综述: 知觉相关的神经振荡-外界节律同步化现象

具有特定频率的节律性刺激能同步大脑内相应频率的神经振荡,使神经活动与外界刺激发生相位锁定,称之为神经振荡-外界节律同步化(neural entrainment).这种同步化的现象伴随着大脑内神经元集群兴奋水平的周期性波动,并与节律信息加工、知觉及注意等认知过程存在关联.得益于其非侵入、易操作以及能有效调控神经活动的特性,神经振荡-外界节律同步化成为了研究神经振荡与知觉和认知功能关系的有力手段,也为认知障碍诊断及干预提供了新的思路和方法.     

Attention Wins over Sensory Attenuation in a Sound Detection Task

‘Sensory attenuation’, i.e., reduced neural responses to self-induced compared to externally generated stimuli, is a well-established phenomenon. However, very few studies directly compared sensory attenuation with attention effect, which leads to increased neural responses. In this study, we brought sensory attenuation and attention together in a behavioural auditory detection task, where both effects were quantitatively measured and compared. The classic auditory attention effect of facilitating detection performance was replicated. When attention and sensory attenuation were both present, attentional facilitation decreased but remained significant. The results are discussed in the light of current theories of sensory attenuation.     

The neurobiology of visual attention: finding sources

The profusion of progress during the past twenty years in identifying neural correlates of selective attention within the visual system has left open the question of how visual representations are biased to favor target stimuli. Studies aimed at specifying the mechanisms that can be causally implicated in the control of visual selective attention have only recently begun in earnest. Employing both the psychophysical and the neuroanatomical data, recent neurophysiological experiments in monkeys and neuroimaging studies in humans are converging on the neural circuits that provide the source of at least some forms of attentional control signals.     

Visual attention: light enters the jungle

Recent studies focusing on basic visual attributes, such as luminance, colour and motion, are providing a starting point for investigating the relationship between perceptual and neural manifestations of attention.     

The origin and evolution of the neural crest

Many of the features that distinguish the vertebrates from other chordates are derived from the neural crest, and it has long been argued that the emergence of this multipotent embryonic population was a key innovation underpinning vertebrate evolution. More recently, however, a number of studies have suggested that the evolution of the neural crest was less sudden than previously believed. This has exposed the fact that neural crest, as evidenced by its repertoire of derivative cell types, has evolved through vertebrate evolution. In this light, attempts to derive a typological definition of neural crest, in terms of molecular signatures or networks, are unfounded. We propose a less restrictive, embryological definition of this cell type that facilitates, rather than precludes, investigating the evolution of neural crest. While the evolutionary origin of neural crest has attracted much attention, its subsequent evolution has received almost no attention and yet it is more readily open to experimental investigation and has greater relevance to understanding vertebrate evolution. Finally, we provide a brief outline of how the evolutionary emergence of neural crest potentiality may have proceeded, and how it may be investigated.     

综述: 无创穿颅电刺激对人脑神经活动和认知功能的调控

穿颅电刺激被认为可以无创调节大脑的神经活动,为研究特定脑区与某一认知功能间的因果关系提供了可能.近些年,对穿颅电刺激作用机制和其对认知、运动功能调控的研究方面取得了很多重要进展.在这篇综述中,我们总结了以往关于穿颅直流电刺激、穿颅交流电刺激和穿颅随机噪声电刺激三种刺激方式的发展历史及其作用机制,同时总结了其对感知觉(主要是视觉知觉)、注意和记忆等认知功能的调控,并对未来的研究方向进行了展望.     

The neurobiology of selective attention.

Research in the field of selective visual attention has recently seen substantial progress in several areas. Neuroimaging and electrical recording results have indicated that selective attention amplifies neural activity in prestriate areas concerned with basic visual processing. Imaging and cellular studies are delineating the networks of anatomical areas that serve as the source of attentional modulation and have suggested that these networks are anatomically distinct from the sites of the resulting amplifications. Cognitive studies of visual search have explored the role of these amplified computations in the integration of visual features into objects. Attentional effects in normal subjects, and their disruption following brain injury, have revealed the mental representations upon which attention operates.     

Auditory attention--focusing the searchlight on sound

Some fifty years after the first physiological studies of auditory attention, the field is now ripening, with exciting recent insights into the psychophysics, psychology, and neural basis of auditory attention. Current research seeks to unravel the complex interactions of pre-attentive and attentive processing of the acoustic scene, the role of auditory attention in mediating receptive-field plasticity in both auditory spatial and auditory feature processing, the contrasts and parallels between auditory and visual attention pathways and mechanisms, the interplay of bottom-up and top-down attentional mechanisms, the influential role of attention, goals, and expectations in shaping auditory processing, and the orchestration of diverse attentional effects at multiple levels from the cochlea to the cortex.     

Shifting baselines in attention research

Psychophysical and physiological studies have shown that attending to a stimulus can enhance its sensory processing. Functional imaging studies now reveal that attention can also modulate activity in sensory brain areas before stimulus onset, when the observer prepares to attend to an anticipated stimulus. These preparatory 'baseline shifts' in brain activity pose many new questions, and potentially offer new insights into the neural basis of perceptual awareness.     

视觉注意与神经振荡

人脑每时每刻都要接收大量视觉信息，由于人脑加工信息的能力有限，所以在较大视野内将注意分配给相关信息，同时抑制引起注意分散的不相关信息，对执行目标导向的行为至关重要。这种对视觉信息的选择性和主动性加工以适应当前目标的过程被称作视觉注意（visual attention），且视觉注意可分为自上而下的注意与自下而上的注意两种不同功能。由于来自大脑电信号的神经振荡活动在认知加工中发挥重要作用，已有研究综述了视觉注意与神经振荡（neural oscillation）的密切关系，但并未涉及不同的注意功能与神经振荡的关系。本文系统性调查了不同注意功能与神经振荡的关系，发现额-顶区域的theta频带振荡活动反映了自上而下的认知控制，而后部脑区的theta振荡与自下而上的注意相关。顶-枕区域alpha振荡的偏侧化有助于注意分配，而alpha频带的大规模同步促成了注意对视皮层自上而下的影响。Beta振荡介导了自上而下的信息与自下而上的信息之间的互动，作为信息载体促进了视觉信息处理。Gamma振荡则可能与自上而下和自下而上的注意间整合相关。本文就视觉注意功能与神经振荡关系的研究现状展开综述，旨在揭示不同的神经振荡活动在特定的视觉注意功能中的作用。     

Sensory gain control (amplification) as a mechanism of selective attention: electrophysiological and neuroimaging evidence.

Both physiological and behavioral studies have suggested that stimulus-driven neural activity in the sensory pathways can be modulated in amplitude during selective attention. Recordings of event-related brain potentials indicate that such sensory gain control or amplification processes play an important role in visual-spatial attention. Combined event-related brain potential and neuroimaging experiments provide strong evidence that attentional gain control operates at an early stage of visual processing in extrastriate cortical areas. These data support early selection theories of attention and provide a basis for distinguishing between separate mechanisms of attentional suppression (of unattended inputs) and attentional facilitation (of attended inputs).     

Novel roles for collagens in wiring the vertebrate nervous system

Wiring the vertebrate nervous system is a multi-step process that relies heavily upon the role of transmembrane and extracellular adhesion molecules. Despite the extensive attention focused on such molecules, collagens, a large family of structural adhesion molecules expressed in the vertebrate nervous system, have been largely overlooked for roles in neural circuit formation. Recently, however, several studies have unexpectedly identified novel roles of collagens and collagen-like molecules in the developing vertebrate nervous system. Here, contributions of these collagens and collagen-like molecules in neural circuit formation are reviewed.     

Human cortical mechanisms of visual attention during orienting and search.

Functional anatomical studies indicate that a set of neural signals in parietal and frontal cortex mediates the covert allocation of attention to visual locations across a wide variety of visual tasks. This frontoparietal network includes areas, such as the frontal eye field and supplementary eye field. This anatomical overlap suggests that shifts of attention to visual locations of objects recruit areas involved in oculomotor programming and execution. Finally, the fronto-parietal network may be the source of spatial attentional modulations in the ventral visual system during object recognition or discrimination.     

The neural crest: basic biology and clinical relationships in the craniofacial and enteric nervous systems

The highly migratory, mesenchymal neural crest cell population was discovered over 100 years ago. Proposals of these cells' origin within the neuroepithelium, and of the tissues they gave rise to, initiated decades-long heated debates, since these proposals challenged the powerful germ-layer theory. Having survived this storm, the neural crest is now regarded as a pluripotent stem cell population that makes vital contributions to an astounding array of both neural and non-neural organ systems. The earliest model systems for studying the neural crest were amphibian, and these pioneering contributions have been ably refined and extended by studies in the chick, mouse, and more recently the fish to provide detailed understanding of the cellular and molecular mechanisms regulating and regulated by the neural crest. The key questions regarding control of craniofacial morphogenesis and innervation of the gut illustrate the wide range of developmental contexts in which the neural crest plays an important role. These questions also focus attention on common issues such as the role of growth factor signaling in neural crest cell development and highlight the central role of the neural crest in human congenital disease.     

Covert shift of attention modulates the ongoing neural activity in a reaching area of the macaque dorsomedial visual stream

Background

Attention is used to enhance neural processing of selected parts of a visual scene. It increases neural responses to stimuli near target locations and is usually coupled to eye movements. Covert attention shifts, however, decouple the attentional focus from gaze, allowing to direct the attention to a peripheral location without moving the eyes. We tested whether covert attention shifts modulate ongoing neuronal activity in cortical area V6A, an area that provides a bridge between visual signals and arm-motor control.

Methodology/Principal Findings

We performed single cell recordings from 3 Macaca Fascicularis trained to fixate straight-head, while shifting attention outward to a peripheral cue and inward again to the fixation point. We found that neurons in V6A are influenced by spatial attention. The attentional modulation occurs without gaze shifts and cannot be explained by visual stimulations. Visual, motor, and attentional responses can occur in combination in single neurons.

Conclusions/Significance

This modulation in an area primarily involved in visuo-motor transformation for reaching may form a neural basis for coupling attention to the preparation of reaching movements. Our results show that cortical processes of attention are related not only to eye-movements, as many studies have shown, but also to arm movements, a finding that has been suggested by some previous behavioral findings. Therefore, the widely-held view that spatial attention is tightly intertwined with—and perhaps directly derived from—motor preparatory processes should be extended to a broader spectrum of motor processes than just eye movements.     

Attention modulates earliest responses in the primary auditory and visual cortices

A fundamental question about the neural correlates of attention concerns the earliest sensory processing stage that it can affect. We addressed this issue by recording magnetoencephalography (MEG) signals while subjects performed detection tasks, which required employment of spatial or nonspatial attention, in auditory or visual modality. Using distributed source analysis of MEG signals, we found that, contrary to previous studies that used equivalent current dipole (ECD) analysis, spatial attention enhanced the initial feedforward response in the primary visual cortex (V1) at 55-90 ms. We also found attentional modulation of the putative primary auditory cortex (A1) activity at 30-50 ms. Furthermore, we reproduced our findings using ECD modeling guided by the results of distributed source analysis and suggest a reason why earlier studies using ECD analysis failed to identify the modulation of earliest V1 activity.     

多目标视觉追踪中的分组效应及其可加性

如何减少注意资源的消耗、提升人类在动态视觉持续性注意任务中的表现,是持续性注意研究关注的重点问题,具有理论和实践的重要意义。多目标追踪任务是研究个体持续性注意的常用实验室方法。多目标追踪任务中,观察者可以利用基于物体特征的分组效应将多个运动目标知觉为一个更大的运动单元,从而减少注意资源的消耗、提高追踪任务表现。为了进一步节省注意资源、提升注意追踪的表现,研究者提出了注意追踪中分组效应的可加性问题。分组效应的可加性表现为基于两个及以上特征的分组对追踪表现的提高优于基于一个特征的分组。可加性的研究对理解不同分组效应的认知机制,个体动态视觉追踪中的注意机制和注意资源分配等具有重要意义。本文对以往的行为以及神经影像学研究进行了汇总,讨论了不同类型分组效应的知觉加工机制及其可加性,系统阐述了基于不同表面特征的不可加性,和基于表面特征与特定时空特征可加性的认知及其神经基础。未来可以从行为学实验角度探究更多基于不同特征分组效应的可加性,或者从注意追踪中基于不同分组效应的神经机制入手,探讨分组效应的可加性问题,为分组效应的分类及可加性研究提供更多认知和神经层面的依据。     

暗示性运动加工的认知神经机制

暗示性运动是指个体观看静止图片时从中知觉到的运动.研究者采用高低认知水平两类暗示性运动刺激材料,借助"冻结帧"、直接观看、运动后效和f MRI适应等任务范式,探讨了注意和意识在暗示性运动加工中的作用及其记忆特点;并借助脑成像等技术,考察了颞中区、颞上皮层区、颞上沟、镜像神经元系统等脑区在暗示性运动加工中的作用.但由于暗示性运动加工涉及"视觉腹侧通路与背侧通路功能的分离与整合"问题,目前对相关研究结果和解释还存在争议,暗示性运动加工的认知神经机制仍有待于进一步研究.