Functional Magnetic Resonance Imaging of Working Memory and Response Inhibition in Children with Mild Traumatic Brain Injury

Abstract

The current pilot study examined functional magnetic resonance imaging (fMRI) activation in children with mild traumatic brain injury (mTBI) during tasks of working memory and inhibitory control, both of which are vulnerable to impairment following mTBI. Thirteen children with symptomatic mTBI and a group of controls completed a version of the Tasks of Executive Control (TEC) during fMRI scanning. Both groups showed greater prefrontal activation in response to increased working memory load. Activation patterns did not differ between groups on the working memory aspects of the task, but children with mTBI showed greater activation in the posterior cerebellum with the addition of a demand for inhibitory control. Children with mTBI showed greater impairment on symptom report and "real world" measures of executive functioning, but not on traditional "paper and pencil" tasks. Likewise, cognitive testing did not correlate significantly with imaging results, whereas increased report of post-concussive symptoms were correlated with increased cerebellar activation. Overall, results provide some evidence for the utility of symptom report as an indicator of recovery and the hypothesis that children with mTBI may experience disrupted neural circuitry during recovery. Limitations of the study included a small sample size, wide age range, and lack of in-scanner accuracy data.

An fMRI Study of Auditory Orienting and Inhibition of Return in Pediatric Mild Traumatic Brain Injury

“…Our current results are consistent with previous findings of hypoactivation during the semi-acute phase of injury (Talavage et al, 2010). In contrast, no difference was observed when data were collected with a heterogeneous time interval spanning the semi-acute to the post-acute phase (Krivitzky et al, 2011), comprising a range in which the majority of patients are expected to recover. These results underscore the important role of homogeneity in time postinjury in examining the neural mechanisms of cognitive disruption, and suggest that the semi-acute phase of injury may be a critical period to characterize the subtle alterations in brain activation following mTBI.…”

“…These results underscore the important role of homogeneity in time postinjury in examining the neural mechanisms of cognitive disruption, and suggest that the semi-acute phase of injury may be a critical period to characterize the subtle alterations in brain activation following mTBI. An additional explanation for the current findings of hypoactivation versus previous findings of hyperactivation (Krivitzky et al, 2011) is that the bottom-up orienting task is likely to be more consistent with a lower cognitive load, which has been shown to result in hypoactivation in adult mTBI patients (McAllister et al, 1999(McAllister et al, ,2001.…”

“…Previous fMRI studies on pediatric mTBI have reported either no difference (Krivitzky et al, 2011), or hypoactivation (Talavage et al, 2010), during a visual n-back working memory task, or hyperactivation during an inhibitory control task (Krivitzky et al, 2011). As noted earlier, a potential explanation for the differences in brain activation patterns across different fMRI studies includes heterogeneity in time post-injury.…”

“…The few fMRI studies examining cognitive function following TBI in children and adolescents have primarily focused on more severely injured patients (Cazalis et al, 2011;Karunanayaka et al, 2007;Kramer et al, 2009Kramer et al, ,2008Newsome et al, 2007Newsome et al, ,2008Tlustos et al, 2011;Wilde et al, 2011), with only two studies focusing on a well-defined mTBI population (Krivitzky et al, 2011;Talavage et al, 2010). Krivitzky and colleagues (2011) reported no difference in brain activation between children with mTBI and healthy controls (HCs) on a working memory task, but they found hyperactivation in mTBI patients in the posterior cerebellum with the addition of a demand for inhibitory control processes.…”

“…The two fMRI studies on pediatric mTBI were conducted either within the semi-acute phase (Talavage et al, 2010), or with a heterogeneous time interval spanning from 8 to 82 days (Krivitzky et al, 2011), comprising a range in which the majority of patients are expected to recover. As significant individual variation in the time course of recovery exists within the mTBI group (Kirkwood et al, 2008;Lovell et al, 2007;Yeates et al, 2009), this clinical heterogeneity makes uncovering the specific pathology quite difficult and may contribute to the inconsistent results seen in the literature.…”