Tenure Track 3
(last update 2020-05-12)
Neuropsychology of Language and Language Disorders
The study of brain-language relationships dates back to the 19th century, from observing the behaviour of patients with brain damage. In more recent decades, much progress has been booked, but basic and clinically applied research on brain and language are often being conducted in isolation. This divide is unfortunate since clinical observations are powerful in informing theories on brain and language. Conversely, these theories can help better understand deficits in clinical populations and inspire new tools for diagnosis and treatment.
This tenure track focuses on performing pre-clinically and clinically oriented research on language. This position bridges the gap between clinical and non-clinical research on language in Nijmegen, nationally and internationally, and promotes interactions between RU and RUMC. It aims at establishing a research programme on language function and dysfunction. This approach takes the strength of both basic and applied fields to widen the theoretical understanding of brain and language relationships and to improve the care for clinical populations that suffer from speech, language, and communication deficits.
Highlight 1: White-matter connectivity in the left posterior middle temporal gyrus – Differentiation from chimpanzees to humans
Team members: Sierpowska, Bryant, Janssen, Mangnus, Römkens, Roelofs, Kessels, Freches, Mars, and Piai
We compared white matter connectivity of the left posterior middle temporal gyrus (L_pMTG) structural bottleneck and left anterior temporal lobe (L_ATL) bottleneck between humans and chimpanzees.
We revealed an extensive ventral system of white matter pathways (including IFOF) originating from the L_ATL seed in both humans and chimpanzees. Importantly, the maps did not substantially differ between the two species. In humans, the probabilistic tracking from L_pMTG showed that the ventral white-matter system extends to both the right hemisphere via the tapetum and to the dorsal pathways for language via the connection between the posterior superior temporal sulcus and the inferior parietal lobe. In chimpanzees, this circuitry was similar with regard to the interhemispheric connections, but connectivity to the dorsal stream was less robust than in humans. Quantification of these (dis)similarities indicated that the L_pMTG difference in connectivity may be mainly explained by how this circuitry connects towards the canonical, dorsal pathways for language, whereas this pattern is explained by the connectivity towards the ventral pathways for language for the L_ATL.
Figure 1. Upper panel: Overlap of individual pMTG white matter connectivity maps for human (left) and chimpanzee (right). Lower panel: Overlap of individual ATL white matter connectivity maps for human (left) and chimpanzee (right). Hotter colours indicate more individuals showing overlapping white matter connectivity.
In this project we addressed one the core questions of the BQ2: what characteristics of human brains may support our unique abilities to acquire/use language. The previous experience of the team, indicating a particular sensitivity to language impairments when any of the white matter hub is damaged in clinical populations, inspired a question of their possible role in human language evolution.
Thanks to this project, various members of two LiI-associated groups a new and dynamic working team. Conjoined expertise in neuroimaging and white matter neuroanatomy brought together clinical and comparative perspectives in order to explore temporal lobe white matter bottlenecks in language.
Highlight 2: The effect of Deep Brain Simulation on the Subthalamic Nucleus on language function in Parkinson’s Disease: A review
Team members: Sandra H. Vos, Roy Kessels, and Vitória Piai
We conducted a systematic review of the effects of deep brain stimulation (DBS) on the subthalamic nucleus on language in patients with Parkinson’s disease (PD). Verbal fluency tasks are the most frequently used and investigated. Overall, verbal fluency was negatively affected by DBS. Importantly, this could not be ascribed to general disease progression as the studies were critically selected on having a matched PD control group without surgery but on best medical treatment, and this control group did not show the same amount of decline over time. Third, picture naming is frequently used as an additional measure of language function.
The present review shows that it is not affected after DBS surgery in PD on a group level, in contrast to verbal fluency. However, studies investigating individual change patterns showed more variability for picture naming performance than for verbal fluency after DBS. Fourth, the present review shows that there is a lack of studies using other language tasks than verbal fluency and/or picture naming. The results of the present review add to current recommendations that the investigation of language function in PD requires sensitive language tests with and without time pressure.
We brought knowledge on psycholinguistics to the field of neuropsychology. It contributes to LiI by showing how surgery and stimulation of the subthalamic nucleus relates to language and to societal relevance by highlighting the gaps in our knowledge that are important for improving health care. The questions asked and answered by this review were only made possible by the collaboration between the fields of psycholinguistics, neuropsychology, and neurology.
Progress Update 2019
Several new collaborations were established in 2019. Multiple manuscripts have been submitted to top journals, others are under review, and several have been published.
Furthermore, a Dutch translation of TeleLanguage was developed as TeleLanguage-NL. This tool provides the opportunity for clinicians to call patients and assess their language abilities via telephone. It is currently already in use at the Radboud University Medical Centre to monitor patients in the weeks and months after brain surgery.
Synergy with Big Questions
This tenure track focuses for a large part on the neurobiology of language and, as such, fits very well with BQ2. Interactions with BQ4 have also increased due to the adoption of Syntest in their battery. All projects described above are to a greater or lesser extent interdisciplinary, as they combine knowledge from different fields, e.g., theoretical linguistics, neurolinguistics, speech therapy, neuroscience, neuropsychology, audiology, speech- and language-pathology, neurology, using a diverse range of techniques (behavioural, haemodynamics, electrophysiology, non-invasive brain stimulation). There have also been great interactions with some other projects previously initiated within LiI, for example, PhD project from Janssen and one of the projects from Utilisation Call II: SimpTell.
1) Collaboration with BQ4 through their adoption of the SynTest, developed within this tenure-track, into their test battery. The benefit for BQ4 is straightforward, since their test-battery was increased in scope thanks to this development. For the tenure-track, the benefit is also substantial since the data collected by BQ4 will enable providing norms not only for adults, but for the whole range of populations examined in BQ4.
2) Internal within DI - “A comparative approach to the white matter anatomy of the left temporal lobe semantic processing hubs”, a collaboration with Bryant (DCC) and Mars. Investigating the patterns of white matter connectivity of two specific areas (posterior middle temporal gyrus and anterior temporal lobe) within the left temporal lobe. Both of these brain portions are claimed to be involved in semantic processing and/or semantic learning. Using a probabilistic single region of interest tractography approach in human and chimpanzees. Results will be further compared between the species.
Innovativeness and Interdisciplinarity
This tenure track focuses on performing pre-clinically and clinically oriented research on language. This position bridges the gap between clinical and non-clinical research on language in Nijmegen, nationally and internationally, and promotes interactions between RU and RUMC. It aims at building collaborations with research groups from RUMC, establishing a research programme on language function and dysfunction.