Functional anatomy of the insula: new insights from imaging

Epilepsia, 2010

Purpose: Different lines of evidence suggest that the insular cortex has many important functional roles. Direct electrical stimulation (ES) of the human insular cortex during surgical procedures for epilepsy, functional imaging techniques, and lesion studies also occasionally induces clinical responses. Methods: In this study, we evaluated 25 patients with drug-refractory focal epilepsy by stereotactically implanting at least one electrode into the insular cortex using an oblique approach (transfrontal or transparietal). One hundred twenty-eight insular sites (each situated between two contiguous contacts within the same electrode) were examined within the gyral substructures. We located each stimulation site by fusing preimplantation threedimensional (3D) magnetic resonance imaging (MRI) images with the postimplantation 3D computed tomography (CT) scans that revealed the electrode contacts.

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Brain, 2009

Magnetoencephalography (MEG) is considered a useful tool for planning electrode placement for chronic intracranial subdural electrocorticography (ECoG) in candidates for epilepsy surgery or even as a substitute for ECoG. MEG recordings are usually interictal and therefore, at best, reflect the interictal ECoG. To estimate the clinical value of MEG, it is important to know how well interictal MEG reflects interictal activity in the ECoG. From 1998 to 2008, 38 candidates for ECoG underwent a 151-channel MEG recording and 3D magnetic resonance imaging as a part of their presurgical evaluation. Interictal MEG spikes were identified, clustered, averaged and modelled using the multiple signal classification algorithm and co-registered to magnetic resonance imaging. ECoG was continuously recorded with electrode grids and strips for $1 week. In a representative sample of awake interictal ECoG, interictal spikes were identified and averaged. The different spikes were characterized and quantified using a combined amplitude and synchronous surface-area measure. The ECoG spikes were ranked according to this measure and plotted on the magnetic resonance imaging surface rendering. Interictal spikes in MEG and ECoG were allocated to a predefined anatomical brain region and an association analysis was performed. All interictal MEG spikes were associated with an interictal ECoG spike. Overall, 56% of all interictal ECoG spikes had an interictal MEG counterpart. The association between the two was 590% in the interhemispheric and frontal orbital region, $75% in the superior frontal, central and lateral temporal regions, but only $25% in the mesial temporal region. MEG is a reliable indicator of the presence of interictal ECoG spikes and can be used to plan intracranial electrode placements. However, a substantial number of interictal ECoG spikes are not detected by MEG, and therefore MEG cannot be considered a substitute for ECoG. Abbreviations: AROM = anatomical region of match; ECoG = electrocorticography; EEG = electroencephalography; MEG = magnetoencephalography; MUSIC = multiple signal classification; RMS_bg = root mean square amplitude of background; RMS_base = root mean square amplitude of baseline; RMS_spike = root mean square amplitude of spike; RMS_int = root mean square integrated value; SPECT = single photon emission computed tomography , although magnetoencephalography (MEG) is emerging as a powerful method to image the epileptic source (Stefan et al.

Radiologia Brasileira, 2011

O uso de sinais na interpretação de imagens na neurorradiologia é extremamente útil. Muitos sinais são bastante específicos e em alguns casos, patognomônicos. Nesta segunda parte os autores descreverão 15 sinais neurorradiológicos adicionais. Serão novamente abordadas as principais características de imagem de cada um e sua importância na prática clínica.

Journal of Neurology, Neurosurgery & Psychiatry, 2010

Influential models based on an increasing body of neuroimaging evidence propose that insular cortex integrates cognitive, affective, sensory and autonomic information to create a consciously perceived, "feeling state". To appraise these models and evaluate interpretations of neuroimaging findings, we review evidence pertaining to the psychological and behavioural consequences of insula lesions. We focus on the emotional, perceptual, sensorimotor symptoms and disorders of body awareness associated with insula damage. This comprehensive review is intended to inform existing neuropsychological models of insula function in order to guide future research.

Neuroimage, 2010

The human insula is hidden in the depth of the cerebral hemisphere by the overlying frontal and temporal opercula, and consists of three cytoarchitectonically distinct regions: the anterior agranular area, posterior granular area, and the transitional dysgranular zone; each has distinct histochemical staining patterns and specific connectivity. Even though there are several studies reporting the functional connectivity of the insula with the cingulated cortex, its relationships with other brain areas remain elusive in humans. Therefore, we decided to use resting state functional connectivity to elucidate in details its connectivity, in terms of cortical and subcortical areas, and also of lateralization. We investigated correlations in BOLD fluctuations between specific regions of interest of the insula and other brain areas of right-handed healthy volunteers, on both sides of the brain. Our findings document two major complementary networks involving the ventral-anterior and dorsal-posterior insula: one network links the anterior insula to the middle and inferior temporal cortex and anterior cingulate cortex, and is primarily related to limbic regions which play a role in emotional aspects; the second links the middle-posterior insula to premotor, sensorimotor, supplementary motor and middleposterior cingulate cortices, indicating a role for the insula in sensorimotor integration. The clear bipartition of the insula was confirmed by negative correlation analysis. Correlation maps are partially lateralized: the salience network, related to the ventral anterior insula, displays stronger connections with the anterior cingulate cortex on the right side, and with the frontal cortex on the left side; the posterior network has stronger connections with the superior temporal cortex and the occipital cortex on the right side. These results are in agreement with connectivity studies in primates, and support the use of resting state functional analysis to investigate connectivity in the living human brain.

Neuropsychology is an interdisciplinary field that studies the relationship among cognition, behavior, emotions and the brain, based on structure–function correlation models developed in the last 150 years. This study presents a discussion concerning the anatomo-clinical method in neuropsychology considering theoretical-methodological advancements that have contributed to this scientific discipline in recent decades. This method assumes that inferences concerning a given cognitive function can be made based on a correspondence between clinical manifestations and the brain injury site. First, we review historical aspects related to the emergence of the practice of exploring neuropsychological abilities in specific areas of the brain, that is, structure–function relationships. Then we discuss the limitations of the anatomo-clinical method and, finally, the current conception found in Neuropsychology, considering advanced imaging and cerebral stimulation techniques. The current conception of localizationism is more distributed. Large-scale networks are dedicated to specific functions such as language, face and object recognition, executive functions, spatial attention, and memory. The conclusion is that the anatomo-clinical method is still essential to grounding structure–function relationships, though caution should be applied in its use considering current conceptions of the brain being a complex system of interconnected regions subject to variations according to sociodemographic variables.

2019

International audienceThe subthalamic nucleus (STN) receives direct cortical inputs which constitute the so-called hyperdirect pathway. In monkeys, motor cortices innervate the whole extent of the STN whereas limbic cortices innervate only its anteromedial part extending more medially outside the nucleus. Tractography studies in humans have also identified motor cortical inputs to the STN, but little is known about the associative and limbic cortical projections. Therefore, the aim of this study was to investigate the anatomo-functional organization of the cortical projections to the STN and to the adjacent medial subthamic region (MSR). We used diffusion-weighted imaging-based tractography acquired from 30 subjects from the Human Connectome Project. We performed a whole-brain probabilistic tractography using MRTrix and extracted streamlines of interest between 39 cortical masks and both the STN and the MSR to provide track-density maps. Agglomerative clustering method was used to c...

2021

At present, there is only the Spanish facsimile edition of 2010, including two supplements a. The interest of the research described in this book lies in the fact that it is surprisingly of current interest, apart from its undoubted historical interest. Some aspects were ahead of discoveries that were made later. It is remarkable that some of the phenomena exposed are still unknown, or have only been observed in the last decades, and that the functional dynamic unity of the cortex proposed by the author is closely related to the current trends in the study of the brain. Some singular phenomena are described with extreme detail, such as inverted vision, facilitation, influence of stimulus intensity, delocalization of colors, reversal of motion, and orientation disorder, among others. Once the author finished his studies of medicine, he completed his training in neurology at the University of Vienna (1933-34) and in brain pathology at the University of Frankfurt (1934-35). The research described here began in the middle of the Spanish Civil War (1936-1939) at a brain injury center in Valencia (Spain), and was later continued at the Ramón y Cajal Institute and at the Spanish National Research Council in Madrid. From the study of brain-injured patients with unilateral lesion in an association area in the left parieto-occipital cortex, equidistant from the visual, tactile and auditory primary areas, the author characterized a multisensory, bilateral and symmetrical disorder that he called central syndrome. This is a multisensory (visual, tactile, auditory) alteration with the lesion not involving the specific areas, all functions being affected, from simple excitability to more complex functions, bilaterally and symmetrically, all of which being incompatible with the rigid traditional theory of brain localization. A phenomenon of clear dynamic character, which depends on the intensity of the stimulus, is the separation or disaggregation of a sensory function into partial functions or qualities that are united in normal perception. Different qualities are gradually lost according to their demands of nervous excitability when the intensity of the stimulus decreases, thus revealing the different functions that make up the sensorium, including visual image orientation as an unexpected function. Thus, inverted or tilted vision appears, among other disorders. The first in-depth study of tilted or inverted vision is part of the present research (pages 142-185). A related dynamic phenomenon is partial disappearance of the disorders by intensification of the stimulus, or by the striking phenomenon of facilitation according to which the perception of a stimulus improves by the presence of another stimulus of the same or of a different sensory modality (cross-modal effect), or by a motor stimulus,

Clinical Neurophysiology, 2002

Brain Research Reviews, 1996

The progress made in understanding the insula in the decade following an earlier review (Augustine, Neurol. Res., 7 (1985) 2-10) is examined in this review. In these ten years, connections have been described between the insula and the orbital cortex, frontal operculum, lateral premotor cortex, ventral granular cortex, and medial area 6 in the frontal lobe. Insular connections between the second somatosensory area and retroinsular area of the parietal lobe have been documented. The insula was found to connect with the temporal pole and the superior temporal sulcus of the temporal lobe. It has an abundance of local intrainsular connections and projections to subdivisions of the cingulate gyms. The insula has connections with the lateral, lateral basal, central, cortical and medial amygdaloid nuclei. It also connects with nonamygdaloid areas such as the perirhinal cortex, entorhinal, and periamygdaloid cortex. The thalamic taste area, the parvicellular part of the ventral posteromedial nucleus, projects fibers to the ipsilateral insular-opercular cortex. In the past decade, confirmation has been given to the insula as a visceral sensory area, visceral motor area, motor association area, vestibular area, and language area. Recent studies have expanded the role of the insula as a somatosensory area, emphasizing its multifaceted, sensory role. The idea of the insula as limbic integration cortex has been affirmed and its role in Alzheimer's disease suggested.

Neuroscience Letters, 2009

The human insular cortex is involved in a wide range of functions including motor control, language, and homeostatic regulation. Little is known, however, how these functions are topographically organized in the insular cortex and how they are functionally related to the amygdala, which is anatomically connected to the insular cortex. We have investigated these questions by conducting an activation likelihood estimate (ALE) meta-analysis of previously published neuroimaging studies reporting insula effects. We find auditory and language tasks to preferentially activate an area in the dorsal part of the anterior insular cortex (AIC). Motor tasks involving both the upper and lower extremity reproducibly activated a posterior AIC region, adjacent to the sulcus centralis insulae (SCI). Significant co-activation with the probabilistically defined amygdala was located in the ventral AIC where also responses related to peripheral physiological changes were repeatedly reported. These findings show that the human AIC is a functionally differentiated brain region. The dorsal region of the AIC may be involved in auditory-motor integration, while the ventral part of the AIC may interface the amygdala with insular regions involved in the regulation of physiological changes related to emotional states. Thus, the present findings provide insights into the organization of human AIC and a methodological approach that may be further used to refine the emerging functional map of the insular cortex.

Gyrus, 2015

Philosophical Transactions of The Royal Society B Biological Sciences

High-resolution MRI of the brain has made it possible to identify focal cortical dysplasia (FCD) in an increasing number of patients. There is evidence for structural abnormalities extending beyond the visually identified FCD lesion. Voxel-based morphometry (VBM) has the potential of detecting both lesions and extra-lesional abnormalities because it performs a whole brain voxel-wise comparison. However, on T1-weighted MRI, FCD lesions are characterized by a wide spectrum of signal hyperintensity that may compromise the results of the segmentation step in VBM. Our purpose was to investigate grey matter (GM) changes in individual FCD patients using voxel-based morphometry (VBM). In addition, we sought to assess the performance of this technique for FCD detection with respect to lesion intensity using an operator designed to emphasize areas of hyperintense T1 signal. We studied 27 patients with known FCD and focal epilepsy, and 39 healthy controls. We compared the GM map of each subject (controls and patients) with the average GM map of all controls and obtained a GM z-score map for each individual. The protocol being designed to achieve a maximal specificity, no differences in GM concentration were found in the control group. The z-score maps showed an increase in GM that coincided with the lesion in 21/27 (78%) patients. Five of the six remaining patients whose lesions were not detected by VBM, presented with a strong lesion hyperintensity and a significant part of their lesion was misclassified as white matter. In 16/27 (59%) patients, there were additional areas of GM increase distant from the primary lesion. Areas of GM decrease were found in 8/27 (30%) patients. In conclusion, individual voxel-based analysis was able to detect FCD in a majority of patients. Moreover, FCD was often associated with widespread GM changes extending beyond the visible lesion. In its current form, however, individual VBM may be unable to detect lesions characterized by strong signal intensity abnormalities.