Lateralized readiness potentials can identify hemisphere of recovery in stroke patients.

Highlights• In healthy adults, the lateralized readiness potential (LRP) is localized to the hemisphere contralateral to a moving limb.• In stroke, the LRP can lateralize contra-, or ipsilateral to the paretic limb depending on the stage of recovery.• Identification of hemisphere of recovery can guide further measures for enhancing brain plasticity. BACKGROUND Event related cortical potentials related to motor action are referred to as movement related cortical potentials. The late component of which is the readiness potential (RP) and its polarity is more negative in the hemisphere responsible for planning of motor action. This lateralized nature of RP during unilateral hand movement is studied as lateralized readiness potential (LRP) by calculating the contralateral-minus-ipsilateral difference wave for each hand. OBJECTIVE The aim was to identify the hemisphere contributing to motor recovery in acute and chronic stroke patients through recording LRPs. METHODS Twenty-nine cases with cerebrovascular stroke (15 acute and 14 chronic) were included in the study. EEG was recorded in response to self-cued button presses by the paretic side to obtain the averaged LRP amplitude. The hemisphere with greater negativity was considered the side of recovery. Functional recovery was assessed by Fugl Meyer test. RESULTS In acute cases, recovery was more related to LRP activity in the contralesional hemisphere (73% ), whereas lateralization was equal in chronic cases; 50% in either group. LRP amplitude was higher in the contralesional hemisphere (p = 0.02). Functional recovery assessed by the Fugl Meyer test (FM) was similar whether recovery was ipsi- or contralesional. CONCLUSIONS Early after stroke, motor recovery is more likely to involve compensatory activity in the contralesional hemisphere, while in the chronic phase, the ipsilesional hemisphere may recover its function and become more active. Further research is needed to verify if the technique mentioned in our study could be used to guide customized NIBS protocols tailoring the optimal site and parameters for each patient.