Biology subjects

Tilden, E. I.

Publications and source records attributed to Tilden, E. I..

3 recordsLinked to original sources

bioRxiv2026

A molecular integrator of sleep duration and interruption

Sleep is regulated across multiple timescales. Transitions between sleep and wake happen within seconds1,2; individual sleep bouts last minutes to hours3; and homeostatic sleep need has classically been tracked across multiple bouts4. Rapid sleep-to-wake transitions are driven by identified neurons, circuits, and neuromodulators1, while slow wave activity correlates with sleep need across hours5,6. However, no signal has been shown to encode sleep history within individual sleep bouts, the timescale at which the brain must continuously monitor how much sleep has occurred and how likely waking is at any given moment. Biochemical signals downstream of sleep/wake-associated neuromodulators display slower dynamics than the neuromodulators themselves7,8, making them candidate encoders of within-bout sleep history. Here, by measuring protein kinase A substrate phosphorylation (PKA-SP) in real time in freely behaving mice7-9, we show that membrane PKA-SP decreases exponentially within each sleep bout with consistent kinetics across bouts, integrates sleep duration and sleep interruption, and continuously forecasts moment-to-moment waking probability. Following sleep deprivation, PKA-SP reaches lower levels at the end of sleep bouts, correlating with increased sleep need dissipation. These findings identify a molecular signal encoding within-bout sleep history, revealing how biochemical dynamics bridge fast arousal circuits and the slow timescale of classical sleep homeostasis.

neuroscience↗

bioRxiv2023

A Cre-dependent reporter mouse for quantitative real-time imaging of Protein Kinase A activity dynamics

Intracellular signaling dynamics play a crucial role in cell function. Protein kinase A (PKA) is a key signaling molecule that has diverse functions, from regulating metabolism and brain activity to guiding development and cancer progression. We previously developed an optical reporter, FLIM-AKAR, that allows for quantitative imaging of PKA activity via fluorescence lifetime imaging microscopy and photometry. However, using viral infection or electroporation for the delivery of FLIM-AKAR is invasive, cannot easily target sparse or hard-to-transfect/infect cell types, and results in variable expression. Here, we developed a reporter mouse, FL-AK, which expresses FLIM-AKAR in a Cre-dependent manner from the ROSA26 locus. FL-AK provides robust and consistent expression of FLIM-AKAR over time. Functionally, the mouse line reports an increase in PKA activity in response to activation of both Gs and Gq-coupled receptors in brain slices. In vivo, FL-AK reports PKA phosphorylation in response to neuromodulator receptor activation. Thus, FL-AK provides a quantitative, robust, and flexible method to reveal the dynamics of PKA activity in diverse cell types.

neuroscience↗

bioRxiv2019

Rapid and Active Stabilization of Visual Cortical Firing Rates Across Light-Dark Transitions

The dynamics of neuronal firing during natural vision are poorly understood. Surprisingly, mean firing rates of neurons in primary visual cortex (V1) of freely behaving rodents are similar during prolonged periods of light and darkness, but it is unknown whether this reflects a slow adaptation to changes in natural visual input, or insensitivity to rapid changes in visual drive. Here we use chronic electrophysiology in freely behaving rats of either sex to follow individual V1 neurons across many dark-light (D-L) and light-dark (L-D) transitions. We show that, even on rapid timescales (1s to 10 min), neuronal activity was only weakly modulated by transitions that coincided with the expected 12h/12h light-dark cycle. In contrast, a larger subset of V1 neurons consistently responded to unexpected L-D and D-L transitions, and disruption of the regular L-D cycle with 60 hours of complete darkness induced a robust increase in V1 firing upon re-introduction of visual input. Thus, V1 neurons fire at similar rates in the presence or absence of natural stimuli, and significant changes in activity arise only transiently in response to unexpected changes in the visual environment. Further, although mean rates were similar in L and D, pairwise correlations were significantly stronger during natural vision, suggesting that information about natural scenes in V1 is more readily extractable from correlations than from individual firing rates. Together, our findings show that V1 firing rates are rapidly and actively stabilized during expected changes in visual input, and are remarkably stable at both short and long timescales.

neuroscience↗