In vivo wide-field calcium imaging of mouse thalamocortical synapses with an 8?K ultra-high-definition camera.

ABSTRACT: In vivo wide-field imaging of neural activity with a high spatio-temporal resolution is a challenge in modern neuroscience. Although two-photon imaging is very powerful, high-speed imaging of the activity of individual synapses is mostly limited to a field of approximately 200?µm on a side. Wide-field one-photon epifluorescence imaging can reveal neuronal activity over a field of ?1?mm2 at a high speed, but is not able to resolve a single synapse. Here, to achieve a high spatio-temporal resolution, we combine an 8?K ultra-high-definition camera with spinning-disk one-photon confocal microscopy. This combination allowed us to image a 1 mm2 field with a pixel resolution of 0.21?µm at 60 fps. When we imaged motor cortical layer 1 in a behaving head-restrained mouse, calcium transients were detected in presynaptic boutons of thalamocortical axons sparsely labeled with GCaMP6s, although their density was lower than when two-photon imaging was used. The effects of out-of-focus fluorescence changes on calcium transients in individual boutons appeared minimal. Axonal boutons with highly correlated activity were detected over the 1?mm2 field, and were probably distributed on multiple axonal arbors originating from the same thalamic neuron. This new microscopy with an 8?K ultra-high-definition camera should serve to clarify the activity and plasticity of widely distributed cortical synapses.

SUBMITTER: Yoshida E 

PROVIDER: S-EPMC5974322 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature