Meta-analysis Of fMRI Studies Research Articles

Negative priming: a meta-analysis of fMRI studies.

A phenomenon termed negative priming is defined as an increase in reaction time and/or decrease in performance during instances in which current target stimuli are employed as distractor stimuli in the previous trial. A recent qualitative review on negative priming reported neural regions of interest underlined by activity within the right middle frontal gyrus and left middle temporal gyrus; however, these areas of interest have not been tested and supported by using coordinate-based, quantitative meta-analysis. We compiled functional magnetic resonance imaging studies that examined neural correlates of priming tasks using perceptual, conceptual and lexical primes. Effect-size signed differential mapping was used to perform a neuroimaging meta-analysis on the negative priming effect. Results from fourteen studies (245 participants; 85 foci) show concordance across studies in the right middle frontal gyrus and the left superior temporal gyrus, as suggested by the previous review; however, results also yielded concordance within the anterior cingulate cortex. Our data support the extant hypothesis and offer new insights into the neural mechanisms of the negative priming effect.

Brain areas associated with numbers and calculations in children: Meta-analyses of fMRI studies

Children use numbers every day and typically receive formal mathematical training from an early age, as it is a main subject in school curricula. Despite an increase in children neuroimaging studies, a comprehensive neuropsychological model of mathematical functions in children is lacking. Using quantitative meta-analyses of functional magnetic resonance imaging (fMRI) studies, we identify concordant brain areas across articles that adhere to a set of selection criteria (e.g., whole-brain analysis, coordinate reports) and report brain activity to tasks that involve processing symbolic and non-symbolic numbers with and without formal mathematical operations, which we called respectively number tasks and calculation tasks. We present data on children 14 years and younger, who solved these tasks. Results show activity in parietal (e.g., inferior parietal lobule and precuneus) and frontal (e.g., superior and medial frontal gyri) cortices, core areas related to mental-arithmetic, as well as brain regions such as the insula and claustrum, which are not typically discussed as part of mathematical problem solving models. We propose a topographical atlas of mathematical processes in children, discuss findings within a developmental constructivist theoretical model, and suggest practical methodological considerations for future studies.

Detecting social-cognitive deficits after traumatic brain injury: An ALE meta-analysis of fMRI studies

ABSTRACTPurpose: Traumatic brain injury (TBI) can result in significant social dysfunction, which is represented by impairment to social-cognitive abilities (i.e. social cognition, social attention/executive function and communication). This study is aimed to explore brain networks mediating the social dysfunction after TBI and its underlying mechanisms. Methods: We performed a quantitative meta-analysis using the activation likelihood estimation (ALE) approach on functional magnetic resonance imaging (fMRI) studies of social-cognitive abilities following TBI. Sixteen studies fulfilled the inclusion criteria resulting in a total of 190 patients with TBI and 206 controls enrolled in the ALE meta-analysis. Results: The temporoparietal junction (TPJ) and the medial prefrontal cortex (mPFC) were the specific regions that social cognition predominantly engaged. The cingulate gyrus, frontal gyrus and inferior parietal lobule were the main regions related to social attention/executive functions. Communication dysfunction, especially related to language deficits, was found to show greater activation of the temporal gyrus and fusiform gyrus in TBI. Conclusion: The current ALE meta-analytic findings provide evidence that patients have significant social-cognitive disabilities following TBI. The relatively limited pool of literature and the varied fMRI results from published studies indicate that social-cognitive abilities following TBI is an area that would greatly benefit from further investigation.

Rethinking the function of brain regions for reading Chinese characters in a meta-analysis of fMRI studies

Abstract Neuroimaging studies have proposed specific brain regions for reading Chinese characters. For example, compared to alphabetic languages, Chinese reading has revealed more activation of the left Middle Frontal Gyrus (MFG) and null or deactivation at left posterior Superior Temporal Gyrus (pSTG). However, the model of specific regions for Chinese was contested by recent findings showing similar activities across languages under the same task demand. Thus, whether the engagement of the Chinese-specific regions was due to stimulus selectivity or to task demand was called into question. The current meta-analysis, using Activation Likelihood Estimation (ALE), summarized brain regions in previous fMRI studies from two types of contrast, stimulus contrasts (SC), in which more regions were activated for Chinese characters than for other visual stimuli (e.g., Korean words, faces) or for other types of characters (e.g., real > artificial characters), and task contrasts (TC), in which more regions were activated for one task than for another (e.g., lexical decision > symbol detection) in processing Chinese characters. ALE activation maps revealed a shared network for the two types of contrast, including the right Inferior Frontal Gyrus (IFG, BA47) and four clusters in the left hemisphere, the IFG (BA45/46), Superior Parietal Lobule, Superior Frontal Gyrus, and posterior Middle Temporal Gyrus (pMTG). The SC > TC comparison demonstrated the greater involvement of the left Angular Gyrus and left Fusiform Gyrus. The TC > SC comparison, in contrast, revealed the engagement of left-hemisphere regions in the IFG, MFG, pSTG, pMTG, and Medial Frontal Gyrus. These results suggest that the previously identified Chinese-specific areas (e.g., MFG, pSTG) might be task dependent rather than stimulus selective. This work shed light on the language-general neural network of visual word reading.

The Role of the Amygdala in Facial Trustworthiness Processing: A Systematic Review and Meta-Analyses of fMRI Studies.

BackgroundFaces play a key role in signaling social cues such as signals of trustworthiness. Although several studies identify the amygdala as a core brain region in social cognition, quantitative approaches evaluating its role are scarce.ObjectivesThis review aimed to assess the role of the amygdala in the processing of facial trustworthiness, by analyzing its amplitude BOLD response polarity to untrustworthy versus trustworthy facial signals under fMRI tasks through a Meta-analysis of effect sizes (MA). Activation Likelihood Estimation (ALE) analyses were also conducted.Data sourcesArticles were retrieved from MEDLINE, ScienceDirect and Web-of-Science in January 2016. Following the PRISMA statement guidelines, a systematic review of original research articles in English language using the search string “(face OR facial) AND (trustworthiness OR trustworthy OR untrustworthy OR trustee) AND fMRI” was conducted.Study selection and data extractionThe MA concerned amygdala responses to facial trustworthiness for the contrast Untrustworthy vs. trustworthy faces, and included whole-brain and ROI studies. To prevent potential bias, results were considered even when at the single study level they did not survive correction for multiple comparisons or provided non-significant results. ALE considered whole-brain studies, using the same methodology to prevent bias. A summary of the methodological options (design and analysis) described in the articles was finally used to get further insight into the characteristics of the studies and to perform a subgroup analysis. Data were extracted by two authors and checked independently.Data synthesisTwenty fMRI studies were considered for systematic review. An MA of effect sizes with 11 articles (12 studies) showed high heterogeneity between studies [Q(11) = 265.68, p < .0001; I2 = 95.86%, 94.20% to 97.05%, with 95% confidence interval, CI]. Random effects analysis [RE(183) = 0.851, .422 to .969, 95% CI] supported the evidence that the (right) amygdala responds preferentially to untrustworthy faces. Moreover, two ALE analyses performed with 6 articles (7 studies) identified the amygdala, insula and medial dorsal nuclei of thalamus as structures with negative correlation with trustworthiness. Six articles/studies showed that posterior cingulate and medial frontal gyrus present positive correlations with increasing facial trustworthiness levels. Significant effects considering subgroup analysis based on methodological criteria were found for experiments using spatial smoothing, categorization of trustworthiness in 2 or 3 categories and paradigms which involve both explicit and implicit tasks.LimitationsSignificant heterogeneity between studies was found in MA, which might have arisen from inclusion of studies with smaller sample sizes and differences in methodological options. Studies using ROI analysis / small volume correction methods were more often devoted specifically to the amygdala region, with some results reporting uncorrected p-values based on mainly clinical a priori evidence of amygdala involvement in these processes. Nevertheless, we did not find significant evidence for publication bias.Conclusions and implications of key findingsOur results support the role of amygdala in facial trustworthiness judgment, emphasizing its predominant role during processing of negative social signals in (untrustworthy) faces. This systematic review suggests that little consistency exists among studies’ methodology, and that larger sample sizes should be preferred.

Cognitive Reserve in Healthy Aging and Alzheimer's Disease: A Meta-Analysis of fMRI Studies.

Cognitive reserve (CR) has been defined as the ability to optimize or maximize performance through differential recruitment of brain networks. In the present study, we aimed at providing evidence for a consistent brain network underpinning CR in healthy and pathological aging. To pursue this aim, we performed a coordinate-based meta-analysis of 17 functional magnetic resonance imaging studies on CR proxies in healthy aging, Alzheimer's disease (AD), and mild cognitive impairment (MCI). We found that different brain areas were associated with CR proxies in healthy and pathological aging. A wide network of areas, including medial and lateral frontal areas, that is, anterior cingulate cortex and dorsolateral prefrontal cortex, as well as precuneus, was associated with proxies of CR in healthy elderly patients. The CR proxies in patients with AD and amnesic-MCI were associated with activation in the anterior cingulate cortex. These results were discussed hypothesizing the existence of possible compensatory mechanisms in healthy and pathological aging.

Is There a Common Network for Processing Reward and Aversion in the Brain?

How do our brains process and attach positive and negative value to the objects around us, the sensations we feel, and the experiences that we have? One method of examining these questions is to detect, using functional magnetic resonance imaging (fMRI), which areas of the human brain are activated when subjects are exposed to rewarding and aversive stimuli. Although many fMRI studies have concentrated on identifying a network of areas that become active in processing either reward or aversion, there is evidence of significant overlap between the “reward” and “aversion” networks, suggesting that the brain might process rewarding and aversive stimuli in a similar manner regardless of valence. Thus, a meta-analysis of fMRI studies involving rewarding and aversive stimuli was undertaken to determine the areas of the brain that are commonly and differentially activated by reward and aversion. The preliminary results indicate that regions of the prefrontal cortex, anterior cingulate cortex, amygdala, nucleus accumbens, hippocampus, and basal ganglia were commonly activated by rewarding and aversive stimuli, while areas including the insula, midcingulate cortex, and parts of the hippocampus were differentially activated. Locating such commonalities and differences might help in our understanding of how the brain ascribes value to our environment.&#x0D;

The Core Neural Mechanisms underlying Depression Disorder: A Meta-analysis of fMRI Studies

Depression disorder is a mental disorder characterized by a pervasive and persistent low mood, and is accompanied by low self-esteem and by a loss of interest or pleasure in normally enjoyable activities. Biological, psychological, and social factors all play a role in inducing depression. In the last decades, the rapid growth of literatures on neuroimaging psychiatry has led to major advances in our understanding of affective disorder such as depression. However, it has also made it increasingly difficult to aggregate and synthesize neuroimaging findings to reach a conclusive agreement. We try to locate the core nerural mechanisms that are specific to depression disorder based on extant literature, by employing a newly developed automated brain-mapping framework—Neurosynth that uses text-mining, meta-analysis and machine-learning techniques to decode broad cognitive states from brain activity (i.e., reverse interference). The processing stream involves the following six steps: Activation coordinates are extracted from published neuroimaging articles using an automated parser. The full text of all articles is parsed, and each article is “tagged” with a set of terms that occur at a high frequency in that article. A list of several thousand terms that occur at high frequency in 20 or more studies are generated. For each term of interest (e.g., “depression”), the entire database of coordinates is divided into two sets: those that occur in articles containing the term and those that do not. A giant meta-analysis is performed comparing the coordinates reported for studies with and without the term of interest. In addition to producing statistical inference maps (i.e., z and p value maps), we also compute posterior probability maps, which display the likelihood of a given term being used in a study if activation is observed at a particular voxel. We repeat the series of steps for depression, anxiety as well as major depression. In sum, the meta-analysis suggests that amygdala, VMPFC and DLPFC are the core nerural mechanisms underlying depression disorder. Among them, differential anlysis indicates that the dysfunction of amygdala and VMPFC is also the key brain regions for other affective disorder such as anxiety, but the malfunction of DLPFC is most predictive and specific to depression disorder. The inability to down-regulate emotion reactions may be the key neural mechanism for this particular disorder. Thus, our study provides clues for future research on neural basis underlying depression disorder, with a special emphasis on DLPFC.

Neural bases of atypical emotional face processing in autism: A meta-analysis of fMRI studies

Objectives. We aim to outline the neural correlates of atypical emotional face processing in individuals with ASD. Methods. A comprehensive literature search was conducted through electronic databases to identify functional magnetic resonance imaging (fMRI) studies of whole brain analysis with emotional-face processing tasks in individuals with ASD. The Signed Differential Mapping with random effects model was used to conduct meta-analyses. Identified fMRI studies were further divided into sub-groups based on contrast (“emotional-face vs. non-emotional-face” or “emotional-face vs. non-face”) to confirm the results of a meta-analysis of the whole studies. Results. Thirteen studies with 226 individuals with ASD and 251 typically developing people were identified. We found ASD-related hyperactivation in subcortical structures, including bilateral thalamus, bilateral caudate, and right precuneus, and ASD-related hypoactivation in the hypothalamus during emotional-face processing. Sub-analyses with more homogeneous contrasts preserved the findings of the main analysis such as hyperactivation in sub-cortical structure. Jackknife analyses showed that hyperactivation of the left caudate was the most robust finding. Conclusions. Abnormalities in the subcortical structures, such as amygdala, hypothalamus and basal ganglia, are associated with atypical emotional-face processing in individuals with ASD.

A meta-analysis of fMRI studies in healthy relatives of patients with schizophrenia.

Genetically at-risk yet healthy relatives of patients with schizophrenia, sharing an important part of the genetic susceptibility to the disease, allow the study of neuroimaging endophenotypes. The aim of our study was to perform a meta-analysis of whole-brain functional magnetic resonance imaging (fMRI) studies that compared adult healthy relatives of patients with schizophrenia and controls. Twenty-one whole-brain fMRI studies were included (17 using cognitive tasks and four using emotional tasks), published between 2003 and 2013. These studies included 467 healthy relatives of patients with schizophrenia and 768 controls. To conduct the statistical analysis, we used the effect-size signed differential mapping software, a voxel-based meta-analytic approach. In healthy relatives of patients with schizophrenia, we observed a general pattern of overactivation across the 21 fMRI studies in right-sided frontal, parietal and temporal regions compared to controls. This pattern was accompanied by an underactivation in the cingulate gyrus. Our analyses showed a very similar pattern during purely cognitive tasks; during emotional tasks, healthy relatives additionally overactivated the left parahippocampal gyrus. This fMRI pattern of prefrontal overactivation and hypoactivation of the cingulate gyrus may represent a candidate endophenotype for schizophrenia.

The Neural Mechanism underlying Music Perception: A Meta-analysis of fMRI Studies

Music is part of the human nature. Music perception involves a series of hierarchical processing levels, including auditory feature extraction, gestalt formation, interval analysis, and structure analysis. Previous functional magnetic resonance imaging (fMRI) studies have identified multiple cortical regions involved in different levels of music perception, but these studies yielded inconsistent findings possibly because different research paradigms and data analysis methods were used. Therefore, the neural mechanism underlying music perception is unclear. In this study we performed a meta-analysis to identify brain regions stably recruited by music perception. Specially, we focused on two processing levels specific to music perception, which were interval analysis and structure analysis. In addition, to explore the hierarchical structure of music perception, we examined the possible overlapping and dissociation of the regions involved in interval analysis and structure analysis. We used meta-analysis approach to re-analyze results from fMRI studies on interval analysis and structure analysis. There were eight studies on interval analysis which included 15 contrasts and 63 peaks, and ten studies on structure analysis which included 19 contrasts and 217 peaks. The coordinates of peak voxels reported in these studies were projected onto a brain template to visualize the distributions of activations recruited by interval analysis and structure analysis respectively. To identify brain regions stably activated by music perception, peaks of each analysis level were segregated into a number of spatially distinct clusters, using a hierarchical classification algorithm that minimized the spatial extent within each cluster while maximizing the peak-to-peak distance between clusters. Then, we calculated mean coordinates for each cluster in the MNI space and used FSL View procedure to identify the anatomical label of each cluster. Finally, to explore whether clusters belonging to the two analysis levels were spatially overlapped or dissociated, we examined the pairs of clusters with distances less than 7mm (about 3 voxels) by K-means clustering. The meta-analysis identified 12 clusters for interval analysis and 29 clusters for structure analysis. Clusters for interval analysis primarily localized in the superior temporal gyrus (STG) with the peaks distribution rate (PDR)being 43%, while clusters for structure analysis mainly localized in the prefrontal cortex with a PDR of 34%. Although both interval analysis and structure analysis involved frontal, temporal, parietal and insular areas, their activations overlapped only in the posterior portion of the superior temporal gyrus (STGp). In sum, the meta-analysis suggests that interval analysis and structure analysis are two separate processing levels in the hierarchical structure of music perception, with largely dissociated neural activations. In addition, the two analysis levels intersected only in STGp, which might play a role in information exchanges between interval analysis and structure analysis. Thus, our study provides clues for future researches on neural basis underlying hierarchical structure of music perception.

Stimulus-dependent activations and attention-related modulations in the auditory cortex: A meta-analysis of fMRI studies

We meta-analyzed 115 functional magnetic resonance imaging (fMRI) studies reporting auditory-cortex (AC) coordinates for activations related to active and passive processing of pitch and spatial location of non-speech sounds, as well as to the active and passive speech and voice processing. We aimed at revealing any systematic differences between AC surface locations of these activations by statistically analyzing the activation loci using the open-source Matlab toolbox VAMCA (Visualization and Meta-analysis on Cortical Anatomy). AC activations associated with pitch processing (e.g., active or passive listening to tones with a varying vs. fixed pitch) had median loci in the middle superior temporal gyrus (STG), lateral to Heschl's gyrus. However, median loci of activations due to the processing of infrequent pitch changes in a tone stream were centered in the STG or planum temporale (PT), significantly posterior to the median loci for other types of pitch processing. Median loci of attention-related modulations due to focused attention to pitch (e.g., attending selectively to low or high tones delivered in concurrent sequences) were, in turn, centered in the STG or superior temporal sulcus (STS), posterior to median loci for passive pitch processing. Activations due to spatial processing were centered in the posterior STG or PT, significantly posterior to pitch processing loci (processing of infrequent pitch changes excluded). In the right-hemisphere AC, the median locus of spatial attention-related modulations was in the STS, significantly inferior to the median locus for passive spatial processing. Activations associated with speech processing and those associated with voice processing had indistinguishable median loci at the border of mid-STG and mid-STS. Median loci of attention-related modulations due to attention to speech were in the same mid-STG/STS region. Thus, while attention to the pitch or location of non-speech sounds seems to recruit AC areas less involved in passive pitch or location processing, focused attention to speech predominantly enhances activations in regions that already respond to human vocalizations during passive listening. This suggests that distinct attention mechanisms might be engaged by attention to speech and attention to more elemental auditory features such as tone pitch or location.This article is part of a Special Issue entitled <Human Auditory Neuroimaging>.

Identifying a consistent pattern of neural function in attention deficit hyperactivity disorder: a meta-analysis

The neurobiological underpinnings of attention deficit hyperactivity disorder (ADHD) are inconclusive. Activation abnormalities across brain regions in ADHD compared with healthy controls highlighted in task-based functional magnetic resonance imaging (fMRI) studies are heterogeneous. To identify a consistent pattern of neural dysfunction in ADHD, a meta-analysis of fMRI studies using Go/no-go, Stop and N-back tasks was undertaken. Several databases were searched using the key words: 'ADHD and fMRI' and 'ADHD and fMRI task'. In all, 20 studies met inclusion criteria comprising 334 patients with ADHD and 372 healthy controls and were split into N-back, Stop task and Go/no-go case-control groups. Using Signed Differential Mapping each batch was meta-analysed individually and meta-regression analyses were used to examine the effects of exposure to methylphenidate (MPH), length of MPH wash-out period, ADHD subtype, age and intelligence quotient (IQ) differences upon neural dysfunction in ADHD. Across all tasks less activity in frontal lobe regions compared with controls was detected. Less exposure to treatment and lengthier wash-out times resulted in less left medial frontal cortex activation in N-back and Go/no-go studies. Higher percentage of combined-type ADHD resulted in less superior and inferior frontal gyrus activation. Different IQ scores between groups were linked to reduced right caudate activity in ADHD. Consistent frontal deficits imply homogeneous cognitive strategies involved in ADHD behavioural control. Our findings suggest a link between fMRI results and the potentially normalizing effect of treatment and signify a need for segregated examination and contrast of differences in sample characteristics in future studies.

Increased Prefrontal and Parahippocampal Activation with Reduced Dorsolateral Prefrontal and Insular Cortex Activation to Food Images in Obesity: A Meta-Analysis of fMRI Studies

Background and ObjectivesObesity is emerging as the most significant health concern of the twenty-first century. A wealth of neuroimaging data suggest that weight gain might be related to aberrant brain function, particularly in prefrontal cortical regions modulating mesolimbic addictive responses to food. Nevertheless, food addiction is currently a model hotly debated. Here, we conduct a meta-analysis of neuroimaging data, examining the most common functional differences between normal-weight and obese participants in response to food stimuli.Data SourceWe conducted a search using several journal databases and adhered to the ‘Preferred Reporting Items for Systematic Reviews and Meta-analyses’ (PRISMA) method. To this aim, 10 studies were found with a total of 126 obese participants, 129 healthy controls, equaling 184 foci (146 increased, 38 decreased activation) using the Activation Likelihood Estimation (ALE) technique. Out of the 10 studies, 7 investigated neural responses to food versus non-food images.ResultsIn response to food images, obese in comparison to healthy weight subjects had increased activation in the left dorsomedial prefrontal cortex, right parahippocampal gyrus, right precentral gyrus and right anterior cingulate cortex, and reduced activation in the left dorsolateral prefrontal cortex and left insular cortex.ConclusionsPrefrontal cortex areas linked to cognitive evaluation processes, such as evaluation of rewarding stimuli, as well as explicit memory regions, appear most consistently activated in response to images of food in those who are obese. Conversely, a reduced activation in brain regions associated with cognitive control and interoceptive awareness of sensations in the body might indicate a weakened control system, combined with hypo-sensitivity to satiety and discomfort signals after eating in those who are prone to overeat.

A meta-analysis of fMRI studies on Chinese orthographic, phonological, and semantic processing

A growing body of neuroimaging evidence has shown that Chinese character processing recruits differential activation from alphabetic languages due to its unique linguistic features. As more investigations on Chinese character processing have recently become available, we applied a meta-analytic approach to summarize previous findings and examined the neural networks for orthographic, phonological, and semantic processing of Chinese characters independently. The activation likelihood estimation (ALE) method was used to analyze eight studies in the orthographic task category, eleven in the phonological and fifteen in the semantic task categories. Converging activation among three language-processing components was found in the left middle frontal gyrus, the left superior parietal lobule and the left mid-fusiform gyrus, suggesting a common sub-network underlying the character recognition process regardless of the task nature. With increasing task demands, the left inferior parietal lobule and the right superior temporal gyrus were specialized for phonological processing, while the left middle temporal gyrus was involved in semantic processing. Functional dissociation was identified in the left inferior frontal gyrus, with the posterior dorsal part for phonological processing and the anterior ventral part for semantic processing. Moreover, bilateral involvement of the ventral occipito-temporal regions was found for both phonological and semantic processing. The results provide better understanding of the neural networks underlying Chinese orthographic, phonological, and semantic processing, and consolidate the findings of additional recruitment of the left middle frontal gyrus and the right fusiform gyrus for Chinese character processing as compared with the universal language network that has been based on alphabetic languages.

Poster #24 FAILURE TO DEACTIVATE MEDIAL PREFRONTAL CORTEX ASSOCIATED WITH CLINICAL NOT GENETIC RISK FOR PSYCHOSIS

regions known as Cortical Midline Structures (CMS) is critically involved in these self-reflection processes. Furthermore, structural imaging studies in patients with schizophrenia have shown abnormalities in this region which correlate with impaired insight. A recent meta-analysis of fMRI studies in healthy individuals on self-reflective processing by van der Meer et al. (2010) confirmed the involvement of the CMS, and more specifically the importance of two regions within the medial prefrontal cortex (MPFC). The ventral MPFC is specifically involved in self-reflective processing, whereas the dorsal MPFC is involved in selfas well as other-reflective processing. A model was developed in which the vMPFC is involved in tagging information relevant for “self”, whereas the dMPFC is involved in decision making processes in selfand other-referential processing. Methods: This model was the starting point in an fMRI study in 40 patients with schizophrenia. More specifically, the relationship between brain activation during self-reflection and illness insight was investigated. Results: Results suggest that schizophrenia patients show an abnormal pattern of activation in self-reflective processing in relation to controls. Results concerning the relationship with insight will be presented. Discussion: More knowledge on the neural basis of impaired self-reflective processing in schizophrenia, a core feature of the disorder, may help understand the origins of the specific problems these patients have and may help to evaluate new treatment strategies.

Neural substrates of smoking cue reactivity: A meta-analysis of fMRI studies

Reactivity to smoking-related cues may be an important factor that precipitates relapse in smokers who are trying to quit. The neurobiology of smoking cue reactivity has been investigated in several fMRI studies. We combined the results of these studies using activation likelihood estimation, a meta-analytic technique for fMRI data. Results of the meta-analysis indicated that smoking cues reliably evoke larger fMRI responses than neutral cues in the extended visual system, precuneus, posterior cingulate gyrus, anterior cingulate gyrus, dorsal and medial prefrontal cortex, insula, and dorsal striatum. Subtraction meta-analyses revealed that parts of the extended visual system and dorsal prefrontal cortex are more reliably responsive to smoking cues in deprived smokers than in non-deprived smokers, and that short-duration cues presented in event-related designs produce larger responses in the extended visual system than long-duration cues presented in blocked designs. The areas that were found to be responsive to smoking cues agree with theories of the neurobiology of cue reactivity, with two exceptions. First, there was a reliable cue reactivity effect in the precuneus, which is not typically considered a brain region important to addiction. Second, we found no significant effect in the nucleus accumbens, an area that plays a critical role in addiction, but this effect may have been due to technical difficulties associated with measuring fMRI data in that region. The results of this meta-analysis suggest that the extended visual system should receive more attention in future studies of smoking cue reactivity.

Exposure to subliminal arousing stimuli induces robust activation in the amygdala, hippocampus, anterior cingulate, insular cortex and primary visual cortex: A systematic meta-analysis of fMRI studies

Functional Magnetic Resonance Imaging (fMRI) demonstrates that the subliminal presentation of arousing stimuli can activate subcortical brain regions independently of consciousness-generating top-down cortical modulation loops. Delineating these processes may elucidate mechanisms for arousal, aberration in which may underlie some psychiatric conditions. Here we are the first to review and discuss four Activation Likelihood Estimation (ALE) meta-analyses of fMRI studies using subliminal paradigms. We find a maximum of 9 out of 12 studies using subliminal presentation of faces contributing to activation of the amygdala, and also a significantly high number of studies reporting activation in the bilateral anterior cingulate, bilateral insular cortex, hippocampus and primary visual cortex. Subliminal faces are the strongest modality, whereas lexical stimuli are the weakest. Meta-analyses independent of studies using Regions of Interest (ROI) revealed no biasing effect. Core neuronal arousal in the brain, which may be at first independent of conscious processing, potentially involves a network incorporating primary visual areas, somatosensory, implicit memory and conflict monitoring regions. These data could provide candidate brain regions for the study of psychiatric disorders associated with aberrant automatic emotional processing.