Figure 3.

The ITD and ILD values at half-maximum of most units were unchanged by deactivation. A, An example ILD unit (black circles) that increased its firing rate on deactivation (orange circles) before returning to near control levels on recovery (green triangles). B, To compare the position of the function in ITD or ILD space, the minimum firing rate in each condition was subtracted and the responses were then normalized. The slopes of the normalized ILD functions in A overlapped. The position of half-maximum firing rate was almost unchanged between conditions, as shown by the dashed lines. C, The location of half-maximum firing rates for ILD (solid lines) and ITD (dashed lines) units in the control condition varied across ILD/ITD space for the population (black line). The distribution of ITD units was constrained to the midline and contralateral hemifield, while ILD units spanned both positive and negative ILDs. The distribution of half-maximum firing rates on contralateral IC deactivation (orange line) and recovery (green line) were almost unchanged relative to control. D, Data for the individual units represented in (C) showing their half-maximal ILD or ITD values in the control and deactivated conditions. Most units were unchanged by deactivation. ILD units (black filled circles) showed greater variance about the line of identity than ITD units (blue open circles).