Field events elicited by CCh are not abolished by pharmacological blockade of NMDA receptors. A, Local field and corresponding intracellular activity in a layer II non-SC elicited by 20 μm CCh. SDEs are elicited at a frequency of 0.8 Hz and have an average duration of 2.9 ± 1.1 sec.B, A single field event from A shown at expanded time scale. Individual field spikes averaged 134 ± 49 msec for three events taken from this sample and occurred at a frequency of 5.5 Hz. C, Bath perfusion of AP-5 (30 μm) did not abolish the field activity or the paroxysms in the neuron; however, the duration of the field events increased slightly to 4.0 ± 0.1 sec. D, An expanded trace from C. Individual field spikes averaged 98 ± 25 msec and occurred at a frequency of 11.3 Hz.