Fig. 3.

Aging effects on task-related TMS measures: (A) Corticospinal excitability modulation (CSE_NORM); (B) M1-M1 IHi modulation (M1-M1 IHi_NORM); and (C) PMd-M1 IHi modulation (PMd-M1 IHi_NORM). The orange bars and green bars represent modulation during the preparatory period $\left({\text{TMS}}_{\text{NORM}(\text{prep})}=\frac{{\text{TMS}}_{\text{IS}}}{{\text{TMS}}_{\text{WS}}}\right)$ and premotor period $\left({\text{TMS}}_{\text{NORM}(\text{prem})}=\frac{\text{TM}{\text{S}}_{75\%\text{EMG}}}{\text{TM}{\text{S}}_{\text{IS}}}\right)$, respectively. For the preparatory period, results are presented for each target hemisphere and type of IHi (B, C). For the premotor period, an additional distinction is made between hand actions. Note that for M1-M1 IHi_NORM(prem), data are collapsed for the factor TARGET HEMISPHERE, since there were no significant (interaction) effects with/of this factor. Note that for the PMd-M1 IHi_NORM(prem), the data are collapsed for the factor HAND ACTION, since there were no significant (interaction) effects with/of this factor. Values below the dashed line indicate an inhibitory modulation relative to TMS_WS (for modulation during the preparatory period) or TMS_IS (for modulation during the premotor period), whereas values above the dashed line indicate a relative facilitatory/disinhibitory modulation. Error bars represent 95% CIs. Abbreviations: D, Dominant; ND, Non-Dominant; O, Older, Y, Young; PMd; dorsal premotor cortex; M1; primary motor cortex; IHi, interhemispheric interaction; s-IHi, short latency interhemispheric interaction; l-IHi, long latency interhemispheric interaction.