Cortex最新文献

The processing of stationary sounds relies on both local features and compact representations. As local information is compressed into summary statistics, abstract representations emerge. Whether the brain is endowed with distinct neural architectures predisposed to such computations is unknown. In this magnetoencephalography (MEG) study, we employed a validated protocol to localize cortical correlates of local and summary auditory representations, exposing participants to sequences embedding triplets of synthetic sound textures systematically varying for either local details or summary statistics. Sounds varied for their duration and could be short (40 ms) or long (478 ms) to favor change detections based on local or summary statistics, respectively. Results clearly revealed distinct activation patterns for local features and summary auditory statistics. Neural activations diverged in magnitude, spatiotemporal distribution, and hemispheric lateralization. The right auditory cortex, comprising both primary and neighboring temporal and frontal regions were engaged to detect sound changes in both local features (for short sounds) and summary statistics (for long sounds). Conversely, the left auditory cortex was not selective to these auditory changes. However, the ventro-lateral portion of left frontal lobe, a region associated with sound recognition, was engaged in processing changes in summary statistics at a long sound duration. These findings highlight the involvement of distinct cortical pathways and hemispheric lateralization for the computation of local and summary acoustic information occurring at different temporal resolutions. SIGNIFICANT STATEMENT: We revealed hemispheric specializations for auditory computations at high (local) and low (summary statistics) temporal resolutions. The right hemisphere was engaged for both computations, while the left hemisphere responded more to summary statistics changes. These findings highlight the multifaceted functions of the right hemisphere in capturing acoustic properties of stationary sounds and the left hemisphere's involvement in processing abstract representations.

While pre-verbal infants may be sensitive to others' mental states, they are not able to accurately answer questions about them until several years later, an ability referred to as having a theory of mind. Here we ask whether infant social-cognitive sensitivity is subserved by the same brain mechanisms as those that support theory of mind in childhood. To do so, we explored the relationship between functional sensitivity of the right temporal-parietal junction to mental state processing in infancy, a region known to underlie theory of mind in older children, and explicit theory of mind reasoning in the same group several years later. In a small initial sample (N = 33), we find evidence of a longitudinal brain-behavioral link from infancy to childhood, providing preliminary support for a common mechanism for theory of mind across development. However, the brain metric that was predictive of individual differences was not the response to conditions that required tracking the beliefs, but instead, the response to a control condition where belief tracking was not obligatory to predict others' behavior. In hindsight, the ambiguity of this control condition may have best distinguished between infants who had different propensities to engage in belief tracking, suggesting a potential role for active experience in infancy contributing to individual differences in later theory of mind development in childhood. Given the exploratory nature of the study, other alternative explanations for these results must also be considered.

To access its online representations, visual working memory (VWM) relies on a pointer-system that creates correspondence between objects in the environment with their memory representations. This pointer-system allows VWM to modify its representations using a process called updating. When the pointer is invalidated, however, VWM triggers a process called resetting in which the no longer relevant representation and pointer are replaced. Past studies used the contralateral delay activity (CDA) to differentiate between updating and resetting and found that resetting is followed by a drop in the CDA amplitude. The current study aimed to investigate the effects of occlusion on VWM representations and the resetting process across four experiments. Experiment 1 examined whether resetting occurs with occluded changes and compared the CDA of occluded versus visible objects. The results indicated a decline in CDA amplitude during occlusion, but it was unclear if resetting occurred when the change was occluded due to the lack of time-locked changes. To better isolate the resetting process, Experiment 2 used a brief occluder appearances (100 ms) and observed a CDA drop likely due to an ERP response to the sudden stimulus appearance. This drop occurred earlier than the resetting CDA drop and appeared even in conditions that did not trigger resetting, which indicates that it might be an ERP response to the short and sudden appearance of a stimulus. Experiment 3 further isolated this ERP response, confirming the early CDA drop as a reaction to the occluder's onset and offset. Experiment 4, which included occluders that did not flash to avoid ERP responses, found a CDA drop indicating that resetting can occur with inferred changes. These findings suggest that VWM maintains representations of occluded objects, and can update or reset these representations based on inferred changes, with brief stimuli eliciting ERP responses that affect CDA amplitude.

Background: Alzheimer's disease (AD) can be diagnosed by in vivo abnormalities of amyloid-β plaques (A) and tau accumulation (T) biomarkers. Previous studies have shown that analyses of serial position performance in episodic memory tests, and especially, delayed primacy, are associated with AD pathology even in individuals who are cognitively unimpaired. The earliest signs of cortical tau pathology are observed in medial temporal lobe (MTL) regions, yet it is unknown if serial position markers are also associated with early tau load in these regions. This study of cognitively unimpaired older individuals examined whether serial position scores in word-list recall cross-sectionally predicted tau PET load in the MTL, and were able to discriminate between biomarker profiles, based on AT classification.

Methods: Data from 490 participants (mean age = 68.8 ± 7.2) were extracted from two cohorts, which were merged into one sample. Linear regression analyses were carried out with regional volume-controlled tau (18F-MK-6240) PET SUVR of the entorhinal cortex (EC), parahippocampal cortex (PHC) and hippocampus (H) as outcomes, cross-sectional memory scores from the Rey Auditory Verbal Learning Test as predictors (total and delayed recall, along with serial position scores) and control variables, in separate analyses for each outcome and predictor. The sample was then stratified by biomarker profile and ANCOVAs were conducted with the strongest scores from the regression analyses, AT groups as fixed factor and the covariates.

Results: Higher delayed primacy significantly predicted lower tau PET in EC, PHC, and H, cross-sectionally. Higher total recall scores predicted lower EC tau, but delayed primacy showed the best model fit, as indicated by AICs. ANCOVAs showed that AVLT metrics did not significantly discriminate between A-T- and A+T+, after correcting for multiple comparisons.

Conclusions: Serial position analysis of word-list recall, particularly delayed primacy, may be a valuable tool for identifying in vivo tau pathology in cognitively unimpaired individuals.

The synergy between cognitive theory and neuropsychology is a hallmark of Sergio Della Sala's research, of his 25 years as editor of Cortex, and of over 40 years of a Della Sala-Logie research collaboration. This short article highlights some of that completed and ongoing collaborative research focused on the cognition of memory in the healthy, ageing, and impaired brain.

Pupil size is modulated by various cognitive factors such as attention, working memory, mental imagery, and subjective perception. Previous studies examining cognitive effects on pupil size mainly focused on inducing or enhancing a subjective experience of brightness or darkness (for example by asking participants to attend to/memorize a bright or dark stimulus), and then showing that this affects pupil size. Surprisingly, the inverse has never been done; that is, it is still unknown what happens when a subjective experience of brightness or darkness is eliminated or strongly reduced even though bright or dark stimuli are physically present. Here, we aim to answer this question by using perceptual fading, a phenomenon where a visual stimulus gradually fades from visual awareness despite its continuous presentation. The study contains two blocks: Fading and Non-Fading. In the Fading block, participants were presented with black and white patches with a fuzzy outline that were presented at the same location throughout the block, thus inducing strong perceptual fading. In contrast, in the Non-Fading block, the patches switched sides on each trial, thus preventing perceptual fading. Participants covertly attended to one of the two patches, indicated by a cue, and reported the offset of one of a set of circles that are displayed on top. We hypothesized that pupil size will be modulated by covert visual attention in the Non-Fading block, but that this effect will not (or to a lesser extent) arise in the Fading block. We found that covert visual attention to bright/dark does modulate pupil size even during perceptual fading (Fading block), but to a lesser extent than when the perceptual experience of brightness/darkness is preserved (Non-Fading block). This implies that pupil size is always modulated by covert attention, but that the effect decreases as subjective experience of brightness or darkness decreases. In broader terms, this suggests that cognitive modulations of pupil size reflect a mixture of high-level and lower-level visual processing.

The lateralised bias of spatial neglect can be modulated by concurrent non-lateralised impairments. For instance, people with left neglect may have spatial working memory deficits that prevent them from keeping track of locations visited in visual search tasks such as target cancellation. Not only do they omit targets in some parts of the array but they may revisit and re-cancel targets in other parts, and this re-cancellation behaviour increases dramatically in 'invisible' conditions, in which touching a target leaves no visible trace. It has been proposed that spatial memory deficits are the main reason for the rise of re-cancellation errors in invisible cancellation conditions. This idea predicts that spatial memory abilities should correlate with re-cancellation behaviour; but this expected relationship has never been demonstrated. The present study takes an exploratory approach to describing the behaviour of 18 people with left visual neglect, following right hemisphere stroke, on touchscreen tests of spatial working memory and target cancellation. We show that people with neglect who are less able to remember locations in a spatial memory task tend to make more re-cancellation errors in invisible cancellation conditions. We also describe an apparent trade-off, in which some people with neglect make many more re-cancellation errors, whilst others make many more target omissions. We suggest that the influence of spatial memory deficits on invisible cancellation tasks can be more fully captured by considering both types of errors, rather than re-cancellations only.