The brain begins organising itself long before birth, and a study led by Tomáš Paus, professor of psychiatry and neuroscience at Université de Montréal and researcher at CHU Sainte-Justine, shows how maternal smoking can interfere with that hidden process. Published in Cerebral Cortex, the work drew on a cohort launched more than two decades ago in Quebec's Saguenay-Lac-Saint-Jean region, in which over 1,000 adolescents aged 12 to 18 were assessed, with some followed into adulthood.
Examining 11 brain regions, the team found that the primary visual cortex, area V1, showed the largest difference between people exposed to tobacco smoke in utero and those who were not: its surface area was smaller in the exposed group. The pattern replicated in roughly 20,000 adults from a British biobank, an entirely different population, and analyses using causal genetic variants supported nicotine exposure as the driver rather than a mere correlate.
The proposed mechanism is elegant and sobering. Before birth, the retina generates spontaneous waves of activity that depend on the neurotransmitter acetylcholine, and nicotine disrupts precisely this signalling, potentially altering how V1 is built. In the biobank data, a larger V1 was associated with better shape perception, though a direct link between cortical surface and visual acuity has been shown in animals rather than humans. The study reinforces the view that fetal experience, not genes alone, sculpts the developing brain.