スケジュール

Chair：Sho K Sugawara and Kenji Ogawa

講演者

Neurological Basis of Handedness: Brain-Spinal Networks, and Future Clinical Insights

Hand dexterity is a hallmark of higher primates, with humans displaying a consistent hand preference in daily activities. The evolution of direct, monosynaptic connection from the primary motor cortex to the spinal cord parallels the development of hand dexterity and lateralization of hand preference. In non-human mammals, indirect, multi-synaptic connections between bilateral primary motor cortices and the spinal cord also contribute to the control of dexterous hand movement. However, it remains unknown how the direct and indirect corticospinal pathways work in concert to control unilateral hand movement with lateralized preference in humans. Here we elucidated this puzzle by employing simultaneous functional magnetic resonance imaging of the brain and spinal cord with a combination of computational network modeling. In this talk, we will discuss an asymmetric functional organization of the two corticospinal networks and a functionally lateralized motor nervous system that underlies the behavioral asymmetry of handedness in humans. I will also provide insights into future projects, such as pain and perception, from a clinical perspective as a spine surgeon.

Perceptual, behavioral, and neural adaptation to independent supernumerary sixth finger

Can the human brain adapt to a supernumerary limb? The rubber hand illusion experiments and other studies about the embodiment of body parts suggested the plasticity of our body representation in the brain. However, since previous studies focused on substitutional artificial limbs controlled by specific body movement, it remains unknown whether the human brain integrates independent artificial limbs into the body system. In this study, we developed an independent supernumerary sixth finger and performed cognitive measurements, behavioral tests, and brain imaging to examine whether body representation is altered by the training for using the sixth finger. Our results suggest that short-time (less than one hour) adaptation to the sixth finger enables participants to perceive a sense of ownership towards the sixth finger and the change of subjective perception correlates with that of the behavioral measurements. fMRI experiments also suggest that brain activity evoked by innate finger movements are altered by the adaptation to the sixth finger. To examine the effect of the difference in the position of attachment, we also developed another type of sixth finger that can be attached between the thumb and the index finger. We will discuss the preliminary results from experiments using this new sixth finger.