September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Impairments of visually-guided reach plans after transcranial magnetic stimulation over the human medial posterior parietal cortex
Author Affiliations & Notes
  • Rossella Breveglieri
    University of Bologna
  • Annalisa Bosco
    University of Bologna
  • Sara Borgomaneri
    University of Bologna
    IRCCS Santa Lucia Foundation, Rome
  • Alessia Tessari
    University of Bologna
  • Claudio Galletti
    University of Bologna
  • Alessio Avenanti
    University of Bologna
    Catholic University of Maule, Chile
  • Patrizia Fattori
    University of Bologna
  • Footnotes
    Acknowledgements  Fondazione Cassa di Risparmio in Bologna (CARISBO internazionalizzazione 2019), Ministero dell'Università e della Ricerca (MIUR, PRIN2017KZNZLN, PRIN2017N7WCLP), Fondazione del Monte di Bologna e Ravenna (339bis/2017), Bial Foundation (347/18), Ministero della Salute, Italy (GR-2018-12365733).
Journal of Vision September 2021, Vol.21, 2042. doi:
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      Rossella Breveglieri, Annalisa Bosco, Sara Borgomaneri, Alessia Tessari, Claudio Galletti, Alessio Avenanti, Patrizia Fattori; Impairments of visually-guided reach plans after transcranial magnetic stimulation over the human medial posterior parietal cortex. Journal of Vision 2021;21(9):2042.

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      © ARVO (1962-2015); The Authors (2016-present)

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The medial posterior parietal cortex (mPPC) is involved in the visual guidance of reaching. Although several studies investigated reaching performed towards different directions, only a few correlational studies investigated different depths. Here, we studied the causal role of mPPC (putatively, human area V6A - hV6A) in encoding depth and direction of reaching performed under visual guidance. Fifteen healthy humans performed a visually-guided reaching task which required different eye-hand configurations (foveal and peripheral reaching): Constant gaze configuration (central gaze fixation while reaching to one of 8 peripheral targets); Constant reach configuration (reaching to the central target while fixating one of 8 peripheral targets); Foveal reach configuration (coincident fixation and reaching targets). We applied single-pulse transcranial magnetic stimulation (TMS) over the left hV6A at 100 or 200 ms after reaction time onset, over area V1 to check for non-specific effect of TMS, and in a SHAM condition with the coil tilted 90° over the vertex. We found a site-specific and time-dependent effect: in particular, TMS delivered over hV6A 200ms after the Go signal affected the encoding of the depth of reaching by decreasing the accuracy (in depth) of movements towards targets located farther with respect to the gazed position, but only when they were far from the body (Constant gaze configuration: repeated-measure ANOVA, Stimulation Condition x Stimulation Time x Depth interaction, F(4,56) = 3.00; p = 0.03, partial η2 = 0.17). Reach end-point precision was not affected by TMS over hV6A. The effectiveness of both retinotopic (farther with respect to the gaze) and spatial (far from the body) position is in agreement with the presence in the monkey V6A of neurons employing either retinotopic, spatial, or mixed reference frames during reach plan. This work provides the first causal evidence of the critical role of hV6A in planning visually-guided reaching movements in depth.


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