Program No. 831.07. Neuroscience 2014 Abstracts. Washington, DC: Society for Neuroscience, 2014.
Locomotor Sequence Learning in Visually Guided Walking
Julia T Choi 1,2, Peter Jensen 2,, and Jens Bo Nielsen 2
1University of Massachusetts, Amherst, MA USA; 2University of Copenhagen, Denmark
We tested whether spatial sequence learning can be integrated with a highly automatic task like walking. Based on the serial reaction response task, introduced by Nissen and Bullemer (1987), we developed a visuo-locomotor task where subjects controlled step length to hit visual targets displayed on a monitor while walking on a treadmill (Fig 1a). Subject performed a total of 7 blocks that each consisted of 100 steps (Fig 1b), without explicit knowledge of the sequence. In random blocks, the targets appeared randomly at locations that required different step lengths (i.e., short, normal, long). In sequence blocks, subjects were presented with a repeating sequence (i.e., short-long-normal-long-short-normal). The first random block (R1) was used to familiarize the subject to the task. The second random block (R2) provided a measure of final baseline performance. In subsequent training blocks (S1-3), subjects were presented with a repeating sequence. The last random block (R3) was used to measure overall improvement achieved. None of the subjects gave accurate descriptions of the repeating sequence when asked at the end of the experiment. Implicit sequence-specific learning was calculated as the difference in performance between the last training block (S3) and the last random block (R3); non-specific learning was calculated as the difference between blocks R2 and R3. We tested 6 healthy control subjects walking at 2.3 ± 0.2 km/h. Group averaged number of hits increased over the three training blocks, but decreased again in the last random block (*P < 0.05). Performance changes were also measured using endpoint error. We analyzed step frequency, and found that cadence was maintained across 7 blocks of testing. The difference in performance on re-introduction of the random sequence indicates sequence-specific effects rather than non-specific effects. In other words, subjects used knowledge about the step length sequence to plan and execute the movement (rather than simply reacting to the visual stimuli). The results suggest that step-by-step gait modifications can be optimized through visuo-locomotor training.
