%0 Generic
%A Leitner, Frauke Christiane
%C Heidelberg
%D 2015
%F heidok:18866
%K entorhinal cortex, calcium imaging
%R 10.11588/heidok.00018866
%T Odor processing in the lateral entorhinal cortex revealed by two-photon calcium imaging
%U https://archiv.ub.uni-heidelberg.de/volltextserver/18866/
%X Recent studies ascribed to the lateral entorhinal cortex (LEC) an important function in object recognition and novelty detection and confirmed the involvement of the LEC in odor processing. In this thesis, I investigated the contribution of LEC layer II neurons in sensory processing. Using immunohistochemical staining methods I could show that excitatory neurons in LEC layer II can be distinguished based on the expression of two marker proteins, namely Reelin and calbindin (CB). In combination with retrograde tracer injections, I revealed distinct projection patterns of these two excitatory cell types, with Reelin+ neurons projecting to the hippocampus and CB+ neurons providing feedback to structures of the olfactory system. Inhibitory GABAergic neurons in layer II of the LEC comprise a variety of molecularly defined subtypes. My goal was to analyze the participation of the defined cell classes in stimulus-triggered network activity. Therefore, I implemented in vivo two-photon imaging of genetically encoded calcium indicators in the LEC of anesthetized mice. This approach allowed me to investigate the activity of small neuronal networks in response to olfactory stimulation. I demonstrated that Reelin+ excitatory neurons transmitting information directly to the hippocampus respond with high selectivity to different odors. A markedly less selective response profile is exhibited by excitatory CB+ neurons that convey feedback to upstream targets in the olfactory pathway. It was possible to contrast these response patterns of excitatory neurons with that of their inhibitory counterparts. Thus, GABAergic neurons responded the least selective to various odors. Furthermore, we established in vivo whole-cell patch-clamp recordings under visual guidance. This enabled us to particularly target excitatory and GABAergic odor-responsive cells and to characterize them based on electrophysiological and morphological criteria. In summary, I defined and characterized here different neuronal subtypes in the LEC that are functionally involved in the processing and transmission of odor information.