Mechanisms and the current state of transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is unique among the current brain stimulation techniques because it is relatively non-invasive. TMS markedly differs from vagus nerve stimulation, deep brain stimulation and magnetic seizure therapy, all of which require either an implanted prosthesis or general anesthesia, or both. Since its rebirth in its modern form in 1985, TMS has already shown potential usefulness in at least three important domains-as a basic neuroscience research instrument, as a potential clinical diagnostic tool, and as a therapy for several different neuropsychiatric conditions. The TMS scientific literature has now expanded beyond what a single summary article can adequately cover. This review highlights several new developments in combining TMS with functional brain imaging, using TMS as a psychiatric therapy, potentially using TMS to enhance performance, and finally recent advances in the core technology of TMS. TMS' ability to non-invasively and focally stimulate the brain of an awake human is proving to be a most important development for neuroscience in general, and neuropsychiatry in particular.     

Introducing Transcranial Magnetic Stimulation (TMS) and its Property of Causal Inference in Investigating Brain-Function Relationships

Transcranial magnetic stimulation (TMS) is a method capable of transiently modulating neural excitability. Depending on the stimulation parameters information processing in the brain can be either enhanced or disrupted. This way the contribution of different brain areas involved in mental processes can be studied, allowing a functional decomposition of cognitive behavior both in the temporal and spatial domain, hence providing a functional resolution of brain/mind processes. The aim of the present paper is to argue that TMS with its ability to draw causal inferences on function and its neural representations is a valuable neurophysiological tool for investigating the causal basis of neuronal functions and can provide substantive insight into the modern interdisciplinary and (anti)reductionist neurophilosophical debates concerning the relationships between brain functions and mental abilities. Thus, TMS can serve as a heuristic method for resolving causal issues in an arena where only correlative tools have traditionally been available.     

From the left to the right: How the brain compensates progressive loss of language function

In normal right-handed subjects language production usually is a function oft the left brain hemisphere. Patients with aphasia following brain damage to the left hemisphere have a considerable potential to compensate for the loss of this function. Sometimes, but not always, areas of the right hemisphere which are homologous to language areas of the left hemisphere in normal subjects are successfully employed for compensation but this integration process may need time to develop. We investigated right-handed patients with left hemisphere brain tumors as a model of continuously progressive brain damage to left hemisphere language areas using functional neuroimaging and transcranial magnetic stimulation (TMS) to identify factors which determine successful compensation of lost language function. Only patients with slowly progressing brain lesions recovered right-sided language function as detected by TMS. In patients with rapidly progressive lesions no right-sided language function was found and language performance was linearly correlated with the lateralization of language related brain activation to the left hemisphere. It can thus be concluded that time is the factor which determines successful integration of the right hemisphere into the language network for compensation of lost left hemisphere language function.     

State-dependency in brain stimulation studies of perception and cognition

We address the importance of understanding initial states of neuronal populations and of state-dependent responses in cognitive neuroscience experiments with special emphasis on brain stimulation studies of perception and cognition. The approach we present is based on evidence that behavioural and perceptual effects of transcranial magnetic stimulation (TMS) are determined by initial neural activation state; by systematically manipulating neural activation states before application of TMS, one can selectively target specific, even spatially overlapping neural populations within the affected region. This approach is potentially of great benefit to cognitive neuroscience and remediation programmes as it combines high spatial and functional resolution with the ability to assess causality.     

Suppression of extinction with TMS in humans: from healthy controls to patients

We review a series of studies exemplifying some applications of single-pulse and paired-transcranial magnetic stimulation (TMS) in the study of spatial attention and of its deficits. We will focus primarily on sensory extinction, the failure to consciously perceive a contralesional sensory stimulus only during bilateral stimulation of homologous surfaces. TMS studies in healthy controls show that it is possible either to interfere or modulate the excitability of the parietal cortex during sensory (i.e. tactile and visual) attentional tasks, thus reproducing a condition of virtual extinction. TMS studies in patients with unilateral (mainly right) brain damage show that the modulation of the unbalance in cortical excitability between the two cerebral hemispheres transiently improves contralesional sensory extinction. These studies show the possible application of TMS not only as a research method in healthy subjects, but also as a tool for inducing brain excitability changes in patients with sensory extinction, which could be useful for supporting the rehabilitation of this deficit.     

Transcranial magnetic stimulation: neurophysiological applications and safety

TMS is a non-invasive tool for measuring neural conduction and processing time, activation thresholds, facilitation and inhibition in brain cortex, and neural connections in humans. It is used to study motor, visual, somatosensory, and cognitive functions. TMS does not appear to cause long-term adverse neurological, cardiovascular, hormonal, motor, sensory, or cognitive effects in healthy subjects. Single-pulse (<1Hz) TMS is safe in normal subjects. High frequency, high-intensity repetitive TMS (rTMS) can elicit seizures even in normal subjects. Safety guidelines for using rTMS have been published.     

基于非侵入性脑刺激的认知增强：方法、伦理和应用

作为人类追求卓越的方式之一,基于非侵入性脑刺激的认知增强成为众多学科和公众关注的问题。首先阐述了非侵入性脑刺激的两种主要技术手段(经颅磁刺激和经颅直流刺激)的技术原理及其在提升健康个体认知功能上的应用,并分析了这两种技术可能带来的安全、自主选择、公平等伦理问题,最后总结了该认知增强技术在体育和军事等两个具体领域的应用。未来可进一步提高技术手段的深部脑区刺激能力及该增强技术的持续和真实效果。     

Magnetic stimulation studies of visual cognition

The panoply of non-invasive techniques for brain imaging is responsible for much of the current excitement in cognitive neuroscience; sensory, perceptual and cognitive behaviour can now be correlated with cerebral blood flow as assessed by functional imaging, the electrical fields generated by populations of neurons or changes in magnetic fields created by electrical activity. Correlations between localized brain activity and behaviour, however, do not of themselves establish that any brain area is necessary for a particular task; necessity is the domain of the lesion technique. Transcranial magnetic stimulation (TMS) is a technique that can be used non-invasively to produce reversible functional disruption and has already been used to investigate visual detection, discrimination, attention and plasticity. The power of TMS as a `lesion' technique lies in the opportunity to combine reversible disruption with high degrees of spatial and temporal resolution. In this review we trace some of the major developments in the use of TMS as a technique for the investigation of visual cognition.     

Elucidating the neural correlates of egoistic and moralistic self-enhancement

Self-enhancement is the biasing of one’s view of oneself in a positive direction. The brain correlates of self-enhancement remain unclear though it has been reported that the medial prefrontal cortex (MPFC) may be important for producing self-enhancing responses. Previous studies have not examined whether the neural correlates of self-enhancement depend on the particular domain in which individuals are enhancing themselves. Both moralistic and egoistic words were presented to participants while transcranial magnetic stimulation (TMS) was applied to the MPFC, precuneus or in a sham orientation. Participants were asked to make decisions as to the words describing themselves, some of which were positive and some of which were negative. It was found the MPFC TMS significantly disrupted egoistic self-enhancement when TMS was delivered to the MPFC. Judgments involving moralistic words were not influenced by TMS. These data provide further evidence that MPFC is involved in self-enhancement, and that the role of MPFC may be selective in this regard.     

The physiological basis of transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is the noninvasive method of choice for studying the causal relevance of a cortical area in the human brain. The success of TMS, however, is contrasted by limited insight into its mechanism of action. A recent study by Allen and colleagues offers stunning new insight into the physiological underpinnings of TMS. Their findings expand our understanding about a method that is widely used for stimulating research in the cognitive neurosciences.     

背外侧前额叶对主动遗忘负性社会反馈的作用：针对抑郁症的TMS研究

抑郁症患者的负性心境可能源于其抑制功能障碍。患者在主动遗忘负性材料时无法有效调用背外侧前额叶(the dorsolateral prefrontal cortex, DLPFC)等负责抑制控制的额叶脑网络。同时, 患者对社会信息的加工比对非社会信息的加工存在更明显的认知神经障碍, 很难主动遗忘对自己不利的社会反馈信息。为了提高抑郁症患者对负性社会反馈的主动遗忘能力, 本研究采用经颅磁刺激技术(transcranial magnetic stimulation, TMS), 考察抑郁症患者在左侧(n = 32)或右侧DLPFC (n = 30)被激活后其记忆控制能力的改变。结果表明, 当患者的DLPFC被TMS激活时, 他们对社会拒绝的回忆正确率与健康对照组(n = 31)无差异, 且TMS激活右侧DLPFC还改善了患者对他人的社会态度。本研究是采用TMS提高抑郁症患者主动遗忘能力的首次尝试, 研究结果不但支持了DLPFC与记忆控制功能的因果关系, 还为临床治疗抑郁症、创伤后应激障碍、药物成瘾等患者的记忆控制缺陷提供了明确的神经靶点。     

TMS in cognitive plasticity and the potential for rehabilitation

Cognitive neuroscientists use transcranial magnetic stimulation (TMS) in several ways, from aiming to increase understanding of brain-behavior relationships to transiently improving performance, both in normals and in patients with neurological and neuropsychological deficits. Different types of TMS (single-pulse, paired-pulse, repetitive) are able to interfere with higher brain functions that require the cooperation of different brain areas and complex neuronal networks. Currently, behavioral TMS effects on the brain are usually short-lived and their underlying mechanisms not yet wholly understood. However, the aim of using TMS to develop rehabilitative strategies for motor, perceptive and cognitive functions represents an intriguing challenge.     

An ethics perspective on transcranial magnetic stimulation (TMS) and human neuromodulation

This paper concerns the ethics of human neuromodulation using transcranial magnetic stimulation (TMS). We examine the challenges of modulating the brain with TMS through the research ethics lens and in clinical medicine for treating frank pathology, primarily in psychiatric diseases. We also consider contemporary issues raised in the neuroethics literature about managing unexpected findings, and relate these to TMS and to other frontier neurotechnology that is becoming openly available in the public domain. We argue that safety and informed consent are of paramount importance for TMS, but that personal values and sociocultural factors must also be considered when examining the promise of this technology and applications that ought to be highlighted for extra precautions.     

Modeling the emergence of informational content by adaptive networks for temporal factorisation and criterial causation

Propagated activation of neurons through their network is an important process in the brain. Another crucial part of neural processing concerns adaptation over time of characteristics of this network such as connection strengths or excitability thresholds. This adaptation can be slow, as in learning from a multiple experiences, or it can be fast, as in memory formation. These adaptive network characteristics can be considered informational criteria for activation of a neuron. This then is viewed as a form of emergent information formation. Activation of neurons is determined by such information via a process termed criterial causation. In the current paper, the relationship of criterial causation with the principle of temporal factorisation for the dynamics of the world in general is explored. Temporal factorisation describes how the world represents information about its past in its present state, which then in turn determines the world’s future. In the paper, it is shown how these processes are analysed in more detail and modeled by (adaptive) network models.     

Representational momentum and the brain: An investigation into the functional necessity of V5/MT

The mental representation of objects can imply motion and momentum. This can be explored by investigating a distortion in recognition memory for pictures that depict objects “frozen” in mid-air, implying motion. This distortion is called representational momentum (RM). Recent functional neuroimaging studies have suggested that the V5/MT system (the area of the brain thought to be responsible for perceptual processing of motion) is involved in the mediation of RM. The results of these studies are reviewed here. However the presence of functional activity revealed in brain imaging studies does not mean that this part of the brain is necessary for a particular cognitive task. A greater degree of functional necessity can be inferred by disrupting function in that part of the brain. One way in which this can be done is with Transcranial Magnetic Stimulation (TMS, a method of temporarily suspending cortical activity). We extended the findings of the previous fMRI experiments by using TMS in conjunction with an RM paradigm. Repetitive magnetic stimulation to V5/MT during the so-called freeze-frame RM task resulted in an absence of the stereotypical distortion in recognition memory (compared to stimulation at the vertex) for approximately 60% of     

Neurophysiology and neuroanatomy of reflexive and volitional saccades as revealed by lesion studies with neurological patients and transcranial magnetic stimulation (TMS)

This review discusses the neurophysiology and neuroanatomy of the cortical control of reflexive and volitional saccades in humans. The main focus is on classical lesion studies and studies using the interference method of transcranial magnetic stimulation (TMS). To understand the behavioural function of a region, it is essential to assess oculomotor deficits after a focal lesion using a variety of oculomotor paradigms, and to study the oculomotor consequences of the lesion in the chronic phase. Saccades are controlled by different cortical regions, which could be partially specialised in the triggering of a specific type of saccade. The division of saccades into reflexive visually guided saccades and intentional or volitional saccades corresponds to distinct regions of the neuronal network, which are involved in the control of such saccades.TMS allows to specifically interfere with the functioning of a region within an intact oculomotor network. TMS provides advantages in terms of temporal resolution, allowing to interfere with brain functioning in the order of milliseconds, thereby allowing to define the time course of saccade planning and execution.In the first part of the paper, we present an overview of the cortical structures important for saccade control, and discuss the pro’s and con’s of the different methodological approaches to study the cortical oculomotor network. In the second part, the functional network involved in reflexive and volitional saccades is presented. Finally, studies concerning recovery mechanisms after a lesion of the oculomotor cortex are discussed.     

Neurophysiology and neuroanatomy of reflexive and volitional saccades as revealed by lesion studies with neurological patients and transcranial magnetic stimulation (TMS)

This review discusses the neurophysiology and neuroanatomy of the cortical control of reflexive and volitional saccades in humans. The main focus is on classical lesion studies and studies using the interference method of transcranial magnetic stimulation (TMS). To understand the behavioural function of a region, it is essential to assess oculomotor deficits after a focal lesion using a variety of oculomotor paradigms, and to study the oculomotor consequences of the lesion in the chronic phase. Saccades are controlled by different cortical regions, which could be partially specialised in the triggering of a specific type of saccade. The division of saccades into reflexive visually guided saccades and intentional or volitional saccades corresponds to distinct regions of the neuronal network, which are involved in the control of such saccades.TMS allows to specifically interfere with the functioning of a region within an intact oculomotor network. TMS provides advantages in terms of temporal resolution, allowing to interfere with brain functioning in the order of milliseconds, thereby allowing to define the time course of saccade planning and execution.In the first part of the paper, we present an overview of the cortical structures important for saccade control, and discuss the pro’s and con’s of the different methodological approaches to study the cortical oculomotor network. In the second part, the functional network involved in reflexive and volitional saccades is presented. Finally, studies concerning recovery mechanisms after a lesion of the oculomotor cortex are discussed.     

认知老化与脑：HAROLD模型之争

HAROLD模型（Hemispheric Asymmetry Reduction in Older Adults）是指与年轻人相比,老年人在完成某些认知任务时大脑激活呈现出非对称性减弱的现象。该模型自提出以来就引发了很多质疑和研究,近几年来又有一系列的研究分别从不同角度提供了支持该模型的证据,它们包括记忆研究领域、抑制研究领域、语言认知研究领域、感觉动作研究领域和脑神经研究领域。同时也存在明显不支持该模型的研究证据,主要体现为对补偿说的批驳。通过对支持该模型和不支持该模型两方面脑成像研究成果的文献分析,发现HAROLD模型可能是一个任务特异性模型;除补偿说之外,还有其他可能的观点能够解释功能性脑成像的年龄差异;对脑激活定义的进一步明确化有助于澄清相关的争论     

面孔认知的四个层面及FFA在其中的作用

面孔具有明显不同于其他刺激物的特点,面孔认知的目的也因此与其他物体认知的目的大相径庭。依据面孔认知的目的,本文将面孔认知划分为四个层面：将面孔区别于一般物体的第一层面,对面孔物理属性进行识别的第二层面,对面孔的生物属性进行识别的第三层面和对面孔的社会属性进行识别的第四层面。FFA是面孔加工的一个重要脑区,通过论述它对面孔认知各层面的作用,FFA在面孔加工中的作用被进一步明确。     

表象测量方法述评

表象测量在训练领域广泛应用,也是训练成败的关键环节.表象测量方法可分为口头报告纸笔法、实验操作法,以及神经科学技术共三种方法.其中纸笔报告法以量表测量为主,包括Betts量表、视觉表象清晰度量表及其修订版和运动表象清晰度量表及其修订版;实验操作法以心理旋转为基本范式;神经科学技术主要以经颅磁刺激和功能磁共振成像为主,测量多种表象过程中不同脑区兴奋性.三者各有优劣,均有待提高和改进.