Exaggerated reaction to novelty as a subclinical consequence of mild traumatic brain injury

Objectives: To evaluate exaggerated reaction to novelty as a behavioural marker of sub-clinical cognitive dysfunction in individuals with a history of mild traumatic brain injury (mTBI).

Background and hypothesis: A sub-set of individuals who sustain mTBIs report persistent cognitive difficulties despite normal performance on traditional neuropsychological measures. Evidence of subtle neuroimaging abnormalities following mTBI lends support to such subjective complaints. However, behavioural evidence is limited. This study examined whether behavioural response to task novelty ('novelty effect' or NE) is exaggerated in mTBI (NE has previously successfully identified pre-clinical cognitive decline among older adults). It was hypothesized that individuals with a history of mTBI would exhibit increased NE relative to controls, despite normal performance on traditional neuropsychological measures.

Methods: Thirty-eight male criminal offenders completed semi-structured interviews of their mTBI and other history, conventional neuropsychological testing and a computerized motor planning task that quantified NE.

Results: As expected, participants with a history of mTBI exhibited significantly greater NE, despite no group differences in traditional neuropsychological test performance. A greater number of injuries was positively related to NE magnitude and unrelated to traditional measures.

Conclusions: Increased NE indexes sub-clinical sequelae of mTBI and may represent a general marker of mild neurological dysfunction.