Note: This figure was published in Science, 159: 894, 1968. It shows the location of cells recorded in and around the midbrain central gray at frontal levels 2.0 and 1.0. Cells which fired only during fighting are shown as stars. Other cells which fired maximally during fighting are shown as closed circles. Other cells are shown as open circles. Area from which hissing was obtained during electrical stimulation is stippled. All cells have been projected onto the same side of the brain for illustration purposes. See Figure 4 on page 19 for further details.