Fig. 2.

PA imaging of odor-evoked neural activity in the fly brain without and with cuticle. (a) Epi-fluorescence image of a GCaMP5G-expressing fly brain with the cuticle surgically removed. The dashed circle identifies the lateral location of M-mode PA recording. (b) Fractional PA amplitude changes from representative neuron layers in the glomerular region of the fly antennal lobe, showing varied response amplitudes and durations at different depths. Note that the depth in this panel is measured from the surface of the fly brain. The gray bar indicates when a puff of ethyl acetate was delivered to the fly antenna. (c) Averaged fractional PA amplitude response and the concurrently recorded fluorescence intensity response to odor stimulation with the cuticle removed. (d) Epifluorescence image of a GCaMP5G-expressing fly brain with the cuticle intact (i.e., not surgically removed). The lateral location of the M-mode PA recording is marked by the dashed circle. (e) Fractional PA amplitude changes from representative neuron layers in the fly brain with its cuticle intact. Note that the lack of response in the cuticle layer (CL) is shown here as a control. Depth in this panel is measured from the cuticle layer. The gray bar indicates the duration of the ethyl acetate delivery to the fly antennae. (f) Averaged fractional PA amplitude response from the fly brain with intact cuticle and the concurrently recorded fluorescence intensity response to odor stimulation. Although the fractional changes in PA amplitude and fluorescence intensity are comparable in magnitude, depth-resolved measurements of neural activity were made only by the PA system. (Video 1, MP4, 286 KB [URL: https://doi.org/10.1117/1.JBO.27.9.096004.s1]; Video 2, MP4, 640 KB [URL: https://doi.org/10.1117/1.JBO.27.9.096004.s2)