Investigation of neuronal mechanisms underlying orientation selectivity in rodent V1 cortex using two-photon microscopy

Despite the insights accumulated on the functions of the primary visual cortex (V1) since the groundbraking work by Hubel and Wiesel (Nobel Prize 1981), the mechanisms underlying V1 neuron tuning properties are still incompletely understood. In particular, it is still debated whether orientation selectivity is build up in a feedforward way from (non-selective) thalamic input alone, or whether intra-cortical circuitry is needed to further sharpen the response properties of V1 cells, and, if so, how this is achieved (Hansel & Van Vreesvijk, 2012).

The objective of the project is to compare the tuning properties of neuronal responses in the input (layer 4) and local processing/output stages (layers 2-3), characterizing their orientation- and contrast selectivity (Persi et al., 2011). Responses of large numbers of cells to oriented visual stimuli of various degrees of contrast will be recorded at cellular resolution using 3D-random access two-photon microscopy in rodent V1 (anesthetized rat or mouse, depending on the achievable penetration depth).

Early on, candidates are expected to get familiar with the underlying neuroscientific background. They will learn the experimental techniques and the analysis steps necessary to evaluate the acquired data working side-by-side with the supervisor. At the end of the training, candidates are expected to be semi-independent in preparation, data acquisition and data analysis.

Requirements: some experience with working with rodents, mastering of basic surgical techniques and some familiarity with a programming language (preferably Matlab). Previous experience with microscopy would be useful but is not required.

Keywords: orientation selectivity, visual cortex, two-photon microscopy, functional imaging, cortical networks, rodent, calcium imaging, balanced regime, functional architecture, connectivity

Techniques: Microscopy, calcium imaging, animal surgery, brain imaging (in animal), imaging data analysis (two-photon fluorescence microscopy)

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