( l pattern generator explained Lanuza....)Salk researchers make fast strides towards understanding how our body controls walking

V1 neurons are so-called interneurons that relay electrical signals between nerve cells in the spinal cord,and motor neurons, the nerve cells that cause muscles to contract.

To explore whether V1 neurons actually contribute to the CPG, Goulding and his colleagues performed electrophysical studies on isolated spinal cords. They found that, while normal spinal cords showed a standard pattern of activity that mimics walking, the rhythmic pattern in spinals cords lacking functional V1 neurons had slowed to a crawl.

"From what we knew about these cells, we were a bit puzzled at first because we had expected to see a loss of coordination," said Goulding. "But after delving into the circuitry further, it made perfect sense. Once excited, motor neurons tend to stay "on" for long periods of time and need to be actively turned off. That is exactly what V1 neurons are doing," explained Goulding. In order to initiate the next step, each burst of motor neuron activity needs to be switched off. Switching off motor neurons more quickly, speeds up the stepping movements, allowing animals to walk, run, or swim faster.