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. Author manuscript; available in PMC: 2013 Apr 2.
Published in final edited form as: Nat Neurosci. 2012 Sep 9;15(10):1430–1438. doi: 10.1038/nn.3208

Figure 6. Short-term representations of temporal sequences in hilar neurons.

Figure 6

a, Experimental configuration. b, Responses to three trials of forward (ABCD) and reverse (DCBA) temporal stimuli sequences recorded intracellularly from three hilar cells. Vertical lines represent EPSP onset times. c, Plot of individual responses to forward and reverse sequential stimulation (black circles) in EPSP frequency space (5 forward and 6 reverse, acquired in pseudo-random order; 4 s analysis window after final stimulus in each sequence). All points contained within bounding ellipsoids (60% confidence interval, as in Fig. 2b) centered on response centroids (black asterisks). d, Plot of probabilities that forward and reverse points are significantly different by LDA. Forward and reverse sequences were significantly different (P <0.05) in 10/11 experiments (filled symbols) and not different in one experiment (open symbol). e, Plot of the effect of MK801 (10 μM) on the mean EPSP frequencies in three sequential stimulation experiments. Population responses to forward and reverse sequential stimulation were separable using LDA in control conditions in each experiment (before MK801; all P < 0.05). Sequential stimulation triggered a mean increase of 17.8 Hz in control conditions in these three experiments, not statistically different than the 16.1 Hz increase observed in the larger set of 12 sequential stimulation experiments. Sequential stimulation failed to trigger an increase in EPSP frequency in MK801 (P > 0.05). * P < 0.05. f, Plot of mean EPSP frequency across a triple recording for all forward and reverse sequences tested in one experiment. Horizontal bars indicate mean EPSP frequency for baseline period and for 4-s windows following each stimuli within the sequence. g, Vector representation of average population response to forward and reverse sequences. Responses to each stimuli were combined head-to-tail and failed to converge for fast (5 s intervals, left) sequences but converged for slow (120 s intervals, right) sequences in a different experiment. h, Plot of average separation in head-to-tail vector representations of forward and reverse sequences (similar to g) over 11 experiments. Black bars represent results from 5 s sequences; purple bar represents forward/reverse separation at the end of 120 s sequences. * P < 0.05; ** P < 0.0005. Mean ± SEM.