Changes in breathing, electrocortical and muscle activity in unanaesthetized fetal lambs with age.
Electrocortical and electro-ocular activity, breathing movements and nuchal muscle activity were recorded continuously in the unanaesthetized lamb in utero (95-135 days). Electrocortical activity was recorded simultaneously from various sites. The bi-parietal electrocorticogram gave the clearest differentiation between high- and low-voltage activity. The onset of cortical differentiation from 110 days gestation was attributed to the superimposition of high-voltage electrocortical activity at 3-10 Hz on existing low-voltage activity. Three distinct patterns in the relationships between electrocortical activity, ocular activity breathing movements and nuchal muscle activity were observed at 95-106, 107-114 and 120-135 days. Isocapnic hypoxia caused a diminution in fetal breathing from 95-135 days gestation, quantitatively greater near term. After cortical differentiation, hypoxia caused the appearance of high-voltage activity within 4 min, if low-voltage electrocortical activity was present initially. The relationship, changing with age, between electrocortical activity, breathing movements, ocular and nuchal muscle activity is discussed.
D000200:Action Potentials; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002540:Cerebral Cortex / Q000196:embryology / Q000502:physiology*; D004569:Electroencephalography; D004585:Electrooculography; D005133:Eye Movements; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D009132:Muscles / Q000196:embryology / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D012119:Respiration; D012756:Sheep / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen