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Patrizia Fattori, Kostas Hadjidimitrakis, Giulia Dal Bo', Annalisa Bosco, Rossella Breveglieri, Claudio Galletti; Depth modulations for reaching across superior parietal lobule. Journal of Vision 2015;15(12):189. doi: 10.1167/15.12.189.
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© ARVO (1962-2015); The Authors (2016-present)
Single cell recordings in the awake monkey have so far neglected the depth dimension of visuomotor transformations for reaching. In the few cases where depth has been taken into account, direction has been left apart. The coexistence of depth and direction information for reaching requires further studies, as usually our reaching movements in real life occurr by changes in the distance and laterality of our hand positions in peripersonal space. Here, we investigated how reach depth and reach direction interact at single cell level in two areas of superior parietal cortex (SPL): area V6A and PEc, located caudally in the SPL, in a region of the posterior parietal cortex medial to area MIP/PRR. Two macaque monkeys performed a fixation-to-reach task in 3-dimensional space, toward foveated targets located at different distances and lateralities. We analized the spatial tuning of about 200 neurons per area in several phases of this delay reaching task: target fixation, early and late delay period, movement and holding times. We found that depth and direction signals influenced jointly a large number of neurons in both areas in all epochs of the task considered, with PEc showing more independent processing of depth and direction, especially before the arm movement onset. In PEc, the effect of direction was more prevalent than depth before reaching execution while the reverse was true for depth. In V6A, depth and direction similarly influenced neural activity for the entire trial. These findings suggest the involvement of both areas in visuospatial and action representations in 3D peripersonal space, with a caudo-rostral trend from a joint processing of depth and direction signals for eye position and reach execution in V6A to an encoding of depth related mostly to arm movement in PEc. These data reflect a rostro-caudal trend similar to that observed in human fMRI studies.
Meeting abstract presented at VSS 2015
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