Systems Neuroscience

Project Summary Interactions between the auditory and visual systems are among the most well-established cases of crossmodal interplay, yet the overwhelming bulk of the sensory physiology literature reflects studies examining processing confined to a single modality and we understand comparatively little about the circuitry mediating crossmodal interplay, or under what conditions such circuits are active. Audiovisual interactions exist even in primary auditory cortex (AC), with latencies too low to be mediated through purely top-down connections.

Prefrontal cortex (PFC) is critical for a range of high-level cognitive functions, such as attention and decision- making. Studying these processes is difficult, since they are covert, dynamic and under the control of the subject, rather than the experimenter. Their measurement traditionally relies on inferring their presence via behavior.

Abstract Behavior is motivated by reward, and the most powerful rewards are those that satisfy a physiologic need. For decades, neuroscientists have studied the midbrain dopamine system to understand reward and hypothalamic circuits to understand sensing of internal needs. But how these two neural systems are interact to give rise to behaviors like eating and drinking remains poorly understood. Recently, we have used approaches for simultaneous neural recording and manipulation to observe directly the communication between these two systems.

Project Summary The field of artificial intelligence (AI) has recently made remarkable advances that resulted in new and improved algorithms and network architectures that proved efficient empirically in silico. These advances raise new questions in neurobiology: are these new algorithms used in the brain? The present study focuses on a new algorithm developed in the field of reinforcement learning (RL), called distributional RL, which outperforms other state-of-the-art RL algorithms and is regarded as a major advancement in RL.

ABSTRACT Our long-term goal is to generate a complete understanding of how the cerebellum learns to improve movement in response to motor errors. Climbing fibers are thought to play an essential role in this process because they fire during erroneous movement. Their activity reliably excites Purkinje cells, eliciting calcium spikes in their dendrites that can trigger long-term synaptic plasticity at coactive parallel fiber inputs. Plasticity induction ultimately leads to corrective behavior by altering the cerebellum’s response to sensorimotor stimuli that predict mistakes.

Project Abstract Understanding how neuronal computations build up a perception of the external world is fundamental to our understanding of how the brain works. This is particularly relevant to sensory systems, where heterogenous inputs representing distinct sensory features must be re-assembled to generate a perception. How individual neurons in early stages of sensory circuits process parallel inputs, and how these circuit elements later contribute to cortical computations that bind the inputs together is completely unknown.

7. Project Summary/Abstract Human experience is shaped by our senses, which receive diverse inputs from our environment. These varied inputs, however, all contribute to a single integrated representation in our minds of the outside world. Neuroscientists have studied sensory perception, and the integration different sensory modalities like vision, hearing, and touch, for decades, but there are still important unanswered questions about how sensory cells in the brain work, and how the circuits that they form control the flow of information through the brain.

Work on learning in neural systems has focused largely on the effects of plasticity at synapses that provide direct input to the neurons being studied. Learning a model of the environment or a complex skill, however, relies on plasticity that is widely distributed and may occur at synapses far from the neurons driving decisions or actions. As is well-known from multi-layer (or 'deep') artificial networks, distributing learning over multiple layers is substantially more powerful but also more difficult to implement than learning at a single layer.

Abstract Our goal is to generate a predictive model of the spinal cord nociceptive circuits that underlie the initiation of pain perception and behavior. Nociceptive signals are conveyed from the periphery to the spinal cord dorsal horn via highly specialized primary sensory neuron subtypes. These sensory neurons, as well as descending modulatory neurons, form synapses upon an array of morphologically and physiologically distinct classes of dorsal horn interneuron and projection neurons.

ABSTRACT Cephalopods have large and complex brains, and in particular a highly capable visual system. However, their brains evolved independently from vertebrates, and very little is known about how neural circuits in the cephalopod brain process visual information. In fact, there has never been a direct recording of receptive fields in the central visual system of cephalopods. This study will measure neural activity and visual coding in the optic lobe of Octopus bimaculoides, an emerging model organism for cephalopod research.