Cortico-cortical paired associative stimulation (ccPAS) over premotor-motor areas affects local circuitries in the human motor cortex via Hebbian plasticity

• DOI: 10.1016/j.neuroimage.2023.120027
• Publication Date: 2023-03-15T08:07:56Z
• Authors: Sonia Turrini; Francesca Fiori; Emilio Chiappini; Boris Lucero; Emiliano Santarne...; Alessio Avenanti
• Keywords: Hebbian theory; Premotor cortex; Brain stimulation

Transcranial magnetic stimulation (TMS) studies have shown that cortico-cortical paired associative (ccPAS) can strengthen connectivity between the ventral premotor cortex (PMv) and primary motor (M1) by modulating convergent input over M1 via Hebbian spike-timing-dependent plasticity (STDP). However, whether ccPAS locally affects activity remains unclear. We tested 60 right-handed young healthy humans in two studies, using a combination of dual coil TMS left PMv to probe manipulate PMv-to-M1 connectivity, single- paired-pulse assess neural within M1. provide evidence ccPAS, relying on repeated activations excitatory connections, acts During motor-evoked potentials (MEPs) induced PMv-M1 gradually increased. Following threshold for inducing MEPs different amplitudes decreased, input-output curve (IO) slope increased, highlighting increased corticospinal excitability. Moreover, reduced magnitude short-interval intracortical inhibition (SICI), reflecting suppression GABA-ergic interneuronal mechanisms M1, without affecting facilitation (ICF). These changes were specific strengthening as no modulations observed when reversing order during control protocol. findings expand prior research focused malleability at network-level, highlight local area activation (i.e., M1) induction. new mechanistic insights into physiological basis are relevant protocol optimization.