Neural correlates of apathy revealed by lesion mapping in participants with traumatic brain injuries

Abstract

Apathy, common in neurological disorders, is defined as disinterest and loss of motivation, with a reduction in self-initiated activity. Research in diseased populations has shown that apathy is associated with variations in the volume of brain regions such as the anterior cingulate and the frontal lobes. The goal of this study was to determine the neural signatures of apathy in people with penetrating traumatic brain injuries (pTBIs), as to our knowledge, these have not been studied in this sample. We studied 176 male Vietnam War veterans with pTBIs using voxel-based lesion-symptom mapping (VLSM) and apathy scores from the UCLA Neuropsychiatric Inventory (NPI), a structured inventory of symptoms completed by a caregiver. Our results revealed that increased apathy symptoms were associated with brain damage in limbic and cortical areas of the left hemisphere including the anterior cingulate, inferior, middle, and superior frontal regions, insula, and supplementary motor area. Our results are consistent with the literature, and extend them to people with focal pTBI. Apathy is a significant symptom since it can reduce participation of the patient in family and other social interactions, and diminish affective decision-making.

Keywords: apathy; cingulate cortex; fatigue; insula; traumatic brain injury; voxel-based lesion-symptom mapping.

Figure 1

Color indicates the number of participants' lesions overlapping at each voxel for the apathy analysis. We required a minimum of four lesion cases at each voxel in order for that voxel to be included in VLSM analysis. The left is on the viewer's right.

Figure 2

Color indicates the number of the 28 participants with apathy symptoms who had lesions overlapping at each voxel. We required a minimum of four lesion cases at each voxel for that voxel to be included in VLSM analysis. The left is on the viewer's right.

Figure 3

Color indicates brain regions where the association between voxel lesion location and apathy score is statistically significant, based on t‐tests and after correction for multiple comparisons (FDR). The left is on the viewer's right.

Figure 4

Sagittal image showing the cingulate lesions associated with apathy.