The Selective Hydraulic Vulnerability Principle: A Three-Tier Neuroangiogenic Framework for Brain Lateralization, Sexual Dimorphism, and Autism Spectrum Disorder

We propose a three-tier neuroangiogenic framework suggesting that selective vulnerability of the developing cerebral microvasculature may contribute to individual variation in brain lateralization and to a subset of Autism Spectrum Disorder (ASD) phenotypes. The framework is organized into three mechanistic tiers. Tier One introduces the core developmental principle: the fetal brain's vascular architecture is heterogeneous. High-order integration cortices, particularly perisylvian association regions, depend on densely arborized, high-resistance capillary networks that may be more vulnerable to reductions in perfusion than the relatively low-resistance vascular supply of primary sensorimotor cortices. This creates a developmental gradient of metabolic vulnerability. Tier Two proposes a sex-dependent biological modulation of this vulnerability. Estradiol may enhance angiogenesis, mitochondrial efficiency, and resistance to hypoxic stress during cortical development, potentially increasing vascular resilience in the female fetal brain. In contrast, the male fetal brain may develop with relatively lower vascular protection relative to its metabolic demand, thereby increasing susceptibility to adverse developmental conditions. Tier Three identifies maternal micronutrient depletion, chronic hypotension, placental insufficiency, and related forms of prenatal metabolic stress as candidate environmental contributors capable of amplifying this pre-existing vulnerability. We hypothesize that under sufficiently adverse developmental conditions, vulnerable perisylvian networks may experience relative metabolic growth impairment, potentially contributing to altered temporal coordination between higher-order integration regions and more preserved sensorimotor systems. Within this framework, ASD may represent one possible developmental outcome emerging from the interaction between selective vascular vulnerability, sex-dependent neuroangiogenic modulation, and environmental stress exposure. The model generates specific and falsifiable predictions involving cerebral perfusion, placental vascular biology, sex differences in neurodevelopment, and regional cortical growth trajectories. If this framework is correct, it suggests that the developing male brain may depend, far more than previously recognized, on the quality of maternal vascular and nutritional supply during critical prenatal windows — a dependency that may represent the developmental cost of lacking the female fetus's estrogenic angiogenic shield.