Biology subjects

Jezek, K.

Publications and source records attributed to Jezek, K..

3 recordsLinked to original sources

bioRxiv2024

LPS-induced sepsis disrupts brain activity in a region- and vigilance-state specific manner

Sepsis-associated encephalopathy (SAE) is a common complication of sepsis and the systemic inflammatory response syndrome that leads to lasting consequences in survivors. It manifests as early EEG changes, that are region-, time- and state-specific, possibly reflecting distinct mechanisms of injury. Here, we investigated the effects of 5mg/kg lipopolysaccharide (LPS) on hippocampal and cortical sleep-wake states, oscillatory and non-oscillatory neuronal activity, as well as on within and between state dynamics using state-space analysis. LPS induced rapid-onset severe temporal and spatial vigilance state fragmentation, which preceded all other spectral changes by [~]90 minutes. Thereafter, LPS led to specific destabilization and increased delta oscillatory activity in wakefulness, but not NREM sleep, although state transitions remained largely normal. Instead, reduced NREM delta power resulted from aperiodic spectrum changes. LPS specifically reduced higher frequency hippocampal gamma oscillations (60-80Hz peak) in wakefulness, but not cortical high gamma or lower frequency gamma oscillations. These results suggest that disruption of sleep-wake patterns could serve as an early indicator of sepsis and associated encephalopathy, independent of spectral changes. Moreover, treatment aimed at stabilizing vigilance states in early stages of sepsis might prove to be a novel option preventing the development of further pathological neurophysiology, as well as limiting inflammation-related brain damage.

neuroscience↗

bioRxiv2022

Context-independent expression of spatial code in hippocampus

Hippocampus plays a crucial role in formation and retrieval of spatial memory across mammals and episodic memory in humans. Episodic as well as spatial memories can be retrieved irrespectively of subjects awake behavioral state and independently of its actual spatial context. The nature of hippocampal network activity during such out-context retrieval has not been described so far, though. Theoretically, context-independent spatial memory retrieval suggests a shift from the hippocampal spatial representations coding the actual- to the remembered context. In this study we show in rats that CA3 neuronal population can switch spontaneously across representations and transiently activate another stored familiar spatial pattern without a direct external sensory cuing. This phenomenon qualitatively differs from the well described sharp wave-related pattern reactivations during immobility. Here it occurred under theta oscillatory state during an active exploration and reflected the preceding experience of sudden environment change. The respective out-context coding spikes appeared later in the theta cycle than the in-context ones. Finally, the experience induced as well an emergence of population vectors with a co-expression of both codes segregated into different phases of the theta cycle.

neuroscience↗

bioRxiv2022

Sepsis-induced brain state instability

Sepsis-associated brain dysfunction (SABD) is a frequent severe complication of sepsis and the systemic inflammatory response syndrome. It is associated with high mortality and a majority of survivors suffer long-term neurological consequences. Here, we aimed at better understanding the effects of SABD on oscillatory brain states in an acute rat model of sepsis induced by high dose LPS (10 mg/kg). To focus on intrinsically generated brain state dynamics, we used a urethane model that spares oscillatory activity in REM- and NREM-like sleep states. Soon after the intraperitoneal LPS injection we observed a robust instability of both oscillatory states resulting in tripling amount of state transitions that lasted for several hours, although the overall time spent in either state did not change. Analysis of power spectra showed opposing shifts in low frequency oscillations (1-9 Hz) that resulted in increased similarity between both states in 2-D state space. The described spectral characteristics of sepsis-induced EEG state instability might point to a mechanism underlying severe sleep fragmentation as described both in sepsis patients and in SABD animal models.

neuroscience↗