Ultrasound exposure of the foetal chick brain: effects on learning and memory

Abstract

Ultrasound imaging of the brain is routinely used to monitor the development and resolution of brain lesions among premature and compromised newborn human babies. However, animal studies have shown that ultrasound can cause damage to developing foetal and neonatal tissues. In this study we investigated if ultrasound of the chick brain can lead to learning and memory impairment after hatch. We exposed the brains of chicks on day 19 of a 21 day incubation period to 5 or 10 min of B-mode, or to 1, 2, 3, 4 or 5 min of pulsed Doppler ultrasound in ovo. Learning and memory function were assessed at day 2 post-hatch. Our results show that B-mode exposure at E19 does not affect memory function. On the other hand, 2h after training, significant memory impairment occurred following 4 and 5 min of pulsed Doppler exposure at E19. In separate groups of chicks, short-, intermediate- and long-term memory was equally impaired suggesting an inability to learn. Further, the chicks were still unable to learn with a second training session 5 min after completion of the initial testing. These results demonstrate that extended exposure to pulsed Doppler ultrasound can adversely affect cognitive function in the chick when exposure occurs close to the time of hatch.

Ultrasound in the First Trimester and Earlier: How to Keep It Safe

“…One specific single specific effect has been described in various publications: a mild increase in the prevalence of non-right handedness among male children exposed to prenatal ultrasound with no other neurological, intellectual, behavioral, or physical anomalies [114][115][116]. Ultrasound has been implicated, in chicks who were insonated in ovo, in learning and memory disturbances [117]. A study failed to demonstrate a relation between ultrasound insonation in utero and decreased intellectual performance [118].…”

“…Dwell time (duration of exposure) is also of major importance: Ziskin [123] reported that among 15,973 Doppler ultrasound examinations, the average duration was 27 min (and the longest 4 h!). A study in chicken seemed to clearly implicate Doppler [117]. Chicken eggs were insonated on day 19-of a 21-day incubation period.…”

Ultrasound in Reproductive Medicine: Is It Safe?

“…This should not completely deter from the study which encourages caution. Another study which demonstrates potential harmful effects of ultrasound (when spectral Doppler is used) showed that even relatively short insonation of chick embryos to clinically relevant Doppler resulted in short-term and medium-term memory loss and a reduced ability to learn [ 82 ].…”

Ultrasonic imaging: safety considerations

“…Schneider-Kolsky et al [52] performed a study on the effects on learning and memory of ultrasound exposure of foetal chick brain. Their findings suggested that B-mode exposure on day 19 of a 21 day incubation period had no effect on learning or memory, whereas 4 -5 min of pulsed Doppler ultrasound did.…”