September 19: Kalanit Grill-Spector, Ph.D., Stanford University
DATE CHANGE: This seminar will be held on MONDAY, September 19
Associate Professor, Department of Psychology, Neuroscience Institute
"Population Receptive Fields in the Human Ventral Stream and Their Role in Face Perception"
Faculty Host: Alessandra Angelucci, Ophthalmology & Visual Sciences
Student Host: Maryam Bijanzadeh
Research Summary: The cortical system for processing faces is a model system for studying the functional neuroanatomy of ventral temporal cortex and its role in perception because the functional organization of the cortical face system is well understood and activations in ventral face-selective regions are causally related to face perception. Here, I will describe recent results from our research elucidating the computations performed by population receptive field (pRFs) in the cortical system for face perception. In contrast to predictions of classical theories, recent data from my lab reveals that computations in face-selective regions in human ventral temporal cortex can be characterized with a computational pRF model, which predicts the location and spatial extent of the visual field that is processed by the neural population in a voxel. Our research characterizes pRF properties of ventral stream face-selective regions revealing three main findings. First, pRFs illustrate a hierarchical organization within the face system, whereby pRFs become larger and more foveal across the ventral hierarchy. Second, attention to faces modulates pRFs in face-selective regions, consequently enhancing the representation of faces in the peripheral visual field where visual acuity is the lowest. Third, our research shows that pRF properties in face-selective regions are behaviorally relevant. We find that face perception abilities are correlated with pRF properties: participants with larger pRFs perform better in face recognition than participants with smaller pRFs. These data suggest that computations performed by pRFs in face-selective regions may form a neural basis for holistic processing necessary for face recognition. Overall, these data highlight the importance of elucidating computational properties of neural populations in ventral temporal cortex as they offer a new mechanistic understanding of high-level visual processes such as face perception. This work has been done in collaboration with Kevin Weiner, Kendrick Kay, Nathan Witthoft & Jesse Gomez.
October 18: John P. Welsh, Ph.D., University of Washington School of Medicine
Professor, Department of Pediatrics
"Central Rhythmogenesis and Behavior"
Faculty Host: David Krizaj, Ophthalmology & Visual Sciences
Student Host: Patrick Parker
Research Summary: Work in my lab has focused on the neuronal mechanisms that produce electrical oscillations in ensembles of neurons and the implications of those mechanisms for behavior, including motricity and associative learning. We have studied the inferior olive, an autonomously rhythmogenic structure that plays a critical role in establishing spatio-temporal patterns of activity in the cerebellum. We established that oscillations in membrane potential that are subthreshold for spiking emerge from resonant interactions between neurons that are supported weak but prevalent electrical coupling. Weak and prevalent electrical coupling serves as a substrate upon which plasticity processes triggered by chemical synaptic input can modify the strength and breadth of neuronal rhythmicity to modulate timing processes in the brain. Our biophysical experiments have motivated a stream of translational studies using classical eyeblink conditioning in young children with autism that has revealed heterogeneity in brain timing related to autism diagnosis. I will discuss the implications of the work for early detection of developmental disorders in order to maximize the opportunities and benefits of early intervention.
November 15: Oleg Butovsky, Ph.D., Harvard Medical School
Professor, Department of Neuroscience
"Mechanisms of Microglia Regulation in Neurodegeneration"
Faculty Host: Monica Vetter, Neurobiology & Anatomy
Student Host: Sarah Anderson
Research Summary: My research interests focus on basic fundamental questions of microglia biology and developing novel microglia-targeting therapies. One of the important new areas in neuroimmunology is the emerging field of the innate immune system and the interface between resident microglia and the peripheral innate immune system. One of the most ambitious projects of my studies and a major problem of the last century is to identify unique signature of microglia. We have identified a unique microglial signature in both rodents and human that allowed us to genetically and molecularly characterize resident microglia in the CNS and distinguish them from peripheral monocytes/macrophages that infiltrate the brain. Our novel tools and therapeutic approaches are broadly applicable to many neurological diseases such as Multiple sclerosis, Amyotrophic lateral sclerosis and Alzheimer's disease that currently lack available therapy.
January 17: Baljit S. Khakh, Ph.D., David Geffen School of Medicine, UCLA
Professor, Departments of Physiology and Neurobiology
"Astrocyte Roles in Neural Circuits in situ and in vivo"
Faculty Host: K.C. Brennan, Neurology
Student Host: Patrick Parker
Research Summary: Astrocytes are a type of brain glial cell. In 1899 Cajal showed the close spatial relationships between astrocytes and neurons in the brain. Subsequent anatomical work a century later showed that a single hippocampal astrocyte can form connections with ~100,000 synapses and that individual astrocytes are tiled in non-overlapping domains. Moreover, astrocytes are known to release signaling molecules through a variety of mechanisms. These studies raise the possibility that astrocytes may regulate neuronal function. A major project in the lab seeks to investigate this possibility in the context of neuronal networks in the healthy brain as well as for models of Huntington's disease.
February 21: John Huguenard, Ph.D., Stanford University School of Medicine
Professor, Department of Neurology & Neurological Sciences
"The Next Wave of Optogenetics for Use in Real Time Control of Seizures"
Faculty Host: K.C. Brennan, Neurology
Student Host: Pratyush Suryavanshi
Research Summary: Neurons are heterogeneous in terms of the electrical responsiveness, with at one extreme, some interneurons are simple integrators of synaptic input to generate spike output, while others have extended firing rate capabilities, including modal firing rates, such as thalamic relay neurons which exhibit both burst firing and tonic firing modes. In the latter, burst firing is associated with certain behavior states such as sleeping and in the extreme, epilepsy. We used novel optogenetic approaches to switch the firing mode of thalamic relay neurons either into or out of burst mode to show the sufficiency and necessity of thalamic population burst mode firing in generation of absence seizures in the thalamocortical network. These findings have important therapeutic implications in that drugs that target the voltage gated calcium channels responsible for burst firing should be effective anti-epileptic compounds.
March 21: J. John Mann, M.D., Columbia University
Paul Janssen Professor of Translational Neuroscience, Departments of Psychiatry and Radiology
"Neurotransmitter Imaging in Mood Disorders: Separating Cause from Consequence"
Faculty Host: Hilary Coon, Psychiatry
Student Host: Nancy William
Research Summary: Studies of the neurobiology of mood disorders need to distinguish between findings related to the causal endophenotype and brain changes in response to stress that include homeostatic responses or damage due to excessive levels of cortisol or glutamate and finally treatment effects. A series of brain imaging studies of the serotonin neurotransmitter system will be described that reveal an endophenotype that is present between episodes of major depression and transmitted in families. This brain endophenotype is a possible cause and also a major target of selective serotonin inhibitors in terms of antidepressant action. This body of research illustrates an approach for understanding causal mechanisms in mood disorders and has potential for optimizing treatment and prevention.
April 18: Peter W. Kalivas, Ph.D., Medical University of South Carolina
Distinguished Professor and Chair, Department of Neuroscience
"Using the Neurobiology of Will Power to Treat Drug Addiction"
Faculty Host: Kristen Keefe, Pharmacology & Toxicology
Student Host: Anne Gibson
Research Summary: The brain circuitry whereby drug associated stimuli promote relapse is characterized and prefrontal glutamate projections into the nucleus accumbens are a primary component. I will discuss how these projections are altered in drug addicted animals, and how cue-induced relapse produces transient synaptic changes in glutamatergic synapses in this projection that mediate the uncontrollable desire to use drug. These transient changes involve all aspects of the tetrapartite glutamate synapses, including not only pre- and post-synaptic transmission, but also astroglia and the extracellular matrix. My presentation will culminate in clinical trials with N-acetylcysteine that restores normal synaptic communication in the prefrontal to accumbens projection and reduces drug relapse.