id_816. RECORDING AND ANALYSIS OF VISUAL EVOKED POTENTIALS IN FREELY MOVING RATS
Čestmír Vejmola1, Ivana Chrtková2,4, Jan Hubený2,5, Nina Miniariková1, Martin Toman1, Tomáš Páleníček1,3
1 Psychedelic Research Center, National Institute of Mental Health, Klecany, Czech Republic
2 Applied Technology in Neuroscience, National Institute of Mental Health, Klecany, Czech Republic
3 Third Faculty of Medicine, Charles University, Prague, Czech Republic
4 Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Klecany, Czech Republic
5 Department of Healthcare Technology, National Institute of Mental Health, Klecany, Czech Republic
INTRODUCTION: Visual evoked potentials (VEPs) are widely used to assess visual pathway integrity in humans, yet their application in awake rodents remains limited due to methodological constraints. Most rodent VEP studies rely on anesthesia, which alters cortical dynamics and may confound translational interpretation.
AIM(S): We aimed to develop and validate a methodology for recording high-quality VEPs in awake rats and to characterize stimulus-specific response profiles and adaptation dynamics across flash, pattern-reversal, and motion-onset paradigms.
METHOD(S): Ten male Long-Evans rats were implanted with 38 epidural electrodes covering the skull. Animals were head-fixed while standing on a freely rotating spherical treadmill, allowing natural locomotion. Visual stimuli (100× flash, 200× pattern-reversal, 300× motion-onset trials) were presented with jittered interstimulus intervals (~2.5 s). EEG was recorded at 1000 Hz and preprocessed in MNE-Python. VEP components were extracted from occipital electrodes (V7/V8). Adaptation of the P1 component was assessed using 20-trial sliding windows (95% overlap) and evaluated with Spearman correlation and permutation testing.
RESULTS: All stimulus types elicited robust, topographically specific responses maximal over the occipital cortex. Flash stimuli produced high-amplitude N40–P90 complexes, pattern-reversal evoked early P45–N60 peaks, and motion-onset generated N120–P250 responses. Adaptation analysis revealed a significant decrease in P1 amplitude and latency over time for flash stimuli (p < 0.001), moderate modulation for motion-onset (p < 0.01), and minimal change for pattern-reversal stimulation.
CONCLUSIONS: We demonstrate reliable VEP recording in awake rats without anesthesia, preserving physiological response properties. Distinct waveform morphology and adaptation patterns across stimulus types reflect functional differences in visual processing streams and support the translational utility of advanced visual paradigms in rodent models.
FINANCIAL SUPPORT: The work was supported by grants GAČR 23-07578K, SVV 260648/2024, ERDF CZ.02.01.01/00/22_008/0004643, LM2023049, the Cooperatio Neurosciences program, and the PSYRES foundation.