Article Figures & Data
Figures
- Figure 1.
Recorded neurons in the LAvl region from fear-conditioned and home cage mice. fear-conditioned mice were shown to have acquired a context-fear memory by a significant increase in freezing behavior (p = 0.0018; A) and a significant decrease in moving behavior (p = 0.0015, n = 6; B). C, Cartoon illustrating the position of whole-cell recorded neurons within the LAvl region of the amygdala from fear-conditioned mice and home cage control mice. Blue markers = home cage; yellow markers = fear-conditioned trained mice; ** indicates statistical significant change.
- Figure 2.
Learning induces increased synaptic activity in a subpopulation of LAvl neurons. Raw traces of sPSCs from (A) home cage mice (HC) and (B) fear-conditioned mice (FC). C, The cumulative frequency graph of the IEI of sPSCs shows a significant left shift in fear-conditioned mice compared to home cage controls (Kolmogorov–Smirnov test p < 0.0001). D, The cumulative frequency graph of the amplitude of sPSCs shows a significant right shift in fear-conditioned mice, compared to home cage controls (Kolmogorov–Smirnov test p < 0.0001, n = 28 HC and n = 33 FC). E, A Gaussian fit to the frequency histogram of the sPSC amplitude of neurons from home cage controls shows a single peak. F, A second peak is evident in fear-conditioned mice.
- Figure 3.
Restricted expression of FTL+ neurons in thick brain slices following fear conditioning. Context fear-conditioned mice acquired a fear memory illustrated by increased (A) freezing relative to pre-shock levels (p = 0.0002) and (B) decreased movement (p < 0.0001, n = 7). C, D, Micrograph of the amygdala region of an FTL mouse stained with x-gal histochemistry following immediate shock training (non-learning control; C) and following delayed shock training (fear-conditioned; D), showing an increase in FTL+ neurons specifically in the LAvl. Scale bars in C, D: 150 µm. *** indicates statistically significant change.
- Figure 4.
FTL+ neurons in the LAvl show increases in sPSC frequency and amplitude. A, C12FDG is converted to the fluorescent product C12-fluorescein by β-galactosidase, enabling the identification of FTL+ neurons in acute brain slices. FTL+ (B) and FTL− (C) neurons identified post hoc by double labeling for β-galactosidase and biotin from intracellular recording. Representative voltage-clamp traces from (D) FTL− and (E) FTL+ neurons in the LAvl of context fear-conditioned mice. F, Cumulative frequency histogram of the IEIs of recorded sPSCs from FTL+ and FTL− neurons (Kolmogorov–Smirnov test p < 0.0001). G, Cumulative frequency histogram of the amplitudes of recorded sPSCs from FTL+ and FTL− neurons (Kolmogorov–Smirnov test p < 0.0001, n = 6 FTL− and n = 7 FTL+). Scale bars in B, C: 25 µm.
- Figure 5.
Increases in the spontaneous excitatory synaptic current event amplitude and frequency. A, Average spontaneous inhibitory PSC (sIPSC) amplitude at varying holding potentials in the presence of NBQX and APV from neurons in the mouse LA, showing a reversal potential of Cl− of approximately –50 mV (n = 7). B, The cumulative frequency graph of the IEI of sPSCs from FTL+ and FTL− neurons at –50 mV (Kolmogorov–Smirnov test p < 0.0001). D, The cumulative frequency graph of the amplitude of sPSCs at –50 mV FTL+ and FTL− neurons (Kolmogorov–Smirnov test p < 0.0001, n = 4 FTL− and n = 6 FTL+).
- Figure 6.
LAvl neurons show no differences in firing properties following fear conditioning. A, B, Representative traces from current-clamped (A) home cage (HC) and (B) fear-conditioned (FC) neurons in the LAvl. C, Mean AP count versus current injection for neurons from context fear-conditioned mice and from untrained home cage mice (n = 28 HC and n = 33 FC). Representative traces from current-clamped (D) FTL− and (E) FTL+ neurons in the LAvl of context fear-conditioned mice. F, Plot of the mean AP count versus current injection for FTL+ and FTL− neurons from fear-conditioned mice (n = 6 FTL− and n = 7 FTL+).
Tables
Untargeted neurons Targeted neurons HC FC t p FTL+ FTL− t p N 28 33 - - 7 6 - - Input resistance (MΩ) 273 ± 139 281 ± 143 1.1 0.25 177 ± 59 162 ± 86 0.73 0.73 Membrane potential (mV) –66 ± 7 –66 ± 6 0.06 0.96 –66 ± 4 –65 ± 8 0.56 0.59 Membrane time constant (ms) 51 ± 16 56 ± 16 0.5 0.60 47 ± 10 42 ± 10 1.21 0.25 Untargeted neurons Targeted neurons HC FC t p FTL+ FTL− t p N 28 33 - - 7 6 - - AP height (mv) 88 ± 7 83 ± 9 2.0 0.047 89 ± 5 85 ± 14 0.62 0.55 AP width (at 50% height, ms) 2.1 ± 0.3 2.3 ± 0.3 2.8 0.007 2.0 ± 0.3 2.1 ± 0.5 0.50 0.63 Rise time (10–90% peak height, ms) 0.6 ± 0.1 0.7 ± 0.1 3.6 0.0007 0.6 ± 0.1 0.6 ± 0.2 0.039 0.97 Decay time (100–50% peak height, ms) 1.5 ± 0.2 1.7 ± 0.2 2.3 0.028 1.5 ± 0.3 1.6 ± 0.4 0.33 0.75
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