ETD

• Circadian rhythm
• Circuiti corticali
• Complessità
• Complexity
• Cortical circuits
• Entropia
• Entropy
• High-density electrophysiological recordings
• Information theory
• Registrazioni elettrofisiologiche ad alta densità
• Ritmo circadiano
• Teoria dell'informazione

Understanding the principles of neural coding is a central challenge in neuroscience. The excitation inhibition ratio is a key determinant of neural circuit dynamics, regulating network excitability, temporal coordination, and computational capacity. In rodents, intracellular chloride concentration displays circadian modulation, rising during the active phase (night) and altering the GABAA inhibitory driving force. We hypothesized that this biophysical shift inherently predisposes cortical networks to enhanced computational properties during the active phase. We performed high-density electrophysiological recordings with Neuropixels 2.0 in the primary visual cortex (V1) of anesthetized mice at midday and midnight, during baseline and stimulus-evoked activity. While global activity levels, quantified via network burst properties and mean firing rates, remained unchanged, evaluating network dynamics within a temporal population coding framework revealed several computational advantages during the active phase. Network activity defined as instantaneous population firing patterns displayed higher Shannon entropy during the night, suggesting higher information processing and representational efficiency. Furthermore, the temporal trajectories of population activity during the night exhibited lower regularity and temporal predictability, indicating more complex dynamics that generate more information over time. Finally, population state entropy exhibited scale-invariant behavior across temporal resolutions in both circadian phases while remaining systematically higher during the night, suggesting that information is embedded across all considered temporal scales. Overall, these findings show that the circadian clock actively configures the computational capacity of cortical circuits, promoting an optimized regime for sensory encoding during the active phase.