Supplementary Figure 1: Countermodulation of CA3 pyramidal neurons in rat hippocampus.

a-c) Three examples of athorny pyramidal neurons identified from rat hippocampal slices (n = 5 cells). Left, low magnification bright-field image of CA3 region where recoded neuron is stained with biocytin and indicated by green arrow. Middle panel, 2-photon image (max intensity projection) taken at 60X magnification where no thorny excrescences can be observed on any of the three example cells. Right panel, firing pattern elicited by somatic current injection, illustrating the intrinsically bursting firing pattern. d) Representative traces from a rat CA3 pyramidal cell under control conditions (no drugs) where a regular spiking firing pattern is observed close to rheobase, and the subsequent shift in intrinsic properties to burst-firing in the presence of the cholinergic agonist carbachol. e) Representative traces from a CA3 pyramidal cell of a rat under control conditions where a burst-firing pattern is observed close to rheobase and the shift in intrinsic properties to regular spiking in the presence of the cholinergic agonist carbachol. f) Left, summary data of individual data points for the input-output relationship of 8 regular spiking cells recorded under control conditions, and for 5 cells recorded in the presence of carbachol. Right, mean and SEM for control and carbachol conditions (rheobase current p = 0.2; output frequency p = 0.03, two-sided paired t-test) g) Left, summary data of individual data points for the input-output relationship of 9 bursting cells recorded under control conditions, and for 5 cells recorded in the presence of carbachol. Right, mean and SEM for control and carbachol conditions (rheobase current p = 0.49; output frequency p = 0.04, two-sided paired t-test).