Donoghue Lab, Neuroscience Department, Brown University
Research
Motor Cortex Plasticity

Motor Cortex Plasticity research formerly conducted in our lab is now carried on by Investigator Mengia Rioult-Pedotti and Professor Anna Dunaevsky's lab (see http://neuroscience.brown.edu/DUNAEVSK/DUNAEVSK.html ).

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.

[Figure 1]
Figure 1: Consequences of motor skill learning on field-potential responses evoked in layer II/III horizontal connections of M1. ( a) Mirror-symmetric placement of stimulating (stim) and recording (rec) microelectrodes bilaterally in layers II/III of M1 in a coronal slice containing both hemispheres. wm, white matter. (b) Single-case examples of field potentials (averages of five sweeps), evoked at 60% maximum stimulation intensity from a single trained (top) and a single paired-control (bottom) animal. Dark lines represent the trained M1 or left M1, hatched lines, the untrained M1 or right M1. (c) Group average responses for trained (top, n = 7) and control (bottom, n = 20, paired and naive) rats at 60% maximal stimulation intensity, illustrating enhanced field potential in the horizontal pathway of M1 contralateral to the limb used in the reaching task. Same format as (b).

Selected Publications