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Man Yi Yim at the Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh 2011

Man Yi Yim at the Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh 2011

April 6 - May 11, 2011
Host: Dr. Matthias Hennig, Dr. Mark Van Rossum

 

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I am currently studying how spike timing dependent plasticity (STDP) in cortico-striatal synapses shapes the connectivity structure and its effects on the striatum network together with Jyotika Bahuguna. This work is an extension of my previous work (Yim et al., 2011) where I suggested a functional role for the structure of cortico-striatal projections. Principal neurons and several types of interneurons in the striatum use GABA as a transmitter. Inhibition can affect spike timing and hence STDP in the cortico-striatal synapses. Therefore, recurrent connections mediated by GABAergic synapses in the striatum play a crucial role in the development of cortico-striatal projections. On the other hand, GABAergic neurons can also induce an excitatory postsynaptic potential early during development in several regions of the brain. Thus, it is crucial to understand the biochemical mechanisms that render GABAergic synapses excitatory or inhibitory before we study the effects of GABAergic activity on STDP.

Dr. Matthias Hennig and his student Oliver Muthmann are working on homeostatic plasticity and its underlying neuronal mechanisms. They introduced me to the molecular mechanism underlying the switching of GABAergic synapses from excitatory to inhibitory. Such a mechanism has also been observed in the retina, the neural system that Dr. Hennig is studying. Briefly, the concentration of chloride inside neurons increases at some stage during development. The reversal potential of inhibitory synapses is mainly determined by the flow of chloride ions. In the retina, it can change from -40 mV to -70 mV, and this switch occurs at around postnatal day 6 (P6) and is completed within one day. The timing of the switch is different in different brain regions. Therefore, for my work, I need to consider the timing of (1) the switch of the sign for GABAergic synapses in the striatum and (2) the development of the cortico-striatal inputs. If (1) precedes (2), then GABA is inhibitory during the development of cortico-striatal connectivity, otherwise excitatory. It is obvious that this makes an important difference.

edinburgh_2011.jpgIn addition, I presented my work on the impact of input correlation on neuronal activity in the lab of Dr. Hennig and received helpful feedback. Several students there are also interested in correlation, and at multiple occasions we discussed several recent papers on the topic. In particular, some techniques potentially useful for the treatment of correlation transmission were reviewed, including linear-nonlinear cascade models and phase models. All these interactions provided me with a broader perspective on my ongoing research with regard to the role of correlations in shaping the ongoing activity as well as information processing.

Thanks for the hospitality of the School of Informatics in University of Edinburgh to make my research visit meaningful and interesting. In addition, the support from the Bernstein Center Freiburg and its PhD-program "iCoNeT" is gratefully acknowledged.

 

Funded by the German Academic Exchange Service (DAAD) and the Federal Ministry of Education and Research (BMBF).

 


 

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