Direct electrical stimulation mapping of cognitive functions in the human brain

ABSTRACT

Direct electrical stimulation (DES) is a well-established clinical tool for mapping cognitive functions while patients are undergoing awake neurosurgery or invasive long-term monitoring to identify epileptogenic tissue. Despite the proliferation of a range of invasive and noninvasive methods for mapping sensory, motor and cognitive processes in the human brain, DES remains the clinical gold standard for establishing the margins of brain tissue that can be safely removed while avoiding long-term neurological deficits. In parallel, and principally over the last two decades, DES has emerged as a powerful scientific tool for testing hypotheses of brain organization and mechanistic hypotheses of cognitive function. DES can cause transient “lesions” and thus can support causal inferences about the necessity of stimulated brain regions for specific functions, as well as the separability of sensory, motor and cognitive processes. This Special Issue of Cognitive Neuropsychology emphasizes the use of DES as a research tool to advance understanding of normal brain organization and function.     

Injectable microstimulator for functional electrical stimulation

A family of digitally controlled devices is constructed for functional electrical stimulation in which each module is an hermetically sealed glass capsule that is small enough to be injected through the lumen of a hypodermic needle. The overall design and component characteristics of microstimulators that receive power and command signals by inductive coupling from a single, externally worn coil are described. Each device stores power between stimulus pulses by charging an electrolytic capacitor formed by its two electrodes, made of sintered, anodised tantalum and electrochemically activated iridium, respectively. Externally, a highly efficient class E amplifier provides power and digitally encoded command signals to control the amplitude, duration and timing of pulses from up to 256 such microstimulators.     

Improving respiration in patients with tetraplegia by functional electrical stimulation: an anatomical perspective

Patients with tetraplegia often have respiratory complications because of paralysis of the abdominal and intercostal muscles. Functional electrical stimulation (FES) has been used to improve breathing in these patients by applying surface stimulation to the abdominal muscles. We aimed to find the best nerves to stimulate directly to increase tidal volume and make cough more effective. Surface electrodes were placed on a patient's abdominal wall to find the optimum points for surface stimulation. These positions were plotted on a transparent sheet. The abdomino-intercostal nerves were dissected in five male dissecting room cadavers matched for size with the patient. The plastic sheet was then superimposed over each of the dissections to clarify the relationship between optimum surface stimulation points and the underlying nerves. Results show that the optimum surface stimulation points overlie the course of abdomino-intercostal nerves T9, 10, and 11. The success with selecting stimulation points associated with T9, 10, and 11 is probably because of the large mass of abdominal muscle supplied by these nerves. The constant position of the nerves below the ribs makes the intercostal space a possible site for direct stimulation of the abdomino-intercostal nerves.     

Investigating the functional neuroanatomy of concrete and abstract word processing through direct electric stimulation (DES) during awake surgery

ABSTRACT

Neuropsychological, neuroimaging and electrophysiological studies demonstrate that abstract and concrete word processing relies not only on the activity of a common bilateral network but also on dedicated networks. The neuropsychological literature has shown that a selective sparing of abstract relative to concrete words can be documented in lesions of the left anterior temporal regions. We investigated concrete and abstract word processing in 10 patients undergoing direct electrical stimulation (DES) for brain mapping during awake surgery in the left hemisphere. A lexical decision and a concreteness judgment task were added to the neuropsychological assessment during intra-operative monitoring. On the concreteness judgment, DES delivered over the inferior frontal gyrus significantly decreased abstract word accuracy while accuracy for concrete words decreased when the anterior temporal cortex was stimulated. These results are consistent with a lexical–semantic model that distinguishes between concrete and abstract words related to different neural substrates in the left hemisphere.     

Direct electrical stimulation of the left frontal aslant tract disrupts sentence planning without affecting articulation

ABSTRACT

Sentence production involves mapping from deep structures that specify meaning and thematic roles to surface structures that specify the order and sequencing of production ready elements. We propose that the frontal aslant tract is a key pathway for sequencing complex actions with deep hierarchical structure. In the domain of language, and primarily with respect to the left FAT, we refer to this as the ‘Syntagmatic Constraints On Positional Elements’ (SCOPE) hypothesis. One prediction made by the SCOPE hypothesis is that disruption of the frontal aslant tract should disrupt sentence production at grammatical phrase boundaries, with no disruption of articulatory processes. We test this prediction in a patient undergoing direct electrical stimulation mapping of the frontal aslant tract during an awake craniotomy to remove a left frontal brain tumor. We found that stimulation of the left FAT prolonged inter-word durations at the start of grammatical phrases, while inter-word durations internal to noun phrases were unaffected, and there was no effect on intra-word articulatory duration. These results provide initial support for the SCOPE hypothesis, and motivate novel directions for future research to explore the functions of this recently discovered component of the language system.     

及早经皮穴位电针刺激对高龄老年髋部骨折术后认知的影响

目的:研究经皮穴位电针刺激及早干预对老年髋部骨折术后认知功能及炎症因子的影响。方法:80岁以上髋部 骨折患者40例,随机分为对照组（A组, 20例）和电刺激组（B组,20例）。两组患者均采用腰-硬联合麻醉。B组患者术前 2 d选取百会穴和风池穴行经皮电针刺激,3次/d,30 min/次;麻醉操作完成后行穴位持续刺激至手术结束。A组患者仅在 相应穴位贴电极未行电针刺激。于入院时、术后24、72 h 3个时点对患者进行MMSE评定,若术后评分降低一个标准差或 以上者即认定发生术后认知功能障碍（POCD）。所有患者在入院时、术毕即刻、术后24 和72 h 抽取静脉血,测定血清 IL-6、IL-10 和S100β 蛋白水平。结果:A组术后24、72 h POCD 发生率分别为65%（13/20）和60%（12/20）,高于B组的 35%（7/20）和25%（5/20）,差异有统计学意义（P<0.05）;B组术后各时间点血清IL-6、IL-10和S100β蛋白水平均显著低于 对照组同时间点,差异有统计学意义（P<0.05）。结论:及早经皮穴位电针干预有利于改善高龄老年髋部骨折术后的认知 功能状态,有效降低患者POCD的发生率。这可能与抑制其血清IL-6、IL-10、S100B蛋白的过度表达、减轻患者脑损伤的 程度有关。     

多电极联合电刺激神经调控模型建立与分析

目的:分析电刺激信号在人体组织中的扩散情况,为多电极联合刺激提供理论依据。方法:采用以电磁仿真标准单层人体头部模型为研究对象的几何结构模型,假定模型中填充物为肌肉组织,建立具有肌肉特性的有限元模型。向模型注入20 mA的直流电信号,通过多物理场仿真软件COMSOL Multiphysics 5.5计算分析信号在简化头部模型中的信号传播机制。结果:信号主要集中在电极周围;多电极联合刺激时,在模型的几何中心处存在信号叠加,信号在该处存在增强的趋势;同时,通过xy截面分析发现,在均匀的肌肉组织中,信号衰减强度约为8 dB/cm。结论:在简化头部模型中,多电极联合刺激能够在头部截面几何中心形成信号增强的趋势。     

Repolarization of ventricular myocardium in atrioventricular electrical stimulation of the heart in dogs

The duration of ventricular myocardium excitation increases during atrioventricular stimulation of dog heart and the sequence of depolarization of the right and left ventricles is desynchronized. Significant shortening of the activation-recovery interval in the intramural and subendocardial layers of the left ventricular base leads to modification of the repolarization sequence in this area and to an increase of total dispersion of activation-recovery intervals in the cardiac ventricles, as a result of which repolarization sequence starts partially repeating the depolarization sequence. Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 146, No. 8, pp. 131–134, August, 2008     

穴位贴敷联合经皮穴位电刺激对腹腔镜术后胃肠蠕动功能的

目的:探讨穴位贴敷联合经皮穴位电刺激对腹腔镜术后胃肠蠕动功能的影响。方法:选取拟择期实施腹腔镜手术的116例患者为研究对象,根据简单随机数表法将所有研究对象分为观察组（58例）和对照组（58例）。两组患者均行腹腔镜手术,观察组给予穴位贴敷联合经皮穴位电刺激治疗,对照组仅给予经皮穴位电刺激治疗。比较两组患者的治疗效果、胃肠蠕动功能相关指标、术前术后胃动素水平、术后3 d内恶心呕吐及腹胀发生率。结果:观察组有效率显著高于对照组（96.55% vs 79.31%, P<0.05）。观察组胃肠蠕动恢复时间、首次排气时间及首次排便时间均短于对照组（P<0.05）。两组患者术前胃动素水平比较,差异无统计学意义（P>0.05）;观察组胃动素水平术后第1、2天显著低于术前（P<0.05）,第3天与术前比较差异无统计学意义（P>0.05）;对照组术后第1、2、3天胃动素水平显著低于术前（P<0.05）;观察组术后第1、2、3天胃动素水平均高于对照组（P<0.05）。观察组术后3 d内恶心呕吐、腹胀发生率均低于对照组（P<0.05）。结论:穴位贴敷联合经皮穴位电刺激能够有效改善腹腔镜术后胃肠蠕动功能,提升胃动力,促使胃肠蠕动功能尽快恢复,减少术后恶心呕吐及腹胀发生,有较好的临床推广应用价值。     

Open-loop position control of the knee joint using electrical stimulation of the quadriceps and hamstrings

The clinical acceptability of functional electrical stimulation (FES) as an aid for restoration of paraplegic gait is limited by the inability to accurately and repeatedly position the lower extremity. To gain insight into the causes of and possible solutions to this problem, the responses of the quadriceps and hamstrings to FES were studied in able-bodied subjects. Isometric torque was dependent on knee angle and changed unpredictably with time. An open-loop feedforward knee-joint position controller was also tested. The results demonstrated that it is beneficial to account for the dependence of torque on position, that modifications to this openloop controller might improve accuracy and that closed-loop control may be essential for functional restoration of gait.     

Field distribution of epidural electrical stimulation

Epidural electrical stimulation has been applied in clinics for many years. However, there is still a concern about possible injury to spinal nerves. This study investigated electrical field and current density distribution during direct epidural electrical stimulation. Field distribution models were theoretically deduced, while the distribution of potentials and current were analyzed. The current density presented an increase of 70–80%, with one peak value ranging from −85° to 85° between the two stimulated poles. The effect of direct epidural electrical stimulation is mainly on local tissue surrounding the electrodes, concentrated around the two stimulated positions.     

核素显像评价电刺激对健康青年人小肠运动功能影响的试验研究

目的利用放射性核素显像研究十二指肠电刺激对人小肠通过时间的影响。方法12例健康青年志愿者,男女各6例,年龄21～25岁,中位年龄23岁。在胃镜引导下留置导管至十二指肠水平部,并安置电极,将99mTc-DTPA(二乙撑三胺五乙酸)和乳果糖混合液注入导管,用单光子发射式计算机断层仪(SPECT)进行连续小肠显像。择日对受试者进行电刺激,刺激条件:频率13Hz、波宽300ms、刺激强度5mA的方波,采用上述方法进行显像。使用感兴趣区分析法,生成小肠时间-放射性曲线,计算出小肠半排时间(T50),比较刺激前后小肠半排时间的变化。结果电刺激前后小肠平均半排时间分别为(49.5±15.8)min和(29.6±10.9)min,刺激前后T50变化有统计学意义(P<0.01)。结论放射性核素显像能很好地反映小肠运动变化,十二指肠电刺激能明显加快小肠运动。     

Short-term effects of functional electrical stimulation on motor-evoked potentials in ankle flexor and extensor muscles

Stimulating sensory afferents can increase corticospinal excitability. Intensive use of a particular part of the body can also induce reorganization of neural circuits (use-dependent plasticity) in the central nervous system (CNS). What happens in the CNS when the nerve stimulation is applied in concert with the use of particular muscle groups? The purpose of this study was to investigate short-term effects of electrical stimulation of the common peroneal (CP) nerve during walking on motor-evoked potentials (MEPs) in the ankle flexors and extensors in healthy subjects. Since the stimulation was applied during the swing phase of the step cycle when the ankle flexors are active, this is referred to as functional electrical stimulation (FES). The following questions were addressed: (1) can FES during walking increase corticospinal excitability more effectively than passively received repetitive nerve stimulation and (2) does walking itself improve the descending connection. FES was delivered using a foot drop stimulator that activates ankle dorsiflexors during the swing phase of the step cycle. MEPs in the tibialis anterior (TA) and soleus muscles were measured before, between, and after periods of walking with or without FES, using transcranial magnetic stimulation. After 30 min of walking with FES, the half-maximum peak-to-peak MEP (MEP_h) in the TA increased in amplitude and this facilitatory effect lasted for at least 30 min. In contrast, walking had no effects on the TA MEP_h without FES. The increase in the TA MEP_h with FES (~40%) was similar to that with repetitive CP nerve stimulation at rest. The soleus MEP_h was also increased after walking with FES, but not without FES, which differs from the previous observation with CP nerve stimulation at rest. With FES, the TA silent period at MEP_h was unchanged or slightly decreased, while it increased after walking without FES. Increased cortical excitability accompanied by unchanged cortical inhibition (no changes in the silent period with FES) suggests that FES did not simply increase general excitability of the cortex, but had specific effects on particular cortical neurons.     

Influence of transcutaneous electrical stimulation on heterotopic ossification: an experimental study in Wistar rats

Heterotopic ossification (HO) is a metaplastic biological process in which there isnewly formed bone in soft tissues, resulting in joint mobility deficit and pain.Different treatment modalities have been tried to prevent HO development, but thereis no consensus on a therapeutic approach. Since electrical stimulation is a widelyused resource in physiotherapy practice to stimulate joint mobility, with analgesicand anti-inflammatory effects, its usefulness for HO treatment was investigated. Weaimed to identify the influence of electrical stimulation on induced HO in Wistarrats. Thirty-six male rats (350-390 g) were used, and all animals were anesthetizedfor blood sampling before HO induction, to quantify the serum alkaline phosphatase.HO induction was performed by bone marrow implantation in both quadriceps of theanimals, which were then divided into 3 groups: control (CG), transcutaneouselectrical nerve stimulation (TENS) group (TG), and functional electrical stimulation(FES) group (FG) with 12 rats each. All animals were anesthetized and electricallystimulated twice per week, for 35 days from induction day. After this period, anotherblood sample was collected and quadriceps muscles were bilaterally removed forhistological and calcium analysis and the rats were killed. Calcium levels in musclesshowed significantly lower results when comparing TG and FG (P<0.001) and betweenTG and CG (P<0.001). Qualitative histological analyses confirmed 100% HO in FG andCG, while in TG the HO was detected in 54.5% of the animals. The effects of themuscle contractions caused by FES increased HO, while anti-inflammatory effects ofTENS reduced HO.     

Eye movements in the cat evoked by electrical stimulation of the outer geniculate body

New data were obtained in experiments with unanesthetized animals showing that electrical stimulation of the structures of the outer geniculate body of the cat elicits goal-directed eye movements. Relationships were found between eye-movement amplitude and direction and the position of the eye at the instant of stimulation, as well as the position of the stimulating electrodes in the outer geniculate body. A scheme is proposed for the multilevel interaction of the visual and oculomotor systems during their functioning, and a possible relation is discussed between the described phenomenon and the mechanisms responsible for the foveation of objects during their recognition.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 69, No. 2, pp. 167–175, February, 1983.     

Expression of the c-Fos gene in the rat hypothalamus in electrical pain stimulation and UHF stimulation of the skin

Studies of the pattern of activation of hypothalamic cells in conditions of electrical pain stimulation demonstrated an increase in the proportion of c-Fos-positive cells (to 72.02–98.95%), predominantly affecting cells of size 10–50 μm². UHF irradiation of the skin activated hypothalamic cells of size 10–70 μm² in the paraventricular and dorsomedial nuclei and in the periforniceal zone of the lateral hypothalamic field. Combined action of UHF irradiation of the skin and electrical pain stimulation led to decreases in the proportions of cells activated as a result of pain stimulation in the anterior hypothalamic field, the ventromedial nucleus, and the basal part of the lateral hypothalamic field. Changes in the distribution of activated cells by size (mainly a reduction in the proportion of cells of area 10–30 μm² and an increase in the proportion of larger cells) were detected in the ventromedial nucleus and the basal part of the lateral field. UHF irradiation of the skin was found to have a modifying effect, consisting of a reduction in the degree of activation of hypothalamic cells evoked by electrical pain stimulation. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 93, No. 3, pp. 255–263, March, 2007.     

Reliability of neural-network functional electrical stimulation gait-control system

Functional electrical stimulation (FES) has been used for restoring walking in spinal-cord injured (SCI) persons. Using artificial intelligence (Al), FES controllers have been developed that allow the automatic phasing of stimulation, to replace the function of hand or heel switches. However, there has been no study to evaluate the reliability of these Al systems. Neural networks were used to construct FES controllers to control the timing of stimulation. Different numbers of sensors in the sensor set and different numbers of data points from each sensor were used. Two incomplete-SCI subjects were recruited, and each was tested on three separate occasions. The results show the neural-network controllers can maintain a high accuracy (around 90% for the two- and three-sensor groups and 80% for the onesensor group) over a period of six months. Two or three sensors were sufficient to provide enough information to construct a reliable FES control system, and the number of data points did not have any effect on the reliability of the system.     

Reliability of neural-network functional electrical stimulation gait-control system

Functional electrical stimulation (FES) has been used for restoring walking in spinal-cord injured (SCI) persons. Using artificial intelligence (AI), FES controllers have been developed that allow the automatic phasing of stimulation, to replace the function of hand or heel switches. However, there has been no study to evaluate the reliability of these AI systems. Neural networks were used to construct FES controllers to control the timing of stimulation. Different numbers of sensors in the sensor set and different numbers of data points from each sensor were used. Two incomplete-SCI subjects were recruited, and each was tested on three separate occasions. The results show the neural-network controllers can maintain a high accuracy (around 90% for the two- and three-sensor groups and 80% for the one-sensor group) over a period of six months. Two or three sensors were sufficient to provide enough information to construct a reliable FES control system, and the number of data points did not have any effect on the reliability of the system.