Abstract
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 covariate control, I argue that lesion size control is no valid
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 methodological and also 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.
Highlights
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Lesion size is a factor that is often considered or controlled
in neuropsychology
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No general causal relation between lesion size, lesion location
and deficit exists
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Lesion size in brain mapping, outcome prediction and behavioural
study is discussed
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Lesion size control is no valid covariate control
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Practical suggestions and guidelines how to consider lesion size
are provided