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Patrizia Fattori, Kostas Hadjidimitrakis, Federica Bertozzi, Rossella Breveglieri, Claudio Galletti; TEMPORAL STABILITY OF REFERENCE FRAMES IN A 3D REACHING TASK IN MONKEY AREA V6A. Journal of Vision 2014;14(10):301. doi: https://doi.org/10.1167/14.10.301.
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© ARVO (1962-2015); The Authors (2016-present)
Neurons in the medial posterior parietal area V6A of macaques show spatial modulations during all the phases of an instructed delay reaching task towards visual targets placed either in a frontal plane, or in 3D space (Fattori et al., Eur. J. Neurosci 2005; Hadjidimitrakis et al., Cereb Cortex 2013a). Furthermore, shortly before and during the execution of reaching movements towards foveated targets that started from different hand positions, V6A neurons were found to encode targets either in a pure body-centered frame of reference, or in mixed body/hand-centred coordinates (Hadjidimitrakis et al., Cereb Cortex 2013b). In contrast to nearby areas such as the Parietal Reach Region (PRR, Chang and Snyder, PNAs 2010), no significant evidence of pure hand-centred coding was found in V6A. Here, we investigated the presence of hand-centred coding in earlier epochs of the task, i.e. immediately after target fixation and in the subsequent early part of the delay period and examined whether the reference frames in individual neurons are stable across the task epochs. We present data from single neurons recorded from V6A in two Macaque monkeys and report no evidence of hand-centred coding also in the earlier phases of the task. Shortly after target fixation and throughout the early delay period, the population of V6A neurons used either body-centred, or mixed body/ hand-centred reference frames. Most of the cells spatially tuned across multiple epochs showed consistent reference frames during the task progress. Rather surprisingly, as movement onset approached, a small but significant proportion of cells shifted from mixed body/hand-centred frames to pure body-centred coordinates. These findings suggest that in V6A the signal of target position relative to the hand is more prevalent shortly after fixation, and is gradually transformed to yield more egocentric representations in the pre- and movement epochs.
Meeting abstract presented at VSS 2014
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