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August 1992 - June 1996
August 2001 - present
June 1996 - July 2001
Education
August 1981 - June 1990
November 1976 - November 1980
Publications
Publications (326)
Background: Aging is associated with progressive cognitive decline, as well as increased prevalence of cardiometabolic risk factors and reduced cardiorespiratory fitness. In fact, reduced cardiometabolic health and cardiorespiratory fitness are both associated with a decline in cognitive functioning. This study examines the common and distinct cont...
White matter (WM) microstructural health declines with increasing age, with evidence suggesting that improved cardiorespiratory fitness (CRF) may mitigate this decline. Specifically, higher fit older adults tend to show preserved WM microstructural integrity compared to their lower fit counterparts. However, the extent to which fitness and aging in...
Objective To examine the acute and chronic effects of reducing prolonged sedentary time (ST) with physical activity (PA) on cognitive and brain health.
Design Systematic review and meta-analysis.
Data sources PubMed, Scopus, CINAHL, PsycINFO, SPORTDiscus, Web of Science, and ProQuest Dissertation and Theses.
Eligibility criteria Randomised contr...
White matter (WM) microstructural health declines with increasing age, with evidence suggesting that improved cardiorespiratory fitness (CRF) may mitigate this decline. Specifically, higher fit older adults tend to show preserved WM microstructural integrity compared to their lower fit counterparts. However, the extent to which fitness and aging in...
Event-related optical signals (EROS) measure fast modulations in the brain’s optical properties related to neuronal activity. EROS offer a high spatial and temporal resolution and can be used for brain–computer interface (BCI) applications. However, the ability to classify single-trial EROS remains unexplored. This study evaluates the performance o...
The broadband shape of the EEG spectrum, summarized using the slope of a 1/fx function, is thought to reflect the balance between excitation and inhibition in cortical regions (E:I balance). This balance is an important characteristic of neural circuits and could inform studies of aging, as older adults show a relative deficit in inhibitory activit...
Cerebrovascular support is critical for healthy cognitive aging--arterial stiffness (arteriosclerosis) has been linked to heightened risks for cognitive decline, and ultimately for Alzheimer's disease and other forms of dementia. Conversely, neurovascular health is supported by lifestyle factors, including cardiorespiratory fitness. Here, capitaliz...
Automatic segmentation methods for in vivo magnetic resonance imaging are increasing in popularity because of their high efficiency and reproducibility. However, automatic methods can be perfectly reliable and consistently wrong, and the validity of automatic segmentation methods cannot be taken for granted. Quality control (QC) by trained and reli...
A brain–computer interface (BCI) allows users to control external devices through brain activity. Portable neuroimaging techniques, such as near-infrared (NIR) imaging, are suitable for this goal. NIR imaging has been used to measure rapid changes in brain optical properties associated with neuronal activation, namely fast optical signals (FOS) wit...
The broadband shape of the EEG spectrum, summarized using a 1/ f x function, is thought to reflect the balance between excitation and inhibition in cortical regions (E:I balance). This balance is an important characteristic of neural circuits and could inform studies of aging, as older adults show a relative inhibitory activity deficit. Thus far, n...
EEG alpha power varies under many circumstances requiring visual attention. However, mounting evidence indicates that alpha may not only serve visual processing, but also the processing of stimuli presented in other sensory modalities, including hearing. We previously showed that alpha dynamics during an auditory task vary as a function of competit...
EEG alpha power varies under many circumstances requiring visual attention. However, mounting evidence indicates that alpha may not only serve visual processing, but also the processing of stimuli presented in other sensory modalities, including hearing. We previously showed that alpha dynamics during an auditory task vary as a function of competit...
In this review we start from the assumption that, to fully understand cognitive aging, it is important to embrace a holistic view, integrating changes in bodily, brain, and cognitive functions. This broad view can help explain individual differences in aging trajectories and could ultimately enable prevention and remediation strategies. As the titl...
Research into the nature of 1/f-like, nonoscillatory electrophysiological activity has grown exponentially in recent years in cognitive neuroscience. The shape of this activity has been linked to the balance between excitatory and inhibitory neural circuits, which is thought to be important for information processing. However, to date, it is not kn...
Since its beginnings in the early 20th century, the psychophysiological study of human brain function has included research into the spectral properties of electrical and magnetic brain signals. Now, dramatic advances in digital signal processing, biophysics, and computer science have enabled increasingly sophisticated methodology for neural time s...
In the face of multiple sensory streams, there may be competition for processing resources in multimodal cortical area devoted to establishing representations. In such cases, alpha oscillations may serve to maintain the relevant representations and protect them from interference, whereas theta band activity may facilitate their updating when needed...
Introduction
Approximately 40% of late-life dementia may be prevented by addressing modifiable risk factors, including physical activity and diet. Yet, it is currently unknown how multiple lifestyle factors interact to influence cognition. The ACTIVate Study aims to (1) explore associations between 24-hour time-use and diet compositions with change...
Research into the nature of 1/ f -like, non-oscillatory electrophysiological activity has grown exponentially in recent years in cognitive neuroscience. The shape of this activity has been linked to the balance between excitatory and inhibitory neural circuits, which is thought to be important for information processing. However, to date, it is not...
In the face of multiple sensory streams, there may be competition for processing resources in multimodal cortical area devoted to establishing representations. In such cases, alpha oscillations may serve to maintain the relevant representations and protect them from interference, whereas theta oscillations may facilitate their updating when needed....
Introduction
Approximately 40% of late-life dementia may be prevented by addressing modifiable risk factors, including physical activity and diet. Yet, it is currently unknown how multiple lifestyle factors interact to influence cognition. The ACTIVate Study aims to 1) Explore associations between 24-hour time-use and diet compositions with changes...
It is well-established that younger adults prioritize information accrued during different stages of stimulus evaluation (“early” versus “late”) to optimize performance. The extent to which older adults flexibly adjust their processing strategies, however, is largely unexplored. Twenty-four younger and twenty-four older participants completed a cue...
The link between spatial (where) and temporal (when) aspects of the neural correlates of most psychological phenomena is not clear. Elucidation of this relation, which is crucial to fully understand human brain function, requires integration across multiple brain imaging modalities and cognitive tasks that reliably modulate the engagement of the br...
A bstract
When making financial choices, most people prefer smaller but more certain gains to larger but more uncertain ones with the same expected value (risk aversion). However, attitudes toward risk may vary greatly also within individuals (choice inconsistency). To examine the brain dynamics implementing risky and inconsistent decisions, we rec...
Typically, time-frequency analysis (TFA) of electrophysiological data is aimed at isolating narrowband signals (oscillatory activity) from broadband non-oscillatory (1/f) activity, so that changes in oscillatory activity resulting from experimental manipulations can be assessed. A widely used method to do this is to convert the data to the decibel...
The resting-state human electroencephalogram (EEG) power spectrum is dominated by alpha (8–12 Hz) and theta (4–8 Hz) oscillations, and also includes non-oscillatory broadband activity inversely related to frequency (1/f activity). Gratton proposed that alpha and theta oscillations are both related to cognitive control function, though in a compleme...
The process of aging includes changes in cellular biology that affect local interactions between cells and their environments and eventually propagate to systemic levels. In the brain, where neurons critically depend on an efficient and dynamic supply of oxygen and glucose, age‐related changes in the complex interaction between the brain parenchyma...
A wealth of evidence strongly suggests that regular physical activity can slow the progression of age-related declines in brain structure, brain function, and cognition. However, the mechanisms linking exercise-induced alterations in biomolecular signaling to neuroanatomical and neurophysiological changes, and, ultimately, to the long-term benefici...
Typically, time-frequency analysis (TFA) of electrophysiological data is aimed at isolating narrowband signals (oscillatory activity) from broadband non-oscillatory (1/ f ) activity, so that changes in oscillatory activity resulting from experimental manipulations can be assessed. A widely used method to do this is to convert the data to the decibe...
Significance
Continuous monitoring of cerebral hemodynamics is critical for safeguarding the healthy neurodevelopment of pediatric patients. This paper introduces a soft, flexible, miniaturized wireless system for real-time, continuous monitoring of systemic and cerebral hemodynamics for such purposes. Clinical studies on pediatric subjects with ag...
Cocoa flavanols protect humans against vascular disease, as evidenced by improvements in peripheral endothelial function, likely through nitric oxide signalling. Emerging evidence also suggests that flavanol-rich diets protect against cognitive aging, but mechanisms remain elusive. In a randomized double-blind within-subject acute study in healthy...
Available evidence suggests enhanced spontaneous emotion regulation in healthy aging, but the effects of specific strategies and the associated age-related neural mechanisms remain unclear. In this study, younger and older participants rated the emotional content of negative and neutral images, after explicit instructions or implicit priming to eng...
Resting-state EEG is dominated by sustained alpha oscillations, and low-frequency activities (short theta bursts and non-oscillatory 1/f slope). Resting alpha power decreases with age and correlates with intelligence. We propose that alpha facilitates proactive control (requiring task set maintenance in preparation for expected conditions), whereas...
Denoising fMRI data requires assessment of frame-to-frame head motion and removal of the biases motion introduces. This is usually done through analysis of the parameters calculated during retrospective head motion correction (i.e., ‘motion’ parameters). However, it is increasingly recognized that respiration introduces factitious head motion via p...
Age-related declines in cognition are associated with widespread structural and functional brain changes, including changes in resting-state functional connectivity and gray and white matter status. Recently we have shown that the elasticity of cerebral arteries also explains some of the variance in cognitive and brain health in aging. Here, we inv...
Despite evidence identifying the role of group membership in social cognition, the neural mechanisms associated with the perception and evaluation of nonverbal behaviors displayed by in-group versus out-group members remain unclear. Here, 42 white participants underwent electroencephalographic recording while observing social encounters involving d...
Denoising fMRI data requires assessment of frame-to-frame head motion and removal of the biases motion introduces. This is usually done through analysis of the parameters calculated during retrospective head motion correction (i.e., ‘motion’ parameters). However, it is increasingly recognized that respiration introduces factitious head motion via p...
Visual suppression by single-pulse transcranial magnetic stimulation (sTMS) has been attributed to interruptions of either feedforward or feedback activity in the visual stream. The relative timing of the C1 event related potential (ERP) and of the TMS suppression, taken from separate studies, supports an interruption of feedback. Here we probe the...
Decline in fluid abilities in normal aging is associated with increased white matter lesions, measured on T1-weighted images as white matter signal abnormalities (WMSAs). WMSAs are particularly evident in hypertensive older adults, suggesting vascular involvement. However, because hypertension is assessed systemically, the specific role of cerebral...
Aging is accompanied by widespread changes in brain tissue. Here, we hypothesized that head tissue opacity to near-infrared light provides information about the health status of the brain’s cortical mantle. In diffusive media such as the head, opacity is quantified through the Effective Attenuation Coefficient (EAC), which is proportional to the ge...
In Fig. 4c of this Article, the scale bar units were incorrectly stated as ‘μV’; the correct units are ‘mV’. The figure has now been amended accordingly.
In Fig. 4c of this Article originally published, the bottom y axis was incorrectly labelled as ‘MRI–ECG (μV)’; the correct label is ‘MRI/ECG’. In addition, in Fig. 4d, the bottom y axis was incorrectly labelled as ‘ECG (μV)’; the correct label is ‘ECG (mV)’. The scale bar units were also incorrectly stated as ‘mV’, the correct units are ‘μV’. The f...
Skin-interfaced medical devices are critically important for diagnosing disease, monitoring physiological health and establishing control interfaces with prosthetics, computer systems and wearable robotic devices. Skin-like epidermal electronic technologies can support these use cases in soft and ultrathin materials that conformally interface with...
Recent work has sought to describe the time-course of spoken word recognition, from initial acoustic cue encoding through lexical activation, and identify cortical areas involved in each stage of analysis. However, existing methods are limited in either temporal or spatial resolution, and as a result, have only provided partial answers to the quest...
Cognitive control (with the closely related concepts of attention control and executive function) encompasses the collection of processes that are involved in generating and maintaining appropriate task goals and suppressing task goals that are no longer relevant, as well as the way in which current goal representations are used to modify attention...
Preterm infants (born at 24–34 weeks of gestational age) suffer from a high incidence of neurological complications. Cerebrovascular lesions (intraventricular hemorrhages, IVH, and ischemic injury) due to the immaturity of the vascular system and its inability to adapt to the extra-uterine environment are the major causes of adverse neurological ou...
Aging is often accompanied by changes in brain anatomy and cerebrovascular health. However, the specific relationship between declines in regional cortical volumes and loss of cerebral arterial elasticity is less clear, as only global or very localized estimates of cerebrovascular health have been available. Here we employed a novel tomographic opt...
Research on the neural correlates of consciousness (NCC) has implicated an assortment of brain regions, ERP components, and network properties associated with visual awareness. Recently, the P3b ERP component has emerged as a leading NCC candidate. However, typical P3b paradigms depend on the detection of some stimulus change, making it difficult t...
Near infrared (NIR) light has been widely used for measuring changes in hemoglobin concentration in the human brain (functional NIR spectroscopy, fNIRS). fNIRS is based on the differential measurement and estimation of absorption perturbations, which, in turn, are based on correctly estimating the absolute parameters of light propagation. To do so,...
The seminal work of Grinvald et al. has paved the way for the use of intrinsic optical signals measured with reflection methods for the analysis of brain function. Although this work has focused on the absorption signal associated with deoxygenation, due to its detailed mapping ability and good signal-to-noise ratio, Grinvald's group has also descr...
Control-demanding tasks rely on communication among regions of the frontoparietal network, areas that undergo significant age-related decline. Here, we integrate data from brain anatomy, electrophysiology (ERPs), and optical imaging (event-related optical signals, EROS) to characterize the spatial and temporal dynamics of preparatory control proces...
Cerebrovascular health is important for maintaining a high level of cognitive performance, not only in old age, but also throughout the lifespan. Recently, it was first demonstrated that diffuse optical imaging measures of pulse amplitude and arterial compliance can provide estimates of cerebral arterial health throughout the cortex, and were assoc...
A concept for millimeter-scale, battery-free sensors for measuring heart rate and blood oxygenation in presented by J. A. Rogers and co-workers on page 1604373. Reflectance pulse oximetry data is devoid of motion artifacts when obtained by wireless near-field communication from various body locations. The concept bears excellent potential for be em...
Reaction Times and Error Rates (Noise Compatibility Effects) from Experiment 2 for each Instruction Condition.
Percent compatible choices in a probability-estimation task given by the explicit, partial-explicit, and implicit instructed subjects for all the cues.
(DOCX)
Reaction Times and Error Rates from Experiment 2 for each Instruction Condition.
Means (+ SEMs) from Experiment 1
(DOCX)
Reaction Times and Error Rates (Noise Compatibility Effects) from Experiment 1 for each Instruction Condition.
Percent compatible choices in a probability-estimation task given by the explicit, partial-explicit, and implicit instructed subjects for all the cues.
(DOCX)
Reaction Times and Error Rates from Experiment 1 for each Instruction Condition.
Means (+ SEMs) from Experiment 1
(DOCX)
Two experiments investigated competition between cues that predicted the correct target response to a target stimulus in a response conflict procedure using a flanker task. Subjects received trials with five-character arrays with a central target character and distractor flanker characters that matched (compatible) or did not match (incompatible) t...
Ethics Statement.
Ethics Statement.
(DOCX)
One of the key components of relational memory is the ability to bind together the constituent elements of a memory experience, and this ability is thought to be supported by the hippocampus. Previously we had shown that these relational bindings can be used to reactivate the cortical processors of an absent item in the presence of a relationally b...
Development of unconventional technologies for wireless collection and analysis of quantitative, clinically relevant information on physiological status is of growing interest. Soft, biocompatible systems are widely regarded as important because they facilitate mounting on external (e.g., skin) and internal (e.g., heart and brain) surfaces of the b...
Theories of brain plasticity propose that, in the absence of input from the preferred sensory modality, some specialized brain areas may be recruited when processing information from other modalities, which may result in improved performance. The Useful Field of View task has previously been used to demonstrate that early deafness positively impact...
Recent advances in materials, mechanics, and electronic device design are rapidly establishing the foundations for health monitoring technologies that have “skin-like” properties, with options in chronic (weeks) integration with the epidermis. The resulting capabilities in physiological sensing greatly exceed those possible with conventional hard e...
Recent studies suggest that cardiorespiratory fitness (CRF) mitigates the brain’s atrophy typically associated with aging, via a variety of beneficial mechanisms. One could argue that if CRF is generally counteracting the negative effects of aging, the same regions that display the greatest age-related volumetric loss should also show the largest b...
The human cerebral vasculature responds to changes in blood pressure and demands for oxygenation via cerebral autoregulation. Changes in cerebrovascular tone (vasoconstriction and vasodilation) also mediate the changes in blood flow measured by the BOLD fMRI signal. This cerebrovascular reactivity is known to vary with age. In two experiments, we d...
Diffuse optical tomography (DOT) provides data about brain function using surface recordings. Despite recent advancements, an unbiased method for estimating the depth of absorption changes and for providing an accurate three-dimensional (3-D) reconstruction remains elusive. DOT involves solving an ill-posed inverse problem, requiring additional cri...
INTRODUCTION This chapter reviews issues related to the analysis of psychophysiological data. It focuses on general questions relevant to a variety of techniques, rather than on specific issues related to individual methods. In this new edition we have modified this chapter to account for the fact that new techniques and research domains are rapidl...
In this chapter, we review research on the sensory and working memory changes that typically accompany normal aging, with the view that an examination of individual differences over the lifespan can illuminate some of the mechanisms underlying working memory processes. We also discuss the theoretical frameworks used to interpret these age-related c...
We review research investigating the reactivation of memory representations through the combined use of behavioral, event-related brain potential, and optical measures. We assume that (1) early stimulus processing creates memory representations in the same brain regions that participated in that processing; and (2) re-exposure to the same stimuli r...
When analyzing visual scenes, it is sometimes important to determine the relevant “grain” size. Attention control mechanisms may help direct our processing to the intended grain size. Here we used the event-related optical signal, a method possessing high temporal and spatial resolution, to examine the involvement of brain structures within the dor...
Information from different modalities is initially processed in different brain areas, yet real-world perception often requires the integration of multisensory signals into a single percept. An example is the McGurk effect, in which people viewing a speaker whose lip movements do not match the utterance perceive the spoken sounds incorrectly, heari...
Functional brain imaging techniques require accurate co-registration to anatomical images to precisely identify the areas being activated. Many of them, including diffuse optical imaging, rely on scalp-placed recording sensors. Fiducial alignment is an effective and rapid method for co-registering scalp sensors onto anatomy, but is quite sensitive...
In this editorial, I discuss the advantages of interpreting brain data in the context of other bodily systems. I also discuss current research challenges that may greatly benefit from a psychophysiological approach in which multiple methods-both peripheral and central-are used to improve our understanding of brain function, its underlying physiolog...