Neocortical microcircuits: Role of excitatory feedback circuits within a barrel-related cortical column

• Applicant: Professor Dr. Dirk Feldmeyer
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2010 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 141272880

The connectivity pattern of excitatory synaptic connections in the barrel cortex and other cortical areas has been studied extensively. However, it is increasingly evident that excitatory neocortical neurons are quite diverse both with respect to their dendritic and axonal projection patterns well as their synaptic function. One feature that has not received significant attention is the modulation of synaptic microcircuits by the action of neurotrans-mitters such as acetlycholine, dopamine etc. At least some of these neuromodulators are neuronal cell type specific and affect neuronal microcircuits differentially thereby changing the weight of synaptic synaptic connections within a barrel-related cortical column. In the present application we will further investigate synaptic connections in a barrel-related cortical column with a particular focus on long-range intracolumnar connections that are elements of the thalamo-cortico-thalamic feedback loop. We will study synaptic microcircuits between the main thalamo-recipient layers 4, 5B and 6A. In addition, we will characterise a synaptic connection between a novel type of L4 interneuron and L4 spiny neurons that may be responsible for lateral (surround) inhibition. Because of the emerging structural and functional diversity of excitatory neocortical neurons we plan to characterise different neuronal cell types and their synaptic connections in the barrel cortex, in particular pyramidal cell types in layers 5 and 6. We will test whether different neuron types in the barrel cortex show a cell-specific response to the neuro-modulators acetylcholine, noradrenaline, dopamine and adenosine, all of which are released during different behavioural states. In this context we will also study whether L6 neurons expressing the transcription factor FoxP2 are selectively responsive to dopamine and form neuronal cortical subnetworks.

• DFG Programme: Research Units
• Subproject of: FOR 1341: Barrel Cortex Function