Table 1. Peak-to-peak MEP amplitudes obtained for the ECR and FCR muscles during probabilistic reward tasks.

	Reward probability
MEP amplitudes	10%	50%	90%	P*
Before reaction
Relative amplitude (FCR/ECR)	1.63±0.05	1.58±0.05	1.45±0.03	0.016
FCR muscle (mV)	1.32±0.03	1.11±0.03	1.16±0.02
ECR muscle (mV)	1.01±0.02	0.91±0.02	1.00±0.02
After reward stimulus
Relative amplitude (FCR/ECR)	1.50±0.04	1.41±0.03	1.64±0.04	<0.0001
FCR muscle (mV)	1.52±0.03	1.40±0.03	1.42±0.03
ECR muscle (mV)	1.28±0.03	1.33±0.04	1.15±0.03

Values are mean ± standard error of the mean. MEP, motor-evoked potential; ECR, extensor carpi radialis; FCR, flexor carpi radialis.

*Differences in MEP amplitudes between reward probabilities were analyzed by repeated measures analysis of variance.