Table 1.
Study | Animal model | Cortical Stimulation Parameters | Rehabilitation Training | Behavioral Outcomes | Neuroanatomical/Neurophysiological Outcomes |
---|---|---|---|---|---|
Kleim et al., 2003 | Rodent Compared monopolar cathodal, bipolar cathodal, monopolar anodal, and no CS |
Subdural 50Hz 1 sec pulse | Single pellet reaching task 20minutes/day for 10 days | Both monopolar and bipolar CS enhanced motor recover – monopolar stimulation more effective | Both monopolar and bipolar CS increased area of cortex from which microstimulation movements could be evoked |
Teskey et al., 2003 | Rodent Compared frequencies (0, 25, 50, 100, 250, and 500 Hz) |
Subdural 0,25,50, 100, 250, 500 Hz 3 sec pulse 50% MT | Pasta Matrix Task 20 minutes/day for 10 days | CS with frequencies between 50 and 250 Hz more effective Returned to preinfarct training levels for reaching success. |
Enhanced evoked potentials and lowering of the MT (25Hz and above) Larger polysynaptic potentiation between 50 and 500 Hz. |
Adkins- Muir & Jones, 2003 | Rodent Compared frequencies (50Hz, 250 Hz, and no CS) |
Subdural 50Hz, 250 Hz no CS 3 sec pulse 50–70% MT | Montoya staircase – retrieved food pellets placed at variable distances on a “staircase” 20 minutes/day for 10 days | No sig. difference in reaching between 250 Hz and no CS. 50 Hz group had significantly greater rate of improvement in reaching | 50 Hz significant increase in surface density of dendritic processes in perilesion cortex compared to other two groups |
Plautz et al., 2003 Plautz & Nudo (2005) |
Nonhuman Primate Assessed feasibility of CS/RT in primates |
Subdural 50 Hz 50% MT 1 sec continuous stimulation – unlimited duration pulse train Monopolar Modified stimulus parameters – monopolar cathodal 100 μsec duration 100 Hz 50% MT |
Unimanual pellet retrieval task requiring skilled use of hand – progressed through training stages in which gradual decrease in the diameter of the wells required increasing finger dexterity. Two 35 minute sessions per day for 30 days. CS initiated 5 minutes before RT. |
Sig improvement in motor performance (success, speed, efficiency) of pellet retrieval which persisted for at least 4 months. Substantial but incomplete resolution of chronic motor performance deficits. Peak recovery level (% recovery to preinfarct level) was 88% for CS/RT and 43% for RT alone |
Large scale emergence of new hand representations in peri-infarct motor cortex, notably in cortical tissue underlying the electrode |
Adkins et al., 2006 | Rodent Compared anodal versus cathodal stimulation |
Epidural 100Hz monopolar stimulation 50% MT | Single pellet retrieval task 60 trials per day or 15 minutes whichever occurred first for 18 days | Demonstrated efficacy of epidural CS/RT Both anodal and cathodal CS enhanced reaching performance compared to no CS group | Cathodal CS/RT group showed increased neuronal density in perilesion cortex |
Adkins et al., 2008 | Rodent Compared effect of CS/RT on rats with moderate versus severe retrieval deficits |
Epidural 100Hz monopolar cathodal stimulation 40–50% MT | Single pellet retrieval task 60 trials per day or 15 minutes whichever occurred first for 18 days | CS/RT enhanced recovery of reaching success in the moderately but not severely impaired subgroups. | Both CS/RT groups had increased density of axodendritic synapses compared to no CS and there was a positive correlation between post rehab reaching success and synaptic density. |
Boychuk et al., 2011 | Rodent Compared focal versus distributed CS |
Epidural monopolar 1-second, 50- Hz cathodal pulse 50% motor threshold | Single pellet skilled reaching task 15 minutes/day for 12 consecutive days | Only the distributed CS/RT enhanced motor performance with RT. | Both the focal and distributed CS/RT promoted motor map reorganization |
CS = cortical stimulation; RT = rehabilitation training; MT = motor threshold