Methods used in the lab
Activity correlation imaging
(a) Stack of raw fluorescent images. (b) Correlation maps corresponding to the planes in (a). The maps were calculated using the activity pattern from the outlined glomerulus in (a). (c) Maximum projection of correlation maps from 18 slices. (d) Multi-color representation of the network using correlation maps from 190 reference regions.
For the analysis of neuronal networks it is an important task to relate the neurons' activities to their morphology. Activity correlation imaging is a novel method to simultaneously visualize the activity and morphology of populations of neurons. To this end we first stain the network's neurons using a membrane-permeable Ca2+ indicator (e.g., Fluo-4/AM) and record their activities. We then exploit the recorded temporal activity patterns as a means of intrinsic contrast to visualize individual neurons' dendritic morphology. The result is a high-contrast, multicolor visualization of the neuronal network. This method, yielding both functional and structural information of neuronal populations, will open up unprecedented possibilities for the investigation of neuronal networks.
The figure shows activity correlation imaging in the Xenopus olfactory bulb as an example. Using a custom built fast line illumination confocal microscope, we measured the spontaneous activties of the mitral/tufted cells in a tissue volume of approximately 460x230x45 µm3 within 500 ms per stack (18 slices). By applying our algorithm we were then able to visualize the projections of the mitral/tufted cells into the olfactory glomeruli.
Demonstration routine for MATLAB
Sample data for MATLAB demonstration (large download: 35MB!)
For more information: Junek et al. (2009)