Abstract
Previous studies have revealed a specific role of the prefrontal-parietal network in rapid goal-directed chunking (RGDC), which dissociates prefrontal activity related to chunking from parietal working memory demands. However, it remains unknown how the prefrontal and parietal cortices collaborate to accomplish RGDC. To this end, a novel experimental design was used that presented Chinese characters in a chunking task, testing eighteen undergraduate students (9 females, mean age = 22.4 years) while recoding the electroencephalogram (EEG). In the experiment, radical-level chunking was accomplished in a timely stringent way (RT = 1485 ms, SD = 371 ms), whereas the stroke-level chunking was accomplished less coherently (RT = 3278 ms, SD = 1083 ms). By comparing the differences between radical-level chunking vs. stroke-level chunking, we were able to dissociate the chunking processes in the radical-level chunking condition within the analyzed time window (−200 to 1300 ms). The chunking processes resulted in an early increase of gamma band synchronization over parietal and occipital cortices, followed by enhanced power in the beta-gamma band (25–38 Hz) over frontal areas. We suggest that the posterior rhythmic activities in the gamma band may underlie the processes that are directly associated with perceptual manipulations of chunking, while the subsequent beta-gamma activation over frontal areas appears to reflect a post-evaluation process such as reinforcement of the selected rules over alternative solutions, which may be an important characteristic of goal-directed chunking.
Highlights
Chunking, which refers to the integration of distinct pieces of information into a single unit, plays an important role in human memory, learning, and problem solving (Chase and Simon, 1973; Gobet et al, 2001)
The accuracy rate of the radical and stroke chunking conditions was 99% (SD = 1%) and 84% (SD = 11%), respectively, revealing a statistically significant difference [t(17) = −6.00, p < 0.001, paired t-test]. This demonstrates that participants were more accurate in combining radicals than strokes with the respective character parts
Since we are interested in the neural correlates of chunking, the radical chunking condition is ideal for the current analyses due to its consistency in accuracy (SD = 0.01) and in reaction times (RTs) (SD = 371), while, the stroke chunking condition serves as an ideal control with no chunking occurring within the to-be-analyzed time window
Summary
Chunking, which refers to the integration of distinct pieces of information into a single unit, plays an important role in human memory, learning, and problem solving (Chase and Simon, 1973; Gobet et al, 2001). Bor et al (2003) and Bor and Owen (2006) have demonstrated that intentionally chunking separated dots into familiar objects activated the prefrontal parietal network In their spatial working memory task, participants had to maintain a dot trajectory within a 4 × 4 square space. Structured sequences, encouraging reorganization of these trajectories into coherent chunks like, for example letters, showed increased activation in prefrontal cortex and in the inferior parietal lobule during encoding, while unstructured trials (without chunking) showed increased activation in parietal and premotor cortices during the delay This shows a successful dissociation of chunking from the maintenance of information in the frontal cortex, it remains unknown how the prefrontal cortex interacts with the parietal lobule during chunking, and the temporal characteristics of the cognitive processes underlying RGDC
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