Effects of linguistic properties in preoperative language mapping: Insights from VLSM and navigated TMS

Tumors in the left hemisphere of the brain commonly cause language disturbances, prompting the recommendation of surgery for the removal of the tumor. Pre- and intraoperative language mapping methods are typically used to identify and preserve functional tissue. Previous work demonstrated that different semantic categories (e.g., actions vs objects) affect the outcomes of language mapping methods, yet it remains unclear whether words within the same semantic category but with different features also influence mapping outcomes. To this end, the present thesis explores the impact of words within the same semantic category but with different linguistic characteristics on the outcomes of language mapping. In Chapter 1, I reviewed studies that employed magnetic stimulation of the human cortex (Transcranial magnetic Stimulation) and verb or sentences, to highlight that the same brain regions are related to multiple linguistic processes without clear-cut differences between linguistic processing levels. In chapter 2, Lesion Symptom Mapping was used to demonstrate that words with various linguistic characteristics are differentially affected by gliomas in different regions. In chapters 3 and 4, navigated Transcranial Magnetic Stimulation was employed to investigate whether actions with varying numbers of arguments (eat vs hike) are differentially affected by the stimulation. Findings in neurotypical individuals and people with gliomas revealed that the production of transitive verbs (a verb that takes an object, e.g., eat) is more affected when posterior temporal regions of the left hemisphere are stimulated. The key point of this thesis is that items with small linguistic variations are differentially affected by tumor locations, and they can also influence the results of language mapping methods.