Inertial Measurement of Head Tilt in Rodents: Principles and Applications to Vestibular Research

Abstract

Inertial sensors are increasingly used in rodent research, in particular for estimating head orientation relative to gravity, or head tilt. Despite this growing interest, the accuracy of tilt estimates computed from rodent head inertial data has never been assessed. Using readily available inertial measurement units mounted onto the head of freely moving rats, we benchmarked a set of tilt estimation methods against concurrent 3D optical motion capture. We show that, while low-pass filtered head acceleration signals only provided reliable tilt estimates in static conditions, sensor calibration combined with an appropriate choice of orientation filter and parameters could yield average tilt estimation errors below 1.5∘ during movement. We then illustrate an application of inertial head tilt measurements in a preclinical rat model of unilateral vestibular lesion and propose a set of metrics describing the severity of associated postural and motor symptoms and the time course of recovery. We conclude that headborne inertial sensors are an attractive tool for quantitative rodent behavioral analysis in general and for the study of vestibulo-postural functions in particular.

Machine Learning Analysis of Physical Activity Data to Classify Postural Dysfunction

“…There is a growing body of evidence that inertial sensors can be used to investigate vestibulopathy. IMUs affixed to rodent skulls offer kinematic data that differentiates models of unilateral vestibular disease and controls 11 . Alessandrini and colleagues found accelerometer‐based features correlated with laboratory measures of sway from a force plate, suggesting use in posturography 9 .…”

“…IMUs affixed to rodent skulls offer kinematic data that differentiates models of unilateral vestibular disease and controls. 11 Alessandrini and colleagues found accelerometer-based features correlated with laboratory measures of sway from a force plate, suggesting use in posturography. 9 Further, the authors demonstrate that accelerometer-based features, such as sway area, significantly differ between subjects with unilateral vestibulopathy and age-matched controls.…”

“…HAR principles applied to the study of neuro‐motor diseases, such as Parkinson's have further been used to formulate objective symptom assessments, track response to therapeutics, and diagnose disease subtypes 5,6 . Although patients experiencing vestibular dysfunction exhibit measurable differences in gait and posture compared with healthy controls, 7–10 the application of inertial sensors and kinematic analysis in the setting of vestibulopathy has to date been limited to small cohort studies in controlled environments, that is, the lab or clinic 11,12 . However, whether inertial measurements of daily activities through passive evaluation in real‐world environments can similarly be used to study the vestibular system, it remains unclear.…”

Naturalistic neuroscience and virtual reality

“…Currently, there are no VR headsets for animals, although they may be in development, as they are mainly a miniaturization issue, apart from species-specific needs. Technology in this direction includes head-mounted camera systems to track eye movements (Meyer et al, 2018 ) and inertial sensors for head-tracking in rodents (Venkatraman et al, 2010 ; Fayat et al, 2021 ).…”