眼固视成分分离的研究现状及应用进展

背景：研究表明,固视期间的眼动,不仅包含了来自神经系统的噪声信号,而且包含认知加工的信息,固视成分及其功能的研究也日益引起重视。目的：综述固视成分分离的研究现状及进展。方法：分别以“visualfixation,fixationaleyemovement,tremor．drifts,microsaccades”为关键词,利用计算机检索1980至2012年PebMed数据库,并使用Google学术进行相关文献搜索,以及参考相应专著,排除内容重复、无关及缺乏原创性的文献,保留64篇文献做进一步分析。结果与结论：固视是个体的眼睛保持对准被观察物体的一种现象,伴随有微颤、漂移和微跳视3种眼动成分,它们是维持视知觉的重要条件。近年来,研究者针对固视3种成分对视知觉的贡献进行了探讨,主要包括防止知觉消退和对视觉系统进行纠错两种观点。目前,研究者通过对眼动速度阈限的估计来分离微跳视成分。未来的研究可以从固视眼动的神经生理基础以及神经活动的记录技术和视网膜固定技术的提高等方面展开,从而加深对固视眼动现象的理解。     

Effects of estrogen on patterns of brain activity at rest and during cognitive activity: a review of neuroimaging studies

Animal and human studies provide evidence of systematic effects of estrogen on cerebral activity and cognitive function. In this article, we review studies of the activational effects of estrogen on cerebral activity during rest and during the performance of cognitive tasks in pre- and postmenopausal women. The goal is twofold--to better understand evidence suggesting that estrogen influences brain functioning and argue for the importance of considering hormone effects when designing neuroimaging studies. Hormone-related increases in blood flow during the resting state have been documented in healthy elderly women, elderly women with cerebrovascular disease, and middle-aged postmenopausal women with early menopause. There is no reliable influence of estrogen on blood flow during the resting state in women with Alzheimer's disease. Hormone therapy has been associated with changes in brain activation patterns in middle-aged and elderly postmenopausal women during performance of verbal and figural memory tasks, providing critical biological support for the view that estrogen might protect against age-associated changes in cognition and lower the risk of Alzheimer's disease. There is a paucity of studies examining changes in brain activation patterns across the menstrual cycle and a need for randomized studies of hormone therapy in postmenopausal women to confirm findings from observational studies. General procedural guidelines for controlling and investigating hormone effects in neuroimaging studies are discussed.     

REM Sleep Behavior Disorder: Diagnosis,Clinical Implications,and Future Directions

Rapid eye movement sleep behavior disorder (RBD) is diagnosed by a clinical history of dream enactment accompanied by polysomnographic rapid eye movement sleep atonia loss (rapid eye movement sleep without atonia). Rapid eye movement sleep behavior disorder is strongly associated with neurodegenerative disease, especially synucleinopathies such as Parkinson disease, dementia with Lewy bodies, and multiple system atrophy. A history of RBD may begin several years to decades before onset of any clear daytime symptoms of motor, cognitive, or autonomic impairments, suggesting that RBD is the presenting manifestation of a neurodegenerative process. Evidence that RBD is a synlucleinopathy includes the frequent presence of subtle prodromal neurodegenerative abnormalities including hyposmia, constipation, and orthostatic hypotension, as well as abnormalities on various neuroimaging, neurophysiological, and autonomic tests. Up to 90.9% of patients with idiopathic RBD ultimately develop a defined neurodegenerative disease over longitudinal follow-up, although the prognosis for younger patients and antidepressant-associated RBD is less clear. Patients with RBD should be treated with either melatonin 3 to 12 mg or clonazepam 0.5 to 2.0 mg to reduce injury potential. Prospective outcome and treatment studies of RBD are necessary to enable accurate prognosis and better evidence for symptomatic therapy and future neuroprotective strategies.     

Mental rotation and object categorization share a common network of prefrontal and dorsal and ventral regions of posterior cortex

The multiple-views-plus-transformation variant of object model verification theories predicts that parietal regions that are critical for mental rotation contribute to visual object cognition. Some neuroimaging studies have shown that the intraparietal sulcus region is critically involved in mental rotation. Other studies indicate that both ventral and dorsal posterior regions are object-sensitive and involved in object perception and categorization tasks. However, it is unknown whether dorsal object-sensitive areas overlap with regions recruited for object mental rotation. Functional magnetic resonance imaging was used to test this directly. Participants performed standard tasks of object categorization, mental rotation, and eye movements. Results provided clear support for the prediction, demonstrating overlap between dorsal object-sensitive regions in ventral-caudal intraparietal sulcus (vcIPS) and an adjacent dorsal occipital area and the regions that are activated during mental rotation but not during saccades. In addition, object mental rotation (but not saccades) activated object-sensitive areas in lateral dorsal occipitotemporal cortex (DOT), and both mental rotation and object categorization recruited ventrolateral prefrontal cortex areas implicated in attention, working memory, and cognitive control. These findings provide clear evidence that a prefrontal-posterior cortical system implicated in mental rotation, including the occipitoparietal regions critical for this spatial task, is recruited during visual object categorization. Altogether, the findings provide a key link in understanding the role of dorsal and ventral visual areas in spatial and object perception and cognition: Regions in occipitoparietal cortex, as well as DOT cortex, have a general role in visual object cognition, supporting not only mental rotation but also categorization.     

Intracerebral dynamics of saccade generation in the human frontal eye field and supplementary eye field

Recent functional imaging and electrical stimulation studies have localized in humans two frontal regions critical for the production of saccadic and anti-saccadic eye movements: the frontal and supplementary eye fields (FEF and SEF, respectively). We investigated the time course of their activations during the generation of pro- and anti-saccades from direct intracranial EEG recordings of three human epileptic patients. We found the preparation and the production of the saccades to be coincident with focal and transient increases of EEG power above 60 Hz. Those were produced in very specific brain sites distributed in the FEF and the SEF (as identified by previous human studies at a coarser time resolution). Furthermore, the spatio-temporal resolution of those recordings turned out to be sufficient to discriminate anatomically between several types of neural responses, determined either by the visual or by the motor components of the saccade tasks, and within this second category of responses, between some associated with the preparation of the saccades and others associated with their execution. Altogether, this study provides the first evidence of high-frequency neural responses in the generation of saccades in humans, and provides a firm basis for other studies detailing further the functional organization of the human oculomotor system at this level of spatial and temporal resolution.     

Category-specific activations during word generation reflect experiential sensorimotor modalities

According to the sensorimotor theory of lexicosemantic organization, semantic representations are neurally distributed and anatomically linked to category-specific sensory areas. Previous functional neuroimaging studies have demonstrated category specificity in lexicosemantic representations. However, little evidence is available from word generation paradigms, which provide access to semantic representations while minimizing confounds resulting from low-level perceptual features of stimulus presentation. In this study, 13 healthy young adults underwent fMRI scanning while performing a word generation task, generating exemplars to nine different semantic categories. Each semantic category was assigned to one of three superordinate category types, based upon sensorimotor modalities (visual, motor, somatosensory) presumed to predominate in lexical acquisition. For word generation overall, robust activation was seen in left inferior frontal cortex. Analyses by sensorimotor modality categories yielded activations in brain regions related to perceptual and motor processing: Visual categories activated extrastriate cortex, motor categories activated the intraparietal sulcus and posterior middle temporal cortex, and somatosensory categories activated postcentral and inferior parietal regions. Our results are consistent with the sensorimotor theory, according to which lexicosemantic representations are distributed across brain regions participating in sensorimotor processing associated with the experiential components of lexicosemantic acquisition.     

Occipital gamma-oscillations modulated during eye movement tasks: simultaneous eye tracking and electrocorticography recording in epileptic patients

We determined the spatio-temporal dynamics of cortical gamma-oscillations modulated during eye movement tasks, using simultaneous eye tracking and intracranial electrocorticography (ECoG) recording. Patients with focal epilepsy were instructed to follow a target moving intermittently and unpredictably from one place to another either in an instantaneous or smooth fashion during extraoperative ECoG recording. Target motion elicited augmentation of gamma-oscillations in the lateral, inferior and polar occipital regions in addition to portions of parietal and frontal regions; subsequent voluntary eye movements elicited gamma-augmentation in the medial occipital region. Such occipital gamma-augmentations could not be explained by contaminations of ocular or myogenic artifacts. The degree of gamma-augmentation was generally larger during saccade compared to pursuit trials, while a portion of the polar occipital region showed pursuit-preferential gamma-augmentations. In addition to the aforementioned eye movement task, patients were asked to read a single word popping up on the screen. Gamma-augmentation was elicited in widespread occipital regions following word presentation, while gamma-augmentation in the anterior portion of the medial occipital region was elicited by an involuntary saccade following word presentation rather than word presentation itself. Gamma-augmentation in the lateral, inferior and polar occipital regions can be explained by increased attention to a moving target, whereas gamma-augmentation in the anterior-medial occipital region may be elicited by images in the peripheral field realigned following saccades. In functional studies comparing brain activation between two tasks, eye movement patterns during tasks may need to be considered as confounding factors.     

The encoding of saccadic eye movements within human posterior parietal cortex

Over the last few years, several functionally distinct subregions of the posterior parietal cortex (PPC) have been shown to subserve oculomotor control. Since these areas seem to overlap with regions whose activation is related to attention, we used functional magnetic resonance imaging to compare the cerebral activation pattern evoked by eye movements with different attentional loads, i.e., oscillatory saccades with different frequencies, as well as predictable, and unpredictable saccades. Our results show activation in largely overlapping networks with differing strength of activity and symmetry of involved areas. Predictable saccades having the shortest saccadic latency led to the most pronounced cerebral activity both in terms of cortical areas involved and signal intensity. Predictable and unpredictable saccades were dominated by activation within the right hemisphere, whereas oscillatory saccades showing the longest saccadic latency were dominated by activation within the left hemisphere. In all tasks, the centers of gravity of activation occurred within the posterior part of the intraparietal sulcus (IPS), while the predictable saccades additionally activated its anterior part. The enhanced activity during the execution of predictable saccades was probably related to top-down processing and/or the preparation of the upcoming eye movement. The hemispheric difference could arise from a predominant role of the right PPC for shifting spatial attention and the left PPC for shifting temporal attention. The differential encoding of saccadic eye movements within IPS indicates that the PPC splits up into different functional modules related to the particular demands of a saccade.     

Comparing eye movements recorded by search coil and infrared eye tracking

OBJECTIVE: The performance of a new video-based infrared eye tracker (IR) was compared to the magnetic search coil technique (SC). Since the IR offers interesting possibilities as a diagnostic tool in neuro-ophthalmology, it was investigated whether the new device has overcome shortcomings that were reported from former IR systems. METHODS: Horizontal saccades were recorded using the IR and the SC. The IR allowed eye movement recordings at different sampling rates ranging from 250 Hz to 1000 Hz while the SC recorded at 1000 Hz. RESULTS/CONCLUSIONS: The results show that the IR and the SC were in good agreement and produced similar results. In contrast to other studies, the influence of the sampling rate of the IR was small. The saccade main-sequences did not show significant differences. The latency times observed for both systems were mainly in the short-latency range.     

Inserting Needles Into the Body: A Meta-Analysis of Brain Activity Associated With Acupuncture Needle Stimulation

Acupuncture is a therapeutic treatment that is defined as the insertion of needles into the body at specific points (ie, acupoints). Advances in functional neuroimaging have made it possible to study brain responses to acupuncture; however, previous studies have mainly concentrated on acupoint specificity. We wanted to focus on the functional brain responses that occur because of needle insertion into the body. An activation likelihood estimation meta-analysis was carried out to investigate common characteristics of brain responses to acupuncture needle stimulation compared to tactile stimulation. A total of 28 functional magnetic resonance imaging studies, which consisted of 51 acupuncture and 10 tactile stimulation experiments, were selected for the meta-analysis. Following acupuncture needle stimulation, activation in the sensorimotor cortical network, including the insula, thalamus, anterior cingulate cortex, and primary and secondary somatosensory cortices, and deactivation in the limbic-paralimbic neocortical network, including the medial prefrontal cortex, caudate, amygdala, posterior cingulate cortex, and parahippocampus, were detected and assessed. Following control tactile stimulation, weaker patterns of brain responses were detected in areas similar to those stated above. The activation and deactivation patterns following acupuncture stimulation suggest that the hemodynamic responses in the brain simultaneously reflect the sensory, cognitive, and affective dimensions of pain.PerspectiveThis article facilitates a better understanding of acupuncture needle stimulation and its effects on specific activity changes in different brain regions as well as its relationship to the multiple dimensions of pain. Future studies can build on this meta-analysis and will help to elucidate the clinically relevant therapeutic effects of acupuncture.     

Structural brain correlates of prepulse inhibition of the acoustic startle response in healthy humans

Neural regions modulating prepulse inhibition (PPI) of the startle response, an operational measure of sensorimotor gating, are well established from animal studies using surgical and pharmacological procedures. The limbic and cortico-pallido-striato-thalamic circuitry is thought to be responsible for modulation of PPI in the rat. The involvement of this circuitry in human PPI is suggested by observations of deficient PPI in a number of neuropsychiatric disorders characterized by abnormalities at some level in this circuitry and recent functional neuroimaging studies in humans. The current study sought to investigate structural neural correlates of PPI in a sample of twenty-four right-handed, healthy subjects (10 men, 14 women). Subjects underwent magnetic resonance imaging (MRI) at 1.5 T and were assessed (off-line) on acoustic PPI using electromyographic recordings of the orbicularis oculi muscle beneath the right eye. Optimized volumetric voxel-based morphometry (VBM) implemented in SPM99 was used to investigate the relationship of PPI (prepulse onset-to-pulse onset interval 120 ms) to regional grey matter volumes, covarying for sex. Significant positive correlations were obtained between PPI and grey matter volume in the hippocampus extending to parahippocampal gyrus, basal ganglia including parts of putamen, globus pallidus, and nucleus accumbens, superior temporal gyrus, thalamus, and inferior frontal gyrus. These findings identify the relationship between PPI and grey matter availability on a highly spatially localized scale in brain regions shown to be activated in recent functional neuroimaging studies in association with PPI in healthy humans and demonstrate the validity of structural neuroimaging methods in delineating the neural mechanisms underlying human PPI.     

Venomous fish stings on the European seashore

Abstract

Background: Cerebral palsy is a nonprogressive brain disorder associated with lifelong motor impairments and often with cognitive deficits, impaired communication, and impaired sensory perception. Vision deficits, in particular, occur frequently in cerebral palsy and can lead to reading difficulties. Objective: Investigate the extent to which the motor impairments in this clinical group affect patients' ability to read. Methods: An eye-tracking system was used to record the eye movements during a reading task in 31 adults diagnosed with cerebral palsy and in 10 healthy controls. Participants were asked to read out loud 1 to 5 excerpts from children's books. Results: In comparison to the healthy readers, cerebral palsy patients took longer to read the excerpts; made more saccades, fixations, and regressions; and made shorter saccades. Average fixation times were similar between the 2 groups, but the average saccade duration was significantly longer for the cerebral palsy group, as a function of the degree of severity of motor impairment. The latter was not a determinant of the level of text comprehension achieved by these patients. Conclusions: Objective measures of eye movement during a reading task can be obtained in cerebral palsy patients using eye-tracking techniques. Results suggest that cerebral palsied patients may experience difficulties in searching for words during reading.     

Functional neuroimaging and cognitive rehabilitation for people with traumatic brain injury

Cognitive deficits are a common consequence of traumatic brain injury. Although such deficits are amenable to rehabilitation, methods for individualizing cognitive interventions are still unrefined. Functional neuroimaging methods such as positron emission tomography and functional magnetic resonance imaging are emerging as possible technologies for measuring and monitoring the cerebral consequences of plasticity associated with brain injury and for evaluating the effectiveness of rehabilitation interventions. Functional neuroimaging may even enable more customized and efficient selection, design, or adaptation of individual cognitive rehabilitation programs. We review the current literature on functional neuroimaging after traumatic brain injury, relating these findings to cognitive rehabilitation. Overall, functional neuroimaging after traumatic brain injury has shown reliable differences in brain activity within several regions of frontal cortex, partly but not uniformly consistent with neuropsychological and structural findings in traumatic brain injury. We also outline a number of promising research opportunities for applying functional neuroimaging in traumatic brain injury settings, along with associated challenges.     

网络游戏成瘾的认知功能和神经影像学研究进展

互联网科技快速发展之下,网络游戏成瘾（IGD）已经成为全球性心理健康问题。目前大多数关于IGD的研究主要集中在奖赏系统、抑制控制及跨期决策3个方面。随着认知神经科学的发展,采用脑电图（EEG）、MRI和PET等技术探讨IGD的神经机制已成为主流。与健康对照者相比,IGD者脑结构和功能均发生相应变化,且大脑损害程度与成瘾行为的持续时间有关。本文对近年来有关IGD的认知功能及其神经影像学研究进展进行综述,重点介绍其研究方法和相应结果,为进一步探索该领域及相关研究拓展思路。     

Dissociating the spatio-temporal characteristics of cortical neuronal activity associated with human volitional swallowing in the healthy adult brain

Human swallowing represents a complex highly coordinated sensorimotor function whose functional neuroanatomy remains incompletely understood. Specifically, previous studies have failed to delineate the temporo-spatial sequence of those cerebral loci active during the differing phases of swallowing. We therefore sought to define the temporal characteristics of cortical activity associated with human swallowing behaviour using a novel application of magnetoencephalography (MEG). In healthy volunteers (n = 8, aged 28-45), 151-channel whole cortex MEG was recorded during the conditions of oral water infusion, volitional wet swallowing (5 ml bolus), tongue thrust or rest. Each condition lasted for 5 s and was repeated 20 times. Synthetic aperture magnetometry (SAM) analysis was performed on each active epoch and compared to rest. Temporal sequencing of brain activations utilised time-frequency wavelet plots of regions selected using virtual electrodes. Following SAM analysis, water infusion preferentially activated the caudolateral sensorimotor cortex, whereas during volitional swallowing and tongue movement, the superior sensorimotor cortex was more strongly active. Time-frequency wavelet analysis indicated that sensory input from the tongue simultaneously activated caudolateral sensorimotor and primary gustatory cortex, which appeared to prime the superior sensory and motor cortical areas, involved in the volitional phase of swallowing. Our data support the existence of a temporal synchrony across the whole cortical swallowing network, with sensory input from the tongue being critical. Thus, the ability to non-invasively image this network, with intra-individual and high temporal resolution, provides new insights into the brain processing of human swallowing.     

VALIDITY OF AN MRI-COMPATIBLE MOTION CAPTURE SYSTEM FOR USE WITH LOWER EXTREMITY NEUROIMAGING PARADIGMS

Background:Emergent linkages between musculoskeletal injury and the nervous system have increased interest to evaluate brain activity during functional movements associated with injury risk. Functional magnetic resonance imaging (fMRI) is a sophisticated modality that can be used to study brain activity during functional sensorimotor control tasks. However, technical limitations have precluded the precise quantification of lower-extremity joint kinematics during active brain scanning. The purpose of this study was to determine the validity of a new, MRI-compatible motion tracking system relative to a traditional multi-camera 3D motion capture system for measuring lower extremity joint kinematics.Methods:Fifteen subjects (9 females, 6 males) performed knee flexion-extension and leg press movements against guided resistance while laying supine. Motion tracking data were collected simultaneously using the MRI-compatible and traditional multi-camera 3D motion systems. Participants’ sagittal and frontal plane knee angles were calculated from data acquired by both multi-camera systems. Resultant range of angular movement in both measurement planes were compared between both systems. Instrument agreement was assessed using Bland-Altman plots and intraclass correlation coefficients (ICC).Results:The system demonstrated excellent validity in the sagittal plane (ICCs>0.99) and good to excellent validity in the frontal plane (0.84 < ICCs < 0.92). Mean differences between corresponding range of angular movement measurements ranged from 0.186 ° to 0.295 °.Conclusions:The present data indicate that this new, MRI-compatible system is valid for measuring lower extremity movements when compared to the gold standard 3D motion analysis system. As there is growing interest regarding the neural substrates of lower extremity movement, particularly in relation to injury and pathology, this system can now be integrated into neuroimaging paradigms to investigate movement biomechanics and its relation to brain activity.Level of Evidence:3     

2型糖尿病认知障碍患者的磁共振成像研究进展

2型糖尿病(type 2 diabetes mellitus,T2DM)会导致大脑结构和功能异常,增加认知障碍的风险.但是,目前我们对T2DM认知障碍发病机理仍不清楚.而磁共振成像研究的进展进一步确定了T2DM导致认知障碍的相关神经因素.我们系统地回顾了有关T2DM患者神经影像学改变的文献,这些改变包括结构、大脑功能以...     

Functional topography in the human cerebellum: a meta-analysis of neuroimaging studies

Clinical, experimental and neuroimaging studies indicate that the cerebellum is involved in neural processes beyond the motor domain. Cerebellar somatotopy has been shown for motor control, but topographic organization of higher-order functions has not yet been established. To determine whether existing literature supports the hypothesis of functional topography in the human cerebellum, we conducted an activation likelihood estimate (ALE) meta-analysis of neuroimaging studies reporting cerebellar activation in selected task categories: motor (n=7 studies), somatosensory (n=2), language (n=11), verbal working memory (n=8), spatial (n=8), executive function (n=8) and emotional processing (n=9). In agreement with previous investigations, sensorimotor tasks activated anterior lobe (lobule V) and adjacent lobule VI, with additional foci in lobule VIII. Motor activation was in VIIIA/B; somatosensory activation was confined to VIIIB. The posterior lobe was involved in higher-level tasks. ALE peaks were identified in lobule VI and Crus I for language and verbal working memory; lobule VI for spatial tasks; lobules VI, Crus I and VIIB for executive functions; and lobules VI, Crus I and medial VII for emotional processing. Language was heavily right-lateralized and spatial peaks left-lateralized, reflecting crossed cerebro-cerebellar projections. Language and executive tasks activated regions of Crus I and lobule VII proposed to be involved in prefrontal-cerebellar loops. Emotional processing involved vermal lobule VII, implicated in cerebellar-limbic circuitry. These data provide support for an anterior sensorimotor vs. posterior cognitive/emotional dichotomy in the human cerebellum. Prospective studies of multiple domains within single individuals are necessary to better elucidate neurobehavioral structure-function correlations in the cerebellar posterior lobe.     

Ocular motor measures in migraine with and without aura

The purpose of this study was to examine basic ocular motor function in individuals with migraine. We used an infrared eye-tracking system to measure horizontal smooth pursuit to a sinusoidal target, saccades to horizontal target displacements of 5-20 degrees , and the stability of fixation in 19 migraine without aura (MoA), 19 migraine with aura (MA) and 19 headache-free control (C) subjects. Eye movement measurements were made at two target displacement rates and against both homogeneous grey and patterned backgrounds. We found no statistically significant differences between migraine and control subjects in any of the eye movement parameters measured, but did find highly significant effects of both target speed and background pattern in all groups. Our results do not provide support for subclinical cerebellar impairment in migraineurs, and do provide evidence that previously described visual abnormalities in migraine are not artefacts of abnormal fixation or eye movements.     

Brain activation during smooth-pursuit eye movements

A potential application of studying eye movements with functional MRI (fMRI) is to examine patient populations with known eye movement dysfunction, but the reliability with which normal subjects demonstrate activity in specific brain regions has not been established. To date, fMRI studies of smooth-pursuit eye movements have used relatively small numbers of subjects and have been restricted to fixed-effects analyses. We extend these studies to whole brain imaging at 1.5 T, properly accounting for intersubject variation using random effects analysis. Smooth-pursuit eye movements elicited activation consistently in dorsal cortical eye fields and cerebellum. Subcortical activation was greatly attenuated, but not eliminated, with the random-effects second-level analysis. In addition, session-dependent changes in activation were greater in some regions than others and may indicate areas of brain, such as the supplementary eye fields, that are sensitive to attentional modulation of eye movements.