Cortex最新文献

The human visual system is tuned to symmetry, and the neural response to visual symmetry has been well studied. One line of research measures an Event Related Potential (ERP) component called the Sustained Posterior Negativity (SPN). Amplitude is more negative at posterior electrodes when participants see symmetrical patterns compared to asymmetrical patterns. Source localization confirms that the SPN is generated by two dipoles in the left and right extrastriate cortex, in line with fMRI results. However, exploratory analysis by Tyson-Carr, Bertamini, Rampone, and Makin (2021) found a third symmetry response located approximately in the posterior cingulate peaking at around 600 msec. The third symmetry response was only generated in conditions where symmetry was 1) task relevant and 2) salient. We tested whether these findings are reliable by running source localization analysis on all suitable datasets from the complete Liverpool SPN catalogue (an online repository of all 40 SPN projects with 2215 participants https://osf.io/2sncj/). We predicted that less variance would be explained by a two-dipole model in experiments where participants classified regularity (hypothesis 1), and, when the third dipole is present, amplitude would correlate with that of the sensor-level SPN (hypothesis 2). Hypothesis 1 was not supported, while hypothesis 2 was. We conclude that the bilateral extrastriate symmetry response is sometimes followed by a third activation near the posterior cingulate. However, this third symmetry response is not as predictable as we had assumed. One possibility is that it may sometimes be hidden from average waveforms by temporal inconsistency between trials. This may happen more in experiments with longer presentation durations.

Neurologically intact individuals display a mild asymmetry in spatial attention that can be measured during experimental spatial tasks such as line bisection. Although this phenomenon, known as pseudoneglect, is traditionally explained as the consequence of right hemisphere dominance for visuospatial attention, surmounting evidence suggests this is not its sole or even its most important determinant. For instance, a recent fMRI study in left-handers revealed that rare individuals with a reversed, left hemispheric dominance (LHDS, N = 23) also demonstrated left-sided pseudoneglect, although their spatial bias was less marked compared to typically lateralized controls (N = 40). The current study sought to replicate and extend these findings in a broader cohort of right-handers (N = 75) and left-handers (N = 181), while addressing methodological limitations of the original study. Contrary to the predictions of the hemispheric specialization account, pseudoneglect was not reversed in LHDS participants (N = 49). However, the pseudoneglect effect was reduced compared to controls with typical cerebral laterality (N = 207) due to a population-level randomization of pseudoneglect in the LHDS group. These results align with those of the original study, supporting a multifactorial interpretation of pseudoneglect, with hemisphere specialization as one among many determinants rather than being the predominant cause.

Script training is a speech-language intervention designed to promote fluent connected speech via repeated rehearsal of functional content. This type of treatment has proven beneficial for individuals with aphasia and apraxia of speech caused by stroke and, more recently, for individuals with primary progressive aphasia (PPA). In the largest study to-date evaluating the efficacy of script training in individuals with nonfluent/agrammatic primary progressive aphasia (nfvPPA; Henry et al., 2018), robust treatment effects were observed, with maintenance of gains up to one year post-treatment. However, outcomes were constrained to measures of script accuracy, intelligibility, and grammaticality, providing a limited view of potential treatment benefit to connected speech. The current study evaluated the utility of a broader set of connected speech measures for characterizing script training outcomes in 20 individuals with nfvPPA who were administered Video-Implemented Script Training for Aphasia (VISTA). Probes of trained and untrained script topics from pre- and post-treatment were transcribed, coded, and analyzed using Computerized Language ANalysis (CLAN, MacWhinney, 2000) to extract measures of fluency, grammar, and informativeness. Speech timing measures (e.g., articulation rate, mean pause duration) were derived from audio files. Participants demonstrated significant changes for trained topics from pre-to post-treatment in words per minute, fluency disruptions per hundred words, mean length of utterance in morphemes, grammatical complexity, and proportion of open to closed class words. Reductions were observed in mean and variability of syllable duration and mean pause duration, and speech to pause ratio increased. These findings lend additional support for script training as a means to promote fluency of connected speech in individuals with nfvPPA and illustrate the utility of automated and semi-automated measures for characterizing treatment effects following intervention.

Formation of episodic memories is linked to cortico-hippocampal interactions during learning, practice, and post-learning rest, although the role of cortical activity itself in such processes remains elusive. Behaviorally, long-term retention of episodic memories has been shown to be aided by several different practice strategies involving memory reencounters, such as repeated retrieval and repeated study. In a two-session resting state electroencephalography (EEG) experiment, using data from 68 participants, we investigated the electrophysiological predictors of long-term memory success in situations where such reencounters occurred after learning. Participants learned word pairs which were subsequently practiced either by cued recall or repeated studying in a between-subjects design. Participants' cortical activity was recorded before learning (baseline) and after practice during 15-min resting periods. Long-term memory retention after a 7-day period was measured. To assess cortical activity, we analyzed the change in spectral power from the pre-learning baseline to the post-practice resting state recordings. From baseline to post-practice, changes in alpha and beta power were negatively, while slow frequency power change was positively associated with long-term memory performance, regardless of practice strategy. These results are in line with previous observations pointing to the role of specific frequency bands in memory formation and extend them to situations where memory reencounters occur after learning. Our results also highlight that the effectiveness of practice by repeated testing seems to be independent from the beneficial neural mechanisms mirrored by EEG frequency power changes.