|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
CNBC Colloquium
Title: Neuronal mechanisms of visual categorization and decision making
Presenter: David Freedman, Ph.D.
Location: 6014 BST3
Abstract: We have a remarkable ability to recognize the behavioral significance, or category membership of a wide range of visual stimuli. While much is known about how simple visual features (such as color, orientation and direction of motion) are processed in early stages of the visual system, much less is known about how the brain learns and recognizes categorical information that gives meaning to incoming stimuli. This talk will review a series of neurophysiological and behavioral experiments aimed at understanding the neuronal representations underlying visual categorization and decision making with a focus on parietal and prefrontal cortices. We have found that the activity of individual neurons in both the posterior parietal and lateral prefrontal cortices can reflect the learned category membership of visual stimuli, and that these two areas play distinct roles in category-based decision making. The relationship between non-spatial cognitive signals and spatial signals (related to attention and eye movements) in parietal cortex will also be discussed.
Title: "The role of striatal microcircuits in basal ganglia disorders"
Presenter: Aryn Gittis, PhD
Location: 1495 BST3
Sponsored by the Department of Neurobiology
Department of Neurobiology, University of Pittsburgh Presents a Special Seminar:
Title: "Synaptic circuit organization of mouse motor cortex"
Presenter: Gordon M. G. Shepherd, MD, PhD
Location: 6014 Biomedical Science Tower 3
Ph.D. Dissertation Defense
Title: Characterizing the Spatiotemporal Neural Representation of Concrete Nouns Across Paradigms
Presenter: Gustavo Sudre -Neural Computation -Center for the Neural Basis of Cognition
Location: Gates 8102
Abstract: Most of the work investigating the representation of concrete nouns in the brain has focused on the locations that code the information. We present a model to study the contributions of perceptual and semantic features to the neural code representing concepts over time and space. The model is evaluated using magnetoencephalography data from different paradigms and not only corroborates previous findings regarding a distributed code, but provides further details about how the encoding of different subcomponents varies in the space-time spectrum. The model also successfully generalizes to novel concepts that it has never seen during training, which argues for the combination of specific properties in forming the meaning of concrete nouns in the brain. The results across paradigms are in agreement when the main differences among the experiments (namely, the number of repetitions of the stimulus, the task the subjects performed, and the type of stimulus provided) were taken into consideration. More specifically, these results suggest that features specific to the physical proper- ties of the stimuli are encoded in posterior regions of the brain in the first hundreds of milliseconds after stimulus onset. Then, properties inherent to the nouns are rep- resented in the signal starting at about 250 ms, focusing on more anterior parts of the cortex. The code for these different features was found to be distributed over time and space, and it was common for several regions to simultaneously code for a particular property. Moreover, most anterior regions were found to code for multiple features, and a complex temporal profile could be observed for the majority of properties. These findings complement much of the work previously described in the literature, and offer new insights about the temporal aspects of the neural encoding of concrete nouns. This model provides a spatiotemporal signature of the representation of objects in the brain. Paired with data from carefully-designed paradigms, the model is an important tool with which to analyze the commonalities of the neural code across stimulus modalities and tasks performed by the subjects.
Department of Neurology
Grand Rounds Series
Title: "Translational Stroke Research from Animal to Human: Problems and Hopes"
Presenter: Jun Chen, MD
Professor of Neurology and Pharmacology
Endowed Chair and Director
Center of Cerebrovascular Disease Research
University of Pittsburgh
Location: 1105AB Scaife Conference Center
Ph.D. Dissertation Defense
Title: Role of monkey prefrontal cortex in encoding multiple items in working memory
Presenter: Roma Konecky
Center for Neuroscience
Kenneth P. Dietrich School of Arts & Sciences/Neuroscience
Location: A219B Langley Hall