EXPERIMENTAL STUDY ON AMMON'S HORN SEIZURE
Authors: Harafuji Takuro 
Published: March 2008

Both the electrical activity and the seizure caused by repetitive electrical stimulation of Amnion's horn of rabbits (partly, of dogs) under non‐anesthesia or dial‐anesthesia were recorded simultaneously at the cortex and the stimulating locus, and the spread of seizure to the cortex and the subcortical regions was recorded. Therefrom, the following results were obtained.

1. The spontaneous activity of Ammon's horn is made up in general of series of fast waves of low voltage (8–15 c./sec.) as compared with that of the cortex. Through sensory stimulation, it gets changed into regular slow waves of somewhat high voltage (3–5 c./sec.), accompanied by simultaneous changing of the cortical activity into fast waves of low voltage.

2. Through mechanical stimulation of Ammon's horn, there comes injury discharge consisting of succession of regular spike waves of high frequency, which goes spreading over to the cortex and subcortical structures.

3. Upon repetitive electrical stimulation of Ammon's horn, there occur both the primary negative response of short latency and low voltage from the ipsilateral cortex and the secondary negative response of high voltage following the former. With further continuation of stimulation, the primary response remained invariable while the secondary one gives a marked decrease in strength. By and by, there takes place now the tertiary negative response much shorter in latency together with the disorder of wave form. When stimulation gets interrupted at this time, a marked seizure dischasge will be produced successively.

4. The seizure was the continuation of spike waves of high frequency all independent of the rhythm of stimulation. It consisted both of the tonic phase represented by a succession of spike waves of high voltage and 10–30 c./sec. and the clonic phase (groups of 5–8 spike waves and pause), the time duration of sizure reading 15–40 sec.

5. The beginning of this seizure resumes either of two types: one begins with tonic phase and the other with clonic phase. These two types are also observable about the end of the seizure, that is, one ending abruptly and the other gradually.

6. With regard to the course of seizure, most frequently observed type begins with tonic phase and ends in the clonic phase; some proceeds in the clonic phase all through or goes from the clonic phase over to the tonic one. Rarely there comes a type with recurrent seizures of high voltage interposed by low potential period in between (recurrence phenomenon).

7. The occurrence of seizure stands under influence of the depth of anesthesia and intensity of stimulation, as a rule, easily evokable under light anesthesia but hardly under deep anesthesia. The optimal stimulation conditions for evokation of seizure read 5–15 V in amplitude, 7–15 c./sec. in frequency and 0.5 msec, in pulse duration. The threshold of stimulation for Ammon's horn stands always lower than that of the other regions.

8. The loci of stimulation for easy evokation of seizure are the alveus, fornix etc. of the Ammon's formation.

9. The regions disposed for spread of seizure are, Area temporalis, Area occipitalis, Area retrosplenialis granularis, lateral part of Area striata, Area parietalis 4 and 5 and, coming next in order, Area parietalis 1, 2 and 3 and Area striata. There was no spread of seizure at Area postcentralis, Area praecentralis granularis and Area agranularis, where the waves may be transformed into the waves of spontaneous activity, though rarely. (Refer to Roses paper32) for the nomenclature!)

10. There are two sorts in mode of spreading of seizure toward the cortex, that is, projection and propagation. Under physiological conditions, spreading occurs through projection, but, under abnormally heightened excitement of the cortex, automatic cortical seizure gets producible through propagation which sometimes may grow to real, generalized convulsion.

11. Seizure is evokable not only at the ipsilateral but also at the contralateral Amnion's horn simultaneously by the way of psalterium, further to spread to both sides of the subcortical regions and cerebellum.