Figure 1.

Transcranial two-photon imaging of fluorescently labeled pyramidal cortex neurons in the living mouse brain. (a) This image illustrates a subset of YFP-expressing L5 pyramidal neurons that extend their apical dendrites to L1 in the barrel cortex of a one-month-old YFP-H transgenic mouse. Scale bar: 50 μm. Modified, with permission, from [36]. (b) A CCD camera image of the brain vasculature as observed in the mouse cortex using the thinned skull method of preparation. Scale bar: 1 mm. (c–d) Dendritic spine dynamics of L5 pyramidal neurons in the barrel cortex of a YFP-H line adolescent mouse. (c) A low-magnification 2D projection from a 3D stack of dendritic branches and axons. Scale bar: 10 μm. (d) A higher magnification view of the dendritic segment demarcated in the white box in (c). Two images of the same dendritic segment, taken at the ages of weeks (w) 4 and 6, respectively, reveal spine elimination (green arrowheads), spine formation (red arrowheads) and filopodia (asterisks). Scale bar: 2 μm. (c) and (d) are modified, with permission, from [27]. (e) En passant bouton dynamics of intracortical axons from L2/3 and L4 neurons in the barrel cortex of a GFP-M transgenic mouse. Two images of the same axon segment, taken at P86 and P94, respectively, reveal the addition of an en passant bouton (red arrowhead). Scale bar: 10 μm. (f) Terminaux bouton dynamics of thalmocortical axons in the barrel cortex of a GFP-M transgenic mouse. Two images of the same axon segment, taken on P124 and P128, respectively, reveal the addition of a terminaux bouton (red arrowhead). Scale bar: 5 μm. (e) and (f) are modified, with permission, from [59]. (g) Dendritic tip dynamics of layer 2/3 interneurons in the visual cortex of a GFP-S transgenic mouse. Two images of the same dendrite, taken at the age of weeks 11 and 13, respectively, reveal elongation of a dendritic tip (pointed by 3 red arrowheads). Scale bar: 5 μm. Modified, with permission, from [58].