Respiratory network remains functional in a mature guinea pig brainstem isolated in vitro

Summary We previously developed a perfused isolated brainstem preparation in the adult guinea pig (Morin-Surun and Denavit-Saubie 1989a) which permitted us to describe several types of rhythmic neuronal discharge. In the present study, we demonstrate that nearly all the periodic neuronal activity we recorded in the ventral respiratory areas were directly related to the respiratory-like periodic output of the hypoglossal nerve. This respiratory-like activity lasted several hours only when the brainstem was perfused by the basilar artery. This shows the necessity of the intraarterial perfusion to preserve a functional respiratory network. Analysis of the characteristics of hypoglossal respiratory-like activity shows that (1) two types of respiratory rhythms can be recorded; one with long respiratory phases (inspiratory and expiratory) and one with short respiratory phases. Depending on the preparation, either type occurs alone or intermingled with the other. (2) The shape of the inspiratory-like activity can change throughout the recording period while the periodicity remains stable. This preparation generates a respiratory rhythm and enables us to dissociate the different mechanisms involved in respiratory neurogenesis.     

The nasolacrimal duct of anuran amphibians: suggestions on its functional role in vomeronasal perception

Tear secretions discharged by the Harderian gland are suggested to function as a solvent for molecules sensed by the vomeronasal organ (VNO) in anurans. It has been assumed that chemical stimuli are absorbed at the surface of the eye to be carried – together with the lacrimal fluid – into the nasal cavity via the nasolacrimal duct. In the study presented herein, we examined the intranasal anatomy of 10 different anuran species to analyse the opening region of the nasolacrimal duct and its functional relationship with the VNO and the external naris. In addition, vital staining of the nasal cavities was conducted. Our results indicate that stimuli reaching the VNO are more likely to be ingested through the nostril than via the eye. In many cases the intranasal orifice of the nasolacrimal duct shows a close proximity to the external naris and simultaneously we observed a noticeable distance to the VNO. We suggest that the secretions of the Harderian gland are carried to the external naris by the nasolacrimal duct, where they bind chemical stimuli that are subsequently actively transported into the VNO. In some of the investigated species the opening region of the tear duct was situated in a more caudal part of the nasal cavity and closer to the VNO. In these cases a conspicuous system of channels can be found, which is suspected to carry the intruding medium of smell from the nostril to the nasolacrimal aperture.     

BA EP 对青年人脑干早期受损的诊断作用

目的：探讨脑干听觉诱发电位（BAEP）检测在诊断青年人脑干早期受损中的作用。方法：收集49例初诊时影像学结果正常而BAEP检测结果异常的青年患者的临床资料,对初诊时、3～6个月复查时的BAEP检测结果进行分析。结果：① BAEP检测复查结果显示：5例（10％）恢复正常,9例（18％）好转,31例（63％）无变化,4例（8％）加重;②4例BAEP加重患者复查CT 结果显示2例脑干腔梗,2例正常;③2例BAEP检测结果加重并CT 结果改变者均为有高血压、高血脂病、且家族史有不良生活习惯者。结论：BAEP检测结果作为脑干早期受损的较敏感指标,提示在某些病例中或更能早于影像学反映脑干早期受损状态;脑干早期受损病例的BAEP检测异常结果在短时间内不易恢复。     

Structural and functional anatomy of the palmaris brevis: grasping for answers

The palmaris brevis (PB) is a small cutaneous hand muscle that has been described as the most mysterious muscle from a functional and developmental perspective [Kaplan ( 1984 ) Kaplan's Functional and Surgical Anatomy of the Hand]. Functionally, the PB is considered to deepen the hollow of the palm and to protect the neurovasculature of the ulnar canal. Although the function of the PB has been inferred from cadaveric observations, the electromyographic (EMG) activity of this muscle has not been explored systematically during specific movements of the hand. The purpose of this study was to record PB intramuscular EMG activity during dynamic grasping tasks, and to quantify the change in PB muscle length (M_L) and thickness (M_T) incurred during maximal contraction using ultrasound imaging. Intramuscular EMG was recorded from the PB in the dominant hands of 12 healthy participants (11 males, one female; age: 27 ± 4 years) during maximal abduction, flexion and opposition of the 5th digit, and two grasping tasks. Abduction of the 5th digit yielded the greatest EMG activity in most individuals (seven out of 11), and produced significantly less PB EMG activity when compared with grasping a cylindrical‐shaped object (P = 0.003) but not a spherical‐shaped object (P = 0.130). During maximal abduction of the 5th digit, PB M_L decreased in both the left (28 ± 11%; P = 0.002) and right (32 ± 5%; P = 0.002) hands. Similarly, a concomitant increase in PB M_T was observed in the left (68 ± 30%; P = 0.002) and right (85 ± 44%; P = 0.002) hands during the same contraction. These EMG results indicate that the PB is voluntarily activated during prehensile and non‐prehensile movements of the hand with significant changes in muscle architecture. The study supports the preservation of the PB in surgical procedures based on its proposed protective role as a muscular barrier to the neurovasculature within the ulnar canal.     

Characterization and mapping of sleep–waking specific neurons in the basal forebrain and preoptic hypothalamus in mice

We recorded 872 single units across the complete sleep–waking cycle in the mouse preoptic area (POA) and basal forebrain (BFB), which are deeply involved in the regulation of sleep and wakefulness (W). Of these, 552 were sleep-active, 96 were waking-active, 106 were active during both waking and paradoxical sleep (PS), and the remaining 118 were state-indifferent. Among the 872, we distinguished slow-wave sleep (SWS)–specific, SWS/PS-specific, PS-specific, W-specific, and W/PS-specific neurons, the last group being further divided into specific tonic type I slow (TI-Ss) and specific tonic type I rapid (TI-Rs) both discharging specifically in association with cortical activation during both W and PS. Both the SWS/PS-specific and PS-specific neurons were distributed throughout a wide region of the POA and BFB, whereas the SWS-specific neurons were mainly located in the middle and ventral half of the POA and adjacent BFB, as were the W-specific and W/PS-specific neurons. At the transition from waking to sleep, the majority of SWS-specific and all SWS/PS-specific neurons fired after the onset of cortical synchronization (deactivation), whereas all W-specific and W/PS-specific neurons showed a significant decrease in firing rate >0.5 s before the onset. At the transition from SWS to W, the sleep-specific neurons showed a significant decrease in firing rate 0.1 s before the onset of cortical activation, while the W-specific and W/PS-specific neurons fired >0.5 s before the onset. TI-Ss neurons were characterized by a triphasic broad action potential, slow single isolated firing, and an antidromic response to cortical stimulation, whereas TI-Rs neurons were characterized by a narrow action potential and high frequency burst discharge in association with theta waves in PS. These data suggest that the forebrain sleep/waking switch is regulated by opposing activities of sleep-promoting (SWS-specific and SWS/PS-specific) and waking-promoting (W-specific and W/PS-specific) neurons, that the initiation of sleep is caused by decreased activity of the waking-promoting neurons (disfacilitation), and that the W/PS-specific neurons are deeply involved in the processes of cortical activation/deactivation.     

Emotion and the auditory brainstem response to speech

Effects of emotion have been reported as early as 20 ms after an auditory stimulus onset for negative valence, and bivalent effects between 30 and 130 ms. To understand how emotional state influences the listener's brainstem evoked responses to speech, subjects looked at emotion-evoking pictures while listening to an unchanging auditory stimulus (danny). The pictures (positive, negative, or neutral valence) were selected from the IAPS database and controlled for dominance and arousal. Utilizing an array of measurements to assess subcortical modulation, we have found that emotion does not substantially alter brainstem alter although there is a subtle effect of background noise suppression in both emotional conditions.     

小鼠脑干交感运动前区前阿黑皮素能神经传入投射的实验研究

目的:研究脑干交感运动前区的前阿黑皮素能神经纤维的分布及其传入投射。方法:以免疫组化法检测前阿黑皮素能神经纤维在脑干交感运动前区的分布;将霍乱毒素B微量注入小鼠脑干交感运动前区进行逆行追踪。结果:α-MSH(α-melanocyte-stimulating hormone)能神经终末密集分布于交感运动前区内,同时则未见AgRP(agouti-related protein)能神经终末,显示交感运动前区仅接受前阿黑皮素(POMC)能神经的单向调节。逆行追踪实验显示脑干交感运动前区的POMC能纤维投射来自于下丘脑弓状核/视交叉后区,而非孤束核尾侧部;统计结果表明下丘脑弓状核/视交叉后区向脑干交感运动前区的神经投射中有近一半为POMC能投射。结论:小鼠下丘脑的POMC能神经元可直接投射到脑干交感运动前区,该神经通路在能量平衡的调节中可能发挥重要的作用。     

Somatotopic arrangement and location of the corticospinal tract in the brainstem of the human brain

The corticospinal tract (CST) is the most important motor pathway in the human brain. Detailed knowledge of CST somatotopy is important in terms of rehabilitative management and invasive procedures for patients with brain injuries. In this study, I conducted a review of nine previous studies of the somatotopical location and arrangement at the brainstem in the human brain. The results of this review indicated that the hand and leg somatotopies of the CST are arranged medio-laterally in the mid to lateral portion of the cerebral peduncle, ventromedial-dorsolaterally in the pontine basis, and medio-laterally in the medullary pyramid. However, few diffusion tensor imaging (DTI) studies have been conducted on this topic, and only nine have been reported: midbrain (2 studies), pons (4 studies), and medulla (1 study). Therefore, further DTI studies should be conducted in order to expand the literature on this topic. In particular, research on midbrain and medulla should be encouraged.     

Mapping the human brainstem: Brain nuclei and fiber tracts at 3 T and 7 T

Structural high‐resolution imaging of the brainstem can be of high importance in clinical practice. However, ultra‐high field magnetic resonance imaging (MRI) is still restricted in use due to limited availability. Therefore, quantitative MRI techniques (quantitative susceptibility mapping [QSM], relaxation measurements [ , R₁ ], diffusion tensor imaging [DTI]) and T₂ ‐ and proton density (PD)‐weighted imaging in the human brainstem at 3 T and 7 T are compared. Five healthy volunteers (mean age: 21.5 ± 1.9 years) were measured at 3 T and 7 T using multi‐echo gradient echo sequences for susceptibility mapping and relaxometry, magnetization‐prepared 2 rapid acquisition gradient echo sequences for R₁ relaxometry, turbo‐spin echo sequences for PD‐ and T₂ ‐weighted imaging and readout‐segmented echo planar sequences for DTI. Susceptibility maps were computed using Laplacian‐based phase unwrapping, V‐SHARP for background field removal and the streaking artifact reduction for QSM algorithm for dipole inversion. Contrast‐to‐noise ratios (CNRs) were determined at 3 T and 7 T in ten volumes of interest (VOIs). Data acquired at 7 T showed higher CNR. However, in four VOIs, lower CNR was observed for at 7 T. QSM was shown to be the contrast with which the highest number of structures could be identified. The depiction of very fine tracts such as the medial longitudinal fasciculus throughout the brainstem was only possible in susceptibility maps acquired at 7 T. DTI effectively showed the main tracts (crus cerebri, transverse pontine fibers, corticospinal tract, middle and superior cerebellar peduncle, pontocerebellar tract, and pyramid) at both field strengths. Assessing the brainstem with quantitative MRI methods such as QSM, , as well as PD‐ and T₂ ‐weighted imaging with great detail, is also possible at 3 T, especially when using susceptibility mapping calculated from a gradient echo sequence with a wide range of echo times from 10.5 to 52.5 ms. However, tracing smallest structures strongly benefits from imaging at ultra‐high field.     

Auditory brainstem responses in the aged cat

Auditory brainstem responses (ABRs) were compared in young adult and aged cats. Mean thresholds for click-evoked ABRs were greater in the aged cats. Clicks normalized to 15 and 30 dB above individual thresholds at rates of 10, 20, 50 and 100/sec evoked ABRs with similar latencies and central conduction times in both groups. Background noise at equal intensity for all cats completely suppressed ABRs evoked by clicks 30 dB above threshold in 2/3 of the young but none of the old cats. As rise time of a 25 msec noise burst at equal intensity for all cats increased 1, 2, 5, and 10 msec, latency of wave 4 increased more for the old cats than for the young. Summed monaural ABRs from both ears were greater than binaural ABRs for waves 4 and 5 in both groups. These data indicate peripheral auditory dysfunction in aged cats but little abnormality in auditory brainstem transmission with click intensity normalized for ABR threshold.     

Measurement of signal and noise characteristics in ongoing auditory brainstem response averaging

Although diagnostic testing with auditory evoked potentials (EPs) has become routine, quantitative measurements of signal and noise are still lacking. In this study, current signal, power, noise power, and signal-to-noise ratio (SNR) estimation formulas are reviewed and applied to auditory brainstem response averaging. Single-sweep responses to individual sound stimuli are recorded and estimation formulas are evaluated during off-line averaging under various sound level and noise conditions. The results show that the quality of the averaged EP can be quantitatively assessed by the continuous display of the SNR and residual noise estimates during the averaging process. This method also allows the study of different types of averaging techniques to improve EP response acquisition.     

婴儿痉挛症脑干听觉诱发电位的奇异性初步分析

目的运用建立在子波变换基础上的Lipschitz指数和模极大值两种奇异性检测方法分析婴儿痉挛症患儿脑干听觉诱发电位,试图解释婴儿痉挛症患儿智能迟滞的原因,从神经电生理的信息传递的角度来证明脑干是责任病灶。方法本实验病例分为2组,正常组12例,平均年龄(6.325±3.210)岁;婴儿痉挛症组13例,平均年龄(4.638±3.986)岁。所有病例均行脑干听觉诱发电位检查,并用建立在子波变换基础上的Lipschitz指数和模极大值两种奇异性检测方法进行分析。结果Lipschitz指数尖峰在正常幼儿0～2ms和5～7ms各出现1次,在婴儿痉挛症患儿尖峰出现在0～2ms和5～7ms之后。正常幼儿模极大值在一定范围内连续性好,而在婴儿痉挛症患儿则中断。结论研究发现在婴儿痉挛症患儿的脑干、尤其是上部脑干对上行传导的信息耦合性差,从而影响患儿的智能发育。     

The role of testosterone in the feedback control of male FSH and LH secretion

Summary Intramuscular administration of 250 mg testosterone oenanthate per week over a period of 21 weeks treatment rapidly and sustainedly suppressed serum LH as well as FSH levels in seven normal males, while serum testosterone rose by a factor of approximately two. These together with other data provide increasing evidence for a feedback control of FSH secretion by gonadal steroids in the male in addition to the already described but as yet undefined tubular testicular factor.     

全麻病人用纳络酮催醒时的BAEP

观察全麻病人用纳络酮催醒时的脑干诱发电位（ＢＡＥＰ）变化。结果表明，全麻诱导期Ⅰ、Ⅲ、Ⅴ波的潜伏期都较清醒时延长，在麻醉维持期（催醒前）则进一步延长（Ｐ＜０．０１）。静注纳络酮后各波的ＰＬ均缩短，Ⅰ～Ⅲ，Ⅲ～Ⅴ，Ⅰ～Ⅴ波的波间期亦缩短，提示ＢＡＥＰ的变化可作为判断麻醉深浅的客观指标，用ＢＡＥＰ变化来观察纳络酮催醒具有准确和灵敏的特点。     

Cholinergic mechanisms of the medial preoptic areas of the hypothalamus in the control of thermoregulation and the states of sleep and waking in pigeons

Cholinergic mechanisms in the medial preoptic area of the hypothalamus were found to be involved in controlling the time characteristics of the states of sleep and waking, as well as measures of thermoregulation, in pigeons. Muscarinic and nicotinic cholinergic receptors were involved in the mechanisms maintaining waking. Activation of muscarinic cholinoreceptors in the medial preoptic area was accompanied by increases in brain temperature due to increases in peripheral vasoconstriction and decreases in the level of muscle contractile activity. Activation of nicotinic cholinoreceptors in this area led to decreases in brain temperature and increases in the level of contractile muscle activity. Comparative analysis of the results of experiments and previous studies showed that changes in brain temperature in pigeons occurring on activation of cholinoreceptors depend on the type of cholinoreceptor activated but are independent of their location in the preoptic area of the hypothalamus. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 6, pp, 681–688, June, 2008.     

Effect of the ketamine/xylazine anesthetic on the auditory brainstem response of adult gerbils

The auditory brainstem response (ABR) is a test widely used to assess the integrity of the brain stem. Although it is considered to be an auditory-evoked potential that is influenced by the physical characteristics of the stimulus, such as rate, polarity and type of stimulus, it may also be influenced by the change in several parameters. The use of anesthetics may adversely influence the value of the ABR wave latency. One of the anesthetics used for ABR assessment, especially in animal research, is the ketamine/xylazine combination. Our objective was to determine the influence of the ketamine/xylazine anesthetic on the ABR latency values in adult gerbils. The ABRs of 12 adult gerbils injected with the anesthetic were collected on three consecutive days, or a total of six collections, namely: pre-collection and A, B, C, D, and E collections. Before each collection the gerbil was injected with a dose of ketamine (100 mg/kg)/xylazine (4 mg/kg). For the capture of the ABR, 2000 click stimuli were used with rarefaction polarity and 13 stimuli per second, 80 dBnHL intensity and in-ear phones. A statistically significant difference was observed in the latency of the V wave in the ABR of gerbils in the C and D collections compared to the pre-, A and E collections, and no difference was observed between the pre-, A, B, and E collections. We conclude that the use of ketamine/xylazine increases the latency of the V wave of the ABR after several doses injected into adult gerbils; thus, clinicians should consider the use of this substance in the assessment of ABR.