The Maturation Phenomenon, described by Ito et al. in 1975 [3) on the basis of his to logical observations in the hippocampus as well as other portions of the cerebral hemisphere, refers to the hours or days of delay in the development of pathological changes in various parameters of ischemic injury following the restoration of blood flow to the ischemic brain. There is a direct relationship between the intensity of ischemic insult and the speed and rate of maturation of ischemic injury, a lesser intensity being associated with slower and less severe development of the lesions. The delayed neuronal death of CAl pyramidal cells of the hippocampus [8) is a classic example. In the cerebral cortex, with increasing intensity of the ischemic insult, the maturation phenomenon of ischemic injuries intensifies, seamlessly, from less exten sive to more extensive disseminated selective neuronal necrosis (DSNN), and then further to cerebral infarction upon reaching a critical threshold [1,2,4,6,7). We also have found that following ischemic insults just under the threshold level required to induce infarction, only disseminated selective neuronal necrosis (DSNN) progresses, while following ischemic insults at the threshold level, initially only DSNN develops, followed by the evolution of a gradually enlarging infarcted focus [5, 7). The reporting of this phenomenon boosted research in the field, as it became evi dent that ischemic damage is not a sudden event, but a process potentially susceptible to therapeutic intervention.

Many nerve cells of the brain which are not killed outright may suffer delayed death or recovery after ischemic insult. This fact has led to the concept of "maturation phenomenon" of neuronal injuries. Since the 1st International Symposium on Maturation Phenomenon in 1990, new developments, particularly in molecular biology, have been rapidly bringing new information about molecular nature and mechanisms of cell death. This book contains the presentations of the 2nd International Symposium held in Tokyo in April 1996. The latest developments in maturation phenomenon and the present status of investigation are described and further stimulation of research in this field is provided.

The maturation phenomenon, first described by Ito et al. in 1975, refers to postischemic changes that develop hours or days after an ischemic insult. The delayed neuronal death of CA1 pyramidal cells of the hippocampus is a classic example. The report of the phenomenon boosted research in the field, as it became evident that ischemic damage is not a sudden event, but a process potentially susceptible to therapeutic intervention. Since then a growing number of studies have improved our knowledge on mechanisms of cell death and recovery. This volume contains the presentations of the 4th international symposium, held in New Orleans in October/November 1999, grouped in sections covering apoptosis and/or necrosis, neuronal recovery vs. death, and protection against infarction. It outlines the present status of investigations and provides further stimulation for research in this field.

It has been well recognized that following an ischemic insult many nerve cells of the brain are not killed outright, but may suffer a "delayed neuronal death" or even recover. This led to the concept of "maturation phenomenon" with its main implication that the maturation of ischemic lesions may provide a "window of opportunity" i.e. a period of time when the injury to neuronal elements is still reversible, and during which an application of proper therapeutic measures might be successful. The symposium on Maturation Phenomenon in Cerebral Ischemia was the first international meeting focussed primarily on this subject and the resulting publication contains presentations and discussionsby prominent researchers engaged in this field. This book should stimulate further research on potential of brain tissue for recovery, and particularly with regard to a functional recovery of neurons suffering from chronic ischemic injury.

Fifth International Workshop April 28-May 1, 2002 Banff, Alberta, Canada