Physiological properties examined in this study and their operational definitions.
The current pulse that first elicits an action potential from a holding potential of -70 mV (see V-I measurements in Materials and Methods section).
Voltage value in the absence of DC injections 10 min after patching.
Calculated from -70 mV in response to a -20 pA current injection.
Membrane time constant
Measure obtained by fitting a single exponential to the voltage response from -70 mV to a -20 pA current injection.
First AP threshold
The point where the rising slope first exceeds 10 mV/ms at rheobase current.
First AP amplitude
The voltage difference between threshold and peak.
First AP half-width
The AP duration at half-maximal amplitude of the first action potential.
First AP delay
The time between the onset of rheobase current and the threshold of the first action potential.
The voltage difference between the first action potential threshold and the most negative voltage associated with the slower AHP following that action potential.
AHP time to peak
The time it takes from the action potential threshold to the most negative potential associated with the AHP.
1 (Last ISI/First ISI) in a recording that contains the first trace with 4 action potentials (elicited from -70 mV).
The slope of the action potential frequency vs. current injection graph.
Minimum membrane response (around -100 mV for each neuron)/steady state potential. A 10 ms region was averaged for both time points in order to obtain a more reliable value.
Time between the end of the last AHP (which is marked by the abrupt change in the slope of the rising phase of the AHP or the onset of ripple oscillations) to the end of a 500 msec, 120 pA current pulse without an action potential.