Neural correlates of fluid reasoning in children and adults

Abstract

Fluid reasoning, or the capacity to think logically and solve novel problems, is central to the development of human cognition, but little is known about the underlying neural changes. During the acquisition of event-related fMRI data, children aged 6-13 (N = 16) and young adults (N = 17) performed a task in which they were asked to identify semantic relationships between drawings of common objects. On semantic problems, participants indicated which of five objects was most closely semantically related to a cued object. On analogy problems, participants solved a visual propositional analogy (e.g., shoe is to foot as glove is to...?) by indicating which of four objects would complete the problem; these problems required integration of two semantic relations, or relational integration. Our prior research on analogical reasoning in adults implicated left anterior ventrolateral prefrontal cortex (VLPFC) in the controlled retrieval of individual semantic relationships, and rostrolateral prefrontal cortex (RLPFC) in relational integration. In this study, age-related changes in the recruitment of VLPFC, temporal cortex, and other cortical regions were observed during the retrieval of individual semantic relations. In contrast, age-related changes in RLPFC function were observed during relational integration. Children aged 6-13 engage RLPFC too late in the analogy trials to influence their behavioral responses, suggesting that important changes in RLPFC function take place during adolescence.

Keywords: analogy; brain; cognition; development; frontal; functional magnetic resonance imaging; hierarchy; relational.

Figure 1

A sample problem is displayed for each of the two task conditions. (A) On semantic problems, one must choose from four images the object that is most closely related to the target image. (Correct answer: A; D = perceptual lure). (B) On analogy problems, one must consider the relationship between the two images above, and identify the image below that completes the analogy (Correct answer: C; B = semantic lure).

Figure 2

Behavioral results for performance during fMRI data acquisition are shown here. Proportion of errors and RTs for correctly performed trials are plotted separately for semantic and analogy conditions, and for adult and child groups. Error bars represent the within-subject error of the Condition × Group interactions. Both age groups showed an increase in errors and RTs for analogy compared to semantic trials. However, children made disproportionately more errors on analogy trials than adults.

Figure 3

Whole-brain multiple regression analyses are displayed here. (A) Positive correlations with age from 6-13 were observed for semantic trials (shown in red) in a number of regions, including left RLPFC (BA 10; −27, 50, 0), left VLPFC (BA 45; −42, 18, 16) and right DLPFC (BA 9; −48, 18, 26), and regions in temporal, parietal, motor, and visual regions. For analogy trials, positive correlations with age from 6–13 were observed only in left RLPFC, right VLPFC, and right superior parietal lobule (BA 7; 36, −66, 52). (B) Adults who exhibited higher accuracy on analogy trials exhibited greater differential activation between analogy and semantic trials in bilateral VLPFC and RLPFC, as well as several other regions. The most prominent cluster was observed in right RLPFC (BA 10; 27, 45, 16).

Figure 4

Left VLPFC ROI and timecourse. The left side displays the left VLPFC ROI identified from the positive correlation between semantic > fixation activation and age in children (ROI circled in blue on the rendered image, and shown below on an axial slice). The right side displays the median timecourse of activation for this region. Semantic (blue) and analogy (red) trials are shown separately, for both adult and child groups.

Figure 5

RLPFC ROIs and timecourses. The left side of the image displays a sagittal view of the left RLPFC ROI, and two separate timecourses displaying semantic and analogy activation every two seconds from where it is baselined at 2 seconds until 18 seconds after trial onset. The right side displays the right RLPFC region and timecourses. All timecourses also model the motor cortex ROI. Note that while in adults the RLPFC timecourses peak during the same 4–6-second period as the motor cortex ROI, in children these ROIs peak much later at 10 to 12 seconds after trial onset.