Rapid Bidirectional Reorganization of Cortical Microcircuits

Area of Science:

• Neuroscience
• Cellular Biology
• Systems Neuroscience

Background:

• The mature neocortex exhibits plasticity, adapting neural activity in response to altered sensory input.
• The specific cellular mechanisms driving this neural reorganization remain largely undetermined.

Purpose of the Study:

• To investigate the cellular mechanisms underlying neocortical adaptation to altered sensory input.
• To examine the dynamic changes in neural connectivity within the somatosensory cortex.

Main Methods:

• Utilized blood oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to observe cortical map reorganization.
• Employed paired electrophysiological recordings in the primary somatosensory cortex to assess neuronal connectivity.

Main Results:

• Observed rapid expansion and subsequent retraction of whisker cortical maps following altered sensory input.
• Found a threefold increase in monosynaptic connections between pyramidal neurons during map expansion, with no change in connection strength or dynamics.
• Demonstrated the loss of excitatory connections between pyramidal neurons during map retraction, while connections with fast-spiking interneurons remained stable.

Conclusions:

• Pyramidal neurons are dynamically recruited to and eliminated from local excitatory networks within days.
• The local excitatory connectome in the mature neocortex is highly dynamic.
• These findings elucidate the cellular basis of sensory map plasticity in the neocortex.