cortex

Project number:

203

Project title:

Adult cortical plasticity induced by experimental visual cortex lesions – the possible role of the horizontal fibre systems

Project supervisor:

Ulf T. Eysel and Thomas Mittmann

Project description:

As a model of focal brain damage, we apply focal laser lesions in the visual cortical network of young adult rats. The subsequent neuronal reorganization requires changes in synaptic weight by use-dependent mechanisms like long-term potentiation (LTP) and long-term depression (LTD) to modify functional connections. We have shown a transient and locally restricted increase in LTP but not LTD at excitatory ascending inputs in layers 2/3 after lesions in the rat visual cortex using an ex vivo-in vitro approach and extra- and intracellular recording techniques. However, remapping of the cortical network requires flexibility not only in ascending but also in horizontal connections. Therefore, in the planned project, we want to study possible changes in synaptic plasticity (LTP and LTD) of the excitatory horizontal fibre system with a similar methodical approach. This study is motivated by the desire to understand the basic mechanisms of cortical reorganization and to elucidate functional states following lesions that might be useful for improving post-lesion rehabilitation.
Animals are sacrificed at different survival times between 2 and 14 days post lesions. In the ex vivo-in vitro approach brain slices that contain the lesions are investigated with intracellular recordings using sharp as well as patch-clamp electrodes. Recordings are made from pyramidal cells in layers 2/3. Theta burst stimulation is applied lateral to the recording sites to elicit LTP and low frequency stimulation (1 Hz) to elicit LTD at synapses of the horizontal fibre system. The ascending inputs are used to test for specificity of the effects induced in the horizontal system. Further tasks would be pharmacological characterization of the underlying receptor types and discrimination of pre- and postsynaptic mechanisms.

Possible cortex partners for rotation:

Oslo, aspects of glutamatergic transmission and excitotoxicity related to our lesion model
Helsinki, hyperexcitability related to our lesion model
London and Prague, possibilities to integrate stem cells into recovery processes using our lesion model