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Layer V pyramidal neuron
- Dendrites sample the entire cortical column.
- Axons project locally, and distally to basal ganglia,
brainstem, & spinal cord.
- Receives local inputs (from the same cortical
column) and distal inputs (other cortical areas and
thalamus).
From Lübke et al 1996
Excitatory connections between layer V pyramidal cells
Full connectivity predicted from morphology
vs.
Sparse (10 %) functional connectivity
Kalisman et al 2005
Touch
# axo-dendritic touches
The solution: All-to-All Potential Connectivity
Unconnected
Whole-cell recordings &
6
Connected
Confocal connection analysis
5
4
3
2
1
Bouton
# boutons
0
3
2
1
0
Connections between interneurons & pyramidal neurons
Summary
- An inhibitory feedback loop is described for
layer V pyramidal cells.
- The loop is frequency dependent, and is
more prevalent than monosynaptic excitation.
- It is mediated by a facilitating excitatory
connection onto GABAergic inhibitory
neurons.
- The inhibition is targeted to the dendrites of
pyramidal neurons (low reversal & dendritic
patch experiments).
- Multi-patch recordings of PCs and
Interneurons revealed that the loop was
mediated by dendritic-targeting Martinotti
cells.