Next Seminar

10/20
Xiaoqin Wang, BME, Neuroscience and Otolaryngology, Johns Hopkins Univ.
Marmoset as a translational model for studying brain mechanisms underlying electrical hearing through cochlear implant

The common marmoset (Callithrix jacchus) has emerged in recent years as a promising model system for studying neural basis of hearing and vocal communication. Marmosets have a rich repertoire of communication calls and a similar hearing range as humans. In the past 20 years, my laboratory has pioneered a number of techniques for studying behaviors and neural activity in awake and behaving marmosets. Recently, we have developed a cochlear implant (CI) model in marmosets to study questions related to brain mechanisms responsible for electrical hearing. By comparing single neuron responses to acoustic and CI stimulation, we discovered that CI stimulation was surprisingly ineffective at activating neurons in auditory cortex, particularly in the hemisphere ipsilateral to the implant. Further analyses revealed that the CI-nonresponsive neurons were narrowly tuned to frequency and sound level; such neurons likely play a role in perceptual behaviors requiring fine frequency and level discrimination, tasks that CI users find especially challenging. These findings suggest potential deficits in central auditory processing of CI stimulation, and provide important insights into factors responsible for poor CI user performance in a wide range of perceptual tasks.


All are welcome, (attendance required for graduate students). Lunch is provided.

Contact: Prof. Qi Wang.

Day/Time/Location: Fridays 11-12 noon, 633 Mudd Building (unless otherwise noted)

Fall 2017 Departmental Seminar Schedule

  •  
    9/15
    Joshua C. Brumberg, Ph.D., Professor of Psychology and Biology, Queens College and The Graduate Center, CUNY
    Sensory Experience and the Shaping of Cortical Circuits

    Sensory experience early in development has profound and lasting impacts on the development of neocortical circuits. Using the mouse whisker-to-barrel system we have examined the influence of sensory activity on neuronal and glial components of the barrel cortex with a special emphasis on the perineuronal net (a neuron specific component of the extra cellular matrix). Sensory deprivation induced by whisker trimming from birth increases dendritic complexity, alters dendritic spines and decreases a specific component of the extracellular matrix suggesting a possible substrate for changes in receptive field properties of neurons in deprived cortex. Subsequent, physiological studies define the role of the perineuronal net in shaping neuronal activity.

  •  
    9/22
    Garrett Stanley, BME, Georgia Tech
    Reading & Writing the Neural Code: Challenges in Neuroengineering

    The external world is represented in the brain as spatiotemporal patterns of electrical activity. Sensory signals, such as light, sound and touch are transduced at the periphery and subsequently transformed by various stages of neural circuitry, resulting in increasingly abstract representations through the sensory pathways of the brain. It is these representations that ultimately give rise to sensory perception. Deciphering the messages conveyed in the representations is often referred to as “reading the neural code”. True understanding of the neural code requires knowledge of not only the representation of the external world at one particular stage of the neural pathway, but ultimately how sensory information is communicated from the periphery to successive downstream brain structures. In contrast, prosthetic devices designed to augment or replace sensory function rely on the principle of artificially activating neural circuits to induce a desired perception, which we might refer to as “writing the neural code”. This requires not only significant challenges in biomaterials and interfaces, but also in knowing precisely what to tell the brain to do. Taken together, an understanding of these complexities and others is critical for understanding how information about the outside world is acquired and communicated to downstream brain structures, in relating spatiotemporal patterns of neural activity to sensory perception, and for the development of engineered devices for replacing or augmenting sensory function lost to trauma or disease.

  •  
    9/29
    Ashutosh Agrawal, BME, University of Miami
    Resealable, Optically accessible, PDMS-free Fluidic Platforms for Organs on Chips

    We report the design and fabrication of robust fluidic platforms for culturing and interrogating 3D organoid cultures. The optimized design of convective fluid flows, use of bio-inert and non-absorbent materials, reversible assembly of the platform, manual access for loading and unloading of cultures, and straightforward integration with commercial imaging and fluid handling systems are major improvements over conventional PDMS-based low volume microfluidics.

    The platform has been used for perfusion interrogation of human pancreatic islets, and engineered spheroid cultures that mimic the metastatic niche of the human bone marrow. Islets were tested for dynamic secretion of hormones, concomitant live-cell imaging, and optogenetic stimulation of genetically engineered islets. The efforts to evaluate ex vivo function of islets are informing the clinical efforts to transplant human islets in Type 1 Diabetic patients.

    The platform is also being tested for long term culture of spheroids composed of primary human cells of the bone marrow along with vascular cells and supporting pericytes. The efforts to recreate the metastatic niche are enabling in vitro maintenance and propagation of circulating tumor cells derived from the blood of breast and prostate cancer patients, as tools for enabling precision oncology.

  •  
    10/6
    Chang H. Lee, Department of Craniofacial Engineering, School of Dental Medicine, CUMC
    In Situ Regeneration of Dense Connective Tissues by Endogenous Stem/Progenitor Cells

    Stem cell-based therapies have received tremendous attention in the hope of regenerating defective tissues or organs. Current stem cell-based regenerative therapies predominantly involve isolation and sorting, ex vivo culture-expansion, and transplantation with or without directed differentiation. Despite being a valid approach, cell transplantation has encountered crucial barriers in therapeutic translation, including immune rejection, pathogen transmission, potential tumorigenesis, issues associated with packaging, storage, and shipping, and difficulties in clinical adoption and regulatory approval. Accordingly, alternative therapeutic approach has been suggested by recent works showing the existence of endogenous stem cells with regenerative capacity. We have reported promising findings that healing, repair or regeneration can be achieved by recruiting, activating, and/or differentiating either tissue resident or circulating stem cells, instead of stem cell transplantation necessitating ex vivo manipulation. This seminar will cover our research progress for regeneration of dense connective tissues including knee meniscus and tendon by harnessing endogenous stem/progenitor cells. The potential of ‘in situ regeneration’ as a simple and straightforward strategy for regenerative medicine will also be discussed.

  •  
    10/13
    Krish Sathian, Neurology, Rehabilitation Medicine and Psychology, Emory University
    Is Modularity Dead? Insights from the Tactile Sense

    Visual cortical areas are routinely recruited, in a taskspecific manner, for processing those aspects of touch for which they are specialized in vision. This reflects flexible access of object representations through vision and touch via both sensory input and multiple types of imagery. Sensorimotor areas are also recruited during comprehension of metaphor. Such findings challenge modular conceptualizations of brain function and highlight the importance of work to understand how perception and cognition arise from network interactions between neuronal populations specialized for different computational processes.

  •  
    10/20
    Xiaoqin Wang, BME, Neuroscience and Otolaryngology, Johns Hopkins Univ.
    Marmoset as a translational model for studying brain mechanisms underlying electrical hearing through cochlear implant

    The common marmoset (Callithrix jacchus) has emerged in recent years as a promising model system for studying neural basis of hearing and vocal communication. Marmosets have a rich repertoire of communication calls and a similar hearing range as humans. In the past 20 years, my laboratory has pioneered a number of techniques for studying behaviors and neural activity in awake and behaving marmosets. Recently, we have developed a cochlear implant (CI) model in marmosets to study questions related to brain mechanisms responsible for electrical hearing. By comparing single neuron responses to acoustic and CI stimulation, we discovered that CI stimulation was surprisingly ineffective at activating neurons in auditory cortex, particularly in the hemisphere ipsilateral to the implant. Further analyses revealed that the CI-nonresponsive neurons were narrowly tuned to frequency and sound level; such neurons likely play a role in perceptual behaviors requiring fine frequency and level discrimination, tasks that CI users find especially challenging. These findings suggest potential deficits in central auditory processing of CI stimulation, and provide important insights into factors responsible for poor CI user performance in a wide range of perceptual tasks.

  •  
    10/27
    Eve Donnelly, Materials Science and Engineering, Cornell University
    Multiscale mechanical and compositional characterization of bone tissue in health and disease

    Bone tissue plays a critical structural role in the skeleton, yet the underlying microstructure-mechanical property relationships are incompletely understood, in part due to the complex hierarchical structure of the tissue. We examine biopsies from human patients to understand disease- and treatment-induced changes in bone composition and their relationship to osteoporotic fracture incidence and bone tissue from animal models to elucidate fundamental structure-property relationships. To understand the relationships among bone turnover, material properties, and fracture incidence, we use vibrational spectroscopic imaging to characterize changes in the composition of osteoporotic human bone with antiresorptive pharmaceutical treatment. This work informs an emerging understanding of the pathophysiology of bisphosphonate-associated atypical fractures debated in the medical literature and reported in the popular press. Elucidation of microstructure-property relationships in normal and pathologic bone generates insights into the contribution of tissue material properties to skeletal integrity and the processes by which the load-bearing capability of bone is degraded in pathologic tissue.

  •  
    11/3
    TBD
    Title and Abstract TBA

    Title and Abstract TBA

  •  
    11/10
    Eve Donnelly, Cornell University, Ithaca, NY, USA

    Multiscale mechanical and compositional characterization of bone tissue in health and disease

    Bone tissue plays a critical structural role in the skeleton, yet the underlying microstructure-mechanical property relationships are incompletely understood, in part due to the complex hierarchical structure of the tissue. We examine biopsies from human patients to understand disease- and treatment-induced changes in bone composition and their relationship to osteoporotic fracture incidence and bone tissue from animal models to elucidate fundamental structure-property relationships. To understand the relationships among bone turnover, material properties, and fracture incidence, we use vibrational spectroscopic imaging to characterize changes in the composition of osteoporotic human bone with antiresorptive pharmaceutical treatment. This work informs an emerging understanding of the pathophysiology of bisphosphonate-associated atypical fractures debated in the medical literature and reported in the popular press. Elucidation of microstructure-property relationships in normal and pathologic bone generates insights into the contribution of tissue material properties to skeletal integrity and the processes by which the load-bearing capability of bone is degraded in pathologic tissue.

  •  
    11/17
    Michael Murrell, BME, Yale University (joint with Mech.E)
    From Active Liquid Crystals to De-wetting Liquid Droplets

    Living cells generate and transmit mechanical forces over diverse time-scales and length-scales to determine the dynamics of cell and tissue shape during both homeostatic and pathological processes, from early embryonic development to cancer metastasis. These forces arise from the cell cytoskeleton, a scaffolding network of entangled protein polymers driven out-of-equilibrium by enzymes that convert chemical energy into mechanical work. However, how molecular interactions within the cytoskeleton lead to the accumulation of mechanical stresses that determine the dynamics of cell shape is unknown. Furthermore, how cellular interactions are subsequently modulated to determine the shape of the tissue is also unclear. To bridge these scales, our group in collaboration with others, uses a combination of experimental, computational and theoretical approaches. On the molecular scale, we use active nematic liquid crystals as a framework to understand how mechanical stresses are produced and transmitted within the cell cytoskeleton. On the scale of cells and tissues, we abstract these stresses to surface tension in a liquid droplet and draw analogies between the dynamics of droplet wetting (and dewetting) and the shape dynamics of cells and simple tissues. Together, we attempt to develop comprehensive description for how cytoskeletal stresses translate to the physical behaviors of cells and tissues with significant phenotypic outcomes such as cancer metastasis.

  •  
    12/1
    J. Ruben Morones-Ramirez, Chemical Engineering, Universidad Autónoma de Nuevo León
    Title and Abstract TBA

    Title and Abstract TBA

  •  
    12/8
    Marius Linguraru, Depts. of Radiology and of Pediatrics, George Washington U.
    Title and Abstract TBA

    Title and Abstract TBA

 


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