The thalamocortical synapse of the visual system has been central to our understanding of sensory computations in the cortex. Although we have a fair understanding of the functional properties of the pre and post-synaptic populations, little is known about their synaptic properties, particularly in vivo. We used simultaneous recordings in LGN and V1 in cat in vivo to characterize the dynamic properties of thalamocortical synaptic transmission in monosynaptically connected LGN-V1 neurons. We found that thalamocortical synapses in vivo are unreliable, highly variable and exhibit short-term plasticity. Using biologically constrained models, we found that variable and unreliable synapses serve to increase cortical firing by means of increasing membrane fluctuations, similar to high conductance states. Thus, synaptic variability and unreliability, rather than acting as system noise, do serve a computational function. Our characterization of LGN-V1 synaptic properties constrains existing mathematical models, and mechanistic hypotheses, of a fundamental circuit in computational neuroscience.
All data generated or analysed during this study are included in the manuscript and supporting files. Raw data and MATLAB code have been uploaded to Dryad (http://dx.doi.org/10.5061/dryad.57pv818).
Data from: Thalamocortical synapses in the cat visual system in vivo are weak and unreliableDryad Digital Repository, http://dx.doi.org/10.5061/dryad.57pv818.
- Larry A Palmer
- Diego Contreras
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) of the University of Pennsylvania (Protocol # 803477). All surgery was performed under sodium pentobarbital or propofol anesthesia, and every effort was made to minimize suffering.
- John Huguenard, Stanford University School of Medicine, United States
© 2019, Sedigh-Sarvestani et al.
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