Abstract rule learning: the differential effects of lesions in frontal cortex.
Learning progressively more abstract stimulus-response mappings requires progressively more anterior regions of the lateral frontal cortex. Using an individual differences approach, we studied subjects with frontal lesions performing a hierarchical reinforcement-learning task to investigate how frontal cortex contributes to abstract rule learning. We predicted that subjects with lesions of the left pre-premotor (pre-PMd) cortex, a region implicated in abstract rule learning, would demonstrate impaired acquisition of second-order, as opposed to first-order, rules. We found that 4 subjects with such lesions did indeed demonstrate a second-order rule-learning impairment, but that these subjects nonetheless performed better than subjects with other frontal lesions in a second-order rule condition. This finding resulted from both their restricted exploration of the feature space and the task structure of this condition, for which they identified partially representative first-order rules. Significantly, across all subjects, suboptimal but above-chance performance in this condition correlated with increasing disconnection of left pre-PMd from the putative functional hierarchy, defined by reduced functional connectivity between left pre-PMd and adjacent nodes. These findings support the theory that activity within lateral frontal cortex shapes the search for relevant stimulus-response mappings, while emphasizing that the behavioral correlate of impairments depends critically on task structure.
Department of Neurology, University of California, San Francisco, CA 94143, USA. akayser@gallo.ucsf.edu
Andrew S
AS
Kayser
Mark
M
D'Esposito
D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000503:physiopathology* / Q000601:surgery; D001930:Brain Injuries / Q000503:physiopathology* / Q000601:surgery; D003210:Concept Formation; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007858:Learning; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance / Q000502:physiology*; D014163:Transfer, Psychology