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The effect of electrical stimulation on behavioral states in the fetal lamb
Brachial nerve stimulation at two frequencies (0.01 and 0.05 pulse per second, pps) with the fetus in either low-voltage electrocortical activity with eye movements or high-voltage electrocortical activity without eye movements was studied in five chronically catheterized fetal lambs at 130 to 140 days' gestation. During low-voltage electrocortical activity with eye movements, there were slight alterations in electrocortical state and electromyographic activity at 0.01 pps. At 0.05 pps these electromyographic changes were enhanced above those expected as a result of state changes but returned to control values during the recovery period. During high-voltage electrocortical activity without eye movements, the state changes were much more dramatic, while electromyographic activity increased significantly only at 0.05 pps. It was of note that in both high- and low-voltage electrocortical activity the fetal heart rate changed only during the recovery period at 0.05 pps. It is concluded that fetal behavioral state influences the interpretation of biophysical measurements in the fetus and that the effect of stimulation is more pronounced if applied when the fetus is in high-voltage electrocortical activity without eye movements.
Brachial nerve stimulation at two frequencies (0.01 and 0.05 pulse per second, pps) with the fetus in either low-voltage electrocortical activity with eye movements or high-voltage electrocortical activity without eye movements was studied in five chronically catheterized fetal lambs at 130 to 140 days' gestation. During low-voltage electrocortical activity with eye movements, there were slight alterations in electrocortical state and electromyographic activity at 0.01 pps. At 0.05 pps these electromyographic changes were enhanced above those expected as a result of state changes but returned to control values during the recovery period. During high-voltage electrocortical activity without eye movements, the state changes were much more dramatic, while electromyographic activity increased significantly only at 0.05 pps. It was of note that in both high- and low-voltage electrocortical activity the fetal heart rate changed only during the recovery period at 0.05 pps. It is concluded that fetal behavioral state influences the interpretation of biophysical measurements in the fetus and that the effect of stimulation is more pronounced if applied when the fetus is in high-voltage electrocortical activity without eye movements.