Metaphor Comprehension in Alzheimerʼs Disease and Behavioral-variant Frontotemporal Dementia:a Concurrent EEG-fNIRS study.


Erdoğan S. B.

FENS 2020, Edinburgh, İskoçya, 11 - 15 Temmuz 2020, ss.1-3

  • Basıldığı Şehir: Edinburgh
  • Basıldığı Ülke: İskoçya
  • Sayfa Sayıları: ss.1-3

Özet

Backround: One of the most important reasons of impairments in the social relations of dementia patients is the deficiency in abstract thinking and comprehension of abstract languages. Lakoff (year) argued that the metaphor language is a suitable basis for studying abstract thinking. Although some studies found that Alzheimer Disease (AD) patients have difficulty with mental processing of  metaphors, there are no electrophysiological and neuroimaging studies that have explored the neurophysiological correlates of this differential processing. The deteriorating effect of verbal language on social relations in the behavioral variant of the frontotemporal dementia (bvFTD) is also known. However; the neurophysiological basis of differences in the processing of metaphor language has not been studied in these patient groups either. The aim of this study was to investigate the neural correlates of differences in processing of metaphors in AD and bvFTD  patients as compared to healthy controls by multimodal recordings of the cerebral electrophysiology and hemodynamic activity. 

Methods: Participants: Twelve Turkish speaking patients with AD, twelve Turkish speaking patients with bvFTD and eleven Turkish speaking healthy control were enrolled in the study. Healthy controls were matched with patients on age and academic level. The stimulus consisted of 4 types (literal, conventional metaphor, novel metaphor, meaningless) of sentences. EEG and fNIRS recording and analysis: All EEG and NIRS signals were recorded simultaneously with a head probe that covered frontal, parietal, motor and temporal regions. For timing synchronization, triggers were sent to both EEG and NIRS equipment simultaneously via a parallel port using e-prime (E-Prime 2.0, Psychology Software Tools) EEG; 13 channels EEG active electrodes were placed on a cap (Acticap, Germany) according to the international 10-20 system (Fp1, Fp2, F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). We measured the amplitude of N400, late negative component (500-700 ms)and 700-900 ms time locked to the onset of critical word, which was also the sentence final-word. fNIRS; Measurements were conducted with fNIRS using 44 channel arrays of optodes (22 sources and 22 detectors). The Cohen’s d value of the oxyhemoglobine concentration (∆HbO2) for each block and for each channels was calculated using the MATLAB (The MathWorks Inc., Natick, USA) program.

Results: EEG results: N400: Repeated measure ANOVA with three repeated variables: 3(electrode site:frontal/central/parietal) 3(electrode laterality: left/middle/right) 4(condition: literal/ conventional/ novel/anormal) and one between variable (group: AD/bvFTD/control) revealed not significant main effect of group, F(2,32) = 1,1669 p > .05. The condition effect was significant F(2,71) = 5.594, p <. 05. Late Negative Components: Repeated measure ANOVA with three repeated variables: 3(electrode site:frontal/central/parietal) 3(electrode laterality: left/middle/right) 4(condition: literal/ conventional/ novel/anormal) and one between variable (group: AD/bvFTD/control) revealed significant main effect of group, F(2,32) = 3.922, p < .05.The condition effect was not significant F(1,57) = 2.723, p = .08.700-900 ms time window: Repeated measure ANOVA with three repeated variables: 3(electrode site:frontal/central/parietal) 3(electrode laterality: left/middle/right) 4 (condition: literal/ conventional/ novel/anormal) and one between variable (group: AD/bvFTD/control) revealed significant main effect of group, F(2,32) = 3.661, p < .05. The condition effect was not significant F(1,49) = 0.743, p > .05. fNIRS results: One-way repeated measure ANOVA revealed significant hemodynamic activity differences among 3 groups in Channel 9 and 10 for conventional metaphor stimuli and in Channel 4 and 42 for novel stimuli. These channels correspond to --- Post-hoc t-tests with Bonferroni correction showed that hemodynamic activity strength of Novel metaphor condition was stronger in AD when compared to FTD group (p=0.04), and stronger for FTD when compared to control group (p=0.016) in Channel 4. Hemodynamic activity of AD patients were found to be statistically significantly higher than control group during Novel metaphore condition in Channel 42 (p=0.008).

Discussion: Our results suggest that AD patients have sentence difficulty in late negative component than controls in three types of  sentences (literal, conventional metaphor, novel metaphor). However; bvFTD patients have differences in only conventional metaphors. These results point to the interest of late negative component (500-700 ms) to investigate sentence comprehension in AD and bvFTD. In 700-900 time window, AD patients have difference in only conventional metaphors than controls but bvFTD patients have no significant difference. Although N400 component is useful to understand the difference of conditions, late negative component and 700-900 time window is predictor for metaphor comprehension in AD and bv-FTD patients.