Ultrasound exposure of the fetal chick brain: Effects on learning and memory

The article reports on the results of tests on learning and short-, intermediate-, and long- term memory in chicks at 2 days of age after exposure to ultrasound in ovo. Hybrid eggs were obtained and incubated in domestic incubators. On day embryonic day 19, the eggs were randomly assigned to experimental groups. An opening of approximately 3 cm in diameter was made in the air pocket at the blunt end of the egg; warm gel was placed on the chorioallantoic membrane; and a commercial ultrasound transducer was placed on the gel. There was a control group in which eggs were not handled at any stage, 2 sham exposure groups which were sham exposed for 5 or 10 minutes, 2 B-mode groups exposed to ultrasound for 5 or 10 minutes, and 5 Doppler groups exposed to pulsed wave Doppler ultrasound focused on the intermediate medial mesopallium (IMM) for 1 2 3 4, and 5 minutes. The exposure duration, thermal index, and mechanical index for each group were recorded. The image settings were standardized. The ultrasound machine was a current commercial unit. Following exposure, replacement shells were placed over the opening, and eggs were returned to the incubator to hatch.