Functional Neuroimaging of Symptom Validity Testing in Traumatic Brain Injury

Abstract

The Word Memory Test (WMT) is a commonly used symptom validity test (SVT) that assesses recognition verbal memory. The task has been adapted for use within a functional magnetic resonance imaging (fMRI) paradigm so the neural correlates of WMT activation patterns can be studied. In the current investigation, performance on the delayed recognition subtest of the WMT was examined in two patients who sustained severe TBI and compared to ten healthy controls. The patients underwent comprehensive neuropsychological evaluations and structural MRI. All participants completed two versions of the WMT: full-effort and simulated poor effort conditions. Despite extensive structural brain damage, the fMRI activation patterns during full-effort WMT performance were somewhat similar in the two TBI patients and likewise, somewhat similar to controls. The fMRI activation pattern in both patients demonstrated intact activation of the basic neural structures necessary to perform the WMT. Dissimilar patterns of activation were obtained during the simulated poor effort condition of WMT performance suggesting that fMRI techniques may be sensitive in demonstrating non-credible cognitive performance. The results of our study represent the first fMRI investigation of normal and simulated poor effort SVT performance in individuals with documented brain damage. The implications of fMRI techniques in SVT research and their clinical application are discussed.

Traumatic Brain Injury Alters Word Memory Test Performance by Slowing Response Time and Increasing Cortical Activation: An fMRI Study of a Symptom Validity Test

“…Significant regions of activation observed both in pre-and post-injury exams were generally consistent for what has previously been observed both at the group level (Allen et al 2007;Larsen et al 2010) and at the individual level (Wu et al 2010). Significant regions of activation included the ventral visual processing stream, motor cortex, and frontalparietal attentional systems (see Table 1 and Fig.…”

“…While the findings of Wu et al (2010) suggest that patients with severe TBI might rely on atypical brain systems in order to meet the cognitive demands required of the WMT, patients with mild TBI might be expected to show a different pattern. Based on results of previous fMRI studies using working memory and other cognitively demanding testing paradigms (McAllister et al 2001(McAllister et al , 2006, we might instead expect increased activation of the systems typically associated with WMT performance, particularly in prefrontal and parietal cortices.…”

“…These studies demonstrated that WMT performance relies on an extended network involving long neural tracts that engage memory and attentional systems throughout the brain but left open the question of how damage to these networks would affect WMT performance. However, in a novel fMRI study of the WMT, Wu et al (2010) demonstrated that two severe TBI patients who performed above cut-score levels on the WMT showed two divergent patterns of activation. Because patient activation patterns differed both from one another and from controls, these results suggest that brain injury had altered the basic cognitive network for normal WMT performance in these patients, who instead relied on adaptive and/or compensatory systems to perform well.…”

It's Not All in Your Head (or at Least Your Brain): Association of Traumatic Brain Lesion Presence and Location with Performance on Measures of Response Bias in Forensic Evaluation

“…While the study sample of 92 patients is larger than those of earlier studies examining the relationship between PVT and neuroimaging results (e.g., Wu, Allen, Goodrich‐Hunsaker, Hopkins, & Bigler, ), it is still comparatively small. Thus, additional studies will need to document further the lack of association between brain lesion and measures of response bias.…”

“…The results of the current study build upon previous research examining the relationship, if any, between the presence of lesion localization in a brain injury litigant and PVTs. To date, only a few case studies (Goodrich‐Hunsaker & Hopkins, ; Palmer, Boone, Allman, & Castro, ; Wu, Allen, Goodrich‐Hunsaker, Hopkins, & Bigler, ) have examined the relationship of brain injury and performance on PVTs, but due to small sample sizes, results generated would greatly under‐represent any significant findings. The authors of these studies found that patients with brain damage were able to pass measures capturing response bias.…”