Association of abnormal semantic processing with delusion-like ideation in frequent cannabis users: an electrophysiological study

Patients suffering from Alzheimer's disease (AD) have severe difficulties in tasks requiring the use of semantic knowledge. The semantic deficits associated with AD have been extensively studied by using behavioral methods. Many of these studies indicate that AD patients have a general deficit in voluntary access to semantic representations but that the structure of the representations themselves might be preserved. However, several studies also provide evidence that to some extent semantic representations in AD may in fact be degraded. Recently, a few studies have utilized event-related brain potentials (ERPs) that are sensitive to semantic factors in order to investigate the electrophysiological correlates of the semantic impairment in AD. Interest has focused on the N400 component, which is known to reºect the on-line semantic processing of linguistic and pictorial stimuli. The results from studies of N400 changes in AD remain somewhat controversial: Some studies report normal or enlarged N400 components in AD, whereas others report diminished ones. One issue not reported in previous studies is whether word-elicited ERPs other than N400 remain normal in AD. In the present study our aim was to find out whether the ERP waveforms N1, P2, N400, and Late Positive Component (LPC) to semantically congruous and incongruous spoken words are abnormal in AD and whether such abnormalities specifically reºect deficiencies in semantic activation in AD. Auditory ERPs from 20 scalp sites to semantically congruous and incongruous final words in spoken sentences were recorded from 17 healthy elderly adults and 9 AD patients. The early ERP waveforms N1 and P2 were relatively normal for the AD patients, but the N400 and LPC effects (amplitude difference between congruous and incongruous conditions) were significantly reduced. We interpret the present results as showing that semantic-conceptual activation and other high-level integration processes are defective in AD. However, a word congruity effect earlier than N400 (phonological mismatch negativity), reflecting lexical selection processes, is at least to some extent preserved in AD.

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When dogs meow: an electrophysiological study of lexical-semantic processing in toddlers

10.31234/osf.io/wc24h ◽

2021 ◽

Author(s):

Mirella Manfredi ◽

Moritz M. Daum

Keyword(s):

Semantic Processing ◽

Electrophysiological Study ◽

Age Groups ◽

Control Group ◽

Older Children ◽

N400 Effect ◽

Brain Potentials ◽

Lexical Information ◽

Lexical Semantic ◽

Two Age Groups

The goal of this study was to investigate lexical–semantic processing at an early phase of language development. Adults often communicate with children using infant-directed speech that typically involves lexical and syntactic modifications such as onomatopoeias (Soderstrom, 2007).Here we asked how and when children start to show an advantage for processing conventional linguistic forms, such as common nouns, and consequently decreasing sensitivity to onomatopoeias. We recorded event-related brain potentials in children of two age groups (16 to 20 months and 24 to 30 months) and in an adult control group during the presentation of the four conditions in which either common nouns or onomatopoeias were presented auditorily followed by either a congruent or incongruent image. The younger children showed a N400 effect only for onomatopoeic words, while the older children showed a N400 effect only for common nouns. The adults show N400 for onomatopoeia and nouns. These different N400 effects suggest that these categories are differently organized in children’s semantic memory and that the acquisition of linguistic abilities affects and modifies semantic processing of different lexical information.

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