Fig. 4.

Frequency tuning of ON- and OFF-type pyramidal cells to sinusoidal AMs. A: a 4 Hz SAM stimulus and the response of an ON-type cell are shown. ON-type cells respond to the SAM upstroke. B: same as A but the response of an OFF-type cell is shown. OFF-type cells respond to the SAM downstroke. C: the vector strengths (phase locking) of ON (blue circles)-and OFF (red squares)-type neurons as a function of sinusoidal AM frequency are shown. The population average vector strength for the tested frequencies (see METHODS) initially increased and reached a maximum and then decreased for higher frequencies, which indicates band-pass tuning. For OFF-type cells, the averaged vector strength was relatively constant as a function of increasing stimulus frequency, which indicates broadband tuning. We quantified the flatness index (standard deviation of the vector strength for each frequency), our results show that this value as higher for ON-type rather than OFF-type cells (inset). D: the preferred phase (in radians) of both ON- and OFF-type neurons at frequencies from 1 to 32 Hz are shown. The ON- and OFF-type ELL cell responses were generally out of phase across the different frequencies. For both cell types, the preferred phase increased as function of increasing frequency. A linear least-squares fit to each curve allowed us to extract the axonal transmission delay from the slope.