Parkinson's disease (PD) is a movement disorder caused by degeneration in dopaminergic neurons. During the disease course, most of PD patients develop mild cognitive impairment (PDMCI) and dementia, especially affecting frontal executive functions. In this study, we tested the hypothesis that PDMCI patients may be characterized by abnormal neurophysiological oscillatory mechanisms coupling frontal and posterior cortical areas during cognitive information processing. To test this hypothesis, event-related EEG oscillations (EROs) during counting visual target (rare) stimuli in an oddball task were recorded in healthy controls (HC; N = 51), cognitively unimpaired PD patients (N = 48), and PDMCI patients (N = 53). Hilbert transform served to estimate instantaneous phase and amplitude of EROs from delta to gamma frequency bands, while modulation index computed ERO phase-amplitude coupling (PAC) at electrode pairs. As compared to the HC and PD groups, the PDMCI group was characterized by (1) more posterior topography of the delta-theta PAC and (2) reversed delta-low frequency alpha PAC direction, ie, posterior-to-anterior rather than anterior-to-posterior. These results suggest that during cognitive demands, PDMCI patients are characterized by abnormal neurophysiological oscillatory mechanisms mainly led by delta frequencies underpinning functional connectivity from frontal to parietal cortical areas.
Background
Several researchers have reported the impairment of recognition of facial expressions in Alzheimer’s disease (AD) patients. AD had reduced theta and alpha responses compared to healthy controls during the recognition of facial expressions (Güntekin et al. 2019). Gamma responses also have a crucial role in the recognition of facial expression in healthy young adults (Güntekin and Başar 2014). AD had increased late gamma responses compared to healthy controls during working memory paradigms (Başar et al. 2017). The present study aims to analyze the gamma responses during the recognition of facial expressions in AD and healthy controls. We hypothesized that if the increase of late gamma responses is a general phenomenon in AD patients independent of the stimulation type, we expect to find increase gamma responses in AD patients in comparison to healthy controls.
Method
EEGs of 40 healthy controls (HCs) and 41 AD patients were recorded during their perception of three different facial expressions (angry, happy, neutral). Event‐related power spectrum and phase locking were analyzed for three different gamma bands (30‐35 Hz, 35‐ 40Hz, 40‐48 Hz) in two different time windows (0‐200 ms, 200‐400 ms).
Result
The group difference between AD patients and HCs was not significant for the phase‐locking values. AD patients had higher gamma power responses compared to healthy controls in 200‐400 ms time window for 30‐35 Hz(p=0.016), 35‐40 Hz(p=0.018) and 40‐48 Hz (p=0.039). The only significant group difference for the early time window (0‐200 ms) was found for 35‐40 Hz (p=0.046). The figure shows topographical plots of gamma (35‐40 Hz) power for 200‐400 ms time window in patients (upper part) and healthy controls (lower part) for angry, happy and neutral facial expressions.
Conclusion
The present study showed that the increase of late (200‐400 ms) gamma were independent of stimulus type in AD patients. The increase of gamma power in a 200‐400 ms time window was found in AD patients compared to healthy controls for all three facial expressions. The facial expression recognition in AD patients was differentiated from healthy controls by increased gamma power. Acknowledgments: This work (grant number 218S314) was supported by TUBITAK.
Demans tarama ve tanısı için klinik pratikte sıklıkla kısa tarama testleri kullanılmaktadır. Mini Mental Durum Testi (MMDT) en sık kullanılan testlerin başında gelmektedir. MMDT’nin demans için duyarlı olduğu bilinmektedir. Ancak, sağlıklı yaşlanma ile demans arasında bir geçiş evresi olarak kabul edilen Hafif Kognitif Bozukluk (HKB)’un ayırt edilmesinde ve Alzheimer Hastalığı tipi demans (AHD) ile HKB’nin ayırıcı tanısında MMDT çoğu zaman yeterli olmamaktadır. Kısa sürede uygulanabilen sözel akıcılık testleri (semantik ve fonemik) MMDT’ye alternatif ya da MMDT ile kullanıldığında HKB ve AH’nin erken evreleri için tanısal doğruluğu daha yüksek bir tarama testi elde edilebilir. Bu çalışmanın amacı MMDT, semantik ve fonemik akıcılık testlerinin ROC eğrisi analizleri ile belirlenen duyarlılık, özgüllük ve kesme puanı değerlerinin sunulmasıdır. Çalışmaya yaş-eğitim-cinsiyet açısından uyumlu 72 sağlıklı birey, 72 HKB ve 72 AHD’li birey dahil edilmiştir. Çalışmanın bulguları MMDT’nin sağlıklı bireyleri ayırt etmede semantik ve fonemik akıcılıktan daha güçlü olduğunu, ancak HKB ve AH ayrımında özgüllüğünün semantik akıcılıktan düşük olduğunu göstermektedir. Tanı doğruluğunun artırılması için kısa zamanda uygulanabilen sözel akıcılık testlerinin, özellikle semantik akıcılık testinin klinik pratiğe eklenmesi yararlı olabilir.
Dementia can be defined as deficits in more than one cognitive domain due to damage to the central nervous system, at a severity level that causes impairment in the activities of daily living. Although the word dementia is widely used in everyday life in western languages, its Turkish equivalent, "bunama" -originating from the root bun-or mun-, which means "disease, distress, stupidity" in old Turkish-is commonly known in society.The history of dementia actually goes back to antiquity. In ancient Greek and Greco-Roman texts, old age was inevitably associated with mental deterioration. The view was also put forward by Plato and Aristotle, the most important names of ancient philosophy. On the other hand, Cicero is one of the first names to say that aging does not always cause
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