фМРТ-исследования в парадигме сокрытия информации: данные об активности мозжечка

Functional magnetic resonance imaging (fMRI) has become an exceedingly popular technique for studies of human brain activity. Typically, fMRI is performed with >3-mm sampling, so that the imaging data can be regarded as two-dimensional samples that roughly average through the typically 1.5—4-mm thickness of cerebral cortex. The use of higher spatial resolutions, <1.5-mm sampling, complicates the use of fMRI, as one must now consider activity variations within the depth of the brain. We present a set of surface-based methods to exploit the use of high-resolution fMRI for depth analysis. These methods utilize white-matter segmentations coupled with deformable-surface algorithms to create a smooth surface representation at the gray-white interface. These surfaces provide vertex positions and surface normals, vector references for depth calculations. That information enables averaging schemes that can increase contrast-to-noise ratio, as well as permitting the direct analysis of depth profiles of functional activity in the human brain.

Proteoglycans (PGs) are widely expressed in all areas of the brain. In this study, the keratan sulfate-containing PGs (KS-PGs) from cerebrum (CB), cerebellum (CL) and brainstem (BS) of young sheep brain were isolated, purified and characterized. The amount of KS-PGs in CL was significantly lower than that in CB and BS. KS-PGs were characterized by increased extent of glycosylation and heterogeneity of KS chains in CL. Western blot analyses demonstrated the presence of the KS-PGs phosphacan, SV2A and SV2B isoforms of synaptic vesicle proteoglycan in all three areas of the young sheep brain. Phosphacan predominated in BS and CB, showing significant molecular heterogeneity. SV2A and SV2B were found in two forms of high and low molecular sizes according to their extent of glycosylation in sheep brain. SV2A predominated in CL, where forms with very high molecular sizes were detected. Immunohistochemical examination revealed that SV2A was localized in the extracellular matrix of both gray and white matter. In contrast, phosphacan and SV2B were mainly localized in the white matter in all brain regions. The results of the present study demonstrated that KS-PGs are present in the three areas of the sheep brain, showing significant variations in their content, structure and localization among the distinct areas. These differences may be important for the physiology of the brain.

Functional magnetic resonance imaging (fMRI) is a unique window to the brain, enabling scientists to follow changes in brain activity in response to hormones, ageing, environment, drugs of abuse and other stimuli. There are two features that make fMRI unique when compared with other imaging modalities used in behavioural neuroscience. First, it can be entirely noninvasive: each animal can serve as its own control over the natural course of its life, vital for following neuroadaptation and other developmental processes critical to understanding behaviour. Second, fMRI has the spatial and temporal resolution to observe patterns of neuronal activity across the entire brain in less than a minute. Although fMRI does not have the cellular spatial resolution of immunostaining, nor the millisecond temporal resolution of electrophysiology, synchronised changes in neuronal activity across multiple brain areas seen with functional MRI can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviours. Thus, fMRI affords a systems approach to the study of the brain, complementing and building from other neurobiological techniques to understand how behaviour is organised across multiple brain regions. In this review, we present a general background to fMRI and the different imaging modalities that can be used in fMRI studies. Included are examples of the application of fMRI in behavioural neuroscience research, along with discussion of the advantages and disadvantages of this technology.

Author response: A unified neural account of contextual and individual differences in altruism

Objective To observe and compare the effects of acupuncture and acupuncture plus speech therapy on activation of the brain areas in aphasic patients by use of oxygenation level dependent-functional magnetic resonance imaging (BOLD-fMRI).Methods Twenty patients with aphasia caused by stroke were randomized into two groups by use of random number table (10 cases in each group):an experimental group subject to acupuncture treatment combined with speech therapy,and a control group subject to speech therapy only.All the cases were dextromanuality.On admission and after 1 month of treatment,BOLD-fMRI was used to test signals of the activated brain areas of both group,and Aphasia Battery of the Chinese (ABC) was employed to evaluate the changes of speech ability of the patients.Results During the study,1 case from control group was unable to do the post-intervention evaluation due to onset of the second stroke.The effective rates of the control and experimental group were 55.56％ and 100.00％,respectively,and recovery of verbal ability in experimental group was significantly better than in control group (P ＜ 0.05).The active volume and extent in brain were significantly increased in both groups (P ＜0.05),and a comparison between the two groups showed that the changes in activation volume and extent of the brain were significantly greater extensive in experimental group than in the control group,especially in bilateral frontal lobe,cuneus,posterior cingulate gyrus,lingual gyrus,occipital lobe,splenium of corpus callosum,cerebellar hemisphere,and the left precentral gyrus,post-central gyrus,paracentral lobule,temporal lobes,angular gyrus,precuneus,and the right hippocampus,parahippocampus gyrus.Conclusion Acupuncture combined with speech therapy could cause changes in activation patterns of the brain areas,which may contribute to the improvement of verbal ability of the aphasic patients. Key words: Functional magnetic resonance imaging; Stroke; Aphasia; Acupuncture

To study the toxicity of methomyl to acetylcholinesterase (AChE) in different regions. The optimal temperature and time for measurement of AChE activity were determined in vitro. The dose- and time-response relationships of methomyl with AChE activity in human erythrocyte membrane, rat erythrocyte membrane, cortical synapses, cerebellar synapses, hippocampal synapses, and striatal synapses were evaluated. The half maximal inhibitory concentration (IC50) and bimolecular rate constant (K) of methomyl for AChE activity in different regions were calculated, and the type of inhibition of AChE activity by methomyl was determined. AChE achieved the maximum activity at 370 °C, and the optimal time to determine initial reaction velocity was 0-17 min. There were dose- and time-response relationships between methomyl and AChE activity in the erythrocyte membrane and various brain areas. The IC50 value of methomyl for AChE activity in human erythrocyte membrane was higher than that in rat erythrocyte membrane, while the Ki value of methomyl for AChE activity in rat erythrocyte membrane was higher than that in human erythrocyte membrane. Among synapses in various brain areas, the striatum had the highest IC50 value, followed by the cerebellum, cerebral cortex, and hippocampus, while the cerebral cortex had the highest Ki value, followed by the hippocampus, striatum, and cerebellum. Lineweaver-Burk diagram demonstrated that with increasing concentration of methomyl, the maximum reaction velocity (Vmax) of AChE decreased, and the Michaelis constant (Km) remained the same. Methomyl is a reversible non-competitive inhibitor of AChE. AChE of rat erythrocyte membrane is more sensitive to methomyl than that of human erythrocyte membrane; the cerebral cortical synapses have the most sensitive AChE to methomyl among synapses in various brain areas.

Objective To investigate the swallow-related brain areas in normal adults with different experimental swallow tasks using founctional MRI (fMRI). Methods Eight healthy volunteers received volitional and reflexive water swallowing during fMRI studies. SPM2 software was used to postprocess functional data and display activated brain mapping. Paired t-test was used to compare the activated brain volume and increased signal of each hemisphere in two swallowing tasks. Results Bilateral primary sensorimotor cortex, premotor cortex, anterior cingnlated gyrus, insular, prefrontal area, posterior parietal lobe, temporal gyms , basal ganglion and cerebellum were detected in volitional water swallowing. However, only few brain areas such as bilateral primary sensorimotor cortex, posterior parietal lobe, frontal opercnlum were activated in reflexive water swallowing task. Volitional swallowing tasks activated much more brain volumes [1213±110 (left) and 1969±133 (right) vs 488±45 (left) and 398±35 (right), in pixels] and increase in signals [4.4±0.4 (left) and 4.1±0.2 (right) vs 2.6±0.3 (left) and 2.5±1.2 (right) at sensorimotor areas, 1.2±0.5 (left) and 1.5±0.6 (right) vs 0.6±0.4 (left) and 0.2±0.1 (right) at insular lobes] than those in reflexive tasks. Different lateralization in activation brain area was observed in swallowing tasks. Lateral index was ( - 16 ±9) % and ( 11 ±5 ) % respectively in volitional and reflexive water swallowing tasks. Conclusions Volitional swallowing task activates much more brain regions and brain volumes as compared to reflexive tasks. The different activated regions between volitional and reflexive swallowing tasks maybe relate to brain activities such as intent, planning, urge and possibly passion during volitional swallowing. Key words: Swallow; Magnetic resonance imaging; Function; Volition; Reflex

*Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin, U.S.A.; †University Hospital Gent, Gent, Belgium; ‡Departments of Diagnostic Radiology and Neurosurgery, Yale University, New Haven, Connecticut; §Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; Clinical Epilepsy Section, National Institutes of Health, Bethesda, Maryland; ¶Department of Radiology, Mayo Clinic, Rochester, Minnesota; and **Department of Neurology, Medical College of Georgia, Augusta, Georgia, U.S.A.

Functional investigation of neural circuits in larval zebrafish

The Face Network: Overextended? (Comment on: “Let's face it: It's a cortical network” by Alumit Ishai)

Cognitive events rely on rapid information flow among interdependent brain areas. Estimates from single-unit physiology in monkeys and human electrophysiological scalp recordings suggest communication between brain areas takes place on the order of tens to hundreds of milliseconds (1). A challenge to the study of human cognition has been to develop noninvasive methods to measure the temporal orchestration of information processing. Limitations were initially imposed by the imaging devices themselves. Positron emission tomography (PET) methods based on short-lived isotopes, for example, take about a minute to make a measurement (2). The advent of functional MRI (fMRI) changed the landscape of human brain imaging by providing a tool that can make measurements on the sub-second time scale (3, 4). However, the use of fMRI solves only part of the problem. An even greater challenge surrounds the temporal sluggishness of the correlates of neuronal activity to which modern imaging devices are sensitive. Most fMRI studies measure brain activity indirectly through changes in blood vasculature that accompany neuronal activity. Although the exact origins of these vascular changes are debated (5, 6), they are temporally slow, begin seconds after a neuronal event, and last for tens of seconds (7). For isolated cognitive acts, which can often be completed in under a second, the sluggish nature of the measured response means that a signal is detected after the neuronal event has subsided. It is against this backdrop that the work of Bellgowan et al. in a recent issue of PNAS (8) can be appreciated. Their study uses a modeling approach to make inferences about neural activity timing differences of ≈100 milliseconds. To understand the basis of this surprisingly high temporal resolution, it is important to consider the evolution of fMRI.

Monitoring deep brain stimulation by measuring regional brain oxygen responses in freely moving mice

Canine functional magnetic resonance imaging (fMRI) neurocognitive studies represent an emerging field that is advancing more gradually compared to progress in human fMRI research. Given the potential benefits of canine fMRI for veterinary, comparative, and translational research, this systematic review highlights significant findings, focusing on specific brain areas activated during task-related and resting state conditions in dogs. The review addresses the following question: “What brain areas in dogs are activated in response to various stimuli?”. Following PRISMA 2020 guidelines, a comprehensive search of PUBMED, Scopus, and Web of Knowledge databases identified 1833 studies, of which 46 met the inclusion criteria. The studies were categorized into themes concerning resting state networks and visual, auditory, olfactory, somatosensory, and multi-stimulations studies. In dogs, resting state networks and stimulus-specific functional patterns were confirmed as vital for brain function. These findings reveal both similarities and differences in the neurological mechanisms underlying canine and human cognition, enhance the understanding of neural activation pathways in dogs, expand the knowledge of social bonding patterns, and highlight the potential use of fMRI in predicting the suitability of dogs for assistance roles. Further studies are needed to further map human–canine similarities and identify the unique features of canine brain function. Additionally, implementing innovative human methods, such as combined fMRI–magnetic resonance spectroscopy (MRS), into canine neurocognitive research could significantly advance the field.

Working memory is a crucial cognitive function for processing and storing information in short-term memory during purposeful activities [1]. Numerous studies using EEG, MEG, and stereo-EEG were conducted to identify the neurophysiological correlates of working memory, including oscillations in specific brain regions in the absence of a memorized stimulus. The studies explored multiple aspects such as encoding, maintenance, processing, ordering, updating, and inhibition and various working memory modalities. Additionally, the studies highlighted the significance of examining the functional connectivity between different brain regions. As a result, researchers have amassed a large amount of data that is often contradictory and lacks organization [2]. The aim of this study is to perform a methodical review of literature published from 1980 up to the present period, cataloged in the Scopus, Web of Science, and Pubmed databases. The systematic review follows the PICo structure and addresses three main questions: which neuronal networks are involved in different working memory modalities and detect synchronizations between and within frequencies in cognitively safe subjects; are there disparities in the characteristics of neuronal networks between adults and the elderly; and can various interventions be employed to align the characteristics of neuronal networks in the elderly with those of adults [3]. The systematic review follows PRISMA-P 2015 protocol [4]. Main inclusion criteria focus on investigating working memory, analyzing visual, verbal and nonspecific modalities, using EEG/MEG/stereo-EEG, assessing adult and elderly subjects, and providing quantitative results from behavioral and neurocognitive research. Exclusion criteria: The study excluded emotional stimuli and assessments of long-term memory as well as the use of fMRI. Additionally, unigender studies and studies with subjects who had cognitive or other impairments were not included. In addition, the study required a sufficient number of subjects and time-frequency analysis. Moreover, physical or dietary interventions were excluded, and experimental research was necessary for inclusion. The study did not assess working memory in a foreign language for the subjects. A systematic review was conducted on the platform nested-knowledge.com. Based on the given criteria, a literature search was performed, yielding 2,828 articles meeting the inclusion criteria. These were further screened by two experts, resulting in the identification of 234 relevant articles, and upon full text review, 89 articles were deemed relevant. The resulting pool of articles is characterized by the following parameters: 69 articles describe adult subjects, 5 articles describe elderly subjects, and 12 articles compare both groups. Additionally, 42 articles focus on oscillation, 15 on functional connectivity, and 32 on both metrics. Concerning working memory, 22 articles describe all stages, 8 focus on encoding, 11 on encoding and maintenance, 4 on maintenance and recall, 23 on maintenance, 9 on maintenance and processing, 7 on processing, 1 on recall, and 3 without separating stages. Furthermore, 28 articles pertain to verbal memory, 51 to visual memory, 8 articles contain comparisons of modalities, and 2 articles discuss modally non-specific tasks. Preliminary findings from the systematic review indicate distinct functions of various frequency bands for working memory. Specifically, theta rhythms (4–8 Hz) in the frontal lobe were predominantly associated with information maintenance, while demonstrating a propension for increased synchronization during information processing. The alpha rhythm (8–14 Hz) was associated with inhibiting irrelevant data and protecting the current content of working memory, aligning with the widely accepted paradigm [5]. The beta rhythm (14–28 Hz) was most frequently noted to occur when maintaining and recalling information, and its power was associated with memory accuracy indicators. The gamma rhythm (28 Hz and higher) was seen during the process of encoding and maintaining information, and exhibited greater power for more complex stimuli. The analysis of connectivity revealed that encoding visual and verbal stimuli involves interhemispheric frontal-temporal and frontal-central connections that interact through theta rhythms. Additionally, storing information relies on the interplay of theta and gamma rhythms between the frontal and parietal networks. Notably, when dealing with verbal stimuli, the connectivity of the frontal and temporal brain lobes through theta rhythm enhances with load during storage. The alpha rhythm facilitates communication across posterior and frontal divisions during information storage, whereas beta rhythm is associated with frontal-temporal connections. During visual information storage, theta rhythm mediates communication across frontal-postcentral connections. As storage load increases, theta rhythm leads to strengthening of frontal-parietal and frontal-frontal connections until the threshold of working memory capacity is reached, after which these connections weaken. When processing information, connectivity of the right frontal-occipital network, right prefrontal and left occipital regions, right frontal and occipital-parietal areas for visual memory, and frontal-parietal regions for verbal memory were observed in the theta band. Connectivity of the occipital brain regions primarily occurred in the alpha spectrum, and temporal regions exhibited high frequencies. No specific differences were observed between the elderly and adults, aside from the suppression of low frequencies and the prevalence of high frequencies in the connectivity analysis.

Functional neuroimaging first allowed researchers to describe the functional segregation of regionally activated areas during a variety of experimental tasks. More recently, functional integration studies have described how these functionally specialized areas (i.e. areas whose activity is temporally modified) interact within a highly distributed neural network. When applied to the field of functional magnetic resonance imaging (fMRI), structural equation modeling (SEM) uses theoretical and/or empirical hypotheses to estimate the effects (path coefficients) of an experimental task within a putative network. Structural equation modeling represents a linear technique for multivariate analysis of fMRI data and has been developed to simultaneously examine ratios of multiple causality in an experimental design; the method attempts to explain a covariance structure within an anatomical (constrained) model. This method, when combined with the concept of effective connectivity, can provide information on the strength and direction of the functional interactions which take place between identified nodes of a putative network. After having provided a brief reminder of the principle of the blood oxygen level-dependent (BOLD) contrast effect, the physiological bases of brain activity and the concepts of functional integration and effective connectivity, we specify the various steps in the SEM analysis and the use of fMRI data to explore putative networks of interconnected active areas. Keywords: fMRI, model, network, effective connectivity, SEM