Electrophysiological properties of IMS, FS, and RS neurons
| Firing frequency (Hz) | fAHP (mV) | AP duration (msec) | Refractory period (msec) | ISI1/ISI2 | |
|---|---|---|---|---|---|
| IMS | 7.4 ± 0.5 | 0.2 ± 0.7 | 3.5 ± 0.1 | 13.7 ± 1.3 | 0.8 ± 0.02 |
| n = 57 | n = 54 | n = 56 | n = 26 | n = 47 | |
| FS | 24 ± 1.0 | −9.1 ± 0.4 | 1.9 ± 0.1 | 5.9 ± 0.5 | 0.9 ± 0.01 |
| n = 41 | n = 40 | n = 41 | n = 23 | n = 40 | |
| RS | 12.1 ± 0.5 | 0.7 ± 0.6 | 2.6 ± 0.1 | 15.0 ± 1.3 | 0.6 ± 0.02 |
| n = 58 | n = 57 | n = 58 | n = 24 | n = 56 |
The mean firing frequency, fAHP, action potential duration, refractory period, and ratio of first to second interspike interval (ISI1/ISI2) were determined for neurons in each of the three firing categories. The firing frequency was determined from the maximal number of spikes evoked by a suprathreshold 600 msec depolarizing current step. The fAHP was measured from threshold to maximal hyperpolarization, after the first spike in the train. Action potential duration was measured at half amplitude. The refractory period was defined as the interstimulus interval between two identical depolarizing stimuli necessary for a neuron to fire an action potential, during the second pulse, with an amplitude at least 90% of that elicited during the first pulse. To calculate the ISI1/ISI2, the time between the first and second spikes in a train is expressed as a percentage of the time between the second and third spikes in the train. Values presented are mean ± SEM; n indicates total number of neurons examined. All five properties are significantly different between RS and FS neurons (p < 0.01; Student’s t test).