In the third trimester of pregnancy, the human fetus has the capacity to process perceptual information []. With advances in 4D ultrasound technology, detailed assessment of fetal behavior [] is now possible. Furthermore, modeling of intrauterine conditions has indicated a substantially greater luminance within the uterus than previously thought []. Consequently, light conveying perceptual content could be projected through the uterine wall and perceived by the fetus, dependent on how light interfaces with maternal tissue. We do know that human infants at birth show a preference to engage with a top-heavy, face-like stimulus when contrasted with all other forms of stimuli []. However, the viability of performing such an experiment based on visual stimuli projected through the uterine wall with fetal participants is not currently known. We examined fetal head turns to visually presented upright and inverted face-like stimuli. Here we show that the fetus in the third trimester of pregnancy is more likely to engage with upright configural stimuli when contrasted to inverted visual stimuli, in a manner similar to results with newborn participants. The current study suggests that postnatal experience is not required for this preference. In addition, we describe a new method whereby it is possible to deliver specific visual stimuli to the fetus. This new technique provides an important new pathway for the assessment of prenatal visual perceptual capacities.

Results and Discussion

6 Johnson M.H.

Morton J. Biology and Cognitive Development: The Case of Face Recognition. Basil Blackwell , ; 8 Pitti A.

Kuniyoshi Y.

Quoy M.

Gaussier P. Modeling the minimal newborn's intersubjective mind: the visuotopic-somatotopic alignment hypothesis in the superior colliculus. PLoS ONE. 8 : e69474 In the present study, we examined how the human fetus would respond to upright and inverted face-like stimuli in a paradigm modified from newborn research []. Based on a prior computational model of the fetal visual system during the third trimester [], we propose that the fetus will produce more head turning to the upright contrasted with the inverted stimuli, in a manner consistent with postnatal studies.

Behavioral responses to stimuli were assessed in 39 fetuses by an ultrasonographer and an experimenter, utilizing 4D ultrasound. Once comfortable, a set of 2D scans were taken comprising the fetal head position, maternal tissue thickness, fetal biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length, and fetal estimated weight. Fetal biometry measurements demonstrated normal fetal growth without fetal anomalies. All participants were then asked not to talk during the study and to remain as still as possible in order to optimize image quality. The initial 2D scan also informed the experimenter of the precise location of the fetal head prior to the presentation of the stimuli.

6 Johnson M.H.

Morton J. Biology and Cognitive Development: The Case of Face Recognition. Basil Blackwell , ; Figure 1 A Conceptual Illustration of the Stimuli Show full caption 9 Jacques S.L. Optical properties of biological tissues: a review. Phys. Med. Biol. 58 : R37-R61 10 Peters V.G.

Wyman D.R.

Patterson M.S.

Frank G.L. Optical properties of normal and diseased human breast tissues in the visible and near infrared. Phys. Med. Biol. 35 : 1317-1334 (A–D) A conceptual illustration of the stimuli utilized in the current study, depicting upright (A and B) and inverted (C and D) orientations. (A) and (C) illustrate the stimuli prior to contact with maternal tissue. (B) and (D) display the consequence of interaction with 30 mm of maternal tissue based on our equation. To calculate the expected projection size, we used the simple equation for the anisotropy of scatter [] along with a value for adipose tissue [] from the corrected version of Figure 8 (expanded view in the Corrigendum, page 2): projected diameter = tan(arccos(g)) × thickness of the tissue × 2. From the figure, g ∼0.98 for adipose, giving a diameter after 30 mm of tissue of ∼12 mm. The stimuli were projected in two orientations ("upright" and "inverted") on the maternal abdomen ( Figure 1 ). Both images were presented to the side of the fetal face, such that the stimuli were presented to the fetal retinal visual areas (left, n = 19; right, n = 20). The light was then moved across the maternal abdomen in a horizontal direction away from the fetal central visual location, for approximately 5 s at an average of 1 cm per second. This is consistent with speeds reported in newborn studies [] taking into account constraints specific to this population, i.e., the width of maternal abdomen that was accessible in order to present stimuli and the space within the womb available for the fetus