Title: The Impact of Thalamic State on Sensory Cortical Processing and Behavior
February 17, 2017 by Leave a Comment
BME PhD Thesis Proposal Presentation
Date and Time:Thursday, March 2nd, 10-11am
Location: Emory Rollins Research Center 1052
Garrett Stanley (advisor)
Biyu He (NYU)
The thalamus is a central junction that processes both sensory afferent and motor efferent signals. Although many neurological disorders including Parkinson’s disease, Schizophrenia, and Central Pain are linked to thalamic dysfunction, basic information about thalamic processing is still unknown. Specifically, it is unclear how ongoing changes in membrane polarization (i.e. state) alter the transmission of information to and from cortical regions. Thalamic neurons have dynamic firing modes (i.e. tonic and burst) and receive tremendous amounts of neuromodulatory inputs that shape the encoding of sensory features. My project will develop novel techniques to measure entire cortical regions and use these tools determine the role of thalamic state on tactile processing and detectability of sensory inputs. Specifically, I utilize the novel genetically expressed voltage indicator ArcLight to measure voltage activity across cortical structures. I will record cortical ArcLight signals while simultaneously manipulating the ongoing thalamic activity using genetically expressed light sensitive protein channels (optogenetics). I will further combine these techniques to modulate thalamic state to control the evoked cortical response and behavioral performance of mice during a tactile detection task. It is critical that we understand how thalamic state alters information transmission to develop better treatment options for these complex neurological disorders.
February 9, 2017 by Leave a Comment
Nathaniel received his PhD in Physics from Washington University in St. Louis. He worked in Ralf Wessel’s lab, where he performed multi-whole-cell and local field potential recordings of visual responses in cortex. He and his collaborators combined these recordings with network simulations to study the dynamics and mechanisms of cortical coordination across multiple spatial scales during visual processing.
February 9, 2017 by Leave a Comment
Originally from China, Linlin Lu (Mia ), is a third year postgraduate student in the PKU-GT-Emory joint BME program. She received her bachelor’s degree of engineering in the department of Biomedical Engineering in Peking University in 2014 and continued her graduate studies in the laboratory of Prof. Duan Xiaojie at PKU. In the Duan lab, she focuses on developing flexible, soft and MRI compatible probes for chronic neural interface. As part of the Stanley lab she hopes to test the chronic recording capability and MRI compatibility of the probe in the whisker pathway, and try to combine the probe with other techniques, such as optogenetics and two-photon imaging, to develop better tools for use in neural science.
January 17, 2017 by Leave a Comment
In this research article, Whitmire and colleagues have been able to utilize optogenetic modulation of thalamic firing modes combined with optical imaging of cortex in the rat vibrissa system to directly test the role of thalamic state in shaping cortical response properties.
Sensory stimulation drives complex interactions across neural circuits as information is encoded and then transmitted from one brain region to the next. In the highly interconnected thalamocortical circuit, these complex interactions elicit repeatable neural dynamics in response to temporal patterns of stimuli that provide insight into the circuit properties that generated them. Here, using a combination of in-vivo voltage sensitive dye (VSD) imaging of cortex, single unit recording in thalamus, and optogenetics to manipulate thalamic state in the rodent vibrissa pathway, we probed the thalamocortical circuit with simple temporal patterns of stimuli delivered either to the whiskers on the face (sensory stimulation) or to the thalamus directly via electrical or optogenetic inputs (artificial stimulation). VSD imaging of cortex in response to whisker stimulation revealed classical suppressive dynamics, while artificial stimulation of thalamus produced an additional facilitation dynamic in cortex not observed with sensory stimulation. Thalamic neurons showed enhanced bursting activity in response to artificial stimulation, suggesting that bursting dynamics may underlie the facilitation mechanism we observed in cortex. To test this experimentally, we directly depolarized the thalamus using optogenetic modulation of the firing activity to shift from a burst to a tonic mode. In the optogenetically depolarized thalamic state, the cortical facilitation dynamic was completely abolished. Taken together, the results obtained here from simple probes suggest that thalamic state, and ultimately thalamic bursting, may play a key role in shaping more complex stimulus-evoked dynamics in the thalamocortical pathway.
Thalamic state control of cortical paired-pulse dynamics. Clarissa J Whitmire, Daniel C Millard, Garrett B. Stanley. PDF
December 6, 2016 by Leave a Comment