PLoS ONE (Jan 2023)

Can static Rorschach stimuli perceived as in motion affect corticospinal excitability?

  • Agata Andò,
  • Francesca Garbarini,
  • Luciano Giromini,
  • Adriana Salatino,
  • Alessandro Zennaro,
  • Raffaella Ricci,
  • Carlotta Fossataro

DOI
https://doi.org/10.1371/journal.pone.0287866
Journal volume & issue
Vol. 18, no. 7
p. e0287866

Abstract

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It has been proposed that seeing human movement or activity (M), while trying to say what the static Rorschach inkblot design look like, is accompanied by Mirror Neuron System (MNS)-like mirroring activity in the brain. The present study aimed to investigate whether the Rorschach cards eliciting M responses could affect the excitability of the motor cortex by recording motor evoked potentials (MEPs) elicited by single-pulse TMS over the primary motor cortex (M1). We hypothesized that Rorschach inkblot stimuli triggering the viewer's experience of human movement would increase corticospinal excitability. Twenty-one healthy volunteers (15 women) participated in the preliminary experiment, while another different sample of twenty-two healthy participants (11 women) ranging in age from 21 to 41 years was enrolled in the main experiment. Our results showed that the Rorschach cards known to be associated with a high number of M responses elicited human movement both as automatic internal sensations and as verbal production of responses involving human movement. However, contrary to our hypothesis, the reported internal feeling of human movement had no corresponding physiological counterpart, as the amplitude of MEPs did not increase. Possible and innovative explanations for the involvement of bottom-up and top-down processes were provided.