Fig. 5

Regional differences in synapse formation in the pallium of learner fish. (A, Left) Map of lost (cyan) or gained (yellow) synapses in the left pallium following TFC for L fish in dorsal view (highlighted in inset, midline to the right). Results from each fish were registered onto a canonical fish prior to pooling (SI Appendix, Fig. S7). (Middle) Coronal view of pooled L results shows a DB plane (red) that optimally divides the left pallium into two regions of differential synapse change: dorsomedially, synapse loss predominates; ventrolaterally, synapse gain predominates (region highlighted in inset; midline to the left). (Right) Slightly tilted 3D coronal view of DB plane for L fish (red) shown against the outline of the canonical zebrafish brain (gray; M: midplane). (B) Dorsal (highlighted in inset cartoon, medial to the right), medial, and lateral views of voxelized aggregate synaptic data in L and NL fish. Each voxel represents a region with predominant synapse loss (cyan) or gain (yellow) following TFC. The DB plane (red) derived from L separates a region of predominant synapse gain (ventrolaterally) and loss (dorsomedially) in L; the same plane does not separate loss and gain in NL. (C) Synapse fractional gain analysis for each group reveals that learners have gained significantly more (∼30%) synapses ventrolaterally versus dorsomedially relative to the DB plane (***P < 0.005, Wilcoxon test). PL, NL, and control groups do not show a significant difference in synapse gain between the two sides of the DB plane (P > 0.05, Wilcoxon test). (D) Fractional change in synapses (gained minus lost) is significantly higher ventrolaterally versus dorsomedially in L and PL (*P < 0.05, Wilcoxon test) but not in any other groups (P > 0.05, Wilcoxon test). (E) The ratio of PSD-95.FingR-GFP fluorescence intensity per synapse before and after TFC (I_t2/I_t1) is negligibly different in medial versus lateral regions in L (∼1% difference), CS, and NS (≤5% difference, *P < 0.05, Wilcoxon test), and in US, PL, and NL (<4%, P > 0.05, Wilcoxon test). (Scale bar, 20 µm.) Voxel dimensions in B, 10 µm. n = 11 L, 6 PL, 11 NL, 11 US, 11 NS, and 11 CS fish. Data available at https://doi.org/10.25551/1/1-1Z06 (60).