Fig. 4. The loss and recovery of cutaneus trunci muscle (CTM) receptive fields. (A) A normal, complete receptive field is shown highlighted in green on the tracing of a control guinea pig, as shown in Fig. 2 and described in Materials and methods. The region of areflexia is outlined in red on the next image, 24 h post-injury to the spinal cord. Note that approximately half the total CTM receptive field is lost as a result of severe spinal cord compression. One month later, this region remains unchanged. The video image used to produce the last drawing is shown on the far right. (B) From left to right, a similar set of images to those in A. The normal receptive field (green) and the region of areflexia (red) after spinal cord injury are marked. The region of CTM recovery in response to PEG application is outlined in blue in the last drawing and demonstrates a region of recovery of CTM sensitivity comprising approximately 42 % of the original region of areflexia. (C) Note the modest region of PEG-mediated CTM recovery outlined in blue. In the magnified section shown in D, note the position of the probe within the region of recovery and the movement of the skin marker dots towards the probe (arrow). Probing outside the region circumscribed in blue did not produce CTM reflex movements, but probing in the region marked in green (above the level of the injury), did elicit contractions. E shows the actual video images collapsed in layers to produce C and D.
