Philip H. Smith, PhD - US grants

The inferior colliculus (IC) serves as a major convergent site of auditory information for lower brainstem auditory structures and as such is of primary importance in the integration and subsequent transmission of auditory information. Recent anatomical, physiological and pharmacological investigations have begun to unravel the complex interactions taking place in this structure yet the circuitry is still not well understood. A number of studies have shown that the IC not only plays a major role in normal auditory function but also is of critical importance in the propagation and initiation of sensory evoked audiogenic seizures. A number of genetic mutants exist in rodents, in particular the genetically epilepsy prone rat (GEPR), that display seizure behavior in response to intense auditory stimuli which may be linked to functional abnormalities in the IC and which may serve as an animal model for reflex or primary generalized epilepsies. Indirect evidence indicates that many of the same potential mechanisms responsible for epileptic neural behavior at the cortical and hippocampal levels may be active in the inferior colliculus. This study will primarily utilize the in vitro brain slice technique to investigate the colliculus. The intent is to begin a characterization of the intrinsic and synaptic features of cells in various specific regions of the colliculus. An effort will be made, at the intracellular level, to look at specific synaptic events elicited by activation of input pathways the potential transmitters used by these pathways and the intrinsic features of the cells that could help to shape the response to these inputs. Records from cells in normal IC slices in altered neural transmission environments and from cells in slices from GEPR mutant will be analyzed to determine which cell types are capable of abnormal epileptic function, whether these functions can occur spontaneously in mutant slices and what the underlying mechanisms/abnormalities are causing this activity. Finally in the in vivo preparation the presumed output pathway of the abnormal seizure activity from the IC will be more thoroughly characterized.

Auditory information is first processed in the brainstem by neurons in the cochlear nuclear complex, containing several cell types. Output axons of many of these cells project forward in a major pathway forming a structure called the trapezoid body (from its shape). These axons then terminate on neurons at the next higher level called the superior olivary complex. We do not yet understand how the signals from the cochlear nuclei are related to higher aspects of auditory function, such as sound localization or startle responses, which are handled by neurons in the superior olive. This project will determine the signalling and target destinations of the these trapezoid body axons. Intracellular recordings will be used to physiologically characterize the response properties of single axons that extend into the trapezoid body, and intracellular dye filling then will be used to trace the pathways, from cells of origin to target cells, within the cat brainstem. Light and electron microscopy will provide details of location of terminals for each cell, and of detailed morphology of the synaptic endings, to morphologically characterize cell types. This classification then will be correlated to the observed functional responses of these cells. This work will provide a unique integration of information in the central auditory pathway; it will clarify what kinds of signal processing occur at the important level connecting the cochlear nuclei to the superior olivary complex, and will clarify the functional significance of morphological cell classification in the cochlear nucleus.

This research is directed towards understanding how auditory information is processed and coded by nerve cells in the cochlear nucleus, a portion of the brain pathways that are involved in hearing. The auditory environment provides a rich and complex array of information from a myriad of sounds from different sources. Some of this information, such as speech sounds, is highly relevant to us, while much of it is disregarded as extraneous noise. The auditory central nervous system converts auditory information into neural signals which are later analyzed at different levels in the brain. In order to understand how auditory information processing occurs, this research is being conducted to determine what aspects of auditory information are being coded by individual types of nerve cells in the cochlear nucleus as well as where cochlear neurons send this information in the brain. The activity of single nerve cells is recorded and analyzed using microelectrodes inserted into single neurons, the response to auditory stimulation is recorded, and a dye is injected into the nerve cell in order to identify it using histological techniques. By locating and analyzing this labelled neuron using both light and electron microscopy, it is possible to answer a number of basic questions which include: (1) Do certain types of cells encode specific parts of the auditory signal? (2) What part of the brain do these cells relay information to? (3) What are the interactions between individual types of neurons? These studies are essential to understanding how such a complex sensory system provides us with the experience of hearing that is so crucial to perception and cognitive experience.

The medial superior olive (MSO) is presumed to play a major role in sound localization. It is the initial site in the auditory CNS where sound-evoked activity from both ears converges on and excites individual neurons. It has been proposed that cells located here can, by comparing these binaural inputs, extract and respond to important temporal cues available in this incoming signal. These temporal cues change as a sound changes location in azimuthal space and it has also been proposed that different members of the MSO cell population respond optimally to only those binaural cues generated from a particular point(s) in this space. Thus, important aspects of the "map" of external space are extracted and neurally encoded in a population of selectively sensitive neurons. Unfortunately, the great difficulty in recording from positively identified MSO cells, using standard in vivo extracellular and intracellular methods, has hindered verification of such hypotheses. We intend to do both in vitro intracellular recordings from MSO cells (and from cells in periolivary nuclei inputting to MSO) and in vivo intraaxonal recordings from MSO axons using high impedance Neurobiotin-filled glass electrodes. In vitro, we will characterize intrinsic membrane features of - and synaptic inputs to - MSO cells to distinguish aspects that could be important in accomplishing the localization tasks described above. We will then study the anatomical aspects of the labeled cell to determine local circuitry and if certain cell subtypes show unique physiology. In vivo, we will record intraaxonally from axons of MSO cells, as they approach inferior colliculus in lateral lemniscus, and characterize their responses to monaural and binaural stimuli. We will subsequently analyze 1) the labeled axon, at light and electron microscopic levels, to determine the influence of MSO cells on other auditory nuclei and 2) the location and type of the backfilled MSO cell body to determine 1) cell type 2) its synaptic input 3) whether different cell types encode different auditory features and 4) if they are arranged in any sort of order (map) based on such features (e.g. those features used to encode location in space).

The auditory cortex is a complex layered structure whose circuitry is composed of a variety of cell types and their interconnections. Auditory information form thalamus terminates in layers III and IV and extracellular recordings from cells there reveal a diverse set of responses to auditory stimuli. The long-term objective of this project are to understand how cells in these layers integrate and process the most basic features of this ascending information and where they subsequently send it. The basic approach involves using single cell intracellular recording methods to record from and characterize the sub- and suprathreshold responses of cells, either in vivo or in the brain slice, followed by labeling of the cells for subsequent anatomical study. In vivo we will use simple auditory stimuli to test 1) whether the cells are excited by stimulation of either ear ("EE") or excited by the contralateral ear and inhibited by simultaneous stimulation of the ipsilateral ear ("EI") 2) the monotonic (progressive increase in spike output with increasing SPL from threshold to saturation) or non- monotonic (maximum spike output at intermediate SPL levels that drops off at higher and lower intensities) nature of the cells and 3) whether cells are sensitive to either the duration of a single stimulus or the duration of the interval between two stimuli. Such an approach determines 1) if the set of cells that display a unique response to a particular auditory signal is a specific anatomical class, 2) what synaptic inputs are shaping these responses? Are both excitatory and inhibitory events involved or is the cell simply mimicking a suprathreshold ascending input? 3) whether the cell's intrinsic membrane features are important in letting the cell respond optimally to it's chosen stimuli and 4) what the cell does with its information, i.e. what are the projection patterns of the axon? In the brain slice we will record from the same populations of cells and, because of the nature of slice recording, be able to more closely study the physiology and pharmacology of the synaptic inputs and the biophysical properties of the cells. These results will begin to lay a structural /functional framework on which to build an understanding for higher auditory cortical function.

DESCRIPTION (provided by applicant): We have shown that both excitatory (glutamatergic) and inhibitory (GABAergic) cells in the inferior colliculus (IC) project to and synapse on cells in the auditory thalamus (MGB). Our long-term objective is to understand the role of these excitatory and inhibitory IC inputs in shaping the responses of cells in the MGB. The sensory thalamus was once considered to be a simple relay center whose cells received ascending sensory information and passively sent it on to the cortex. Over the past 3 decades it has become apparent that this is not the case and that thalamic cells can function in two different response modes, "burst" and "tonic" which depend on the activation or inactivation of a voltage sensitive calcium conductance. Depending upon which mode the cell is in drastically alters their spike response to ascending excitatory synaptic messages and thus changes their input to the cortex in response to sensory stimuli (see Sherman, '01). In addition, the synchronized response of populations of thalamic cells while in the burst mode are believed to be responsible for the EEG oscillations seen during slow wave sleep and during some types of generalized epileptic seizures (see McCormick and Bal, '97). Recent evidence primarily from our lab has indicated that an added level of complexity is found in the auditory thalamus. Here 1) in contrast to other sensory thalamic nuclei, the ascending synaptic information is in the form of both excitation and inhibition 2) this ascending sensory input may be influencing auditory thalamic cells that do not necessarily display the two different response modes and 3) this ascending sensory input from the IC to some cells in the MGB may show synaptic plasticity. Thus, models of thalamic function that have been created using other sensory systems may not be applicable to the auditory thalamus. In order to better understand the similarities and/or differences in auditory thalamic processing of sensory information it is important to determine 1) how and when the excitatory and inhibitory IC inputs are active and thus influencing thalamic neurons 2) whether these inputs are influencing cells that can respond either in one mode or two and 3) whether stimulation of the collicular inputs can generate synaptic plasticity (LTP) in certain MGB cells and what mechanism of potentiation is involved. The proposed experiments will help to answer these questions.

DESCRIPTION (provided by applicant): Illicit drug use (IDU) and intimate partner violence (IPV) are important and interrelated public health issues. There is strong evidence for a cross-sectional association between IDU and IPV, but there is a shortage of research testing a longitudinal association and potential mediation/moderation effects. Leonard (1993) proposed a heuristic model of the association between substance use and IPV, whereby distal risk factors (e.g. antisocial personality, hostility) in conjunction with proximal risk factors (e.g. situational cues, psychopharmacological effects of substance use), increase the likelihood of violent events. Experimental evidence that the psychopharmacological effects of different illicit drug types (i.e. cannabis, cocaine) elicit aggressive behavior is equivocal, suggesting that it is important to research more distal effects of IDU. Previous research has speculated that IDU may increase verbal conflict in relationships, which in turn can result in a greater likelihood of IPV. A host of other variables (e.g., hostility, avoidance coping, life stress, race, antisocial personality, alcohol use and partner IDU) have been suggested as possible moderators of an association; however, there is a lack of research that directly tests these effects. This proposed study will use secondary data analysis to test a longitudinal association between IDU and IPV, and mediation\ moderation effects. To do so, data will be analyzed from the Adult Development Study (ADS), a longitudinal survey of newly married couples in Buffalo, NY. Research on IPV among newly married couples is particularly important because rates of IPV are high in this population. Couples were recruited for the ADS as they applied for their marriage license, and subsequently followed-up at their first, second, fourth, seventh and ninth wedding anniversaries. It will be important to limit the sample to the early years of marriage while retaining enough time-points to conduct meaningful longitudinal analyses; thus, data will be analyzed from the first four waves only (i.e. baseline through 4th anniversary). ADS data were collected from both spouses of 634 couples, allowing this proposed study to examine the potentially important effect of partner behaviors on relationship violence. It will be important to first examine consistency with previous findings; thus, the first specific aim of this proposed study is to test a cross-sectional relation between IDU and IPV. The second specific aim is to examine the longitudinal association between husband/wife IDU and husband/wife IPV in newly married couples. The third specific aim is to test possible mediators/moderators of an IPV-IDU association, including: a) the moderation effect of partner IDU, b) the mediation effect of verbal conflict, and c) the moderation effect of hostility, avoidance coping, life stress, antisocial personality, alcohol use, and race/ethnicity. Descriptive statistics, chi-square tests, t-tests and logistic regression will be used to examine the prevalence of IDU and IPV in the sample, and to test cross-sectional relations between IDU and IPV. Multi Level Modeling will be used to test for a longitudinal relation between IDU and IPV, as well as mediation and moderation effects.

DESCRIPTION (provided by applicant): Binaural hearing plays a key role in the development of speech and language perception because the normal development of the brain's binaural circuitry requires the proper activation of these inputs. Besides being instrumental in the development of normal circuitry, recent evaluations of bilateral cochlear implant patients indicates that their newly acquired binaural inputs provide some improvements in their abilities to localize sound and to understand speech in quiet and in the presence of noise. Thus, although we are able to process complex auditory stimuli like speech with only one ear, binaural cues provide additional critical information. Unfortunately it is only some improvement for some of these bilateral cochlear implant patients. We are still in the infancy stages of knowing how to optimally present such stimuli to the hard of hearing or deaf via hearing aids or cochlear implants. One of the major impediments on this path is that we still do not have a complete understanding the basic brainstem circuitry involved in binaural processing and the mechanisms used by this circuitry to extract the critical auditory cues. The medial superior olive (MSO) is a brainstem auditory nucleus and the first binaural site in the auditory pathway where major inputs activated by the two ears converge. It is by far the most prominent of the auditory brainstem nuclei in the human superior olivary complex. Interestingly, virtually all children with autistic spectral disorder (ASD) have auditory related dysfunction and the MSO is the most severely and consistently malformed brainstem nucleus in the autistic brain. All of these observations would indicate that a more thorough understanding of MSO structure and function is critical if we are to design appropriate methods of activating this nucleus under compromised conditions. Such efforts in experiments using animals with auditory brainstems similar to humans have been hampered by several features that make it extremely difficult to access and record from cells in the MSO. We have perfected methods that bypass these unfavorable features of the nucleus and will allow us to unequivocally evaluate the anatomical and physiological features of MSO cells that are vital in their binaural mission. The method involves recording the responses of these cells to auditory stimulation not from their cell bodies but remotely from their axons at some distance from the nucleus. After determining the response features to auditory stimuli presented to one or both ears we can inject a mobile dye (Neurobiotin) into the individual axon which fills the entire cell body, dendritic tree and axon collateral field. This gives us the opportunity to evaluate the important anatomical features of these physiologically characterized cells at the light and electron microscopic level as well. It is our sincere belief that the experiments proposed here will provide critical information that will advance our understanding of hearing mechanisms in the normal brain and how to better facilitate hearing in the aged and damaged brain.

? DESCRIPTION (provided by applicant): These P20 applications describe the development of a collaborative theme-specific partnership between City College of New York, and Memorial Sloan Kettering Cancer Center. This collaboration is called the TREND Partnership: Translational Research Education and Training to Eliminate Tobacco Disparities. The TREND Partnership builds on an existing, mutually beneficial, and evolving partnership between two exceptional institutions with unique capacities. The goal for this planning grant application is to develop the coordinated capacity within and between our institutions to support collaborative research, research training, and education efforts aimed at reducing tobacco-related cancer health disparities. We have three primary objectives: 1) To provide funding, mentoring, and support for two CCNY/MSK collaborative translational tobacco-related disparities Pilot Research Projects for Early Stage Investigators. These projects will obtain preliminary data that will lead directly o submission of competitive peer-reviewed funding proposals. 2) To provide translational cells to society tobacco-related disparities research training for CCNY students and MSK Research Fellows with broad exposure to relevant scientific domains. We will establish: a) four research training positions at CCNY with appropriate CCNY/MSK faculty mentors and tobacco disparities research project placements, and b) a series of CCNY/MSK shared training activities focused on the specific research topics and skills needed to examine and address tobacco disparities. 3) To augment CCNY clinical program curricula to include knowledge and competencies about tobacco use and dependence, tobacco-related disparities, and the evidence-based treatment of tobacco dependence. We will incorporate: a) Knowledge and competencies associated with tobacco and nicotine biochemistry, nicotine addiction, tobacco-related disparities, and tobacco use and dependence treatment as a permanent interdisciplinary, longitudinal thread from the basic to clinical sciences in the BS/MD curriculum; b) Knowledge and competencies associated with tobacco-related disparities and the evidence-based treatment of tobacco dependence as a permanent, required element of the Physician Assistant (PA) curriculum and the Certified Addiction Substance Abuse Counselor (CASAC) curriculum, and d) lessons learned into a competitive R25 grant application to support the development of a tobacco-disparities research Institutional Curriculum Development Project that will provide ongoing research training in and dissemination of tobacco disparities research to the CCNY, MSK, and broader NYC communities. This R25 project will develop and test a model for developing the capacity to address tobacco-related cancer disparities that can be replicated elsewhere. Meeting the TREND Partnership objectives will have a sustained and powerful impact on our shared capacity to conduct cancer disparities research, research training, and education as well as a significant impact on the current knowledge base relative to understanding and addressing tobacco disparities.

? DESCRIPTION (provided by applicant): Women experience significant disparities with regards to smoking cessation, and research has identified key factors underlying poor treatment response including differential response to smoking cessation medications. Despite this knowledge, findings have yet to translate into improved clinical outcomes for smoking cessation, and current guidelines provide little information on sex-based practices. One critical barrier for the translation to clinical practice is the lack of evidence from Phase-IV population-based studies. To date, evidence has exclusively emerged from Phase-III clinical trial data; sex differences in real-world effectiveness of stop smoking medications remain unknown. We will conduct a Phase-IV pharmacoepidemiologic study of sex differences in smoking cessation effectiveness in a U.S. nationally representative sample. [[[E-cigarette use during cessation attempts and associations with quitting will also be examined.]]] Our study will be a secondary analysis of the first wave of the Population Assessment of Tobacco and Health (PATH) study (scheduled to be released in the Fall of 2015), which was initiated and funded by NIDA and the FDA. The study's large sample size (~59,000) and its inclusion of information on medication/e-cigarette use during attempts to stop smoking will present a unique and unprecedented opportunity to address the study's aims. The project will also serve as the foundation for an R01 application for subsequent analyses of longitudinal waves of PATH data. [[[Our primary aim will be to examine sex differences in the real world comparative effectiveness of smoking cessation medications, using both regression and propensity score approaches, and following published guidelines for medication effectiveness studies using secondary data sources.]]] Data from current and former smokers who attempted to quit smoking (either successfully or unsuccessfully) at least once during the 12 months prior to their interview (n~8,215; 4,240 men and 3,975 women) will be analyzed. The investigation will examine the comparative effectiveness of the following medications: nicotine replacement therapy (the patch, oral NRT, nasal spray), varenicline/Chantix, and bupropion/Wellbutrin/Zyban. We will explore whether sex differences in medication effectiveness are moderated by education level, annual income, race/ethnicity, nicotine dependence level, and mental health. [[[We will also explore sex differences in associations between use of e-cigarettes during cessation attempts and likelihood of successful cessation.]]] This study addresses the National Institute on Drug Abuse's (NIDA) call for projects that assess the differential effectiveness of current drug abuse treatments in males and females (PA-14-037: Women & Sex/Gender Differences in Drug and Alcohol/Dependence).

Project Summary T Stellate cells of the ventral cochlear nucleus (VCN) form an important ascending pathway that transmits spectral information from the auditory nerve to numerous auditory nuclei. They innervate the olivocochlear efferents in the ventral nucleus of the trapezoid body, the lateral superior olive, the inferior colliculi and the thalamus. In preliminary experiments we have discovered that groups of T stellate cells within an isofrequency lamina are bidirectionally interconnected through excitatory synaptic connections that can be potentiated. In dual, whole-cell patch-clamp recordings from T stellate cells, firing in a presynaptic cell generally evoked no EPSCs in the postsynaptic cell unless presynaptic firing was paired with postsynaptic depolarization. These findings are exciting for two reasons. First is that the mechanism underlying that potentiation is new and unprecedented. Postsynaptic depolarization increased the probability of recorded EPSCs, a presynaptic function, implicating the involvement of a retrograde messenger. Our preliminary results support the hypothesis that nitric oxide serves as that retrograde signal. Aim 1 is to use intracellular recordings in slices to gain a deeper understanding of the mechanisms that underlie potentiation of connections between T stellate cells and to understand their source and dynamics. We will identify what neurons participate in polysynaptic connections, how synaptic excitation by auditory nerve fibers affects the plasticity of interconnections, examine signaling through the nitric oxide pathway, and measure rates at which potentiation develop and fade. Second is that our discovery reveals a new form of central gain control at the network level. Bidirectional, excitatory interconnections indicate that T stellate cells in an isofrequency lamina form a network and could explain how T stellate cells can sharpen the encoding of spectral peaks. These interconnections could also form synaptic positive feedback loops that lead to hyperexcitability in the face of loss of auditory nerve fibers and the consequent uncoupling of excitation and inhibition. Aim 2 is to use computational neural models to understand the implications of excitatory interconnections between T stellate cells on their encoding of sound. We will implement models that can simulate the response features of single T stellate cells and build an interconnected neural network to understand how network connectivity contributes to potentiation. We will test the hypothesis that excitatory interconnections enhance the encoding of spectral peaks and that inhibition is required to stabilize the network.