Biomedical subjects

Michael J Brammer

Publications and source records attributed to Michael J Brammer.

At least 19 recordsLinked to original sources

PubMed2007

Detecting functional nodes in large-scale cortical networks with functional magnetic resonance imaging: a principal component analysis of the human visual system.

This study aimed to demonstrate how a regional variant of principal component analysis (PCA) can be used to delineate the known functional subdivisions of the human visual system. Unlike conventional eigenimage analysis, PCA was carried out as a second-level analysis subsequent to model-based General Linear Model (GLM)-type functional activation mapping. Functional homogeneity of the functional magnetic resonance imaging (fMRI) time series within and between clusters was examined on several levels of the visual network, starting from the level of individual clusters up to the network level comprising two or more distinct visual regions. On each level, the number of significant components was identified and compared with the number of clusters in the data set. Eigenimages were used to examine the regional distribution of the extracted components. It was shown that voxels within individual clusters and voxels located in bilateral homologue visual regions can be represented by a single component, constituting the characteristic functional specialization of the cluster(s). If, however, PCA was applied to time series of voxels located in functionally distinct visual regions, more than one component was observed with each component being dominated by voxels in one of the investigated regions. The model of functional connections derived by PCA was in accordance with the well-known functional anatomy and anatomical connectivity of the visual system. PCA in combination with conventional activation mapping might therefore be used to identify the number of functionally distinct nodes in an fMRI data set in order to generate a model of functional connectivity within a neuroanatomical network.

Adult↗

PubMed2006

How metaphors influence semantic relatedness judgments: the role of the right frontal cortex.

We used event-related fMRI (ER-fMRI) to test the hypothesis that metaphors bias cognitive processing of semantic relatedness towards a search for a wider range of associations. Twelve right-handed male volunteers read a mixture of metaphoric and literal sentences, each sentence being followed by a single word, which could be semantically related or not to the preceding sentence context. We found that judging unrelated words as contextually irrelevant was associated with increased blood oxygenation level-dependent (BOLD) signal in the right ventrolateral prefrontal cortex in the metaphoric but not in the literal condition. The same region was also activated when subjects endorsed a semantic relation between words and metaphoric sentence primes but not between words and literal sentence primes. We argue that these results are consistent with the notion of semantic open-endedness, whereby figurative statements bias cognitive processing towards a search for a wider range of semantic relationships compared to literal statements, and thus lend further support to the view that coarse semantic coding occurs preferentially in the right hemisphere.

Brain Mapping↗

PubMed2006

Time-resolved fMRI of mental rotation revisited--dissociating visual perception from mental rotation in female subjects.

Functional neuroimaging studies have demonstrated that mental rotation paradigms activate a network of spatially distributed cortical areas rather than a discrete brain region. Although the neuro-anatomical nodes of the rotation network are well established, their specific functional role is less well identified. It was the aim of the present study to dissociate network components involved in the visual perception of 3D cubic objects from regions involved in their mental spatial transformation. This was achieved by desynchronizing the time course of the perceptional process (i.e., stimulus duration) from the duration of the cognitive process (i.e., reaction times) and by comparing these with the temporal characteristics of the hemodynamic response functions (HRFs) in regions of interest. To minimize intersubject variability, an all-female subject group was chosen for this investigation. Time-resolved fMRI analysis revealed a significant increase in the full width at half maximum (FWHM) of the HRF with reaction times in the supplementary motor area (pre-SMA), in the bilateral premotor cortex (PMd-proper), and in the left parietal lobe (PP). The FWHM in visual system components such as the bilateral lateral occipital complex (LOC) and dorsal extrastriate visual areas (DE) was constant across trials and roughly equal to the stimulus duration. These findings suggest that visual system activation during mental rotation reflects visual perception and can be dissociated from other network components whose response characteristics indicates an involvement in the mental spatial transformation itself.

Adult↗

PubMed2006

Cerebral processing of food-related stimuli: effects of fasting and gender.

To maintain nutritional homeostasis, external food-related stimuli have to be evaluated in relation to the internal states of hunger or satiety. To examine the neural circuitry responsible for integration of internal and external determinants of human eating behaviour, brain responses to visual and complex gustatory food-related stimuli were measured using functional magnetic resonance imaging in 18 healthy non-smokers (10 women, 8 men). Each individual was studied on two occasions, the order of which was counterbalanced; after eating as usual and after 24 h fasting. Raised plasma free fatty acids and lower insulin and leptin concentrations confirmed that participants fasted as requested. When fasted, participants reported more hunger, nervousness and worse mood and rated the visual (but not gustatory) food-related stimuli as more pleasant. The effect of fasting on hunger was stronger in women than in men. No circuitry was identified as differentially responsive in fasting compared to satiety to both visual and gustatory food-related stimuli. The left insula response to the gustatory stimuli was stronger during fasting. The inferior occipito-temporal response to visual food-related stimuli also tended to be stronger during fasting. The responses in the occipito-temporal cortex to visual and in the insula to gustatory stimuli were stronger in women than in men. There was no interaction between gender and fasting. In conclusion, food reactivity in modality-specific sensory cortical areas is modulated by internal motivational states. The stronger reactivity to external food-related stimuli in women may be explored as a marker of gender-related susceptibility to eating disorders.

Adult↗

PubMed2006

Lexical and sentential processing in British Sign Language.

Studies of spoken and written language suggest that the perception of sentences engages the left anterior and posterior temporal cortex and the left inferior frontal gyrus to a greater extent than non-sententially structured material, such as word lists. This study sought to determine whether the same is true when the language is gestural and perceived visually. Regional neural activity was measured using functional MRI while Deaf and hearing native signers of British Sign Language (BSL) detected semantic anomalies in well-formed BSL sentences and when they detected nonsense signs in lists of unconnected BSL signs. Processing BSL sentences, when contrasted with signed lists, was reliably associated with greater activation in the posterior portions of the left middle and superior temporal gyri and in the left inferior frontal cortex, but not in the anterior temporal cortex, which was activated to a similar extent whether lists or sentences were processed. Further support for the specificity of these areas for processing the linguistic-rather than visuospatial-features of signed sentences came from a contrast of hearing native signers and hearing sign-naïve participants. Hearing signers recruited the left posterior temporal and inferior frontal regions during BSL sentence processing to a greater extent than hearing non-signers. These data suggest that these left perisylvian regions are differentially associated with sentence processing, whatever the modality of the linguistic input.

Adolescent↗

PubMed2006

Human attachment security is mediated by the amygdala: evidence from combined fMRI and psychophysiological measures.

The neural basis of human attachment security remains unexamined. Using event-related functional magnetic resonance imaging (fMRI) and simultaneous recordings of skin conductance levels, we measured neural and autonomic responses in healthy adult individuals during a semantic conceptual priming task measuring human attachment security "by proxy". Performance during a stress but not a neutral prime condition was associated with response in bilateral amygdalae. Furthermore, levels of activity within bilateral amygdalae were highly positively correlated with attachment insecurity and autonomic response during the stress prime condition. We thereby demonstrate a key role of the amygdala in mediating autonomic activity associated with human attachment insecurity.

Adult↗

PubMed2006

A systematic review and quantitative appraisal of fMRI studies of verbal fluency: role of the left inferior frontal gyrus.

The left inferior frontal gyrus (LIFG) has consistently been associated with both phonologic and semantic operations in functional neuroimaging studies. Two main theories have proposed a different functional organization in the LIFG for these processes. One theory suggests an anatomic parcellation of phonologic and semantic operations within the LIFG. An alternative theory proposes that both processes are encompassed within a supramodal executive function in a single region in the LIFG. To test these theories, we carried out a systematic review of functional magnetic resonance imaging studies employing phonologic and semantic verbal fluency tasks. Seventeen articles meeting our pre-established criteria were found, consisting of 22 relevant experiments with 197 healthy subjects and a total of 41 peak activations in the LIFG. We determined 95% confidence intervals of the mean location (x, y, and z coordinates) of peaks of blood oxygenation level-dependent (BOLD) responses from published phonologic and semantic verbal fluency studies using the nonparametric technique of bootstrap analysis. Significant differences were revealed in dorsal-ventral (z-coordinate) localizations of the peak BOLD response: phonologic verbal fluency peak BOLD response was significantly more dorsal to the peak associated with semantic verbal fluency (confidence interval of difference: 1.9-17.4 mm). No significant differences were evident in antero-posterior (x-coordinate) or medial-lateral (y-coordinate) positions. The results support distinct dorsal-ventral locations for phonologic and semantic processes within the LIFG. Current limitations to meta-analytic integration of published functional neuroimaging studies are discussed.

Brain Mapping↗

PubMed2006

Evidence against functionalism from neuroimaging of the alien colour effect in synaesthesia.

Coloured hearing synaesthetes experience colours to heard words, as confirmed by reliability of self-report, psychophysical testing and functional neuroimaging data. Some also describe the 'alien colour effect' (ACE): in response to colour names, they experience colours different from those named. We have previously reported that the ACE slows colour naming in a Stroop task, reflecting cognitive interference from synaesthetically induced colours, which depends upon their being consciously experienced. It has been proposed that the hippocampus mediates such consciously experienced conflict. Consistent with this hypothesis, we now report that, in functional magnetic resonance imaging of the Stroop task, hippocampal activation differentiates synaesthetes with the ACE from those without it and from non-synaesthete controls. These findings confirm the reality of coloured hearing synaesthesia and the ACE, phenomena which pose major challenges to the dominant contemporary account of mental states, functionalism. Reductive functionalism identifies types of mental states with causal roles: relations to inputs, outputs and other states. However, conscious mental states, such as experiences of colour, are distinguished by their qualitative properties or qualia. If functionalism is applied to conscious mental states, it identifies the qualitative type of an experience with its causal role or function. This entails both that experiences with disparate qualitative properties cannot have the same functional properties, and that experiences with disparate functional properties cannot have the same qualitative properties. Challenges to functionalism have often denied the first entailment. Here, we challenge the second entailment on empirical grounds. In coloured hearing synaesthesia, colour qualia are associated with both hearing words and seeing surfaces; and, in the ACE, these two functions act in opposition to one another. Whatever its merits as an account of other mental states, reductive functionalism cannot be the correct account of conscious experiences.

Adult↗

PubMed2006

Stroop performance in bipolar disorder: further evidence for abnormalities in the ventral prefrontal cortex.

OBJECTIVES: Bipolar patients are impaired in Stroop task performance, a measure of selective attention. Structural and functional abnormalities in task-associated regions, in particular the prefrontal cortex (PFC), have been reported in this population. We aimed to examine the relationship between functional abnormalities, impaired task performance and the severity of depressive symptoms in bipolar patients. METHODS: Remitted bipolar patients (n = 10; all medicated), either euthymic or with subsyndromal depression, and age-matched control subjects (n = 11) viewed 10 alternating blocks of incongruent Stroop and control stimuli, naming the colour of the ink. Neural response was measured using functional magnetic resonance imaging. We computed between-group differences in neural response and within-group correlations with mood and anxiety. RESULTS: There were no significant between-group differences in task performance. During the Stroop condition, controls demonstrated greater activation of visual and dorsolateral and ventrolateral prefrontal cortical areas; bipolar patients demonstrated relative deactivation within orbital and medial prefrontal cortices. Depression scores showed a trend towards a negative correlation with the magnitude of orbitofrontal cortex deactivation in bipolar patients, whereas state anxiety correlated positively with activation of dorsolateral PFC and precuneus in controls. CONCLUSIONS: Our findings confirm previous reports of decreased ventral prefrontal activity during Stroop task performance in bipolar patients, and suggest a possible negative correlation between this and depression severity in bipolar patients. These findings further highlight the ventromedial PFC as a potential candidate for illness related dysfunction in bipolar disorder.

Adult↗

PubMed2006

Facial emotion processing in criminal psychopathy. Preliminary functional magnetic resonance imaging study.

BACKGROUND: It has been suggested that people with psychopathic disorders lack empathy because they have deficits in processing distress cues (e.g. fearful facial expressions). AIMS: To investigate brain function when individuals with psychopathy and a control group process facial emotion. METHOD: Using event-related functional magnetic resonance imaging we compared six people scoring > or =25 on the Hare Psychopathy Checklist-Revised and nine non-psychopathic healthy volunteers during an implicit emotion processing task using fearful, happy and neutral faces. RESULTS: The psychopathy group showed significantly less activation than the control group in fusiform and extrastriate cortices when processing both facial emotions. However, emotion type affected response pattern. Both groups increased fusiform and extrastriate cortex activation when processing happy faces compared with neutral faces, but this increase was significantly smaller in the psychopathy group. In contrast, when processing fearful faces compared with neutral faces, the control group showed increased activation but the psychopathy group decreased activation in the fusiform gyrus. CONCLUSIONS: People with psychopathy have biological differences from controls when processing facial emotion, and the pattern of response differs according to emotion type.

Antisocial Personality Disorder↗

PubMed2005

An fMRI study of verbal self-monitoring: neural correlates of auditory verbal feedback.

The ability to recognize one's own inner speech is essential for a sense of self. The verbal self-monitoring model proposes that this process entails a communication from neural regions involved in speech production to areas of speech perception. According to the model, if the expected verbal feedback matches the perceived feedback, then there would be no change in activation in the lateral temporal cortices. We investigated the neural correlates of verbal self-monitoring in a functional magnetic resonance (fMRI) study. Thirteen healthy male volunteers read aloud presented adjectives and heard their auditory feedback which was experimentally modified. Decisions about the source of the feedback were made with a button-press response. We used a 'clustered' fMRI acquisition sequence, consisting of periods of relative silence in which subjects could speak aloud and hear the feedback in the absence of scanner noise, and an event-related design which allowed separate analysis of trials associated with correct attributions and misattributions. Subjects made more misattribution responses when the feedback was a distorted version of their voice. This condition showed increased superior temporal activation relative to the conditions of hearing their own voice undistorted and hearing another person's voice. Furthermore, correct attributions during this condition were associated with greater temporal activation than misattributions. These findings support the self-monitoring model as mismatches between expected and actual auditory feedback were associated with greater temporal activation.

Adult↗

PubMed2005

Deriving meaning: Distinct neural mechanisms for metaphoric, literal, and non-meaningful sentences.

In this study, we used a novel cognitive paradigm and event-related functional magnetic resonance imaging (ER-fMRI) to investigate the neural substrates involved in processing three different types of sentences. Participants read either metaphoric (Some surgeons are butchers), literal (Some surgeons are fathers), or non-meaningful sentences (Some surgeons are shelves) and had to decide whether they made sense or not. We demonstrate that processing of the different sentence types relied on distinct neural mechanisms. Activation of the left inferior frontal gyrus (LIFG), BA 47, was shared by both non-meaningful and metaphoric sentences but not by literal sentences. Furthermore, activation of the left thalamus appeared to be specifically involved in deriving meaning from metaphoric sentences despite lack of reaction times differences between literals and metaphors. We assign this to the ad hoc concept construction and open-endedness of metaphoric interpretation. In contrast to previous studies, our results do not support the view the right hemispheric is specifically involved in metaphor comprehension.

Adult↗

PubMed2005

Functional neuroanatomy of body shape perception in healthy and eating-disordered women.

BACKGROUND: Abnormalities in perception and evaluation of body shape are a hallmark of eating disorders. METHODS: Brain responses to line drawings of underweight, normal weight, and overweight female bodies were measured with functional magnetic resonance imaging in 9 women with bulimia nervosa, 13 with anorexia nervosa, and 18 healthy women. Participants rated the stimuli for fear and disgust. RESULTS: In the three groups, the lateral fusiform gyrus, inferior parietal cortex, and lateral prefrontal cortex were activated in response to body shapes compared with the control condition (drawings of houses). The responses in the lateral fusiform gyrus and in the parietal cortex were less strong in patients with eating disorders compared with healthy control subjects. Patients with eating disorders rated the body shapes in all weight categories as more aversive than did healthy women. In the group with eating disorders, the aversion ratings correlated positively with activity in the right medial apical prefrontal cortex. CONCLUSIONS: Processing of female body shapes engages a distributed neural network, parts of which are underactive in women with eating disorders. The considerable variability in subjective emotional reaction to body shapes in patients with eating disorders is associated with differential activity in the prefrontal cortex.

Adult↗

PubMed2005

A differential pattern of neural response toward sad versus happy facial expressions in major depressive disorder.

BACKGROUND: Accurate recognition of facial expressions is crucial for social functioning. In depressed individuals, implicit and explicit attentional biases away from happy and toward sad stimuli have been demonstrated. These may be associated with the negative cognitions in these individuals. METHODS: Using event-related functional magnetic resonance imaging (fMRI), neural responses to happy and sad facial expressions were measured in 14 healthy individuals and 16 individuals with major depressive disorder. RESULTS: Healthy but not depressed individuals demonstrated linear increases in response in bilateral fusiform gyri and right putamen to expressions of increasing happiness, while depressed individuals demonstrated linear increases in response in left putamen, left parahippocampal gyrus/amygdala, and right fusiform gyrus to expressions of increasing sadness. There was a negative correlation in depressed individuals between depression severity and magnitude of neural response within right fusiform gyrus to happy expressions. CONCLUSIONS: Our findings indicate preferential increases in neural response to sad but not happy facial expressions in neural regions involved in the processing of emotional stimuli in depressed individuals. These findings may be associated with the above pattern of implicit and explicit attentional biases in these individuals and suggest a potential neural basis for the negative cognitions and social dysfunction in major depression.

Adult↗

PubMed2005

BOLD, sweat and fears: fMRI and skin conductance distinguish facial fear signals.

It is not known how the brain and autonomic systems interact during perception of facial signals of danger. We recorded blood-oxygen-level-dependent (BOLD) activity using fMRI and simultaneous skin conductance measures of autonomic arousal in healthy subjects. Distinct response profiles were elicited for fear (enhanced arousal with amygdala activity), anger (rapid onset, slow recovery arousal responses with anterior cingulate) and disgust (delayed arousal responses with insula and basal ganglia activity). The findings suggest that fear, anger and disgust perception involves specific interactions in the neural arousal systems for emotion and motivation.

Adult↗

PubMed2005

Brain response to visceral aversive conditioning: a functional magnetic resonance imaging study.

BACKGROUND & AIMS: Brain-imaging studies to date have confounded visceral pain perception with anticipation. We used functional magnetic resonance imaging of the human brain to study the neuroanatomic network involved in aversive conditioning of visceral pain and, thus, anticipation. METHODS: Eight healthy volunteers (5 male) participated in the study. We used a classic conditioning paradigm in which 3 neutral stimuli (differently colored circles) that acted as conditioned stimuli were paired with painful esophageal distention, air puff to the wrist, or nothing, which acted as unconditioned stimuli. Neural activity was measured during learning, anticipation (pairing only 50% of conditioned stimuli with their unconditioned stimuli), and extinction (unpaired conditioned stimuli) phases. For magnetic resonance imaging, axial slices depicting blood oxygen level-dependent contrast were acquired with a 1.5-T system. RESULTS: Neural responses during the learning phase included areas commonly associated with visceral pain (anterior cingulate cortex, insula, and primary and secondary somatosensory cortices) and innocuous somatosensory perception (primary and secondary somatosensory cortices and insula). During the anticipation and extinction phases of aversive stimulation, brain activity resembled that seen during actual painful esophageal stimulation. In contrast, anticipation and extinction of the innocuous somatic stimulus failed to show that effect. CONCLUSIONS: We have shown that actual and anticipated visceral pain elicit similar cortical responses. These results have implications for the design and interpretation of brain-imaging studies of visceral pain. They not only contribute to our understanding of the processing of visceral pain, but also have clinical implications for the management of chronic pain states.

Adult↗

PubMed2005

Abnormal brain activation during inhibition and error detection in medication-naive adolescents with ADHD.

OBJECTIVE: Patients with attention deficit hyperactivity disorder (ADHD) and a medication history have shown abnormal brain activation in prefrontal and striatal brain regions during cognitive challenge. Previous findings have been confounded, however, by potential long-term effects of stimulant medication exposure and group discrepancies in task performance. The aim of this study was to investigate whether medication-naive adolescents with ADHD would still show abnormal brain activation in prefrontal brain regions during motor response inhibition in a task designed to control for intergroup performance discrepancies. METHOD: Rapid, event-related functional magnetic resonance imaging was used to compare brain activation in 16 medication-naive ADHD adolescents and 21 IQ-, age-, and sex-matched healthy comparison volunteers during a challenging, idiosyncratically adjusted task that required withholding of a triggered motor response. The design, which manipulated task parameters to force each subject to fail on 50% of trials, ensured that subjects worked at the edge of their own inhibitory performance, thereby controlling for intersubject and intergroup performance discrepancies and furthermore allowing for investigation of differences in brain activation related to inhibition and inhibition failure. RESULTS: Medication-naive adolescents with ADHD showed significantly reduced brain activation in the right inferior prefrontal cortex during successful motor response inhibition and in the precuneus and posterior cingulate gyrus during inhibition failure, both of which correlated with behavioral scores of ADHD. CONCLUSIONS: The study shows that abnormal brain activation during inhibitory challenge in ADHD is specific to the disorder, since it persists when medication history and performance discrepancies are excluded.

Adolescent↗

PubMed2005

Neural correlates of syntax production in schizophrenia.

BACKGROUND: The production of grammatically complex sentences is impaired in schizophrenia. It has been suggested that impaired syntax processing reflects a risk for the disorder. AIMS: To examine the neural correlates of syntax production in people with schizophrenia using functional magnetic resonance imaging (fMRI). METHOD: Six patients with schizophrenia and six healthy volunteers spoke about seven Rorschach inkblots for 3 min each while correlates of brain activation were measured with fMRI. Participants produced varying amounts of syntactically simple and complex sentences during each 3 min run. The number of simple and complex sentences was correlated separately with the BOLD contrast. RESULTS: In the comparison between the control group and the patient group, the number of complex sentences produced was correlated with activation in the posterior portion of the right middle temporal (Brodmann area 21) and left superior frontal (BA10) gyriin the control group but not in the patients. CONCLUSIONS: The absence of activation in the right posterior temporal and left superior frontal cortex in patients with schizophrenia might contribute to the articulation of grammatically more simple speech in people with this disorder.

Brain↗