Defining the Lesion for Lesion-Symptom Mapping

Brain lesions can have many causes including injury, disease, and infections. Lesion-symptom mapping is a tool used by investigators to understand the relationship between brain structure and function. There are many different types of brain lesions with varying characteristics that researchers must consider when deciding which participants to include to best answer their specific research questions of interest. In this chapter, we discuss the different types of lesions that may be used in brain mapping research, the characteristics of those lesions including the stability of lesions over time, and appropriateness and challenges specific to each lesion type for behavior mapping at various time points. Different types of lesions discussed include lesions resulting from ischemic or hemorrhagic stroke, traumatic brain injury, neurodegenerative disease, brain tumors, surgical resection of lesions, brain abscesses, and transient lesions from transcranial magnetic stimulation (TMS). As the brain will reorganize during spontaneous recovery processes and rehabilitation following an insult, the importance of considering not only which types of lesions to study, but also the time point at which they are studied, is also discussed.