Discrete tactile feature comparison subprocess in human brain during a decision-making process

From sensory input to motor action, encoded sensory features flow sequentially along cortical networks for decision-making. Despite numerous studies probing the decision-making process, the subprocess that compares encoded sensory features before making a decision has not been fully elucidated in humans. In this study, we investigated sensory feature comparison by presenting two different tasks (a discrimination task, in which participants made decisions by comparing two sequential tactile stimuli; and a detection task, in which participants responded to the second tactile stimulus in two sequential stimuli) to epilepsy patients while recording electrocorticography (ECoG). By comparing tactile-specific gamma band (30-200 Hz) power between the two tasks, the decision-making process was divided into three subprocesses-categorization, comparison, and decision-consistent with a previous study (Heekeren et al., 2004). These subprocesses occurred sequentially in the dorsolateral prefrontal cortex, premotor cortex, secondary somatosensory cortex, and parietal lobe. Gamma power showed two different patterns of correlation with response time. In the inferior parietal lobule (IPL), there was a negative correlation. This means that as gamma power increased, response time decreased. In the secondary somatosensory cortex (S2), there was a positive correlation. Here, as gamma power increased, response time also increased. These results indicate that the IPL and S2 encode tactile feature comparison differently. Our connectivity analysis showed that the S2 transmitted tactile information to the IPL. Our findings suggest that multiple areas in the parietal lobe encode sensory feature comparison differently before making a decision.

Cortical thickness of the inferior parietal lobule as a potential predictor of relapse in men with alcohol dependence

Alcohol dependence is a disorder with a high recurrence rate that leads to a considerable public health burden. The risk of relapse appears to be related to a complex interplay of multiple factors. Herein, we aimed to explore the potential neural predictors of relapse in Chinese male patients with alcohol dependence. This study enrolled 58 male patients with alcohol dependence who had undergone acute detoxification. General demographic information and clinical features were collected. Magnetic resonance imaging data were used to measure cortical thickness across 34 regions of the brain. Patients were followed up at six months, and 51 patients completed the follow-up visit. These patients were divided into a relapser and an abstainer group. A binary logistic regression analysis was performed to investigate the potential risk factors of relapse. Compared to abstainers, relapsers showed higher inattention and non-planning impulsivity on the 11th version of the Barratt Impulsive Scale. The cortical thicknesses of the inferior-parietal lobules were significantly higher in abstainers compared with those in relapsers. Furthermore, binary logistic regression analysis showed that the thickness of the inferior parietal lobule predicted relapse, and lower non-planning impulse was a protective factor against relapse. Relapsers show poorer impulse control than abstainers, and structural magnetic resonance imaging revealed a decreased thickness of the inferior parietal lobule in relapsers. Our results indicate the thickness of the inferior parietal lobule as a potential relapse predictor in male patients with alcohol dependence.

Functional reorganization of brain activity in children with attention-deficit/hyperactivity disorder: Evidence from the modulatory effect of cognitive demand during visuospatial attention task

Previous studies reported that the inferior parietal lobule (IPL) had lower activation during visuospatial attention in children with attention-deficit/hyperactivity disorder (ADHD), while the functional connectivity (FC) between the IPL and other brain regions and how cognitive demand might modulate IPL's FC remain unclear. We performed a functional magnetic resonance imaging experiment recruiting two task conditions with relatively low and high cognitive demand of visuospatial attention. Forty-four children with ADHD and 36 age- and sex-matched healthy controls were included. IPL's regional activation and FC intensities were compared between groups and correlated with clinical measurements. We found that the IPL had significantly reduced activation in children with ADHD compared to healthy controls and this abnormal activation was not modulated by the cognitive demand of visuospatial attention. Importantly, further analysis revealed that the functional connectivity between IPL and inferior frontal gyrus was modulated by the cognitive demand of visuospatial attention in children with ADHD. These results revealed a modulatory effect of cognitive demand of visuospatial attention on IPL's functional connectivity but not IPL's activation in children with ADHD. More generally, these results highlight the functional reorganization of the brain activity as a possible compensatory strategy in response to the symptoms of ADHD.

Differential expression of diacylglycerol kinase ζ is involved in inferior parietal lobule-related dysfunction in schizophrenia with cognitive impairments

BACKGROUND

Cognitive impairment is the main factor in the poor prognosis of schizophrenia, but its mechanism remains unclear. The inferior parietal lobule (IPL) is related to various clinical symptoms and cognitive impairment in schizophrenia. We aimed to explore the relationship between IPL-related functions and cognitive impairment in schizophrenia.

METHODS

136 schizophrenia patients and 146 demographically matched healthy controls were enrolled for a cross-sectional study. High-spatial-resolution structural and resting-state functional images were acquired to demonstrate the alternations of brain structure and function. At the same time, the digit span and digit symbol coding tasks of the Chinese Wechsler Adult Intelligence Test Revised (WAIS-RC) were utilized in assessing the subjects' cognitive function. Patients were divided into cognitive impairment and normal cognitive groups according to their cognitive score and then compared whether there were differences between the three groups in fractional amplitude of low-frequency fluctuation (fALFF). In addition, we did a correlation analysis between cognitive function and the fALFF for the left IPL of patients and healthy controls. Based on the Allen Human Brain Atlas, we obtained genes expressed in the left IPL, which were then intersected with the transcriptome-wide association study results and differentially expressed genes in schizophrenia.

RESULTS

Grouping of patients by the backward digit span task and the digit symbol coding task showed differences in fALFF values between healthy controls and cognitive impairment patients (P < 0.05). We found a negative correlation between the backward digit span task score and fALFF of the left IPL in healthy controls (r = - 0.388, P = 0.003), which was not seen in patients (r = 0.203, P = 0.020). In addition, none of the other analyses were statistically significant (P > 0.017). In addition, we found that diacylglycerol kinase ζ (DGKζ) is differentially expressed in the left IPL and associated with schizophrenia.

CONCLUSION

Our study demonstrates that the left IPL plays a vital role in cognitive impairment in schizophrenia. DGKζ may act as an essential regulator in the left IPL of schizophrenia patients with cognitive impairment.

Cortical thickness of the inferior parietal lobule as a potential predictor of relapse in men with alcohol dependence

Background

Alcohol dependence (AD) is a disorder with a high recurrence rate that leads to a considerable public health burden. The risk of relapse appears to be related to a complex interplay of multiple factors. Herein, we aimed to explore the potential neural predictors of relapse in Chinese male patients with AD.

Methods

This study enrolled 58 male patients with AD who had undergone acute detoxification. General demographic information and clinical features were collected. Magnetic resonance imaging (MRI) data were used to measure cortical thickness across 34 regions of the brain. Patients were followed up at 6 months, and 51 patients completed the follow-up visit. These patients were divided into a relapser and an abstainer group. A binary logistic regression analysis was performed to investigate the potential risk factors of relapse.

Results

Compared to abstainers, relapsers showed higher inattention and non-planning impulsivity on the 11th version of the Barratt Impulsive Scale. The cortical thicknesses of the inferior-parietal lobule were significantly greater in abstainers compared with those in relapsers. Furthermore, binary logistic regression analysis showed that the thickness of the inferior parietal lobule predicted relapse.

Conclusions

Relapsers show poorer impulse control than abstainers, and MRI imaging shows a decreased thickness of the inferior parietal lobule in relapsers. Our results indicate the thickness of the inferior parietal lobule as a potential relapse predictor in male patients with AD.

Disentangling influences of dyslexia, development, and reading experience on effective brain connectivity in children

Altered brain connectivity between regions of the reading network has been associated with reading difficulties. However, it remains unclear whether connectivity differences between children with dyslexia (DYS) and those with typical reading skills (TR) are specific to reading impairments or to reading experience. In this functional MRI study, 132 children (M = 10.06 y, SD = 1.46) performed a phonological lexical decision task. We aimed to disentangle (1) disorder-specific from (2) experience-related differences in effective connectivity and to (3) characterize the development of DYS and TR. We applied dynamic causal modeling to age-matched (n_dys = 25, n_TR = 35) and reading-level-matched (n_dys = 25, n_TR = 22) groups. Developmental effects were assessed in beginning and advanced readers (TR: n_beg = 48, n_adv = 35, DYS: n_beg = 24, n_adv = 25). We show that altered feedback connectivity between the inferior parietal lobule and the visual word form area (VWFA) during print processing can be specifically attributed to reading impairments, because these alterations were found in DYS compared to both the age-matched and reading-level-matched TR. In contrast, feedforward connectivity from the VWFA to parietal and frontal regions characterized experience in TR and increased with age and reading skill. These directed connectivity findings pinpoint disorder-specific and experience-dependent alterations in the brain's reading network.

Working memory biases early object discrimination and parietal activity during attentional selection

The contents of working memory (WM) guide visual attention, but the neural mechanisms underlying WM biases remains unclear. Here, we used simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) approaches to characterize the timing and location of the neural response underlying WM guidance during a visual search task. Behaviorally, we observed faster search performance when the WM contents matching targets (valid) compared to when WM contents did not reappear (neutral). The EEG data showed similar benefit effects of posterior N1 component, in which targets induced larger N1 amplitudes in the valid condition than in the neutral condition. Interestingly, the fMRI activation in left supramarginal gyrus (SMG)/inferior parietal lobule (IPL) and bilateral occipital cortex was lower in the valid compared to neutral conditions. Importantly, the magnitude of the increased N1 activity and the decreased fMRI activity in the left SMG/IPL predicted the extent of search improvement at an individual subject level. These results suggest that information held in WM enhances early object discrimination during attentional selection, and the left SMG/IPL may be a critical region in mediating goal-directed processing under WM biases in human visual attention.

Minimal scanning duration for producing individualized repetitive transcranial magnetic stimulation targets

This study aimed to determine the minimal scanning duration of functional magnetic resonance imaging (fMRI) for producing individualized repetitive transcranial magnetic stimulation (rTMS) targets that are superior to the group-level targets. This study included 30 healthy subjects and 20 depressive patients with high-sampled fMRI data (> 69 min). We computed suboptimal targets by gradually increasing the scanning duration beginning at 6 min. The suboptimal target connectivity and spatial distance to the optimal target (based on the full-duration scanning data) were compared to an anatomically fixed target from a group analysis (termed as the group target). These analyses were repeated for healthy subjects and depressive patients, as well as for target masks in the dorsolateral prefrontal cortex (DLPFC) and inferior parietal lobule (IPL). As the scanning duration increased, the suboptimal targets gradually approached the optimal targets in the healthy subjects. Compared with the group targets, the suboptimal targets in the DLPFC showed higher connectivity strength after 10 min of data collection and shorter spatial distance after 40 min. Similar results were found in major depressive patients. In the IPL, the minimal scanning duration decreased to 6 and 8 min for connectivity strength and distance, respectively. These findings provide an important reference for individualized target definition in terms of scanning duration, which may standardize connectivity-based personalized studies. Future research is needed to further validate the therapeutic effects of the approach.

Childhood trauma is associated with social anhedonia and brain gray matter volume differences in healthy subjects

The present study tested the effects of childhood trauma (CT) on trait social anhedonia (SA) and on gray matter volume (GMV) and explored the possible relationships among CT, SA and brain GMV. Forty-three healthy individuals with experience of moderate-to-severe CT and sixty-eight individuals with no or low CT participated in the present study. Trait SA was evaluated using the Revised Social Anhedonia Scale. GMV was measured using voxel-based morphometry. Participants with moderate-to-severe CT had elevated trait SA, as well as brain volumetric differences in left inferior parietal lobule (IPL), left precuneus, right insula, left superior temporal gyrus, and left middle occipital gyrus extending into middle temporal gyrus relative to participants with no or low level of CT. CT was also found to be positively correlated with GMV in right dorsolateral prefrontal cortex (DLPFC) and bilateral precuneus. Partial mediation effect of GMV in left IPL and right DLPFC on the relationship between CT and trait SA was significant. These findings suggest that CT may have effects on trait SA and on GMV of widespread brain regions. GMV differences in DLPFC and left IPL may mediate the effect of CT on trait SA, although this needs to be verified by future longitudinal studies.

Neural correlates of doubt in decision-making

The experience of doubt, the lack of confidence in one's perceptions, internal states, memory and attention, can be due to the variability in occurrence of a phenomenon or can be driven by the internal experience of uncertainty based on subjective evaluation of the environment. Although the experience of some doubt is adaptive in normal cognitive functioning, excessive doubt can significantly impair decision-making and in extreme cases give rise to psychopathology. Although neuroimaging studies have provided some insight into the network of brain areas that is engaged when decision-making involves uncertainty, it remains unclear if dysfunction in these areas also gives rise to the experience and pathological expression of doubt. This study examined the neural correlates of doubt using neuroimaging during the performance of a forced-choice perceptual decision-making task under varying levels of uncertainty in participants who reported either low or high doubt. Participants reporting high doubt exhibited increased activation in the bilateral inferior parietal lobule (IPL) during perceptual decision-making which was not observed in participants who reported low doubt. Furthermore, activity in the IPL in high doubt participants was associated with clinical measures of doubt and showed functional connectivity differences between the high and low doubt groups. The findings of the current study suggest a key role of the IPL and provide a network of brain regions that may play a role in the experience and expression of doubt.

The neural network underlying individual differences in conflict adaptation effect

Individuals must constantly adjust their behavior to adapt to the changing environment, and this dynamic adjustment ability has been studied through the conflict adaptation effect (CAE). We explored the resting state brain network underlying individual differences in CAE. The functional connection strength between dorsolateral prefrontal cortex (DLPFC) and bilateral insula or right anterior cingulate cortex (ACC) was negatively correlated with CAE, whereas the connection strength between DLPFC and left inferior parietal lobule was positively correlated with CAE. We speculated that, when faced with conflict, individuals with low CAE employ salience network to detect conflict, and then control is performed by DLPFC; in individuals with high CAEs who maintain a high level of control in all tasks, conflict is resolved mainly by the central executive network. In other words, in conflict tasks, individuals with high CAEs adopt proactive control strategies, but their counterparts with low CAEs employ reactive control strategies.

Inferior parietal lobule involved in representation of "what" in a delayed-action Libet task

Intentional motor action is typically characterized by the decision about the timing, and the selection of the action variant, known as the "what" component. We compared free action selection with instructed action, where the movement type was externally cued, in order to investigate the action selection and action representation in a Libet's task. Temporal and spatial locus of these processes was examined using the combination of high-density electroencephalography, topographic analysis of variance, and source reconstruction. Instructed action, engaging representation of the response movement, was associated with distinct negativity at the parietal and centro-parietal channels starting around 750 ms before the movement, which has a source particularly in the bilateral inferior parietal lobule. This suggests that in delayed-action tasks, the process of action representation in the inferior parietal lobule may play an important part in the larger parieto-frontal activity responsible for movement selection.

Associative memory improvement after 5 days of magnetic stimulation: A replication experiment with active controls

Associative memory (AM) is an essential function of everyday life, but is often disrupted in many neurological diseases. Recent studies have found that repetitive transcranial magnetic stimulation (rTMS) can effectively enhance AM and have shown its potential in clinical applications. In this study, we aimed to reproduce the 5-day rTMS effect on AM in a Chinese version of a face-cued word recall task. In an open-label experiment, AM scores were significantly improved after active 20-Hz rTMS on individualized inferior parietal lobule (IPL) targets. To exclude the placebo effect, we performed a second experiment and added rTMS of the pre-supplementary motor area (preSMA) as an active control. In this within-subject crossover experiment, participants received active rTMS on IPL and preSMA targets, separated by at least 2 weeks. A Stroop task was included as a control test, which was more likely to be modulated by preSMA stimulations. We found that stimulations on IPL targets significantly improved AM, but this change did not significantly higher than that induced by preSMA stimulations. No significant change in Stroop measures were found in either IPL or preSMA condition. In summary, this study did not support that the 5 days of rTMS on individualized IPL targets could improve AM more than placebo rTMS. Further work is required to improve the rTMS paradigms to enhance the aftereffects in memory.

Higher-order sensorimotor circuit of the brain's global network supports human consciousness

Consciousness is a mental characteristic of the human mind, whose exact neural features remain unclear. We aimed to identify the critical nodes within the brain's global functional network that support consciousness. To that end, we collected a large fMRI resting state dataset with subjects in at least one of the following three consciousness states: preserved (including the healthy awake state, and patients with a brain injury history (BI) that is fully conscious), reduced (including the N1-sleep state, and minimally conscious state), and lost (including the N3-sleep state, anesthesia, and unresponsive wakefulness state). We also included a unique dataset of subjects in rapid eye movement sleep state (REM-sleep) to test for the presence of consciousness with minimum movements and sensory input. To identify critical nodes, i.e., hubs, within the brain's global functional network, we used a graph-theoretical measure of degree centrality conjoined with ROI-based functional connectivity. Using these methods, we identified various higher-order sensory and motor regions including the supplementary motor area, bilateral supramarginal gyrus (part of inferior parietal lobule), supragenual/dorsal anterior cingulate cortex, and left middle temporal gyrus, that could be important hubs whose degree centrality was significantly reduced when consciousness was reduced or absent. Additionally, we identified a sensorimotor circuit, in which the functional connectivity among these regions was significantly correlated with levels of consciousness across the different groups, and remained present in the REM-sleep group. Taken together, we demonstrated that regions forming a higher-order sensorimotor integration circuit are involved in supporting consciousness within the brain's global functional network. That offers novel and more mechanism-guided treatment targets for disorders of consciousness.

Inclusion of African American/Black adults in a pilot brain proteomics study of Alzheimer's disease

Alzheimer's disease (AD) disproportionately affects certain racial and ethnic subgroups, such as African American/Black and Hispanic adults. Genetic, comorbid, and socioeconomic risk factors contribute to this disparity; however, the molecular contributions have been largely unexplored. Herein, we conducted a pilot proteomics study of postmortem brains from African American/Black and non-Hispanic White adults neuropathologically diagnosed with AD compared to closely-matched cognitively normal individuals. Examination of hippocampus, inferior parietal lobule, and globus pallidus regions using quantitative proteomics resulted in 568 differentially-expressed proteins in AD. These proteins were consistent with the literature and included glial fibrillary acidic protein, peroxiredoxin-1, and annexin A5. In addition, 351 novel proteins in AD were identified, which could partially be due to cohort diversity. From linear regression analyses, we identified 185 proteins with significant race x diagnosis interactions across various brain regions. These differences generally were reflective of differential expression of proteins in AD that occurred in only a single racial/ethnic group. Overall, this pilot study suggests that disease understanding can be furthered by including diversity in racial/ethnic groups; however, this must be done on a larger scale.

Region-dependent bidirectional plasticity in M1 following quadripulse transcranial magnetic stimulation in the inferior parietal cortex

BACKGROUND

The ability to manipulate the excitability of the network between the inferior parietal lobule (IPL) and primary motor cortex (M1) may have clinical value.

OBJECTIVE

To investigate the possibility of inducing long-lasting changes in M1 excitability by applying quadripulse transcranial magnetic stimulation (QPS) to the IPL, and to ascertain stimulus condition- and site-dependent differences in the effects.

METHODS

QPS was applied to M1, the primary somatosensory cortex (S1), the supramarginal gyrus (SMG) and angular gyrus (AG) IPL areas, with the inter-stimulus interval (ISI) in the train of pulses set to either 5 ms (QPS-5) or 50 ms (QPS-50). QPS was repeated at 0.2 Hz for 30 min, or not presented (sham condition). Excitability changes in the target site were examined by means of single-pulse transcranial magnetic stimulation (TMS).

RESULTS

QPS-5 and QPS-50 at M1 increased and decreased M1 excitability, respectively. QPS at S1 induced no obvious change in M1 excitability. However, QPS at the SMG induced mainly suppressive effects in M1 for at least 30 min, regardless of the ISI length. Both QPS ISIs at the AG yielded significantly different MEP compared to those at the SMG. Thus, the direction of the plastic effect of QPS differed depending on the site, even under the same stimulation conditions.

CONCLUSIONS

QPS at the IPL produced long-lasting changes in M1 excitability, which differed depending on the precise stimulation site within the IPL. These results raise the possibility of noninvasive induction of functional plasticity in M1 via input from the IPL.

Development of the functional connectivity of the frontoparietal mirror neuron network in preschool Children: An investigation under resting state

Previous task-related imaging studies in adults have demonstrated that there is a frontoparietal mirror neuron system (MNS) that preferentially engages in self-recognition. However, the development of the MNS during preschool (age 3-5 years) has not been thoroughly examined. In this study, we investigated the development of the MNS by examining the correlations in spontaneous fluctuations of the functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) signal in healthy, 3-5-year-old preschool children (n = 30, 15 in each group). Using a ROI-based (inferior frontal gyrus) functional connectivity analysis, we identified a right lateralized MNS during rest in both groups with a positive correlation between the inferior frontal gyrus and inferior parietal lobule. A significant increase in the functional connectivity of the MNS was observed in the older group. Our results suggest that the spontaneous functional connectivity of the MNS is shaped at as early as 3 years of age and undergoes age-related development within the preschool period.

Affective and cortical EEG gamma responses to emotional movies in women with high vs low traits of empathy

The present study sought to investigate how differences in trait empathy can influence emotional reactivity to a specific set of affective categories. Forty-one female students, divided in High (HE, n = 20) and Low (LE, n = 21) trait empathy, watched eight validated movie clips divided in four emotional categories (Erotic, Fear, Compassion and Neutral) while subjective evaluation of emotion and EEG gamma activity were recorded. Analysis of self-reports revealed that HE compared to LE exhibited an increased arousal level to all emotional clips. Concerning EEG data, the HE group showed a greater cortical gamma to all the emotional categories compared to the Neutral, while the LE group had greater response only to the negative clips. Participants in the HE group also showed a strong positive correlation between subjective arousal and cortical activity in response to Fear and Compassion clips. The greatest correlation was found to Compassion clips and was located in the right inferior parietal lobe (r₍₁₈₎ = 0.63), an important hub for both sensory-emotion integration and empathic sharing of others' emotions. Results suggest that high empathy was associated with enhanced gamma activity and greater self-reported arousal to all emotional stimuli. Furthermore, in this group, scenes with crying characters prompted a distinctive and localized cortical processing.

Functional brain alterations in acute sleep deprivation: An activation likelihood estimation meta-analysis

Sleep deprivation (SD) is a common problem in modern societies, which leads to cognitive dysfunctions including attention lapses, impaired working memory, hindering decision making, impaired emotional processing, and motor vehicle accidents. Numerous neuroimaging studies have investigated the neural correlates of SD, but these studies have reported inconsistent results. Thus, we aimed to identify convergent patterns of abnormal brain functions due to acute SD. Based on the preferred reporting for systematic reviews and meta-analyses statement, we searched the PubMed database and performed reference tracking and finally retrieved 31 eligible functional neuroimaging studies. Then, we applied activation estimation likelihood meta-analysis and found reduced activity mainly in the right intraparietal sulcus and superior parietal lobule. The functional decoding analysis using the BrainMap database indicated that this region is mostly related to visuospatial perception, memory and reasoning. The significant co-activation of this region using the BrainMap database were found in the left superior parietal lobule, intraparietal sulcus, bilateral occipital cortex, left fusiform gyrus and thalamus. This region also connected with the superior parietal lobule, intraparietal sulcus, insula, inferior frontal gyrus, precentral, occipital and cerebellum through resting-state functional connectivity in healthy subjects. Taken together, our findings highlight the role of superior parietal cortex in SD.

Interaction of the effects associated with auditory-motor integration and attention-engaging listening tasks

A number of previous studies have implicated regions in posterior auditory cortex (AC) in auditory-motor integration during speech production. Other studies, in turn, have shown that activation in AC and adjacent regions in the inferior parietal lobule (IPL) is strongly modulated during active listening and depends on task requirements. The present fMRI study investigated whether auditory-motor effects interact with those related to active listening tasks in AC and IPL. In separate task blocks, our subjects performed either auditory discrimination or 2-back memory tasks on phonemic or nonphonemic vowels. They responded to targets by either overtly repeating the last vowel of a target pair, overtly producing a given response vowel, or by pressing a response button. We hypothesized that the requirements for auditory-motor integration, and the associated activation, would be stronger during repetition than production responses and during repetition of nonphonemic than phonemic vowels. We also hypothesized that if auditory-motor effects are independent of task-dependent modulations, then the auditory-motor effects should not differ during discrimination and 2-back tasks. We found that activation in AC and IPL was significantly modulated by task (discrimination vs. 2-back), vocal-response type (repetition vs. production), and motor-response type (vocal vs. button). Motor-response and task effects interacted in IPL but not in AC. Overall, the results support the view that regions in posterior AC are important in auditory-motor integration. However, the present study shows that activation in wide AC and IPL regions is modulated by the motor requirements of active listening tasks in a more general manner. Further, the results suggest that activation modulations in AC associated with attention-engaging listening tasks and those associated with auditory-motor performance are mediated by independent mechanisms.

Vestibular dysfunction as cortical damage with amyotrophic lateral sclerosis

BACKGROUND

Cortical damage in areas such as the frontal lobe is reported in amyotrophic lateral sclerosis (ALS). However, aside from executive dysfunction, the pathological significance of this cortical damage has yet to be clarified. The present study investigated the effects of cortical damage on vestibular function in ALS.

METHODS

Subjects comprised 18 ALS patients and 18 age- and sex-matched healthy controls. Cold air caloric stimulation was performed in all subjects to induce vestibular nystagmus, which was analysed to evaluate vestibular function. Visual suppression testing to investigate the suppressive effects of visual stimuli on vestibular nystagmus was expressed as suppression rate (SR, %). Executive function was tested using the frontal assessment battery (FAB).

RESULTS

Suppression rate and FAB score were significantly lower in the ALS group than in the control group (p < 0.01 each). A positive correlation was also observed between SR and FAB score (R = 0.65, p = 0.023).

CONCLUSION

Visual suppression testing showed significant damage to the central nervous system vestibular control mechanisms, which utilize visual information in the ALS group and a positive correlation between SR and FAB score suggest a relationship between frontal lobe damage and impaired vestibular control. A simple vestibular function test may be useful as a tool to objectively monitor the progression of cerebral lesions in ALS.

Functionally distinct contributions of parietal cortex to a numerical landmark task: An fMRI study

This study aimed at establishing the neural basis of magnitude processing of multiple numbers from working memory. We designed a numerical landmark task and embedded it in a fragmented trial event-related fMRI design, allowing to separate encoding from decision processing. An attentional localiser task not involving numbers allowed further functional specification. The results show that in a numerical landmark task the right anterior intraparietal sulcus is involved in number encoding while more posterior parietal regions, bilateral superior parietal lobule and right inferior parietal lobule, provide domain-general support in the form of constructing a working memory representation or orienting spatial attention within that mental representation during number comparison. The results are in line with earlier studies reporting a functional distinction between anterior and posterior parietal contributions to number processing and further specify their role at a functional level.

The neural basis for understanding imitation-induced musical meaning: The role of the human mirror system

Music can convey meanings by imitating phenomena of the extramusical world, and these imitation-induced musical meanings can be understood by listeners. Although the human mirror system (HMS) is implicated in imitation, little is known about the HMS's role in making sense of meaning that derives from musical imitation. To answer this question, we used fMRI to examine listeners' brain activities during the processing of imitation-induced musical meaning with a cross-modal semantic priming paradigm. Eleven normal individuals and 11 individuals with congenital amusia, a neurodevelopmental disorder of musical processing, participated in the experiment. Target pictures with either an upward or downward movement were primed by semantically congruent or incongruent melodic sequences characterized by the direction of pitch change (upward or downward). When contrasting the incongruent with the congruent condition between the two groups, we found greater activations in the left supramarginal gyrus/inferior parietal lobule and inferior frontal gyrus in normals but not in amusics. The implications of these findings in terms of the role of the HMS in understanding imitation-induced musical meaning are discussed.

Classic Hallucinogens and Mystical Experiences: Phenomenology and Neural Correlates

This chapter begins with a brief review of descriptions and definitions of mystical-type experiences and the historical connection between classic hallucinogens and mystical experiences. The chapter then explores the empirical literature on experiences with classic hallucinogens in which claims about mystical or religious experiences have been made. A psychometrically validated questionnaire is described for the reliable measurement of mystical-type experiences occasioned by classic hallucinogens. Controlled laboratory studies show that under double-blind conditions that provide significant controls for expectancy bias, psilocybin can occasion complete mystical experiences in the majority of people studied. These effects are dose-dependent, specific to psilocybin compared to placebo or a psychoactive control substance, and have enduring impact on the moods, attitudes, and behaviors of participants as assessed by self-report of participants and ratings by community observers. Other studies suggest that enduring personal meaning in healthy volunteers and therapeutic outcomes in patients, including reduction and cessation of substance abuse behaviors and reduction of anxiety and depression in patients with a life-threatening cancer diagnosis, are related to the occurrence of mystical experiences during drug sessions. The final sections of the chapter draw parallels in human neuroscience research between the neural bases of experiences with classic hallucinogens and the neural bases of meditative practices for which claims of mystical-type experience are sometimes made. From these parallels, a functional neural model of mystical experience is proposed, based on changes in the default mode network of the brain that have been observed after the administration of classic hallucinogens and during meditation practices for which mystical-type claims have been made.

Steady-state evoked potentials distinguish brain mechanisms of self-paced versus synchronization finger tapping

Sensorimotor synchronization (SMS) requires aligning motor actions to external events and represents a core part of both musical and dance performances. In the current study, to isolate the brain mechanisms involved in synchronizing finger tapping with a musical beat, we compared SMS to pure self-paced finger tapping and listen-only conditions at different tempi. We analyzed EEG data using frequency domain steady-state evoked potentials (SSEPs) to identify sustained electrophysiological brain activity during repetitive tasks. Behavioral results revealed different timing modes between SMS and self-paced finger tapping, associated with distinct scalp topographies, thus suggesting different underlying brain sources. After subtraction of the listen-only brain activity, SMS was compared to self-paced finger tapping. Resulting source estimations showed stronger activation of the left inferior frontal gyrus during SMS, and stronger activation of the bilateral inferior parietal lobule during self-paced finger tapping. These results point to the left inferior frontal gyrus as a pivot for perception-action coupling. We discuss our findings in the context of the ongoing debate about SSEPs interpretation given the variety of brain events contributing to SSEPs and similar EEG frequency responses.

Disrupted functional connectivity patterns of the insula subregions in drug-free major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is characterized by impairments in emotional and cognitive functions. Emerging studies have shown that cognition and emotion interact by reaching identical brain regions, and the insula is one such region with functional and structural heterogeneity. Although previous literatures have shown the role of insula in MDD，it remains unclear whether the insular subregions show differential change patterns in MDD.

METHODS

Using the resting-state fMRI data in a group of 23 drug-free MDD patients and 34 healthy controls (HCs), we investigated whether the abnormal connectivity patterns of insular sub-regions or any behavioural correlates can be detected in MDD. Further hierarchical cluster analysis was used to identify the functional connectivity-clustering patterns of insular sub-regions.

RESULTS

Compared with HCs, the MDD exhibited higher connectivities between dorsal agranular insula and inferior parietal lobule and between ventral dysgranular and granular insula and thalamus/habehula, and lower connectivity of hypergranular insula to subgenual anterior cingulate cortex. Moreover, the three subregions with significant group differences were in three separate functional systems along anterior-to-posteior gradient. The anterior and middle insula showed positive correlation with depressive severity, while the posterior insular was to the contrary.

LIMITATIONS

The small and unbalanced sample size, only included moderate and severe depression and the possible inter-individual differences may limit the interpretability.

CONCLUSIONS

These findings provided evidences for the MDD-related effects in functional connectivity patterns of insular subregions, and revealed that the subregions might be involved in different neural circuits associated with the contrary impacts on the depressive symptoms.

Altered perspective-dependent brain activation while viewing hands and associated imitation difficulties in individuals with autism spectrum disorder

Background

Individuals with autism spectrum disorder (ASD) appear to have a unique awareness of their own body, which may be associated with difficulties of gestural interaction. In typically developing (TD) individuals, the perception of body parts is processed in various brain regions. For instance, activation of the lateral occipito-temporal cortex (LOTC) is known to depend on perspective (i.e., first- or third-person perspective) and identity (i.e., own vs. another person's body). In the present study, we examined how perspective and identity affect brain activation in individuals with ASD, and how perspective- and identity-dependent brain activation is associated with gestural imitation abilities.

Methods

Eighteen young adults with ASD and 18 TD individuals participated in an fMRI study in which the participants observed their own or another person's hands from the first- and third-person perspectives. We examined whether the brain activation associated with perspective and identity was altered in individuals with ASD. Furthermore, we identified the brain regions the activity of which correlated with gestural imitation difficulties in individuals with ASD.

Results

In the TD group, the left LOTC was more strongly activated by viewing a hand from the third-person perspective compared with the first-person perspective. This perspective effect in the left LOTC was significantly attenuated in the ASD group. We also observed significant group differences in the perspective effect in the medial prefrontal cortex (mPFC). Correlation analysis revealed that the perspective effect in the inferior parietal lobule (IPL) and cerebellum was associated with the gestural imitation ability in individuals with ASD.

Conclusions

Our study suggests that atypical visual self-body recognition in individuals with ASD is associated with an altered perspective effect in the LOTC and mPFC, which are thought to be involved in the physical and core selves, respectively. Furthermore, the gestural imitation difficulty in individuals with ASD might be associated with the altered activation in the IPL and cerebellum, but not in the LOTC. These findings shed light on common and divergent neural mechanisms underlying atypical visual self-body awareness and gestural interaction in ASD.

Intentionally not imitating: Insula cortex engaged for top-down control of action mirroring

Perception and action are inextricably linked, down to the level of single cells which have both visual and motor response properties - dubbed 'mirror neurons'. The mirror neuron system is generally associated with direct-matching or resonance between observed and executed actions (and goals). Yet in everyday interactions responding to another's movements with matching actions (or goals) is not always appropriate. Here we examine processes associated with intentionally not imitating, as separable from merely detecting an observed action as mismatching one's own. Using fMRI, we test how matched and mismatched stimulus-response mapping for actions is modulated depending on task-relevance. Participants were either cued to intentionally copy or oppose a presented action (intentional imitation or counter-imitation), or cued to perform a predefined action regardless of the presented action (incidental imitation or counter-imitation). We found distinct cortical networks underlying imitation compared to counter-imitation, involving areas typically associated with an action observation network and widespread occipital activation. Intentionally counter-imitating particularly involved frontal-parietal networks, including the insula and cingulate cortices. This task-dependent recruitment of frontal networks for the intentional selection of opposing responses supports previous evidence for the preparatory suppression of imitative responses. Sensorimotor mirroring is modulated via control processes, which complex human interactions often require.

Supramodal effect of rightward prismatic adaptation on spatial representations within the ventral attentional system

Rightward prismatic adaptation (R-PA) was shown to alleviate not only visuo-spatial but also auditory symptoms in neglect. The neural mechanisms underlying the effect of R-PA have been previously investigated in visual tasks, demonstrating a shift of hemispheric dominance for visuo-spatial attention from the right to the left hemisphere both in normal subjects and in patients. We have investigated whether the same neural mechanisms underlie the supramodal effect of R-PA on auditory attention. Normal subjects underwent a brief session of R-PA, which was preceded and followed by an fMRI evaluation during which subjects detected targets within the left, central and right space in the auditory or visual modality. R-PA-related changes in activation patterns were found bilaterally in the inferior parietal lobule. In either modality, the representation of the left, central and right space increased in the left IPL, whereas the representation of the right space decreased in the right IPL. Thus, a brief exposure to R-PA modulated the representation of the auditory and visual space within the ventral attentional system. This shift in hemispheric dominance for auditory spatial attention offers a parsimonious explanation for the previously reported effects of R-PA on auditory symptoms in neglect.

Resting-state functional reorganization in Parkinson's disease: An activation likelihood estimation meta-analysis

Parkinson's disease (PD) is a common progressive neurodegenerative disorder. Studies using resting-state functional magnetic resonance imaging (fMRI) to investigate underlying pathophysiology of motor and non-motor symptoms in PD yielded largely inconsistent results. This quantitative neuroimaging meta-analysis aims to identify consistent abnormal intrinsic functional patterns in PD across studies. We used PubMed to retrieve suitable resting-state studies and stereotactic data were extracted from 28 individual between-group comparisons. Convergence across their findings was tested using the activation likelihood estimation (ALE) approach. We found convergent evidence for intrinsic functional disturbances in bilateral inferior parietal lobule (IPL) and the supramarginal gyrus in PD patients compared to healthy subjects. In follow-up task-based and task-independent functional connectivity (FC) analyses using two independent healthy subject data sets, we found that the regions showing convergent aberrations in PD formed an interconnected network mainly with the default mode network (DMN). Behavioral characterization of these regions using the BrainMap database suggested associated dysfunction of perception and executive processes. Taken together, our findings highlight the role of parietal cortex in the pathophysiology of PD.

Development of rostral inferior parietal lobule area functional connectivity from late childhood to early adulthood

Although the mirror neuron system (MNS) has been extensively studied in monkeys and adult humans, very little is known about its development. Previous studies suggest that the MNS is present by infancy and that the brain and MNS-related cognitive abilities (such as language, empathy, and imitation learning) continue to develop after childhood. In humans, the PFt area of the inferior parietal lobule (IPL) seems to particularly correlate with the functional properties of the PF area in primates, which contains mirror neurons. However, little is known about the functional connectivity (FC) of the PFt area with other brain areas and whether these networks change over time. Here, we investigated the FC development of the PFt area-based network in 59 healthy subjects aged 7-26 years at resting-state to study brain development from late childhood through adolescence to early adulthood. The bilateral PFt showed similar core FC networks, which included the frontal lobe, the cingulate gyri, the insula, the somatosensory cortex, the precuneus, the superior and inferior parietal lobules, the temporal lobe, and the cerebellum posterior lobes. Furthermore, the FC between the left PFt and the left IPL exhibited a significantly positive correlation with age, and the FC between the left PFt and the right postcentral gyrus exhibited a significantly negative correlation with age. In addition, the FC between the right PFt and the right putamen exhibited a significantly negative correlation with age. Our findings suggest that the PFt area-based network develops and is reorganized with age.

Vestibular Impairment in Frontotemporal Dementia Syndrome

Background

No studies to date have attempted to evaluate frontotemporal lobar degeneration from the perspective of the vestibular system.

Objective

The present study examined vestibular function in patients with frontotemporal dementia (FTD) clinical syndrome and evaluated whether vestibular disorders are involved in the clinical symptoms due to FTD.

Methods

Fourteen patients with FTD syndrome, as well as healthy elderly controls without dementia, were included in the present study. All subjects underwent vestibular function tests using electronystagmography, such as caloric tests and visual suppression (VS) tests, in which the induced caloric nystagmus was suppressed by visual stimuli. The association between clinical symptoms and vestibular function in the FTD syndrome group was further examined.

Results

In the FTD syndrome group, caloric nystagmus was not necessarily suppressed during VS tests. Furthermore, VS was observed to be significantly impaired in FTD syndrome patients with gait disturbance as compared to those without such disturbance.

Conclusion

The present study revealed that impairment of VS in patients with FTD results in an inability to regulate vestibular function by means of visual perception, regardless of multiple presumed neuropathological backgrounds. This could also be associated with gait disturbance in patients with FTD syndrome.

Selective functional connectivity abnormality of the transition zone of the inferior parietal lobule in schizophrenia

Structural and functional alterations in the inferior parietal lobule (IPL) in schizophrenia have been frequently reported; however, the IPL connectivity changes in schizophrenia remain largely unknown. Based on heterogeneity of the IPL in structure, connection and function, we hypothesize that the resting-state functional connectivities (rsFCs) of the IPL subregions are differentially affected in schizophrenia. This study included 95 schizophrenia patients and 104 healthy controls. The IPL subregions were defined according to a previous in vivo connection-based parcellation study. We calculated the rsFC of each IPL subregion and compared them between the two groups while controlling for the effects of age, gender, and grey matter volume. Among the six subregions of the left IPL and the five subregions of the right IPL, only the bilateral PFm (a transition zone of the IPL) subregions exhibited abnormal rsFC in schizophrenia. Specifically, the left PFm showed increased rsFC with the bilateral lingual gyri in schizophrenia patients than in healthy controls. The right PFm exhibited increased rsFC with the right lingual gyrus and inferior occipital gyrus, and bilateral mid-cingulate and sensorimotor cortices in schizophrenia patients. These findings suggest a selective rsFC abnormality in the IPL subregions in schizophrenia, characterized by the increased rsFC between the PFm subregion of the IPL and the visual and sensorimotor areas.

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Investigation of the subregional-level rsFC changes of the IPL in schizophrenia

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The PFm is only IPL subregion with significant rsFC changes in schizophrenia.

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Suggesting a selective rsFC abnormality in the IPL subregions in schizophrenia

Neural basis of understanding communicative actions: Changes associated with knowing the actor's intention and the meanings of the actions

People can communicate by using hand actions, e.g., signs. Understanding communicative actions requires that the observer knows that the actor has an intention to communicate and the meanings of the actions. Here, we investigated how this prior knowledge affects processing of observed actions. We used functional MRI to determine changes in action processing when non-signers were told that the observed actions are communicative (i.e., signs) and learned the meanings of half of the actions. Processing of hand actions activated the left and right inferior frontal gyrus (IFG, BA 44 and 45) when the communicative intention of the actor was known, even when the meanings of the actions remained unknown. These regions were not active when the observers did not know about the communicative nature of the hand actions. These findings suggest that the left and right IFG play a role in understanding the intention of the actor, but do not process visuospatial features of the communicative actions. Knowing the meanings of the hand actions further enhanced activity in the anterior part of the IFG (BA 45), the inferior parietal lobule and posterior inferior and middle temporal gyri in the left hemisphere. These left-hemisphere language regions could provide a link between meanings and observed actions. In sum, the findings provide evidence for the segregation of the networks involved in the neural processing of visuospatial features of communicative hand actions and those involved in understanding the actor’s intention and the meanings of the actions.

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Participants observed hand actions before and after learning that they are signs.

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Learning-induced changes in brain activity measured using fMRI.

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No activity in mirror neuron system when actions were not known to be communicative.

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Knowing the actor’s intention to communicate activated IFG and IPL.

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Knowing meanings of the actions increased activity in left IFG (BA 45), IPL and MTG.

Acoustical and categorical tasks differently modulate activations of human auditory cortex to vowels

The present study compared activations to prototype, nonprototype, nonphonemic, and cross-category vowel pairs during vowel discrimination, category discrimination, 2-back, and visual tasks. Our results support previous findings that areas of the superior temporal gyrus (STG) are sensitive to the speech-level difference between prototype vs. nonprototype and phonemic vs. nonphonemic vowels. Further, consistent with previous studies, we found enhanced activations in anterior-posterior STG and inferior parietal lobule (IPL) during the vowel discrimination and 2-back tasks, respectively. Unlike the vowel discrimination task, the category discrimination task was associated with strong IPL activations. Our results provide evidence that activations in STG and IPL strongly depend on whether the task requires analysis of detailed acoustical information or operations on categorical representations. Based on previous studies investigating activations during categorical pitch and spatial tasks, we argue that this distinction is probably not specific to speech.

Pathways to lexical ambiguity: fMRI evidence for bilateral fronto-parietal involvement in language processing

Numerous functional neuroimaging studies reported increased activity in the pars opercularis and the pars triangularis (Brodmann's areas 44 and 45) of the left hemisphere during the performance of linguistic tasks. The role of these areas in the right hemisphere in language processing is not understood and, although there is evidence from lesion studies that the right hemisphere is involved in the appreciation of semantic relations, no specific anatomical substrate has yet been identified. This event-related functional magnetic resonance imaging study compared brain activity during the performance of language processing trials in which either dominant or subordinate meaning activation of ambiguous words was required. The results show that the ventral part of the pars opercularis both in the left and the right hemisphere is centrally involved in language processing. In addition, they highlight the bilateral co-activation of this region with the supramarginal gyrus of the inferior parietal lobule during the processing of this type of linguistic material. This study, thus, provides the first evidence of co-activation of Broca's region and the inferior parietal lobule, succeeding in further specifying the relative contribution of these cortical areas to language processing.

Regional homogeneity and resting state functional connectivity: associations with exposure to early life stress

Early life stress (ELS) confers risk for psychiatric illness. Previous literature suggests ELS is associated with decreased resting-state functional connectivity (rs-FC) in adulthood, but there are no studies of resting-state neuronal activity in this population. This study investigated whether ELS-exposed individuals demonstrate resting-state activity patterns similar to those found in PTSD. Twenty-seven adults (14 with at least moderate ELS), who were medication-free and without psychiatric or medical illness, underwent MRI scans during two 4-minute rest periods. Resting-state activity was examined using regional homogeneity (ReHo), which estimates regional activation patterns through indices of localized concordance. ReHo values were compared between groups, followed by rs-FC analyses utilizing ReHo-localized areas as seeds to identify other involved regions. Relative to controls, ELS subjects demonstrated diminished ReHo in the inferior parietal lobule (IPL) and superior temporal gyrus (STG). ReHo values were inversely correlated with ELS severity. Secondary analyses revealed decreased rs-FC between the IPL and right precuneus/posterior cingulate, left fusiform gyrus, cerebellum and caudate in ELS subjects. These findings indicate that ELS is associated with altered resting-state activity and connectivity in brain regions involved in trauma-related psychiatric disorders. Future studies are needed to evaluate whether these associations represent potential imaging biomarkers of stress exposure.

Inferior parietal lobule volume and schneiderian first-rank symptoms in antipsychotic-naïve schizophrenia: a 3-tesla MRI study

BACKGROUND

As per Frith's neuro-cognitive model, inferior parietal lobule (IPL) is implicated in the pathogenesis of Schneiderian first-rank symptoms (FRS) in schizophrenia. The specific role of IPL structural abnormalities in the pathogenesis of FRS is yet to be ascertained.

MATERIALS AND METHODS

Using 3-tesla MRI scanner, this first-time study examined antipsychotic-naïve schizophrenia patients ( n = 28) (patients with FRS [FRS +]: N = 14, M: F = 7:7; and patients without FRS [FRS-]: N = 14, M: F = 7:7) in comparison with sex-, handedness-, education- and socioeconomic status-matched healthy controls (n = 14, M: F = 7:7). The volume of IPL was measured using a three-dimensional, interactive, semi-automated analysis, with good inter-rater reliability.

RESULTS

FRS + patients showed significant volume deficit in right IPL in comparison with healthy controls (F = 4.0; P=.028) after controlling for the potential confounding effects of age, sex and intracranial volume.

CONCLUSIONS

Right IPL volume deficit in FRS+patients adds further support to the Frith's model of FRS in schizophrenia.