Motor imagery training induces changes in brain neural networks in stroke patients

Abstract

Motor imagery is the mental representation of an action without overt movement or muscle activation. However, the effects of motor imagery on stroke-induced hand dysfunction and brain neural networks are still unknown. We conducted a randomized controlled trial in the China Rehabilitation Research Center. Twenty stroke patients, including 13 males and 7 females, 32-51 years old, were recruited and randomly assigned to the traditional rehabilitation treatment group (PP group, n = 10) or the motor imagery training combined with traditional rehabilitation treatment group (MP group, n = 10). All patients received rehabilitation training once a day, 45 minutes per session, five times per week, for 4 consecutive weeks. In the MP group, motor imagery training was performed for 45 minutes after traditional rehabilitation training, daily. Action Research Arm Test and the Fugl-Meyer Assessment of the upper extremity were used to evaluate hand functions before and after treatment. Transcranial magnetic stimulation was used to analyze motor evoked potentials in the affected extremity. Diffusion tensor imaging was used to assess changes in brain neural networks. Compared with the PP group, the MP group showed better recovery of hand function, higher amplitude of the motor evoked potential in the abductor pollicis brevis, greater fractional anisotropy of the right dorsal pathway, and an increase in the fractional anisotropy of the bilateral dorsal pathway. Our findings indicate that 4 weeks of motor imagery training combined with traditional rehabilitation treatment improves hand function in stroke patients by enhancing the dorsal pathway. This trial has been registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-OCH-12002238).

Keywords: brain neural network; diffusion tensor imaging; dorsal pathway; hand function; motion evoked potential; motor imagery; nerve regeneration; neural regeneration; stroke; ventral pathway.

Figure 1

Effect of motor imagery training combined with traditional rehabilitation on hand function in stroke patients. (A) ARAT score. (B) FMA score. Difference = post-training − pre-training. Data are expressed as the mean ± SD (n = 20; independent sample t-test). ##P < 0.01, vs. pre-training; *P < 0.05, **P < 0.01, vs. PP group. MP: Motor imagery training combined with traditional rehabilitation treatment group; PP: traditional rehabilitation treatment group; ARAT: Action Research Arm Test; FMA: Fugl–Meyer Assessment of the upper extremity.

Figure 2

Effect of motor imagery training combined with traditional rehabilitation treatment on MEPs in the abductor pollicis brevis in stroke patients. (A) MEP amplitude. (B) MEP latency. Data are expressed as the mean ± SD (n = 20; independent sample t-test). ##P < 0.01, vs. pre-training; *P < 0.05, vs. PP group. MP: Motor imagery training combined with traditional rehabilitation treatment group; PP: traditional rehabilitation treatment group; MEP: motor evoked potential.

Figure 3

Left/right and dorsal/ventral pathway tracked by the fiber probability tracking method. (A) Green indicates the right dorsal pathway; (B) green indicates the left dorsal pathway; (C) blue indicates the right ventral pathway; (D) blue indicates the left ventral pathway.