Circadian control of sleep-related neuronal activity in lizards.

Although diurnal animals displaying monophasic sleep patterns exhibit periodic cycles of alternating slow-wave sleep (SWS) and rapid eye movement sleep (REMS), the regulatory mechanisms underlying these regular sleep cycles remain unclear. Here, we report that in the Australian dragon exposed to constant darkness (DD), sleep behavior and sleep-related neuronal activity emerged over a 24-h cycle. However, the regularity of the REMS/SWS alternation was disrupted under these conditions.

The dynamics of pattern matching in camouflaging cuttlefish.

Many cephalopods escape detection using camouflage. This behaviour relies on a visual assessment of the surroundings, on an interpretation of visual-texture statistics and on matching these statistics using millions of skin chromatophores that are controlled by motoneurons located in the brain. Analysis of cuttlefish images proposed that camouflage patterns are low dimensional and categorizable into three pattern classes, built from a small repertoire of components.

Wake-like skin patterning and neural activity during octopus sleep.

While sleeping, many vertebrate groups alternate between at least two sleep stages: rapid eye movement and slow wave sleep, in part characterized by wake-like and synchronous brain activity, respectively. Here we delineate neural and behavioural correlates of two stages of sleep in octopuses, marine invertebrates that evolutionarily diverged from vertebrates roughly 550 million years ago (ref. ) and have independently evolved large brains and behavioural sophistication.

A claustrum in reptiles and its role in slow-wave sleep.

The mammalian claustrum, owing to its widespread connectivity with other forebrain structures, has been hypothesized to mediate functions that range from decision-making to consciousness. Here we report that a homologue of the claustrum, identified by single-cell transcriptomics and viral tracing of connectivity, also exists in a reptile-the Australian bearded dragon Pogona vitticeps. In Pogona, the claustrum underlies the generation of sharp waves during slow-wave sleep.

Visual perception and cuttlefish camouflage.

Visual perception is inherently statistical: brains exploit repeating features of natural scenes to disambiguate images that could, in principle, have many causes. A clear case for the relevance of statistical inference in vision is animal camouflage. Although visual scenes are each composed of unique arrangements of pixels, they are usually perceived mainly as groupings of statistically defined patches (sandy/leafy/smooth etc…); this fact is exploited by camouflaging animals.

Elucidating the control and development of skin patterning in cuttlefish.

Few animals provide a readout that is as objective of their perceptual state as camouflaging cephalopods. Their skin display system includes an extensive array of pigment cells (chromatophores), each expandable by radial muscles controlled by motor neurons. If one could track the individual expansion states of the chromatophores, one would obtain a quantitative description-and potentially even a neural description by proxy-of the perceptual state of the animal in real time.

On the Value of Reptilian Brains to Map the Evolution of the Hippocampal Formation.

Our ability to navigate through the world depends on the function of the hippocampus. This old cortical structure plays a critical role in spatial navigation in mammals and in a variety of processes, including declarative and episodic memory and social behavior. Intense research has revealed much about hippocampal anatomy, physiology, and computation; yet, even intensely studied phenomena such as the shaping of place cell activity or the function of hippocampal firing patterns during sleep remain incompletely understood.

New Methods to Study Gustatory Coding.

The sense of taste allows animals to detect chemicals in the environment, giving rise to behaviors critical for survival. When Gustatory Receptor Neurons (GRNs) detect tastant molecules, they encode information about the identity and concentration of the tastant as patterns of electrical activity that then propagate to follower neurons in the brain. These patterns constitute internal representations of the tastant, which then allow the animal to select actions and form memories.

Slow waves, sharp waves, ripples, and REM in sleeping dragons.

Sleep has been described in animals ranging from worms to humans. Yet the electrophysiological characteristics of brain sleep, such as slow-wave (SW) and rapid eye movement (REM) activities, are thought to be restricted to mammals and birds. Recording from the brain of a lizard, the Australian dragon Pogona vitticeps, we identified SW and REM sleep patterns, thus pushing back the probable evolution of these dynamics at least to the emergence of amniotes.

Spatiotemporal Coding of Individual Chemicals by the Gustatory System.

Unlabelled: Four of the five major sensory systems (vision, olfaction, somatosensation, and audition) are thought to use different but partially overlapping sets of neurons to form unique representations of vast numbers of stimuli. The only exception is gustation, which is thought to represent only small numbers of basic taste categories. However, using new methods for delivering tastant chemicals and making electrophysiological recordings from the tractable gustatory system of the moth Manduca sexta, we found chemical-specific information is as follows: (1) initially encoded in the population of gustatory receptor neurons as broadly distributed spatiotemporal patterns of activity; (2) dramatically integrated and temporally transformed as it propagates to monosynaptically connected second-order neurons; and (3) observed in tastant-specific behavior.