Fig. 4: Emergence of sequential stimulus and context neuron activity suggests a storage mechanism.
From: Distinct neuronal populations in the human brain combine content and context
a, Mean cross-correlograms (six sessions) during picture presentations between entorhinal MS and either hippocampal MC neurons (each with only one significant main effect, blue) or a matched number of other hippocampal neurons (non-significant, black; left). Data are mean ± s.e.m. (solid lines and shaded areas, respectively). The peak lag time is shown in the top left. The red horizontal lines indicate significant differences (P < 0.05, cluster permutation test). Stimulus–neuron firing in the entorhinal cortex predicted hippocampal context–neuron, but not other neuron firing after approximately 40 ms. The right panel is the same as the left panel, but with the region order reversed. The hippocampal stimulus neuron firing did not predict entorhinal context–neuron firing. b, Cross-correlations of all 40 entorhinal cortex stimulus and hippocampus context neuron pairs (MS–MC) before (pre, grey) and after (post, red) the experiment. Asymmetric correlations around −40 ms were absent before but emerged during the experiment and persisted afterwards (P < 0.01, cluster permutation test). c, Boxplots (quantile 1, median, quantile 3 and whiskers (points within ±1.5× the interquartile range) are shown) of mean cross-correlations (−10 to 100 ms; see dashed lines in b) between the same neuron pairs as in panel b (left). Correlations did not differ from zero before the experiment (exp.; P = 0.29, pre in grey; Wilcoxon signed-rank test), but exceeded zero during its first (exp., violet) and second (exp., blue) halves and after its termination (post, red; all P < 0.001). Correlations of all later periods exceeded pre-experiment levels (P(pre, exp1) = 3.258 × 10−2; P(pre, exp2) = 6.625 × 10−3; and P(pre, post) = 3.106 × 10−3). Firing rates did not differ significantly before and after the experiment but were significantly lower (P < 0.01) than during each experimental half (right). ****P < 0.0001, ***P < 0.001, **P < 0.01 and *P < 0.05. All tests are two-sided and uncorrected.
