The strange role of brain lesion size in cognitive neuropsychology

• Published in: Cortex 2022-01, Vol.146, p.216-226
• Main Author: Sperber, Christoph
• Format: Article
• Language: English
• Subjects: Brain - diagnostic imaging; Brain Mapping; Cognition; Covariate control; Humans; Lesion volume; Lesion–deficit prediction; Magnetic Resonance Imaging; Neuropsychology; Stroke; Stroke - complications; Stroke - diagnostic imaging; Voxel-based lesion symptom mapping
• ISSN: 0010-9452; 1973-8102
• DOI: 10.1016/j.cortex.2021.11.005

The size of brain lesions is a variable that is frequently considered in cognitive neuropsychology. In particular, lesion-deficit inference studies often control for lesion size, and the association of lesion size with post-stroke cognitive deficits and its predictive value are studied. In the present article, the role of lesion size in cognitive deficits and its computational or design-wise consideration is discussed and questioned. First, I argue that the commonly discussed role or effect of lesion size in cognitive deficits eludes us. A generally valid understanding of the causal relation of lesion size, lesion location, and cognitive deficits is unachievable. Second, founded on the theory of causal inference, I argue that lesion size control is no generally appropriate covariate control. Instead, it is identified as a procedure with only situational benefits, which is supported by empirical data. This theoretical background is used to suggest possible research practices in lesion-deficit inference, post-stroke outcome prediction, and behavioural studies. Last, control for lesion size is put into a bigger historical context – it is identified to relate to a long-known association problem in neuropsychology, which was previously discussed from the perspectives of a mislocalisation in lesion-deficit mapping and the symptom complex approach.