Impact of Traumatic Brain Injury on different formats of topographical representation.

Navigating in the environmental space requires processing and integrating different types of visuospatial information. It depends on activity of a large-scale brain network, which regions play different and complementary contributions. Thus, white matter damage may greatly impact on this complex skill. Here, we aimed to test whether and how diffused axonal damage, proper of traumatic brain injury (TBI), affects spatial navigation. We use the laboratory-based setting (LBS) we recently developed, which allows for testing route learning (RK; route learning task), landmark knowledge (LK; landmark recognition task), survey knowledge (SK; landmark positioning task) and landmark ordering (LO; ordering task). We compared the performance of patients with TBI (N = 18) with that of healthy controls (HC; N = 34) matched for age and gender. The inverse efficiency score index (IES), that balances and integrates accuracy and response time, was computed for each task of the LBS. Then we performed Mann-Whitney U tests to compare indexes of the two groups; in each group, Spearman's correlation coefficient was computed as well. The two groups differed significantly on the second attempt of the RK, but not on the third attempt, suggesting that although it took more time, patients with TBI learned the path similarly to the HC. However, performances differed significantly in LK and SK task, suggesting a deficit in recollecting figurative memory of the landmarks and shifting from an egocentric to an allocentric representation. Performance did not differ significantly in the LO. Consistently with our previous results, performances on LO were associated with SK in HC; instead, they were associated with RK in patients with TBI. Results suggest that HC used SK to perform LO; instead, TBI used the route information they had correctly acquired, suggesting a different strategy in this sample of patients.