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Abstract

We describe a miniaturized head−mounted multiphoton microscope
and its use for recording Ca2 transients from the somata of
layer 2/3 neurons in the visual cortex of awake, freely moving rats.
Images contained up to 20 neurons and were stable enough to
record continuously for >5 min per trial and 20 trials per imaging
session, even as the animal was running at velocities of up to 0.6
m/s. Neuronal Ca2 transients were readily detected, and responses
to various static visual stimuli were observed during free
movement on a running track. Neuronal activity was sparse and
increased when the animal swept its gaze across a visual stimulus.
Neurons showing preferential activation by specific stimuli were
observed in freely moving animals. These results demonstrate that
the multiphoton fiberscope is suitable for functional imaging in
awake and freely moving animals