Neuropsychologia最新文献

Semantic memory, a repository for concepts and factual information, plays a vital role in acquiring and retrieving knowledge. This study explores the impact of age-related knowledge accumulation on semantic cognition, investigating whether a denser representational space affects retrieval processes. Using a semantic feature verification task, we employ both behavioral (reaction time; RT) and neurophysiological (event-related potential; ERP) measures to explore these dynamics across young and older adults. Findings revealed an age-related RT difference in retrieval of semantically incongruent features, indicative of increased semantic search demands with age. ERP results show attenuated N400 responses in older adults for congruent features, possibly reflecting increased semantic relatedness. The late frontal effect (LFE) shows sustained modulation in older adults, indicative of enhanced post-retrieval monitoring. We propose that this extended search through semantic memory reflects an increase in the number of features to evaluate. These results support the idea that aging leads to a more densely packed semantic space, impacting the speed and dynamics of semantic retrieval.

This study aimed to investigate prospective memory (PM) in patients with memory complaints but without dementia (PWD) and correlate findings with resting-state functional connectivity (rsFC) alterations. We hypothesized that PM impairment would be evident at a certain relatively early point in the continuum and specific rsFC patterns would be the neuroimaging signature of this impairment. Sixty PWD participated in the study. The Memory Screening Test for Intentions and the Virtual Week were used to assess PM. Using the participants' PM scores as a regressor, the rsFC for PM was analyzed by Network-Based Statistics (NBS). Participants were divided into high and low PM groups (HPMG, LPMG) according to their PM scores and then their neuropsychological scores, rsFC patterns, and CSF biomarker levels were compared. The effect of education on the relationship between connectivity and CSF Aβ₄₂ level was examined by moderation analysis. Compared with HPMG, LPMG was impaired in both event- and time-based PM tasks, but the difference was more distinct in the event-based ones. While HPMG was more successful in event-based tasks than time-based ones, LPMG was not. As a result of NBS analysis, the middle frontal gyrus (MFG), supramarginal gyrus (SMG), and anterior cingulate cortex (ACC) were determined as central seeds. The HPMG's performance and connectivity were higher for most comparisons but had lower CSF Aβ₄₂ than LPMG and therefore was closer to the positivity threshold. When the education level was at the mean and above, there was a negative correlation between CSF Aβ₄₂ level and overall connectivity. The connectivities of MFG, SMG, and ACC play an important role in PM performance in the PWD. In more advanced PM impairment, the impairment of spontaneous processes is more prominent. At the onset of amyloidosis, the cognitive reserve may compensate for cognitive impairment by increasing connectivity.

Although gesture observation tasks are believed to invariably activate the action-observation network (AON), we investigated whether the activation of different cognitive mechanisms when processing identical stimuli with different explicit instructions modulates AON activations. Accordingly, 24 healthy right-handed individuals observed gestures and they processed both the actor's moved hand (hand laterality judgment task, HT) and the meaning of the actor's gesture (meaning task, MT). The main brain-level result was that the HT (vs MT) differentially activated the left and right precuneus, the left inferior parietal lobe, the left and right superior parietal lobe, the middle frontal gyri bilaterally and the left precentral gyrus. MT (vs HT) differentially activated the left and right calcarine cortex, the fusiform gyrus bilaterally, the left inferior temporal gyrus, the left and right hippocampus and parahippocampal gyri, and the temporal pole bilaterally. Processing the actor's moving hand modulates the dorsal action observation network (while processing gesture meaning modulates the ventral object recognition stream). The present results suggest instruction-induced modulation on the visual stream during gesture observation.

Previous research has explored the brain correlates of perceptual grouping but, to our knowledge, no preceding study has investigated the neural dynamics of the competition between intrinsic and extrinsic grouping principles in vision. The present event-related potentials (ERPs) study aimed at characterizing the temporal neural dynamics of the direct competition between extrinsic (i.e., common region) and intrinsic (i.e., shape similarity) grouping cues. In separated blocks, participants selectively attended and responded to perceptual clusters based on one of the two grouping cues pitted against each other in a competing condition, which was compared to a uniform, non-grouped condition. Behavioural results indicated larger interference effect of common region over shape similarity cues when both grouping principles competed against each other, supporting a processing dominance of common region. Applying a temporo-spatial principal component analysis (PCA), our ERP data showed four main neural correlates related to perceptual grouping and competition between grouping cues: (1) an enhanced central-posterior N195 associated with perceptual dominance of common region cues during the visual analysis of perceptual grouping; (2) an enhanced posterior P245 presumably reflecting higher confidence in perceptual decisions linked to common region grouping; (3) a posterior P400 possibly indexing the differential allocation of attentional resources related to higher processing efficiency of common region cues; and (4) a P550 that seems to be related to top-down suppression activity for the termination of the current trial.

Background: Word production difficulty is one of the most common and persisting symptoms in people suffering from aphasia (i.e., anomia). However, there is a considerable variability in patients' responses to treatment, leading to the need of new effective approaches. Also, the mechanisms underlying word (re)learning is little known in production even in neurotypical adult native language and especially in relationship with the lexical-semantic integration of (re)learnt words. The lexical-semantic network being highly contextual and multimodal, new technologies such as immersive virtual reality may become pertinent approaches, but still need scientific proof, especially as past studies have found no advantage over a control method and have never used an immersive version of VR. Yet, the immersion has been identified as being a key factor of positive outcomes in learning. Therefore, the aim of the present study was to investigate whether immersive virtual reality provides a benefit in word learning in neurotypical adults (Study 1) and in the treatment for anomia in people suffering from aphasia following stroke (Study 2).

Method: In study 1, 32 neurotypical adults learned two matched lists of 30 rare words each in their native language (French) during a one-week protocol alternating test and learning sessions with immersive virtual reality (iVR) and with a digital static learning method. Study 2 followed the same design over a two week-period with 16 people with aphasia (re)learning two matched lists of 28 frequent words.

Results: Neurotypical adults demonstrated a higher accuracy rate in word production for words learned with iVR in comparison to those learned with the digital static learning method. For people suffering from anomia, the iVR did not differ from the control method on total accuracy but led to a greater reduction of lexical errors.

Conclusion: iVR has a potential of use for learning new words but also for the treatment of word production difficulties especially in people with aphasia that produce mainly lexical errors. These two main results lead to the hypothesis that iVR promotes lexical-semantic processes.

Neuroscience has examined the brain processes of recognizing and identifying a known person. But the process of integrating the representation of a temporarily unrecognised person with the representation of the familiar person is not yet known (e.g., as in Mandler's butcher on the bus). This process is one of identification; the stranger (man on the bus) has to be seen as identical to the old acquaintance (butcher from the supermarket). Our fMRI experiment contrasts this case of belated recognition with immediate recognition. The results show stronger activation of left inferior parietal lobe (IPL) and the left anterior temporal lobe (ATL) for identification over pure recognition. The data are discussed under the mental files framework providing an important extension to current person recognition paradigms.

Endogenous visuo-spatial attention is under the control of a fronto-parietal network of brain regions. One key node in this network, the intra-parietal sulcus (IPS), plays a crucial role in maintaining endogenous attention, but little is known about its ongoing physiology and network dynamics during different attentional states. Here, we investigated the reactivity of the left IPS in response to brain stimulation under different states of selective attention. We recorded electroencephalography (EEG) in response to single pulses of transcranial magnetic stimulation (TMS) of the IPS, while participants (N = 44) viewed bilateral random-dot motion displays. Individual MRI-guided TMS pulses targeted the left IPS, while the left primary somatosensory cortex (S1) served as an active control site. In separate blocks of trials, participants were cued to attend covertly to the motion display in one hemifield (left or right) and to report brief coherent motion targets. The perceptual load of the task was manipulated by varying the degree of motion coherence of the targets. Excitability, variability and information content of the neural responses to TMS were assessed by analysing TMS-evoked potential (TEP) amplitude and inter-trial phase clustering (ITPC), and by performing multivariate decoding of attentional state. Results revealed that a left posterior region displayed reduced variability in the phase of theta and gamma oscillations following TMS of the IPS, but not of S1, when attention was directed contralaterally, rather than ipsilaterally to the stimulation site. A right frontal cluster also displayed reduced theta variability and increased amplitude of TEPs when attention was directed contralaterally rather than ipsilaterally, after TMS of the IPS but not S1. Reliable decoding of attentional state was achieved after TMS pulses of both S1 and IPS. Taken together, our findings suggest that endogenous control of visuo-spatial attention leads to changes in the intrinsic oscillatory properties of the IPS and its associated fronto-parietal network.

While decreasing negative attitudes against outgroups are often reported by individuals themselves, biased behaviour prevails. This gap between words and actions may stem from unobtrusive mental processes that could be uncovered by using neuroimaging in addition to self-reports. In this study we investigated whether adding neuroimaging to a traditional intergroup bias measure could detect intersubject differences in intergroup bias processes in a societal context where opposing discrimination is normative. In a sample of 43 Finnish students, implicit behavioural measures failed to indicate intergroup bias against Middle Eastern and Muslim immigrants, and explicit measures reported rather positive attitudes and sentiments towards that targeted group. Yet, while implementing a repeatedly validated method for detecting intergroup bias, an implicit association paradigm presenting stereotypical ingroup and outgroup face stimuli while undergoing magnetoencephalography, we detected a clear neural difference between two experimental conditions. The neural effect is thought to reflect intergroup bias in the valence of the associations that faces evoke. The activity cluster of the neural bias peaked in BA37 and included significant activity in the fusiform gyrus, which has been repeatedly found to be active during face perception bias. Importantly, this neural pattern was driven by participants who were explicitly favourable of immigration - but to a lesser extent than others. These findings suggest that such variations in explicit support of immigration are associated with the differential neural sensitivity to the congruency of associations between intergroup faces and valence. This research showcases the potential of neuroimaging to unravel covert perceptual bias against outgroup members and its sensitivity to small variations in explicit attitudes.