Learning-Induced LTP in Neocortex

TLDR

The hypothesis that learning occurs via LTP‑ and LTD‑like mechanisms is widely held but unproven, assuming synapses are modifiable, change with learning, and strengthen through an LTP‑like mechanism. The study investigated whether learning strengthened horizontal connections in rat motor cortex through LTP. We found that trained motor cortex synapses reached near‑maximum modification, with no change in modification range, but LTP was markedly reduced and LTD enhanced, supporting the role of LTP in learning‑induced synaptic strengthening.

Abstract

The hypothesis that learning occurs through long-term potentiation (LTP)- and long-term depression (LTD)-like mechanisms is widely held but unproven. This hypothesis makes three assumptions: Synapses are modifiable, they modify with learning, and they strengthen through an LTP-like mechanism. We previously established the ability for synaptic modification and a synaptic strengthening with motor skill learning in horizontal connections of the rat motor cortex (MI). Here we investigated whether learning strengthened these connections through LTP. We demonstrated that synapses in the trained MI were near the ceiling of their modification range, compared with the untrained MI, but the range of synaptic modification was not affected by learning. In the trained MI, LTP was markedly reduced and LTD was enhanced. These results are consistent with the use of LTP to strengthen synapses during learning.