Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits

Area of Science:

• Neuroscience
• Developmental Biology
• Sensory Systems

Background:

• The primary somatosensory cortex (S1) in mice contains a complete body map, mirroring subcortical maps.
• Peripheral changes during development can alter these maps via 'bottom-up' plasticity.
• The influence of S1 size on map organization and potential feedback to subcortical maps remains unclear.

Purpose of the Study:

• To investigate how the size of the primary somatosensory cortex (S1) influences body map organization.
• To determine if an altered S1 map can affect subcortical maps through feedback mechanisms.

Main Methods:

• Reduced S1 size in mice via cortex-specific deletion of the Pax6 gene.
• Analysis of body map organization and sensory thalamocortical input.
• Manipulation of thalamocortical axon competition using sensory deprivation and S1 size alteration.

Main Results:

• Reduced S1 size led to a smaller body map and loss of specific body representations.
• An initially normal sensory thalamus was repatterned to match the aberrant S1 map.
• Thalamic neuron apoptosis occurred for body parts whose axons were excluded from S1.
• Representation loss was rescued by altering thalamocortical axon competition or increasing S1 size.

Conclusions:

• S1 size is a critical determinant of body map resolution and completeness.
• S1 engages 'top-down' plasticity to reorganize the sensory thalamus, ensuring alignment with the cortical map.
• This study reveals a novel top-down mechanism in sensory map development and maintenance.