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

The Word Memory Test (WMT) is an established symptom validity test that relies on verbal memory performance to make inferences
about “effort.” Previous studies, using a functional MRI (fMRI) adaptation of the WMT with healthy controls, have shown that
successful completion of the WMT relies on a widespread network of neural systems associated with high cognitive effort. Additional
studies using the same fMRI paradigm with patients with severe traumatic brain injury (TBI) suggest that increased activation
of cortical regions associated with cognitive load are recruited to meet the cognitive challenges that the WMT places on a
compromised neural system. This study builds on previous findings as a result of highly uncommon circumstances in which fMRI
data on the WMT task were made available from the very same individual both 1 year before and 1 year after sustaining a TBI.
Interestingly, the effect of TBI did not appear to impair performance on the WMT in terms of standard accuracy measurements,
though response times were notably slower. The main fMRI finding was a significantly stronger and more widespread pattern
of activation post-injury, particularly in the frontal and parietal brain regions, suggesting that stronger engagement of
these networks was necessary to sustain accurate WMT performance compared to pre-injury testing. This unique source of data,
together with previous findings, suggests a more complex relationship between effort and performance levels on the WMT than
what is commonly assumed.