The bioelectrical activity of an epileptogenic focus formed by applying penicillin
to the sensorimotor area of the cerebral cortex was studied in 76 male rats aged 3–29
days. A focus was formed in all the animals, but its discharges altered during development.
Primary focal discharges acquired a mature shape and duration at the age of 12 days.
No after-discharge was yet present in this phase, however, and it was not recorded
in its definitive form until the 24th day. A projected discharge, recorded in the
symmetrical site of the contralateral hemisphere, was present for the first time in
5-day-old rats, but up to the 7th day it was inconstant. This interhemispheric transmission
underwent distinct development between the 7th and 14th day after birth and at 14
days the discharge of the “mirror” focus was practically no different from the findings
in adult animals. The projected discharge in the occipital region of the “primary”
hemisphere attained its definitive shape on the 24th day.
Cerebral cortex - Epileptogenic focus - Propagation of discharges - Ontogenesis
