1. A method for identifying a contra-ictal condition for a subject, the method comprising: obtaining a physiological signal dataset from the subject; generating an N-dimensional feature vector for different time points of the physiological signal dataset; identifying a grouping of feature vectors or a region of an N-dimensional feature space that is substantially free from ictal activity and is separated in time from subsequent ictal activity by a computed or predetermined time period; and using the grouping of feature vectors or region of the N-dimensional feature space to identify a contra-ictal condition of the subject.