- Title
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Luminance Changes Drive Directional Startle through a Thalamic Pathway
- Authors
- Heap, L.A.L., Vanwalleghem, G., Thompson, A.W., Favre-Bulle, I.A., Scott, E.K.
- Source
- Full text @ Neuron
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Brain-wide detection of activity resulting from visual loom stimuli. Magenta shows pERK and green shows total ERK (tERK) in larvae subjected to looms (A) and in control larvae (B). For animals exposed to looming stimuli, heightened pERK was observed in the ventral thalamus (white outline in (C) and (C’)), telencephalon (red outline, (C) and (C’)), tectum (white outline, (D) and (D’)), and hindbrain, including within the rhombencephalic expressing region of Tg(-6.7FRhcrtR:gal4) (white and red outlines, (E) and (E’)). In animals subjected to looms, the ratio of pERK to tERK (F) was significantly elevated in each of these brain regions (control larvae in blue, larvae exposed to looms in grey, error bars indicate SEM). n = 5 for controls and 6 for loom-treated animals. Student’s t-test with Bonferroni-Holm correction for multiple comparisons, * = >0.05, ** = >0.01, *** = >0.001. A z-series of this registered brain can be found in Supplemental Movie 1. Scale bars indicate 100μm. |
Optical setup for functional imaging during visual stimulation. (A) The selective plane illumination microscope (SPIM) setup used for all experiments. (B) Animals were placed in a custom-built chamber, embedded in agarose, with light from the SPIM entering from the front and side. A 75 X 55mm screen was placed 70mm from the animal for visual stimulation. (C) An example image of the tectum taken on the SPIM setup in (A), and the corresponding watershed segmentation of this image (D). |
Tectal and thalamic responses to diverse visual stimuli. Barcoded population responses to visual stimuli are shown for the tectum (A) and the thalamus (B). For each of 28 visual stimuli (bottom) the proportion of ROIs responding 0-5 times during five presentations of each stimulus is indicated. Several of these stimuli elicited significant responses above spontaneous baseline for populations of tectal ROIs ((A), right). In contrast, only the dark looming stimulus (second bar, right side of (B)) elicited a significant population response from thalamic ROIs. Abbreviations: BW = black on white, WB = white on black, MS = medium (7 degree) spot, SS = small (3 degree) spot, HB = horizontal bar, VB = vertical bar, RC = rostral-caudal, CR = caudal-rostral, DV = dorsal-ventral, VD = ventral-dorsal, FF = full field flash. * = p<0.05, determined with 2-way ANOVA test with Dunnett test for multiple comparisons. n = 12 larvae, scale bars indicate 50μm. |
Thalamic expression in Gal4s1020t. Expression of Kaede (magenta), averaged across five animals of the genotype Gal4s1020t; UAS:Kaede, is registered against cell nuclei (green) from the Zbrain atlas (Randlett, Wee et al. 2015). (A-D) show horizontal optical sections through the brain at four dorsal to ventral positions, and selected close-ups are shown in (E-G). Gal4 expression is notable in the habenulae ((A) and (B), red outlines in (E) and (F)), the tectal neuropil ((B), white outline in (F)), sparsely in the dorsal thalamus ((C), white outline in (G)), and the ventral thalamus ((C) and (D), red outlines in (G)). All outlines are derived from the Zbrain atlas (Randlett et al., 2015). Scale bars indicate 100μm. |
Laser ablation of the thalamo-tectal tract. (A) Images of the thalamus (outline) in a Gal4s1020t;UAS:mCherry; HuC:H2B-GCaMP6f animal before (A) and after (B) laser ablation (arrow) of the tract from the thalamus to the tectum. Magenta shows mCherry and green shows GCaMP6f. Scale bars = 100μm. |