Multisubject Decomposition of Event-related Positivities in Cognitive Control: Tackling Age-related Changes in Reactive Control

Brain Topogr DOI 10.1007/s10548-016-0512-4 ORIGINAL PAPER Multisubject Decomposition of Event-related Positivities in Cognitive Control: Tackling Age-related Changes in Reactive Control Stefanie Enriquez-Geppert1,2 • Francisco Barceló2,3 Received: 23 January 2016 / Accepted: 2 August 2016 Ó The Author(s) 2016. This article is published with open access at Springerlink.com Abstract Age-related neurocognitive effects have been observed at different levels ranging from reduced amplitudes of even-related potentials and brain oscillations, to topography changes of brain activity. However, their association remains incompletely understood. We investigated time-frequency and time-course effects in functional networks underlying the P300 and their involvement in reactive control. Electroencephalographic (EEG) data of three different age groups (30 young: 18–26 years, 30 midaged: 49–58 years, 30 elderly: 65–75 years) was measured while they performed a cued colour/thickness switching task. Neural data was analysed concerning the targets. To consider restart, mixing, and switching processes, the targetś position after a cue (first or third target) as well as their context in the single-task (distractor cue) or the mixed-task block (switch- or repeat cue) was analysed. P300 EEG data was decomposed by means of group-independent component and time-frequency analyses focusing on theta and beta oscillations. RTs generally slowed down with age (main effect group), and effects were specifically strong in targets after a switching cue (larger Cohens d). Peaking at around 300 ms, we detected five functionally independent networks reflecting the multicomponent process underlying task-switching. These networks differed in terms of their topography (parietal and frontal), their involvement in task processes (switch-specific, mixing-, restart-, and singletask processes) and in terms of frequency effects. All were affected by age, as indicated by amplitude changes of the target-P300 and power reductions most consistently shown in beta oscillations. Most extensive age-related changes were observed in one parietal network sensitive to mixing and restart processes. Changes included a topography shift, P300 and beta amplitudes, and were ongoing in the elderly group. Keywords Cognitive aging
P300
Frontalization
Theta and beta oscillations
Task-switching
Group ICA
Functional networks This is one of several papers published together in Brain Topography on the ‘‘Special Issue: Multisubject decomposition of EEG - methods and applications’’. Introduction Electronic supplementary material The online version of this article (doi:10.1007/s10548-016-0512-4) contains supplementary material, which is available to authorized users. & Stefanie Enriquez-Geppert 1 Department of Clinical and Developmental Neuropsychology, University of Groningen, Groningen, Netherlands 2 Department of Psychology, University of the Balearic Islands, Palma de Mallorca, Spain 3 Asociación de Neuropsicologia Balear, Palma de Mallorca, Spain Declines of Executive Functions in Aging We are currently facing periods of demographic change, which are characterized by pronounced aging due to higher life-expectancy worldwide (United Nations Development Programme 2004). While analysing the implications for health management, a crucial aspect is the cognitive decline associated with aging. Affected domains include episodic memory (Glisky et al. 2001), processing speed (Salthouse 1996), and executive functions (EFs) (Kramer et al. 1999; Bialystok 2006; Watson et al. 2010). EFs are 123 Brain Topogr regarded as especially imperative for success in daily life since they enable adaptive goal-oriented behaviour (Seiferth et al. 2007). In terms of aging, declines of EFs are known to reduce the success in everyday activities (Vaughan and Giovanello 2010) and to narrow the functional status in older adults (Bell-McGinty et al. 2002). Thus, it is clearly apparent that the investigation of agerelated changes in executive functioning and its underlying neural mechanisms is imperative in order to face the challenges of main trends in society. White matter integrity of axonal bundles has been shown to be decreased mostly in frontal regions (Moseley 2002; Pfefferbaum et al. 1994), and has been associated with poorer EFs performance (Grieve et al. 2007). The network implementing EFs (Niendam et al. 2012) seems to be affected similarly, as observed in grey matter declines of the highly interconnected midcingulate cortex (MCC) (Mann et al. 2011), which is considered as a network hub (Cavanagh et al. 2012). It therefore comes as no surprise that apart from structural changes, functional changes take also place in aging. Age-related Changes in Task Switching Posterior-to-anterior Brain Activity Shifts in Aging EFs are defined as a bundle of higher functions controlling lower functions. Of those, motor inhibition, conflict monitoring, memory updating and task switching are the most important and most independent functions (Miyake et al. 2000; Miyake and Friedman 2010; Brydges et al. 2014; Adrover-Roig et al. 2012). Task switching requires the flexible shift between two tasks, depending of context specific cues (Rogers and Monsell 1995; Meiran 2002). Typically, the alternation between two or more tasks is investigated in the mixed-task block and compared to the single-task block without any task switching. On a behavioural level, response prolongations have been observed that are associated to at least three different processes. Most known is local switching which takes place in target processing after a cue that indicates a task switch. Local switching can be differentiated from more general mixing processes, which refer to additional demands in the context of a mixed-task compared to single-task block. A third process is related to a restart mechanism, which describes response prolongations in targets directly following a cue regardless whether a switch is require (in a mixed-task block). Concerning cognitive aging, consistent effects have been shown in mixing processes (e.g., Karayanidis et al. 2011). Aging has been suggested to lead to reduced cognitive preparation or proactive control in cue-to-target intervals and to the enhanced usage of reactive control processes (e.g., Jimura and Braver 2010). Furthermore, studies investigating adult lifespan trajectories hint to a qualitative change of task-switching at the age of 60 years. However, the neuronal changes are poorly understood. Generally, age-related cognitive decline has frequently been associated to different types of brain changes. Age-related Brain Changes Concerning neurotrophic factors, which are associated to neuroprotection and to cognition as well, age-related changes have been documented (Tumati et al. 2016). On a macrostructural level, aging is associated with reduced brain weight and volume (e.g., van Petten et al. 2004). 123 One of the most prominent observ (...truncated)