Spring 2005 Seminar Series in Neuroscience


Tuesday Feb 1, 4-5 pm	Dan Barth, Department of Psychology, University of Colorado, Boulder TITLE: “Fast Electrical Oscillations in Sensory Cortex: Implications for Feature Binding, Modulation, and a New Clock Speed for Neural Computation” Abstract: One of the greatest challenges facing cognitive neuroscientists is understanding how spatial and temporal patterns of electrical activity in large populations of cortical neurons encode features of objects in the environment. Recent studies of gamma frequency (40 Hz) and faster oscillatory (FO; >200 Hz) electrical activity in sensory cortex of many species, including humans, have suggested that tightly synchronized oscillations may play a major role in coordinating interactions between regions of sensory cortex at microscopic and macroscopic levels. My laboratory has studied fast field potential oscillations in rat sensory cortex using high resolution electrode arrays placed on the cortical surface, combined with extracellular and intracellular microelectrode recordings of single neurons and small groups of neurons, with the objective of better understanding their functional significance and their underlying neural generators. In this seminar I will present evidence that gamma oscillations serve to precisely coordinate excitability among cortical columns as a prerequisite to fast inter-columnar processing and thus bind together feature within sensory maps. However, inter-columnar processing is effected by FO, which serve as a mechanism for rapid spatio-temporal integration with sub-millisecond accuracy.
Tuesday Feb 15, 4-5 pm	Tim Curran, Dept of Psychology & Institute of Cognitive Sciences, CU-Boulder TITLE: “Human learning and memory: Perspectives from event-related brain potentials (ERPs)” Abstract: People learn and remember things in a variety of different ways that tap into several distinct neurocognitive processes. A shopper trying to remember the contents of a grocery list mistakenly left at home relies on memory processes that are much different from those of a bird watcher who, based on years of experience, recognizes a scarlet tanger in flight. Our laboratory uses human, scalp-recorded, event-related brain potentials (ERPs) to try to understand the characteristics of these memory processes. We have found that expertise in visual object recognition (e.g., bird watchers) leads to changes in early (less that 200 milliseconds) visual cortical processes. Memory for more recently (and less frequently) encountered information (e.g., a grocery list), on the other hand, depends on later-occurring (400+ milliseconds) processes that appear to be dependent upon the hippocampus. This talk will summarize some of our recent research intended to further our understanding of these learning and memory processes.
Tuesday Mar 1, 4-5 pm	Patricia Reuter-Lorenz, University of Michigan TITLE: "New Visions of the Aging Mind and Brain" Abstract: TBA
Tuesday March 15, 4-5 pm	Gregory Quirk, Dept of Physiology, Ponce School of Medicine, Puerto Rico TITLE: "Fear Not! Prefrontal-amygdala interactions in extinction" Abstract: After a traumatic experience, how do we learn to feel safe again? One way to address this is to study extinction of conditioned fear. While it has been known since Pavlov that extinction represents new learning, the past 5 years have seen renewed interest in the neural mechanism of extinction. The amygdala appears to be necessary for the initial learning of extinction, and the medial prefrontal cortex is necessary for consolidation and expression of extinction. Converging data from lesion, unit-recording, microstimulation, and molecular studies in rats suggests that extinction potentiates inputs to the infralimbic mPFC, which reduces fear by inhibiting amygdala output. Interestingly, many of these changes are initiated after the cessation of extinction training, suggesting that consolidation of extinction involves activity in prefrontal-amygdala circuits. Understanding consolidation of extinction could be applicable to anxiety disorders such as PTSD, which are treated with extinction-based exposure therapies.
Tuesday April 5, 4-5 pm	Wilma Friedman, Department of Biological Sciences, Rutgers University TITLE: “Nerve growth factor in the brain: A double-edged sword” Abstract: Neurotrophic factors are proteins that influence survival and function of neurons in the central and peripheral nervous systems. Recent studies, however, have shown that specific neurotrophic factors may cause neuronal death instead of survival, depending upon which receptors and signaling pathways are activated. We are examining mechanisms governing death- vs. survival-promoting actions of nerve growth factor and related neurotrophins during development and under inflammatory conditions.
Tuesday April 19, 4-5 pm	Greg Ashby, Department of Psychology, University of California at Santa Barbara TITLE: “The neurobiology of human category learning” Abstract: To categorize is to respond differently to objects or events in separate classes or categories. This vitally important skill allows us to approach food or friend and to avoid toxin or trap. Recent evidence suggests that human category learning is mediated by multiple, qualitatively distinct learning systems, and much is now known about the neurobiology that underlies these systems. Several of these systems will be described, including a frontal-based explicit system that uses logical reasoning and depends on working memory and executive attention, and a basal ganglia-mediated implicit system that uses procedural learning. The study of category learning improves our understanding of a basic human skill, leads to better insights into the cognitive changes that result from a variety of different neurological disorders, and suggests improvements in training procedures for complex categorization tasks (e.g., teaching radiology students to find tumors in x-rays).
Tuesday April 26, 4-5 pm	Bruno Rossion, Unite de Neurosciences Cognitives and Laboratoire de Neurophysiologie, Universite Catholique de Louvain, Belgium TITLE: How does the brain discriminate familiar and unfamiliar faces? Abstract: TBA