The functional foetal brain: A systematic review and meta-analysis.

This work examines functional magnetic resonance imaging and foetal magnetoencephalography studies that measure foetal auditory and visual evoked responses during the third trimester of gestation. A prior study (Dunn et al., 2015) found inconsistent results in healthy human samples due to substantial methodological variability. The updated review also includes studies where participants are at risk of, or are already showing, atypical development. This gives a broader understanding of how and when sensory abilities develop and in which way their development is influenced by foetal and maternal risk factors. 46 studies were included from initial 528 reports. They demonstrate that auditory stimuli activate primarily temporal areas whereas visual stimuli activate only frontal regions. They also show that latencies and amplitudes of foetal evoked responses are comparable between both modalities, but are negatively affected by atypical development. Several stimulus and paradigm characteristics further moderate latency and amplitude values modality specific. Due to insufficient data regarding the gestational age, it remains inconclusive how age affects latencies and amplitudes. Older foetuses show, however, increased response rates and decreased latencies compared to younger foetuses, independent of modality. Key recommendations relate to improving data quality and comparability between studies. This will enable the development of clinical assessment tools in the future.