Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

Effects of Adaptation in a Somatosensory Thalamocortical Circuit

Khatri, Vivek (2005) Effects of Adaptation in a Somatosensory Thalamocortical Circuit. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

Primary Text

Download (1MB) | Preview


In the mammalian brain, thalamocortical circuits perform the initial stage of processing before information is sent to higher levels of the cerebral cortex. Substantial changes in receptive field properties are produced in the thalamocortical response transformation. In the whisker-to-barrel thalamocortical pathway, the response magnitude of barrel excitatory cells is sensitive to the velocity of whisker deflections, whereas in the thalamus, velocity is only encoded by firing synchrony. The behavior of this circuit can be captured in a model which contains a window of opportunity for thalamic firing synchrony to engage intra-barrel recurrent excitation before being 'damped' by slightly delayed, but strong, local feedforward inhibition. Some remaining aspects of the model that require investigation are: (1) how does adaptation with ongoing and repetitive sensory stimulation affect processing in this circuit and (2) what are the rules governing intra-barrel interactions. By examining sensory processing in thalamic barreloids and cortical barrels, before and after adaptation with repetitive high-frequency whisker stimulation, I have determined that adaptation modifies the operations of the thalamocortical circuit without fundamentally changing it. In the non-adapted state, higher velocities produce larger responses in barrel cells than lower velocities. Similarly, in the adapted barrel, putative excitatory and inhibitory neurons can respond with temporal fidelity to high-frequency whisker deflections if they are of sufficient velocity. Additionally, before and after adaptation, relative to putative excitatory cells, inhibitory cells produce larger responses and are more broadly-tuned for stimulus parameters (e.g., the angle of whisker deflection). In barrel excitatory cells, adaptation is angularly-nonspecific; that is, response suppression is not specific to the angle of the adapting stimulus. The angular tuning of barrel excitatory cells is sharpened and the original angular preference is maintained. This is consistent with intra-barrel interactions being angularly-nonspecific. The maintenance of the original angular preference also suggests that the same thalamocortical inputs determine angular tuning before and after adaptation. In summary, the present findings suggest that adaptation narrows the window of opportunity for synchronous thalamic inputs to engage recurrent excitation so that it can withstand strong, local inhibition. These results from the whisker-to-barrel thalamocortical response transformation are likely to have parallels in other systems.


Social Networking:
Share |


Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberHumphrey, Allen Lhumphrey@pitt.eduHUMPHREY
Committee MemberKeller,
Committee MemberSimons, Daniel Jcortex@pitt.eduCORTEX
Committee MemberUrban, Nathaniel
Committee MemberLand, Pete
Date: 20 December 2005
Date Type: Completion
Defense Date: 30 September 2005
Approval Date: 20 December 2005
Submission Date: 8 December 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Neurobiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: cortex; thalamus; whisker
Other ID:, etd-12082005-143022
Date Deposited: 10 Nov 2011 20:09
Last Modified: 15 Nov 2016 13:53


Monthly Views for the past 3 years

Plum Analytics

Actions (login required)

View Item View Item