Circuit Diagrams

Summary Multimodal sensory information is converged through poly-synaptic pathways to the hippocampus to form integrated representations and encode memories of the world, which in turn guide our future behavior through multiple poly-synaptic downstream pathways. It is well known that each of the brain regions in this circuit consists of various neuronal cell types or groups which are distinct in connectivity and functions.

SUMMARY Norepinephrine is a neurotransmitter thought to be involved in driving behavioral flexibility. It is released by a small number of neurons throughout the neocortex. Little is known, however, about what signals these neurons provide, and how targets in neocortex use those signals, in the context of well-controlled behaviors in mammals. This proposal aims to determine functions of norepinephrine-releasing neurons in the locus coeruleus, the primary source of forebrain norepinephrine.

Abstract    A major challenge in the treatment of neurological diseases is the elaborate and diffuse nature of neural  circuits, where physically proximal neurons are engaged in functionally different pathways. The ability to target  neurons based on function, rather than location, is critical to improving treatments for disease. In Parkinson’s 

Many animal behaviors are organized into long-lasting states, perhaps most strikingly in the sleep/wake and emotional states that mammals display. However, the fundamental mechanisms that allow animals to initiate, maintain and terminate these states are unknown. Biogenic amine and neuropeptide neuromodulators are critical for the generation of behavioral states, but a mechanistic understanding of how neuromodulators act on circuits to generate stable circuit-wide patterns of neural activity has been lacking, largely due to the complexity of neuromodulation in mammalian circuits.

Project Summary / Abstract Encoding of environmental location and navigational behavior in mammals involves large ensembles of specific neuron types across multiple interacting brain regions. “Place cell” and “grid cell” mapping of spatial location in the CA1 region of hippocampus and medial entorhinal cortex (EC), respectively, is thought to be fed forward to associative cortical brain regions including the posterior parietal cortex (PPC) and retrosplenial cortex (RSP) to map conjunctions of egocentric and external spatial relationships.

Abstract This study aims to understand how the ensemble activity and network architecture of a neuronal population guides natural and learned behavior.

Development of predictive coding networks for spatial navigation Summary: Mammalian navigation uses internal models to predict the spatial-temporal statistical regularity of the sequence of environmental locations. Predictive coding theories view the brain as Bayesian interpreter that computes the difference between the external stimuli and an internal model of the world. It is increasingly understood that sequential spatial information is represented by temporal sequences of ensemble neuronal firing in the hippocampus.

Project Summary During behavior, the oculomotor system is tasked with selecting objects from an ever-changing visual field and guiding eye movements to these locations. The attentional priority given to sensory targets during selection can be strongly influenced by external stimulus properties (“bottom-up”) or internal goals based on previous experience (“top-down”).

ABSTRACT A major goal in clinical neuroscience is to develop efficient treatments to prevent or minimize the loss of brain function caused by pathological decreases or increases of neuronal activity, which are hallmarks of a wide variety of neurological disorders. Interestingly, in some instances, the brain has evolved mechanisms to partially correct abnormal neuronal function.

ABSTRACT Persistent neural activity, a sustained response following brief stimuli that is observed in many brain networks, needs to be appropriately tuned to meet the exacting demands of various motor and cognitive tasks. One task that has been particularly amenable to understanding persistent neural activity is the oculomotor control of gaze position.