Pain enhances functional connectivity of a brain network evoked by performance of a cognitive task

Experimental and clinical evidence indicates that pain can affect cognitive processes, but the cortical networks involved in pain-cognition interactions are unclear. In this study, we determined the effect of pain on the activity of cortical areas involved in cognition acting as a whole (i.e., a network). Subjects underwent functional magnetic resonance imaging (fMRI) while engaged in an attention-demanding cognitive task (multisource interference task) of varying difficulty and simultaneously receiving painful stimuli at varying intensities. The control (baseline) condition was simple finger tapping that had minimal cognitive demands and without pain. Functional connectivity analysis revealed a cortical network consisting of two anti-correlated parts: a task-negative part (precuneus/posterior cingulate cortex, medial frontal and inferior parietal/temporal) the activity of which correlated negatively with the cognitive task and positively with the control baseline, and a task-positive part (inferior frontal, superior parietal, premotor, and anterior insula cortices) the activity of which correlated positively with the cognitive task and negatively with the baseline. Independent components analysis revealed these opposing networks were operating at a low frequency (0.03-0.08 Hz). The functional connectivity of the task-positive network was increased by cognitive demand and by pain. We suggest this attention-specific network balances the needs of general self-referential and environmental awareness versus focused attention to salient information. We postulate that pain affects cognitive ability by its reliance on this common attention-specific network. These data provide evidence that pain can modulate a network presumed to be involved in focused attention, suggesting a mechanism for the interference of pain on cognitive ability by the consumption of attentional resources.     

EEG correlates of emotional tasks related to attentional demands

This research brings together two separate areas: (1) that of EEG processes associated with positive and negatively valenced emotional material; and (2) that of traditional psychophysiological research related to the “intake” and “rejection” of environmental stimuli. Forty males on each of two days were presented with tasks reflecting both attentional demands and affectual processing. Heart rate and bilateral EEG measures from frontal, parietal and temporal sites were recorded. Using a FFT (fast Fourier transform) electrocortical activity in the 2–7 Hz, 8–15 Hz, and 16–24 Hz was determined and analyzed. The results suggest emotional valence (i.e. positive and negative) and attentional demands (i.e. intake vs rejection) are differentially represented in terms of EEG functioning. An interaction of attentional demand with hemisphere was found for EEG alpha activity in the temporal and parietal areas. For emotional valence there was a significant main effect for EEG beta activity in both the temporal and parietal areas. Differential hemispheric activity was found using a factor analytic technique (PARAFAC) with positively valenced tasks being associated with right temporal beta. Heart rate changes for the attentional dimension were consistent with previous research.     

糖尿病视网膜病变患者自发活动性异常的脑区与MoCA的相关性研究

目的 基于静息态功能磁共振局部一致性技术探讨糖尿病视网膜病变患者局部脑区一致性的改变及与认知关系.方法 选择27例糖尿病视网膜病变(DR)及与之年龄、性别、受教育年限相匹配的单纯糖尿病(N-DR)患者27例,均进行实验室检查、蒙特利尔量表(MoCA)检测及头颅磁共振扫描.利用多元回归分析及Pearson回归分析观察临床变量与活动性异常活动脑区ReHo值之间的关系.结果 相对于N-DR,DR患者在左小脑后叶、右额叶/额中回/内侧回、右枕叶/楔叶/距状回、左颞叶/上/中回、右边缘叶/后扣带回、左顶叶/中央后回ReHo值降低;在左额叶/眶部额上回、左顶叶/楔前叶ReHo值增强.而且MoCA量表评分与颞叶及楔前叶异常活动的脑区存在相关性.降低的枕叶距状回及颞叶中回与糖化血红蛋白呈负相关,增强的眶额叶与糖化血红蛋白呈正相关.结论 糖尿病视网膜病变患者存在多个脑区活动性异常的表现,且这些局部异常活动的脑区与认知功能及糖化血红蛋白存在相关.     

Comparable fMRI activity with differential behavioural performance on mental rotation and overt verbal fluency tasks in healthy men and women

To explicate the neural correlates of sex differences in visuospatial and verbal fluency tasks, we examined behavioural performance and blood-oxygenation-level-dependent (BOLD) regional brain activity, using functional magnetic resonance imaging, during a three-dimensional (3D) mental rotation task and a compressed sequence overt verbal fluency task in a group of healthy men (n=9) and women (n=10; tested during the low-oestrogen phase of the menstrual cycle). Men outperformed women on the mental rotation task, and women outperformed men on the verbal fluency task. For the mental rotation task, men and women activated areas in the right superior parietal lobe and the bilateral middle occipital gyrus in association with the rotation condition. In addition, men activated the left middle temporal gyrus and the right angular gyrus. For verbal fluency, men activated areas in the bilateral superior frontal gyrus, right cingulate gyrus, left precentral gyrus, left medial frontal gyrus, left inferior frontal gyrus, thalamus, left parahippocampal gyrus and bilateral lingual gyrus, and women activated areas in the bilateral inferior frontal gyrus and left caudate. Despite observing task related activation in the hypothesised areas in men and women, no areas significantly differentiated the two sexes. Our results demonstrate comparable brain activation in men and women in association with mental rotation and verbal fluency function with differential performance, and provide support for sex differences in brain–behaviour relationships.     

Neural activation and memory for natural scenes: Explicit and spontaneous retrieval

Stimulus repetition elicits either enhancement or suppression in neural activity, and a recent fMRI meta‐analysis of repetition effects for visual stimuli (Kim, 2017) reported cross‐stimulus repetition enhancement in medial and lateral parietal cortex, as well as regions of prefrontal, temporal, and posterior cingulate cortex. Repetition enhancement was assessed here for repeated and novel scenes presented in the context of either an explicit episodic recognition task or an implicit judgment task, in order to study the role of spontaneous retrieval of episodic memories. Regardless of whether episodic memory was explicitly probed or not, repetition enhancement was found in medial posterior parietal (precuneus/cuneus), lateral parietal cortex (angular gyrus), as well as in medial prefrontal cortex (frontopolar), which did not differ by task. Enhancement effects in the posterior cingulate cortex were significantly larger during explicit compared to implicit task, primarily due to a lack of functional activity for new scenes. Taken together, the data are consistent with an interpretation that medial and (ventral) lateral parietal cortex are associated with spontaneous episodic retrieval, whereas posterior cingulate cortical regions may reflect task or decision processes.     

遭受多重侵害高职高专女生静息态脑功能局部一致性的研究

目的:探讨遭受多重侵害的高职高专女生静息态脑功能磁共振特点。方法:15名遭受多重侵害无创伤后应激症状被试(PV无PTSS组)、15名多重侵害有创伤后应激症状被试(PV有PTSS组)和15名正常对照接受静息态脑功能扫描。采用SPM8和静息态功能磁共振数据处理工具包分别进行数据预处理和ReHo分析。结果:静息状态下,与对照组相比,PV无PTSS组左侧额下回、左右额内侧回、右侧中央后回、左侧梭状回、左右海马旁回、右侧扣带回、左右豆状核和右侧岛叶的ReHo值降低;左右额上回、左右额中回、左右额下回、左右顶下小叶、左右楔前叶、左右颞上回、左侧颞横回、左右颞中回、右侧舌回和右侧扣带后回的ReHo值升高。与PV有PTSS组相比,PV无PTSS组在右侧额中回和额下回、左侧楔前叶、左侧舌回、左右海马旁回、左侧扣带回和左侧豆状核ReHo值降低;在左右额上回、左右额中回、左侧额内侧回、右侧中央后回、左侧缘上回、左右顶下小叶、左侧梭状回和左侧尾状核ReHo值升高。结论:遭受多重侵害但无创伤后应激症状的高职高专女生在静息状态下脑默认网络以及岛叶、基底神经节、海马旁回存在局部一致性信号异常,这些脑区异常可能为遭受多重侵害导致精神障碍的发病机制提供重要线索。     

Personality traits and the amplitude of spontaneous low-frequency oscillations during resting state

Recently, neural substrates of the Big Five personality model were investigated using neuroimaging. We examined the relationships between the amplitude of spontaneous low-frequency oscillations (LFO) and the Big Five traits using resting-state functional magnetic resonance imaging (R-fMRI). Twenty-four healthy right-handed undergraduates (23.13 ± 1.87 years, 9 males and 15 females) participated in 5-min R-fMRI and completed the NEO Five-Factor Inventory. We observed that Neuroticism correlated negatively with regional activity of the middle frontal gyrus and precuneus; Extraversion correlated positively with regional activity of the striatum, precuneus, and superior frontal gyrus; Openness correlated positively with the thalamus and amygdala, and negatively with the superior frontal gyrus; Conscientiousness correlated positively with regional activity of the middle frontal gyrus and correlated negatively with the cerebellum. Our results revealed the neural substrates of Extraversion, Neuroticism, Openness, and Conscientiousness in the amplitude of spontaneous LFO.     

Negative BOLD during tongue movement: A functional magnetic resonance imaging study

The aim of this functional magnetic resonance imaging (fMRI) study was to evaluate negative blood oxygen level-dependent (BOLD) signals during voluntary tongue movement. Deactivated (Negative BOLD) regions included the posterior parietal cortex (PPC), precuneus, and middle temporal gyrus. Activated (Positive BOLD) regions included the primary somatosensory-motor area (SMI), inferior parietal lobule, medial frontal gyrus, superior temporal gyrus, insula, lentiform nucleus, and thalamus. The results were not consistent with previous studies involving unilateral hand and finger movements showing the deactivation of motor-related cortical areas including the ipsilateral MI. The areas of Negative BOLD in the PPC and precuneus might reflect specific neural networks relating to voluntary tongue movement.     

视觉刺激状态下正常成人电针光明穴的脑功能性磁共振研究

目的:对比研究针刺足少阳胆经光明穴(GB37)与视觉刺激后引起的人脑血液动力学反应,探讨分析视觉刺激状态下针刺对脑功能活动区的影响。方法:25例健康志愿者随机分为无视觉刺激电针组(10例)与视觉刺激状态电针组(15例)。视觉刺激状态电针组15例健康自愿者中12例取得成功,并在2种不同的刺激模式(包括视觉刺激任务与视觉刺激状态下针刺光明穴)状态下进行血氧水平依赖性功能磁共振(BOLD-fMRI)实验;应用闪烁棋盘方格为视觉刺激任务,频率8Hz,最后以图像数据重组方法,检测受试者在接受视觉刺激任务与针刺状态时的大脑响应功能区的激活,并进行分析比较。结果:视觉刺激任务时见脑干、小脑后叶大面积激活、及边缘叶、海马、颞中回、颞下回激活;针刺状态时见顶叶中央后回、顶下小叶、顶叶楔前叶、额中回激活。在视觉刺激下时电针光明穴见额上回,额下回、顶叶楔前叶及枕叶舌回激活。结论:功能性磁共振技术可看出针刺后脑功能响应功能区的激活情况;视觉刺激的参与导致针刺脑激活区改变,且该变化具有重要的意义;针刺足少阳胆经光明穴对视觉系统转导通路整合有一定影响;此外,外界的刺激亦对针刺疗效可能有着显著的影响。     

Event related fMRI studies of voluntary and inhibited eye blinking using a time marker of EOG

Electrooculogram (EOG) measurements, along with infrared measurements, are commonly used to record eye blinking during functional magnetic resonance imaging (fMRI). We report herein, on the use of EOG in measuring voluntary and inhibited eye blinking during echo planar imaging (EPI) in an MR scanner. The inhibited eye blinking occurred during the period, in which subjects were requested not to blink their eyes. After the removal of gradient-field induced artifacts from the EOG signal, the waveform of the EOG clearly showed both voluntary and inhibited eye blinking. Using these data, each voluntary or inhibited eye-blinking event was used as the temporal cue for an event related fMRI. Activation of the bilateral parahippocampal, precentral gyrus and left supplementary motor area was observed for voluntary eye blinking, whereas the medial/superior frontal, precentral, cingulate, precuneus, and superior temporal gyrus appears to be involved in inhibited eye blinking. Based on these experimental results, we propose that the precentral gyrus is responsible for both voluntary and inhibited eye blinking. The parietal area (precuneus and superior temporal gyrus) appears to be exclusively related to inhibited eye blinking.     

Distinct cortical anatomy linked to subregions of the medial temporal lobe revealed by intrinsic functional connectivity

The hippocampus and adjacent cortical structures in the medial temporal lobe (MTL) contribute to memory through interactions with distributed brain areas. Studies of monkey and rodent anatomy suggest that parallel pathways converge on distinct subregions of the MTL. To explore the cortical areas linked to subregions of the MTL in humans, we examined cortico-cortical and hippocampal-cortical correlations using high-resolution, functional connectivity analysis in 100 individuals. MTL seed regions extended along the anterior to posterior axis and included hippocampus and adjacent structures. Results revealed two separate brain pathways that correlated with distinct subregions within the MTL. The body of the hippocampus and posterior parahippocampal cortex correlated with lateral parietal cortex, regions along the posterior midline including posterior cingulate and retrosplenial cortex, and ventral medial prefrontal cortex. By contrast, anterior hippocampus and the perirhinal/entorhinal cortices correlated with distinct regions in the lateral temporal cortex extending into the temporal pole. The present results are largely consistent with known connectivity in the monkey and provide a novel task-independent dissociation of the parallel pathways supporting the MTL memory system in humans. The cortical pathways include regions that have undergone considerable areal expansion in humans, providing insight into how the MTL memory system has evolved to support a diverse array of cognitive domains.     

Multi-modal imaging predicts memory performance in normal aging and cognitive decline

This study (n=161) related morphometric MR imaging, FDG-PET and APOE genotype to memory scores in normal controls (NC), mild cognitive impairment (MCI) and Alzheimer's disease (AD). Stepwise regression analyses focused on morphometric and metabolic characteristics of the episodic memory network: hippocampus, entorhinal, parahippocampal, retrosplenial, posterior cingulate, precuneus, inferior parietal, and lateral orbitofrontal cortices. In NC, hippocampal metabolism predicted learning; entorhinal metabolism predicted recognition; and hippocampal metabolism predicted recall. In MCI, thickness of the entorhinal and precuneus cortices predicted learning, while parahippocampal metabolism predicted recognition. In AD, posterior cingulate cortical thickness predicted learning, while APOE genotype predicted recognition. In the total sample, hippocampal volume and metabolism, cortical thickness of the precuneus, and inferior parietal metabolism predicted learning; hippocampal volume and metabolism, parahippocampal thickness and APOE genotype predicted recognition. Imaging methods appear complementary and differentially sensitive to memory in health and disease. Medial temporal and parietal metabolism and morphometry best explained memory variance. Medial temporal characteristics were related to learning, recall and recognition, while parietal structures only predicted learning.     

Coherent spontaneous activity identifies a hippocampal-parietal memory network

Despite traditional theories emphasizing parietal contributions to spatial attention and sensory-motor integration, functional MRI (fMRI) experiments in normal subjects suggest that specific regions within parietal cortex may also participate in episodic memory. Here we examined correlations in spontaneous blood-oxygenation-level-dependent (BOLD) signal fluctuations in a resting state to identify the network associated with the hippocampal formation (HF) and determine whether parietal regions were elements of that network. In the absence of task, stimuli, or explicit mnemonic demands, robust correlations were observed between activity in the HF and several parietal regions (including precuneus, posterior cingulate, retrosplenial cortex, and bilateral inferior parietal lobule). These HF-correlated regions in parietal cortex were spatially distinct from those correlated with the motion-sensitive MT+ complex. Reanalysis of event-related fMRI studies of recognition memory showed that the regions spontaneously correlated with the HF (but not MT+) were also modulated during directed recollection. These regions showed greater activity to successfully recollected items as compared with other trial types. Together, these results associate specific regions of parietal cortex that are sensitive to successful recollection with the HF.     

Hippocampal function and spatial memory: evidence from functional neuroimaging in healthy participants and performance of patients with medial temporal lobe resections

Several strategies can be used to find a destination in the environment. Using a virtual environment, the authors identified 2 strategies dependent on 2 different memory systems. A spatial strategy involved the use of multiple landmarks available in the environment, and a response strategy involved right and left turns from a given start position. Although a probe trial provided an objective measure of the strategy used, classification that was based on verbal reports was used in small groups to avoid risks of misclassification. The authors first demonstrated that the spatial strategy led to a significant activity of the hippocampus, whereas the response strategy led to a sustained activity in the caudate nucleus. Then, the authors administered the task to 15 patients with lesions to the medial temporal lobe, showing an impaired ability using the spatial strategy. Imaging and neuropsychological results are discussed to shed light on the human navigation system.     

Brain activation during human navigation: gender-different neural networks as substrate of performance

Visuospatial navigation in animals and human subjects is generally studied using maze exploration. We used functional MRI to observe brain activation in male and female subjects as they searched for the way out of a complex, three-dimensional, virtual-reality maze. Navigation activated the medial occipital gyri, lateral and medial parietal regions, posterior cingulate and parahippocampal gyri as well as the right hippocampus proper. Gender-specific group analysis revealed distinct activation of the left hippocampus in males, whereas females consistently recruited right parietal and right prefrontal cortex. Thus we demonstrate a neural substrate of well established human gender differences in spatial-cognition performance.     

Structural brain plasticity in Parkinson's disease induced by balance training

We investigated morphometric brain changes in patients with Parkinson's disease (PD) that are associated with balance training. A total of 20 patients and 16 healthy matched controls learned a balance task over a period of 6 weeks. Balance testing and structural magnetic resonance imaging were performed before and after 2, 4, and 6 training weeks. Balance performance was re-evaluated after ∼20 months. Balance training resulted in performance improvements in both groups. Voxel-based morphometry revealed learning-dependent gray matter changes in the left hippocampus in healthy controls. In PD patients, performance improvements were correlated with gray matter changes in the right anterior precuneus, left inferior parietal cortex, left ventral premotor cortex, bilateral anterior cingulate cortex, and left middle temporal gyrus. Furthermore, a TIME × GROUP interaction analysis revealed time-dependent gray matter changes in the right cerebellum. Our results highlight training-induced balance improvements in PD patients that may be associated with specific patterns of structural brain plasticity. In summary, we provide novel evidence for the capacity of the human brain to undergo learning-related structural plasticity even in a pathophysiological disease state such as in PD.     

Impairments in cognition and resting-state connectivity of the hippocampus in elderly subjects with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of Alzheimer's disease, which involves hippocampus-mediated cognitive impairment. The present study investigated whether the resting-state functional connectivity of the hippocampus would be changed in patients with T2DM. A region of interest-based resting-state functional magnetic resonance imaging (fMRI) approach was applied to explore functional connectivity differences between 21 elderly patients with T2DM and 19 well-matched healthy controls, with all participants assessed by multi-dimensional neuropsychological tests. We found that T2DM patients performed significantly worse in the Auditory Verbal Learning Test (AVLT) (especially for Delayed Recall and Recognition) and Clock Drawing Test (CDT) when compared with the control group, and cognitive function was negatively related to BMI and HbA_1c. Importantly, the hippocampus showed reduced functional connectivity bilaterally to widespread regions, including fusiform gyrus, frontal gyrus, temporal gyrus, anterior cingulate gyrus, medial frontal gyrus, posterior cingulate gyrus, precuneus and inferior parietal lobule in T2DM patients compared to healthy controls. T2DM is associated with an impaired pattern of default network function, and the specific disconnection pattern identified may be involved in the neuropathophysiology of this disease.     

Hippocampal contribution to early and later stages of implicit motor sequence learning

Implicit motor sequence learning refers to an important human ability to acquire new motor skills through the repeated performance of a motor sequence. This learning process is characterized by slow, incremental gains of motor performance. The present fMRI study was developed to better delineate the areas supporting these temporal dynamics of learning. By using the serial color matching paradigm, our study focused on the motor level of sequence learning and tracked the time course of learning-related neural changes. Imaging results showed a significant contribution of the left anterior hippocampus in an early sequence acquisition stage (first scanning session) as well as during a later stage with stabilized learning effects (second scanning session). Hippocampal activation significantly correlated with the behavioral learning process and was affected by a change of the motor sequence. These results suggest a strong involvement of the hippocampus in implicit motor sequence learning. On the other hand, a very extensive and bilateral neural network of parietal, temporal and frontal cortical areas (including SMA, pre-SMA) together with parts of the cerebellum and striatum were found to play a role during random visuo-motor task performance.     

Age differences in the neural systems supporting human allocentric spatial navigation

Age-related declines in spatial navigation are well-known in human and non-human species. Studies in non-human species suggest that alteration in hippocampal and other neural circuitry may underlie behavioral deficits associated with aging but little is known about the neural mechanisms of human age-related decline in spatial navigation. The purpose of the present study was to examine age differences in functional brain activation during virtual environment navigation. Voxel-based analysis of activation patterns in young subjects identified activation in the hippocampus and parahippocampal gyrus, retrosplenial cortex, right and left lateral parietal cortex, medial parietal lobe and cerebellum. In comparison to younger subjects, elderly participants showed reduced activation in the hippocampus and parahippocampal gyrus, medial parietal lobe and retrosplenial cortex. Relative to younger participants elderly subjects showed increased activation in anterior cingulate gyrus and medial frontal lobe. These results provide evidence of age specific neural networks supporting spatial navigation and identify a putative neural substrate for age-related differences in spatial memory and navigational skill.     

On the multivariate nature of brain metabolic impairment in Alzheimer's disease

We used principal component analysis to decompose functional images of patients with AD in orthogonal ensembles of brain regions with maximal metabolic covariance. Three principal components explained 38% of the total variance in a large sample of FDG-PET images obtained in 225 AD patients. One functional ensemble (PC2) included limbic structures from Papez's circuit (medial temporal regions, posterior and anterior cingulate cortex, thalamus); its disruption in AD patients was related to episodic memory impairment. Another principal component (PC1) illustrated major metabolic variance in posterior cerebral cortices, and patients' scores were correlated to instrumental functions (language and visuospatial abilities). PC3 comprised frontal, parietal, temporal and posteromedial (posterior cingulate and precuneus) cortices, and patients' scores were related to executive dysfunction and global cognitive impairment. The three main metabolic covariance networks converged in the posterior cingulate area that showed complex relationships with medial temporal structures within each PC. Individual AD scores were distributed as a continuum along PC axes: an individual combination of scores would determine specific clinical symptoms in each patient.