Lecture: Professor Evan Balaban, Neuroimaging the dawn of integrative brain function
Neuroimaging the dawn of integrative brain function
Professor Evan Balaban
Behavioral Neurosciences Program
McGill University, Montreal, Canada
When in development do higher vertebrate embryo brains start functioning as integrative organs for the first time? To answer this question, chicken embryos were studied in the egg with a combination of sub-millimeter-resolution brain positron emission tomography (PET), structural x-ray computed tomography (CT) of the skeleton for fine-scale embryo aging, and non-invasive behavioral recording. PET imaging revealed unexpectedly wide variation in prenatal brain activity, inversely related to behavioral activity, which developed into different, sleep-like fetal brain states. Brief prenatal exposure to a salient chicken vocalization (eliciting strong postnatal behavioral responses) increased higher-brain activity significantly more than a spectrally-and-temporally-matching non-vocal noise analogue. Patterns of integrated activity between the brainstem and higher brain areas resembling awake, post-hatching animals were seen exclusively in chicken-stimulated embryos. This work suggests that integrative, waking-like brain function first becomes present in a latent but inducible state during the final 20% of embryonic life, and is selectively modulated by context-dependent monitoring circuitry. These data also revealed the developmental emergence of sleep-like behavior and its linkage to metabolic brain states, and highlighted problems with assigning embryo brain states based on behavioral observations.
