The 2+2-Signature and the 1+1-Matrix-Brane
  We discuss different aspects of the 2+2-signature from the point of view of the quatl theory. In particular, we compare two alternative approaches to such a spacetime signature, namely the 1+1-matrix-brane and the 2+2-target spacetime of a string. This analysis also reveals hidden discrete symmetries of the 2+2-brane action associated with the 2+2-dimensional sector of a 2+10-dimensional target background. 
J. A. Nieto