Systems Neuroscience

PROJECT SUMMARY/ABSTRACT Many animals rely on spatial cognition for daily survival in order to recognize familiar places and process movements through or between locations. A variety of space-encoding cells in the hippocampus are important for spatial behaviors in mammals. However, neural encoding of space remains uncharacterized in other vertebrate taxa, including amphibians, whose simpler brain structure suggests alternative mechanisms of encoding space.

How are complex behaviors that require the coordination of multiple muscle systems produced? How does the brain suddenly turn them “on”? Vocalizations are seemingly simple, yet to occur, ~100 muscles must be coordinated, such as those for articulation (laryngeal and tongue) and breathing. Moreover, vocalizations must seamlessly integrate with or perhaps even override the breathing rhythm. Innate vocalizations occur in multiple behavioral contexts, like mating, and are presumed to be initiated by a gatekeeper, the periaqueductal gray (PAG).

This proposal will investigate neural circuits driving negative phototaxis in an emerging model for neural circuit analysis: larvae of the primitive chordate Ciona. Ciona larvae have a number of features that make them ideally suited for this project. They are small and transparent, and have only 177 CNS neurons. Moreover, putative circuits for phototaxis have been identified from the Ciona connectome. Negative phototaxis in Ciona larvae consists of two phases.

Project Summary Primary motor cortex (M1) and the locus ceruleus (LC) both contribute in essential ways to the generation of purposive movements – with M1 and its pyramidal tract (PT) neurons involved in action planning and execution, the and LC and its noradrenergic axonal projections involved in aspects relating to arousal and attention. The cellular- and circuit-level mechanisms by which these two major brain systems communicate and interact are not well understood.

Project Summary: Memory enables animals to acquire, store, and recall knowledge of the world through experience and use this knowledge to maximize reward and avoid danger. Understanding the circuit mechanisms within and between brain regions that underlie the formation and recall of memories is considered one of the great scientific challenges of our time, and has the potential to drastically influence the treatment of memory disorders. The hippocampus is both necessary and sufficient for the formation and recall of episodic memories—memories of experiences placed in time and space.

PROJECT SUMMARY/ABSTRACT When learning in complex, realistic, or even real worlds, we have the benefit of using different strategies adaptively. For most primate brains, adaptive means adjusting as a function of where we are, who we are with, and what things of use are in view or in reach. Learning theories like Complementary Learning Systems (CLS) originally suggested that the hippocampus and neocortical structures contributed distinct computations to represent different kinds of memory.

The neural circuits of animals, including humans, are the combined product of adaptation by natural selection and the evolutionary history of a species. Distinguishing which features of neural circuits represent fundamental principles of circuit design versus the quirks of a particular model species requires comparative approaches. Features of neural circuit design and architecture that have evolved independently multiple times in distantly related species indicate elements of optimal solutions to solving a particular behavioral or cognitive problem.

ABSTRACT The taste of food is a critical factor that determines whether an organism will accept or reject a food source. In addition, the sensory perception of food taste changes significantly depending on the metabolic state of animals. Despite the significant progress in understanding the homeostatic biology of food intake in the mammalian brain, how metabolic states (e.g., how hungry an animal is) alter the perception of food taste at the level of specific neuronal circuits remains poorly understood.

Project Summary The brain uses sensory representations to assess risk and predict reward in order to adjust behavior. Per­ ception is a multisensory process. To make reliable predictions, it is advantageous for the brain to combine more than one sensory modality to represent the world. In humans, as in many species, there is evidence for sophisticated forms of learning, such as crossmodal enhancement, where the integration of multiple stimuli from different modalities facilitates memory formation and/or improves discrimination.

Assessing social signals, such as vocalizations, figures prominently in the outcome of aggressive encounters, including the potential to win a fight or prevent escalation resulting in physical injury. Among vertebrates, the neural circuitry integrating sensation, for example what an individual hears, with modulation of aggressive output, is distributed throughout the forebrain and conserved across vertebrate lineages. Social behavior is thought to be an emergent property of activity across this network, and audition plays a prominent role in modulating aggression in primates and birds.