cerebral cortex; somatosensory system; homeostatic plasticity; barrel; neuronal plasticity; synapse formation¨; sensory information; homeostasis
Pichon Fabien, Nikonenko Irina, Kraftsik Rudolf, Welker Egbert (2012), Intracortical connectivity of layer VI pyramidal neurons in the somatosensory cortex of normal and barrelless mice., in The European journal of neuroscience
, 35(6), 855-69.
Landers M S, Knott G W, Lipp H P, Poletaeva I, Welker E (2011), Synapse formation in adult barrel cortex following naturalistic environmental enrichment., in Neuroscience
, 199, 143-52.
Knott Graham W, Holtmaat Anthony, Trachtenberg Joshua T, Svoboda Karel, Welker Egbert (2009), A protocol for preparing GFP-labeled neurons previously imaged in vivo and in slice preparations for light and electron microscopic analysis., in Nature protocols
, 4(8), 1145-56.
Giaume Christian, Maravall Miguel, Welker Egbert, Bonvento Gilles (2009), The barrel cortex as a model to study dynamic neuroglial interaction., in The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry
, 15(4), 351-66.
In the adult mouse, layer IV of the barrel cortex consists of excitatory and inhibitory interneurons that, together with the astrocytes react onto increased sensory stimulation in a very robust manner. We have shown that the structural modifications induced by 24 hours of continuous stimulation in the adult mouse include synapse formation (Knott et al., 2002), modified astrocytic coverage of excitatory synapses on spines (Genoud et al., 2006) and lead, at the functional level to a diminished response of the neurons upon deflection of the stimulated whisker (Quairiaux et al., 2007). These observations have led to the notion that layer IV of the adult somatosensory cortex is capable to react to an increased level of neuronal activity to maintain a level of homeostasis. It forms an example that illustrates the partnership between the various cellular elements that together regulate the neuronal network after a perturbation of its level of activity and turns the barrel cortex into a model to study homeostatic plasticity in the adult nervous system.To further contribute to the understanding of the molecular and structural basis for the homeostatic response we here formulated the following goals: i) to characterize the molecular pathways that are involved in the synaptic modifications underlying whisker-stimulation induced plasticity and to investigate how they are expressed in the different neuronal cell types in layer IV; and ii) to study alteration in the synaptic input to GABAergic neurons in stimulated barrels. The first set of experiments will be based on the analysis of the results of the micro-array study that we are currently performing in collaboration with Dr. Markus Ruegg of the Biozentrum of the University of Basel. Using bio-informatics we will identify the molecular pathways involved in the homeostatic process induced by whisker stimulation. Subsequently, we will investigate whether the different neuronal cell types modify gene expression in specific manners. These studies will involve in situ hybridization and immunohistochemistry.In the second set of experiments, serial section EM-analysis will be applied to investigate whether the input to GABAergic neurons is altered by the increased neuronal activity induced by the whisker stimulation paradigm. Two methods will be used to label and reconstruct individual GABAergic neurons: one is based on biocytin injection prior to stimulation; the second, on the use on mouse lines in which different GABAergic cell classes express GFP.