NMDA spikes underlie persistent activity induction.

<p><b>A.</b> Top panel: Indicative traces of transient stimulus response for a ratio of 1.1 (black) and of persistent activity corresponding to iNMDA-to-iAMPA ratio of 2.3 (grey). Bottom panel: net NMDA current the neuron receives for the ratio 1.1 (black) and 2.3 (grey). Bar indicates stimulus presentation. <b>B.</b> Box plot showing the cumulative sum of the net iNMDA during the 500 ms of stimulus presentation, for the different iNMDA-to-iAMPA ratios. <b>C–D.</b> Depolarization recorded at the basal dendrite in the absence (C) and in the presence (D) of background synaptic activity of the ‘silent’ pyramidal neuron embedded in the microcircuit, for the different ratios used. <b>E.</b> Box plot of the depolarizing potential during the last 100 ms of the stimulus (dotted box in A). Note the generation of a large plateau potential (∼16 mV) for the 2.3 ratio.