The effects of practice on the functional anatomy of task performance

Abstract

The effects of practice on the functional anatomy observed in two different tasks, a verbal and a motor task, are reviewed in this paper. In the first, people practiced a verbal production task, generating an appropriate verb in response to a visually presented noun. Both practiced and unpracticed conditions utilized common regions such as visual and motor cortex. However, there was a set of regions that was affected by practice. Practice produced a shift in activity from left frontal, anterior cingulate, and right cerebellar hemisphere to activity in Sylvian-insular cortex. Similar changes were also observed in the second task, a task in a very different domain, namely the tracing of a maze. Some areas were significantly more activated during initial unskilled performance (right premotor and parietal cortex and left cerebellar hemisphere); a different region (medial frontal cortex, "supplementary motor area") showed greater activity during skilled performance conditions. Activations were also found in regions that most likely control movement execution irrespective of skill level (e.g., primary motor cortex was related to velocity of movement). One way of interpreting these results is in a "scaffolding-storage" framework. For unskilled, effortful performance, a scaffolding set of regions is used to cope with novel task demands. Following practice, a different set of regions is used, possibly representing storage of particular associations or capabilities that allow for skilled performance. The specific regions used for scaffolding and storage appear to be task dependent.

Figure 1

Absolute magnitudes in hypothetical brain areas (Top three graphs) during passively viewing words, reading words, and generating verbs; difference magnitudes in hypothetical brain areas (Middle three graphs) for reading minus passively viewing words and verb generation minus reading words subtractions; and difference magnitudes in brain areas of interest (Bottom three graphs) for reading minus passively viewing words and verb generating minus reading words subtractions in areas with activations related to motor output (A–C), to generating a verb (D–F), and to simple reading of words (G–I).

Figure 2

Median reaction times (Left) and percentage of stereotyped responses (Right) across verb generation practice blocks. Means and standard error are presented. g1–g10 represent the 10 verb generate blocks, all on the same list of 40 nouns, g1′ is verb generate on a novel list of nouns. Subjects were scanned during g1 (naive verb generate), g10 (practiced verb generate), and g1′ (novel verb generate).

Figure 3

PET difference (subtraction) images showing areas of increased (Upper images) and decreased (Lower images) blood flow when verb generation (under Naive, Practiced, and Novel conditions) is compared with reading. During naive (Left images) and novel (Right images) verb generation, increased blood flow in left frontal cortex was found compared with simple reading, whereas decreased blood flow was observed in left insular cortex. The Center images show that blood flow in these areas changed to a level almost identical to that found during simple reading after the verb generation was practiced. A linear gray scale is used with white representing maximal activation and black, minimal activation. The brain outlines were traced from the stereotaxic atlas of Talairach and Tournoux (20) and represent sagittal sections with their x-axis (left–right axis, left being negative) positions in millimeters noted.

Figure 4

Magnitudes in left prefrontal cortex, anterior cingulate, right cerebellum, and bilateral insular cortex for the verb generation conditions (naive, practiced, and novel) minus word reading.

Figure 5

Maze and square designs used in the study. Arrows indicate the starting position for the tracing of each design. Shown are the mazes presented during right-hand performance. During left-hand performance, mirror images of the mazes were presented and tracing had to be done in a counterclockwise direction. Starting position for left-hand square tracing was at the lower right corner, with counterclockwise tracing.

Figure 6

Mean velocity, number of errors, and duration and percentage of stops for right- and left-hand performance as a function of condition.

Figure 7

PET difference (subtraction) images showing areas of increased (Upper images) and decreased (Lower images) blood flow when maze tracing (under Naive, Practiced, and Novel conditions) is compared with fast square tracing. During naive (Left images) and novel (Right images) maze tracing, increased blood flow in right premotor and parietal areas was found compared with square tracing, whereas decreased blood flow was observed in primary and supplementary motor cortex. The Center images show that blood flow in these areas changed to a level almost identical to that found during simple square tracing after the maze was practiced. A linear gray scale is used, with white representing maximal activation and black, minimal activation. The brain outlines were traced from the stereotaxic atlas of Talairach and Tournoux (20) and represent a transverse section 54 mm above the AC–PC line.

Figure 8

Magnitudes in right premotor and parietal areas, left cerebellum, SMA, and left primary motor cortex for the maze-tracing conditions (Naive, Practiced, and Novel) minus fast square tracing.

Figure 9

Absolute magnitudes in hypothetical brain areas (Upper three graphs) during the five tracing conditions minus the control rest condition and in brain areas of interest (Lower three graphs) in areas with activations related to velocity (A and B), to unskilled performance (C and D), and to skilled performance (E and F).