Pontine reticulospinal projections in the neonatal mouse: Internal organization and axon trajectories

We recently characterized physiologically a pontine reticulospinal (pRS) projection in the neonatal mouse that mediates synaptic effects on spinal motoneurons via parallel uncrossed and crossed pathways (Sivertsen et al. [2014] J Neurophysiol 112:1628–1643). Here we characterize the origins, anatomical organization, and supraspinal axon trajectories of these pathways via retrograde tracing from the high cervical spinal cord. The two pathways derive from segregated populations of ipsilaterally and contralaterally projecting pRS neurons with characteristic locations within the pontine reticular formation (PRF). We obtained estimates of relative neuron numbers by counting from sections, digitally generated neuron position maps, and 3D reconstructions. Ipsilateral pRS neurons outnumber contralateral pRS neurons by threefold and are distributed about equally in rostral and caudal regions of the PRF, whereas contralateral pRS neurons are concentrated in the rostral PRF. Ipsilateral pRS neuron somata are on average larger than contralateral. No pRS neurons are positive in transgenic mice that report the expression of GAD, suggesting that they are predominantly excitatory. Putative GABAergic interneurons are interspersed among the pRS neurons, however. Ipsilateral and contralateral pRS axons have distinctly different trajectories within the brainstem. Their initial spinal funicular trajectories also differ, with ipsilateral and contralateral pRS axons more highly concentrated medially and laterally, respectively. The larger size and greater number of ipsilateral vs. contralateral pRS neurons is compatible with our previous finding that the uncrossed projection transmits more reliably to spinal motoneurons. The information about supraspinal and initial spinal pRS axon trajectories should facilitate future physiological assessment of synaptic connections between pRS neurons and spinal neurons. J. Comp. Neurol. 524:1270–1291, 2016. © 2015 Wiley Periodicals, Inc.     

Functional connectivity associated with hand shape generation: Imitating novel hand postures and pantomiming tool grips challenge different nodes of a shared neural network

Clinical research suggests that imitating meaningless hand postures and pantomiming tool‐related hand shapes rely on different neuroanatomical substrates. We investigated the BOLD responses to different tasks of hand posture generation in 14 right handed volunteers. Conjunction and contrast analyses were applied to select regions that were either common or sensitive to imitation and/or pantomime tasks. The selection included bilateral areas of medial and lateral extrastriate cortex, superior and inferior regions of the lateral and medial parietal lobe, primary motor and somatosensory cortex, and left dorsolateral prefrontal, and ventral and dorsal premotor cortices. Functional connectivity analysis revealed that during hand shape generation the BOLD‐response of every region correlated significantly with every other area regardless of the hand posture task performed, although some regions were more involved in some hand postures tasks than others. Based on between‐task differences in functional connectivity we predict that imitation of novel hand postures would suffer most from left superior parietal disruption and that pantomiming hand postures for tools would be impaired following left frontal damage, whereas both tasks would be sensitive to inferior parietal dysfunction. We also unveiled that posterior temporal cortex is committed to pantomiming tool grips, but that the involvement of this region to the execution of hand postures in general appears limited. We conclude that the generation of hand postures is subserved by a highly interconnected task‐general neural network. Depending on task requirements some nodes/connections will be more engaged than others and these task‐sensitive findings are in general agreement with recent lesion studies. Hum Brain Mapp 36:3426–3440, 2015. © 2015 Wiley Periodicals, Inc.     

Soleus H-Reflex Gain,Threshold, and Amplitude as Function of Body Posture and Load in Spinal Cord Intact and Injured Subjects

In this study, we established parameters of the soleus H-reflex excitability in response to changes of posture and load in 8 chronic spinal cord injured (SCI) and 10 spinal-intact subjects. The soleus H-reflex recruitment curve was established in all subjects while they were supine, seated, and standing on a stable treadmill. During standing, body weight support (BWS) was provided via an upper body harness and ranged in SCI subjects from 20%–50% and in spinal-intact subjects was set at 0% and 50%. Stimuli corresponding to the H-threshold (H_th), maximal H-reflex amplitude (H_max), and 50% of H_max as well as the reflex gain were estimated based on a sigmoid function of the ascending limb of the soleus H-reflex recruitment curve. The soleus H-reflex gain, H_max amplitude, and stimuli corresponding to H_th, 50% of H_max, and H_max were increased in SCI subjects regardless of the body position and loading. Further, the reflex gain was not modulated appropriately during conditions of weight bearing in SCI subjects. Impaired spinal reflex excitability in SCI subjects is accompanied by changes of the H-reflex recruitment curve parameters regardless of presence or absence of body loading.     

听神经鞘瘤切除术术中体位与术后并发症相关性分析（附90例报告）

目的探讨听神经鞘瘤经枕下乙状窦后入路肿瘤切除术中体位与术后并发症的相关性。方法对2004年至2007年收治的90例听神经鞘瘤病人，应用显微外科技术在显微镜下行枕下乙状窦后入路肿瘤切除术，术中病人体位取坐位58例，侧卧位32例，回顾性分析术后一系列并发症的发生与术中体位的关系。结果术后出现颅内血肿5例，其中术中采取坐位者4例（6．90％），侧卧位者1例（3．12％）；术后出现颅内积气47例，其中坐位者38例（65．52％），侧卧位者9例（28．12％），经统计学分析，采取两种不同体位手术的病人颅内积气发生率差异显著（P〈0.05）。结论侧卧位下较坐位下行枕下乙状窦后入路听神经鞘瘤切除术能更有效降低听神经鞘瘤术后颅内积气的发生率。     

三种不同体位对剖宫产产妇血流动力学的影响

目的探讨剖宫产腰麻一硬膜外联合麻醉（CSEA）后不同体位调节方法对血流动力学的影响。方法选择足月妊娠行剖宫产产妇150例,随机分为A、B、C三组,各50例。A组麻醉后保持左侧卧位5min后平卧并右侧臀下垫高15°;B组麻醉后立即取平卧位并右侧臀下垫高15°;C组麻醉后立即取水平仰卧位。观察三组麻醉后不同体位下血流动力学的变化。结果C组血压下降最严重,在麻醉后2、5、10min血压下降幅度与A、B组比较有显著性差异（P〈0．01）,B组和C组比较无显著性差异（P〉0．05）。结论剖宫产CSEA麻醉后低血压主要是由于血流动力学调节不能及时代偿,麻醉后血管扩张和下半身血液回流障碍所致。麻醉后保持数分钟侧卧位可以有效防止严重低血压发生。     

Cells in monkey STS responsive to articulated body motions and consequent static posture: a case of implied motion?

We show that populations of visually responsive cells in the anterior part of the superior temporal sulcus (STSa) of the macaque monkey code for the sight of both specific articulated body actions and the consequent articulated static body postures. We define articulated actions as actions where one body part (e.g. a limb or head) moves with respect to the remainder of the body which remains static; conversely non-articulated actions are actions where the equivalent body parts do not move with respect to each other but move as one. Similarly, articulated static body postures contain a torsion or rotation between parts, while non-articulated postures do not. Cells were tested with the sight of articulated and non-articulated actions followed by the resultant articulated or non-articulated static body postures. In addition, the static body postures that formed the start and end of the actions were tested in isolation. The cells studied did not respond to the sight of non-articulated static posture, which formed the starting-point of the action, but responded vigorously to the articulated static posture that formed the end-point of the action. Other static postures resembling the articulated end-point posture, but which were in a more relaxed muscular state (i.e. non-articulated), did not evoke responses. The cells did not respond to body actions that were less often associated with the effective static articulated postures. Our results suggest that the cells' responses were related to the implied action rather than the static posture per se. We propose that the neural representations in STSa for actual biological motion may also extend to biological motion implied from static postures. These representations could play a role in producing the activity in the medial temporal/medial superior temporal (V5(MT)/MST) areas reported in fMRI studies when subjects view still photographs of people in action.     

The effects of instability and additional hand support on anticipatory postural adjustments in leg, trunk, and arm muscles during standing

We report data from a patient, FK, who manifested 'utilisation' behaviour after bilateral lesions of the medial frontal and anterior temporal lobes. In tasks requiring actions to be made with the hand compatible with the orientation of a cup, FK was able to ignore irrelevant distractors that fell in the path of action to the target. However, errors were made when the distractors were other cups. These errors reflected the hand selected on the basis of the properties of the target, suggesting that distractors competed to control the action after selection of the target. When similar in kind to the target, distractors sometimes captured the action. However, distractors that were associated with an action related to the target blocked the usual hand response. These results suggest a complex interlocking of attention and action when grasping responses are made to a target amongst distractors. There is initial selection of the target, but distractors on the path of a reach can then compete for control of the action. Distractors can be inhibited if they do not match the properties of the specified target, and there can also be inhibition of concurrently activated responses. We show that the magnitude of the inhibition is proportional to the strength of learned object-action associations.     

The influence of posture upon cardiovascular dynamics throughout pregnancy

Systemic blood pressure (measured with a zero-randomized sphyngmomanometer), stroke volume and heart-rate (measured with a Minnesota Impedance Cardiograph), hematocrit and their derivatives — cardiac output, pulse pressure, mean arterial blood pressure and peripheral vascular resistance, were assessed in 19 nonpregnant women of child-bearing age and in 27 patients who were examined at regular intervals on 12 to 15 occasions from 8 to 11 wk of pregnancy until 6-wk postpartum. Readings were made with the subjects in each of six positions: supine, reclining, left and right lateral, left and right tilt. The purpose of this paper is to compare the results of these different postures.Systolic and diastolic blood pressure readings were lowest in the left lateral and second lowest in the left tilt. We suggest that this reflects a hydrostatic pressure difference. Stroke volume and cardiac output were lowest in the right lateral and second lowest in the right tilt. Thus, the derived values of peripheral resistance were lowest when subjects were turned towards the left and highest when turned towards the right.The rank orders of values were maintained with impressive consistency between subjects (pregnant and nonpregnant) and throughout pregnancy, reaching levels of statistical significance in almost all instances. No evidence was found that aortocaval compression led to a change in the measured attributes of central cardiovascular dynamics. For the ‘normal unembarrassed parturient’ it is suggested that aortocaval compression is rapidly succeeded by a restabilization of these attributes to their previous levels, reflecting the prompt establishment of a suitably diminished circulating blood volume within a reduced vascular capacity. It is nevertheless likely that aortocaval compression will interfere markedly with uteroplacental vascular dynamics and hence pose a hazard to the fetus.     

Effects of body posture on local sweating and sudomotor outflow as estimated using sweat expulsion

To estimate the effects of changes in body posture on sudomotor function, sweat rates on the forearm, chest and thigh, tympanic temperature (Tty), and skin temperatures were recorded in an upright sitting and a supine position under a hot environment of 40 degrees C Ta and 40% relative humidity for 60 min. Sweat expulsions were identified on sweat rate curves and their rates (Fsw) were calculated. Tty was higher, and its initial fall was greater, in the supine position than in the sitting position. On the forearm and the chest, the regression line relating sweat rate to mean body temperature (Tmb) had a gentler slope in the supine position, whereas on the thigh, it showed a steeper slope. The regression line relating Fsw to Tmb had a steeper slope in the supine position than in the sitting position, suggesting that the gain in the mechanisms for central integration and rhythm-generation was enhanced in the supine position. The parameter of sweat rate divided by Fsw was lower on the forearm and the chest, whereas it was higher on the thigh in the supine position than in the sitting position, suggesting that sudomotor outflow was modified at the spinal cord in association with skin pressure. It was concluded that body posture affects sudomotor functions through both brain and spinal mechanisms.     

Maintenance of equilibrium during tracing eye movements

Horizontal tracing movements of eyes modify the type of vertical posture maintenance decreasing the role of the lower segment in the regulation of the position of the pressure center. The relationship between fluctuations of the pressure center in the frontal and sagittal planes increases. Periodicity of eye movements corresponds to fluctuations of the pressure center and these signals were phase shifted relatively to each other. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 8, pp. 152–158, August, 2004 The study was supported by the Russian Foundation for Basic Research (grant No. 01-04-49489).