Regional cerebral blood flow increases during wakeful rest following cognitive training

Variability of physiological brain perfusion in healthy subjects - A systematic review of modifiers. Considerations for multi-center ASL studies

Quantitative measurements of brain perfusion are influenced by perfusion-modifiers. Standardization of measurement conditions and correction for important modifiers is essential to improve accuracy and to facilitate the interpretation of perfusion-derived parameters. An extensive literature search was carried out for factors influencing quantitative measurements of perfusion in the human brain unrelated to medication use. A total of 58 perfusion modifiers were categorized into four groups. Several factors (e.g., caffeine, aging, and blood gases) were found to induce a considerable effect on brain perfusion that was consistent across different studies; for other factors, the modifying effect was found to be debatable, due to contradictory results or lack of evidence. Using the results of this review, we propose a standard operating procedure, based on practices already implemented in several research centers. Also, a theory of 'deep MRI physiotyping' is inferred from the combined knowledge of factors influencing brain perfusion as a strategy to reduce variance by taking both personal information and the presence or absence of perfusion modifiers into account. We hypothesize that this will allow to personalize the concept of normality, as well as to reach more rigorous and earlier diagnoses of brain disorders.

A New Analysis of Resting State Connectivity and Graph Theory Reveals Distinctive Short-Term Modulations due to Whisker Stimulation in Rats

Resting state (RS) connectivity has been increasingly studied in healthy and diseased brains in humans and animals. This paper presents a new method to analyze RS data from fMRI that combines multiple seed correlation analysis with graph-theory (MSRA). We characterize and evaluate this new method in relation to two other graph-theoretical methods and ICA. The graph-theoretical methods calculate cross-correlations of regional average time-courses, one using seed regions of the same size (SRCC) and the other using whole brain structure regions (RCCA). We evaluated the reproducibility, power, and capacity of these methods to characterize short-term RS modulation to unilateral physiological whisker stimulation in rats. Graph-theoretical networks found with the MSRA approach were highly reproducible, and their communities showed large overlaps with ICA components. Additionally, MSRA was the only one of all tested methods that had the power to detect significant RS modulations induced by whisker stimulation that are controlled by family-wise error rate (FWE). Compared to the reduced resting state network connectivity during task performance, these modulations implied decreased connectivity strength in the bilateral sensorimotor and entorhinal cortex. Additionally, the contralateral ventromedial thalamus (part of the barrel field related lemniscal pathway) and the hypothalamus showed reduced connectivity. Enhanced connectivity was observed in the amygdala, especially the contralateral basolateral amygdala (involved in emotional learning processes). In conclusion, MSRA is a powerful analytical approach that can reliably detect tiny modulations of RS connectivity. It shows a great promise as a method for studying RS dynamics in healthy and pathological conditions.

Cerebral Perfusion Enhancing Interventions: A New Strategy for the Prevention of Alzheimer Dementia

Cardiovascular and cerebrovascular diseases are major risk factors in the development of cognitive impairment and Alzheimer's disease (AD). These cardio-cerebral disorders promote a variety of vascular risk factors which in the presence of advancing age are prone to markedly reduce cerebral perfusion and create a neuronal energy crisis. Long-term hypoperfusion of the brain evolves mainly from cardiac structural pathology and brain vascular insufficiency. Brain hypoperfusion in the elderly is strongly associated with the development of mild cognitive impairment (MCI) and both conditions are presumed to be precursors of Alzheimer dementia. A therapeutic target to prevent or treat MCI and consequently reduce the incidence of AD aims to elevate cerebral perfusion using novel pharmacological agents. As reviewed here, the experimental pharmaca include the use of Rho kinase inhibitors, neurometabolic energy boosters, sirtuins and vascular growth factors. In addition, a compelling new technique in laser medicine called photobiomodulation is reviewed. Photobiomodulation is based on the use of low level laser therapy to stimulate mitochondrial energy production non-invasively in nerve cells. The use of novel pharmaca and photobiomodulation may become important tools in the treatment or prevention of cognitive decline that can lead to dementia.

Neural reactivation links unconscious thought to decision-making performance

Brief periods of unconscious thought (UT) have been shown to improve decision making compared with making an immediate decision (ID). We reveal a neural mechanism for UT in decision making using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging. Participants (N = 33) encoded information on a set of consumer products (e.g. 48 attributes describing four different cars), and we manipulated whether participants (i) consciously thought about this information (conscious thought), (ii) completed a difficult 2-back working memory task (UT) or (iii) made an immediate decision about the consumer products (ID) in a within-subjects blocked design. To differentiate UT neural activity from 2-back working memory neural activity, participants completed an independent 2-back task and this neural activity was subtracted from neural activity occurring during the UT 2-back task. Consistent with a neural reactivation account, we found that the same regions activated during the encoding of complex decision information (right dorsolateral prefrontal cortex and left intermediate visual cortex) continued to be activated during a subsequent 2-min UT period. Moreover, neural reactivation in these regions was predictive of subsequent behavioral decision-making performance after the UT period. These results provide initial evidence for post-encoding unconscious neural reactivation in facilitating decision making.

Functional Brain Changes Following Cognitive and Motor Skills Training

Background. Functional neuroimaging is increasingly used in rehabilitation research to map the neural mechanisms subserving training targets. These data can inform intervention design and improve evaluation of treatment outcomes. Reliable neural markers may provide standard metrics of treatment impact and allow consideration of behavioral outcomes in the context of functional brain changes. Objective. To identify common patterns of functional brain changes associated with training across a diverse range of intervention protocols. Reliable brain changes could inform development of candidate neural markers to guide intervention research. Methods. Taking a quantitative meta-analytic approach, we review the functional neuroimaging studies of cognitive and motor skills training interventions in healthy young adults (N = 38). Results. Reliable decreases in functional brain activity from pretraining to posttraining were observed in brain regions commonly associated with cognitive control processes, including lateral prefrontal, left anterior inferior parietal lobule, and dorsal anterior cingulate cortex. Training-related increases were observed in the medial prefrontal cortex and posterior cingulate and angular gyrus, core regions of the default network. Activity within the subcortical striatum also showed reliable increases pretraining to posttraining. Conclusions. These data suggest that altered engagement of large-scale, spatially distributed cortical brain networks and subcortical striatal brain regions may serve as candidate neural markers of training interventions. The development of reliable metrics based on activity and functional connectivity among large-scale brain networks may prove fruitful in identifying interactions between domain-general and -specific changes in brain activity that affect behavioral outcomes.

The role of corpus callosum development in functional connectivity and cognitive processing

The corpus callosum is hypothesized to play a fundamental role in integrating information and mediating complex behaviors. Here, we demonstrate that lack of normal callosal development can lead to deficits in functional connectivity that are related to impairments in specific cognitive domains. We examined resting-state functional connectivity in individuals with agenesis of the corpus callosum (AgCC) and matched controls using magnetoencephalographic imaging (MEG-I) of coherence in the alpha (8-12 Hz), beta (12-30 Hz) and gamma (30-55 Hz) bands. Global connectivity (GC) was defined as synchronization between a region and the rest of the brain. In AgCC individuals, alpha band GC was significantly reduced in the dorsolateral pre-frontal (DLPFC), posterior parietal (PPC) and parieto-occipital cortices (PO). No significant differences in GC were seen in either the beta or gamma bands. We also explored the hypothesis that, in AgCC, this regional reduction in functional connectivity is explained primarily by a specific reduction in interhemispheric connectivity. However, our data suggest that reduced connectivity in these regions is driven by faulty coupling in both inter- and intrahemispheric connectivity. We also assessed whether the degree of connectivity correlated with behavioral performance, focusing on cognitive measures known to be impaired in AgCC individuals. Neuropsychological measures of verbal processing speed were significantly correlated with resting-state functional connectivity of the left medial and superior temporal lobe in AgCC participants. Connectivity of DLPFC correlated strongly with performance on the Tower of London in the AgCC cohort. These findings indicate that the abnormal callosal development produces salient but selective (alpha band only) resting-state functional connectivity disruptions that correlate with cognitive impairment. Understanding the relationship between impoverished functional connectivity and cognition is a key step in identifying the neural mechanisms of language and executive dysfunction in common neurodevelopmental and psychiatric disorders where disruptions of callosal development are consistently identified.

Prefrontal transcranial direct current stimulation changes connectivity of resting-state networks during fMRI

Transcranial direct current stimulation (tDCS) has been proposed for experimental and therapeutic modulation of regional brain function. Specifically, anodal tDCS of the dorsolateral prefrontal cortex (DLPFC) together with cathodal tDCS of the supraorbital region have been associated with improvement of cognition and mood, and have been suggested for the treatment of several neurological and psychiatric disorders. Although modeled mathematically, the distribution, direction, and extent of tDCS-mediated effects on brain physiology are not well understood. The current study investigates whether tDCS of the human prefrontal cortex modulates resting-state network (RSN) connectivity measured by functional magnetic resonance imaging (fMRI). Thirteen healthy subjects underwent real and sham tDCS in random order on separate days. tDCS was applied for 20 min at 2 mA with the anode positioned over the left DLPFC and the cathode over the right supraorbital region. Patterns of resting-state brain connectivity were assessed before and after tDCS with 3 T fMRI, and changes were analyzed for relevant networks related to the stimulation-electrode localizations. At baseline, four RSNs were detected, corresponding to the default mode network (DMN), the left and right frontal-parietal networks (FPNs) and the self-referential network. After real tDCS and compared with sham tDCS, significant changes of regional brain connectivity were found for the DMN and the FPNs both close to the primary stimulation site and in connected brain regions. These findings show that prefrontal tDCS modulates resting-state functional connectivity in distinct functional networks of the human brain.

Patterns of hemodynamic low-frequency oscillations in the brain are modulated by the nature of free thought during rest

During conscious rest, the mind switches into a state of wandering. Although this rich inner experience occupies a large portion of the time spent awake, how it relates to brain activity has not been well explored. Here, we report the results of a behavioral and functional magnetic resonance imaging (fMRI) study of the continuous resting state in 307 healthy participants. The analysis focused on the relationship between the nature of inner experience and the temporal correlations computed between the low-frequency blood oxygen level-dependent (BOLD) fluctuations (0.01-0.1 Hz) of five large-scale modules. The subjects' self-reported time spontaneously spent on visual mental imagery and/or inner language was used as the behavioral variable. Decreased temporal correlations between modules were revealed when subjects reported more time spent thinking in mental images and inner language. These changes segregated the three modules supporting inner-oriented activities from those associated with sensory-related and externally guided activities. Among the brain areas associated with inner-oriented processing, the module including the lateral parietal and frontal regions (commonly described as being engaged in the manipulation and maintenance of internal information) was implicated in the majority of these effects. The preponderance of segregation appears to be the signature of the spontaneous sequence of thoughts during rest that are not constrained by logic, causality, or even a rigorous temporal organization. In other words, though goal-directed tasks have been demonstrated to rely on specific regional integration, mind wandering can be characterized by widespread modular segregation. Overall, the present study provides evidence that modulation of spontaneous low-frequency fluctuations in the brain is at least partially explained by spontaneous conscious cognition while at rest.

Neuronal effects following working memory training

There is accumulating evidence that training working memory (WM) leads to beneficial effects in tasks that were not trained, but the mechanisms underlying this transfer remain elusive. Brain imaging can be a valuable method to gain insights into such mechanisms. Here, we discuss the impact of cognitive training on neural correlates with an emphasis on studies that implemented a WM intervention. We focus on changes in activation patterns, changes in resting state connectivity, changes in brain structure, and changes in the dopaminergic system. Our analysis of the existing literature reveals that there is currently no clear pattern of results that would single out a specific neural mechanism underlying training and transfer. We conclude that although brain imaging has provided us with information about the mechanisms of WM training, more research is needed to understand its neural impact.

[The neural impact of cognitive training]

Tracing the connections from brain functions to education is a major goal of modern neuroscience. By providing insights into the abilities and constraints of the learning brain, neuroscience can help to explain why some learning environments work while others fail. The results presented here provide the first insights into neuropedagogy of reasoning.

User-friendly cognitive training for the elderly: a technical report

OBJECTIVE

This article presents a system that implements a cognitive training program in users' homes. The system comprises various applications designed to create a daily brain-fitness regime.

MATERIALS AND METHODS

The proposed mental training system uses television and a remote control specially designed for the elderly. This system integrates Java applications to promote brain-fitness training in three areas: arithmetic, memory, and idea association. The system comprises the following: Standard television set, simplified wireless remote control, black box (system's core hardware and software), brain-fitness games (language Java), and Wi-Fi-enabled Internet-connected router. All data from the user training sessions are monitored through a control center. This control center analyzes the evolution of the user and the proper performance of the system during the test.

RESULTS

The implemented system has been tested by six healthy volunteers. The results for this user group demonstrated the accessibility and usability of the system in a controlled real environment. The impressions of the users were very favorable, and they reported high adaptability to the system. The mean score for usability and accessibility assigned by the users was 3.56 out of 5 points. The operation stress test (over 200 h) was successful.

CONCLUSION

The proposed system was used to implement a cognitive training program in users' homes, which was developed to be a low-cost tool with a high degree of user interactivity. The results of this preliminary study indicate that this user-friendly system could be adopted as a form of cognitive training for the elderly.

A cognitive training intervention increases resting cerebral blood flow in healthy older adults

Healthy aging is typically accompanied by some decline in cognitive performance, as well as by alterations in brain structure and function. Here we report the results of a randomized, controlled trial designed to determine the effects of a novel cognitive training program on resting cerebral blood flow (CBF) and gray matter (GM) volume in healthy older adults. Sixty-six healthy older adults participated in 8 weeks of either a training program targeting attention and distractibility or an educational control program. This training program produced significantly larger increases in resting CBF to the prefrontal cortex than the control program. Increases in blood flow were associated with reduced susceptibility to distraction after training, but not with alterations in GM volume. These data demonstrate that cognitive training can improve resting CBF in healthy older adults and that cerebral perfusion rates may be a more sensitive indicator of the benefits of cognitive training than volumetric analyses.

The resting state questionnaire: An introspective questionnaire for evaluation of inner experience during the conscious resting state

We designed a semi-structured questionnaire for the introspective evaluation of inner experience of participants undergoing functional magnetic resonance imaging (fMRI) in the resting state. This resting state questionnaire (ReSQ) consists of 62 items organized by five main types of mental activity: visual mental imagery (IMAG); inner language (LANG), split into two subtypes, inner speech (SPEE) and auditory mental imagery (AUDI); somatosensory awareness (SOMA); inner musical experience (MUSI); and mental manipulation of numbers (NUMB). For IMAG and LANG, additional questions estimated association of such activities with ongoing learning, retrospective memories, or prospective thoughts. Using a 0-100% scale, the participant quantitatively rated the proportion of time spent in each mental activity during the resting state fMRI acquisition. A total of 180 healthy volunteers completed the ReSQ immediately after being scanned with fMRI while at rest. Of these, 66% exhibited dominance of a type of mental activity at rest (IMAG: 35%; LANG: 17%; SOMA: 7%; MUSI: 6%; NUMB: 1%). A majority of participants reported either retrospective memories (82%) or prospective thoughts (78%), with 58% of participants reporting both in at least one type of mental activity. Thoughts related to ongoing learning were low (37% of participants). The present results are consistent with those of previous studies investigating inner experience in a natural environment. In conclusion, we provide a robust and easy-to-implement tool for the exploration of mental activities during rest of healthy participants undergoing fMRI. This tool relies on normative data acquired from a 180-participant sample balanced for sex and handedness.