Risky Choices After Frontal Brain Injury: Differential Effects in Self vs Other-Decision Contexts

Rostami, F.; Soltani, S.; Grafman, J.; Heyrani, R.; Yazdanpanah, A.; Jahanbakhshi, A.; Vahabie, A.-H.; Shariat, S. V.; Abdolalizadeh, A.; Mirfazeli, F. S.

doi:10.1101/2025.11.21.689684

bioRxiv · 10.1101/2025.11.21.689684

Risky Choices After Frontal Brain Injury: Differential Effects in Self vs Other-Decision Contexts

Rostami, F.·Soltani, S.·Grafman, J.·Heyrani, R.·Yazdanpanah, A.·Jahanbakhshi, A.·Vahabie, A.-H.·Shariat, S. V.·Abdolalizadeh, A.·Mirfazeli, F. S.

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Abstract

Frontal lobe integrity is crucial for assessing risk and making informed decisions. This study investigated how frontal lobe lesions affect the computational mechanisms underlying risky choice, particularly when decisions impact oneself versus another person. A Patient Group of 20 individuals with frontal cortex damage and a Control Group of 20 matched individuals performed a gambling task, making accept/reject decisions on mixed-outcome gambles for themselves ("Self") or an anonymous other ("Other"). We provide a mechanistic account of choice behavior using Prospect Theory, the leading behavioral model of decision-making under risk, to quantify parameters for utility curvature, loss aversion, and probability weighting. Behaviorally, the Patient Group accepted significantly more disadvantageous gambles for themselves than did the Control Group yet showed a trend toward greater caution when choosing for others. Prospect Theory modeling revealed a specific computational phenotype for this behavior. Compared to the Control Group, the Patient Group exhibited significantly more pronounced utility curvature (lower , {beta}) and more linear, less distorted probability weighting (higher {gamma}). While patients also showed a trend toward lower loss aversion ({lambda}), this difference was not statistically significant. This combination of altered utility and probability processing explains their paradoxical risk-seeking. These findings suggest that frontal cortex damage disrupts the computation of subjective value, leading to a distinctive decision-making profile marked by altered utility curvature and reduced sensitivity to outcome magnitudes. This computational characterization deepens our understanding of frontal lobe contributions to decision-making and can inform targeted rehabilitation strategies.

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Rostami, F., Soltani, S., Grafman, J., Heyrani, R., Yazdanpanah, A., Jahanbakhshi, A., Vahabie, A.-H., Shariat, S. V., Abdolalizadeh, A., Mirfazeli, F. S.. 2025-11-22. Risky Choices After Frontal Brain Injury: Differential Effects in Self vs Other-Decision Contexts. https://doi.org/10.1101/2025.11.21.689684

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