Figure 4.

Long-range horizontal connections underlying long-range LFP responses. A, Evoked LFPs over cortical distance after whisker C2 stimulation (black) were almost abolished at electrodes 5–8 after cortical transection between electrodes 4 and 5 (green), an effect not observed after an earlier transection parallel to the electrode array (purple). Inset, Nissl-based micrograph of transection (arrows). B, C, Representative example of labeled border-crossing, long-range horizontal connections after BDA microinjection roughly above A2 barrel and surrounding septa. B, Delineated axons from three consecutive cortical slices from layers 2–3 superimposed on the corresponding layer IV scheme containing barrels (black) and cortical borders (gray). C, Photomicrograph from the same BDA injection illustrating several long-range axons radiating at least 2500 μm away from the injection site, spanning across VCx (arrows highlight one of the axons). Scale bars, 500 μm.