Evidence for a motor mechanism of pain-induced aggression instigation in humans

The automatic skeletal motor responses of 20 male and 20 female student subjects (aged 20–36) receiving a painful stimulation (electric shock) were studied by examining voluntary concomitant extensions and flexions of the arm. These movements were either of long duration, allowing for an on-line control of their execution or, of short duration, requiring extensive pre-programming. Subjects were instructed either to push or to pull a lever upon receipt of an acoustic signal, which was paired or unpaired with an electric shock. Latencies for long duration movements (regardless of direction) were reduced by reception of painful stimulation. Latencies of short duration extensions and flexions were respectively reduced and increased by painful stimulation. Latencies of short duration movements were larger for females than males, regardless of movement direction. These data suggest that painful stimulation elicits automatic movements which affect programming of the termination of simultaneous voluntary movements. Implications of these findings for the study of aggressive behavior are discussed. © 1994 Wiley-Liss, Inc.     

Bilateral Transcranial Direct Stimulation Over the Primary Motor Cortex Alters Motor Modularity of Multiple Muscles

Abstract

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has been demonstrated to modulate the motor performance of both healthy individuals and patients with neuromuscular disorders. However, the effect of tDCS on motor control of multiple muscles, which is a prerequisite to change in motor performance, is currently unknown. Using dimensionality reduction analysis, we investigated whether bilateral tDCS over M1 modulates the coordinated activity of 12 muscles. Fifteen healthy men participated in this randomized, double-blind crossover study. Each participant received a 20-min sham and 2-mA stimulation bilaterally over M1 (anode on the right M1 and cathode on the left M1), with a minimum washout period of 4?days. Muscle activation and end-point kinematics were evaluated during a task where participants reached out to a marked target with non-dominant hand as fast as possible, before and immediately after tDCS application. We found decreased similarity in motor modularity and significant changes in muscle activation in a specific motor module, particularly when reaching out to a target placed within arm’s length and improved smoothness index of movement only following 2-mA stimulation. These findings indicate that clinicians and researchers need to consider the simultaneous effect of bilateral tDCS over M1 on multiple muscles when they establish tDCS protocol to change in motor performance of patients with neuromuscular deficits.     

Visual aspects of centrally elicited attack behavior in the cat: “Patterned reflexes” associated with selection of and approach to a rat

It has been previously suggested that the electrical brain stimulation which elicits quiet-biting attack in the cat actively affects the way the central nervous system processes visual and tactile information concerned with the reflexes involved in the terminal aspects of attack. In order to examine the effects of brain stimulation on a nonterminal aspect of attack – the stimulated cat's selection of and approach to a rat – cats were implanted with attack-eliciting electrodes in both the lateral hypothalamus and the midbrain ventral tegmental area. These cats were then tested in an 8-ft-long cage, one end of which was divided into three, 2-ft-long parallel compartments, whose openings faced the end of the cage from which the cat commenced its approach. An anesthetized rat was placed at the back of one compartment, a bowl of food at the back of another compartment, and the third compartment contained no object. It was found in the first experiment that the attack elicited by nearly all electrodes was selectively directed at the rat. However, the success of the cat in finding the compartment containing the rat varied dramatically for different electrodes in the same cat. Further, these differences were stable and did not change as the cat gained experience with the task. The results suggested that the stimulation of different brain sites in the same cat differentially affected the visual neural mechanisms involved in guiding a cat to a rat. Previous studies have also suggested that the effects of brain stimulation which elicits quiet-biting attack are largely lateralized to the side of the brain stimulated. In order to determine if the effects of stimulation on the neural mechanisms mediating the visually guided approach of a cat to a rat were also lateralized, attempts were made in a second experiment to disrupt the visual input to one side of the brain by unilaterally transecting the optic tract. It was found that this manipulation interfered with the visually guided selective approach to a rat, if the cat was stimulated through hypothalamic or mid-brain electrodes ipsilateral to the optic tract transection, but not if the hypothalamic or midbrain stimulation was on the contralateral (visually intact) side of the brain. However, any final interpretation of the results was confounded by the finding in all of these cats of a complex syndrome of neglect of all contralateral sensory information.     

The neural pathways mediating quiet-biting attack behavior from the hypothalamus in the cat: A functional autoradiographic study

Electrical stimulation of the region of the lateral hypothalamus produced a consistent form of quiet-biting attack behavior in cats. In one series of experiments, cats, implanted with electrodes from which attack had been elicited, were anesthetized and then were injected with a bolus of ¹⁴C-2-deoxyglucose at the same time as electrical stimulation was delivered through the attack electrodes. Brains prepared for X-ray autoradiography revealed that lateral hypothalamic stimulation activated the classical medial forebrain bundle pathway supplying the septal region, diagonal band, lateral preoptic area, and ventral tegmental region. Stimulation of quiet-attack sites in perifornical hypothalamus resulted in the activation of a much more extensive projection system which included the central and lateral tegmental fields of the midbrain and pons, and central gray region, as well as the structures described above. In a second series of experiments, ³H-leucine was placed into the region of the electrode tip from which attack was elicited in order to identify more precisely the pathways arising from that site. In general, tritiated amino acid radioautography replicated the ¹⁴C-2-deoxyglucose findings. In addition, the amino acid radioautographic data revealed the presence of extensive projections from perifornical hypothalamus to such pontine structures as the nucleus locus coeruleus, motor nucleus of NV , and the lateral pontine tegmental field. The functional connections between the lateral hypothalamic “attack region” and lateral preoptic zone were also confirmed by electrophysiological methods.     

左侧眶额皮层在自动情绪调节下注意选择中的作用：来自经颅直流电刺激的证据

前人研究表明自动情绪调节能够自上而下地影响情绪及情绪性注意过程。近来有研究提示自动情绪调节与眶额皮层(orbitofrontal cortex, OFC)有关。也有研究表明左侧OFC的激活影响负性注意偏向。本研究采用经颅直流电刺激技术, 考察阈下启动情绪控制目标条件下, 抑制左侧眶额皮层兴奋性是否影响负性注意偏向。结果发现, 使用阴极刺激抑制左侧OFC活动可以加快被试对与恐惧刺激位置一致的探测点的反应。该结果提示左侧眶额皮层是自动情绪调节下情绪性注意选择相关的重要脑区。     

The role of midfrontal theta oscillations across the development of cognitive control in preschoolers and school‐age children

The development of cognitive control enables children to better resist acting based on distracting information that interferes with the current action. Cognitive control improvement serves different functions that differ in part by the type of interference to resolve. Indeed, resisting to interference at the task‐set level or at the response‐preparation level is, respectively, associated with cognitive flexibility and inhibition. It is, however, unknown whether the same neural mechanism underlies these two functions across development. Studies in adults have revealed the contribution of midfrontal theta (MFT) oscillations in interference resolution. This study investigated whether MFT is involved in the resolution of different types of interference in two age groups identified as corresponding to different latent structures of executive functions. Preschool (4–6 years) and school children (6–8 years) were tested with a task involving interference at the response level and/or the task‐set level while (electroencephalogram) EEG was recorded. Behaviorally, response time and accuracy were affected by task‐set. Both age groups were less accurate when the interference occurred at the task‐set level and only the younger group showed decreased accuracy when interference was presented at the response‐preparation level. Furthermore, MFT power was increased, relative to the baseline, during the resolution of both types of interference and in both age groups. These findings suggest that MFT is involved in immature cognitive control (i.e., preschool and school‐ages), by orchestrating its different cognitive processes, irrespective of the interference to resolve and of the level of cognitive control development (i.e., the degree of differentiation of executive functions).     

Effects of three types of noncontingent auditory stimulation on vocal stereotypy in children with autism

We evaluated the effects of 3 types of noncontingent auditory stimulation (music, white noise, recordings of vocal stereotypy) on 2 children with autism who engaged in high rates of vocal stereotypy. For both participants, the music condition was the most effective in decreasing vocal stereotypy to near-zero levels, resulted in the highest parent social validity ratings, and was selected as most preferred in treatment preference evaluations.     

The psychological neuroscience of depression: implications for understanding effects of deep brain stimulation

In this article it is suggested that current psychological theories of depression presuppose that this condition will develop as a result of a vicious circle involving negatively biased communication between systems of emotional stress-/alarm-signaling, executive functions and mood regulation. These systems may from a neuroanatomical point of view be located in the limbic system, the orbitofrontal and lateral prefrontal cortex and the hypothalamus-pituitary-adrenal (HPA-) axis respectively. The theoretical and practical implications of this model for the understanding of pharmacological treatments of depression are briefly discussed and this theory is related to the catecholamine hypothesis of depression. The model is furthermore discussed in relation to deep brain stimulation (DBS) of treatment resistant major depression. Similarities and differences between this perspective and the one advocated by the "homeostatic theory" of depression are discussed. It is concluded that a topographical psychological theory may offer a useful heuristic in thinking about depression and that it offers several testable predictions about treatments of the disorder.     

The role of the human extrastriate visual cortex in mirror symmetry discrimination: a TMS-adaptation study

The human visual system is able to efficiently extract symmetry information from the visual environment. Prior neuroimaging evidence has revealed symmetry-preferring neuronal representations in the dorsolateral extrastriate visual cortex; the objective of the present study was to investigate the necessity of these representations in symmetry discrimination. This was accomplished by the use of state-dependent transcranial magnetic stimulation, which combines the fine resolution of adaptation paradigms with the assessment of causality. Subjects were presented with adapters and targets consisting of dot configurations that could be symmetric along either the vertical or horizontal axis (or they could be non-symmetric), and they were asked to perform a symmetry discrimination task on the targets while fixating the center of the screen. TMS was applied during the delay between the adapter and the test stimulus over one of four different sites: Left or Right V1/V2, or left or right dorsolateral extrastriate cortex (DLO). TMS over both Left and Right DLO reduced the adaptation effect in detecting vertical and horizontal symmetry, although the Left DLO effect on horizontal symmetry and the Right DLO effect on both vertical and horizontal symmetry were present only when considering subjects who showed a behavioral adaptation effect in the baseline No-TMS condition. Application of TMS over the Left or Right V1/V2 did not modulate the adaptation effect. Overall, these data suggest that both the Left and Right DLO contain neuronal representations tuned to mirror symmetry which play a causal role in symmetry discrimination.     

Dorsolateral prefrontal cortex mediates working memory processes in motor skill learning

Neuroimaging studies have shown that the dorsolateral prefrontal cortex (DLPFC) is recruited during motor skill learning, which suggests the involvement of the DLPFC in working memory (WM) processes, such as selection and integration of motor representations temporarily stored in WM. However, direct evidence linking activation of the DLPFC to WM storage and manipulation during motor skill learning in real-time is rare. In this study, we conducted two experiments to investigate the causal role of DLPFC activity in WM storage and manipulation during motor skill learning under low and high WM-demand conditions. Participants received continuous theta burst stimulation (cTBS) and sham stimulation (crossover design) over the left DLPFC (experiment 1) or right DLPFC (experiment 2). Before and after stimulation, participants in both experiments performed a sequential finger-tapping (SFT) task containing repeated sequence (low-WM demand) and non-repeated sequence (high-WM demand) conditions which are used to study WM processes. The number of correct sequences (NoCS) and reproduction error rate were analyzed. Learning gains in NoCS improved significantly with the practice for both sequence types in the presence of either stimulation type. Compared to sham stimulation, cTBS over the left DLPFC resulted in significantly reduced learning gains in NoCS for non-repeated sequences. These results suggest that the left DLPFC contributes to WM manipulation during motor skill learning.