Coherence Potentials: Loss-Less, All-or-None Network Events in the Cortex
Figure 6
Spatial spread of similar waveforms depends on fast inhibitory and excitatory transmission.
(A) Reduced AMPA glutamate-receptor mediated excitation (2 µM DNQX) decreased the fraction of correlated sites at all thresholds (p<10−3, amplitude thresh ≤−2.5 SD; shown here and in B are the best-match values within a period of ±10 ms). Thresholds used in both cases correspond to the absolute amplitude values before drug. (B) DNQX also significantly reduced the amplitude similarity (i.e., amplitudes within 50% of the selected trigger) of highly correlated waveforms (R≥0.8) at all thresholds (p<10−5). (C) Reducing GABAA-receptor mediated inhibition (5 µM Picrotoxin, PTX) destroyed the sigmoidal increase in correlations with increasing amplitude, reducing the extent of correlations at high thresholds and increasing the extent of correlations at low thresholds. (D) Similar comparison as in (B) for n = 3 cultures before and in the presence of 5 µM PTX shows that amplitude similarity is also reduced under conditions of reduced fast inhibition (p<0.05). In addition, amplitude variability is increased as indicated by the larger error bars. (E) Examples of waveforms with amplitudes ≤−9 SD that are temporally clustered (<10 ms intervals) before (pre-drug) and in the presence of PTX (+PTX) demonstrate the substantial loss in waveform similarity when inhibition is reduced.