Table 1. Specific sequences of interspike interval (ISI) define normal or abnormal behavior; X normal ISI; −, shorter than normal; +, longer than normal.

normal	X X X X X
single PVB	X −+X
trigeminism	X −+X −+X
bigeminism	X −+−+X
couplet	X − − X
triplet	X − − − X
vt	X − − − −