Redwood Neuroscience
Title "Fine-Scale Specificity of
Cortical Connections”
Ed
Callaway
Systems
Neurobiology Laboratories
Salk
Abstract:
The specificity of cortical neuron connections creates
columns of functionally similar neurons spanning from the pia
to the white matter. We investigated whether there is an additional, finer
level of specificity that creates subnetworks of
excitatory neurons within functional columns. We tested for fine-scale
specificity of connections to cortical layer 2/3 pyramidal neurons in rat
visual cortex by using cross-correlation analyses of synaptic currents evoked
by photostimulation. Recording simultaneously from
adjacent layer 2/3 pyramidal cells, we find that when they are connected to
each other (20% of all recorded pairs) they share common input from layer 4 and
within layer 2/3. When adjacent layer 2/3 neurons are not connected to each other,
they share very little (if any) common excitatory input from layers 4 and 2/3.
In contrast, all layer 2/3 neurons share common excitatory input from layer 5
and inhibitory input from layers 2/3 and 4, regardless of whether they are
connected to each other. Thus, excitatory connections from layer 4 to layer 2/3
and within layer 2/3 form fine-scale assemblies of selectively interconnected
neurons; inhibitory connections and excitatory connections from layer 5 link
neurons across these fine-scale subnetworks.
Relatively independent subnetworks of excitatory
neurons are therefore embedded within the larger-scale functional architecture;
this allows neighbouring neurons to convey
information more independently than suggested by previous descriptions of
cortical circuitry.