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Cell type specific connections from primary motor to primary somatosensory cortex.

Kinnischtzke, Amanda K (2013) Cell type specific connections from primary motor to primary somatosensory cortex. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Anatomical studies have shown that primary somatosensory (S1) and primary motor
(M1) cortices are reciprocally connected. The pathway from primary motor cortex (M1) to
primary somatosensory cortex (S1) is thought to influence activity in S1 by conveying a general
modulatory signal and/or a copy of the motor command. In these studies, we investigated M1
synaptic inputs to S1 by injecting an AAV virus containing channelrhodopsin-2 and a fluorescent
tag into M1. Consistent with previous results, we found labeling of M1 axons within S1 that was
most robust in the deep layers and in L1. We recorded in vitro from excitatory neurons and two
classes of inhibitory interneurons, fast-spiking and somatostatin-expressing inhibitory
interneurons. All three cell types had a high probability of receiving direct excitatory M1 input,
with both excitatory and inhibitory cells in L4 being the least likely to receive input from M1.
Disynaptic inhibition was observed frequently, indicating that M1 recruits substantial inhibition
within S1.
A subpopulation of pyramidal neurons in layers 5 and 6 received especially strong input
from M1, suggesting M1 differentially contacts classes of pyramidal neurons, such as those
projecting to different sensorimotor centers at cortical and subcortical levels. We tested this
hypothesis by combining optogenetic techniques to specifically label M1 synaptic inputs to S1
and retrograde tracing to identify specific populations of projection neurons in infragranular
layers of S1. We determined that both the intrinsic properties and the magnitude of M1 input to
an S1 pyramidal neuron is highly dependent on its projection target.

Overall, our results suggest that activation of M1 evokes within S1 a general increase in
excitatory and inhibitory synaptic activity that could contribute in a layer-specific manner to
state-dependent changes in S1. Our results further indicate that M1 may specifically engage subcircuits
within S1 in order to differentially regulate particular downstream cortical and
subcortical processing centers.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Kinnischtzke, Amanda Kakk31@pitt.eduAKK31
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairAizenman, Eliasredox@pitt.eduREDOX
Committee MemberDoiron, Brentbdoiron@pitt.eduBDOIRON
Committee MemberOswald, Anne-Marie
Committee MemberFanselow, Erika
Committee MemberKeller,
Thesis AdvisorSimons, Daniel Jcortex@pitt.eduCORTEX
Date: 24 July 2013
Date Type: Publication
Defense Date: 8 July 2013
Approval Date: 24 July 2013
Submission Date: 23 July 2013
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 159
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Neurobiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: somatosensory cortex; sensorimotor integration; inhibitory interneurons; somatosensory system
Date Deposited: 24 Jul 2013 18:58
Last Modified: 15 Nov 2016 14:14


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