Chronic two-photon imaging of entire cortical columns in awake mice using microprisms

In the scientific quest to unravel the neural basis of many perceptual and cognitive functions, animal models are very important in complementing the findings obtained in non-invasive human neuroimaging studies. Furthermore, even though there are many species-specific aspects to cognition (e.g., human language), for those perceptual-cognitive functions that do generalize across species, animal models often offer the only possibility to test decisively between alternative hypotheses. Further, development of animal research methods is advancing at astounding speed. Two-photon calcium imaging is a relatively new method that allows simultaneous recording from large (~hundreds) populations of neurons, however, the method has been limited to recording from limited number of cortical layers at a time, and it has not been possible to record the neural populations over extended periods of time, which would be very useful in studies of, for example, the neural basis of various types of learning.

With the method recently published by Andermann et al. (2013) it is now possible to record extensive populations of neurons simultaneously from all six cortical layers over extended periods of time, even for months. The authors surgically implanted glass microprisms in somatosensory and visual cortical areas of mice, which then allowed chronic two-photon imaging of hundreds of neurons and from all layers simultaneously, in awake animals. The authors point out that their novel methodology, when combined with advances in genetic, pharmacological, and optogenetic methods (using which individual neurons in a population can be selectively suppressed and excited), can considerably expand the highly exciting capabilities offered by two-photon imaging in animal-model studies of the neural basis of perceptual and cognitive functions.

Reference: Andermann ML, Gilfoy NB, Goldey GJ, Sachdev RNS, Wölfel M, McGormick DA, Reid RC, Levene MJ. Chronic cellular imaging of entire cortical columns in awake mice using microprisms. Neuron (2013) e-publication ahead of print. http://dx.doi.org/10.1016/j.neuron.2013.07.052