Ann-Katrin Ohlerth

I am a (clinical) neurolinguist, interested in the individual localisation of language production sites both on the cortex and in subcortical white matter networks, particularly in the non-healthy brain, e.g. when a lesion (such as a brain tumor) causes function to relocate to mostly unpredictable areas. But even in the healthy brain, large individual differences in both structure and function have surfaced in recent years and have motivated my research. 

Through my master’s thesis and later PhD project at the universities of Groningen, Potsdam, Trento and Macquarie, Sydney, in collaboration with the Technical University in Munich, I have employed non-invasive stimulation mapping with navigated Transcranial Magnetic Stimulation (nTMS) in order to localise crucial language production hubs, that are recruited in naming pictures, in the individual brain. In particular, we challenged the existing approach in nTMS by introducing sentence-building skills as needed in the verb-targetting action naming task, next to the commonly used noun-targetting task object naming. This led to a higher sensitivity of delineating cortical areas and subcortical tracts that need preserving during surgical intervention, in order not to risk postoperative loss of language function. (For more info, check out my thesis on action naming in language mapping).

While this work took an important step in improving the method of nTMS and in deepening our understanding of segregated networks for nouns and verbs in the brain, it left us with many open questions that I am now planning to address in my postdoctoral position here at the Max Planck Institute: 

• Can the intersubject-variability in function and susceptibility to nTMS be accounted for by the widely understudied variability in anatomical structure, more particularly in the white matter networks?
• What role do specific items and their properties across tasks play in the localization of action/verb and object/noun production?
• How can we disrupt and thereby localise grammatical encoding under stimulation mapping, a process most often impaired in lesioned brains, yet hard to mimic in virtual lesion models such as nTMS?
• Is the right hemisphere solely involved in prelinguistic conceptual retrieval as often revealed by nTMS mapping or do we need to rephrase our understanding of its contribution by using finer grained language tasks?
• How can we best capture language through stimulation mapping in the left temporal lobe, as this patient group is mostly at risk of experiencing long lasting effects of surgical intervention?