Fig 3.

Paired stimulation facilitates network burst probability. (A) Latency profiles of thalamo-cortical (TC), L1 and P network bursts in an exemplary slice showing shortened P burst latencies around the intersection of TC and L1 burst latency profiles (arrow). (B) Summary analysis of latency shortening by paired stimuli. For each slice, the recording site closest to the intersection of TC and L1 burst latency profiles, as shown exemplarily in A, was selected; the difference between L1 and TC burst latencies at that site (Lat_L1 and Lat_TC, respectively) was used as the abscissa value and the difference (latency of P bursts) – (latency of TC or L1 bursts, whichever was smaller), termed Δ latency, was used as the ordinate value. Filled circle and error bars represent the median and inter-quartile ranges, respectively. (C) Individual trials of bursts elicited by TC, L1 and paired stimuli. Signals from all 16 electrodes are depicted for each trial (top row corresponds to electrode closest to cortical stimulation site). Data were smoothed by a low-pass filter (–3dB frequency 200 Hz) for better visibility. Grey scale is identical for all plots. TC and L1 stimulation intensities were 10 and 32 µA, respectively. (D) Plots of P(Bu) vs recording site for the data shown in C. Dashed line in right-most plot is P(Bu)_P,exp, the P(Bu) for paired stimuli that would be expected in the absence of any interaction between TC and L1 afferents. (E) Plot of P(Bu)_Pvs P(Bu)_P,exp of all experiments in data set. Each point represents P(Bu) averaged across recording sites for a specific pair of stimulation strengths. Magenta point at coordinate (0.53, 1.0) corresponds to the experiment shown in C and D. Note that the overwhelming majority of points is at or close to coordinate (1,1) because of the supra-threshold nature of most stimuli in control. P, paired; S, spontaneous; P(Bu), probability of network burst; L1, layer 1; MUA, multi-unit activity.