A, representative traces showing each of the four distinct AP discharge patterns exhibited by DDH interneurons in response to a 800 ms square step depolarising current injection: tonic firing (TF), initial bursting (IB), delayed firing (DF) and single spiking (SS). B, group data showing the incidence of each of the four AP discharge patterns in age-matched uninjured control animals for the 3 weeks (light grey bars, n = 44 neurons) and 6 weeks (dark grey bars, n = 39) time points. C, incidence of AP discharge patterns in untrained SCI animals at 3 weeks (light grey bars, n = 49) and 6 weeks (dark grey bars, n = 70) time points. D, incidence of AP discharge patterns in trained SCI animals at 3 weeks (light grey bars, n = 43) and 6 weeks (dark grey bars, n = 66). *P < 0.05 for 3 week untrained group compared to 3 week control group. Significance obtained using χ2 test.