Fig. 3: dHPC^→NAc neurons carry enhanced and more reliable spatial information.

a Schematic of dual-color projection neuron imaging method. Thy1-GCaMP6s mice were injected with AAVrg-Cre in the medial NAc and DIO-mCherry in dHPC. Representative coronal brain slice showing axonal mCherry expression in NAc (AP −1.3; left). Representative coronal brain slice stained with DAPI (blue) of dHPC; scale bar represents 1 mm (second left). Field of view of one sample experiment showing Thy1-GCaMP6s expression in green and mCherry expression of putative NAc-projecting neurons in red; outlines show detected components used for analysis (right). b Raw (F), denoised and deconvolved (C) and event (S) traces from two representative neurons; red traces indicate mCherry co-expression (dHPC^→NAc). c Excerpt from one representative recording session showing behavioral activity (top) and denoised neural activity of identified place cells (bottom). White vertical lines mark new laps. Traces are ordered according to place fields (red: dHPC^→NAc; green: dHPC^-). Black traces are example neurons shown in d, e. d, e Spatial activity of one neuron without (d) and with (e) mCherry co-expression over one session. f–k NAc-projecting neurons (red) contain a higher proportion of place cells (f, χ²(1, 5372) = 6.364, P = 0.0116); these place cells contain more spatial information per second (g, Mann-Whitney U = 161846, P < 0.001), show increased sparsity (h, Mann-Whitney U = 160810, P < 0.001), higher reliability (i, probability of firing maximally within their place field per lap; Mann-Whitney U = 149324.5, P = 0.0112), higher place field stability (j lap-to-lap correlations; Mann-Whitney U = 162556, P < 0.001), and higher in-place field activity (k Mann-Whitney U = 150460.0, P = 0.0066). n = 6 mice, 19 imaging sessions, 5372 (inc. 444 mCherry-coexpressing) neurons, 1750 (inc. 169 mCherry-coexpressing) place cells; all tests two-tailed. Data in g–k: n = 5/3 mice with place cells. Solid lines in violin plots represent median values and dashed lines quartiles. Bottom panels in g–k show median difference computed from 5000 bootstrapped resamples (black dot, median; black ticks, 95% confidence interval; filled curve, sampling-error distribution). *P < 0.05, **P < 0.01, ***P < 0.001. Source data are provided as a Source Data file.