Temperature-robust rapid eye movement and slow wave sleep in the lizard Laudakia vulgaris

Abstract

During sleep our brain switches between two starkly different brain states - slow wave sleep (SWS) and rapid eye movement (REM) sleep. While this two-state sleep pattern is abundant across birds and mammals, its existence in other vertebrates is not universally accepted, its evolutionary emergence is unclear and it is undetermined whether it is a fundamental property of vertebrate brains or an adaptation specific to homeotherms. To address these questions, we conducted electrophysiological recordings in the Agamid lizard, Laudakia vulgaris during sleep. We found clear signatures of two-state sleep that resemble the mammalian and avian sleep patterns. These states switched periodically throughout the night with a cycle of ~90 seconds and were remarkably similar to the states previously reported in Pogona vitticeps. Interestingly, in contrast to the high temperature sensitivity of mammalian states, state switches were robust to large variations in temperature. We also found that breathing rate, micro-movements and eye movements were locked to the REM state as they are in mammals. Collectively, these findings suggest that two-state sleep is abundant across the agamid family, shares physiological similarity to mammalian sleep, and can be maintain in poikilothems, increasing the probability that it existed in the cold-blooded ancestor of amniotes.

A flexible implant towards acute intrapancreatic electrophysiology

“…The shank’s maximum width of 850 μm is determined primarily by the resolution of the metal layer. Although we use contact lithography and have produced similar flexible electrode array components with traces of 2 μm (Albeck et al , 2022), we chose to have minimum trace width and spacing of 4.5 μm to ensure reasonable yields and reduce process complexity. Proximal from the shank, the trace width and spacing were increased to reduce the risk of fabrication defects.…”

ReptiLearn: An automated home cage system for behavioral experiments in reptiles without human intervention

“…Second, tracking and manipulating food rewards allows incorporating metabolic considerations into experiments. Third, the arena is compatible with neurophysiological measurements allowing to link thermoregulation with brain activity [ 72 ]. Finally, the ability to dynamically alter thermal conditions using real-time feedback opens new avenues of thermal regulation research and significantly enhances the system’s flexibility.…”

“…Thus, studies in a wide range of species can potentially benefit from our approach. Finally, ReptiLearn facilitates the integration of behavioral assays with neurophysiology to elucidate the brain regions and neuronal population patterns underpinning these cognitive skills [ 72 ]. Recent neuronal recordings from awake reptiles are beginning to reveal the neuronal dynamics underlying brain states [ 72 , 84 , 85 ] and visual processing [ 86 ].…”

“…Finally, ReptiLearn facilitates the integration of behavioral assays with neurophysiology to elucidate the brain regions and neuronal population patterns underpinning these cognitive skills [72]. Recent neuronal recordings from awake reptiles are beginning to reveal the neuronal dynamics underlying brain states [72,84,85] and visual processing [86]. Placing such studies within a behavioral context can shed light on the evolution of cognition and provide a comparative perspective critical for generalized understanding [29,30,[32][33][34][35]81].…”

ReptiLearn: A Smart Home Cage for Behavioral Experiments in Reptiles

“…Second, tracking and manipulating food rewards allows incorporating metabolic considerations into experiments. Third, the arena is compatible with neurophysiological measurements allowing to link thermoregulation with brain activity (69). Finally, the ability to dynamically alter thermal conditions using real-time feedback opens new avenues of thermal regulation research and significantly enhances the system's flexibility.…”