Comparing behavioural sampling methods in shelter dogs: implications for enrichment studies.

Wilson’s disease (WD), an autosomal recessive disorder of copper metabolism ( gene mutation), leads to pathological copper accumulation in the liver and brain, particularly within the basal ganglia, cerebellum, and cortical regions [, ]. Neurological manifestations, such as tremor, dystonia, and dysarthria, occur in approximately 40–60% of patients and severely impair their quality of life []. Notably, clinical observations suggest that emotional states modulate tremor amplitude and frequency in WD patients [, ]; however, the neural mechanisms underlying this emotion–tremor coupling remain poorly understood. Current pathophysiological models of WD underscore copper-induced neurotoxicity in the lentiform nucleus and cerebellar dentate nuclei—a process that disrupts the cortico-striato-thalamocortical (CSTC) circuits critical for motor control []. However, these models largely overlook the role of emotion-processing networks in motor symptom variability. Emerging evidence indicates that WD patients exhibit deficits in facial emotion recognition and heightened social anxiety [], paralleling findings in functional movement disorders where negative emotions exacerbate tremor []. This raises a critical question — how do emotion-processing networks interact with motor circuits to drive tremor variability in WD? Dynamic systems theory posits that motor output emerges from the interaction between neural circuitry, body dynamics, and environmental constraints []. Within this framework, emotional states may act as “environmental constraints” that bias sensorimotor integration. Similarly, embodied cognition theory proposes that bodily states (e.g., tremor-induced proprioceptive feedback) directly shape emotional experiences, forming a closed loop between perception, emotion, and action []. For WD patients, chronic tremor may distort body schema representations (as measured by the Body Image Disturbance Questionnaire, BIDQ), amplifying emotional arousal and further destabilizing motor output — a hypothesis supported by recent magnetic resonance imaging (MRI) studies showing aberrant insula activation during emotional tasks in WD []. Electroencephalogram (EEG) microstates, which are transiently stable scalp field topographies (100–200 ms duration), provide a powerful tool to capture the rapid dynamics of large-scale brain networks []. Four canonical microstates (A-D) have been linked to distinct networks: auditory (A), visual (B), salience (C), and attentional (D) networks []. Notably, microstate C, associated with the anterior insula and anterior cingulate cortex, is modulated by emotional arousal and correlates with interoceptive awareness [] a process likely disrupted in WD owing to basal ganglia-cerebellar pathology. Despite these advances, critical gaps persist: (1) No previous study has quantitatively examined how emotional states dynamically modulate tremor kinematics in WD using motion tracking. (2) The neurophysiological signatures of emotion-tremor interactions, particularly EEG microstate dynamics (salience network activity), have never been explored in WD. (3) The structural substrates (lentiform nucleus, cerebellum, frontal cortex) underlying emotion-motor integration in WD remain unidentified. To our knowledge, this is the first study to combine kinematic tremor analysis, EEG microstate dynamics, and structural MRI to investigate emotion-tremor coupling in WD.