Intraparietal
Bimodal Neurones Delineating Extrinsic Space Through Intrinsic
Actions
M. Tanaka, S. Obayashi, H. Yokochi, S. Hihara, M. Kumashiro, Y. Iwamura, & A. Iriki |
We
can mentally calibrate the directions of our bodily movements into
visual coordinate systems to achieve purposeful actions in space.
Alternatively, we can apprehend characteristics of the peri-personal
space through actions performed by our own body parts. Such interactions
between representations of our body motions and extrinsic space should
occur in the intraparietal cortices, where the hierarchically processed
somatosensory information adjoins the information on spatial vision
processed along the dorsal stream. In this brain area of monkeys,
we analyzed the response properties of "bimodal joint neurones",
which responded simultaneously to forearm joint displacements and
visual stimuli moving in one direction in space. For the majority
of these neurones, the directions of hand movements in space as a
result of adequate joint displacements were congruent with the preferred
directions of the moving visual stimuli. When the arm position was
rotated, the preferred direction of the joint displacement became
inverted so as to match the induced hand movement in space with the
preferred visual stimulus direction. On the other hand, in some neurones
the visual preferred direction became inverted when the joint was
rotated, becoming to match the preferred direction of joint displacement.
Hence, intraparietal neurones appear not only to represent mental
recalibration of intrinsic movements into extrinsic coordinates,
but also render delineation of extrinsic space through intrinsic
actions. Key words: awake monkeys, intraparietal cortex, single unit recordings, bimodal neurones, visuo-somatic integration |