Spectral edge frequency as a simple quantitative measure of the maturation of electrocortical activity.
The feasibility of using spectral edge frequency (SEF) as a single quantitative measure of the maturation of electrocortical activity is demonstrated in a large number of fetal lambs studied throughout the 3rd trimester. A total of 43 electrocortical recordings obtained from 23 fetal lambs ranging from 116-140 d were subjected to power spectral analysis using the fast Fourier transform. Spectral edge frequency was calculated as the frequency below which 90% of the power resides. The SEF was found to be highly sensitive in identifying the transition between high-voltage slow-activity and low-voltage fast-activity electrocortical activity. By 125 d, the distribution of SEF clearly showed two distinct populations, a low SEF with peak values ranging from 3-9 Hz; and a high SEF (SEFH) with values ranging from 13-23 Hz. Increase in gestational age was associated with a progressive increase in SEFH, which can be described by the linear function (SEF = 0.53GA-51.3). This progressive increase in SEFH reflects the gradual acquisition of faster frequencies. In contrast, low SEF declined with age before 130 d, but then stabilized at 4 Hz throughout the rest of gestation. As a result, there was a gradual increase in the separation between SEFH and low SEF as a function of gestational age.
Szeto
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Department of Pharmacology, Cornell University Medical College, New York, New York 10021.
D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology*; D004594:Electrophysiology; D005314:Embryonic and Fetal Development / Q000502:physiology*; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D012756:Sheep / Q000502:physiology*