Localization of a medial temporal lobe–precuneus network for time orientation
Time orientation, or the ability to match one's personal sense of time with a universal reference, is a fundamental cognitive process routinely assessed in neurological and neuropsychological evaluations. Despite its clinical ubiquity, the regional neuroanatomy supporting time orientation remains poorly understood. Large bilateral lesions have been loosely associated with time disorientation, but the specific brain regions implicated by focal, unilateral damage were largely unknown.
550 patients with acquired focal brain lesions were identified from the Iowa Neurological Patient Registry. Time orientation was assessed three or more months after lesion onset using the Benton Temporal Orientation Test (BTOT); 39 patients met criteria for chronic time disorientation. Multivariate lesion-symptom mapping (LSM) identified brain regions where damage was statistically associated with disorientation. Functional lesion network mapping (fLNM) then used normative resting-state fMRI connectome data to characterize the broader functional network in which those lesion sites were embedded. Structural lesion network mapping (sLNM) used normative diffusion tensor data to characterize the white matter tracts connecting network nodes. Memory impairment was evaluated in parallel to assess anatomical and behavioral overlap with time disorientation.
LSM revealed that damage to the precuneus, medial temporal lobes, and occipito-temporal cortex was most strongly associated with time disorientation. LNM demonstrated that these regional findings converged on a network connecting the precuneus and medial temporal lobe. A strong behavioral and anatomical association was found between time disorientation and memory impairment, though the left posterior precuneus showed involvement in time disorientation in the absence of severe memory impairment, suggesting partial dissociability between the two processes.
Published in Annals of Neurology (2023), Vol. 94(3), pp. 421–433. The study was featured on the journal cover.