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How to find us prof. dr. R. (Roel) Jonkers

prof. dr. R. Jonkers

Vice dean, Faculty of Arts, professor in Neurolinguistics
prof. dr. R. Jonkers
Faculty Office Arts:

Apraxia of Speech; diagnosis and therapy

Start: september 2008 - ongoing

projectmembers: Judith Feiken, Joost Hurkmans, and Roel Jonkers

Sponsored by the Dutch Aphasia Foundation and the Foundation Beatrixoord Noord-Nederland

Within this project the diagnostic instrument for Apraxia of Speech (DIAS) was developed (Feiken and Jonkers, 2012). Afterwards , Judith Feiken has been  developing a therapy programme, the Therapeutic Instument for Apraxia of Speech, which was published as part of the Speech Therapy app (STAPP). Joost Hurkmans has evaluated the therapy programme SMTA on its effeciveness. In 2020, the Norwegean addaptation of the DIAS, Diagnostisk verktøy for taleapraksi, was published. 

Apraxia of Speech (AoS) is a speech motor disorder that in general results from vascular brain damage. An important aim in the diagnosis of AoS is the differential diagnosis between AoS and aphasia and dysarthria. In recent years, research has focused on the symptoms of AoS. Recently, a diagnostic test has been published, that can differentially diagnose AoS from other disorders (Feiken and Jonkers 2012). Diagnosis is based on determining the presence of 8 symptoms that relate to AoS (inconsistent distortion of sounds; more problems with consonants than with vowels; more problems with alternating syllables than with sequencing syllables; initiation problems; groping; cluster segmentation; syllable segmentation; effect of syllable complexity). Only 3 of these symptoms need to be present to make a valid diagnosis. This means that there is considerable variation in the characteristics of AoS within patients. This is partly due to the fact that some of the mentioned symptoms are seen as direct symptoms (such as initiation problems and inconsistent distortions), whereas others are seen as indirect symptoms. In these cases the system adapts to the foreseen problems in motor programming leading, for example, to schwa insertion or the segmentation of syllables.
A therapy programme that was recently developed in the Netherlands, and in which music plays an important role is Speech-Music Therapy for Aphasia (SMTA, De Bruijn,  Zielman & Hurkmans, 2005). SMTA is a combination of speech and music therapy used to remediate fluency problems associated with phonological deficits in aphasia. Next, SMTA is also used for subjects with dysarthria or apraxia of speech. It is administered at least twice a week in half-hour sessions. Therapy ends if target improvement is attained or if no more improvement is seen.  SMTA consist of two interwoven treatment approaches: a speech therapy approach focusing on sounds, words and sentences; and music therapy focusing on singing, emphasizing rhythmic speech and finally the intended normal speech. So far about 100 speakers have been treated using this programme. Practice based evidence is therefore sufficiently available. Joost Hurkmans recently finished a formal evaluation of the efficacy of the programme employing controlled scientific methods, showing that also in a multiple baseline accross behaviors study the effictivity of the programme can be proved.  


The effect of verb type on verb processing in dementia

Projectmembers: Jet Vonk (City Univesity of New York; supervisor: Dr. Loraine Obler) and Roel Jonkers

Period 2013 - 2017

Jet Vonk was sponsored by Prins Bernhard Cultuurfonds Grant (made possible by Banning-de Jong Fonds) (2013);  CUNY Graduate Center Fellowship (2013) and the Fulbright Graduate Scholarship Program (2013).

Verbs play an important role in language processing. In spite of a lot of studies on verb retrieval, both in non-language disturbed as well as in aphasic speakers, there is still no clear theory on the storage of verbs in the mental lexicon. Recent studies have shown that a reason for this is the fact that verbs should not be seen as one uniform category. In aphasia, effects of conceptual and grammatical aspects of verbs were shown to influence the performance of different types of aphasic subjects. The current study will explore a new fields in which the effect of verb type on verb processing was hardly ever considered, namely dementia. Outcomes from these studies will reveal more about how (types of) verbs are retrieved from the lexicon, how they are stored in the brain, and about the effect of a deficit on verb retrieval. The studies in dementia will be based on the expectations from the Embodied Cognition Framework. Within this framework it is assumed that semantic knowledge of verbs is not amodal, but should be incorporated in motor-sensory systems in the brain. The first project executed by Jet Vonk will focus on effects of verb type in verb processing in subjects suffering from different types of dementia. In the second study, executed by Roel Jonkers, a selection of these subjects will be followed in a longitudinal study that will last for at least three years, in order to be able to reveal more about the deterioration of verb retrieval.


Test for assessing Reference of Time

period: 2008 - ongoing 

Within this project the Test for assessing Reference of Time (Bastiaanse, Jonkers, and Thompson, 2008) was developed. This test has been translated into more than 40 languauges.   


Translation and adaptation into Frisian of Dutch diagnostic test batteries for aphasic subjects

period: 1 january 2004 – 1 january 2006

projectmembers: Nynke van den Bergh, Joost Hurkmans, Roelien Bastiaanse and Roel Jonkers

Sponsored by: Stichting Revalidatie Friesland ( , Provincie Friesland, Fonds de Gavere Innovatiefonds Zorgverzekeraar De Friesland (, Stichting Het Diaconessenhuis, University of Groningen


Description of the project

The Netherlands has two official languages, i.e. Dutch and Frisian. Frisian is spoken in Friesland , a province of the Netherlands . 45.000 people speak Frisian, on a total number of 60.000 who live in Friesland . For 350.000 people, Frisian is their mother language. Frisian is taught at primary and secondary schools and it is possible to study Frisian Language and Literature at the University of Groningen . Most Frisians who speak Frisian are bilinguals, as they also speak Dutch.

Although a lot of elderly people in Friesland speak Frisian, until now there was no diagnostic material to test the language abilities in Frisian for subjects who suffer from a language deficit like aphasia. Speech therapists in Friesland repeatedly reported this lack and therefore it was decided in a collaboration of the university of Groningen and Stichting Revalidatie Friesland to translate and adapt two Ducth test batteries for aphasic subjects into Frisian. The aim was not only to get tests in the Frisian language, providing the opportunity to diagnose the different language problems people suffer from, but also to find an answer to the question how to treat bilingual aphasic subjects, i.e. in Frisian or in Dutch.

The two aphasia tests that are used most frequently in Dutch, the Aachen Aphasia Test (Akense Afasie Test; Graetz, De Bleser, and Wilmes 1995) and the Amsterdam Nijmegen Everyday Language Test (Amsterdam-Nijmegen test voor alledaags taalgebruik; Blomert, Koster, and Kean 1995) were adapted into Frisian. The first test mainly focuses on the linguistic abilities of aphasic subjects, whereas the second tests mainly takes communicative capacities into account.


An important aspect of the development of the tests is validation. Although both Dutch tests are validated, this does not automatically mean that this also holds for the Frisian adaptation of these tests. Therefore a large group of non-language disturbed Frisian subjects is tested with versions of the Dutch tests and the Frisian adaptations.

In the first stage of the project, a Frisian translation has been made of both Dutch tests. This translation has been used in a small group of non-language disturbed subjects. From testing it was clear that it was not useful to adapt all subtests of the Aachen Aphasia Test. As Frisian has an oral tradition, the subtests that involve reading or writing were not used. In the pilot-phase it was concluded that a literal translations of the items in the tests could not always be used. In some cases there was no literal Frisian equivalent for a Dutch term, but also because now and then items did not fulfill the construction principle of the AAT, i.e. the items are of raising complexity. In repetition, for example, words get longer, and some Frisian translations are not of the same length (i.e. ontoerekeningsvatbaarheid - ûntarekkenberhied). Therefore, sometimes other words, with a comparable length to the Dutch word were chosen (i.e. the word lijnvliegtuigmodellenbedrijf, which is removed in the Frisian version by the word kleurpotleaddoazemakkerij),.

The project finished in May 2006. 120 non-aphasic subjects were tested with the Dutch and Frisian version of both tests. Variables like age, gender, education, region of birth and knowledge of Frisian were accounted for. Region of birth might be important as Frisian has some different dialects, which could influence the reactions. In general, the control subjects performed very well on the adapted tests. Furthermore, no differences were found between the Dutch and the Frisian version, which makes the Frisian version valid for administration with aphasic subjects. 

The tests have therefore also been administered with 30 aphasic subjects. THe aphasic subjects showed a better performance on the Frisian as compared to the Dutch version for the subparts Naming and Comprehension of the AAT, as well as for the measures Comprehensibility and Understadability of the ANELT.

Last modified:22 September 2020 12.03 p.m.

Contact information

Oude Kijk in 't Jatstraat 26
9712 EK Groningen
The Netherlands

Board of the Faculty; Linguistics

Job title:
vice dean, Faculty of Arts, full professor Neurolinguistics
Working hours:
monday - friday
Faculty Office Arts: