Electroencephalography (EEG) measures ongoing electrical activity in the brain and offers a way to non-invasively characterize brain function. EEG represents a useful tool for examining cerebrocortical development in young animals, however, limited data are available among certain species including felines. Previous studies of EEGs in kittens are limited in number and vary widely with respect to how recordings were performed making broad generalizations and comparisons difficult. Various types of sedation used in different studies further complicate the picture of the developing feline brain because pharmacologic effects on the electrical activity recorded by EEG must be considered. We characterized the normal post-natal maturational process of the feline brain with regard to EEG by describing a standardized sedation protocol and recording EEGs with subcutaneous electrodes at discreet postnatal ages from two to 24 weeks of age.
Twenty five minute EEG recordings were performed in 20 cats at intervals of 2, 4, 6, 8, 12, 16, 20, and 24 weeks of age. Surface electrodes were placed on the head in a standard arrangement. The positioning of electrodes over appropriate brain regions was verified by post-mortem exam of one euthanized cat. Cats were sedated with medetomidine hydrochloride and butorphanol and reversed with atipamezole. Sedation protocol limited significant motion artifacts and was not associated with any adverse effects. Recordings were visually reviewed for the character of background electrical activity. Computer-aided analysis was used to perform frequency spectral analysis and to determine absolute and relative power of the background activity.
Analysis of background frequency, amplitude, and absolute power showed strong age-related electrical changes. Quantitative calculation of absolute power showed minimum values in two week old kittens within each frequency range reached maximum values in 6 to 8 week old cats, and declined steadily until reaching a plateau in 20 to 24 week old cats. There was no correlation between age and relative power. Our data show that age is an important consideration when interpreting EEG data in a young cat.
EEG recordings were also made in developing cats with the neurodevelopmental disorder Niemann-Pick type C. Affected cats showed abnormal spike and spike/wake activity as well as decreased normal transients compared to unaffected cats. Recordings also indicate age-related electrical changes with regard to amplitude and frequency of background activity.