Practice Induces Function-Specific Changes in Brain Activity

Practice can have a profound effect on performance and brain activity, especially if a task can be automated. Tasks that allow for automatization typically involve repeated encoding of information that is paired with a constant response. Much remains unknown about the effects of practice on encoding and response selection in an automated task.To investigate function-specific effects of automatization we employed a variant of a Sternberg task with optimized separation of activity associated with encoding and response selection by means of m-sequences. This optimized randomized event-related design allows for model free measurement of BOLD signals over the course of practice. Brain activity was measured at six consecutive runs of practice and compared to brain activity in a novel task.Prompt reductions were found in the entire cortical network involved in encoding after a single run of practice. Changes in the network associated with response selection were less robust and were present only after the third run of practice.This study shows that automatization causes heterogeneous decreases in brain activity across functional regions that do not strictly track performance improvement. This suggests that cognitive performance is supported by a dynamic allocation of multiple resources in a distributed network. Our findings may bear importance in understanding the role of automatization in complex cognitive performance, as increased encoding efficiency in early stages of practice possibly increases the capacity to otherwise interfering information

Response Selection ROI's.

<p>ROIs showing activity related to the response selection. The numbers in the color bar refer to the response selection ROIs (RS1–RS14) in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003270#pone-0003270-t003" target="_blank">table 3</a>.</p

Heterogeneous effect of practice on regions activated by both encoding and response selection.

<p>Example of bold activity (arbitrary units) in regions activated by both phases: a. left DLPFC (top) and b. anterior cingulate cortex (bottom) during the novel task (left), after one practice run (middle) and six practice runs (right); showing the heterogeneous effects of practice for encoding and response selection.</p

Practice and Encoding Activity

<p>Multivariate tests for signals in ROIs related to encoding. Signals were tested over all runs (1st column) and between novel task (NT) and each practice run (PT). Significant results are displayed in bold. (For abbreviations see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003270#pone-0003270-t002" target="_blank">table 2</a>).</p

Encoding ROI's

<p>Description of ROIs showing activity correlated with encoding phase. (Abbreviations: E = encoding; BA = Brodmann Area; NV = number of voxels in ROI (size of ROI); x, y, z = MNI coordinates of voxel with highest t-value in ROI; tmax: maximum t-value in ROI).</p

Cognitive Paradigm.

<p>The timeline is shown for the cognitive experiment. Two m-sequences (m.seq.) of 63 bits control the encoding phase (1) and the response phase (2). Each trial starts with the encoding phase followed by a brief delay and the response phase. Where bits are 0 (baseline); memory sets with 1 letter (MS1) are presented during the encoding phase and blank trials are presented during the response phase. Where bits are 1; 5-letter memory sets (MS5) are presented during the encoding phase and a probe stimulus during the response phase. In the novel task the letters presented during the encoding phase were different in each MS1 and MS5 trial. In the practiced task, the same five letters were repeated in each MS5 trial.</p

Practice and Performance

<p>a. reaction time (top) and b. error rate (bottom). Measures were tested over all runs (1st row) and between novel task (NT) and each practice run (PT), across one-letter (MS1) and five-letter (MS5) memory set trials (1st column) and for MS1 trials vs. MS5 trials (2nd column). Significant results are displayed in bold.</p

Encoding ROI's.

<p>ROIs showing activity related to encoding. The numbers in the color bar refer to the encoding phase ROIs (E1–E7) in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003270#pone-0003270-t002" target="_blank">table 2</a>.</p

Practice and brain activity.

<p>a. activity in arbitrary units during encoding averaged over encoding phase ROIs (left) and b. activity during response selection averaged over response selection ROIs (right). Activity is displayed for novel task (NT) and each practice run (PT1–PT6).</p