上脘、中脘、下脘穴的体表定位汇考与局部解剖探析

上脘、中脘、下脘穴为任脉上的三个重要腧穴,但历代医家对其体表定位的描述并不统一.现经查阅、比较古今文献记载的三穴的体表定位并结合现代解剖学知识对腧穴深层解剖结构的研究,明确了该三穴在不同解剖层次上的组织结构及其体内投影的脏腑器官,旨在为三穴的临床应用和针刺安全应用提供依据.     

Muscle imaging: mapping responses to transcranial magnetic stimulation with high-density surface electromyography

Representations of different body parts or muscles in the human primary motor cortex overlap extensively. At the effector level, most muscles are surrounded by and overlap with several neighbours as well. This hampers the assessment of excitability in individual muscles with transcranial magnetic stimulation (TMS), even if so-called "focal" stimulating coils are used. Here we used a novel mapping paradigm based on high-density surface electromyography (HD-sEMG) to investigate the spatial selectivity of TMS in the forearm musculature. In addition, we tested the hypothesis that selective stimulation can be improved by a voluntary background contraction of the target muscle. We mapped and compared the topographies of motor evoked potential (MEP) amplitudes during rest and during background contractions of two forearm muscles (extensor carpi radialis and extensor digitorum communis). The MEP topographies were also compared to the amplitude topography of voluntary EMG. The results indicate that under many conditions a large proportion of the MEP activity recorded at the surface originated from the target muscle's neighbours. There was a systematic relationship between TMS intensity and the topographic distribution of MEP responses during voluntary contraction. With increasing stimulus intensity, the MEP topography deviated increasingly more from the topography of voluntary EMG. We conclude that when standard EMG montages are used, the recorded MEPs are not necessarily evoked in the target muscle alone. Stimulation during a voluntary background contraction of the target muscle may enhance the selectivity of TMS. It however remains essential to use stimulus intensities as low as possible, to minimize the contribution of surrounding non-target muscles to the MEP.     

Growth dynamics and morphology of regenerating optic fibers in tectum are altered by injury conditions: an in vivo imaging study in goldfish

The dynamic behavior of axons in systems that normally regenerate may provide clues for promoting regeneration in humans. When the optic nerve is severed in adult goldfish, all axons regenerate back to the tectum to reestablish accurate connections. In adult mammals, regeneration can be induced in optic and other axons but typically few fibers regrow and only for short distances. These conditions were mimicked in the adult goldfish by surgically deflecting 10-20% of optic fibers from one tectum into the opposite tectum which was denervated of all other optic fibers by removing its corresponding eye. At 21-63 days, DiI was microinjected into retina to label a few fibers and the fibers were visualized in the living fish for up to 5-7 h. The dynamic behavior and morphology of these regenerating deflected fibers were analyzed and compared to those regenerating following optic nerve crush. At 3-4 weeks, deflected fibers were found to form more branches and to maintain many more branches than crushed fibers. Although both deflected and crushed fibers exhibited stochastic growth and retraction, deflected fibers spent more time growing but grew for less distance. At 2 months, both deflected and crushed fibers became much more stable. These results show that the morphology and behavior of fibers regenerating into the same target tissue can be substantially altered by the injury conditions, that is, they show state-dependent plasticity. The morphology and behavior of the deflected fibers suggest they were impaired in their capacity to grow to their correct targets.     

Seeing voices: High-density electrical mapping and source-analysis of the multisensory mismatch negativity evoked during the McGurk illusion

Seeing a speaker's facial articulatory gestures powerfully affects speech perception, helping us overcome noisy acoustical environments. One particularly dramatic illustration of visual influences on speech perception is the "McGurk illusion", where dubbing an auditory phoneme onto video of an incongruent articulatory movement can often lead to illusory auditory percepts. This illusion is so strong that even in the absence of any real change in auditory stimulation, it activates the automatic auditory change-detection system, as indexed by the mismatch negativity (MMN) component of the auditory event-related potential (ERP). We investigated the putative left hemispheric dominance of McGurk-MMN using high-density ERPs in an oddball paradigm. Topographic mapping of the initial McGurk-MMN response showed a highly lateralized left hemisphere distribution, beginning at 175 ms. Subsequently, scalp activity was also observed over bilateral fronto-central scalp with a maximal amplitude at approximately 290 ms, suggesting later recruitment of right temporal cortices. Strong left hemisphere dominance was again observed during the last phase of the McGurk-MMN waveform (350-400 ms). Source analysis indicated bilateral sources in the temporal lobe just posterior to primary auditory cortex. While a single source in the right superior temporal gyrus (STG) accounted for the right hemisphere activity, two separate sources were required, one in the left transverse gyrus and the other in STG, to account for left hemisphere activity. These findings support the notion that visually driven multisensory illusory phonetic percepts produce an auditory-MMN cortical response and that left hemisphere temporal cortex plays a crucial role in this process.     

Neurite Outgrowth Is Directed by Schwann Cell Alignment in the Absence of Other Guidance Cues

Schwann cells enhance axonal regeneration following nerve injury in vivo and provide a favorable substrate for neurite outgrowth in vitro. However, much remains unknown about the nature of interactions that occur between Schwann cells and growing neurites. In this paper, we describe direct evidence of the ability of Schwann cell alignment alone to direct neurite outgrowth. Previously, we reported that laminin micropatterns can be used to align Schwann cells and thus create oriented Schwann cell monolayers. In the current study, dissociated rat spinal neurons were seeded onto oriented Schwann cell monolayers, whose alignment provided the only directional cue for growing neurites, and neurite alignment with the underlying Schwann cells was analyzed. The orientation of neurite outgrowth mimicked that of the Schwann cells. Associations observed between neurites and Schwann cells suggest that Schwann cells may guide neurite outgrowth through both topographical and molecular mechanisms. This work demonstrates that Schwann cell alignment can direct neurite outgrowth in the absence of other directional cues, and provides a new method for examining neuronal–Schwann cell interactions in vitro.     

Increasing the temporal g(r)ain: double-pulse resolution is affected by the size of the attention focus

Spatial cueing of transient attention has recently been shown to reduce temporal sensitivity. We investigated how the size of the sustained attentional focus influences double-pulse resolution (DPR) thresholds mapped across the visual field in a sample of 95 healthy subjects using a 9-fold interleaved adaptive algorithm (YAAP). Peripheral DPR thresholds increased for measurements between 2.5 degrees and 20 degrees eccentricity. Additionally, central DPR thresholds increased at a similar rate when measured with increasingly larger stimulus displays for peripheral measurements. This latter effect suggests that temporal resolution decreases with a larger sustained attention focus and cannot be explained by retinal characteristics only.     

Adaptive modifications of human postsaccadic pursuit eye movements induced by a step-ramp-ramp paradigm

 The main purpose of the present study was to investigate adaptive properties in human smooth-pursuit eye movements generated by a peripheral moving target. In adaptation trials, a target appeared in the peripheral visual field and immediately moved away at a constant speed, and a subject made a saccade and postsaccadic pursuit responses to track it. The target speed was, however, changed to a higher or lower constant speed (step-ramp-ramp target motion) at the termination of the saccade. This adaptation paradigm induced adaptive modifications in postsaccadic pursuit responses and our results revealed the following properties of the pursuit adaptation system. Topographic modification: Modification of the initial pursuit velocity depends on the position of a moving target. Pursuit gain change: Pursuit velocity is modified not by the addition of a constant bias to the pre-adaptation pursuit velocity, but by a change in the pursuit gain (pursuit velocity/target velocity). Lack of influence on saccade properties: Pursuit adaptation does not change the amplitude and latency of saccades either to a moving target or to a stationary target. Received: 31 May 1996 / Accepted: 28 January 1997     

Distribution of neurons related to a hindlimb as opposed to forelimb movement in the monkey premotor cortex

Summary Single cell recordings were made from the premotor cortex (lateral part of area 6) of a monkey trained to perform either a distal hindlimb or forelimb movement separately. Out of 175 movement-related neurons, 59 neurons showed modulation of activity only prior to the hindlimb movement, and the majority of them was distributed in a focal region around the superior precentral sulcus, several mm posteromedial to the genu of the arcuate sulcus. The hindlimb focus was separate from a focal region for forelimb movement-related neurons, which lay immediately posterior to the genu of the arcuate sulcus.Supported in part by Ministry of Education, Science and Culture of Japan (grant 58106001 and 58570046)