Forebrain mechanisms related to internal inhibition and sleep

In experiments performed on cats and monkeys over the past nine years a “forebrain inhibitory system” has been investigated through recording of neurophysiologic, behavioral, reflexive and intracellular parameters. This forebrain system is capable of expressing its inhibitory influences widely throughout the body, and on both somatic and visceral mechanisms. Electrical stimulation within this system has been shown to: a) suppress ongoing behavior, synchronize the EEG and induce the initial stages of sleep. These behavioral effects could be conditioned to indifferent stimuli. Other studies have shown that lesions within this system result in marked alterations in sleep patterns and in behavioral hyperactivity,b) Inhibit remarkably monosynaptic and polysynaptic reflexes in the brain stem and at cervical and lumbosacral levels of the spinal cord.c) Induce hyperpolarizing potentials within motoneurons of the final common path. Cl infusion caused the hyperpolarization to change to depolarization. Studies of the “forebrain inhibitory system” indicate that at least in part it is a descending system involving both multisynaptic (loop) pathways and direct pathways. It is felt that descending circuits from the forebrain to inhibitory centers in the medulla are responsible for the effects observed at the final common paths from stimulation in the forebrain. It has been found that behaviorally, reflexively and intracellularly, the “forebrain inhibitory system” acts generally in opposition to the reticular activating system of the brain stem, and that the achievement of an organism’s overt behavioral patterns depends on the functional state of both systems.     

大脑电刺激在听觉语言加工研究中的应用

大脑电刺激是历史悠久但近年来才广泛应用在人类被试上的实验技术。通过对颅内刺激位点进行电刺激, 并分析引发的暂时性行为功能变化和记录位点的电位活动, 大脑电刺激技术可以揭示认知加工过程中脑区内的功能作用与脑区间的有效连接。通过对听觉语言加工过程相关的丘脑、听觉皮层、高级语言皮层进行电刺激, 现有研究发现了各个脑区的不同功能特点以及不同脑区间的信息传递机制, 为进一步探索听觉语言加工的神经机制提供了新的视角。     

Neuroscience and learning: lessons from studying the involvement of a region of cerebellar cortex in eyeblink classical conditioning

How the nervous system encodes learning and memory processes has interested researchers for 100 years. Over this span of time, a number of basic neuroscience methods has been developed to explore the relationship between learning and the brain, including brain lesion, stimulation, pharmacology, anatomy, imaging, and recording techniques. In this paper, we summarize how different research approaches can be employed to generate converging data that speak to how structures and systems in the brain are involved in simple associative learning. To accomplish this, we review data regarding the involvement of a particular region of cerebellar cortex (Larsell's lobule HVI) in the widely used paradigm of classical eyeblink conditioning. We also present new data on the role of lobule HVI in eyeblink conditioning generated by combining temporary brain inactivation and single-cell recording methods, an approach that looks promising for further advancing our understanding of relationships between brain and behavior.     

Regional brain catecholamines and memory: effects of footshock, amygdala implantation, and stimulation

Previous findings have revealed a correlation between post-training release of whole brain norepinephrine (NE) and later retention performance. The present experiment examined changes after a training footshock in NE levels, as well as the levels of the major central NE metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), dopamine (DA), and epinephrine (EPI) in eight brain regions. Brain levels of these amines and the metabolite were assessed 10 min after training in a one-trial inhibitory (passive) avoidance task. The results indicate that NE levels decreased significantly in neocortex, neostriatum, hypothalamus, frontal pole, septum, and brainstem, but not in hippocampus or thalamus. The decreases in NE levels were generally accompanied by increases in MHPG; the MHPG/NE ratio increased significantly in all areas in which decreases in NE were observed. DA levels decreased in neostriatum and increased in neocortex and brainstem. Epinephrine levels decreased only in the brainstem sample. Thus, the effects of training on NE are widespread, probably reflecting the release of the amine in most brain regions. Such findings are consistent with the view that posttraining release of brain NE may modulate the storage of new information in many brain regions. One especially potent treatment for modulating memory storage is electrical stimulation of the amygdala. Therefore, we also examined the effects of amygdala implantation and stimulation on brain catecholamine levels to determine whether such changes might be correlated with the effects of amygdala stimulation on memory. The results indicate that electrode implantation into the amygdala results in pervasive changes in NE levels in most brain regions tested. Against this modified baseline, the results of training and electrical stimulation were region specific and very difficult to interpret. The major conclusion which can be derived from this portion of the experiment is that the amygdala damage produced by electrode implantation produces a brain which is substantially different from that of intact animals.     

Continuous Theta Burst Transcranial Magnetic Stimulation of the Right Dorsolateral Prefrontal Cortex Impairs Inhibitory Control and Increases Alcohol Consumption

Previous research indicates that alcohol intoxication impairs inhibitory control and that the right dorsolateral prefrontal cortex (rDLPFC) is a functional brain region important for exercising control over thoughts and behaviour. At the same time, the extent to which changes in inhibitory control following initial intoxication mediate subsequent drinking behaviours has not been elucidated fully. Ascertaining the extent to which inhibitory control impairments drive alcohol consumption, we applied continuous theta burst transcranial magnetic stimulation (rDLPFC cTBS vs. control) to isolate how inhibitory control impairments (measured using the Stop-Signal task) shape ad libitum alcohol consumption in a pseudo taste test. Twenty participants (13 males) took part in a within-participants design; their age ranged between 18 and 27 years (M = 20.95, SD = 2.74). Results indicate that following rDLPFC cTBS participants’ inhibitory control was impaired, and ad libitum consumption increased. The relationship between stimulation and consumption did not appear to be mediated by inhibitory control in the present study. Overall, findings suggest that applying TMS to the rDLPFC may inhibit neural activity and increase alcohol consumption. Future research with greater power is recommended to determine the extent to which inhibitory control is the primary mechanism by which the rDLPFC exerts influence over alcohol consumption, and the degree to which other cognitive processes may play a role.     

The effects of hypothermia and hunger on the duration of bar pressing for intracranial self-stimulation in rats

Hypothermic rats at rectal temperatures below 30° C showed decreased duration of bar pressing for intracranial self-stimulation in lateral hypothalamic sites. The same effect was found in hungry rats. Both with cooling and hunger, decreased durations were accompanied by decreased thresholds. The threshold changes in hypothermic rats exceeded 12 μA in some cases. The results are relevant to explanations of why animals turn off rewarding brain stimulation. Particular attention is given to the possibility that cooling enhances neural activity in facilitatory connections between positive and aversive systems.     

Transient increase of intact visual field size by high-frequency narrow-band stimulation

Three patients with visual field defects were stimulated with a square matrix pattern, either static, or flickering at frequencies that had been found to either promote or not promote blindsight performance. Comparison between pre- and post-stimulation perimetric maps revealed an increase in the size of the intact visual field but only for flicker frequencies previously found to promote blindsight. These changes were temporary but dramatic – in two instances the intact field was increased by an area of ∼30 deg² of visual angle. These results indicate that not only does specific high-frequency stimulus flicker promote blindsight, but that intact visual field size may be increased by stimulation at the same frequencies. Our findings inform speculation on both the brain mechanisms and the potency of temporal modulation for altering the functional visual field.     

Positive reinforcement and suppression from the same occurrence of the unconditioned stimulus in a positive conditioned suppression procedure

Responding of rats was maintained on a variable-interval schedule of food reinforcement. The same response also produced a blinking light followed by electrical brain stimulation according to a fixed-interval schedule. This conjoint schedule produced two behavioral changes. First, instead of a steady rate of responding throughout the session, which would be characteristic of the variable interval food schedule alone, responding between occurrences of the light-brain stimulation pairings became positively accelerated and thus was more characteristic of the fixed-interval schedule of these pairings. Second, food responding was suppressed during the light that preceded brain stimulation. These results indicate that positive reinforcement and suppression resulted from the same occurrence of the light-brain stimulation combination. This finding suggests that stimuli such as conditioned reinforcers that precede an unconditioned reinforcer may have a suppressive effect upon responding in their presence that is being maintained by another reinforcer.     

乳头体对海马齿状回习得性长时程突触增强的影响

用高频电脉冲刺激大鼠乳头体（ＭＢ）,可一过性抑制由刺激穿通纤维（ＰＰ）诱发的海马齿状回（ＤＧ）群体锋电位（ＰＳ）。训练作业前先刺激ＭＢ,导致ＤＧ的习得性长时程突触增强（ＬＤＬＴＰ）的形成显著延缓,相应地延缓了条件性饮水反应的建立。电刺激ＭＢ对ＰＰ─ＤＧＰＳ的这种抑制作用在训练所产生的ＰＳ增大达最高水平时显著减弱,刺激ＭＢ对ＬＤＬＴＰ的保持及相应地对条件反应的巩固没有明显影响。结果表明ＭＢ对ＤＧＬＤＬＴＰ的形成有抑制性调制作用。     

Moving memories: Behavioral synchrony and memory for self and others

Establishing and maintaining connections with others is central to a fulfilling social life. In this respect, behavioral coordination provides one avenue by which interpersonal linkages can be formed. Drawing from the dynamical systems approach, the present research explored whether temporary interpersonal connections founded on coordinated behavior influence memory for self and others. To do so, we measured participants’ incidental recall of self and other-relevant information after a period of either in-phase or anti-phase interpersonal coordination. While participants in the less stable anti-phase condition demonstrated the typical memory advantage for self-related compared to other-related information, this effect was eliminated when participant and confederate movements displayed in-phase coordination. These results are discussed with respect to the interplay between the systems that support interpersonal synchrony and basic social-cognitive processing.     

What has fMRI told us about the Development of Cognitive Control through Adolescence?

Cognitive control, the ability to voluntarily guide our behavior, continues to improve throughout adolescence. Below we review the literature on age-related changes in brain function related to response inhibition and working memory, which support cognitive control. Findings from studies using functional magnetic resonance imaging (fMRI) indicate that processing errors, sustaining a cognitive control state, and reaching adult levels of precision, persist through adolescence. Developmental changes in patterns of brain function suggest that core regions of the circuitry underlying cognitive control are on-line early in development. However, age-related changes in localized processes across the brain, and in establishing long range connections that support top-down modulation of behavior, more effective neural processing for optimal mature executive function. While great progress has been made in understanding the age-related changes in brain processes underlying cognitive development, there are still important challenges in developmental neuroimaging methods and the interpretation of data that need to be addressed.     

Centrally elicited aggressive behavior: A model system for the study of episodic neurobehavioral pathologies?

Studies in which the predatory-like attack of a cat upon a rat has been elicited by electrical brain stimulation have been briefly reviewed with an emphasis on the question of where within the central nervous system such brain stimulation is producing its behaviorally meaningful effects. Two opposing but by no means mutually exclusive views are considered. The first is that brain stimulation elicits this behavior pattern primarily because it affects a specific motivated behavior system that is organized discretely in the midbrain and pons. The second is that forebrain neural activity is modulated in behaviorally significant ways by brainstem stimulation, which elicits predatory-like aggressive behavior in the cat. The possibility that further research on the altered state of central nervous system activity, induced by brain stimulation which elicits aggressive behavior in the cat, may lead to a further understanding of the altered states of central nervous system activity that underlie the aggressive dyscontrol syndrome and other episodic state disorders is discussed.     

A comparative review of the primate motor system

Primates have evolved separately from other mammals since the late Cretaceous, and during this time the two major extant primate groups, prosimians (lorises, lemurs, and tarsiers) and anthropoids (monkeys, apes, and humans) arose. Concurrently, structures within the central nervous system acquired primate characteristics. Not all of the uniquely primate features have been identified in the brain, but several are well known. The pyramidal system, the best studied motor system, shows a distinct primate pattern in its terminal connections in the spinal cord. Other descending systems are less well known, but primate specializations in the vestibular system and red nucleus have been observed. The primary and secondary motor cortices are topographically separated in primates, suggesting one basis for increased complexity. Given the size of the brain, structures in the basal ganglia are relatively enlarged in primates as compared with other mammals, whereas the cerebellum has the same relative size.     

The Role of Similarity Analysis in Understanding Movement

Primates have evolved separately from other mammals since the late Cretaceous, and during this time the two major extant primate groups, prosimians (lorises, lemurs, and tarsiers) and anthropoids (monkeys, apes, and humans) arose. Concurrently, structures within the central nervous system acquired primate characteristics. Not all of the uniquely primate features have been identified in the brain, but several are well known. The pyramidal system, the best studied motor system, shows a distinct primate pattern in its terminal connections in the spinal cord. Other descending systems are less well known, but primate specializations in the vestibular system and red nucleus have been observed. The primary and secondary motor cortices are topographically separated in primates, suggesting one basis for increased complexity. Given the size of the brain, structures in the basal ganglia are relatively enlarged in primates as compared with other mammals, whereas the cerebellum has the same relative size.     

The Limitations and Potential of Neuroimaging in the Criminal Law

Neuroimaging showing brain abnormalities is increasingly being introduced in criminal court proceedings to argue that a defendant could not control his behavior and should not be held responsible for it. But imaging has questionable probative value because it does not directly capture brain function or a defendant’s mental states at the time of a criminal act. Advanced techniques could transform imaging from a coarse-grained measure of correlations between brain states and behavior to a fine-grained measure of causal connections between them. Even if this occurs, bias and other attitudes may unduly influence jurors’ interpretation of the data. Moreover, judges’ decisions about whether neuroimaging data is legally relevant and admissible are normative decisions based on more than empirical evidence. Advanced neuroimaging will better inform assessments of criminal responsibility but will not supplant or explain away the psychological and normative foundation of the criminal law.     

Serotonin's influence on predatory behavior of highly aggressive cba and weakly aggressive DD strains of mice

The effects of serotonin were studied on locust-killing behavior of mice from low (DD) and high (CBA) predatory aggressive strains. 5-HTP injected intraperitoneally (50 and 100 mg/kg) or 5-HT administered into the lateral ventricle (10 μg) significantly reduced locust-killing behavior in highly aggressive CBA mice. Imipramine (20, 30, and 40 mg/kg) elicited a dose-dependent inhibitory effect on predatory behavior. Fluoxetine (10 and 20 mg/kg) alone had a slight influence on locust-killing behavior but potentiated the action of the subthreshold dose of 5-HTP (25 mg/kg). Pretreatment with the blocker of 5-HT₂ type receptors methysergide (2 mg/kg) abolished the inhibitory effect of 5-HTP. These finding indicate that serotonin of the brain exerts an inhibitory effect on predatory behavior in mice. In contrast, neither lesion of the dorsal raphe nucleus (although significantly depleting the brain serotonin) nor treatment with methysergide (2 mg/kg) induced locust-killing behavior in weakly aggressive DD mice. Low predatory aggressiveness in DD mice is suggested to be related to the low tonus of the mechanisms activating killing behavior rather than to excessive serotonergic inhibitory influences.     

额叶区域的经颅直流电刺激对抑制控制的影响

抑制控制是执行功能的重要组成部分之一, 研究表明抑制控制与额叶区域的活动有关。经颅直流电刺激(Transcranial Direct Current Stimulation, tDCS)是一种非侵入性的脑刺激技术, 可以调节脑区的激活程度。研究表明tDCS刺激额叶的部分区域可以有效干预参与者的抑制控制水平, 而这一干预作用会受到刺激位置、刺激类型以及实验任务等条件变化的影响。目前tDCS已应用于不同人群的抑制控制研究, 并能与其他研究技术较好的结合。     

Dreams as Fictional Remembering

ABSTRACT

During dreaming, the brain inhibits input from the senses and blocks motor output. The miracle is that, despite a lack of contact with the senses and a temporary paralysis, the brain continues to generate densely meaningful first-person scenarios. What justifies this purely imaginative procedure that leaves people so vulnerable to predators? A great deal of neuroanatomical evidence suggests that during REM sleep, the brain prunes exuberant synaptic connections. In so doing, the brain simplifies overly complex models of the world formed during the day to deal with noisy scenarios and renders them more generalizable to the future. Freud likened the mandate of dreaming to the task an illustrator faces in coming up with a single illustration to represent the day’s headlines. In my view, this process of condensation is not a method of disguise, as Freud believed, but the very function of dreaming, and it has a temporal signature. Dreams reveal and simplify past happenings by generating tight fictional narratives around similar schemas, exposing by analogy the deep invariant structures of the stories by which people organize their lives.     

基本情绪的神经基础：来自fMRI与机器视觉技术研究的证据

基本情绪理论(basic emotion theory)是情绪科学领域最具代表性的理论, 该理论认为人类情绪是由有限的几种基本情绪组成的, 如恐惧、愤怒、喜悦、悲伤等。基本情绪是为了完成基本生命任务(fundamental life task)进化而来的, 每一种基本情绪都有独特的神经结构和生理基础。尽管基本情绪理论被广泛接受, 但是对于基本情绪的种类却莫衷一是。近几十年来, 许多fMRI研究试图确定各种基本情绪的独特神经结构基础, 而且取得了许多重要发现, 比如厌恶和脑岛有关, 悲伤和前扣带回有关, 杏仁核是与恐惧有关的重要边缘结构等。但是, 最近有人进行了元分析研究, 发现许多基本情绪存在混淆的大脑区域, 因此对基本情绪的特定脑区理论提出质疑, 甚至否定基本情绪理论。通过对基本情绪及其神经基础的探讨, 以及对基本情绪理论的最新功能性磁共振成像研究进行梳理分析, 提出有关基本情绪理论的争论来源于基本情绪种类的确定, 因为许多所谓的不同基本情绪实际上是同一种基本情绪, 提出人类可能只有3种基本情绪。未来研究可以利用机器视觉技术进一步推动基本情绪脑影像研究。     

Neuroimmune stress responses: reciprocal connections between the hypothalamus and the brainstem

Hypothalamic nuclei, particularly the paraventricular nuclei (PVN), are important brain sites responsible for eliciting stress responses following a systemic immune challenge. The activation of PVN cells by a systemic immune challenge is critically dependent on the integrity of inputs from brainstem cells situated in the nucleus tractus solitarius (NTS) and ventrolateral medulla (VLM). Interestingly, a descending pathway from the PVN to the brainstem, recruited by systemic immune challenge, might also exist. It is well documented that PVN neurons innervate the NTS and VLM and recent evidence from our laboratory shows that lesions of the PVN reduce brainstem cell responses elicited by a systemic bolus of the proinflammatory cytokine interleukin-1beta (IL-1beta). Although a number of different PVN divisions are candidates for the source of inputs to the brainstem, we have demonstrated that the majority of descending PVN projections recruited by systemic IL-1beta arise from cell bodies localized in the medial and lateral parvocellular PVN. These findings suggest that central nervous system responses to an immune challenge are likely to involve complex reciprocal connections between the PVN and the brainstem, whereby brainstem cell populations could essentially act as integratory sites for descending and ascending immune signals. For instance, these brainstem pathways may have significant implications not only for the regulation of central hypothalamic and extra-hypothalamic targets but also the autonomic nervous system.