ELECTROCORTICAL AND HEART-RATE RESPONSE DURING VIBROACOUSTIC STIMULATION IN FETAL SHEEP

OBJECTIVE: Our purpose was to study effects of vibroacoustic stimuli o n electrocortical activity and heart rate changes in fetal sheep in ut ero. STUDY DESIGN: Seven chronically instrumented near-term fetal shee p were repeatedly stimulated by an electronic artificial larynx for 32 seconds during periods of rapid-eye-movement and non-rapid-eye-moveme nt sleep. Responses to vibroacoustic stimulation were obtained by spec tral analysis of the electrocorticogram (fast Fourier transform) and b y assessment of changes in fetal heart rate and fetal heart rate varia bility. RESULTS: During non-rapid-eye-movement sleep vibroacoustic sti mulation led to electrocorticogram desynchronization that consisted of a marked reduction of delta and theta band power (p < 0.05). A concom itant fetal heart rate decrease and fetal heart rate variability incre ase were also noted (p < 0.05). During rapid-eye-movement sleep vibroa coustic stimulation induced a significant increase in alpha and beta b and power (p < 0.05) and a slight deviation in basal fetal heart rate and fetal heart rate variability (p < 0.05). CONCLUSION: Vibroacoustic stimulation of fetal sheep provokes reproducible changes in fetal ele ctrocortical activity and heart rate patterns. These changes, which ar e not easily identifiable in gross polygraphic assessments of the feta l behavioral state, are indicative of fetal arousal.