The Role of Temporal Synchrony in the Facilitation of Perceptual Learning during Prenatal Development

This study explored the critical features of temporal synchrony for the facilitation of prenatal perceptual learning with respect to unimodal stimulation using an animal model, the bobwhite quail. The following related hypotheses were examined: (1) the availability of temporal synchrony is a critical feature to facilitate prenatal perceptual learning, (2) a single temporally synchronous note is sufficient to facilitate prenatal perceptual learning, with respect to unimodal stimulation, and (3) in situations where embryos are exposed to a single temporally synchronous note, facilitated perceptual learning, with respect to unimodal stimulation, will be optimal when the temporally synchronous note occurs at the onset of the stimulation bout. To assess these hypotheses, two experiments were conducted in which quail embryos were exposed to various audio-visual configurations of a bobwhite maternal call and tested at 24 hr after hatching for evidence of facilitated prenatal perceptual learning with respect to unimodal stimulation. Experiment 1 explored if intermodal equivalence was sufficient to facilitate prenatal perceptual learning with respect to unimodal stimulation. A Bimodal Sequential Temporal Equivalence (BSTE) condition was created that provided embryos with sequential auditory and visual stimulation in which the same amodal properties (rate, duration, rhythm) were made available across modalities. Experiment 2 assessed: (a) whether a limited number of temporally synchronous notes are sufficient for facilitated prenatal perceptual learning with respect to unimodal stimulation, and (b) whether there is a relationship between timing of occurrence of a temporally synchronous note and the facilitation of prenatal perceptual learning. Results revealed that prenatal exposure to BSTE was not sufficient to facilitate perceptual learning. In contrast, a maternal call that contained a single temporally synchronous note was sufficient to facilitate embryos’ prenatal perceptual learning with respect to unimodal stimulation. Furthermore, the most salient prenatal condition was that which contained the synchronous note at the onset of the call burst. Embryos’ prenatal perceptual learning of the call was four times faster in this condition than when exposed to a unimodal call. Taken together, bobwhite quail embryos’ remarkable sensitivity to temporal synchrony suggests that this amodal property plays a key role in attention and learning during prenatal development.

Elevated progesterone in yolk as a moderator of prenatal and postnatal auditory learning in bobwhite quail

Recent studies have established that yolk hormones of maternal origin have significant effects on the physiology and behavior of offspring in birds. Herrington (2012) demonstrated that an elevation of progesterone in yolk elevates emotional reactivity in bobwhite quail neonates. Chicks that hatched from progesterone treated eggs displayed increased latency in tonic immobility and did not emerge as quickly from a covered location into an open field compared to control groups. For the present study, three experimental groups were formed: chicks hatched from eggs with artificially elevated progesterone (P), chicks hatched from an oil-vehicle control group (V), and chicks hatched from a non-manipulated control group (C). Experiment 1 examined levels of progesterone with High Performance Liquid Chromatography/tandem Mass Spectroscopy (HPLC/MS) from prenatal day 1 to prenatal day 17 in bobwhite quail egg yolk. In Experiment 2, bobwhite quail embryos were passively exposed to an individual maternal assembly call for 24 hours prior to hatching. Chicks were then tested individually for their preference between the familiarized call and a novel call at 24 and 48 hours following hatching. For Experiment 3, newly hatched chicks were exposed to an individual maternal assembly call for 24-hrs. Chicks were then tested for their preference for the familiarized call at 24 and 48-hrs after hatch. Results of Experiment 1 showed that yolk progesterone levels were significantly elevated in treated eggs and were present in the egg yolk longer into prenatal development than the two control groups. Results from Experiment 2 indicated that chicks from the P group failed to demonstrate a preference for the familiar bobwhite maternal assembly call at 24 or 48-hrs after hatch following 24-hrs of prenatal exposure. In contrast, chicks from the C and V groups demonstrated a significant preference for the familiarized call. In Experiment 3, chicks from the P group showed an enhanced preference for the familiarized bobwhite maternal call compared to chicks from the C and V groups at 24 and 48-hrs after hatch. The results of these experiments suggest that elevated maternal yolk hormone levels in pre-incubated bobwhite quail eggs can influence auditory perceptual learning in embryos and neonates.^

Effects of Altered Prenatal Sensory Stimulation on Postnatal Contingency Learning in Bobwhite Quail Neonates (Colinus Virginianus)

Preterm infants are exposed to high levels of modified early sensory experience in the Neonatal Intensive Care Unit (NICU). Reports that preterm infants show deficits in contingency detection and learning when compared to full-term infants (Gekoski, Fagen, & Pearlman, 1984; Haley, Weinberg, & Grunau, 2006) suggest that their exposure to atypical amounts or types of sensory stimulation might contribute to deficits in these critical skills. Experimental modifications of sensory experience are severely limited with human fetuses and preterm infants, and previous studies with precocial bird embryos that develop in ovo have proven useful to assess the effects of modified perinatal sensory experience on subsequent perceptual and cognitive development. In the current study, I assessed whether increasing amounts of prenatal auditory or visual stimulation can interfere with quail neonates’ contingency detection and contingency learning in the days following hatching. Results revealed that augmented prenatal visual stimulation prior to hatching does not disrupt the ability of bobwhite chicks to recognize and prefer information learned in a contingent fashion, whereas augmented prenatal auditory stimulation disrupted the ability of chicks to benefit from contingently presented information. These results suggest that specific types of augmented prenatal stimulation that embryos receive during late prenatal period can impair the ability to learn and remember contingently presented information. These results provide testable developmental hypotheses, with the goal of improving the developmental care and management of preterm neonates in the NICU setting.