THE ROLE OF THE PIRIFORM CORTEX IN KINDLING
Section snippets
INTRODUCTION
The piriform cortex (PC) is the largest area of the mammalian olfactory cortex which is characterized by direct input from the olfactory bulb (see review by Shipley et al., 1995). The PC extends over a considerable distance of the lateral and ventral surface of the rat forebrain [Fig. 1(A)]. In the literature, “primary olfactory cortex” (because the PC receives the main projection from the olfactory bulb) or “prepiroform cortex” have been used as a synonym for the PC (for discussion, see
FUNCTIONAL ANATOMY OF THE PC
The PC of the rat extends over an anterior-posterior distance of some 5 mm at the rostral and lateral surface of the forebrain just ventral to the rhinal fissure (Paxinos and Watson, 1986). Although the cell layers and morphology are generally similar in the whole PC, it is sometimes divided into an anterior and a posterior part. The borderline between anterior and posterior PC is defined tentatively by the disappearance of the lateral olfactory tract (LOT) on the PC surface and a concomitant
SPECIAL PHYSIOLOGICAL FEATURES OF THE PC
The PC has gained some attention because of striking differences in information processing and simplicity of microcircuitry, compared to neocortical areas. In contrast to the topic projection usually found in neocortical connections, the input to the PC is rather diffuse. Anatomical studies have shown that fibers from the olfactory bulb have a broad terminal field with many en passant synapses (Devor, 1976; Ojima et al., 1984). Accordingly, the representation of physiological (odors) or
Epilepsy, Epileptic Seizures, and the Kindling Model of Epilepsy
Epilepsy or the epilepsies are common disorders of the brain affecting at least 50 million people worldwide. Clinically, the epilepsies are characterized by recurrent epileptic seizures, either convulsive or non-convulsive, which are caused by partial or generalized epileptogenic discharges in the brain. Basic research on the various types of epilepsy focuses on the cellular and molecular mechanisms of the ways in which epileptic attacks inherently start, regenerate, arrest spontaneously, or
CONCLUSIONS
Several clinical and experimental studies have demonstrated that the structures of the limbic system show a low threshold for generation of epileptic activity. Unlike other cortical areas, the limbic (“temporal”) lobe shows a highly directional organization of the corticocortical association fiber system. Olfactory cortex pyramidal neurons project through a rostral-to-caudal-directed associative fiber system all over the PC and entorhinal cortex (Haberly and Price, 1978). Although it had been
Acknowledgements
Supported in part by grants from the Deutsche Forschungsgemeinschaft. We thank Dr Holger Lehmann for help in providing illustrations on GABA immunohistochemistry in piriform cortex, Dr Elisabeth Liebler (Department of Pathology, School of Veterinary Medicine, Germany) and Ursula Brakensiek for help with the microphotography, and Prof. Hermann Stefan (Department of Neurology, University of Erlangen-Nürnberg, Germany) for providing the MRI and helpful discussions.
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