Jian-Young Wu - US grants

The long term objective of this proposal is to understand the neuronal organization that underlies the generation of behaviors by simple nervous systems. To accomplish this goal, we will use voltage sensitive dyes imaging techniques to monitor a large fraction of neurons when behaviors are generated. We plan to study two molluscan ganglia, the Aplysia abdominal ganglion and the Clione intestinal ganglion. We have found that about 300 neurons are activated in the Aplysia abdominal ganglion during two kinds of gill withdrawal behaviors and about 70 per cent of the active neurons are activated in both behaviors. This suggests there may be a large distributed neuronal network in this ganglion. For Aplysia, we plan to monitor a large fraction of neurons during normal and altered behaviors. There are four specific aims: I. To test three models for possible neuronal organization suggested by our preliminary data. II. To examine how neurons are shared by different behavioral events III. To examine the interaction between evoked behavior and intrinsic rhythms and between two behaviors initiated close in time. IV. To study how system changes when the activity of individual neurons is modified and to find important interneurons in the ganglion. With these aims we will try to understand the neuronal organization in this ganglion and the role of individual neurons in a large and extensively inter- connected neuronal network. We will also examine the dynamic behavior of this simpler nervous system and explore the hypothetical "temporary circuits" which forms only during specific behaviors. We also plan to study a smaller nervous system-- the Clione intestinal ganglion. This ganglion has been evaluated in our preliminary experiment and may be unique for optically monitoring all the neurons during behaviors. Two specific aims are proposed on this new preparation: I. To identify all the neurons in the ganglion by combining voltage sensitive dye imaging and phase contrast enhancement. Neurons will be identified by both morphological features and the activity patterns during different behaviors. II. To study how neuronal activity changes when the neuronal hardware varies. We have found that there are a large variations in number of neurons in this ganglion. We will try to examine how neuronal activity patterns change when neurons are missing or there are extra neurons.

The long-term objective of this study is to understand the local population interactions in neocortex, an important process for both normal cortical functioning and for neurological disorders such as epilepsy. Our approach is to examine the spatio-temporal patterns and cellular properties of population activity in intrinsic cortical circuits. We hypothesize that one basic form of population activation in neocortex is the dynamically organized multi-neuronal ensemble. In our previous study we found a local co-activation in adult cortical slices which is related to the activity patterns in the cortex. This kind of co- activation is dynamically organized, all-or-none population event with an asynchronized, low density of spikes. It could be evoked by a proper stimulation or spontaneously occurred as a propagating activation during 7 to 10 Hz oscillations. This proposal will utilize voltage-sensitive dye imaging and electrophysiological methods to further study the spatio-temporal dynamics and neuronal activities of this cortical population event. There are four specific aims. Aim 1 will examine the proper stimulation patterns which can evoke or interact with this activity, and explore whether this activity can commonly occur in different cortical areas. Aim 2 will study the network and cellular mechanisms which sustain this co-activation. Aim 3 will study propagation of this activity and the interactions with the cortical columnar organization. Aim 4 will study the neuronal activity within this dynamically organized population event. This study will increase our knowledge about the cortical population activities related to the input pattern and intrinsic activities in cortex during normal and pathological conditions.

DESCRIPTION (provided by applicant): The long-term objective of this study is to understand the organization of population neuronal events (correlated activities of millions of neurons). This proposal studies the propagation of excitation waves (a.k.a. traveling waves) in the neo-cortex. Propagating waves occur during sensory and motor processes as well as during neurological disorders such as epilepsy. The mechanisms that control the propagating velocity and directions are important in determining what kind of activity patterns will be carried by the wave and delivered to what part of the cortex, and at what time. Very little is known about the control of the propagating direction and velocity. This is because the waves travel in a distributed neuronal network with parallel and polysynaptic pathways. This proposal will test a hypothesis that propagating waves are generated by coupled local oscillators. The phase relationship among the local oscillators determines the velocity and direction. Voltage-sensitive dye imaging will be used to visualize the propagation waves generated in vitro, in neo-cortical slices. Three Specific Aims are proposed to study the local oscillators during two kinds of "theta" (4-12 Hz) oscillations and an evoked gamma oscillation. Aim 1 consists of two experiments. One experiment will visualize the local oscillators and the boundaries between them. The other experiment will try to separate individual local oscillators with micro cuts to the cortical tissue. Aim 2 will test the hypothesis on the two-dimensional waves generated in tangential cortical slices. Aim 3 will study the neuronal-composition of an evoked gamma oscillation. The spiking activity of individual neurons will be optically monitored in an attempt to understand how the activities of individual neurons compose a population oscillation. This study will not only contribute to the understanding of normal cortical processing but also to the understanding of the initiation and spreading of epileptic seizure activity in the cortex that disrupts the life of about 1% of the U.S. population.

DESCRIPTION (provided by applicant): The long-term goal of this study is to understand the organization of cortical neuronal activity in sustained seizure events and in sensory processing. In this proposal, we will study a special form of population neuronal activity, namely, spiral waves. Spiral waves are a ubiquitous feature of excitable systems in nature, where they play a role in pattern formation and the organization of flow dynamics. Within biomedical science, spiral wave dynamics have been studied extensively in cardiac electrophysiology, and have greatly advanced our understanding of arrhythmogenic mechanisms. Surprisingly, however, only a few researchers have studied spiral dynamics in the brain. Following our recent discovery of spiral waves in rat neocortical slices, in this proposal, we will experimentally verify the existence of spiral waves in rodent neocortex in vivo during seizure-like events and during sensory evoked and spontaneous activity. Cortex in vivo has extensive long-range connections which are not present in brain slices. It is therefore necessary to experimentally examine the initiation and sustaining of spiral waves in intact cortex, given that strong long-range thalamocortical and corticocortical connections may disrupt the development of these spiral waves. Three Specific Aims are proposed to study wave-to-wave interactions in rat sensory and motor cortices. Aim 1 is devoted to improve voltage-sensitive dye imaging methods in order to identify phase singularities at the spiral center. Aim 2 is to examine the incidence rate of spirals during seizure-like activity in various cortical areas. Aim 3 is to investigate spiral dynamics during sensory-evoked activity and sleep-like waves. Studying spiral dynamics in the cortex will directly contribute to understanding of the initiation and sustaining of seizure activity. Spirals are known as a major contributor to arrhythmic activity in cardiac tissue, and extinguishing spirals in the heart has been a therapeutic strategy for preventing cardiac fibrillation. This project is highly relevant to the mission of the NINDS, and should contribute to the understanding of initiation and sustaining of epileptic activity in the cortex, which disturbs the life of about 1% of the US population.

The ability to detect and rapidly respond to changes in the environment is evolutionarily conserved across the animal kingdom. Yet, the neural computation underlying novelty detection have not been precisely defined or quantified. Drs. Wu (Georgetown University), Ding (University of Florida) and Chou (University of California, Los Angeles) will test the hypothesis that dynamics in neuronal activity at the tissue level play a two-step role in novelty-detection. First, a constant or repetitive stimulus establishes a spatiotemporal pattern of neuronal activity that stores an expectation of regularity within the system. Second, stimuli that violate the expected regularity are registered as changes in the patterns of neuronal activity, triggering a response. The research team will use voltage-sensitive dye imaging, optogenetics, high-density EEG, and fMRI, to measure brain activity maps resulting from a common stimulus sequence. The expected neuronal activity and the novelty response to changing the stimulus will be measured in turtles, mice, and humans. The investigators will then quantify these activity maps using mathematical/statistical analysis and develop physically-motivated theoretical models.

This project is expected to provide the initial identification of shared computational principles as well as species- and system-specific implementation of such mechanisms. Results from this research may shed light on a wider range of cognitive functions that rely on novelty detection and novelty-controlled neuromodulation, including attention, learning and memory, and decision-making. Given the importance of such cognitive functions, the proposed research may potentially have long-term, broad societal impact. For example, the opportunity to relate novelty detection capacity of college students to their classroom performance may lead to the development of novelty-stimuli based tools for more effective classroom education. Moreover, the comparative investigation of different species may provide insight into the evolution of learning capacity.

Abstract The sharp-wave ripple (SWR) is a neuronal activity spontaneously occur in the hippocampus. During each SWR, neuronal assemblies coding animals? experiences are reactivated in a temporally compressed manner. This compressed replay is critical for the consolidation of episodic memory. SWRs occur thousands of times every hour, during sleep and quiet restfulness. The occurrence rate reduces with aging and after hippocampal damage resulting from Alzheimer?s disease (AD) and other neurodegenerative conditions. Reduced SWR occurrence rate and quality may contribute to the impairment of memory consolidation of recent experiences. We propose to use ?pacing? (micro-electric shocks at a given rate) to prime the occurrence of SWRs, and to examine whether pacing SWR can improve spatial memory of Alzheimer animal models. Two Specific Aims are proposed: Aim 1 To achieve minimally invasive pacing in free-moving animals through wireless stimulation via an electrode placed in the lateral ventricles, outside of the hippocampus tissue. Preliminary results have demonstrated that SWRs can be induced by non-contact stimulation, by weak electrical field affecting the CA3 tissue in hippocampal slices. Experiments under Aim 1 will extend the preliminary results from brain slice to whole animals, establishing an electrical-field stimulation in lateral ventricle. Aim 2 To test if ?artificial SWRs? induced by pacing can contribute to memory consolidation. We will also test if pacing can improve memory consolidation in AD model (Tg2567) animals. These animals develop significant deficits in spatial memory at 6-8 months of age. We will test if pacing can improve spatial memory in behavioral tests. Deterioration of hippocampus-dependent episodic memory is a hallmark of Alzheimer dementia and other brain degeneration conditions. The proposal will be a first step in develop a therapeutic strategy for improving memory with a non-pharmaceutical method, and less invasive than deep brain stimulation.

Project Summary/abstract Sleep disruption affects 25?40% of Alzheimer's disease (AD) patients with mild to moderate dementia. Disruption in sleep architecture, distinct from obstructive sleep apnea, is a biomarker highly correlated to the early stages of AD and APOE e4 allele risk factors. Sleep sensors measuring body movement (actigraphy) cannot detect the cyclical patterns that shift between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages. Accurate monitoring of sleep architecture requires electroencephalograph (EEG) recordings. Home-based EEG sensors are far from ideal as they are expensive and not comfortable to wear on a daily basis. Large efforts are still needed towards the improvement of electrodes, wireless signal transmission, and overall cost-effectiveness. Being low cost and easy to use are essential factors necessary for public acceptance of large-scale measurements with millions of users. The goal of this proposal is to develop an optimized, cost-effective, EEG sensor for home use. We propose an integrated approach to achieve cost-effectiveness and reliability by combining novel electrodes, amplifiers, Bluetooth transmission, and the battery on a single soft headband. SA1. Optimized EEG electrodes for reliable recording. Electrode design is the most critical element for high signal quality and a friendly user experience. We will test a number of novel self-adhesive electrodes inspired by gecko feet and grasshopper legs. These novel surfaces may bring large lateral grip force to stabilize the electrode over the skin, which may greatly reduce the artifact caused by relative movement between the skin and the electrode. SA2. Platform independent wireless transmission and data storage. We propose platform-independent Bluetooth wireless signal transmission to existing cellphones. As cellphones are widely used in the older and middle- aged population, recording and storage of EEG data on user's own cellphone is a cost-effective solution for large-scale use. We will use conventional voice recording APPs in every cellphone for data storage and a Bluetooth microphone for transmitting data from the headband to the user's cellphone. Such devices can be directly paired with cellphones running different operating systems without installation. Transmitting EEG through a voice band will be achieved with a frequency modulation circuit, and the EEG signals will be recovered from the voice file by a software demodulation program. Large scale measurement of sleep disruption depends on cost-effective solutions. Our project will not only contribute to the early detection/early intervention of AD pathology, but also serve as a research tool for researchers to collect large amounts of data to define early biomarkers of AD specific phenotypes.