Multisensory integration: important issue to understand cognitive functions of the lateral prefrontal cortex

The lateral prefrontal cortex (LPFC) receives visual, auditory, and somatosensory information and has extensive local neural connections across different sensory regions. Therefore, this cortical area is likely an ideal site for investigating the neural mechanisms of multisensory integration and for understanding how such integration contributes to various cognitive functions. However, it has been shown that the LPFC is functionally heterogeneous and compartmentalized with respect to different sensory modalities and that each sensory area exhibits topographic representation of sensory information. Human neuroimaging studies indicate that although multiple sensory modalities are integrated in domain-general regions of the prefrontal cortex, each sensory modality is primarily processed within functionally segregated networks. These domain-general regions largely correspond to visual areas, whereas modality-specific regions are located adjacent to them. This organization suggests that each sensory modality is mainly processed by distinct functional networks in the prefrontal cortex. Despite the importance of multisensory integration for understanding prefrontal functions, relatively few studies have been conducted, with most focusing audio-visual integration in vocal communication. This limitation is partly due to the difficulty of activating prefrontal neurons using simple sensory stimuli and behavioral tasks, as well as the limitation of experimental data for computational approach and experimental techniques for investigating activities under multimodal conditions. Recently, several novel multisensory technologies have been developed, enabling the investigation of multisensory integration under conditions close to natural environments. These approaches are expected to advance our understanding of the neural mechanisms underlying multisensory integration in the prefrontal cortex.