Cortical representation of different taste modalities on the gustatory cortex: A pilot study

Background

Right insular cortex is involved in taste discrimination, but its functional organization is still poorly known. In general, sensory cortices represent the spatial prevalence of relevant features for each sensory modality (visual, auditory, somatosensory) in an ordered way across the cortical space. Following this analogy, we hypothesized that primary taste cortex is organized in similar ordered way in response to six tastes with known receptorial mechanisms (sweet, bitter, sour, salt, umami, CO₂)_.

Design

Ten normal subjects were enrolled in a pilot study. We used functional magnetic resonance imaging (fMRI), a high resolution cortical registration method, and specialized procedures of feature prevalence localization, to map fMRI responses within the right insular cortex, to water solutions of quinine hydrochloride (bitter), Acesulfamate K (sweet), sodium chloride (salt), mono potassium glutamate + inosine 5' mono phosphate (Umami), citric acid (sour) and carbonated water (CO₂). During an fMRI scan delivery of the solutions was applied in pseudo-random order interleaved with cleaning water.

Results

Two subjects were discarded due to excessive head movements. In the remaining subjects, statistically significant activations were detected in the fMRI responses to all tastes in the right insular cortex (p<0.05, family-wise corrected for multiple comparisons). Cortical representation of taste prevalence highlighted two spatially segregated clusters, processing two and three tastes coupled together (sweet-bitter and salt-umami-sour), with CO₂ in between.

Conclusions

Cortical representation of taste prevalence within the right primary taste cortex appears to follow the ecological purpose of enhancing the discrimination between safe nutrients and harmful substances.

Spectral signatures of mirror movements in the sensori-motor connectivity in kallmann syndrome

Mirror movements (MM) might be observed in congenital and acquired neurodegenerative conditions but their anatomic-functional underpinnings are still largely elusive. This study investigated the spectral changes of resting-state functional connectivity in Kallmann Syndrome (hypogonadotropic hypogonadism with hypo/anosmia with or without congenital MM) searching for insights into the phenomenon of MM. Forty-four Kallmann syndrome patients (21 with MM) and 24 healthy control subjects underwent task (finger tapping) and resting-state functional MRI. The spatial pattern of task-related activations was used to mask regions and select putative motor networks in a spatially independent component analysis of resting-state signals. For each resting-state independent component time-course power spectrum, we extracted the relative contribution of four separate bands: slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), slow-3 (0.073-0.198 Hz), slow-2 (0.198-0.25 Hz), and analyzed the variance between groups. For the sensorimotor network, the analysis revealed a significant group by frequency interaction (P = 0.002) pointing to a frequency shift in the spectral content among subgroups with lower slow-5 band and higher slow-3 band contribution in Kallmann patients with MM versus controls (P = 0.028) and with lower slow-5 band contribution between patients with and without MM (P = 0.057). In specific regions, as obtained from hand motor activation task analysis, spectral analyses demonstrated a lower slow-5 band contribution in Kallmann patients with MM versus both controls and patients without MM (P < 0.05). In Kallmann syndrome, the peculiar phenomenon of bimanual synkinesis is associated at rest with regionally and spectrally selective functional connectivity changes pointing to a distinctive cortical and subcortical functional reorganization. Hum Brain Mapp 39:42-53, 2018. © 2017 Wiley Periodicals, Inc.

Altered processing of rewarding and aversive basic taste stimuli in symptomatic women with anorexia nervosa and bulimia nervosa: An fMRI study

Functional magnetic resonance imaging (fMRI) studies have displayed a dysregulation in the way in which the brain processes pleasant taste stimuli in patients with anorexia nervosa (AN) and bulimia nervosa (BN). However, exactly how the brain processes disgusting basic taste stimuli has never been investigated, even though disgust plays a role in food intake modulation and AN and BN patients exhibit high disgust sensitivity. Therefore, we investigated the activation of brain areas following the administration of pleasant and aversive basic taste stimuli in symptomatic AN and BN patients compared to healthy subjects. Twenty underweight AN women, 20 symptomatic BN women and 20 healthy women underwent fMRI while tasting 0.292 M sucrose solution (sweet taste), 0.5 mM quinine hydrochloride solution (bitter taste) and water as a reference taste. In symptomatic AN and BN patients the pleasant sweet stimulus induced a higher activation in several brain areas than that induced by the aversive bitter taste. The opposite occurred in healthy controls. Moreover, compared to healthy controls, AN patients showed a decreased response to the bitter stimulus in the right amygdala and left anterior cingulate cortex, while BN patients showed a decreased response to the bitter stimulus in the right amygdala and left insula. These results show an altered processing of rewarding and aversive taste stimuli in ED patients, which may be relevant for understanding the pathophysiology of AN and BN.

Interhemispheric functional connectivity in anorexia and bulimia nervosa

The functional interplay between hemispheres is fundamental for behavioral, cognitive, and emotional control. Anorexia nervosa (AN) and bulimia nervosa (BN) have been largely studied with brain magnetic resonance imaging (MRI) in relation to the functional mechanisms of high-level processing, but not in terms of possible inter-hemispheric functional connectivity anomalies. Using resting-state functional MRI (fMRI), voxel-mirrored homotopic connectivity (VMHC) and regional inter-hemispheric spectral coherence (IHSC) were studied in 15 AN and 13 BN patients and 16 healthy controls (HC). Using T1-weighted and diffusion tensor imaging MRI scans, regional VMHC values were correlated with the left-right asymmetry of corresponding homotopic gray matter volumes and with the white matter callosal fractional anisotropy (FA). Compared to HC, AN patients exhibited reduced VMHC in cerebellum, insula, and precuneus, while BN patients showed reduced VMHC in dorso-lateral prefrontal and orbito-frontal cortices. The regional IHSC analysis highlighted that the inter-hemispheric functional connectivity was higher in the 'Slow-5' band in all regions except the insula. No group differences in left-right structural asymmetries and in VMHC vs. callosal FA correlations were significant in the comparisons between cohorts. These anomalies, not explained by structural changes, indicate that AN and BN, at least in their acute phase, are associated with a loss of inter-hemispheric connectivity in regions implicated in self-referential, cognitive control and reward processing. These findings may thus gather novel functional markers to explore aberrant features of these eating disorders.

Effects of active music therapy on the normal brain: fMRI based evidence

The aim of this study was to investigate the neurophysiological bases of Active Music Therapy (AMT) and its effects on the normal brain. Twelve right-handed, healthy, non-musician volunteers were recruited. The subjects underwent 2 AMT sessions based on the free sonorous-music improvisation using rhythmic and melodic instruments. After these sessions, each subject underwent 2 fMRI scan acquisitions while listening to a Syntonic (SP) and an A-Syntonic (AP) Production from the AMT sessions. A 3 T Discovery MR750 scanner with a 16-channel phased array head coil was used, and the image analysis was performed with Brain Voyager QX 2.8. The listening to SP vs AP excerpts mainly activated: (1) the right middle temporal gyrus and right superior temporal sulcus, (2) the right middle frontal gyrus and in particular the right precentral gyrus, (3) the bilateral precuneus, (4) the left superior temporal sulcus and (5) the left middle temporal gyrus. These results are consistent with the psychological bases of the AMT approach and with the activation of brain areas involved in memory and autobiographical processes, and also in personal or interpersonal significant experiences. Further studies are required to confirm these findings and to explain possible effects of AMT in clinical settings.

Sniffin' Sticks and olfactory system imaging in patients with Kallmann syndrome

BACKGROUND

The relationship between olfactory function, rhinencephalon and forebrain changes in Kallmann syndrome (KS) have not been adequately investigated. We evaluated a large cohort of male KS patients using Sniffin' Sticks and MRI in order to study olfactory bulb (OB) volume, olfactory sulcus (OS) depth, cortical thickness close to the OS, and olfactory phenotype.

METHODS

Olfaction was assessed administering Sniffin' Sticks®, in 38 KS patients and 17 controls (by means of Screening 12 test®). All subjects underwent magnetic resonance imaging (MRI) to study OB volume, sulcus depth, and cortical thickness.

RESULTS

Compared to controls, KS patients showed smaller OB volume (p<0.0001), reduced sulcus depth (p<0.0001), and thicker cortex in the region close to the OS (p<0.0001). Anosmic KS patients had smaller OB than controls and hyposmic KS patients; there was no difference between hyposmic KS patients and controls. OB volume correlated with Sniffin' Sticks score (r = 0.64; p < 0.001), OS depth (p<0.0001) and, inversely, with cortical thickness changes (p<0.0001). Sniffin' Sticks showed an inverse correlation with cortical thickness (r = -0.5; p<0.0001) and a trend toward a statistically significant correlation with OS depth.

CONCLUSION

The present study provides further evidence of the strict relationship between olfaction and OB volume. The strong correlation between OB volume and the overlying cortical changes highlights the key role of rhinencephalon in forebrain embryogenesis.

Intracranial internal carotid artery changes in acromegaly: a quantitative magnetic resonance angiography study

PURPOSE

Although cerebrovascular mortality is increased up to eightfold in acromegaly, intracranial internal carotid artery (ICA) changes have not been well investigated. This is a magnetic resonance angiography (MRA) quantitative cross-sectional study of ICA tortuosity, ectasia and intercarotid distance in acromegalic patients with subsequent analysis of concomitant clinical, laboratory and neuroimaging findings.

METHODS

One hundred seventy six acromegalic patients (mean-age 55 ± 14 years, age range 21-88, 92 females) and 104 subjects with headache or transient neurological deficits underwent MRA with the same 1.5 T scanner. Clinical data, laboratory and pituitary adenoma imaging findings were recorded. Using a commercially available software, we measured the tortuosity index [(curved/linear ICA length from C3-midpoint to intracranial bifurcation) - 1], ICA ectasia index (intracavernous/petrous ICA diameter) and intercarotid distance at C3 and C4 levels.

RESULTS

Mean ICA tortuosity and ectasia indices were increased in acromegalic patients compared with controls (1.06 ± 0.29 vs 0.93 ± 0.26, p < 0.001; 1.02 ± 0.10 vs 0.92 ± 0.09, p < 0.001). Mean intercarotid distance was reduced at C3 and increased at C4 in acromegalic patients (16.7 ± 3.4 vs 17.9 ± 2.5 mm, p < 0.001; 16.7 ± 4.6 vs 15.4 ± 4.1 mm, p < 0.05; t test). ICA tortuosity and ectasia correlated neither with laboratory findings nor with previous or current treatment. On multivariate analysis, C3 intercarotid distance was reduced in patients on dopamine agonist treatment (p < 0.01) and increased in patients with GH-deficit (p = 0.01), while C4 intercarotid distance was increased with macroadenoma (p = 0.01) and reduced in patients under dopamine agonist (p < 0.01) or somatostatin analogue (p < 0.05) treatment.

CONCLUSIONS

Intracranial ICA changes are common findings in acromegaly, and further studies focused on their possible clinical impact are needed.

Limbic hyperconnectivity in the vegetative state

OBJECTIVE

To investigate functional connectivity between the default mode network (DMN) and other networks in disorders of consciousness.

METHODS

We analyzed MRI data from 11 patients in a vegetative state and 7 patients in a minimally conscious state along with age- and sex-matched healthy control subjects. MRI data analysis included nonlinear spatial normalization to compensate for disease-related anatomical distortions. We studied brain connectivity data from resting-state MRI temporal series, combining noninferential (independent component analysis) and inferential (seed-based general linear model) methods.

RESULTS

In DMN hypoconnectivity conditions, a patient's DMN functional connectivity shifts and paradoxically increases in limbic structures, including the orbitofrontal cortex, insula, hypothalamus, and the ventral tegmental area.

CONCLUSIONS

Concurrently with DMN hypoconnectivity, we report limbic hyperconnectivity in patients in vegetative and minimally conscious states. This hyperconnectivity may reflect the persistent engagement of residual neural activity in self-reinforcing neural loops, which, in turn, could disrupt normal patterns of connectivity.

Effect of carbonation on brain processing of sweet stimuli in humans

Little is known about how CO2 affects neural processing of taste. We used functional magnetic resonance imaging to investigate the effects of carbonation on brain processing of sweet stimuli, which has relevance to studies of food selection and satiety. The presence of carbonation produced an overall decrease in the neural processing of sweetness-related signals, especially from sucrose. CO2 reduced the neural processing of sucrose more than that of artificial sweeteners. These findings might be relevant to dietary interventions that include noncaloric beverages, whereas the combination of CO2 and sucrose might increase consumption of sucrose.

Catechol-O-methyltransferase genotype modifies executive functioning and prefrontal functional connectivity in women with anorexia nervosa

BACKGROUND

Anorexia nervosa is characterized by high levels of perseveration and inflexibility, which interfere with successful treatments. Dopamine (DA) signalling seems to play a key role in modulating the prefrontal cortex, since both DA deficiency and excess nega tively influence the efficiency of cognitive functions. The present study explores the effect of a functional polymorphism (Val158Met) in the catechol-O-methyltransferase (COMT) gene on the set-shifting abilities and prefrontal functional connectivity of patients with anorexia nervosa.

METHODS

All participants performed the Wisconsin Card Sorting Task, and a subsample underwent resting-state functional magnetic resonance imaging.

RESULTS

We included 166 patients with DSM-IV lifetime anorexia nervosa and 140 healthy women in our study. Both underweight and weight-recovered patients with anorexia nervosa showed high levels of perseveration, but only in the underweight group did the Val158Met polymorphism affect cognitive performance, showing the U-shaped curve characteristic of increased DA signalling in the prefrontal cortex. Underweight patients with anorexia nervosa who are Met homozygotes had significantly higher levels of perseveration and increased prefrontal functional connectivity than underweight patients in the other genotype groups, indicating abnormal regional cortical processing.

LIMITATIONS

Although our data show that grey matter reduction in starving patients with anorexia nervosa did not explain our findings, the cross-sectional design of the present study did not allow us to distinguish between the effects of starvation and those of low estrogen levels.

CONCLUSION

Starvation affects DA release in the prefrontal cortex of patients with anorexia nervosa with different effects on executive functioning and prefrontal functional connectivity according to the COMT genotype. This observation has several therapeutic implications that need to be addressed by future studies.

Brainstem activation in cluster headache: an adaptive behavioural response?

INTRODUCTION

The functional neuroimaging of headache patients has revolutionized our understanding of the pathophysiology of primary headaches, providing unique insights into these syndromes. Indeed, functional neuroimaging studies have shown the activation of specific brain structures, the brainstem in migraine and posterior hypothalamus in cluster headache (CH), as well as in other trigeminal autonomic cephalalgias. We describe the functional neuroimaging findings in a patient suffering from CH headache, investigated with functional magnetic resonance imaging (fMRI) during typical pain attacks.

MATERIAL AND METHODS

Two typical, consecutive CH attacks were investigated by two fMRI imaging sessions on the same day. Both fMRI scans were performed at rest, during the CH attacks and the pain-free state induced by subcutaneous administration of sumatriptan.

RESULTS

Significant activation of the bilateral red nucleus, ventral pons and trigeminal root entry zone ipsilaterally to the pain side was detected during the pain state, in addition to the hypothalamic region ipsilaterally to the pain side.

CONCLUSION

Being that such structures are mainly involved in motor function and reactive behaviour, their activation, in our hypothesis, may be linked to pain avoidance and may well represent a defence reaction in cluster headache, which is characterised by a "fight-or-flight" type behavioural pattern during pain attacks.

Disruption of visuospatial and somatosensory functional connectivity in anorexia nervosa

BACKGROUND

Although body image disturbance is considered one of the core characteristics of anorexia nervosa (AN), the exact nature of this complex feature is poorly understood. Task-related functional magnetic resonance imaging studies can only partially explore the multimodal complexity of body consciousness, which is a complex cognition underpinned by aspects of visual perception, proprioception, and touch. The aim of the present study was to explore the functional connectivity of networks involved in visuospatial and somatosensory processing in AN.

METHODS

Twenty-nine subjects with AN, 16 women who had recovered from it, and 26 healthy women underwent a resting-state functional magnetic resonance imaging scan and neuropsychological assessment of their visuospatial abilities using the Rey-Osterrieth Complex Figure Test.

RESULTS

Both AN groups showed areas of decreased connectivity in the ventral visual network, a network involved in the "what?" pathway of visual perception. Even more interestingly, the AN group, but not the recovered AN group, displayed increased coactivation in the left parietal cortex, encompassing the somatosensory cortex, in an area implicated in long-term multimodal spatial memory and representation, even in the absence of visual information. A neuropsychological assessment of visuospatial abilities revealed that aspects of detail processing and global integration (central coherence) showed correlations with connectivity of this brain area in the AN group.

CONCLUSIONS

Our findings show that AN is associated with double disruption of brain connectivity, which shows a specific association with visuospatial difficulties and may explain the failure of the integration process between visual and somatosensory perceptual information that might sustain body image disturbance.

Pain processing in medication overuse headache: a functional magnetic resonance imaging (fMRI) study

OBJECTIVE

The primary aim was to investigate functional differences between medication overuse headache (MOH) patients and controls with the purpose of evaluating the presence of a global alteration in the processing of noxious stimuli throughout the pain matrix. The secondary aim was to investigate whether activations in MOH patients normalize after medication withdrawal, which would suggest a possible role of the pain matrix in headache chronification.

DESIGN

Functional magnetic resonance imaging was performed during painful mechanical stimulation in nine female patients with MOH immediately and at 6 months after beginning medication withdrawal, and in nine control participants.

RESULTS

Compared with controls, immediately after beginning withdrawal, the MOH patients showed reduced pain-related activity across the primary somatosensory cortex, inferior parietal lobule, and supramarginal gyrus, as well as in regions of the lateral pathway of the pain matrix. At 6 months, these differences were no longer detectable.

CONCLUSION

Our findings suggest that significant functional changes occur in the lateral pain pathway in MOH patients. These could result from different processes: 1) cortical down-regulation aimed at reducing painful input to the cortex; 2) activity-dependent plasticity induced by excessive painful input during migraine attacks; and 3) direct effect of medication overuse. At 6 months after withdrawal, activity in these regions normalized, suggesting that no irreversible changes occur due to medication overuse.

Language production and working memory in classic galactosemia from a cognitive neuroscience perspective: future research directions

Most humans are social beings and we express our thoughts and feelings through language. In contrast to the ease with which we speak, the underlying cognitive and neural processes of language production are fairly complex and still little understood. In the hereditary metabolic disease classic galactosemia, failures in language production processes are among the most reported difficulties. It is unclear, however, what the underlying neural cause of this cognitive problem is. Modern brain imaging techniques allow us to look into the brain of a thinking patient online - while she or he is performing a task, such as speaking. We can measure indirectly neural activity related to the output side of a process (e.g. articulation). But most importantly, we can look into the planning phase prior to an overt response, hence tapping into subcomponents of speech planning. These components include verbal memory, intention to speak, and the planning of meaning, syntax, and phonology. This paper briefly introduces cognitive theories on language production and methods used in cognitive neuroscience. It reviews the possibilities of applying them in experimental paradigms to investigate language production and verbal memory in galactosemia.

The brain functional networks associated to human and animal suffering differ among omnivores, vegetarians and vegans

Empathy and affective appraisals for conspecifics are among the hallmarks of social interaction. Using functional MRI, we hypothesized that vegetarians and vegans, who made their feeding choice for ethical reasons, might show brain responses to conditions of suffering involving humans or animals different from omnivores. We recruited 20 omnivore subjects, 19 vegetarians, and 21 vegans. The groups were matched for sex and age. Brain activation was investigated using fMRI and an event-related design during observation of negative affective pictures of human beings and animals (showing mutilations, murdered people, human/animal threat, tortures, wounds, etc.). Participants saw negative-valence scenes related to humans and animals, alternating with natural landscapes. During human negative valence scenes, compared with omnivores, vegetarians and vegans had an increased recruitment of the anterior cingulate cortex (ACC) and inferior frontal gyrus (IFG). More critically, during animal negative valence scenes, they had decreased amygdala activation and increased activation of the lingual gyri, the left cuneus, the posterior cingulate cortex and several areas mainly located in the frontal lobes, including the ACC, the IFG and the middle frontal gyrus. Nonetheless, also substantial differences between vegetarians and vegans have been found responding to negative scenes. Vegetarians showed a selective recruitment of the right inferior parietal lobule during human negative scenes, and a prevailing activation of the ACC during animal negative scenes. Conversely, during animal negative scenes an increased activation of the inferior prefrontal cortex was observed in vegans. These results suggest that empathy toward non conspecifics has different neural representation among individuals with different feeding habits, perhaps reflecting different motivational factors and beliefs.

Comparison between realistic and spherical approaches in EEG forward modelling

In electroencephalography (EEG) a valid conductor model of the head (forward model) is necessary for predicting measurable scalp voltages from intra-cranial current distributions. All inverse models, capable of inferring the spatial distribution of the neural sources generating measurable electrical and magnetic signals outside the brain are normally formulated in terms of a pre-estimated forward model, which implies considering one (or more) current dipole(s) inside the head and computing the electrical potentials generated at the electrode sites on the scalp surface. Therefore, the accuracy of the forward model strongly affects the reliability of the source reconstruction process independently of the specific inverse model. So far, it is as yet unclear which brain regions are more sensitive to the choice of different model geometry, from both quantitative and qualitative points of view. In this paper, we compare the finite difference method-based realistic model with the four-layers sensor-fitted spherical model using simulated cortical sources in the MNI152 standard space. We focused on the investigation of the spatial variation of the lead fields produced by simulated cortical sources which were placed on the reconstructed mesh of the neocortex along the surface electrodes of a 62-channel configuration. This comparison is carried out by evaluating a point spread function all over the brain cortex, with the aim of finding the lead fields mismatch between realistic and spherical geometry. Realistic geometry turns out to be a relevant factor of improvement which is particularly important when considering sources placed in the temporal or in the occipital cortex. In these situations, using a realistic head model will allow a better spatial discrimination of neural sources when compared to the spherical model.

Realistic and spherical head modeling for EEG forward problem solution: a comparative cortex-based analysis

The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.

Metabolic and hemodynamic events after changes in neuronal activity: current hypotheses, theoretical predictions and in vivo NMR experimental findings

Unraveling the energy metabolism and the hemodynamic outcomes of excitatory and inhibitory neuronal activity is critical not only for our basic understanding of overall brain function, but also for the understanding of many brain disorders. Methodologies of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are powerful tools for the noninvasive investigation of brain metabolism and physiology. However, the temporal and spatial resolution of in vivo MRS and MRI is not suitable to provide direct evidence for hypotheses that involve metabolic compartmentalization between different cell types, or to untangle the complex neuronal microcircuitry, which results in changes of electrical activity. This review aims at describing how the current models of brain metabolism, mainly built on the basis of in vitro evidence, relate to experimental findings recently obtained in vivo by (1)H MRS, (13)C MRS, and MRI. The hypotheses related to the role of different metabolic substrates, the metabolic neuron-glia interactions, along with the available theoretical predictions of the energy budget of neurotransmission will be discussed. In addition, the cellular and network mechanisms that characterize different types of increased and suppressed neuronal activity will be considered within the sensitivity-constraints of MRS and MRI.

Visual target modulation of functional connectivity networks revealed by self-organizing group ICA

We applied a data-driven analysis based on self-organizing group independent component analysis (sogICA) to fMRI data from a three-stimulus visual oddball task. SogICA is particularly suited to the investigation of the underlying functional connectivity and does not rely on a predefined model of the experiment, which overcomes some of the limitations of hypothesis-driven analysis. Unlike most previous applications of ICA in functional imaging, our approach allows the analysis of the data at the group level, which is of particular interest in high order cognitive studies. SogICA is based on the hierarchical clustering of spatially similar independent components, derived from single subject decompositions. We identified four main clusters of components, centered on the posterior cingulate, bilateral insula, bilateral prefrontal cortex, and right posterior parietal and prefrontal cortex, consistently across all participants. Post hoc comparison of time courses revealed that insula, prefrontal cortex and right fronto-parietal components showed higher activity for targets than for distractors. Activation for distractors was higher in the posterior cingulate cortex, where deactivation was observed for targets. While our results conform to previous neuroimaging studies, they also complement conventional results by showing functional connectivity networks with unique contributions to the task that were consistent across subjects. SogICA can thus be used to probe functional networks of active cognitive tasks at the group-level and can provide additional insights to generate new hypotheses for further study.

Basic concepts of advanced MRI techniques

An overview is given of magnetic resonance (MR) techniques sensitized to diffusion, flow, magnetization transfer effect, and local field inhomogeneities induced by physiological changes, that can be viewed, in the clinical practice, as advanced because of their challenging implementation and interpretation. These techniques are known as diffusion-weighted, perfusion, magnetization transfer, functional MRI and MR spectroscopy. An important issue is that they can provide quantitative estimates of structural and functional characteristics that are below the voxel resolution. This review does not deal with the basic concepts of the MR physics and the description of the available acquisition and postprocessing methods, but hopefully provides an adequate background to readers and hence facilitate the understanding of the following clinical contributions.

Functional magnetic resonance imaging in episodic cluster headache

We have investigated the cerebral activation centre in four patients with episodic cluster headache (CH) with functional magnetic resonance imaging (f-MRI). The patients underwent MRI scans for anatomical and functional data acquisition in the asymptomatic state, during a headache attack and after subcutaneous administration of sumatriptan. Anatomical images were acquired by means of 3D-MPRAGE sequences and f-MRI images were obtained by means of echo-planar imaging. Data was analysed using the BrainVoyager QX version 1.7.81 software package. In all patients, the data showed significant hypothalamic activation of the hypothalamus ipsilateral to the pain side, attributable to a headache attack. Overall, we have demonstrated the anatomical location of central nervous system activation by means the first f-MRI study in CH patients. f-MRI offers a good balance of spatial and temporal resolution, and this method of study appears appropriate for investigating the pathogenetic aspects of primary headaches. Positron emission tomography and f-MRI may be regarded as little or no importance in a clinical context, they do, however, offer great potential for the exploration of headache physiopathology and the effects of pharmacological treatment.

A novel tool for the morphometric analysis of corpus callosum: applications to the diagnosis of autism - biomed 2009

Autism is a developmental disorder characterized by social deficits, impaired communication, and restricted and repetitive patterns of behaviour. Emerging theories indicate interregional functional and anatomical brain connectivity as a likely key feature in autism pathophysiology. Corpus callosum (CC) represents a natural target of autism connectivity research, being the expression of interhemispheric communication. In this paper, a novel method for a robust morphometric analysis of CC data is presented. The standard morphometric approach is based on the analysis of the size and shape of the CC midsagittal cross-section. As there are no gross anatomical landmarks that clearly delimit anatomically or functionally distinct CC regions, several geometric partitioning schemes have been proposed in the literature for morphometric analysis, subdividing CC into subregions whose fiber topography is expected to target different hemispheric cortical regions. A novel tool of morphometric analysis, based on the automated subdivision of a high number of partitions from a CC centroid and on the consequent determination of the CC anatomical landmarks is presented, allowing an automated analysis of CC volumes, shapes and curvatures, suitable for an automated application in clinical environment. Moreover the proposed tool can be used for original post-processing and visualization techniques that may help in the analysis of possible alterations of CC and in the correlations with autism-related diseases. The proposed morphometric tool has been validated and applied for clinical investigation on brain morphometry in children (age 3-11 years) with autism or with other autism spectrum disorders (DSA) and on healthy control subjects who underwent volumetric MRI T1 weighted acquisitions.