Ultrasonic Vocalizations as Markers of Anxiety and Depression in Rodent Models of Neurotrauma.

Spinal cord injury (SCI) and traumatic brain injury (TBI) are severe events that cause lasting sensorimotor and autonomic impairments. Both injuries often also lead to psychological and somatosensory dysfunctions such as anxiety, depression, or pain. Preclinical assessment of anxiety and depression in rodents often relies on locomotion-based behavioural tests confounded by motor deficits and pain-related changes. Because rodents cannot self-report sensory or emotional experiences, behavioural outcomes are limited to observable proxies of anxiety and depression. Ultrasonic vocalizations (USVs) offer a complementary, non-locomotor tool that may capture anxiety- and depression-relevant context not detected by behavioural tests. Despite extensive USV research in stress, reward, and social behaviour, applications to neurotrauma remain underexplored, with no studies directly examining USVs in relation to anxiety- or depression-like outcomes after SCI. Even so, evidence from related fields and the limited neurotrauma literature suggests that USVs warrant further exploration as affective readouts after TBI and particularly SCI. USVs may complement behavioural testing by providing socioaffective context without relying on locomotor performance, potentially helping distinguish post-injury anxiety- and depression-like phenotypes from pain-related and other injury-associated changes. By integrating behavioural, neural, and pharmacological evidence, we highlight how USV features may reflect affective dimensions relevant to post-injury anxiety- and depression-like states and outline methodological considerations for validity and specificity. Machine-learning approaches further enable high-throughput, objective detection of subtle affective shifts. With development of collaborative datasets, these methods could reveal consistent affective vocal patterns and lay groundwork for a rudimentary 'lexicon' of rodent affect. Integrating USV analysis into neurotrauma and CNS disease research may refine preclinical models of affective dysfunction and improve triangulated evaluation of treatments targeting chronic mental health outcomes.