Determining the Nature of Prefrontal Cortex Recruitment After Traumatic Brain Injury: A Response to Turner

Abstract

Summary: multIple roleS for prefrontal cortex after Injury The goal remains to determine what pre-frontal recruitment represents after injury, and while I have been critical of this work by Turner et al. (2011), it is clear that gain-ing traction on this issue is not simple. When considering this literature broadly, part of the difficulty may be attributable to the potentially distinct response to injury occurring across functionally discrete nodes within prefrontal cortex. Ultimately, we anticipate that at least part of what has been observed as prefrontal recruitment in TBI represents the unmasking of latent resources during periods of inefficient task processing. This does not, however, preclude the possibility that subcomponents within prefrontal cortex operate to facilitate per-formance under certain conditions or at certain thresholds.In this sense, the role of prefrontal cortex recruitment in working memory is multifaceted and there is unlikely to be uniform dedication of the same resources throughout the life of a task. For exam-ple, in studying TBI, reductions in right prefrontal connectivity can be observed from “early” to “late” in a task as learning occurs (see Hillary et al., 2011). Moreover, the relationship between activation and performance may depend upon how per-formance is measured. One might imagine a scenario where resources are necessary and sufficient for completion of a task (i.e., accuracy), but involvement of these same resources does not also guaran-tee rapid and efficient responding (i.e., reaction time). Thus, to determine the potentially divergent roles of prefrontal cortex recruitment on task performance after TBI, several nuanced manipulations will be required in combination. Future research should focus on within-subject and within-task changes in the neural and behavioral responses, connectivity analy-ses to examine prefrontal communication with other network regions (such as those offered in Turner et al., 2011 here), and lon-gitudinal designs to observe the evolution of prefrontal involvement during critical windows of recovery.based upon incomplete information thus limiting how these findings might inform us more generally about how prefrontal cortex accommodates injury.