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Articles 31 - 36 of 36

Full-Text Articles in Systems Neuroscience

Modulation Of Spasticity By Trans-Spinal Direct Current Stimulation In Animals With Spinal Cord Injury, Wagdy Mekhael Sep 2017

Modulation Of Spasticity By Trans-Spinal Direct Current Stimulation In Animals With Spinal Cord Injury, Wagdy Mekhael

Dissertations, Theses, and Capstone Projects

Central nervous system injuries usually produce motor impairments that are exacerbated by pathologically altered muscle tone. Abnormal muscle tone interferes with voluntary movement and is associated with loss of dexterity. Prior work in our laboratory demonstrated that 30-second trans-spinal direct current (DC) stimulation can temporarily modify muscle tone in anesthetized spastic mice after spinal cord injury (SCI). These experiments described DC-induced muscle tone responses to be polarity-dependent. That is, anodal stimulation (current passed from the lumbar spine to sciatic nerve) decreased muscle tone, and cathodal stimulation (current passed from the sciatic nerve to the lumbar spine) increased it. The present …


Rules And Mechanisms For Efficient Two-Stage Learning In Neural Circuits, Tiberiu Teşileanu, Bence Ölveczky, Vijay Balasubramanian Jan 2017

Rules And Mechanisms For Efficient Two-Stage Learning In Neural Circuits, Tiberiu Teşileanu, Bence Ölveczky, Vijay Balasubramanian

Publications and Research

Trial-and-error learning requires evaluating variable actions and reinforcing successful variants. In songbirds, vocal exploration is induced by LMAN, the output of a basal ganglia-related circuit that also contributes a corrective bias to the vocal output. This bias is gradually consolidated in RA, a motor cortex analogue downstream of LMAN. We develop a new model of such two-stage learning. Using stochastic gradient descent, we derive how the activity in ‘tutor’ circuits (e.g., LMAN) should match plasticity mechanisms in ‘student’ circuits (e.g., RA) to achieve efficient learning. We further describe a reinforcement learning framework through which the tutor can build its teaching …


Protein Kinase M Zeta-Mediated Ltp Maintenance In The Non-Human Primate Hippocampus: A Role For Stress And Serotonergic Signaling In Affective Processing, Sasha L. Fulton Dec 2016

Protein Kinase M Zeta-Mediated Ltp Maintenance In The Non-Human Primate Hippocampus: A Role For Stress And Serotonergic Signaling In Affective Processing, Sasha L. Fulton

Theses and Dissertations

Early-Life Stress (ELS) is associated with vulnerability to mood disorder, but it’s not well understood how ELS contributes to deficits in cognitive function. Atypical PKMzeta is critical for LTP maintenance and memory. The current study aims to characterize the ELS phenotype with respect to this key marker of hippocampal LTP.


The Impact Of Affect On Neural Mechanisms Underlying Orientation Perception, Michelle L. Fowler Feb 2016

The Impact Of Affect On Neural Mechanisms Underlying Orientation Perception, Michelle L. Fowler

Dissertations, Theses, and Capstone Projects

The underlying mechanisms used to process 2D visual information to form a unified 3D percept of the world remain largely unknown. Previous work in our lab has shown that accurate 3D perception of textured surfaces depends on the presence of specific patterns of orientation flows in the retinal image. Recent research has shown that affective state may influence the visual perception of oriented patterns. Relative to neutral face stimuli, fearful face stimuli have been shown to increase sensitivity to orientation of low spatial frequency patterns and decrease sensitivity to orientation of high spatial frequency patterns. How affective state influences the …


A Principle Of Economy Predicts The Functional Architecture Of Grid Cells, Xue-Xin Wei, Jason Prentice, Vijay Balasubramanian Jan 2015

A Principle Of Economy Predicts The Functional Architecture Of Grid Cells, Xue-Xin Wei, Jason Prentice, Vijay Balasubramanian

Publications and Research

Grid cells in the brain respond when an animal occupies a periodic lattice of ‘grid fields’ during navigation. Grids are organized in modules with different periodicity. We propose that the grid system implements a hierarchical code for space that economizes the number of neurons required to encode location with a given resolution across a range equal to the largest period. This theory predicts that (i) grid fields should lie on a triangular lattice, (ii) grid scales should follow a geometric progression, (iii) the ratio between adjacent grid scales should be √e for idealized neurons, and lie between 1.4 and 1.7 …


Variance Predicts Salience In Central Sensory Processing, Ann M. Hermundstad, John J. Briguglio, Mary M. Conte, Jonathan D. Victor, Vijay Balasubramanian, Gašper Tkačik Jan 2014

Variance Predicts Salience In Central Sensory Processing, Ann M. Hermundstad, John J. Briguglio, Mary M. Conte, Jonathan D. Victor, Vijay Balasubramanian, Gašper Tkačik

Publications and Research

Information processing in the sensory periphery is shaped by natural stimulus statistics. In the periphery, a transmission bottleneck constrains performance; thus efficient coding implies that natural signal components with a predictably wider range should be compressed. In a different regime—when sampling limitations constrain performance—efficient coding implies that more resources should be allocated to informative features that are more variable. We propose that this regime is relevant for sensory cortex when it extracts complex features from limited numbers of sensory samples. To test this prediction, we use central visual processing as a model: we show that visual sensitivity for local multi-point …