Local Differences in Network Organization in the Auditory and Parietal Cortex, Revealed with Single Neuron Activation

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Cortical local circuit structure is conserved, but population activity dynamics differ between sensory and association areas.
• Sensory cortex activity has shorter timescales and decays sharply, supporting fine-scale sensory feature coding.
• Association cortex activity has longer timescales and spreads widely, aiding memory and behavior control.

Purpose of the Study:

• To investigate if differences in network structure explain the distinct population activity dynamics in sensory versus association cortices.
• To compare the spatial and temporal properties of neural network responses in auditory cortex (AC) and posterior parietal cortex (PPC).

Main Methods:

• Targeted photostimulation of single layer 2/3 excitatory neurons in AC and PPC of mice.
• Two-photon calcium imaging to monitor surrounding population activity.
• Experiments conducted in mice expressing a red fluorophore in somatostatin-expressing interneurons (SOM).

Main Results:

• Photostimulation induced a local excitatory zone and a wider inhibitory 'suppressive surround' in both AC and PPC.
• PPC showed a wider positive influence zone but a narrower suppressive surround compared to AC.
• AC exhibited a narrower positive influence zone and a wider suppressive surround than PPC.

Conclusions:

• Differences in the spatial extent of positive and negative neural influences in AC and PPC can account for their distinct network dynamics.
• The network structure in PPC, with wider excitation and narrower inhibition, supports large-scale network activity for memory and behavior.
• The network structure in AC, with narrower excitation and wider inhibition, may sharpen sensory representations.