INTRODUCTION: Changes in the sense of smell are associated with cognitive decline and major neurological disorders, both linked to disrupted brain rhythms. Nasal respiration not only supports odor detection but also entrains neural activity across widespread brain regions, including corticolimbic circuits, playing a role in learning and memory processes.

AIM(S): This study's aim was to explore how input from the NE affects electrical activity patterns.

METHOD(S): We developed a novel, reversible model of anosmia in rats by infusing gadolinium into the nares. Olfactory function was assessed over time. Local field potentials (LFP) were recorded from the olfactory bulb, ventral striatum, and prefrontal cortex during wakefulness and slow-wave sleep. Immunohistochemical analysis measured olfactory sensory neuron integrity via olfactory marker protein (OMP) expression.

RESULTS: Gadolinium infusion induced a significant reduction in olfactory function lasting up to two weeks, with gradual recovery thereafter. During wakefulness, LFP recordings from the olfactory bulb showed reduced amplitude in the respiration-related rhythm (1–10 Hz) and gamma band (30–90 Hz) in treated animals. Stronger respiration-locked olfactory bulb activity correlated with better olfactory performance across all subjects. Anosmia was also associated with decreased 1–10 Hz power in the ventral striatum and prefrontal cortex, and diminished gamma oscillations in the ventral striatum. These neural disruptions were specific to wakefulness; slow-wave sleep activity remained unaffected. Immunohistochemistry confirmed a loss of olfactory sensory neurons, indicated by decreased OMP expression in treated rats.

CONCLUSIONS: This reversible anosmia model demonstrates disrupted brain oscillations during wakefulness in key brain regions involved in cognition. These results suggest that altered neural rhythms are a direct consequence of anosmia and may contribute to the cognitive impairments linked to impaired olfactory processing.

FINANCIAL SUPPORT: Narodowe Centrum Nauki