Neural Markers of Vulnerability to Anxiety Outcomes after Traumatic Brain Injury

Abstract

Anxiety outcomes following traumatic brain injury (TBI) are complex, and the underlying neural mechanisms are poorly understood. Here, we developed a multidimensional behavioral profiling approach to investigate anxiety-like outcomes in mice that takes into account individual variability.Departing from the tradition of comparing outcomes in TBI versus sham groups, we identified animals within the TBI group that are vulnerable to anxiety dysfunction by applying dimensionality reduction, clustering and post-hoc validation to behavioral data obtained from multiple assays for anxiety at several post-injury timepoints. These vulnerable animals expressed distinct molecular profiles in the corticolimbic network, with downregulation in GABA and glutamate, and upregulation in NPY markers. Indeed, among vulnerable animals, not resilient or sham controls, severity of anxiety outcomes correlated strongly with expression of molecular markers. Our results establish a foundational approach, with predictive power, for reliably identifying maladaptive anxiety outcomes following TBI and uncovering neural signatures of vulnerability to anxiety..

Multidimensional analysis of behavior predicts genotype with high accuracy in a mouse model of Angelman syndrome

“…Multidimensional analysis of behavior consisted of a series of steps: data selection, standardization, principal component analysis (PCA), k -means clustering, and validation (Fig. 1i ) [ 22 ]. Data selection: Eight total measures (weight, rotarod day 1, rotarod day 5, open field distance traveled, open field center time, marbles buried, nest building, forced swim floating time) from a series of six tests (weight, rotarod, open field, marble burying, nest building, forced swim) were included in multidimensional analysis.…”

“…Here we define multidimensional analysis as the multi-step process of: (a) reducing the dimensionality of large behavioral datasets using principal component analysis (PCA) [ 12 , 13 ], (b) clustering data in principal component space using k-means clustering, and (c) assessing whether behaviorally defined clusters align with animal genotype. Dimensionality reduction and clustering have been validated in various mouse behavioral contexts [ 14 – 22 ]. Here, we tested the hypothesis that multidimensional analysis of mouse behavioral data could accurately distinguish the genotype of Ube3a mutants (a model of Angelman syndrome (AS)) from wild-type littermates.…”

Measuring Anxiety-Like Behaviors in Rodent Models of Traumatic Brain Injury

“…Whereas clinical studies have rigorous inclusion criteria, most pre-clinical studies assessing anxiety after TBI consider the injured group as a homogeneous distribution, rather than considering variability among individuals and using that individual variability following TBI to learn about underlying pathology. Popovitz et al tested male mice on a battery of anxiety tests (EZM, OFT, EPM) at multiple time points following CCI (weeks 1, 3, 5 and 7) and developed a multi-dimensional behavioral profiling technique to identify "resilient" and "vulnerable" subgroups of mice (Popovitz et al, 2021). The authors reported that only about 13% of the injured animals were found to be "vulnerable, " showing increased exploration of anxiogenic regions during testing compared to baseline behavior and to sham-treated animals (Popovitz et al, 2021).…”

“…Popovitz et al tested male mice on a battery of anxiety tests (EZM, OFT, EPM) at multiple time points following CCI (weeks 1, 3, 5 and 7) and developed a multi-dimensional behavioral profiling technique to identify "resilient" and "vulnerable" subgroups of mice (Popovitz et al, 2021). The authors reported that only about 13% of the injured animals were found to be "vulnerable, " showing increased exploration of anxiogenic regions during testing compared to baseline behavior and to sham-treated animals (Popovitz et al, 2021). The behavior of the vulnerable mice had neurobiological correlates in the medial prefrontal cortex, basolateral amygdala, and ventral hippocampus; all areas that are associated with stress and anxiety (Almeida-Suhett et al, 2014;Bryant and Barker, 2020;Kenwood et al, 2021;Liu et al, 2021;McCorkle et al, 2021;Pentkowski et al, 2021).…”

Editorial: Behavioral outcomes of traumatic brain injury

“…They offered guidance for improving the measurement of anxiety-like behavior in the study of TBI, including considerations for the ability of animals to properly perform the test, use of testing batteries, and reporting of common data elements. They further encouraged the use of statistical methods that are sensitive to individual differences, which are often observed in clinical and preclinical TBI studies (Lim et al, 2015 ; Scholten et al, 2016 ; Popovitz et al, 2021 ).…”