Parietal Operculum Research Articles

Supraspinal Control of Urine Storage and Micturition in Men--An fMRI Study.

Despite the crucial role of the brain in the control of the human lower urinary tract, little is known about the supraspinal mechanisms regulating micturition. To investigate the central regulatory mechanisms activated during micturition initiation and actual micturition, we used an alternating sequence of micturition imitation/imagination, micturition initiation, and actual micturition in 22 healthy males undergoing functional magnetic resonance imaging. Subjects able to micturate (voiders) showed the most prominent supraspinal activity during the final phase of micturition initiation whereas actual micturition was associated with significantly less such activity. Initiation of micturition in voiders induced significant activity in the brainstem (periaqueductal gray, pons), insula, thalamus, prefrontal cortex, parietal operculum and cingulate cortex with significant functional connectivity between the forebrain and parietal operculum. Subjects unable to micturate (nonvoiders) showed less robust activation during initiation of micturition, with activity in the forebrain and brainstem particularly lacking. Our findings suggest that micturition is controlled by a specific supraspinal network which is essential for the voluntary initiation of micturition. Once this network triggers the bulbospinal micturition reflex via brainstem centers, micturition continues automatically without further supraspinal input. Unsuccessful micturition is characterized by a failure to activate the periaqueductal gray and pons during initiation.

Parietal and premotor cortices: Activation reflects imitation accuracy during observation, delayed imitation and concurrent imitation

This study investigated whether activation within areas belonging to the action observation and imitation network reveals a linear relation to the subsequent accuracy of imitating a bimanual rhythmic movement measured via a motion capturing system. 20 participants were scanned with functional magnetic resonance imaging (fMRI) when asked to imitate observed bimanual movements either concurrently versus with a delay (2s) or simply to observe the movements without imitation. Results showed that action observation relates to activation within classic mirror-related areas. Activation patterns were more widespread when participants were asked to imitate the movement. During observation with concurrent imitation, activation in the left inferior parietal lobe (IPL) was associated negatively with imitation accuracy. During observation in the delayed imitation condition, higher subsequent imitation accuracy was coupled with higher activation in the right superior parietal lobe (SPL) and the left parietal operculum (POp). During the delayed imitation itself, a negative association between imitation accuracy and brain activation was revealed in the right ventral premotor cortex (vPMC). We conclude that the IPL is involved in online comparison and visuospatial attention processes during imitation, the SPL provides a kinesthetic blueprint during movement observation, the POp preserves body identity, and the vPMC recruits motor representations—especially when no concurrent visual guidance is possible.

Michael Langman

Neural plasticity induced by stroke can mediate positive outcomes, such as recovery of function, but can also result in the formation of abnormal connections with negative consequences for perception and...

P442: The value of SSR recordings in the assessment of autonomic nervous dysfunction in patients with sacral-pudendal impairment

P442: The value of SSR recordings in the assessment of autonomic nervous dysfunction in patients with sacral-pudendal impairment

Imaging the where and when of tic generation and resting state networks in adult Tourette patients.

Introduction: Tourette syndrome (TS) is a neuropsychiatric disorder with the core phenomenon of tics, whose origin and temporal pattern are unclear. We investigated the When and Where of tic generation and resting state networks (RSNs) via functional magnetic resonance imaging (fMRI).Methods: Tic-related activity and the underlying RSNs in adult TS were studied within one fMRI session. Participants were instructed to lie in the scanner and to let tics occur freely. Tic onset times, as determined by video-observance were used as regressors and added to preceding time-bins of 1 s duration each to detect prior activation. RSN were identified by independent component analysis (ICA) and correlated to disease severity by the means of dual regression.Results: Two seconds before a tic, the supplementary motor area (SMA), ventral primary motor cortex, primary sensorimotor cortex and parietal operculum exhibited activation; 1 s before a tic, the anterior cingulate, putamen, insula, amygdala, cerebellum and the extrastriatal-visual cortex exhibited activation; with tic-onset, the thalamus, central operculum, primary motor and somatosensory cortices exhibited activation. Analysis of resting state data resulted in 21 components including the so-called default-mode network. Network strength in those regions in SMA of two premotor ICA maps that were also active prior to tic occurrence, correlated significantly with disease severity according to the Yale Global Tic Severity Scale (YGTTS) scores.Discussion: We demonstrate that the temporal pattern of tic generation follows the cortico-striato-thalamo-cortical circuit, and that cortical structures precede subcortical activation. The analysis of spontaneous fluctuations highlights the role of cortical premotor structures. Our study corroborates the notion of TS as a network disorder in which abnormal RSN activity might contribute to the generation of tics in SMA.

Spatio-temporal correlates of taste processing in the human primary gustatory cortex

In humans the identification of the primary gustatory cortex (PGC) is still under debate. Neuroimaging studies indicate insula and overlying opercula as the best candidates but the exact position of the PGC within this region is not entirely clear. Moreover, inconsistencies appear when comparing results from studies using functional magnetic resonance imaging (fMRI), and gustatory event-related potentials (gERP), or gustatory event-related magnetic fields (gERMF). fMRI indicates activations in the anterior part of the insula and frontal operculum, while gERP and/or gERMF indicate activations at the transition between the parietal operculum and insula in its posterior part. Here it is important to note that for gERP and gERMF temporal and spatial characteristics of the stimulus must be well controlled to evoke a useful brain response. In the present study gERMF and gERP were recorded simultaneously using a whole-head system with 249 magnetometers and 32 electrodes, respectively; taste stimuli were applied using a stimulator providing excellent temporal and spatial control of the stimulus. Separate ERP and ERMF averaged waveforms were derived time-locked to the onset of the taste stimuli. The source analysis for the early time range revealed activity in the left and right anterior and mid part of the insula, where in the later time range the sources were located more in the posterior part of the insula.

Different localizations underlying cortical gelastic epilepsy: Case series and review of literature

BackgroundGelastic seizures (GS) are classically observed with hypothalamic hamartomas but they can also be associated with cortical epileptogenic foci. ObjectiveTo study the different cortical localizations associated with GS. MethodsWe reviewed the data from all patients with cortical GS investigated in our epilepsy unit from 1974 to 2012 and in the literature from 1956 to 2013. ResultsSixteen cases were identified in our database and 77 in the literature. Investigations provided confident focus localization in 9 and 18, respectively. In our series, the identified foci were located in the mesial temporal structures (2 left, 1 right), lateral temporal cortex (1 right), superior frontal gyrus (1 left), and operculoinsular region [3 right (orbitofrontal or frontal operculum extending into the anterior insula) and 1 left (frontal operculum extending into the anterior insula)]. In the literature, the identified foci (13 right/5 left) were located in the temporal lobe of 4 (1 right inferior, 1 right medial and inferior, 1 right posterior middle, inferior extending posteriorly to the lingual gyrus, and 1 left middle, inferior, and medial), in the frontal lobe of 12 [10 (6 right/4 left) medial (i.e., superior, medial frontal, and/or anterior cingulate gyri), 1 lateral (right anterior inferior frontal gyrus), and 1 right medioposterior orbitofrontal cortex] and in the parietal lobe of 2 (1 left superior parietal lobule and 1 right parietal operculum) patients. ConclusionIctal laughter is a poorly lateralizing and localizing feature as it may be encountered in patients with a focus in the left or right frontal, temporal, parietal, or insular lobe.

Ear acupuncture and fMRI: a pilot study for assessing the specificity of auricular points.

In recent years research explored different acupuncture stimulation techniques but interest has focused primarily on somatic acupuncture and on a limited number of acupoints. As regards ear Acupuncture (EA) there is still some criticism about the clinical specificity of auricular points/areas representing organs or structures of the body. The aim of this study was to verify through (Functional magnetic resonance imaging) fMRI the hypothesis of EA point specificity using two auricular points having different topographical locations and clinical significance. Six healthy volunteers underwent two experimental fMRI sessions: the first was dedicated to the stimulation of Thumb Auricular Acupoint (TAA) and the second to the stimulation of Brain Stem Auricular Acupoint (BSAA). The stimulation of the needle placed in the TAA of the left ear produced an increase in activation bilaterally in the parietal operculum, region of the secondary somatosensory area SII. Stimulation of the needle placed in the BSAA of the left ear showed a pattern that largely overlapped regions belonging to the pain matrix, as shown to be involved in previous somatic acupuncture studies but with local differences in the left amygdala, anterior cingulate cortex, and cerebellum. The differences in activation patterns between TAA and BSAA stimulation support the specificity of the two acupoints. Moreover, the peculiarity of the regions involved in BSAA stimulation compared to those involved in the pain matrix, is in accordance with the therapeutic indications of this acupoint that include head pain, dizziness and vertigo. Our results provide preliminary evidence on the specificity of two auricular acupoints; further research is warranted by means of fMRI both in healthy volunteers and in patients carrying neurological/psychiatric syndromes.

Expert athletes activate somatosensory and motor planning regions of the brain when passively listening to familiar sports sounds

The present functional magnetic resonance imaging study examined the neural response to familiar and unfamiliar, sport and non-sport environmental sounds in expert and novice athletes. Results revealed differential neural responses dependent on sports expertise. Experts had greater neural activation than novices in focal sensorimotor areas such as the supplementary motor area, and pre- and postcentral gyri. Novices showed greater activation than experts in widespread areas involved in perception (i.e. supramarginal, middle occipital, and calcarine gyri; precuneus; inferior and superior parietal lobules), and motor planning and processing (i.e. inferior frontal, middle frontal, and middle temporal gyri). These between-group neural differences also appeared as an expertise effect within specific conditions. Experts showed greater activation than novices during the sport familiar condition in regions responsible for auditory and motor planning, including the inferior frontal gyrus and the parietal operculum. Novices only showed greater activation than experts in the supramarginal gyrus and pons during the non-sport unfamiliar condition, and in the middle frontal gyrus during the sport unfamiliar condition. These results are consistent with the view that expert athletes are attuned to only the most familiar, highly relevant sounds and tune out unfamiliar, irrelevant sounds. Furthermore, these findings that athletes show activation in areas known to be involved in action planning when passively listening to sounds suggests that auditory perception of action can lead to the re-instantiation of neural areas involved in producing these actions, especially if someone has expertise performing the actions.

Representation of Spatial Information in Key Areas of the Descending Pain Modulatory System

Behavioral studies have demonstrated that descending pain modulation can be spatially specific, as is evident in placebo analgesia, which can be limited to the location at which pain relief is expected. This suggests that higher-order cortical structures of the descending pain modulatory system carry spatial information about the site of stimulation. Here, we used functional magnetic resonance imaging and multivariate pattern analysis in 15 healthy human volunteers to test whether spatial information of painful stimuli is represented in areas of the descending pain modulatory system. We show that the site of nociceptive stimulation (arm or leg) can be successfully decoded from local patterns of brain activity during the anticipation and receipt of painful stimulation in the rostral anterior cingulate cortex, the dorsolateral prefrontal cortices, and the contralateral parietal operculum. These results demonstrate that information regarding the site of nociceptive stimulation is represented in these brain regions. Attempts to predict arm and leg stimulation from the periaqueductal gray, control regions (e.g., white matter) or the control time interval in the intertrial phase did not allow for classifications above chance level. This finding represents an important conceptual advance in the understanding of endogenous pain control mechanisms by bridging the gap between previous behavioral and neuroimaging studies, suggesting a spatial specificity of endogenous pain control.

Altered resting state – functional connectivity in patients with bilateral vestibular failure

Background: Patients with bilateral vestibular failure (BVF) suffer from gait unsteadiness and oscillopsia. Brain imaging studies applying vestibular stimulation in patients with BVF have shown altered neural activity of cortical visual-vestibular interaction: decreased bilateral neural activity in the posterior insula and parietal operculum and decreased deactivations in the visual cortex. It is unknown how this affects functional connectivity in the resting brain.

Cortical activation resulting from the stimulation of periodontal mechanoreceptors measured by functional magnetic resonance imaging (fMRI)

To describe the normal cortical projections of periodontal mechanoreceptors. A device using von Frey filaments delivered 1-Hz punctate tactile stimuli to the teeth during fMRI. In a block design paradigm, tooth (T) 11 and T13 were stimulated in ten volunteers and T21 and T23 in ten other subjects. Random-effect group analyses were performed for each tooth, and differences between teeth were examined using ANOVA. The parietal operculum (S2) was activated bilaterally for all teeth; the postcentral gyrus (S1) was activated bilaterally for T21 and T23 and contralaterally for T11 and T13. In the second-level analysis including the four teeth, we found five clusters: bilateral S1 and S2, and left inferior frontal gyrus, with no difference between teeth in somatosensory areas. However, the ANOVA performed on the S1 clusters found separately in each tooth showed that S1 activation was more contralateral for the canines. One-hertz mechanical stimulation activates periodontal mechanoreceptors and elicits bilateral cortical activity in S1 and S2, with a double representation in S2, namely in OP1 and OP4. The cortical somatotopy of periodontal mechanoreceptors is poorly described. These findings may serve as normal reference to further explore the cortical plasticity induced by periodontal or neurological diseases.

Ranking brain areas encoding the perceived level of pain from fMRI data

Pain perception is thought to emerge from the integrated activity of a distributed brain system, but the relative contribution of the different network nodes is still incompletely understood.In the present functional magnetic resonance imaging (fMRI) study, we aimed to identify the more relevant brain regions to explain the time profile of the perceived pain intensity in healthy volunteers, during noxious chemical stimulation (ascorbic acid injection) of the left hand. To this end, we performed multi-way partial least squares regression of fMRI data from twenty-two a-priori defined brain regions of interest (ROI) in each hemisphere, to build a model that could efficiently reproduce the psychophysical pain profiles in the same individuals; moreover, we applied a novel three-way extension of the variable importance in projection (VIP) method to summarize each ROI contribution to the model.Brain regions showing the highest VIP scores included the bilateral mid-cingulate, anterior and posterior insular, and parietal operculum cortices, the contralateral paracentral lobule, bilateral putamen and ipsilateral medial thalamus. Most of these regions, with the exception of medial thalamus, were also identified by a statistical analysis on mean ROI beta values estimated using the time course of the psychophysical rating as a regressor at the voxel level.Our results provide the first rank-ordering of brain regions involved in coding the perceived level of pain. These findings in a model of acute prolonged pain confirm and extend previous data, suggesting that a bilateral array of cortical areas and subcortical structures is involved in pain perception.

Impact of a Single Bout of Aerobic Exercise on Regional Brain Perfusion and Activation Responses in Healthy Young Adults

PurposeDespite the generally accepted view that aerobic exercise can have positive effects on brain health, few studies have measured brain responses to exercise over a short time span. The purpose of this study was to examine the impact within one hour of a single bout of exercise on brain perfusion and neuronal activation.MethodsHealthy adults (n = 16; age range: 20–35 yrs) were scanned using Magnetic Resonance Imaging (MRI) before and after 20 minutes of exercise at 70% of their age-predicted maximal heart rate. Pseudo-continuous arterial spin labeling (pcASL) was used to measure absolute cerebral blood flow (CBF) prior to exercise (pre) and at 10 min (post-10) and 40 min (post-40) post-exercise. Blood oxygenation level dependent (BOLD) functional MRI (fMRI) was performed pre and post-exercise to characterize activation differences related to a go/no-go reaction time task.ResultsCompared to pre-exercise levels, grey matter CBF was 11% (±9%) lower at post-10 (P<0.0004) and not different at post-40 (P = 0.12), while global WM CBF was increased at both time points post-exercise (P<0.0006). Regionally, the hippocampus and insula showed a decrease in perfusion in ROI-analysis at post-10 (P<0.005, FDR corrected), whereas voxel-wise analysis identified elevated perfusion in the left medial postcentral gyrus at post-40 compared to pre (pcorrected = 0.05). BOLD activations were consistent between sessions, however, the left parietal operculum showed reduced BOLD activation after exercise.ConclusionThis study provides preliminary evidence of regionalized brain effects associated with a single bout of aerobic exercise. The observed acute cerebrovascular responses may provide some insight into the brain’s ability to change in relation to chronic interventions.

Altered resting-state functional connectivity in patients with chronic bilateral vestibular failure.

Patients with bilateral vestibular failure (BVF) suffer from gait unsteadiness, oscillopsia and impaired spatial orientation. Brain imaging studies applying caloric irrigation to patients with BVF have shown altered neural activity of cortical visual–vestibular interaction: decreased bilateral neural activity in the posterior insula and parietal operculum and decreased deactivations in the visual cortex. It is unknown how this affects functional connectivity in the resting brain and how changes in connectivity are related to vestibular impairment.We applied a novel data driven approach based on graph theory to investigate altered whole-brain resting-state functional connectivity in BVF patients (n= 22) compared to age- and gender-matched healthy controls (n= 25) using resting-state fMRI. Changes in functional connectivity were related to subjective (vestibular scores) and objective functional parameters of vestibular impairment, specifically, the adaptive changes during active (self-guided) and passive (investigator driven) head impulse test (HIT) which reflects the integrity of the vestibulo-ocular reflex (VOR).BVF patients showed lower bilateral connectivity in the posterior insula and parietal operculum but higher connectivity in the posterior cerebellum compared to controls. Seed-based analysis revealed stronger connectivity from the right posterior insula to the precuneus, anterior insula, anterior cingulate cortex and the middle frontal gyrus. Excitingly, functional connectivity in the supramarginal gyrus (SMG) of the inferior parietal lobe and posterior cerebellum correlated with the increase of VOR gain during active as compared to passive HIT, i.e., the larger the adaptive VOR changes the larger was the increase in regional functional connectivity.Using whole brain resting-state connectivity analysis in BVF patients we show that enduring bilateral deficient or missing vestibular input leads to changes in resting-state connectivity of the brain. These changes in the resting brain are robust and task-independent as they were found in the absence of sensory stimulation and without a region-related a priori hypothesis. Therefore they may indicate a fundamental disease-related change in the resting brain. They may account for the patients' persistent deficits in visuo-spatial attention, spatial orientation and unsteadiness. The relation of increasing connectivity in the inferior parietal lobe, specifically SMG, to improvement of VOR during active head movements reflects cortical plasticity in BVF and may play a clinical role in vestibular rehabilitation.

The Changes of c-Fos Expression by Motor Cortex Stimulation in the Deafferentation Pain Model

The effect of motor cortex stimulation (MCS) therapy for deafferentation pain was evaluated based on c-Fos, a known pain marker. Nineteen mature cats weighing 1.5–3.5 kg were used. Cats were divided into three groups: a deafferentation pain group in which the left trigeminal ganglion was destroyed, an MCS group in which MCS was used following destruction of the trigeminal ganglion, and a control group. Sites and levels of c-Fos expression were examined immunohistochemically. The percentage of c-Fos-positive cells in the left spinal nucleus of the trigeminus, the bilateral insula, and the bilateral operculum increased in both the deafferentation pain and the MCS groups. There were no statistically significant differences between these groups. In the cingulate gyrus, the percentage of c-Fos-positive cells increased bilaterally in the deafferentation pain group and the MCS group, but the increase was greater in the MCS group. The increase in c-Fos-positive cells in the left spinal nucleus of the trigeminus in the deafferentation group may reflect reported electrical hyperactivity. The cingulate gyrus, insula, and parietal operculum were activated after deafferentation. This change (increase in c-Fos positive cells) is related to the development of deafferentation pain. Pain relief due to MCS is not dependent on the suppression of the activated left spinal nucleus of the trigeminus or the descending analgesic mechanism of the brain stem. Activation of the cingulate gyrus appears to be a factor in the analgesic mechanism of MCS.

Neuronal differences between chronic low back pain and depression regarding long‐term habituation to pain

Longitudinal studies of experimental pain are rare and little is known about the differences regarding sensitization and habituation over longer periods in patients with chronic pain or depression compared with controls. We used a standardized longitudinal painful heat paradigm that was designed to induce long-term habituation in 19 patients with chronic low back pain (CLBP), 21 patients with depression (DEP) and 21 healthy participants (controls) over a time course of eight consecutive days. We applied functional magnetic resonance imaging on the first and last day of this period and after 3 months. Although the pain paradigm was standardized, patients with DEP exhibited significantly higher pain thresholds and a trend to higher pain ratings and, in functional imaging, showed less activation of the operculum and the secondary somatosensory cortex (S2) as compared to patients with CLBP and controls. Conversely, patients with CLBP showed increased activation in the anterior insula and parietal operculum as compared to patients with DEP and controls. Within session, all participants sensitized to pain, which was associated with higher activation levels in the thalamus, amygdala, midcingulate cortex, and sensory and motor areas. However, patients with depression showed significantly less activation in midbrain and brainstem areas. Given that pain and depression potentiate each other clinically, our data suggest that this may involve different cortical pain areas.

The utility of magnetoencephalography in the presurgical evaluation of refractory insular epilepsy

To study the utility of magnetoencephalography (MEG) in patients with refractory insular epilepsy. Covered by highly functional temporal, frontal, and parietal opercula, insular-onset seizures can manifest a variety of ictal symptoms falsely leading to a diagnosis of temporal, frontal, or parietal lobe seizures. Lack of recognition of insular seizures may be responsible for some epilepsy surgery failures. We retrospectively reviewed and analyzed MEG data in 14 patients with refractory insular seizures defined through intracranial electroencephalography (EEG) or by the presence of an epileptogenic lesion in the insula with compatible seizure semiology. MEG was performed as part of the noninvasive presurgical evaluation, using a 275-channel whole head MEG system. MEG data were analyzed using a single equivalent current dipole model. MEG localization was compared to interictal positron emission tomography (PET) and ictal single photon emission computed tomography (SPECT) results and to the resection margin. Three patterns of MEG spike sources were observed. Seven patients showed an anterior operculoinsular clusters and two patients had a posterior operculoinsular cluster. No spikes were detected in one patient, and the remaining four patients showed a diffuse perisylvian distribution. Spike sources showed uniform orientation perpendicular to the sylvian fissure. Nine patients proceeded to insular epilepsy surgery with favorable surgical outcome. Among patients with anterior operculoinsular cluster who proceeded to have surgery, MEG provided superior information to ictal SPECT in four of six patients and to interictal PET in five of six patients. MEG is useful in identifying patients who are likely to benefit from epilepsy surgery targeting the insula, particularly if a tight dipole cluster is identified even if other noninvasive modalities fail to produce localizing results.

Haptic Working Memory for Grasping: the Role of the Parietal Operculum

We investigated how haptic information on object geometry is encoded in the parietal operculum (OP) and is used for guiding object-directed motor acts in humans. We tested the effects of conditioning single-pulse transcranial magnetic stimulation (spTMS) applied to the left OP on corticospinal excitability assessed by a test spTMS applied to the ipsilateral motor cortex (M1) 5 ms after conditioning spTMS. Participants explored the size of a graspable object visually or haptically and waited for a go-signal to grasp it in the dark. They received TMS during the delay phase. In a separate group of participants performing the same task, conditioning spTMS was applied to the ventral premotor cortex (vPM) 7 ms before test spTMS. Results showed that conditioning TMS over OP modulated M1 output according to the information on object size that had been acquired haptically but not visually. Vice versa, conditioning TMS over vPM modulated M1 output according to information on object size acquired by vision but not haptically. Moreover spTMS over OP produced a significant modulation of the upcoming reaching behavior only when the object had been explored haptically. We show that OP contains a haptic memory of objects' macrogeometry and the appropriate motor plan for grasping them.

Are visual texture-selective areas recruited during haptic texture discrimination?

Shape and surface texture provide salient cues to object identity, both when objects are explored using vision and via touch (haptics). In vision, shape information is processed within the lateral occipital complex (LOC), while surface texture is selectively processed in medial ventro-temporal cortex, in the collateral sulcus (CoS) and parahippocampul gyrus (pHG). Accumulating evidence indicates that the LOC, despite its location within the ventral visual system, is also consistently recruited during haptic shape processing. Here we used fMRI to examine whether ventral ‘visual’ texture-selective areas are similarly recruited when observers discriminate surface texture via touch. We used a blocked design in which participants attended to, and made same/different judgments about, sequential pairs of 3-dimensional plastic objects. During each block, the stimuli varied either in their shape (but not surface texture), or their surface texture (but not shape). In half of the scans, participants explored the stimuli using vision alone, and in the remaining scans the stimuli were explored via touch alone. In vision, the strongest fMRI responses to surface texture (versus shape) perception were observed within medial ventral temporal cortex – a result consistent with recent fMRI findings in vision. When stimuli were explored via touch, however, the strongest fMRI responses to surface texture (versus shape) perception were observed dorsally, within the parietal operculum (in the vicinity of secondary somatosensory cortex) and inferior frontal cortex. Importantly, however, we also observed significant texture-selective fMRI responses in medial ventral temporal cortex within areas analogous to those recruited during visual texture discrimination. Our imaging data demonstrate for the first time that ventro-medial temporal areas known to process visual textures are also recruited during the perception of surface texture via touch. Meeting abstract presented at VSS 2013