Understanding Circuits

ABSTRACT A critical step towards understanding how neural circuits drive behavior is the ability to record the activity of all neurons in an organism while it interacts with its environment in an unconstrained manner. A promising vertebrate model system in this regard is the zebrafish larva, which performs complex visually-driven behaviors such as hunting from an early age, and due to its transparency allows large-scale neural imaging at single- neuron resolution.

Although neuroscience has provided a great deal of information about how neurons work, the fundamental question of how neurons function together in a network to produce cognition has been difficult to address. Our group has been at the forefront of developing methods that allow large scale monitoring of identified neurons, monitoring of voltage signals by optical means and elucidation of subcellular events in dendrites, all of which can now be done in awake behaving animals.

Project Summary Working memory, the ability to temporarily hold multiple pieces of information in mind for manipulation, is central to virtually all cognitive abilities. Recent technical advances have opened an unprecedented opportunity to comprehensively dissect the neural circuit mechanisms of this ability across multiple brain areas. The task to be studied is a common form of decision-making that is based on the gradual accumulation of sensory evidence and thus relies on working memory.

Understanding the mechanisms that the nervous system uses to control movement is critical for understanding brain and behavior, and one of the fundamental questions in neuroscience. The control of movement emerges from the activity of different motor control centers, that converge onto output systems, mostly located in the spinal cord. While the spinal circuits that underlie different aspects of motor control have been relatively well characterized, the way by which these circuits are coordinated by supraspinal motor control centers remains elusive.

Project Summary - A realistic multiscale circuit model of the larval zebrafish brain The working group of the BRAIN initiative (BRAIN 2025, a Scientific Vision) identified “the analysis of circuits of interacting neurons as being particularly rich in opportunity, with potential for revolutionary advances

PROJECT SUMMARY The monoamines, which include dopamine, norepinephrine, and serotonin, are evolutionarily conserved neurotransmitters that modulate the activity of excitatory and inhibitory neurons throughout the entire brain, and are thus essential for diverse aspects of physiology and behavior. Abnormalities of monoamine systems contribute to numerous brain disorders including schizophrenia, depression, and Parkinson's disease.

Project summary: Consolidating transient sensory experiences into long-lasting memories is a fundamental function of the brain, linked to synaptic plasticity. The importance of sleep for promoting this process, and the disruptive effect of sleep deprivation on it, have been appreciated for nearly a century.

Abstract Short-term memory (STM) is a core cognitive function, critical for reasoning, decision-making, and flexible behavior. Though it has been recognized as a key function of interest for many decades, the critical neural substrate of STM is little understood.

Abstract Sleep is essential for the maintenance of our cognition and neurological functions, and both quality and quantity of sleep are critical. We likely have known this for the entire human history. Yet, we remain astonishingly ignorant on how the quality and quantity of sleep are regulated. Excitingly, nature has provided us a very small number of human subjects who are genetically wired to sleep shorter hours per day (thus more efficiently). These people usually live a long and healthy (both physically and mentally) life.

Abstract The flow of visual information from the retina, through the dorsal lateral geniculate nucleus (dLGN) to the cortex, is regulated by behavior. However, the dynamic circuit interactions that occur in the dLGN of awake animals, and their modulation by behavior, have yet to be revealed. The purpose of this proposal is to develop tools to determine how inhibitory circuits of the dLGN (which utilize the neurotransmitter gamma amino butyric acid, GABA) interact in vivo, and how they collectively shape vision in the context of behavior.