嗅球僧帽细胞具有编码气味空间信息的能力

刺激源的方位是刺激的重要特性之一.行为学的研究发现,动物能够利用气味到达左右鼻腔的时间差和强度差信息对气味方位进行感知,但作为嗅觉系统第一神经中枢的嗅球,是否具有利用两侧鼻间差信息对气味方位进行编码的能力一直受到质疑.为探讨该问题,在本研究中通过比较嗅球中84个僧帽细胞对同侧气味刺激、对侧气味刺激以及对侧气味刺激略先于同侧气味刺激时的反应,发现有29个僧帽细胞可被同侧气味所兴奋,其中18个虽然对对侧气味刺激不反应,但对侧气味的存在却能显著降低其对同侧气味刺激的反应.另外,50个僧帽细胞在只给予同侧或对侧气味刺激时不反应,但其中11个在对侧刺激略先于同侧刺激的方式给出气味时,表现出明显的兴奋性反应.我们的研究结果一方面提示僧帽细胞具有编码气味到达两个鼻腔的时间差,或气味源位置信息的能力;另一方面也表明对侧刺激不仅能对同侧嗅球僧帽细胞产生抑制效应,还可能存在目前还不明确的机制而产生兴奋效应.     

关于自动去极化电位时相定位归属的己见

任何一个可兴奋细胞兴奋的全过程都依次为：由静息电位去极化在达到阈电位之前的局部电位一锋电位（动作电位）-膜电位复极化恢复到兴奋以前的静息水平这样三个大致时相。其中阈电位之前的局部电位（local potential）是整个兴奋过程的最初阶段,是触发细胞产生真正意义兴奋（动作电位）的启动电位。虽然在不同的可兴奋细胞这个启动电位的名称不完全一样,譬如在骨骼肌细胞称之为终板电位（end—platepotential）,在感受器称之为感受器电位（或发生器电位,generator potential）,在神经称之为局部电位,但是其电位的本质意义都一样,即它们都是由外界刺激而发生、当去极化达到细胞本身的阈电位水平时,     

大鼠下丘脑薄片视上核神经元的细胞内生物电记录

从成年Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠用振动切片机制备含有视上核的下丘脑冠状薄片（５００μｍ厚）,并对视上核神经元（ｎ＝１７）进行常规细胞内生物电记录。测得静息电位－６０±８ｍＶ,膜输入电阻１７３±５８ＭΩ,时间常数１０．２±３．９ｍｓ,动作电位幅度６５±１２ｍＶ,阈电位－４４±７ｍＶ,由Ｉ─Ｖ曲线测得斜率电阻１５８±６２ＭΩ,大部分细胞还显示内向整流特性。在静息电位状态下,５７％细胞保持静息,４３％有自发锋电位发放。细胞的锋电位发放模式７８％为时相型,２２％为持续型。外源性去甲肾上腺素（ｎ＝７）或谷氨酸钠（ｎ＝５）可引起伴有膜电阻减小的去极化反应,并可导致锋电位的串发放。     

电刺激大鼠巨细胞网状核对小脑浦肯野细胞自发和诱发电活动的影响

本研究在麻醉并制动的大鼠上观察了电刺激巨细胞网状核(Gi)对小脑浦肯野细胞(PC)自发及诱发简单锋电位的影响。结果如下:(1)刺激Gi可使PC的简单锋电位出现潜伏期小于20ms的抑制性或兴奋性反应,并以抑制性反应为主。抑制性反应持续40-100ms,而兴奋性反应的时程可达200ms以上;(2)注射5-HT_2型受体阻断剂methysergide可以减弱或阻断电刺激Gi对PC自发简单锋电位的抑制作用;(3)条件性Gi刺激可以显著压抑或加强由刺激对侧大脑皮层感觉运动区引起的PC诱发简单锋电位反应。以上结果说明:在大鼠存在Gi-小脑通路,这一通路中的部分纤维是5-HT能的。Gi-小脑纤维可能通过突触和/或非经典突触的化学传递方式对PC的电活动产生某种调制性的影响。推测Gi-小脑传入纤维投射可能在某些小脑功能活动,如肌紧张及姿势的调节等方面发挥重要作用。     

NA和5—HT对小脑脑片清浦肯野细胞自发有诱发电活动的影响

在大鼠小脑脑片上观察了ＮＡ和５－ＨＴ地浦背野细胞（ＰＣ）的自发放电活动及由白质刺激所引诱发放电活动的影响。结果表明：（１）ＮＡ使ＰＣ产生抑制、兴奋和双相反应,以抑制反应为主（７９．８％）;５－ＨＴ引起ＰＣ兴奋和抑制反应,以兴奋反应略多（５７．８％）。（２）先后灌流ＮＡ和５－ＨＴ对同一个ＰＣ自发放电的影响主要为抑制（ＮＡ）－兴奋（５－ＨＴ）（５３．８％）。（３）ＮＡ地ＰＣ的诱发复杂锋电位（ＣＳ）和简     

华虻小叶神经元运动敏感性的研究

用电生理细胞内记录的方法记录了１０个以上小叶神经元对闪光、运动光斑及运动光栅刺激的电生理反应特点,结果表明：（１）小叶神经元对闪光刺激具有特征性反应,细胞对给光和撤光刺激都会表现出不同程度的去极化和超极化,反应的波形不随闪光时间的改变而改变,两次去极化之间的时间间隔与闪光刺激的时间长度成线性关系;（２）小叶神经元对运动光斑的运动速度非常敏感,而对光斑的运动方向的改变却不敏感,尽管有的细胞存在一个能使反应的变化更快的优势方向,但并没有明显的运动方向选择性;（３）小叶神经元对运动光栅的响应频率受光栅的空间频率和运动速度的双重调制,与光栅的运动方向无关。     

高频电刺激改变神经元锋电位的波形

为了正确检测和研究高频电刺激(high frequencystimulation,HFS)期间神经元的动作电位发放活动,进而深入揭示深部脑刺激治疗神经系统疾病的机制,本课题研究HFS期间锋电位波形的变化.在麻醉大鼠海马CA1区的输入神经通路Schaffer侧支上,施加1~2 min时长的100或者200 Hz顺向高频刺激(orthodromic-HFS,O-HFS),利用微电极阵列采集刺激下游神经元的多通道锋电位信号,并获得由O-HFS经过单突触传导激活的中间神经元的单元锋电位波形及其特征参数.结果表明,O-HFS使得锋电位的幅值明显减小而半高宽明显增加,以基线记录为基准计算百分比值,O-HFS期间锋电位的降支幅值和升支幅值分别可减小20%和40%左右,半高宽则增加10%以上.并且,在大量神经元同时产生动作电位期间,或者在比200 Hz具有更大兴奋作用的100 Hz刺激期间,锋电位波形的改变更多,幅值的减小可达50%,宽度的增加可达20%.可以推测,高频电刺激对于神经元的兴奋作用可能升高细胞膜电位,从而改变细胞膜离子通道的活动特性,导致动作电位波形的改变.这些结果支持深部脑刺激具有兴奋性调节作用的假说,对于正确分析高频电刺激期间神经元锋电位活动具有指导意义,也为进一步研究深部脑刺激(DBS)治疗脑神经系统疾病的机制提供了重要线索.     

激活蓝斑在孤束核水平对迷走神经传入的抑制

在戊巴比妥钠麻醉兔,电刺激颈迷走神经中枢端,在同侧孤束核（NTS）区可记录到一个由三个子波组成的复合电位。它们的潜伏期分别为6．8±0．6ms（P1）,25．8±4．2ms（P2）和89．1±2．7ms（P3）。这可能代表着不同性质的迷走传入纤维的突触后电位。同侧蓝斑（LC）内微量注射谷氨酸钠使P2,P3波的幅值明显降低。电刺激LC在同侧NTS区诱发出111个有反应单位,其潜伏期平均为6．3±1．4ms。在169个对迷走传入刺激有反应的NTS单位中,有90个对LC刺激也有反应。39个（占43．3％）会聚性单位对上述两种刺激的反应相似,而其余的呈不同的反应。对LC和迷走刺激分别均呈兴奋反应的25个NTS单位中,如预先刺激LC,则有14个单位对迷走刺激的兴奋反应受到明显抑制,另11个单位的兴奋反应完全被抑制。上述结果提示：激活蓝斑核具有抑制NTS对迷走传入刺激反应的作用。     

迷走神经感觉输入诱发的鲫鱼Mauthner细胞胞内电位变化

实验运用微电极穿刺技术,初步探索了刺激鲫鱼右侧迷走神经在双侧Mauthner(M)细胞胞体诱发的胞内电位变化。结果表明：（1）直接刺激鲫鱼右侧迷走神经,可在同侧或对侧M细胞胞体记录到一种短潜伏期、长持续时间、分级的、复合的突触后电位（postsynaptic potentials,PSPs)。此PSPs表现出明显的强度依从性和频率依赖性。（2）刺激迷走神经诱发的PSPs可使逆向锋电位的幅度降低。（3）肌注士的宁后,PSPs的幅度增高、平均持续时间增加、峰值前移。并且可爆发两个以上的动作电位,上述结果提示：迷走神经到M细胞的通路可能 是由长短不等的神经链群组成的。且此通路中不仅包含有兴奋性成分还包含有抑制性成分,而兴奋和抑制之间的相互关系可能起着调节M细胞兴奋性的作用。     

蝇髓部细胞的运动敏感性

用细胞外记录方法研究了蝇髓部细胞的运动敏感性.实验证明,在蝇髓部有运动敏感型细胞,它们的主要特点是对运动敏感,但不具有方向选择性.其主要性质如下:1.有些细胞对闪光刺激给出超极化反应,有些则为去极化反应;2.对运动反应,但不具有方向性;3.有些对大视场的运动敏感,有些则对小视场的运动敏感;4.反应幅度与图形运动速度有关;5.感受野为简单型,并且不很大.对于可能对应的算法进行了讨论.     

Visual processing of moving single objects and wide-field patterns in flies: Behavioural analysis after laser-surgical removal of interneurons

A laser micro-beam unit was used to reproducibly and selectively eliminate the large horizontal and vertical motion sensitive neurons (H- and V-cells) of the lobula plate on one side of the brain of house fliesMusca domestica. This was achieved by ablating the precursors of these cells deep in the larval brain without damaging other cells in the brain or other tissues. The individually reared flies were tested for their behaviour. Three tests were performed: (i) visual fixation of a single stripe, (ii) the optomotor turning and thrust response to a stripe moving clockwise and counterclockwise around the fly, (iii) the monocular turning response to a moving grating. The responses to a moving single object were normal on both sides, the control side and the one lacking the H- and V-cells. However, the responses to a moving grating were reduced on the side lacking H- and V-cells for progressive (front to back) and regressive (back to front) motion. From this we conclude that the response to single objects is controlled mainly by cells other than the H- and V-cells. We also suggest two separate pathways for the processing of single object motion and wide field pattern motion respectively (Fig. 8). Furthermore, the H- and V-cells might function as visual stabilizers and background motion processors.     

Motion sensitive interneurons in the optomotor system of the fly

The three horizontal cells of the lobula plate of the blowflyCalliphora erythrocephala were studied anatomically and physiologically by means of cobalt impregnations and intracellular recordings combined with Procion and Lucifer Yellow injections. The cells are termed north, equatorial and south horizontal cell (HSN, HSE, HSS) and are major output neurons of the optic lobe. 1. The dendritic arborizations of the HSN, HSE, HSS reside in a thin anterior layer of the lobula plate and extend over the dorsal, equatorial and ventral parts of this neuropil, respectively. Due to the retinotopic organization of the optic lobe, these parts correspond anatomically to respective regions of the ipsilateral visual field. Homologue horizontal cells in both lobula plates of the same animal and in different animals are highly variable with respect to their individual dendritic branching patterns. They are extraordinarily constant, on the other hand, with regard to the position and size of their dendritic fields as well as their dendritic branching density distributions. Each cell covers about 40% of the total area of the lobula plate and shows the highest dendritic density near the lateral margin of the neuropil which subserves the frontal eye region. The axons of the horizontal cells are relatively short and large in diameter; they terminate in the posterior ventrolateral protocerebrum. 2. The horizontal cells are directionally selective motion sensitive visual interneurons responding preferentially to progressive (front to back) motion in the ipsilateral visual field with graded depolarization of their axons and superimposed action potentials. Stimulation with motion in the reverse direction leads to hyperpolarizing graded responses. The HSE and HSN are additionally activated by regressive motion in the contralateral visual field.     

Wide-field motion-sensitive neurons tuned to horizontal movement in the honeybee,Apis mellifera

This paper describes the morphology and response characteristics of two types of paired descending neurons (DNs) (classified as DNVII₁ and DNIV₁) and two lobula neurons (HR1 and HP1) in the honeybee, Apis mellifera.

The horizontal cells in the lobula plate of the blowfly,Phaenicia sericata

SummarySummary Combining intracellular recording and dye injection techniques, the horizontal cells of the blowfly,Phaenicia (= Lucilia) sericata, were studied.Anatomy In each lobula plate, one finds a set of three cells, termed NH-, EH- and SH-cell. EH occurs in two distinct anatomical forms, EH1 and EH2, differing in their respective branching patterns of the axon at the frontal surface of the lobula plate. Each cell's dendrite covers approximately a third of the surface of the lobula plate corresponding to a third of the visual field of the ipsilateral eye. These dendrites possess postsynaptic spines. The axons of all three cells pass along the frontal surface of the lobula plate within the inner chiasma; they cross the optic peduncle and enter the central protocerebrum where they form a second arborization, the axonal arborization consisting of dorsally extending collaterals. The axons terminate in the posterior slope of the ventrolateral protocerebrum. The axonal arborization as well as the axonal terminals possess telodendritic knobs. Ultrastructural investigations show that the lobula plate-dendrite possesses exclusively postsynaptic chemical synapses, and that the axonal arborisation and the axonal terminals possess pre- as well as postsynaptic chemical synapses. The very endings of the axons are exclusively presynaptic.Physiology The horizontal cells respond to stimulation within the ipsi- and/or contralateral receptive field. Regressive motion within the contralateral receptive field induces EPSPs and action potentials of small amplitude (10–35 mV); progressive motion is ineffective. Within the ipsilateral receptive field, regressive motion hyperpolarizes the cell membrane whereas progressive motion induces a strong depolarizing membrane potential-shift with superimposed fast potential changes of noisy appearance. Thus, the horizontal cells respond to rotational movement of the surround around the high axis of the animal: clockwise rotation excites the horizontal cells of the right lobula plate and counterclockwise motion those of the left lobula plate, respectively. However, this compound potential behaviour can only be recorded in the lobula plate-axon and main dendrites, whereas the horizontal cells respond tocontralateral regressive motion with action potentialsonly in their axonal terminals in the posterior slope; no graded potentials can be recorded in this cell region if stimulation occurs within theipsilateral receptive field. It is discussed that the previously described graded potentials for the axonal terminals (Hausen 1976b) can only be measured if the cells are already damaged. The probable cause of this change in response behaviour from action potentials to a compound potential behaviour (consisting of graded potentials and action potentials though of small amplitude) is discussed.This research was supported by the Deutsche Forschungsgemeinschaft through grants Ec56/1a + b and a Heisenberg stipend EC 56/3, funds from the SFB 114, and a grant from the National Science Foundation (NSF BMS 74-21712) awarded to the author and L.G. Bishop. I am indebted to Dr. A. Whittle and particularly to Prof. K. Meller for their invaluable help in ultrathin sectioning and to Mrs. B. Decker who introduced me to the technique of cutting serial semithin sections. Prof. K. Hamdorf helped with many stimulating discussions. I am most grateful to Dr. W. Broughton for kindly correcting the English style.     

Motion sensitive interneurons in the optomotor system of the fly

The functional properties of the three horizontal cells (north horizontal cell, HSN; equatorial horizontal cell, HSE; south horizontal cell, HSS) in the lobula plate of the blowflyCalliphora erythrocephala were investigated electrophysiologically. 1. The receptive fields of the HSN, HSE, and HSS cover the dorsal, equatorial and ventral part of the ipsilateral visual field, respectively. In all three cells, the sensitivity to visual stimulation is highest in the frontal visual field and decreases laterally. The receptive fields and spatial sensitivity distributions of the horizontal cells are directly determined by the position and extension of their dendritic fields in the lobula plate and the dendritic density distributions within these fields. 2. The horizontal cells respond mainly to progressive (front to back) motion and are inhibited by motion in the reverse direction, the preferred and null direction being antiparallel. The amplitudes of motion induced excitatory and inhibitory responses decline like a cosine function with increasing deviation of the direction of motion from the preferred direction. Stimulation with motion in directions perpendicular to the preferred direction is ineffective. 3. The preferred directions of the horizontal cells show characteristic gradual orientation changes in different parts of the receptive fields: they are horizontally oriented only in the equatorial region and increasingly tilted vertically towards the dorsofrontal and ventrofrontal margins of the visual field. These orientation changes can be correlated with equivalent changes in the local orientation of the lattice of ommatidial axes in the pertinent compound eye. 4. The response amplitudes of the horizontal cells under stimulation with a moving periodic grating depend strongly on the contrast frequency of the stimulus. Maximal responses were found at contrast frequencies of 2–5 Hz. 5. The spatial integration properties of the horizontal cells (studied in the HSE) are highly nonlinear. Under stimulation with extended moving patterns, their response amplitudes are nearly independent of the size of the stimuli. It is demonstrated that this response behaviour does not result from postsynaptic saturation in the dendrites of the cells. The results indicate that the horizontal system is essentially involved in the neural control of optomotor torque responses performed by the fly in order to minimize unvoluntary deviations from a straight flight course.     

Is there a motion-independent position computation of an object in the visual system of the housefly?

A single vertical stripe (long or short) was moved clockwise, with constant speed, around a tethered femaleMusca domestica fly. The yaw torque response of the fly was analyzed as a function of the position of the object. After an interval of 8 s the stripe was moved counterclockwise and a similar analysis of the torque was made. This procedure was repeated a few times and averaged to each direction separately and for all the flies tested. The results suggested that: a) There are at least two mechanisms for computing the optomotor response in the lower part of the fly's eye, one performing a position-dependent velocity computation and the other depending on the position but not on the direction of motion of an object. b) These two components are parametrized over the position on the lower part of the eye. The results also show that: c) There is a significant difference in the response between the upper and the lower part of the eye. The position-dependent component cannot be detected in the upper part of the eye. In addition: d) Two different control mechanisms are proposed, one responding to progressive (from front to back) and one to regressive (from back to front) movement of objects.     

On the neuronal basis of figure-ground discrimination by relative motion in the visual system of the fly

It has been concluded in the preceding papers (Egelhaaf, 1985a, b) that two functional classes of output elements of the visual ganglia might be involved in figure-ground discrimination by relative motion in the fly: The Horizontal Cells which respond best to the motion of large textured patterns and the FD-cells which are most sensitive to small moving objects. In this paper it is studied by computer simulations (1) in what way the input circuitry of the FD-cells might be organized and (2) the role the FD-cells play in figure-ground discrimination. The characteristic functional properties of the FD-cells can be explained by various alternative model networks. In all models the main input to the FD-cells is formed by two retinotopic arrays of small-field elementary movement detectors, responding to either front-to-back or back-to-front motion. According to their preferred direction of motion the FD-cells are excited by one of these movement detector classes and inhibited by the other. The synaptic transmission between the movement detectors and the FD-cells is assumed to be non-linear. It is a common property of all these model circuits that the inhibition of the FD-cells induced by large-field motion is mediated by pool cells which cover altogether the entire horizontal extent of the visual field of both eyes. These pool cells affect the response of the FD-cells either by pre- or postsynaptic shunting inhibition. Depending on the FD-cell under consideration, the pool cells are directionally selective for motion or sensitive to motion in either horizontal direction. The role the FD-cells and the Horizontal Cells are likely to play in figure-ground discrimination can be demonstrated by computer simulations of a composite neuronal model consisting of the model circuits for these cell types. According to their divergent spatial integration properties they perform different tasks in figure-ground discrimination: Whereas the Horizontal Cells mainly mediate information on wide-field motion, the FD-cells are selectively tuned to efficient detection of relatively small targets. Both cell classes together appear to be sufficient to account for figure-ground discrimination as it has been shown by analysis at the behavioural level.     

The centrifugal horizontal cells in the lobula plate of the blowfly, Phaenicia sericata

Intracellular recordings combined with iontophoretic injection of Procion Yellow M4RAN were used to study the anatomy and physiology of the centrifugal horizontal cells (CH-cells) in the lobula plate of the blowfly, Phaenicia sericata.Anatomy: The CH-cells comprise a set of two homolateral, giant visual interneurones (DCH, VCH) at the rostral surface of each lobula plate. Their extensive arborizations in the lobula plate possess bulbous swellings (boutons terminaux). The arborization of one cell (DCH) covers the dorsal, and the arborization of the other cell (VCH) the ventral half of the lobula plate. Their axons run jointly with those of the horizontal cells through the chiasma internum and the optic peduncle. Their protocerebral arborization possesses spines; they form a dense network together with the axonal arborization of the horizontal cells, a second type of giant homolateral cell most sensitive to horizontal motion. The protocerebral arborization of the CH-cells gives rise to a cell body fibre which traverses the protocerebrum dorsally to the oesophageal canal. The cell body lies on the contralateral side laterally and slightly dorsally to the oesophageal canal in the frontal cell body layer.Physiology: The CH-cells respond with graded potentials to rotatory movements of their surround. Cells in the right lobula plate respond with excitation (excitatory postsynaptic potentials, membrane depolarization) to clockwise motion (contralateral regressive, ipsilateral progressive), and with inhibition (inhibitory postsynaptic potentials, membrane hyperpolarization) to counterclockwise motion in either or both receptive fields; CH-cells respond to motion presented to the ipsilateral and/or contralateral eye. Cells of the left lobula plate respond correspondingly to the reverse directions of motion. Vertical pattern motion and stationary patterns are ineffective.The heterolateral H1-neurone elicits excitatory postsynaptic potentials in the DCH-cell; these postsynaptic potentials are tightly correlated 1:1 to the preceding H1-action potentíal. The delay between the peak of the action potential and the beginning of the DCH-postsynaptic potential is 1.15 msec, agreeing very well with the value reported previously for the blowfly, Calliphora (Hausen, 1976a). The synaptic input and output connections of the CH-cells are discussed.     

The interaction between visual edge fixation and skototaxis in the mealworm beetle Tenebrio molitor

Summary (1) It has been shown in earlier experiments that during the visually guided orientation response of the mealworm beetle,Tenebrio molitor, edge fixation and skototaxis interact. Under certain stimulus conditions these two effects act against each other and relative movement between the retina and the surroundings shifts the balance in favour of edge fixation. In this paper, three further parameters are described which change the contribution of the two mechanisms to the turning tendency of the animals. (2) When the centre of a broad black stripe lies on one side and one of the edges on the other side of the animal (Fig. 1B, C) then motion of an edge from front to back (progressive movement) more effectively increases the relative weight of edge fixation than do regressive movements (motion of an edge from back to front). (3) In the same situation temporal modulation of the overall illumination weakens skototaxis, dimming more than brightening (Fig. 2 A). From this it was predicted — and confirmed — that the dependence on the direction of motion will be reversed if both the centre and the edge closest to the midline of a broad black stripe lie on the same side of the animal (Fig. 2 B). (4) Animals with one eye blinded can fixate an edge (Fig. 3). Furthermore, edge fixation is mediated mainly by the ventral part of the eyes and skototaxis by the dorsal (Fig. 5). (5) The possible significance of the results for the animal's natural behaviour and for the underlying neural circuitry is discussed.     

Orientation tuning of motion-sensitive neurons shaped by vertical-horizontal network interactions

We measured the orientation tuning of two neurons of the fly lobula plate (H1 and H2 cells) sensitive to horizontal image motion. Our results show that H1 and H2 cells are sensitive to vertical motion, too. Their response depended on the position of the vertically moving stimuli within their receptive field. Stimulation within the frontal receptive field produced an asymmetric response: upward motion left the H1/H2 spike frequency nearly unaltered while downward motion increased the spike frequency to about 40% of their maximum responses to horizontal motion. In the lateral parts of their receptive fields, no such asymmetry in the responses to vertical image motion was found. Since downward motion is known to be the preferred direction of neurons of the vertical system in the lobula plate, we analyzed possible interactions between vertical system cells and H1 and H2 cells. Depolarizing current injection into the most frontal vertical system cell (VS1) led to an increased spike frequency, hyperpolarizing current injection to a decreased spike frequency in both H1 and H2 cells. Apart from VS1, no other vertical system cell (VS2-8) had any detectable influence on either H1 or H2 cells. The connectivity of VS1 and H1/H2 is also shown to influence the response properties of both centrifugal horizontal cells in the contralateral lobula plate, which are known to be postsynaptic to the H1 and H2 cells. The vCH cell receives additional input from the contralateral VS2-3 cells via the spiking interneuron V1.