2003 — 2005 |
Bartlett, Edward L |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Feature Selectivity of Auditory Thalamus @ Johns Hopkins University
DESCRIPTION (provided by applicant): The overall goal of this study is to discover the representations of acoustic features by medial geniculate body (MGB) neurons in an awake primate. In doing so, we can ascertain how the known cortical representations of these features arise from the MGB representations, given the comparatively large body of knowledge regarding responses of auditory cortex neurons to auditory stimuli. Some deficits observed in humans with dyslexia and schizophrenia have been correlated with abnormalities in the MGB. An understanding of normal MGB responses to stimuli that produce abnormal responses in affected people, such as rapidly changing or multi-frequency stimuli will provide insight into the likely causes of neuronal dysfunction. We will study how sound characteristics are encoded by MGB neurons by recording the neural responses of single neurons in response to auditory stimuli. The recordings will be performed in awake marmosets, which are primates that possess a large repertoire of vocalizations that are used to communicate. Since auditory cortex responses have been studied extensively and are generated largely by integrating inputs from the thalamus, we will use auditory stimuli that have been used for auditory cortex studies, such as repetitive clicks, two-tone complexes, and amplitude-modulated tones. Knowing both thalamic and cortical responses, the ways that MGB inputs are combined to form new auditory cortex response properties are likely to reveal relevant acoustic features used for auditory perception. The specific aims of the study are as follows: 1) we will test the hypothesis that MGB neurons represent temporally modulated stimuli in a manner that is intermediate between that of the inferior colliculus and the auditory cortex, using separate populations of neurons. One population fires discharges that are locked to the repeated stimulus cycles in a synchronized manner and another population responds in a non-stimulus-synchronized manner through increases in discharge rate. 2) We will investigate the spectral context selectivity of MGB neurons. Using two-tone stimuli, we will test the hypothesis that frequencies that are harmonically related to a MGB neuron's best frequency will inhibit the neuron, whereas the two-tone facilitation observed in the auditory cortex will be weak in the MGB. 3) We will test the hypothesis that the contrasting synaptic and anatomic characteristics of two putative populations of IC excitatory inputs will lead to contrasting responses to tone, two-tone, click, filtered noise, and sinusoidally modulated stimuli in vivo. These two groups of contrasting responses will be differently localized within the MGB.
|
0.961 |
2008 — 2011 |
Shi, Riyi (co-PI) [⬀] Rundell, Ann Rickus, Jenna Bartlett, Edward |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Purdue Scholarship Program in Quantitative Physiology
This project is developing a training community for undergraduate and graduate students in the area of quantitative physiology with a focus on academically talented students with demonstrated financial need. In addition to providing financial support for up to forty-eight students annually the project offers community support as well as classroom and experiential learning opportunities in quantitative and experimental aspects of physiology. The intellectual merit of the project lies in its support structures that focus on the academic and career success of students and include vertical mentoring from secondary school through graduate school, curricular guidance, collaborative interdisciplinary training, and community outreach activities. For example, graduate students in the program help to recruit from their previous institutions and undergraduates do the same from their secondary schools. Graduate students along with upper-division undergraduates also serve as mentors for lower-division students. Furthermore, students with complementary backgrounds are paired to promote interdisciplinary study and research. The broader impacts of the project are felt through its emphasis on motivating the pursuit of higher education and mitigating against attrition issues through the different student support activities. Furthermore, the program is preparing students for future employment or further academic training by teaching students to approach problems outside their expertise and work with complementary experts to propose and achieve solutions. The program is also reaching beyond the institution to establish pipelines of financially needy students from secondary school through graduate school.
|
0.915 |
2012 — 2016 |
Bartlett, Edward |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Measurement and Modeling of Central Auditory Processing in Aged Animals
DESCRIPTION (provided by applicant): Auditory deficits are present in a growing population of millions of elderly listeners. A fundamental gap in knowledge is that central auditory representations of the sounds most affected by aging are poorly understood due to limited in vivo measurements and due to a disconnect between the in vivo responses and their cellular neural bases. The long-term goal of this research is to discover how alterations of cellular physiology in the central auditory pathway of aged animals give rise to altered neural representations at the single-neuron, local network and population levels, in order to target hearing maintenance or recovery programs based on mechanistic hypotheses. Given this goal, the objective of this proposal is to link non-invasive envelope-following and frequency-following responses to inferior colliculus (IC) spiking responses and local field potentials (LFPs) in vivo and to biophysical models of IC neurons. Our central hypothesis is that many age-related auditory deficits can be explained by a small number of critical changes in cellular neurophysiology, such as reduced inhibition, whose consequences can be observed in vivo by measuring the activities of small populations of IC neurons or large populations of brainstem and IC neurons in response to appropriate non-speech and speech-like sounds. The rationale for this research is that there have been few attempts to link diagnostic in vivo data to the underlying neural circuitry that generate aberrant responses, which hampers progress towards remedying the deficits. The proposal objective will be addressed by the following aims: Aim 1) Identify the sounds and shared acoustic features that generate aberrant envelope and frequency following responses in aged animals to bridge animal and human auditory assessments. Aim 2) Determine changes in the spiking activities and LFPs of IC neurons during aging and their correspondence to changes in the envelope following responses evoked by the same sounds. Aim 3) Reproduce in vivo IC responses and predict responses to sounds in young and aged animals using detailed biophysical IC models to distinguish between different cellular mechanisms in aging. The expected contribution of the proposed research is to create a clinic to channels knowledge loop wherein non-invasive diagnostic measurements of central auditory activity in animals are linked to in vivo single neuron responses, LFPs and detailed mechanistic models of IC neurons. This contribution is significant because connecting in vivo electrophysiological measurements with their cellular bases creates a powerful framework in which to iteratively identify factors that contribute to age-related central auditory decline and predict rapidly the consequences of potential treatments that affect those factors. The proposed research is innovative because in vivo electrophysiological measurements of clinically and behaviorally relevant sounds taken at the population, local network, and single/multiunit levels are informed and constrained by detailed cellular and synaptic models of the central auditory system, rather than by abstract or anatomically based models. This will provide targets for pharmacologic or behavioral therapy at each level. PUBLIC HEALTH RELEVANCE: The proposed project is relevant to public health because it progresses towards establishing a clear link between non-invasive human and animal auditory neurophysiologic diagnostics and the cellular mechanisms that generate those responses in young and old listeners. Impacts relevant to the NIH's mission will emerge in the form of diagnostic stimuli with the ability to pinpoint specific types of temporal and spectral processing deficits in aging, along with the ability to identify and predict the effects of numerous potential therapeutic targets in vivo based on their cellular modes of action.
|
0.915 |