Increased activity of pre-motor network does not change the excitability of motoneurons during protracted scratch initiation

Key points center dot A single cutaneous stimulus of adjusted intensity insufficient for scratch initiation evokes scratch when repeated at subsecond intervals. center dot The protracted scratch initiation shows that the spinal network is able to store information at subsecond time intervals. center dot Membrane depolarization and increase in excitability of motoneurons are not necessary for protracted scratch initiation. center dot The activity of the pre-motor network increases in a wind-up manner during protracted scratch initiation. Abstract Intrinsic response properties of neurons change during network activity. These changes may reinforce the initiation of particular forms of network activity. If so, the involvement of neurons in particular behaviours in multifunctional networks could be determined by up- or down-regulation of their intrinsic excitability. Here we employed an experimental paradigm of protracted scratch initiation in the integrated carapacespinal cord preparation of adult turtles (Chrysemys scripta elegans). The protracted initiation of scratch network activity allows us to investigate the excitability of motoneurons and pre-motor network activity in the time interval from the start of sensory stimulation until the onset of scratch activity. Our results suggest that increased activity in the pre-motor network facilitates the onset of scratch episodes but does not change the excitability of motoneurons at the onset of scratching.