occurred in the caudal auditory belt, posterior and lateral to primary auditory cortex.
• Integration was stronger for temporally coincident stimuli and followed the principle of inverse effectiveness.

Conclusions:

• Multisensory integration occurs early in the auditory pathway, near primary sensory areas.
• Integration in anesthetized animals suggests mediation by preattentive, bottom-up mechanisms.
• These findings challenge the traditional view of sensory processing hierarchies.