Dissociable brain states linked to common and creative object use

Abstract

Studies of conceptual processing have revealed that the prefrontal cortex is implicated in close-ended, deliberate memory retrieval, especially the left ventrolateral prefrontal regions. However, much of human thought-particularly that which is characterized as creative-requires more open-ended, spontaneous memory retrieval. To explore the neural systems that support conceptual processing under these two distinct circumstances, we obtained functional magnetic resonance images from 24 participants either while retrieving the common use of an everyday object (e.g., "blowing your nose," in response to a picture of a tissue) or while generating a creative (i.e., uncommon but plausible) use for it (e.g., "protective padding in a package"). The patterns of activation during open- and closed-ended tasks were reliably different, with regard to the magnitude of anterior versus posterior activation. Specifically, the close-ended task (i.e., Common Use task) reliably activated regions of lateral prefrontal cortex, whereas the open-ended task (i.e., Uncommon Use task) reliably activated regions of occipito-temporal cortex. Furthermore, there was variability across subjects in the types of responses produced on the open-ended task that was associated with the magnitude of activation in the middle occipital gyrus on this task. The present experiment is the first to demonstrate a dynamic tradeoff between anterior frontal and posterior occipitotemporal regions brought about by the close- or open-ended task demands.

Figure 1

(A) Example trials and their duration. Participants in the first condition (n = 12) generated aloud the common use for each object; participants in the second condition (n = 12) generated aloud an uncommon use for each object; both participant groups also performed a baseline task in which they verified aloud whether a square box was superimposed on top of abstract black and white images; ms = milliseconds; ITI = intertrial interval. The events were jittered with the inclusion of additional null trials, which extended the ISI from 3,000 ms to either 6,000, 9,000, or 12,000 ms. (B) Results of the random effects analysis for the Common Use task relative to the perceptual baseline; (C) Results of the random effects analysis for the Uncommon Use task relative to the perceptual baseline; L = left hemisphere, R = right hemisphere.

Figure 2

(A) Results of the random effects analysis for both experimental tasks relative to the perceptual baseline; this analysis was used for the identification of functional regions of interest (ROIs). (B) Mean blood oxygenation level–dependent (BOLD) signal change (beta value) by task (Common Use vs. Uncommon Use) and posterior and anterior ROIs of maximum activation (P < 0.04). Error bars indicate the standard error of the means. L = left hemisphere, R = right hemisphere.

Figure 3

(A) Identification of ROIs by labels, Talairach coordinates (x y z) and t value (critical threshold t = 5.53, P < 0.05) and mean signal change by 27‐voxel region of interest (ROI) and task. †Because of the proximity of the local maxima to the edge of the image, the ROI did not extend fully in all directions and so contains fewer than 27 voxels (min = 14). (B) Identification of ROIs by position.

Figure 4

Relationship between signal change in the left middle occipital gyrus and percent of perceptually based responses for the Uncommon Use task on the qualitative analysis measure (Pearson's r = 0.54, P = 0.06; for median scores, Pearson's r = 0.65, P = 0.02).