Language impairments and resting-state EEG in brain tumour patients:Revealing connections

Intact language functions are crucial for everyday communication. A brain tumour can impair these functions. We studied language abilities and their relation to resting-state brain activity in low-grade brain tumour patients, in search for predictors of language outcome after surgery. The brain tumours in this thesis include gliomas, which originate in the brain, and meningiomas, which arise from the meninges. Glioma and meningioma patients underwent thorough language assessments and brain activity registrations by electroencephalography (EEG). Two aspects of brain activity were evaluated: slow-wave activity, concerning activity with a low frequency, and functional connectivity brain networks, reflecting the extent to which brain areas interact.It is concluded that low-grade gliomas can cause impairments in a variety of language abilities. Furthermore, meningiomas can induce language impairments (primarily in speech production and writing), despite that these tumours do not infiltrate brain tissue. Many glioma and meningioma patients are presented with language impairments 1 year after surgery, but there is large interpatient variation. Our findings underline the importance of extensive language testing before and after brain tumour surgery. With regard to the EEG analyses, the outcomes indicate that increased slow-wave activity and particular characteristics of the functional connectivity networks are associated with poorer language functioning before surgery in glioma patients, unlike in meningioma patients. Moreover, two predictors of language outcome after glioma surgery are identified. This line of research requires further investigation because it has the potential to improve clinical procedures, such as treatment planning, patient counselling, and language rehabilitation

The role of frequency in the retrieval of nouns and verbs in aphasia

Background: Word retrieval in aphasia involves different levels of processing; lemma retrieval, grammatical encoding, lexeme retrieval and phonological encoding, before articulation can be programmed and executed. Several grammatical, semantic, lexical and phonological characteristics, such as word class, age of acquisition, imageability and word frequency influence the degree of success in word retrieval. It is, however, not yet clear how these factors interact. The current study focuses on retrieval of nouns and verbs in isolation and in sentence context and evaluates the impact of the mentioned factors on the performance of a group of 54 aphasic individuals. Aims: The main aim is to measure the effect of word frequency on the retrieval of nouns and verb by disentangling the influence of word class, age of acquisition, imageability and lemma and lexeme frequency on word retrieval in aphasia. Outcomes and Results: Word class, age of acquisition and imageability play a significant role in the retrieval of nouns and verbs: nouns are easier than verbs; the earlier a word has been learned and the more concrete it is, the easier it is to retrieve. When performance is controlled for these factors, lemma frequency turns out to play a minor role: only in object naming it affects word retrieval: the higher the lemma frequency of a noun, the easier it is to access. Such an effect does not exist for verbs, neither on an action-naming test, nor when verbs have to be retrieved in sentence context. Lexeme frequency was not found to be a better predictor than lemma frequency in predicting word retrieval in aphasia. Conclusions: Word retrieval in aphasia is influenced by grammatical, semantic and lexical factors. Word frequency only plays a minor role: it affects the retrieval of nouns, but not of verbs

Resting-State Electroencephalography Functional Connectivity Networks Relate to Pre- and Postoperative Language Functioning in Low-Grade Glioma and Meningioma Patients

Introduction: Preservation of language functioning in patients undergoing brain tumor surgery is essential because language impairments negatively impact the quality of life. Brain tumor patients have alterations in functional connectivity (FC), the extent to which brain areas functionally interact. We studied FC networks in relation to language functioning in glioma and meningioma patients. Method: Patients with a low-grade glioma (N = 15) or meningioma (N = 10) infiltrating into/pressing on the language-dominant hemisphere underwent extensive language testing before and 1 year after surgery. Resting-state EEG was registered preoperatively, postoperatively (glioma patients only), and once in healthy individuals. After analyzing FC in theta and alpha frequency bands, weighted networks and Minimum Spanning Trees were quantified by various network measures. Results: Pre-operative FC network characteristics did not differ between glioma patients and healthy individuals. However, hub presence and higher local and global FC are associated with poorer language functioning before surgery in glioma patients and predict worse language performance at 1 year after surgery. For meningioma patients, a greater small worldness was related to worse language performance and hub presence; better average clustering and global integration were predictive of worse outcome on language function 1 year after surgery. The average eccentricity, diameter and tree hierarchy seem to be the network metrics with the more pronounced relation to language performance. Discussion: In this exploratory study, we demonstrated that preoperative FC networks are informative for pre- and postoperative language functioning in glioma patients and to a lesser extent in meningioma patients

Distinct Slow-Wave Activity Patterns in Resting-State Electroencephalography and Their Relation to Language Functioning in Low-Grade Glioma and Meningioma Patients

INTRODUCTION: Brain tumours frequently cause language impairments and are also likely to co-occur with localised abnormal slow-wave brain activity. However, it is unclear whether this applies specifically to low-grade brain tumours. We investigate slow-wave activity in resting-state electroencephalography (EEG) in low-grade glioma and meningioma patients, and its relation to pre- and postoperative language functioning. METHOD: Patients with a glioma (N = 15) infiltrating the language-dominant hemisphere and patients with a meningioma (N = 10) with mass effect on this hemisphere underwent extensive language testing before and 1 year after surgery. EEG was registered preoperatively, postoperatively (glioma patients only), and once in healthy individuals. Slow-wave activity in delta- and theta- frequency bands was evaluated visually and quantitatively by spectral power at three levels over the scalp: the whole brain, the affected hemisphere, and the affected region. RESULTS: Glioma patients had increased delta activity (affected area) and increased theta activity (all levels) before and after surgery. In these patients, increased preoperative theta activity was related to the presence of language impairment, especially to poor word retrieval and grammatical performance. Preoperative slow-wave activity was also related to postoperative language outcomes. Meningioma patients showed no significant increase in EEG slow-wave activity compared to healthy individuals, but they presented with word retrieval, grammatical, and writing problems preoperatively, as well as with writing impairments postoperatively. DISCUSSION: Although the brain-tumour pathology in low-grade gliomas and meningiomas has a different effect on resting-state brain activity, patients with low-grade gliomas and meningiomas both suffer from language impairments. Increased theta activity in glioma patients can be considered as a language-impairment marker, with prognostic value for language outcome after surgery

Stability of spontaneous speech in chronic mild aphasia

Een spontane-taalanalyse bij afasie is een belangrijke toevoeging om de linguïstische en communicatieve mogelijkheden in kaart te brengen, een passend therapieplan op te stellen en de mate van vooruitgang te meten. In het onderhavige onderzoek wordt bij een groep van tien mensen met een milde afasie in de chronische fase onderzocht hoe stabiel de spontane taal is binnen een interview. Uit de spontane-taalinterviews zijn twee keer 300 woorden getranscribeerd en geanalyseerd volgens de Analyse voor Spontane Taal bij Afasie (ASTA; Boxum, Van der Scheer & Zwaga, 2010). Van veertien linguïstische variabelen is bekeken of er verschil is tussen de scores in de eerste en tweede 300 woorden. Ook is onderzocht of het gespreksonderwerp en de emotionele lading ervan invloed hebben op het taalgebruik. De scores op de linguïstische maten blijken stabiel te zijn gedurende een interview, met uitzondering van het aantal semantische parafasieën en het aantal seconden onverstaanbaar. Een verandering van het gespreksonderwerp blijkt geen significante invloed te hebben, maar de emotie die erbij beleefd wordt wel. Bij een negatieve emotie worden meer lexicale werkwoorden en minder zelfstandige naamwoorden gebruikt dan bij een positieve emotie. Toch lijkt een spontane-taalanalyse een stabiel en betrouwbaar beeld te geven van de taalproductie. Vervolgonderzoek kan uitwijzen of dit ook geldt voor andere fasen van afasie.In aphasia, an analysis of spontaneous speech provides opportunities to establish the linguistic and communicative abilities, to create suitable therapy plans and to measure language progress. The current study investigated the stability of spontaneous speech within an interview of ten mild aphasic participants in the chronic stage. Stability is important in order to enable making justified decisions about the underlying deficit(s). Two 300 words samples of spontaneous speech gathered during interviews were transcribed and analysed according to the ‘Analyse voor Spontane Taal bij Afasie’ (ASTA; Boxum, Van der Scheer & Zwaga, 2010). A comparison of the scores on fifteen linguistic variables between the first 300 words and the second 300 words was made. Also,it was investigated whether the conversation topic and its emotional charge influenced language usage. Results showed that the scores on the linguistic variables remained stable during an interview, except for the amount of semantic paraphasias and the number of seconds of incomprehensible speech. A change in the topic of conversation did not appear to have a significant influence; however, the emotion experienced with the topic did have an effect on language usage. More lexical verbs and fewer nouns were used when a negative emotion was experienced, compared to a positive emotion. An analysis of spontaneous speech seems to give a stable and reliable profile of language production in people with mild aphasia in the chronic stage, as long as the emotional charge of the topic remains stable. Further research could explore whether this also holds for other stages of aphasia