Silvia A. Bunge, Itamar Kahn, Jonathan D. Wallis, Earl K. Miller, Anthony D. Wagner, Neural Circuits Subserving the Retrieval and Maintenance of Abstract Rules, Journal of Neurophysiology, 2003, 90, pp. 3419-3428.
Thesis 1: Ventrolateral PFC (VLPFC) is correlated with controlled retrieval and maintenance of abstract rule representations.
Thesis 2: Temporal cortex is correlated with an abstract rule retrieval.
Thesis 3: Left anterior and posterior VLPFC interact with temporal cortices to retrieve the rule, FPC reformulates the rule into a form that can be used to guide behaviour more specifically, and posterior VLPFC and parietal cortices interact to maintain the relevant response contingencies.
(b) Experimental setting:
Experiment: First, subjects learned to associate each of four verbal and nonverbal cues with one of four rules: match, non-match, go left or go right. Non of the cues had preexperimental associations (verbal cues were pronounceable nonwords, e.g. ‘pohu’, and the nonverbal cues were unfamiliar shapes). Then, participants were asked to perform a task while being fMRI scanned. During the task, a cue was presented for 1 s, followed by a variable delay (ranging from 7 s to 15 s). After the delay, a picture was presented (the sample) and was followed by a second picture (the probe) that was either identical to or different from the sample. Two white circles apperead below the second picture, indicating that the participant should make a response by pressing one of two buttons with their left hand. On match trials, subjects were to press the left button if the probe matched the sample and the right button if it did not match. On non-match trials, subjects were to press the left button if the probe did not match the sample and the right button if it matched. On go trials, subjects were to press either left or right button depending on the cue. The fMRI scanning revealed that left VLPFC, parietal, temporal, and posterior dorsolateral (DLPFC) regions were active during cue period. Left posterior VLPFC and parietal regions were active during both cue period and delay period.
2. Critical comments:
1) The rules which were applied by participants, appeared to them as a response to a certain stimuli, verbal or nonverbal, which was associated with this stimuli. The participants did not enter any explicit process of reasoning, which, at least in some contexts, seems to be crucial in applying abstract rules in novel cirtumstances.
2) The rules used by participants in the experiment could be described as technical (match, non match, go left, go right). It would be interesting to see, whether different kinds of rules, especially moral norms, activate the same regions in the brain.