Eric W. Gobel, Paul J. Reber; Northwestern University
Society for Neuroscience Annual Meeting 2009, Chicago, IL. 21 Oct 2009.
Most well practiced perceptual-motor skills that we execute are composed of a learned sequence of movements that must be performed in a particular order with specific timing. Experiments described here support the idea that order and timing are interdependent and integrated in perceptual-motor sequence learning. Furthermore, there are distinct regions of the brain that process the separate order and timing components and their integration.
To study the neural underpinnings of order and timing in implicit perceptual-motor sequence learning, a new paradigm was developed emphasizing precise timing in the response to a moving visual cue and allowing for timing information to be embedded in the response sequence. In this paradigm, circular cues move upwards on the screen toward four target regions. Participants are instructed to press a corresponding key when a cue is centered within the target region. In a behavioral experiment, participants learned a repeating 12-item sequence of responses with embedded timing information: responses were separated by either 350ms or 700ms in a repeating pattern. Overall performance on the task improved over time, as measured by decreasing error rates. When a novel pseudo-random series of responses was required instead of the repeating sequence, the error rate increased significantly, showing that participants had acquired implicit knowledge of the specific practiced sequence.
After learning, participants performed four transfer conditions, which maintained either the ordinal sequence, the timing sequence, both sequences, or neither sequence. Participants exhibited high levels of performance only when the test sequence was identical to the training conditions, maintaining both the order and inter-item timing. When either the order of actions or the timing intervals between actions was changed, participants’ performance dropped to a level equivalent to that of a completely novel sequence. These results demonstrate that timing information is tightly integrated with order information in a learned perceptual-motor sequence.
Functional imaging of the transfer conditions was performed to identify the brain circuits mediating performance of the order and timing integration components of the practiced sequence. Results suggest that cerebellar and anterior precuneus activity is correlated with executing an integrated order and timing sequence, while posterior precuneus and anterior cingulate activity is correlated with executing a practiced order of movements, independent of timing.