Differences in the oscillatory EEG dynamics of reading open class (OC) and closed class (CC) words have previously been found (Bastiaansen et al., 2005) and are thought to reflect differences in lexical-semantic content between these word classes. In particu-lar, the theta-band (4-7 Hz) seems to play a prominent role in lexical-semantic retrieval. We tested whether this theta effect is robust in an older population of subjects. Additionally, we examined how the context of a word can modulate the oscillatory dynamics underly-ing retrieval for the two different classes of words. Older participants (mean age 55) read words presented in either syntactically correct sentences or in a scrambled order ("scram-bled sentence") while their EEG was recorded. We performed time-frequency analysis to examine how power varied based on the context or class of the word. We observed larger power decreases in the alpha (8-12 Hz) band between 200-700 ms for the OC compared to CC words, but this was true only for the scrambled sentence context. We did not observe differences in theta power between these conditions. Context exerted an effect on the alpha and low beta (13-18 Hz) bands between 0 and 700 ms. These results suggest that the previously observed word class effects on theta power changes in a younger participant sample do not seem to be a robust effect in this older population. Though this is an indi-rect comparison between studies, it may suggest the existence of aging effects on word retrieval dynamics for different populations. Additionally, the interaction between word class and context suggests that word retrieval mechanisms interact with sentence-level comprehension mechanisms in the alpha-band.
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In the past decade, the fast and transient coupling and uncoupling of functionally related brain regions into networks has received much attention in cognitive neuroscience. Empirical tools to study network coupling include functional magnetic resonance imaging (fMRI)-based functional and/or effective connectivity, and electroencephalography (EEG)/magnetoencephalography-based measures of neuronal synchronization. Here we use simultaneously recorded EEG and fMRI to assess whether fMRI-based connectivity and frequency-specific EEG power are related. Using data collected during resting state, we studied whether posterior EEG alpha power fluctuations are correlated with connectivity within the visual network and between the visual cortex and the rest of the brain. The results show that when alpha power increases, BOLD connectivity between the primary visual cortex and occipital brain regions decreases and that the negative relation of the visual cortex with the anterior/medial thalamus decreases and the ventral–medial prefrontal cortex is reduced in strength. These effects were specific for the alpha band, and not observed in other frequency bands. The decreased connectivity within the visual system may indicate an enhanced functional inhibition during a higher alpha activity. This higher inhibition level also attenuates long-range intrinsic functional antagonism between the visual cortex and the other thalamic and cortical regions. Together, these results illustrate that power fluctuations in posterior alpha oscillations result in local and long-range neural connectivity changes.
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This study examines the automaticity of processing the emotional aspects of words, and characterizes the oscillatory brain dynamics that accompany this automatic processing. Participants read emotionally negative, neutral and positive nouns while performing a color detection task in which only perceptual-level analysis was required. Event-related potentials and time frequency representations were computed from the concurrently measured EEG. Negative words elicited a larger P2 and a larger late positivity than positive and neutral words, indicating deeper semantic/evaluative processing of negative words. In addition, sustained alpha power suppressions were found for the emotional compared to neutral words, in the time range from 500 to 1000. ms post-stimulus. These results suggest that sustained attention was allocated to the emotional words, whereas the attention allocated to the neutral words was released after an initial analysis. This seems to hold even when the emotional content of the words is task-irrelevant.
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Nederland is een belangrijke speler op de wereldwijde rozenmarkt. In 2023 exporteerde het land rozen ter waarde van 939 miljoen dollar, waarmee het de grootste exporteur ter wereld was ( (OECtoday, 2024). Rozenkwekers worden geconfronteerd met aanzienlijke uitdagingen, waaronder de verwoestende impact van ziekten zoals valse meeldauw, die zich onder gunstige omstandigheden snel kunnen verspreiden en ernstige oogstverliezen veroorzaken. Valse meeldauw vormt een ernstige bedreiging voor rozen, aangezien vooral buitenteelt onderhevig is aan weersinvloeden zoals hoge luchtvochtigheid, temperatuurschommelingen en regenval, die de verspreiding van de schimmel aanzienlijk bevorderen. De infectie leidt tot bladverlies, groeivertraging en een significante verslechtering van de bloemkwaliteit, wat resulteert in aanzienlijke economische schade voor telers. Dit project richt zich op de ontwikkeling van een geavanceerd AI-gebaseerd beeldherkenningssysteem dat specifiek is ontworpen voor het vroegtijdig detecteren van valse meeldauw (Peronospora sparsa) op rozen in de buitenteelt. Traditioneel worden chemische fungiciden ingezet, maar deze aanpak is zowel milieubelastend als inefficiënt op de lange termijn, mede door de ontwikkeling van resistentie bij de schimmel. Ons project beoogt daarom een duurzame, niet-chemische oplossing door middel van gerichte ultraviolet-bestraling (UV-C). De reeds ontwikkelde robot Alpha Ceres, die autonoom door rozenvelden navigeert met behulp van Real-Time-Kinematic (RTK) GPS, zal in de toekomst als draagplatform dienen voor deze technologie. In de eerste fase ligt de focus op de ontwikkeling van een robuust AI-algoritme voor herkenning van geïnfecteerde bladeren en het bepalen van hun positie. Daarnaar volgt het nauwkeurig bepalen van optimale UV-C-instellingen en laboratoriumtesten met geïnfecteerde planten. Er zal een proof-of-concept worden gerealiseerd met een opstelling bestaande uit een lopende band, camera’s en een actuator die de lamp naar de plant toe beweegt, welke beschikbaar is bij het GreenTechLab. Dit vormt de basis voor de overstap naar Alpha Ceres.
