Figure 1.

Correlation of Short Latency Afferent Inhibition (SAI) with stage of Parkinson’s Disease and cognitive function 1a – Average test (grey) and conditioned (black) motor evoked potential (MEP) from a representative patient with PD at modified H&Y (modified Hoehn and Yahr) stage 1 (early stage) showing the expected reduction in MEP amplitude when conditioned with median nerve stimulation. 1b - Average test (grey) and conditioned (black) MEP from a representative patient at H&Y stage 3 (advanced stage) showing no change in MEP amplitude when conditioned with median nerve stimulation. ISI = Interstimulus interval. 1c – Gradual mean reduction in percentage inhibition of test MEP with advancement in the disease stage (One way ANOVA with post-hoc Tukey’s test). 1d – A significant negative correlation between SAI and the orientation cognitive domain (Spearman’s rank correlation). 1e - A significant negative correlation between SAI and visuospatial executive function (Spearman’s rank correlation). P < 0.05 was considered the threshold to reject the null hypothesis. N = sample size