Figure 4. Principal cells have fast kinetics and small action potentials.
(A) Fifty milliseconds of spontaneous activity is shown for four principal cells (left column) and four non-principal cells (right column). In each panel, CF or BF is indicated (top left) as well as cell number (bottom left). For the non-principal cells in the right column, the subtype is indicated above the abscissa. Red and green dots respectively indicate examples of inhibitory and excitatory postsynaptic potentials. (B) Similar as A, for two labeled MSO neurons. (C) Normalized amplitude spectra of spontaneous activity traces for 12 LSO neurons, as well as six labeled MSO neurons (CF ranged from 2 to 3 kHz; including the examples in B). Between 2 and 6 s of spontaneous activity were analyzed for each neuron. Dashed horizontal line indicates 50% of maximal amplitude. (D) Stacked action potentials during ipsilateral sound presentations for a representative principal and a non-principal cell. Cell number is indicated in each panel. Respectively 42 (top) and 407 (bottom) action potentials are overlaid. (E) Scatter plot of average action potential amplitude versus the upper cut-off frequency. The latter was defined as the frequency where the high-frequency flank of the normalized magnitude spectrum falls to 50% of the maximal amplitude (dashed line in panel c). Green filled circles and black stars respectively indicate morphologically unambiguous principal cells and non-principal cells. Red crosses indicate labeled neurons that light microscopically could be principal cells or non-principal class 5 cells, but were not further evaluated at the E.M. level. Blue circles indicate whole-cell recordings from unlabeled LSO neurons.
Figure 4—figure supplement 1. Spontaneous activity of bipolar LSO neurons.
