frequency-selective responses in Layer 4/lower Layer 3 (“1” and “2” Fig. 1); this negativity extends in a ventral direction from the current sinks in these locations, particularly the lower (Layer 4) one. Figure 2 shows Layer 4 MUA, CSD and LFP responses to tones in two different A1 penetration sites. In each site, it is clear that the three signals were largest in response to same tone frequencies, and thus shared a common BF. However, while MUA and CSD responses to tones disappeared as the tone frequency moved away from the BF, the LFP response did not.
