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In JoVE (1)
Other Publications (2)
Articles by Bryan J. Hansen in JoVE
JoVE Neuroscience
Examining Local Network Processing using Multi-contact Laminar Electrode Recording
1Graduate School of Biomedical Science, Neuroscience Program, University of Texas, 2Department of Neurobiology and Anatomy, University of Texas
A fundamental issue in our understanding of cortical circuitry is how networks in different cortical layers encode sensory information. Here we describe electrophysiological techniques utilizing multi-contact laminar electrodes to record single-units and local field potentials and present analyses to identify cortical layers.
Other articles by Bryan J. Hansen on PubMed
Attention Alters Visual Plasticity During Exposure-based Learning
It is generally believed that attention enhances the processing of sensory information during perception and learning. Here we report that, contrary to common belief, attention limits the degree of plasticity induced by repeated exposure to image features. Specifically, daily exposure to oriented stimuli that are not linked to a specific task causes an orientation-specific improvement in perceptual performance along the "exposed" axes. This effect is modulated by attention: human subjects showed a larger improvement in orientation discrimination when attention is directed toward the location where stimuli are presented. However, the capacity to perform discriminations away from the exposed orientation is enhanced when the exposure stimuli are unattended. Importantly, the improvement in orientation discrimination at the unattended location leads to a robust enhancement in the discrimination of complex stimuli, such as natural texture images, with orientation components along the exposed axes, whereas the improvement in orientation discrimination at the attended location exhibits only weak transfer to complex stimuli. These results indicate that sensory adaptation by passive stimulus exposure should be viewed as a form of perceptual learning that is complementary to practice-based learning in that it reduces constraints on generalization.
Adaptation-induced Synchronization in Laminar Cortical Circuits
A fundamental feature of information processing in neocortex is the ability of individual neurons to adapt to changes in incoming stimuli. It is increasingly being understood that cortical adaptation is a phenomenon that requires network interactions. The fact that the structure of local networks depends critically on cortical layer raises the possibility that adaptation could induce specific effects in different layers. Here we show that brief exposure (300 ms) to a stimulus of fixed orientation modulates the strength of synchronization between individual neurons and local population activity in the gamma-band frequency (30-80 Hz) in macaque primary visual cortex (V1) and influences the ability of individual neurons to encode stimulus orientation. Using laminar probes, we found that although stimulus presentation elicits a large increase in the gamma synchronization of rhythmic neuronal activity in the input (granular) layers of V1, adaptation caused a pronounced increase in synchronization in the cortical output (supragranular) layers. The increase in gamma synchronization after adaptation was significantly correlated with an improvement in neuronal orientation discrimination performance only in the supragranular layers. Thus, synchronization between the spiking activity of individual neurons and their local population may enhance sensory coding to optimize network processing across laminar circuits.
