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Updated: Sep 22, 2025
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Large-scale Three-dimensional Imaging of Cellular Organization in the Mouse Neocortex
Published on: September 5, 2018
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Conserved patterns of functional organization between cortex and thalamus in mice
Andrew J Miller-Hansen1, S Murray Sherman1
1Department of Neurobiology, University of Chicago, Chicago, IL 60637.
Summary
Higher-order thalamic nuclei modulate sensory processing. Layer 5 cortical neurons drive feedback through the thalamus, influencing primary sensory cortex differently based on cortical area.
Area of Science:
- Neuroscience
- Sensory processing
- Thalamocortical circuitry
Background:
- Higher-order thalamic nuclei are crucial for sensory processing, projecting to various cortical areas.
- The specific cortical and subcortical inputs shaping distinct higher-order thalamic output pathways remain unclear.
Purpose of the Study:
- To anatomically and physiologically dissect the input-output pathways of higher-order thalamic nuclei in the somatosensory (posterior medial nucleus) and visual (pulvinar) systems.
- To investigate the functional properties of thalamocortical synapses in primary versus higher cortical areas.
Main Methods:
- Utilized subpopulation-specific viral strategies in mice.
- Employed complementary optogenetics and electrical stimulation.
- Used transsynaptic tracing verified by optogenetics to map inputs.
Main Results:
- Higher-order thalamic projections to primary sensory cortex (S1, V1) were weakly modulatory.
- Projections to higher cortical areas (S2, higher visual areas) acted as strong drivers.
- Layer 5 neurons in primary and higher cortical areas were identified as key drivers of feedback pathways through the posterior medial nucleus and pulvinar.
Conclusions:
- Layer 5 of cortical areas drives transthalamic feedback modulation of primary sensory cortex via higher-order thalamus.
- This organization suggests conserved principles in thalamocortical circuitry.
- Transthalamic pathways parallel direct corticocortical projections, with feedforward pathways acting as drivers and feedback pathways as modulators.
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