Mohamed Hesham Khalil
Adult hippocampal neurogenesis (AHN) is associated with cognitive reserve and mental health, and can be supported by environmental enrichment, such as spatial complexity, as a form of cognitive enrichment. Studies on human subjects show that navigating complex landscapes and higher geospatial complexity at a zipcode level are associated with greater hippocampal volume and lower risk of Alzheimer's disease, while laboratory studies show that spatial complexity can enhance AHN in mice and rats. However, the role of architectural spatial complexity remains unexplored, despite people spending ∼90% of their time indoors, which can pose a risk to AHN. To address this gap, first, this study developed a novel tool, the Architectural Spatial Complexity Index (A-SCI). The A-SCI was calculated based on seven layout variables and seven points of interest to maintain a balanced ratio, and the index scores were normalised to range from 0 to 1. Second, this study theoretically validated the A-SCI's ability to differentiate between enriched housing models that enhance AHN and non-enriched laboratory housing. It showed that enriched environments, using layout complexity, points of interest, or both, scored significantly higher than non-enriched animal housing models, with no difference between enrichment subtypes (layout complexity versus points of interest), demonstrating the theoretical validity of the A-SCI tool. Third, floor area did not independently predict the index scores after controlling for complexity. Fourth, exploratory assessments of human layouts demonstrate that multi-storey houses outscored single-storey apartments. Adding landscape and museum mazes yielded index scores comparable to those of multi-storey houses, both higher than those of apartments. Lastly, using an expanded dataset ( n = 63), historical palaces and contemporary shopping malls scored relatively higher, while hotel apartments and student accommodation scored similarly to apartments. Points of interest, which may provide cognitive enrichment independent of layout complexity, were not assessed in this study due to their dependence on social and economic factors that require separate investigation. The A-SCI tool offers a neuroscience-informed approach to architectural enrichment by design, which can support AHN in humans and help predict the risk of cognitive decline and mental health conditions such as depression. This paper encourages the use of the A-SCI tool for future research in architecture and neuroscience. Applications can span public health, space syntax, historical, and socioeconomic perspectives.