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CCN Brown Bag Series: Tom Palmeri
September 2, 2015

Approaches to Model-based Cognitive Neuroscience

Tom Palmeri Ph.D., Department of Psychology, Vanderbilt University

Wednesday, Sept. 2, 2015

12:10 p.m. Wilson Hall, Room 115

Cognitive modeling has a rich history of formalizing and testing hypotheses about cognitive mechanisms within a mathematical and computational language, making exquisite predictions of how people perceive, learn, remember, and decide. Cognitive neuroscience aims to identify neural mechanisms associated with key aspects of cognition, using techniques like neurophysiology, electrophysiology, and structural and functional brain imaging. These two come together in a powerful approach called model-based cognitive neuroscience, which can both inform model development and model selection and help interpret neural measures. Cognitive models decompose complex behavior into representations and processes and these latent model states are used to explain the modulation of brain states under different experimental conditions. Reciprocally, neural measures provide data that help constrain cognitive models and adjudicate between competing cognitive models that make similar predictions of behavior. I will outline a first attempt to develop a taxonomy of different approaches to model-based cognitive neuroscience, often making references to our collaborative work at Vanderbilt, highlighting potential strengths and weaknesses of different approaches.


Neuroscience Brown Bag Series: Jon Kaas
September 3, 2015

The evolution of parietal-frontal networks for specific actions in primates

Jon Kaas, Ph.D., Department of Psychology Vanderbilt University 

Thursday, September 3, 2015

12:10 p.m. Wilson Hall 316

For over ten years we have been using electrical stimulation of the cortex as the primary tool in our studies of posterior parietal-to-frontal motor cortex pathways that are mediating specific classes of motor behavior in primates. The electrical stimulation has been useful, as it gives us a lot of control over the behavior as we manipulate the networks. We have studied prosimian primates, New World monkeys, and Old World monkeys, as well as other mammals to reveal similarities and differences in the networks, and suggest how they might have evolved. Our anatomical and physiological studies have led to results that support a number of conclusions. Most important, all primates likely have interacting networks for eight or more classes of behavior that involve domains in posterior parietal cortex, premotor cortex, and primary motor cortex. The domains function as a feed-forward posterior parietal-to-premotor-to-motor cortex series. Electrically stimulating any domain evokes slight variations of a specific behavior as a result of focused feedforward projections. Domains interact in ways that modify or inhibit specific behaviors via lateral connections in each cortical region, and by feedback connections. Other inputs contribute to each cortical region to modulate the final behavioral outcome. Close relatives of primates, tree shrews and rodents, do not have the large posterior parietal cortex of primates, and their posterior parietal cortex plays a minor role in motor behavior. The extensive expansion of posterior parietal cortex that is found in humans suggests an increased and more varied role in sensorimotor behavior.

 


Clinical Brown Bag Series: Steve Brunwasser
September 8, 2015

Steve Brunwasser, Kennedy Center for Research, Vanderbilt University

Tuesday, Sept. 8, 2015

12:10 p.m. Wilson Hall, Room 316

Title and abstract: TBA


CCN Brown Bag Series: Ming Meng
September 9, 2015

Ming Meng, Ph.D., Center for Social Brain Sciences. Dartmouth University

Wednesday, Sept. 9, 2015

12:10 p.m. Wilson Hall, Room 115

Fluctuations of fMRI activation patterns underlie the theta-band rhythmic effects of visual object priming

To efficiently interact with an ever-changing environment, the brain dynamically responds to sensory stimulation. Notably, whereas high-frequency gamma band activity may directly underlie neuronal spike coordination (Crick & Koch, 1990), slower waves carrying (multiplexing) faster waves appear to be a common perceptual coding strategy in the brain (VanRullen & Koch, 2003). Recent behavioral studies further suggest a theta-band rhythm (4-7 Hz) in the effects of attention and priming (e.g., Fiebelkorn, Saalmann, & Kastner, 2013; Song et al., 2014; Huang, Chen, & Luo, 2015). Here, I investigate three possible brain mechanisms that may lead to such rhythmic behavioral effects: 1) object representations may be rhythmic in the inferior temporal (IT) cortex; 2) Object representations may be constant, but attentional selection of the representations may be rhythmic; 3) Sensory sampling may be rhythmic as early as the primary visual cortex, therefore all the subsequent processes may also be rhythmic. To test these possibilities, activity corresponding to visual object priming was measured in regions of interest (ROIs) across the whole brain by using fMRI.  Critically, to examine rhythmic effects, time-resolved measurements of fMRI activation patterns were attained by varying trial-by-trial stimulus onset asynchrony (SOA) between prime and probe in small steps of 20ms (equivalent to a 50Hz sampling rate). Our behavioral results replicated previous findings, showing theta-band oscillations in the priming effects of reaction times as a function of SOA. More interestingly, multivariate pattern analysis of the fMRI data also demonstrated theta-band oscillations as a function of SOA and an out-of-phase relationship between congruent and incongruent conditions in the IT cortex. No such effects were found in the BA17 or the frontoparietal attention network. This study is the first to map theta-band rhythms across the whole human brain using fMRI. Our results suggest that object representation is oscillatory with theta-band rhythms in the IT cortex, providing insights to understanding the dynamic mechanisms underlying visual perception.

 


Neuroscience Brown Bag Series: Siyuan Yin
September 10, 2015

Siyuan Yin, Department of Psychology, Vanderbilt University

Thursday, Sept. 10, 2015

12:10 p.m. Wilson Hall 316

TITLE AND ABSTRACT: TBD


Clinical Brown Bag Series: Carissa Cascio
September 15, 2015

Carissa Cascio, Child and Adolescent Psychiatry, Vanderbilt University Medical Center

Tuesday, Sept. 15, 2015

12:10 p.m. Wilson Hall, Room 316

TITLE AND ABSTRACT: TBA


CCN Brown Bag Series: Miguel Eckstein
September 16, 2015

Rapidly looking at faces: A sensory optimization theory

Miguel P. Eckstein, Department of Psychological and Brain Sciences, University of California, Santa Barbara

Wednesday, Sept. 16, 2015

12:10 p.m. Wilson Hall, Room 115

When viewing a human face people first look towards the eyes. A prominent idea holds that these fixation patterns arise solely due to social norms.  Here, I propose that this behavior can be explained as an adaptive brain strategy to learn eye movement plans that optimize the rapid extraction of visual information for  evolutionarily important perceptual tasks. I show that humans move their eyes to points of fixation that maximize perceptual performance determining the identity, gender, and emotional state of a face. These initial optimal points of fixation, which vary moderately across tasks, are correctly predicted by a foveated Bayesian ideal observer (FIO) that takes into account the task, integrates information optimally across the face but is constrained by the decrease in resolution and sensitivity from the fovea towards the visual periphery.  A model that disregards the foveated nature of the visual system and makes eye movements either to the regions/features with the highest discriminative information or center of the face fails to predict the human fixations.   The preferred points of initial fixation are similar across cultural groups (East Asians vs. Caucasians).    However,  there are individual differences with a majority of observers (~ 85 %) looking just below the eyes while a minority ( ~ 15) closer to the tip of the nose and below.  The systematic differences in initial points of fixation persist over time and also correspond to individual variations in the points of fixation that maximize perceptual performance.   Finally , observers have difficulty changing their eye movement plans when confronted with unusual faces or simulated scotomas that make their over-practiced preferred points of fixation suboptimal.  Together, these results illustrate how the brain optimizes initial eye movements to rapidly extract information from faces based on the statistical distribution of discriminatory information, general properties of the human visual system and individual specific neural characteristics, and also highlight the ingrained nature of these highly practiced motor programs.

References:

Or, C.F.C., Peterson, M.F., Eckstein M.P., Initial eye movements during face identification are optimal and similar across cultures, Journal of Vision, 2015 (in press)

Peterson, M. F., & Eckstein, M. P. Learning optimal eye movements to unusual faces. Vision Research, 99, 57-68 (2014)

Peterson, M. F., & Eckstein, M. P. Individual Differences in Eye Movements During Face Identification Reflect Observer-Specific Optimal Points of Fixation , Psychological science, 24(7), 1216-25, (2013)

 

Peterson, M. F., & Eckstein, M. P. Looking just below the eyes is optimal across face recognition tasks. Proceedings of the National Academy of Sciences, 109(48), E3314-E3323  (2012).

 


Clinical Brown Bag Series: Andre Christie-Mizell
September 22, 2015

Andre Christie-Mizell, Ph.D., Sociology Department, Vanderbilt University

Tuesday, Sept. 22, 2015

12:10 p.m. Wilson Hall 316

TITLE AND ABSTRACT: TBA


CCN Brown Bag Series: Sean Polyn
September 23, 2015

Sean Polyn, Ph.D., Department of Psychology, Vanderbilt University

Wednesday, Sept. 23, 2015

12:10 p.m. Wilson Hall, Room 115

Title and Abstract: TBD


Clinical Brown Bag Series: No Talk Scheduled
September 29, 2015

NO TALKS SCHEDULED FOR THIS DATE  (Kennedy Center Science Day)


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