Use Of fMRI Research Articles

Decoding fMRI Signatures of Real-world Autobiographical Memory Retrieval.

Extant neuroimaging data implicate frontoparietal and medial-temporal lobe regions in episodic retrieval, and the specific pattern of activity within and across these regions is diagnostic of an individual's subjective mnemonic experience. For example, in laboratory-based paradigms, memories for recently encoded faces can be accurately decoded from single-trial fMRI patterns [Uncapher, M. R., Boyd-Meredith, J. T., Chow, T. E., Rissman, J., & Wagner, A. D. Goal-directed modulation of neural memory patterns: Implications for fMRI-based memory detection. Journal of Neuroscience, 35, 8531-8545, 2015; Rissman, J., Greely, H. T., & Wagner, A. D. Detecting individual memories through the neural decoding of memory states and past experience. Proceedings of the National Academy of Sciences, U.S.A., 107, 9849-9854, 2010]. Here, we investigated the neural patterns underlying memory for real-world autobiographical events, probed at 1- to 3-week retention intervals as well as whether distinct patterns are associated with different subjective memory states. For 3 weeks, participants (n = 16) wore digital cameras that captured photographs of their daily activities. One week later, they were scanned while making memory judgments about sequences of photos depicting events from their own lives or events captured by the cameras of others. Whole-brain multivoxel pattern analysis achieved near-perfect accuracy at distinguishing correctly recognized events from correctly rejected novel events, and decoding performance did not significantly vary with retention interval. Multivoxel pattern classifiers also differentiated recollection from familiarity and reliably decoded the subjective strength of recollection, of familiarity, or of novelty. Classification-based brain maps revealed dissociable neural signatures of these mnemonic states, with activity patterns in hippocampus, medial PFC, and ventral parietal cortex being particularly diagnostic of recollection. Finally, a classifier trained on previously acquired laboratory-based memory data achieved reliable decoding of autobiographical memory states. We discuss the implications for neuroscientific accounts of episodic retrieval and comment on the potential forensic use of fMRI for probing experiential knowledge.

Functional Magnetic Resonance Imaging: From Acquisition to Application

Functional magnetic resonance imaging (fMRI) is a technique that exploits magnetic resonance imaging (MRI) to detect regional brain activity through measurement of the hemodynamic response that is coupled to electrical neuronal activity. The most common fMRI method detects blood oxygen level dependent (BOLD) contrast. The BOLD effect represents alteration in the ratio of deoxygenated to oxygenated hemoglobin within brain tissue following neuronal activity. Alterations in this hemoglobin ratio result from changes in cerebral oxygen extraction, cerebral blood flow, and cerebral blood volume that occur in response to neuronal activity. The small, but detectable, change in magnetics resonance signal intensity is due to the sensitivity of magnetic resonance (MR) images to the paramagnetic deoxygenated state of hemoglobin that is the basis of contrast in fMRI applications. This review describes the physical and physiological bases of the MR signal, the principle of the BOLD effect, technical issues related to fMRI implementation, and fMRI experimental design. Research and clinical applications of fMRI are presented, including the use of fMRI in neurosurgical planning. Since it provides an individualized map of brain function, fMRI enables accurate localization of eloquent brain regions prior to surgery, allowing assessment of surgical risk and prognosis, as well as planning surgical approach.

Assumptions beyond the science: encouraging cautious conclusions about functional magnetic resonance imaging research on organizational behavior

SummaryFunctional magnetic resonance imaging (fMRI) is likely to become the major tool for studying the neural underpinnings of organizational behavior. It is a technique for brain imaging that, according to advocates, provides information about which areas of the brain are activated during organizational processes (e.g., leadership and decision‐making). In this article, we take a critical look at this tool from a technical perspective. In particular, we take the reader through the assumptions that must be made at the three main steps of the research process (study design, data capture, and interpretation of results) in order to draw conclusions about organizational phenomena from fMRI research. Applying this analysis to three case studies demonstrates the gap between what fMRI can actually tell us and the claims often made about the contribution of fMRI to understanding and improving organizational behavior. Our discussion provides researchers with a series of recommendations oriented toward optimizing the use of fMRI to help it live up to its potential in the field of organizational behavior and consumers with a means of evaluating fMRI research in order to draw appropriate and warranted conclusions. Copyright © 2016 John Wiley & Sons, Ltd.

Study of the neuronal response to olfactory stimuli in control and LPS-stimulated mice by functional magnetic resonance imaging

Olfactory perception plays the key role in the inter­action of animals with biotic factors of the species-specific econiche. Identification of odorants informs nocturnal animals about social environment, presence of predators, or infected food. Olfactory efficiency depends on physiological conditions; in particular, odor sensitivity can be changed by infection. This work considers use of fMRI in the study of the influence of innate immunity activation on neuronal response during perception and differentiation of socially significant (2.5-dimethylpyrazine, 2-heptanon) and socially insignificant (1-hexanol and isoprene) olfactory stimuli by CD-1 mice. We stimulated innate immunity by intraperitoneal injection of bacterial lipopolysaccharide (LPS) at the dose 500 µg/kg three hours before tomography. Urethane anesthesia was used during MRI trail. Odor stimulation was done with a lab-made metering unit for supplying standard doses of volatile organic compounds. The supply of olfactory stimuli induced activation of neurons in the primary perceptual center and the centers of secondary processing of olfactory information. Olfactory stimulus type affected neuronal response rate in an olfactory bulb but did not affect response parameters in other brain regions studied. This increase in neuronal activity is likely to be of adaptive significance as a mechanism supporting olfactory sensitivity increase, which plays the key role in the identification of potential sources of infection.

Conflict monitoring in speech processing: An fMRI study of error detection in speech production and perception

To minimize the number of errors in speech, and thereby facilitate communication, speech is monitored before articulation. It is, however, unclear at which level during speech production monitoring takes place, and what mechanisms are used to detect and correct errors. The present study investigated whether internal verbal monitoring takes place through the speech perception system, as proposed by perception-based theories of speech monitoring, or whether mechanisms independent of perception are applied, as proposed by production-based theories of speech monitoring. With the use of fMRI during a tongue twister task we observed that error detection in internal speech during noise-masked overt speech production and error detection in speech perception both recruit the same neural network, which includes pre-supplementary motor area (pre-SMA), dorsal anterior cingulate cortex (dACC), anterior insula (AI), and inferior frontal gyrus (IFG). Although production and perception recruit similar areas, as proposed by perception-based accounts, we did not find activation in superior temporal areas (which are typically associated with speech perception) during internal speech monitoring in speech production as hypothesized by these accounts. On the contrary, results are highly compatible with a domain general approach to speech monitoring, by which internal speech monitoring takes place through detection of conflict between response options, which is subsequently resolved by a domain general executive center (e.g., the ACC).

NIMG-46THE USE OF CLINICAL FUNCTIONAL MAGNETIC RESONANCE IMAGING IN BRAIN TUMOUR PATIENTS FOR SURGICAL PLANNING: A SINGLE-SURGEON RETROSPECTIVE COHORT STUDY AT A CANADIAN CENTER

BACKGROUND: Advanced imaging techniques such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are being increasingly used for the pre-operative evaluation of patients with brain tumors. METHODS: The study is a retrospective chart review investigating the use of fMRI from 2002-2013 in the pre-operative evaluation of brain tumour patients. Baseline demographic and clinical data were collected. The specific fMRI protocols used for each patient were recorded. RESULTS: 60 patients were identified over the twelve-year period. The type of tumours most commonly investigated were low-grade glioma, glioblastoma multiforme and meningioma. Most common presenting concerns were seizures (46%), change on surveillance (15%), language deficits (11%), and headache (10%). There was a predominance of left-hemispheric lesions investigated with fMRI (77.6% versus 22.4% for right). The most commonly involved lobes were frontal (46.5%), temporal (28.8%), parietal (16.4%), then insular (5.5%). The most common fMRI paradigms were language (85.2%), motor (79.6%), sensory (18.5%), and memory (9.3%). Most patients ultimately underwent a craniotomy (73.2%) while smaller groups underwent stereotactic biopsy (10.7%) and non-surgical management (16.1%). Time from request for fMRI to actual fMRI acquisition was 3.2 +/− 2.3 weeks. Time from fMRI acquisition to intervention was 5.2 +/− 5.4 weeks. CONCLUSIONS: We have characterized patient demographics in a retrospective single-surgeon cohort undergoing pre-operative clinical fMRI at a Canadian center. Our experience suggests an acceptable wait time from scan request to scan completion/analysis and from scan to intervention.

Neural Activity Associated with Visual Search for Line Drawings on AAC Displays: An Exploration of the Use of fMRI

ABSTRACTVisual aided augmentative and alternative communication (AAC) consists of books or technologies that contain visual symbols to supplement spoken language. A common observation concerning some forms of aided AAC is that message preparation can be frustratingly slow. We explored the uses of fMRI to examine the neural correlates of visual search for line drawings on AAC displays in 18 college students under two experimental conditions. Under one condition, the location of the icons remained stable and participants were able to learn the spatial layout of the display. Under the other condition, constant shuffling of the locations of the icons prevented participants from learning the layout, impeding rapid search. Brain activation was contrasted under these conditions. Rapid search in the stable display was associated with greater activation of cortical and subcortical regions associated with memory, motor learning, and dorsal visual pathways compared to the search in the unpredictable display. Rapid search for line drawings on stable AAC displays involves not just the conceptual knowledge of the symbol meaning but also the integration of motor, memory, and visual-spatial knowledge about the display layout. Further research must study individuals who use AAC, as well as the functional effect of interventions that promote knowledge about array layout.

Imaging learned fear circuitry in awake mice using fMRI.

Functional magnetic resonance imaging (fMRI) of learned behaviour in ‘awake rodents’ provides the opportunity for translational preclinical studies into the influence of pharmacological and genetic manipulations on brain function. fMRI has recently been employed to investigate learned behaviour in awake rats. Here, this methodology is translated to mice, so that future fMRI studies may exploit the vast number of genetically modified mouse lines that are available. One group of mice was conditioned to associate a flashing light (conditioned stimulus, CS) with foot shock (PG; paired group), and another group of mice received foot shock and flashing light explicitly unpaired (UG; unpaired group). The blood oxygen level‐dependent signal (proxy for neuronal activation) in response to the CS was measured 24 h later in awake mice from the PG and UG using fMRI. The amygdala, implicated in fear processing, was activated to a greater degree in the PG than in the UG in response to the CS. Additionally, the nucleus accumbens was activated in the UG in response to the CS. Because the CS signalled an absence of foot shock in the UG, it is possible that this region is involved in processing the safety aspect of the CS. To conclude, the first use of fMRI to visualise brain activation in awake mice that are completing a learned emotional task is reported. This work paves the way for future preclinical fMRI studies to investigate genetic and environmental influences on brain function in transgenic mouse models of disease and aging.

Researchers Hone Use of fMRI to Predict Memory Loss After Epilepsy Surgery

Researchers Hone Use of fMRI to Predict Memory Loss After Epilepsy Surgery

A prospective fMRI-based technique for localising the epileptogenic zone in presurgical evaluation of epilepsy

There is growing evidence for the benefits of simultaneous EEG-fMRI as a non-invasive localising tool in the presurgical evaluation of epilepsy. However, many EEG-fMRI studies fail due to the absence of interictal epileptic discharges (IEDs) on EEG. Here we present an algorithm which makes use of fMRI as sole modality to localise the epileptogenic zone (EZ). Recent studies using various model-based or data-driven fMRI analysis techniques showed that it is feasible to find activation maps which are helpful in the detection of the EZ. However, there is lack of evidence that these techniques can be used prospectively, due to (a) their low specificity, (b) selecting multiple activation maps, or (c) a widespread epileptic network indicated by the selected maps. In the current study we present a method based on independent component analysis and a cascade of classifiers that exclusively detects a single map related to interictal epileptic brain activity. In order to establish the sensitivity and specificity of the proposed method, it was evaluated on a group of 18 EEG-negative patients with a single well-defined EZ and 13 healthy controls. The results show that our method provides maps which correctly indicate the EZ in several (N=4) EEG-negative cases but at the same time maintaining a high specificity (92%). We conclude that our fMRI-based approach can be used in a prospective manner, and can extend the applicability of fMRI to EEG-negative cases.

BCI in patients with disorders of consciousness: Clinical perspectives

The reestablishment of communication is one of the main goals for patients with disorders of consciousness (DOC). It is now established that many DOC patients retain the ability to process stimuli of varying complexity even in the absence of behavioural response. Motor impairment, fatigue, attention disorders might contribute to the difficulty of communication in this population. Brain-computer interfaces (BCI) might be helpful in restoring some communication ability in these patients. After a definition of the different disorders of consciousness that might benefit from BCI, brain markers able to detect cognitive processes and awareness in the absence of behavioural manifestation are described. Can these markers be willfully modulated and used to restore communication in DOC patients? In order to answer this question, three paradigmatic articles using either functional imaging or electrophysiology are critically analysed with regard to clinical applications. It appears that the use of fMRI is limited from a clinical point of view, whereas the EEG seems more feasible with possible BCI applications at the patient's bedside. However, at this stage, several limitations are pointed out: the lack of awareness in itself, the lack of sensitivity of the technique, atypical pattern of brain activity in brain damaged patients. The challenge is now to select the best candidates, to improve the efficiency, portability and cost of these techniques. Although this innovative technology may concern a minority of DOC patients, it might offer the possibility to restore or improve communication to heavily disabled patients and meanwhile detect a signature of awareness.

Assessing Nociception by fMRI of the Human Spinal Cord: A Systematic Review.

OBJECTIVETo assess the use of fMRI of the spinal cord in measuring noxious stimulation.METHODSThe Scopus, Medline, EMBASE, and Web of Science databases were searched, along with the reference lists of included articles. Two independent reviewers screened abstracts, full-text articles, and extracted data. Original research was included if fMRI of the human spinal cord was used to measure responses to noxious stimulation.RESULTSOf the 192 abstracts screened, 19 met the search criteria and were divided according to their focus: investigating pain responses (n = 6), methodology (n = 6), spinal cord injury (n = 2), or cognition–pain interactions (n = 5). All but one study appear to have observed activity in ipsilateral and dorsal gray matter regions in response to noxious stimuli, although contralateral or ventral activity was also widely observed.CONCLUSIONSAlthough nociception can be investigated using spinal fMRI, establishing reliability, standardizing methodology, and reporting of results will greatly advance this field.

The economics of functional magnetic resonance imaging: clinical and research.

It is difficult to justify maintaining a clinical functional magnetic resonance imaging (fMRI) program based solely on revenue generation. The use of fMRI is, therefore, based mostly in patient care considerations, leading to better outcomes. The high costs of the top-of-the-line equipment, hardware, and software needed for state-of-the-art fMRI and the time commitment by multiple professionals are not adequately reimbursed at a representative rate by current payor schemes for the Current Procedure Terminology codes assigned.

Impact of Preoperative Functional Magnetic Resonance Imaging during Awake Craniotomy Procedures for Intraoperative Guidance and Complication Avoidance

Background: We wanted to study the role of functional MRI (fMRI) in preventing neurological injury in awake craniotomy patients as this has not been previously studied. Objectives: To examine the role of fMRI as an intraoperative adjunct during awake craniotomy procedures. Methods: Preoperative fMRI was carried out routinely in 214 patients undergoing awake craniotomy with direct cortical stimulation (DCS). Results: In 40% of our cases (n = 85) fMRI was utilized for the intraoperative localization of the eloquent cortex. In the other 129 cases significant noise distortion, poor task performance and nonspecific BOLD activation precluded the surgeon from using the fMRI data. Compared with DCS, fMRI had a sensitivity and specificity, respectively, of 91 and 64% in Broca's area, 93 and 18% in Wernicke's area and 100 and 100% in motor areas. A new intraoperative neurological deficit during subcortical dissection was predictive of a worsened deficit following surgery (p < 0.001). The use of fMRI for intraoperative localization was, however, not significant in preventing worsened neurological deficits, both in the immediate postoperative period (p = 1.00) and at the 3-month follow-up (p = 0.42). Conclusions: The routine use of fMRI was not useful in identifying language sites as performed and, more importantly, practiced tasks failed to prevent neurological deficits following awake craniotomy procedures.

Functional magnetic resonance imaging as experienced by stroke survivors.

Functional magnetic resonance imaging (fMRI), a noninvasive technique that measures brain activation, has been increasingly used in the past decade, particularly among older adults. Use of fMRI in research with stroke survivors in recent years has substantially contributed to researchers' understanding of the pathophysiology of stroke sequelae. However, despite the increasing popularity and use of fMRI, little is known about the patient experience of fMRI under research circumstances. The current research brief reports the findings of a pilot study undertaken to understand stroke survivors' experiences with fMRI under research circumstances. Nine ischemic stroke patients underwent two MRI sessions, each of which lasted 1.5 hours and included several fMRI tasks. Patients were asked about their experiences and to share any advice. All participants reported that they did not feel claustrophobic; in addition, the importance of educating participants about fMRI was a universal theme that emerged. Knowledge of participant experiences may help with enrollment strategies for fMRI studies and improve research outcomes related to the fMRI experience.

Deficient approaches to human neuroimaging.

Functional magnetic resonance imaging (fMRI) is the workhorse of imaging-based human cognitive neuroscience. The use of fMRI is ever-increasing; within the last 4 years more fMRI studies have been published than in the previous 17 years. This large body of research has mainly focused on the functional localization of condition- or stimulus-dependent changes in the blood-oxygenation-level dependent signal. In recent years, however, many aspects of the commonly practiced analysis frameworks and methodologies have been critically reassessed. Here we summarize these critiques, providing an overview of the major conceptual and practical deficiencies in widely used brain-mapping approaches, and exemplify some of these issues by the use of imaging data and simulations. In particular, we discuss the inherent pitfalls and shortcomings of methodologies for statistical parametric mapping. Our critique emphasizes recent reports of excessively high numbers of both false positive and false negative findings in fMRI brain mapping. We outline our view regarding the broader scientific implications of these methodological considerations and briefly discuss possible solutions.

Pre-surgical cortical activation to food pictures is associated with weight loss following bariatric surgery

BackgroundRecent research suggests that preintervention functional magnetic resonance imaging (fMRI) data may predict weight loss outcomes among patients who participate in a behavioral weight loss plan. No study has examined whether presurgical brain activation can predict outcomes following bariatric surgery. MethodThe aim of the present study was to determine if brain activations during a presurgical fMRI food-motivation paradigm are associated with weight loss 3 and 6 months following laparoscopic adjustable gastric banding (LAGB). Nineteen participants viewed food and nonfood pictures from a well-established food motivation paradigm during an fMRI scanning session before LAGB surgery. Weight was assessed presurgery and 3 and 6 months postsurgery; data for all participants was available at each time point. fMRI data were analyzed using the BrainVoyager QX statistical package. Whole brain voxelwise correlations of presurgery (food–nonfood) brain activation and weight, corrected for multiple comparisons, were performed to analyze the relationship between presurgical brain activation and subsequent weight loss. The settings were a medical university brain imaging center and 2 surgical weight loss centers in a major metropolitan area. ResultsIncreased activity in frontal regions associated with cognitive control (medial, middle, superior frontal gyrus) and posterior cingulate cortex was associated with weight loss following LAGB. ConclusionWe found that neural activity in previously established regions associated with cognitive and behavioral self-regulation predicts weight loss following bariatric surgery. These preliminary findings highlight the role of neural circuitry in the success and maintenance of weight loss and suggest a possible future use of fMRI in screening LAGB surgery candidates.

The use of fMRI to detect neural responses to cognitive interference and planning: evidence for a contribution of task related changes in heart rate?

fMRI signals during rest are strongly correlated with heart rate variations. These heart rate/fMRI associations may influence the results of brain activation studies, particularly if heart rate is affected by the task. To assess the contribution of task-related heart rate changes on fMRI brain activation related to executive processing, we co-registered the electrocardiogram with fMRI in 91 subjects during an interference task (color-word Stroop) and during a planning task (Tower of London; ToL). We found that both Stroop interference and ToL planning significantly increased heart rate in the scanner and confirmed significant main effects of heart rate regressors on the fMRI signals. Nevertheless, statistical contrasts that test for increased fMRI during Stroop interference and ToL planning were not significantly influenced by inclusion of heart rate regressors. We conclude therefore that fMRI changes associated with heart rate changes do not impact strongly on higher-order fMRI effects in these commonly used executive function tasks, but routinely adding a correction seems prudent.

An fMRI study exploring cognitive processing during computer-based discovery learning

Discovery-based learning designs incorporating active exploration are common within computer-based instructional simulations, supported by constructivist theories of learning focussing on active individual knowledge construction. On the other hand, researchers have highlighted empirical evidence showing that ‘pure' discovery learning is of limited value and that combinations of explicit instruction and guided discovery learning are more effective. Little is known, however, about differences in the cognitive processing that occurs when a learner undertakes active discovery learning using a computer-based simulation compared to when they are guided through observation of simulation output. A better understanding of the cognitive processing occurring when learners interact with on-line materials in the context of specific learning designs is important both for networked learning researchers and for on-line teachers. This paper reports on a study in which the brain activations from two learning conditions using computer-based simulations were compared using functional magnetic resonance imaging (fMRI). One condition allowed exploration through manipulation of simulation parameters, while the other allowed observation of simulation output from preset parameters. Drawing on constructivist theories of learning, it was hypothesised that the active exploration condition would lead to greater activation of brain areas associated with working memory organisation and long term memory formation. The study also set out to explore the broader feasibility of using fMRI to explore learners' cognitive processing while undertaking holistic learning activities using on-line learning materials. Results of the study were somewhat equivocal about differences in brain activation with no consistent differences in activation between the two conditions able to be measured. Consistent with our related research which suggests that discovery learning strategies vary substantially across individuals, results of this study suggest that the cognitive processing during the two conditions varied across participants. Integrated analysis of the exploration processes, learning outcomes and measured brain activations of individuals shows promise in better understanding the relationship between learning strategy, interaction and cognition when using instructional simulations. Approaches like this that draw on an analysis of data on learning process and outcome along with an analysis of physiological measures (in this case blood flow as an indicator of brain activation) are expected to be at the leading edge of learning analytics research in coming years. The study also highlighted challenges associated with the use of fMRI to explore learners' cognition while undertaking learning activities allowing significant learner control and involving extensive computer-based interaction.

HIV infection and the fronto–striatal system

Functional MRI studies investigating the impact of HIV on the brain have implicated the involvement of fronto-striatal circuitry. However, to date there is no review and meta-analysis of this work. We systematically reviewed the literature and performed a meta-analysis of functional magnetic resonance imaging (fMRI) studies in HIV-infected individuals using a well validated tool recently developed for use in fMRI, 'GingerALE'. Twenty-one studies (468 HIV+, 270 HIV- controls) were qualitatively reviewed, of which six (105 HIV+, 102 controls) utilized fMRI paradigms engaging the fronto-striatal-parietal network, making a quantitative analysis possible. Our meta-analysis revealed consistent functional differences in the left inferior frontal gyrus and caudate nucleus between infected participants and controls across these studies. This fronto-striatal dysfunction was qualitatively related to cognitive impairment, disease progression and treatment effects. Although further work needs to be done to further delineate the potentially confounding influence of substance abuse and HIV-related comorbidities, as well as HIV's effect on functional haemodynamic vascular coupling, these findings indicate that further investigation of the fronto-striatal sub-networks in HIV-infected patients is warranted.