Electrophysiological Advances on Multiple Object Processing in Aging

EEG research conducted in the past five years on multiple object processing has begun to define how the aging brain tracks the numerosity of the objects presented in the visual field for different goals. We review the recent EEG findings in healthy older individuals (age range: 65-75 years approximately) on perceptual, attentional and memory mechanisms- reflected in the N1, N2pc and Contralateral Delayed Activity components of the EEG, respectively- during the execution of a variety of cognitive tasks requiring simultaneous processing of multiple elements. The findings point to multiple loci of neural changes in multi-object analysis, and suggest the involvement of early perceptual mechanisms, attentive individuation and WM operations in the neural and cognitive modification due to aging. However, the findings do not simply reflect early impairments with a cascade effect over subsequent stages of stimulus processing, but in fact highlight interesting dissociations between the effects occurring at the various stages of stimulus processing. Finally, the results on older adults indicate the occurrence of neural overactivation in association to good levels of performance in easy perceptual contexts, thus providing some hints on the existence of compensatory phenomena that are associated with the functioning of early perceptual mechanisms

Learning by task repetition enhances object individuation and memorization in the elderly

A decline in visuospatial Working Memory (vWM) is a hallmark of cognitive aging across various tasks, and facing this decline has become the target of several studies. In the current study we tested whether older adults can benefit from task repetition in order to improve their performance in a vWM task. While learning by task repetition has been shown to improve vWM performance in young adulthood, little is known on whether a similar enhancement can be achieved also by the aging population. By combining different behavioral and electrophysiological measures, we investigated whether practicing a specific task (delayed match-to-sample judgement) over four consecutive sessions could improve vWM in healthy aging, and which are the neurophysiological and cognitive mechanisms modulated by learning. Behavioral data revealed that task repetition boosted performance in older participants, both in terms of sensitivity to change (as revealed by d' measures) as well as capacity estimate (as measured by k values). At the electrophysiological level, results indicated that only after task repetition both target individuation (as evidenced by the N2pc) and vWM maintenance (as reflected by the CDA) were modulated by target numerosity. Our results suggest that repetition learning is effective in enhancing vWM in aging and acts through modifications at different stages of stimulus processing

Estudo dos cambios na actividade eléctrica cerebral asociados ao declive na memoria de traballo visoespacial, no envellecemento san e no deterioro cognitivo leve

Traballo Fin de Grao en Psicoloxía. Curso 2017-2018[GL] O deterioro cognitivo leve (DCL) é un estadio intermedio entre o envellecemento san e o que cursa con demencia. No presente estudo seleccionáronse dous grupos de participantes (Control san e DCL) nos que se estudaron os cambios na conduta e na actividade eléctrica cerebral ante unha tarefa de memoria de traballo (MT) visoespacial, con tres niveis de dificultade (fácil, intermedia e difícil), determinada pola cantidade de items a codificar en MT. Os obxectivos principais foron a obtención dos índices condutuais e psicofisiolóxicos do procesamento da información na fase de codificación en MT, e a comprobación da existencia de diferenzas nestes índices entre o grupo control (envellecemento san) e o grupo con DCL. Nos parámetros condutuais observáronse incrementos coa idade nos tempos de reacción, así como diferenzas entre o grupo DCL e o Control, con un menor porcentaxe de acertos no primeiro, o que indica que a idade cursa cunha lentificación dos procesos atencionais e de MT nos dous grupos e que o grupo con DCL mostra unha menor eficiencia nos procesos de MT. En canto ós compoñentes dos potenciais evocados (PE) estudados, observáronse P1, P2, N2 e P300 nos dous grupos; pero non se atopou ningunha diferenza significativa entre grupos, nas amplitudes nin nas latencias deses compoñentes, o que contrasta cos estudos previos revisados. Discútese que a ausencia de efecto Grupo nos parámetros dos PE podería deberse a que o protocolo de preprocesado dos datos EEG foi moi riguroso na eliminación dos artefactos; por outra, os criterios de exclusión dos datos EEG en canto a número mínimo de épocas válidas de cada categoría, contribuíu a unha redución drástica do tamaño da mostra.[EN] Mild Cognitive Impairment is an intermediate stage between healthy ageing and ageing with dementia. Two groups of participants (healthy control group and MCI) were selected for this study in which behavioural changes and brain electrical activity were studied utilising a visual-spatial working memory task with three difficulty levels: easy, intermediate and difficult, which were determined by the number of codified items in the working memory task. The key objectives were obtaining the behavioural and psycho-physiological indexes of information processing in the codification stage of the working memory task, and the verification of the existence of differences in these indexes between the control group and the MCI group. In the behavioral parameters, age-related increases were observed in reaction times, as well as differences between the MCI group and the control group, with a lower percentage of accuracy in the first group, which indicates that ageing entails a slowdown of attention processes and working memory in both groups, with the MCI group showing a lower efficiency in the WM processes.As regards the components of the event-related potentials that were studied, P1, P2, N2 and P300 were observed in both groups; but no significant differences were noted, neither in the amplitude nor in the latency of these components between the groups that were studied, which contrasts with the previously reviewed studies. It is discussed that the absence of the group effect in the ERP could be due to the fact that the reprocessing protocol of EEG data was strict in the removal of the artefacts; on the other hand, the deferral criteria of EEG data in terms of a minimum number of valid trials in each category, contributed to a drastic reduction of the size of the sample

A multimodal approach to the study of healthy and pathoogical aging

Il presente lavoro si è concentrato sui meccanismi neurofisiologici e comportamentali legati all'invecchiamento sano e patologico. Il primo studio ha esplorato le dinamiche comportamentali ed elettrofisiologiche (N2pc e CDA) del processamento di oggetti multipli in pazienti con decadimento cognitivo lieve ed in pazienti con malattia di Alzheimer (AD), al fine di identificare marcatori neurofisiologici per distinguere l’invecchiamento normale da quello patologico. I dati suggeriscono che la CDA può essere un marcatore neurale utile sia per distinguere tra invecchiamento sano e patologico che per caratterizzare le diverse fasi lungo il continuum della malattia di Alzheimer, diventando un biomarcatore per la diagnosi precoce di AD. Il secondo studio ha valutato la possibilità di applicare un protocollo di neuroriabilitazione non invasiva, mediante stimolazione elettrica transcranica (tES), per migliorare le prestazioni cognitive aumentando il livello di eccitazione. Sia le prestazioni comportamentali ad un compito di memoria a breve termine che gli indici di attivazione fisiologica autonomica (dilatazione pupillare e conduttanza cutanea) sono stati studiati in un gruppo di soggetti giovani sani e in un gruppo di soggetti anziani sani. Nei giovani, entrambe le risposte comportamentali e fisiologiche non sono state modulate dall’applicazione della tES. Negli anziani, invece, la stimolazione reale ha indotto la rievocazione di una proporzione significativamente più bassa di stimoli ad alta salienza, rispetto alla condizione sham, suggerendo una riduzione della capacità di memoria. Gli indici fisiologici risultano inaffidabile nei partecipanti anziani e non possono essere utilizzati per trarre conclusioni definitive sulle modulazioni indotte dalla tES sul livello di eccitazione. Questi risultati hanno mostrato che l’applicazione della tES, durante un compito di memoria a breve termine, modulano diversamente le prestazioni comportamentali nei partecipanti giovani ed in quelli anziani.The present work focused on neurophysiological and behavioral mechanisms related to healthy and pathological aging. The first study explored the behavioral and electrophysiological dynamics (N2pc and CDA) of multiple object processing in mild cognitive impairment and Alzheimer's disease (AD) patients to identify neurophysiological markers able to differentiate normal from pathological aging. Data suggested that CDA may be a useful neural signature to both distinguish between healthy and pathological aging and characterize the different stages along the AD continuum, possibly becoming a reliable candidate for an early diagnostic biomarker of AD pathology. The second study evaluated the possibility to apply a non-invasive neurorehabilitation protocol, by means of transcranial electrical stimulation (tES), to improve cognitive performance by increasing the level of arousal. Both the behavioral performance to a short term memory task and indexes of autonomic physiological activation (pupillary dilatation and skin conductance) were investigated in a group of healthy young subjects and in a group of healthy elderly subjects. In young, both behavioural and physiological responses were not modulated by tES application. In elderly, instead, real tES induced the report of a significant lower proportion of high salient stimuli, compared to the sham condition, suggesting a reduction of the memory span. The physiological indexes resulted unreliable in elderly participants and they could not be used to draw firm conclusions on the tES modulations of the level of arousal. These results showed that bursts of tES, applied during a short term memory task, differently modulated behavioural performance in young and elderly participants

Perceptual and Cognitive Load in Autism – An Electrophysiological and Behavioural Approach

Attention is a fundamentally important cognitive process and is required to efficiently navigate the world. Whilst altered attentional processes have been frequently observed in autistic people the differences seen suggest that attentional processes are different, however not necessarily deficient. In fact, aspects of superior visual perceptual ability and enhanced perceptual capacity have frequently been reported. The goal of the present thesis was to extend our knowledge of enhanced perceptual capacity under the framework of the Load Theory and to extend the findings to more active components of attention. To address this aim, the first three empirical studies I conducted, assessed selective and executive attention in autism and in a fourth study I investigated the feasibility of a neurofeedback intervention. Specifically, in Chapter 2, I used behavioural markers of congruency effects to consider whether cognitive capacity would be increased for autistic people, analogous to the enhanced perceptual capacity previously reported. In Chapter 3, I investigated electrophysiological aspects of visual working memory capacity and filtering efficiency. The findings were further expanded upon in Chapter 4 by directly contrasting visual working memory capacity and perceptual capacity using electrophysiological markers. Finally, I sought to assess whether practical steps could be taken to address altered attention experienced by autistic adults. The feasibility of an online neurofeedback intervention was investigated to assess whether aspects of attention and mental health could be improved through the training programme (Chapter 5). The findings of the thesis were then summarised and further discussed, highlighting the contribution to the autism attention literature and offering practical recommendations to harness attentional strengths in autism

The interplay between attention, working memory, and linked neural signatures in visual tracking and inhibition

The aims of this thesis began with investigating whether inattentional blindness was associated with a propensity for lower sensitivity to semantic violations in image textures. Inattentional blindness has recently been investigated through methods such as manipulation of low-level image statistics in artificial textures. However, work in this thesis aimed to transition such research into more natural contexts. Whilst a variety of methods were explored, results specifically related to inattentional blindness and working memory capacity remained inconclusive. Therefore, work in this thesis moved from investigating differences across inattentional blindness groups to how potential strategies of object tracking and relationships to working memory capacity can influence tracking performance. Results from the first half of this thesis provide novel insights into methods that can help to investigate sensitivity to distractors in a naturalistic setting, with both behavioural and neural data. This shift away from investigating inattentional blindness to patterns of tracking across working memory capacity also coincided with a shift to linear mixed effects modelling. This allowed the thesis to remove any artificial grouping through median scores of capacities, and instead focus more on sensitivity across the spectrum. Over five tracking studies, a number of findings suggest of differences across working memory capacity can compensate in performance for such capacity limitations. Findings also suggest that participants, regardless of capacity, employ a post-probe approximation estimation when tracking targets over a trial gap, as opposed to active tracking. Results from the tracking studies emphasise the differing approaches that individuals with varying working memory employ when tracking multiple and single objects