Figure 4.

Motor cortex population activity characteristics during flat surface and ladder locomotion in normal conditions and during temporary inactivation of approximately one-tenth of the ventrolateral thalamus (VL) with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Phase distribution of periods of elevated firing (PEFs) of neurons during flat surface (A1 and C1) and ladder (B1 and D1) locomotion. Each row represents the PEF of one cell. A circular mark on a PEF denotes the preferred phase for cells with a single PEF per stride cycle. Neurons are rank ordered so that those with PEFs earlier in the cycle are plotted at the top of the graph. Vertical interrupted lines separate the swing and stance phases. A2, B2, C2, and D2: corresponding phase distributions of discharge frequencies. The average discharge frequency in each 1/20th portion of the cycle is color-coded according to the scale shown at the bottom of the figure. Proportion of active neurons (neurons in their PEF) in different phases of the step cycle during flat surface (A3 and C3) and ladder (B3 and D3) locomotion. The mean discharge rates of neurons during flat surface (A4 and C4) and ladder (B4 and D4) locomotion. Thin lines show means ± SE. Red crosses indicate periods of the stride when the activity during ladder locomotion was significantly higher (P < 0.05, U test) than during flat surface locomotion, 35 neurons, 40 tests.