Neural Circuits Lecture 15

Lecture 15 27th March 2017


Neural Circuits

Cortical Microcircuits

The cortical zoo: cell diversity
 About 30 types of GABAergic neurons
 About 15-20 types of glutamatergic neurons

Excitatory neurons
 Cell types defined by laminar location(what layer in the cortex they
project to) and projection largely agree with those identified by RNA
sequencing
 Project to further regions of the brain
 Layer 4 – granule layer
 Missing in most cortices
 But always found in sensory cortex
 L4 IT
 Layer 4 Isothalamic neurons
 Project to the cortex layers 3 and 5
 IT
 Isothalamic neurons in layers 2,3, 5 and 6
 Pyramidal cells
 Long apical dendrites to layer 1
 Layer 1 contains fibres.
 PT
 Pyramidal tract neurons
 Long range communicators
 Project to other brain areas such as the brain stem
 CT
 Cortical Thalamic neurons
 Layer 6
 Sends information to the thalamus
 Each type has a role in the “connection matrix” for a cortical region

Inhibitory neurons
 Around 30 types resulting from the intersection of relevant classification
parameters:
 Morphology
 Connectivity
 Markers
 Intrinsic properties
 ~30% of the inhibitory neurons are somatostatin-expressing
 Martinotti cells
 X94
 Other?
 ~30% of the inhibitory neurons are 5HT3aR-expressing
 VIP
 Non-VIP
 ~40% of the inhibitory neurons are Parvalbumin- expressing