The ERP correlates of self-knowledge in ageing.

Self-knowledge is a type of personal semantic knowledge that concerns one's self-image and personal identity. It has most often been operationalized as the summary of one's personality traits ("I am a stubborn person"). Interestingly, recent studies have revealed that the neural correlates of self-knowledge can be dissociated from those of general semantic and episodic memory in young adults. However, studies of "dedifferentiation" or loss of distinctiveness of neural representations in ageing suggest that the neural correlates of self-knowledge might be less distinct from those of semantic and episodic memory in older adults. We investigated this question in an event-related potential (ERP) study with 28 young and 26 older adults while they categorised personality traits for their self-relevance (self-knowledge conditions), and their relevance to certain groups of people (general semantic condition). Participants then performed a recognition test for previously seen traits (episodic condition). The amplitude of the late positive component (LPC), associated with episodic recollection processes, differentiated the self-knowledge, general semantic, and episodic conditions in young adults, but not in older adults. However, in older adults, participants with higher composite episodic memory scores had more differentiated LPC amplitudes across experimental conditions. Moreover, consistent with the fact that age-related neural dedifferentiation may be material and region specific, in both age groups some differences between memory types were observed for the N400 component, associated with semantic processing. Taken together, these findings suggest that declarative memory subtypes are less distinct in ageing, but that the amount of differentiation varies with episodic memory function.

Cognitive and neuroimaging markers for preclinical vascular cognitive impairment.

Detection of incipient cognitive impairment and dementia pathophysiology is critical to identify preclinical populations and target potentially disease modifying interventions towards them. There are currently concerted efforts for such detection for Alzheimer's disease (AD). By contrast, the examination of cognitive markers and their relationship to biomarkers for Vascular Cognitive Impairment (VCI) is far less established, despite VCI being highly prevalent and often concomitantly presenting with AD. Critically, vascular risk factors are currently associated with the most viable treatment options via pharmacological and non-pharmacological intervention, hence early identification of vascular factors have important implications for modifying dementia disease trajectories. The aim of this review is to examine the current evidence of cognitive marker correlates to VCI pathology. We begin by examining midlife risk factors that predict VCI. Next, discuss preclinical cognitive hallmarks of VCI informed by insights from neuropsychological assessment, network connectivity and ERP/EEG experimental findings. Finally, we discuss limitations of current cognitive assessments and the need for future cognitive test development to inform diagnostic assessment. As well as, intervention outcome measures for preclinical VCI. In turn, these tests will inform earlier detection of vascular changes and allow implementation of disease intervention approaches.

All talk? Challenging the use of left-temporal EEG alpha oscillations as valid measures of verbal processing and conscious motor control.

This study tested the validity of EEG left-temporal alpha power and upper-alpha T7-Fz connectivity as indices of verbal activity and conscious motor control. Participants (n = 20) reached for, and transported, a jar under three conditions: a control condition and two self-talk conditions aimed at eliciting either task-unrelated verbal processing or task-related conscious control, while EEG and hand kinematics were recorded. Compared to the control condition, both self-talk conditions increased self-reported verbal processing, but only the task-related self-talk condition increased left-temporal activity (i.e., alpha power decreased). However, as cortical activity increased across the entire scalp topography, conscious control likely elicits a multitude of processes that may not be explained by left-temporal activity or verbal processing alone, but by a widespread decrease in neural efficiency. No significant effects for T7-Fz connectivity were detected. Results suggest that left-temporal EEG alpha oscillations are unlikely to uniquely reflect verbal processing during conscious motor control.

The effects of valid and invalid expectations about stimulus valence on behavioural and electrophysiological responses to emotional pictures.

Previous studies have shown that uncertainty about the expected valence of an upcoming stimulus modulates behavioural and neural responses to the stimulus. However, relatively little is known about how invalid emotion expectations (i.e. expecting a positive picture but seeing a negative picture) affect neural and behavioural responses. To investigate this, two experiments were conducted where participants viewed and rated the pleasantness of emotional pictures that were preceded by a cue. In Experiment 1, there were three cue conditions: uncertain, valid and invalid. The uncertain cue did not indicate the valence of the upcoming picture, whereas cues in the valid condition (70% of positive and negative cues) correctly indicated the valence of the upcoming picture. The remaining trials were invalid, where the valence of the picture differed from the expected valence. Behavioural results showed that invalidly cued negative pictures elicited more neutral valence ratings compared to validly cued pictures. In Experiment 2 we replicated the findings of Experiment 1, and in addition found an increased amplitude for the early (400-600 ms) portion of the late positive potential (LPP) for invalidly compared to validly cued pictures. Together, these results show that invalid expectations influence the neural and behavioural processing of subsequently presented emotional pictures, where invalidly cued pictures led to attenuated (i.e., more neutral) emotional responses, and enhanced early LPP amplitude, compared to validly cued pictures.