Morphometry of human insular cortex and insular volume reduction in Williams syndrome

Magnetic resonance-guided laser interstitial thermal therapy for the treatment of non-lesional insular epilepsy in pediatric patients: thermal dynamic and volumetric factors influencing seizure outcomes

PURPOSE

To investigate the safety and efficacy of stereoelectroencephalography (sEEG) directed magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in medically refractory insular epilepsy in pediatric patients, define the relationship between ablation volumes and seizure control, and analyze the relationship between thermal energy and ablation volumes.

METHODS

A single-institution, retrospective review of pediatric patients with insular epilepsy who underwent sEEG directed MRgLITT over a 10-month period was performed. Perioperative, imaging, and outcome data were analyzed. Seizure outcomes were determined based on Engel score (Engel I versus Engel II-IV). Insula and ablation volumes were measured, and the proportion of insula volume ablated was calculated. Thermal energy was calculated in joules.

RESULTS

Four patients underwent sEEG directed MRgLITT of insular epileptogenic foci. The ablation volume was higher in patients with Engel I outcome (3.93 cm³) compared to Engel II-IV outcome (1.02 cm³). The proportion of ablation to insula volume was lowest in patients with Engel II-IV outcome (25.09%). The mean energy requirement to create a unit volume of ablation in the insula is 1205.86 J. A linear trend was noted between thermal ablation energy and ablation volume (R² = 0.884). Over a mean follow-up period of 104 days, three patients were seizure-free (Engel I), and one patient saw significant improvement in seizure frequency (Engel III).

CONCLUSIONS

The proportion of insula ablated, as well as the volume of ablation, are related to seizure outcome with increasing ablation volumes corresponding to improved seizure control. Further analysis of insula laser ablation thermal dynamics and volumes is needed.

Altered Anterior Insular Asymmetry in Pre-teen and Adolescent Youth with Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is hallmarked by social-emotional reciprocity deficits. Social-emotional responding requires the clear recognition of social cues as well as the internal monitoring of emotional salience. Insular cortex is central to the salience network, and plays a key role in approach-avoidance emotional valuation. Consistent right anterior insular hypoactivity and variable volumetric differences of insular cortical volumes were shown previously. The current study analyzed anterior and posterior insular volume/asymmetry changes in ASD across age. Age was used as an additional grouping variable as previous studies indicated differential regional volume in ASD individuals before and after puberty onset. In the current sample, pre-teen ASD expressed left lateralized anterior insula, while adolescent ASD had right lateralization. Typically developing (TD) individuals expressed the opposite lateralization of anterior insula in both age-groups (right greater than left anterior insular volume among pre-teen TD and left greater than right anterior insular volume among adolescent TD). Social-emotional calibrated severity scores from the ADOS were positively correlated with leftward anterior insular asymmetry and negatively correlated with proportional right anterior insular volumes in ASD. Insular cortex has a lateralized role in autonomic nervous system regulation (parasympathetic control in the left, sympathetic control in the right). Atypical insular asymmetry in ASD may contribute to the development of networks with a diminished salience signal to human faces and voices, and may lead to more learned passive avoidant responses to such stimuli at younger ages, leading to more distressed responses in adolescence. Data here supports the use of early behavioral intervention to increase awareness of and reward for social-emotional cues.

The Corticocortical Structural Connectivity of the Human Insula

The insula is a complex structure involved in a wide range of functions. Tracing studies on nonhuman primates reveal a wide array of cortical connections in the frontal (orbitofrontal and prefrontal cortices, cingulate areas and supplementary motor area), parietal (primary and secondary somatosensory cortices) and temporal (temporal pole, auditory, prorhinal and entorhinal cortices) lobes. However, recent human tractography studies have not observed connections between the insula and the cingulate cortices, although these structures are thought to be functionally intimately connected. In this work, we try to unravel the structural connectivity between these regions and other known functionally connected structures, benefiting from a higher number of subjects and the latest state-of-the-art high angular resolution diffusion imaging (HARDI) tractography algorithms with anatomical priors. By performing an HARDI tractography analysis on 46 young normal adults, our study reveals a wide array of connections between the insula and the frontal, temporal, parietal and occipital lobes as well as limbic regions, with a rostro-caudal organization in line with tracing studies in macaques. Notably, we reveal for the first time in humans a clear structural connectivity between the insula and the cingulate, parahippocampal, supramarginal and angular gyri as well as the precuneus and occipital regions.

Reduced anterior insula, enlarged amygdala in alcoholism and associated depleted von Economo neurons

The insula, a structure involved in higher order representation of interoceptive states, has recently been implicated in drug craving and social stress. Here, we performed brain magnetic resonance imaging to measure volumes of the insula and amygdala, a structure with reciprocal insular connections, in 26 alcohol-dependent patients and 24 healthy volunteers (aged 22-56 years, nine females in each group). We used an established morphometry method to quantify total and regional insular volumes. Volumetric measurements of the amygdala were obtained using a model-based segmentation/registration tool. In alcohol-dependent patients, anterior insula volumes were bilaterally reduced compared to healthy volunteers (left by 10%, right by 11%, normalized to total brain volumes). Furthermore, alcohol-dependent patients, compared with healthy volunteers, had bilaterally increased amygdala volumes. The left amygdala was increased by 28% and the right by 29%, normalized to total brain volumes. Post-mortem studies of the anterior insula showed that the reduced anterior insular volume may be associated with a population of von Economo neurons, which were 60% diminished in subjects with a history of alcoholism (n = 6) as compared to subjects without a history of alcoholism (n = 6) (aged 32-56 years, all males). The pattern of neuroanatomical change observed in our alcohol-dependent patients might result in a loss of top-down control of amygdala function, potentially contributing to impaired social cognition as well as an inability to control negatively reinforced alcohol seeking and use.

Fetal MRI insular cortical morphometry and its association with neurobehavior in late-onset small-for-gestational-age fetuses

OBJECTIVE

To evaluate insular cortical morphometry assessed by magnetic resonance imaging (MRI) in late-onset small-for-gestational-age (SGA) fetuses compared with controls, and its association with neurobehavioral outcomes.

METHODS

MRI was performed in 65 late-onset SGA and 59 normally-grown fetuses at 37 weeks' gestation. T2-weighted half Fourier acquisition single-shot turbo spin echo (HASTE) anatomical and diffusion-weighted images were acquired. Insular cortical thickness, volume and fractional anisotropy values were assessed, and asymmetry indices were constructed. At 42 weeks of age, a Neonatal Behavioral Assessment Scale (NBAS) test was performed on the SGA neonates.

RESULTS

Late-onset SGA fetuses had significantly thinner insular cortical thickness and smaller insular cortical volume than did controls. SGA fetuses also presented a more pronounced left asymmetry in the posterior cortex and significantly lower fractional anisotropy values in the left insula. Insular measurements in the SGA group were significantly correlated with neurobehavior as assessed by NBAS scores.

CONCLUSIONS

Insular cortical morphometry was significantly different in late-onset SGA fetuses and correlated with poorer neurobehavioral performance. These data support the impact of growth restriction on brain development and the potential value of cortical assessment as a biomarker of neurodevelopment in at-risk fetuses.

Prior fear conditioning and reward learning interact in fear and reward networks

The ability to flexibly adapt responses to changes in the environment is important for survival. Previous research in humans separately examined the mechanisms underlying acquisition and extinction of aversive and appetitive conditioned responses. It is yet unclear how aversive and appetitive learning interact on a neural level during counterconditioning in humans. This functional magnetic resonance imaging (fMRI) study investigated the interaction of fear conditioning and subsequent reward learning. In the first phase (fear acquisition), images predicted aversive electric shocks or no aversive outcome. In the second phase (counterconditioning), half of the CS+ and CS− were associated with monetary reward in the absence of electric stimulation. The third phase initiated reinstatement of fear through presentation of electric shocks, followed by CS presentation in the absence of shock or reward. Results indicate that participants were impaired at learning the reward contingencies for stimuli previously associated with shock. In the counterconditioning phase, prior fear association interacted with reward representation in the amygdala, where activation was decreased for rewarded compared to unrewarded CS− trials, while there was no reward-related difference in CS+ trials. In the reinstatement phase, an interaction of previous fear association and previous reward status was observed in a reward network consisting of substantia nigra/ventral tegmental area (SN/VTA), striatum and orbitofrontal cortex (OFC), where activation was increased by previous reward association only for CS− but not for CS+ trials. These findings suggest that during counterconditioning, prior fear conditioning interferes with reward learning, subsequently leading to lower activation of the reward network.

Structural asymmetry of anterior insula: behavioral correlates and individual differences

The current study investigated behavioral correlates of structural asymmetry of the insula, and traditional perisylvian language regions, in a large sample of young adults (N=200). The findings indicated (1) reliable leftward surface area asymmetry of the anterior insula, (2) association of this asymmetry with divided visual field lateralization of visual word recognition, and (3) modulation of the correlation of structural and linguistic asymmetry by consistency of hand preference. Although leftward asymmetry of cortical surface area was observed for the anterior insula, pars opercularis and triangularis, and planum temporale, only the anterior insula asymmetry was associated with lateralized word recognition. We interpret these findings within the context of recent structural and functional findings about the human insula. We suggest that leftward structural lateralization of earlier developing insular cortex may bootstrap asymmetrical functional lateralization even if the insula is only a minor component of the adult language network.

Altered microstructure within social-cognitive brain networks during childhood in Williams syndrome

Williams syndrome (WS) is a neurodevelopmental condition caused by a hemizygous deletion of ∼26-28 genes on chromosome 7q11.23. WS is associated with a distinctive pattern of social cognition. Accordingly, neuroimaging studies show that WS is associated with structural alterations of key brain regions involved in social cognition during adulthood. However, very little is currently known regarding the neuroanatomical structure of social cognitive brain networks during childhood in WS. This study used diffusion tensor imaging to investigate the structural integrity of a specific set of white matter pathways (inferior fronto-occipital fasciculus [IFOF] and uncinate fasciculus [UF]) and associated brain regions [fusiform gyrus (FG), amygdala, hippocampus, medial orbitofrontal gyrus (MOG)] known to be involved in social cognition in children with WS and a typically developing (TD) control group. Children with WS exhibited higher fractional anisotropy (FA) and axial diffusivity values and lower radial diffusivity and apparent diffusion coefficient (ADC) values within the IFOF and UF, higher FA values within the FG, amygdala, and hippocampus and lower ADC values within the FG and MOG compared to controls. These findings provide evidence that the WS genetic deletion affects the development of key white matter pathways and brain regions important for social cognition.

Insular cortex abnormalities in psychotic major depression: relationship to gender and psychotic symptoms

Recent data suggests that psychotic major depression (PMD) may be a discrete disorder distinguishable from nonpsychotic major depression (NPMD), and that patients with PMD may be more similar to individuals with schizophrenia than individuals with NPMD. The insula is a brain region in which morphometric changes have been associated with psychotic symptom severity in schizophrenia and affective psychosis. It was hypothesized that insular volumes would be reduced in PMD compared to NPMD and controls, and insular volumes would correlate with psychosis but not depression severity. Insular gray matter volumes were measured in PMD and NPMD patients and matched healthy controls using magnetic resonance images and manual morphometry. Clinical measures of illness severity were obtained to determine their relationship with insular volume. Posterior insular volumes were significantly reduced in PMD compared to HC. There were also significant group-by-gender interactions for total, anterior and posterior insular volumes. Using Pearson product-moment correlations, anterior insular volumes did not correlate with depression severity. Left anterior insular volume was significantly correlated with total and positive symptom psychosis severity in the PMD group. Atypical insular morphometry may be related to the inability to distinguish between internally and externally generated sensory inputs characteristic of psychosis.

The regulatory function of social referencing in preschoolers with Down syndrome or Williams syndrome

BACKGROUND

An important developmental task is to learn to recognize another person as a source of information and to utilize this information as a method of learning about the surrounding world. This socially guided form of learning, referred to as social referencing, is critical for the development of children's understanding of other people, themselves and their surrounding world. In the present project, the regulatory function of social referencing was examined in two genetic disorders that are characterized by differing patterns of socio-cognitive development: Down syndrome (DS) and Williams syndrome (WS).

METHODS

Participants were 20 children with DS and 20 children with WS aged 42 to 71 months, matched on chronological age and gender. Each child participated in four studies: one study in which we examined performance in a social referencing paradigm and three studies in which we considered performance on tasks designed to tap each of three component abilities (initiating eye contact, gaze following and emotional responsivity) important for success in social referencing.

RESULTS

The majority of children in both groups demonstrated positive behavioral responses regarding the stimulus in the Social Referencing task when the adult communicated a joyful message but did not regulate their own behavior in accordance with the adult's expression of fear. Between-group differences were observed in both conditions, with most differences indicating more advanced socio-communicative competence for children with DS than for children with WS even though the overall intellectual abilities and receptive language abilities of the children with WS were significantly higher than were those of the children with DS. The results of follow-up studies indicated that children with DS were more likely to initiate eye contact (unsolicited) and to follow another person's gaze in triadic situations than were children with WS. Neither group regulated their behavior in response to expressions of fear.

CONCLUSIONS

These findings provide new insight into the development of the social cognitive phenotypes associated with DS and WS. These social cognitive differences found during the preschool years likely contribute to the differing phenotypes observed later in life between individuals with DS and individuals with WS.

Reduced insular volume in attention deficit hyperactivity disorder

The aim of this study was to evaluate whether structural differences in the insula and anterior cingulate cortex (ACC), two critical areas of the "salience network," co-exist in adolescents with attention deficit hyperactivity disorder (ADHD) compared with healthy controls (HC). In addition we aimed to determine if structural changes within these regions correlate with attention and inhibitory function. Nineteen adolescents with ADHD and 25 HC received MRI scans on a 3T magnet. Morphometric analysis was performed with FreeSurfer. Youths with ADHD were found to have a bilateral reduction in anterior insular (AIC) gray matter volumes compared to HC. Furthermore, the left AIC was found to positively correlate with oppositional symptoms, while the right AIC was found to associate with both attention problems and inhibition. To our knowledge this is the first report of a bilateral reduction in AIC volumes in ADHD. Our findings suggest a role for the insula in modulating attention and inhibitory capacity in ADHD.

Neural network development in late adolescents during observation of risk-taking action

Emotional maturity and social awareness are important for adolescents, particularly college students beginning to face the challenges and risks of the adult world. However, there has been relatively little research into personality maturation and psychological development during late adolescence and the neural changes underlying this development. We investigated the correlation between psychological properties (neuroticism, extraversion, anxiety, and depression) and age among late adolescents (n = 25, from 18 years and 1 month to 22 years and 8 months). The results revealed that late adolescents became less neurotic, less anxious, less depressive and more extraverted as they aged. Participants then observed video clips depicting hand movements with and without a risk of harm (risk-taking or safe actions) during functional magnetic resonance imaging (fMRI). The results revealed that risk-taking actions elicited significantly stronger activation in the bilateral inferior parietal lobule, temporal visual regions (superior/middle temporal areas), and parieto-occipital visual areas (cuneus, middle occipital gyri, precuneus). We found positive correlations of age and extraversion with neural activation in the insula, middle temporal gyrus, lingual gyrus, and precuneus. We also found a negative correlation of age and anxiety with activation in the angular gyrus, precentral gyrus, and red nucleus/substantia nigra. Moreover, we found that insula activation mediated the relationship between age and extraversion. Overall, our results indicate that late adolescents become less anxious and more extraverted with age, a process involving functional neural changes in brain networks related to social cognition and emotional processing. The possible neural mechanisms of psychological and social maturation during late adolescence are discussed.

Effect of nonrigid registration algorithms on deformation-based morphometry: a comparative study with control and Williams syndrome subjects

Deformation-based morphometry (DBM) is a widely used method for characterizing anatomical differences across groups. DBM is based on the analysis of the deformation fields generated by nonrigid registration algorithms, which warp the individual volumes to a DBM atlas. Although several studies have compared nonrigid registration algorithms for segmentation tasks, few studies have compared the effect of the registration algorithms on group differences that may be uncovered through DBM. In this study, we compared group atlas creation and DBM results obtained with five well-established nonrigid registration algorithms using 13 subjects with Williams syndrome and 13 normal control subjects. The five nonrigid registration algorithms include the following: (1) the adaptive bases algorithm, (2) the image registration toolkit, (3) The FSL nonlinear image registration tool, (4) the automatic registration tool, and (5) the normalization algorithm available in Statistical Parametric Mapping (SPM8). Results indicate that the choice of algorithm has little effect on the creation of group atlases. However, regions of differences between groups detected with DBM vary from algorithm to algorithm both qualitatively and quantitatively. Some regions are detected by several algorithms, but their extent varies. Others are detected only by a subset of the algorithms. Based on these results, we recommend using more than one algorithm when performing DBM studies.

The Williams syndrome chromosome 7q11.23 hemideletion confers hypersocial, anxious personality coupled with altered insula structure and function

Although it is widely accepted that genes can influence complex behavioral traits such as human temperament, the underlying neurogenetic mechanisms remain unclear. Williams syndrome (WS), a rare disorder caused by a hemizygous deletion on chromosome 7q11.23, including genes important for neuronal migration and maturation (LIMK1 and CLIP2), is typified by a remarkable hypersocial but anxious personality and offers a unique opportunity to investigate this open issue. Based on the documented role of the insula in mediating emotional response tendencies and personality, we used multimodal imaging to characterize this region in WS and found convergent anomalies: an overall decrease in dorsal anterior insula (AI) gray-matter volume along with locally increased volume in the right ventral AI; compromised white-matter integrity of the uncinate fasciculus connecting the insula with the amygdala and orbitofrontal cortex; altered regional cerebral blood flow in a pattern reminiscent of the observed gray-matter alterations (i.e., widespread reductions in dorsal AI accompanied by locally increased regional cerebral blood flow in the right ventral AI); and disturbed neurofunctional interactions between the AI and limbic regions. Moreover, these genetically determined alterations of AI structure and function predicted the degree to which the atypical WS personality profile was expressed in participants with the syndrome. The AI's rich anatomical connectivity, its transmodal properties, and its involvement in the behaviors affected in WS make the observed genetically determined insular circuitry perturbations and their association with WS personality a striking demonstration of the means by which neural systems can serve as the interface between genetic variability and alterations in complex behavioral traits.

Regional brain differences in cortical thickness, surface area and subcortical volume in individuals with Williams syndrome

Williams syndrome (WS) is a rare genetic neurodevelopmental disorder characterized by increased non-social anxiety, sensitivity to sounds and hypersociability. Previous studies have reported contradictory findings with regard to regional brain variation in WS, relying on only one type of morphological measure (usually volume) in each study. The present study aims to contribute to this body of literature and perhaps elucidate some of these discrepancies by examining concurrent measures of cortical thickness, surface area and subcortical volume between WS subjects and typically-developing (TD) controls. High resolution MRI scans were obtained on 31 WS subjects and 50 typically developing control subjects. We derived quantitative regional estimates of cortical thickness, cortical surface area, and subcortical volume using FreeSurfer software. We evaluated between-group ROI differences while controlling for total intracranial volume. In post-hoc exploratory analyses within the WS group, we tested for correlations between regional brain variation and Beck Anxiety Inventory scores. Consistent with our hypothesis, we detected complex patterns of between-group cortical variation, which included lower surface area in combination with greater thickness in the following cortical regions: post central gyrus, cuneus, lateral orbitofrontal cortex and lingual gyrus. Additional cortical regions showed between-group differences in one (but not both) morphological measures. Subcortical volume was lower in the basal ganglia and the hippocampus in WS versus TD controls. Exploratory correlations revealed that anxiety scores were negatively correlated with gray matter surface area in insula, OFC, rostral middle frontal, superior temporal and lingual gyrus. Our results were consistent with previous reports showing structural alterations in regions supporting the socio-affective and visuospatial impairments in WS. However, we also were able to effectively capture novel and complex patterns of cortical differences using both surface area and thickness. In addition, correlation results implicate specific brain regions in levels of anxiety in WS, consistent with previous reports investigating general anxiety disorders in the general population.

The variation of function across the human insula mirrors its patterns of structural connectivity: evidence from in vivo probabilistic tractography

The human insula is a functionally complex yet poorly understood region of the cortex, implicated in a wide range of cognitive, motor, emotion and somatosensory activity. To elucidate the functional role of the insula, the current study used in vivo probabilistic tractography to map the structural connectivity of seven anatomically-defined insular subregions. The connectivity patterns identified reveal two complementary insular networks connected via a dual route architecture, and provide key insights about the neural basis of the numerous functions ascribed to this area. Specifically, anterior-most insular regions were associated with a ventrally-based network involving orbital/inferior frontal and anterior/polar temporal regions, forming part of a key emotional salience and cognitive control network associated with the implementation of goal-directed behavior. The posterior and dorsal-middle insular regions were associated with a network focused on posterior and (to a lesser extent) anterior temporal regions via both dorsal and ventral pathways. This is consistent with the involvement of the insula in sound-to-speech transformations, with an implicated role in the temporal resolution, sequencing, and feedback processes crucial for auditory and motor processing, and the monitoring and adjustment of expressive performance.

Emotion regulation and brain plasticity: expressive suppression use predicts anterior insula volume

Expressive suppression is an emotion regulation strategy that requires interoceptive and emotional awareness. These processes both recruit the anterior insula. It is not known, however, whether increased use of expressive suppression is associated with increased anterior insula volume. In the present study, high-resolution anatomical MRI images were used to calculate insula volumes in a set of 50 healthy female subjects (mean 21.9 years) using both region of interest (ROI) and voxel-based morphometry (VBM) approaches. Participants also completed trait measures of expressive suppression usage, cognitive reappraisal usage, and negative emotional reactivity (the latter two served as control measures). As predicted, both ROI and VBM methods found that expressive suppression usage, but not negative affect and cognitive reappraisal, was positively related to anterior insula volume. These findings are consistent with the idea that trait patterns of emotion processing are related to brain structure.

Insular volume reduction in fragile X syndrome

Fragile X syndrome (FraX) is the most common form of inherited mental deficit and is caused by mutations of the Fragile X Mental Retardation 1 (FMR1) gene on the X chromosome. While males and females with the full FMR1 mutation are affected differently because the disorder is X-linked, both suffer from varying degrees of cognitive impairment, attention deficits and social anxiety. The insula is a sensory integrative region that has been increasingly suggested as a critical area involved in anxiety manifestation. The current study was designed to examine possible changes in insular volume in FraX compared to age- and gender-matched typically developing healthy controls (HC) as well as age-, gender-, and intelligence-matched developmentally delayed controls (DD). An established native-space, manual morphometry method was utilized to quantify total and regional insular volumes using structural magnetic resonance imaging. Total, anterior and posterior insular volumes were found to be reduced in FraX compared to both HC and DD. The current data add to a growing literature concerning brain abnormalities in FraX and suggests that significant volume reduction of the insula is a component of the FraX neuroanatomical phenotype. This finding also provides an intriguing potential neural correlate for hyperarousal and gaze aversion, which are prominent behavioral symptoms of FraX.