Midline Section Research Articles

Optimization Design of the Elbow Inlet Channel of a Pipeline Pump Based on the SCSO-BP Neural Network

A vertical pipeline pump is a type of single-stage, single-suction centrifugal pump with a curved elbow input. The inhomogeneous flow of the impeller inlet coexists with the unique elbow inlet channel, making it simple to generate the inlet vortical secondary flow. This paper aimed to optimize elbow inlet channel performance using a backpropagation (BP) neural network enhanced by the Sand Cat Swarm algorithm. The elbow flow channel’s midline and cross section shapes were fitted with a spline curve, and the parametric model of the curve was then constructed. Nine initial variables were filtered down to four optimization variables using the partial factor two-level (P2) and Plackett-Burman (P-B) experimental designs and multivariate analysis of variance. The sample space was generated by 50 groups of experiment samples, and the Sand Cat Swarm algorithm to optimize the BP (SCSO-BP) neural network and the approximation model of four variables were built. A genetic algorithm (GA) was applied to determine the optimal parameters among the approximate models in the sample space, and the ideal parameter combination of the elbow inlet channel was achieved. The findings demonstrated a strong agreement between the experimental and numerical simulation results. With reduced error fluctuation in inaccuracy and a more consistent fluctuation range, the approximate prediction model based on the optimized Sand Cat Swarm algorithm performed better. The optimized inlet model minimized the impact loss on the inlet wall, improved the velocity distribution uniformity of the inlet impeller, increased the pump efficiency by about 5% and the head by about 7.48% near the design flow, and broadened the efficient region of the pump.

Brainstem Neural Circuits Triggering Vertical Saccades and Fixation.

Neurons in the nucleus raphe interpositus have tonic activity that suppresses saccadic burst neurons (BNs) during eye fixations, and that is inhibited before and during saccades in all directions (omnipause neurons, OPNs). We have previously demonstrated via intracellular recording and anatomical staining in anesthetized cats of both sexes that OPNs are inhibited by BNs in the medullary reticular formation (horizontal inhibitory BNs, IBNs). These horizontal IBNs receive monosynaptic input from the caudal horizontal saccade area of the superior colliculus (SC), and then produce monosynaptic inhibition in OPNs, providing a mechanism to trigger saccades. However, it is well known that the neural circuits driving horizontal components of saccades are independent from the circuits driving vertical components. Thus, our previous results are unable to explain how purely vertical saccades are triggered. Here, we again apply intracellular recording to show that a disynaptic vertical IBN circuit exists, analogous to the horizontal circuit. Specifically, we show that stimulation of the SC rostral vertical saccade area produces disynaptic inhibition in OPNs, which is not abolished by midline section between the horizontal IBNs. This excludes the possibility that horizontal IBNs could be responsible for the OPN inhibition during vertical saccades. We then show that vertical IBNs in the interstitial nucleus of Cajal, which receive monosynaptic input from rostral SC, are responsible for the disynaptic inhibition of OPNs. These results indicate that a similarly functioning SC-IBN-OPN circuit exists for both the horizontal and vertical oculomotor pathways. These two IBN-mediated circuits are capable of triggering saccades in any direction.Significance Statement Saccades shift gaze to objects of interest, moving their image to the central retina, where it is maintained for detailed examination (fixation). During fixation, high gain saccade burst neurons (BNs) are tonically inhibited by omnipause neurons (OPNs). Our previous study showed that medullary horizontal inhibitory BNs (IBNs) activated from the caudal superior colliculus (SC) inhibit tonically active OPNs in order to initiate horizontal saccades. The present study addresses the source of OPN inhibition for vertical saccades. We find that OPNs monosynaptically inhibit vertical IBNs in the interstitial nucleus of Cajal during fixation. Those same vertical IBNs are activated by the rostral SC, and inhibit OPN activity to initiate vertical saccades.

Leonardo da Vinci, the Ventricles of the Brain, and the Foramen of Monro

Abstract Leonardo da Vinci’s neuroanatomical studies include a cast of the ventricles of an ox with melted wax. By depicting the result of this ingenious approach, he provided the first graphic representation of the connection between the cerebral ventricles. We question the widespread assumption that Leonardo already showed the fully paired lateral ventricles and the interventricular foramina today named after Alexander Monro. Instead, we demonstrate by graphical means and magnetic resonance imaging that this is in fact a longstanding misinterpretation of an unusual section plane and its depiction used by Leonardo. Such a midline section fails to show two lateral ventricles and their interventricular foramina both in human and ruminant brains. Our results correct numerous inaccurate statements made in the literature since 1930. With regard to Leonardo’s rendering of the ventricular system, we discuss the realism of his anatomical drawings, the visual techniques he employed, and the legitimation of our approach.

Morphological and molecular characterization of Calicophoron raja (Näsmark, 1937) collected from wild Bovidae in South Africa

Paramphistomes, commonly known as rumen flukes, are digenean parasites that infect ruminants. Accurate morphological identification of paramphistome species is challenging and often neglected. For instance, it requires sagittal midline sections of adult flukes, which are difficult to prepare. Therefore, the majority of the genetic information on paramphistomes found in the International Nucleotide Sequence Database is not supported by morphological descriptions, and the DNA barcodes of paramphistome species remain unreliable. In the present study, both morphological and molecular characterizations were simultaneously performed to ensure the reliability of the DNA information for the paramphistome species Calichophoron raja (Näsmark, 1937). The morphological characteristics of the sagittal and horizontal sections of adult flukes from a black wildebeest (Connochaetes gnou) and a waterbuck (Kobus ellipsiprymnus) in South Africa were identical to those previously described for Ca. raja. Additionally, this study represents a new host record of the species from Co. gnou. All sequences of the internal transcribed spacer 2 region of ribosomal DNA were 100% identical among the 18 flukes analyzed in the present study. A single nucleotide mutation was observed between Ca. raja in this study and Ca. raja detected in domestic ruminants in Kenya.

Brainstem Circuits Triggering Saccades and Fixation.

Omnipause neurons (OPNs) in the nucleus raphe interpositus have tonic activity while the eyes are stationary ("fixation") but stop firing immediately before and during saccades. To locate the source of suppression, we analyzed synaptic inputs from the rostral and caudal superior colliculi (SCs) to OPNs by using intracellular recording and staining, and investigated pathways transmitting the inputs in anesthetized cats of both sexes. Electrophysiologically or morphologically identified OPNs received monosynaptic excitation from the rostral SCs with contralateral dominance, and received disynaptic inhibition from the caudal SCs with ipsilateral dominance. Cutting the tectoreticular tract transversely between the contralateral OPN and inhibitory burst neuron (IBN) regions eliminated inhibition from the caudal SCs, but not excitation from the rostral SCs in OPNs. In contrast, a midline section between IBN regions eliminated disynaptic inhibition in OPNs from the caudal SCs but did not affect the monosynaptic excitation from the rostral SCs. Stimulation of the contralateral IBN region evoked monosynaptic inhibition in OPNs, which was facilitated by preconditioning SC stimulation. Three-dimensional reconstruction of HRP-stained cells revealed that individual OPNs have axons that terminate in the opposite IBN area, while individual IBNs have axon collaterals to the opposite OPN area. These results show that there are differences in the neural circuit from the rostral and caudal SCs to the brainstem premotor circuitry and that IBNs suppress OPNs immediately before and during saccades. Thus, the IBNs, which are activated by caudal SC saccade neurons, shut down OPN firing and help to trigger saccades and suppress ("latch") OPN activity during saccades.SIGNIFICANCE STATEMENT Saccades are the fastest eye movements to redirect gaze to an object of interest and bring its image on the fovea for fixation. Burst neurons (BNs) and omnipause neurons (OPNs) which behave reciprocally in the brainstem, are important for saccade generation and fixation. This study investigated unsolved important questions about where these neurons receive command signals and how they interact for initiating saccades from visual fixation. The results show that the rostral superior colliculi (SCs) excite OPNs monosynaptically for fixation, whereas the caudal SCs monosynaptically excite inhibitory BNs, which then directly inhibit OPNs for the initiation of saccades. This inhibition from the caudal SCs may account for the omnipause behavior of OPNs for initiation and maintenance of saccades in all directions.

Induction of selective liver hypothermia prevents significant ischemia/reperfusion injury in Wistar rats after 24 hours

PurposeTo investigate the effects of induction of selective liver hypothermia in a rodent model.MethodsSeven male Wistar rats were subjected to 90 minutes of partial 70% liver ischemia and topic liver 26°C hypothermia (H group). Other seven male Wistar rats were subjected to 90 minutes of partial 70% normothermic liver ischemia (N group). Five additional rats underwent a midline incision and section of liver ligaments under normothermic conditions and without any liver ischemia (sham group). All animals were sacrificed 24-h after reperfusion, and livers were sampled for analyses. Pathology sections were scored for sinusoidal congestion, ballooning, hepatocelllular necrosis and the presence of neutrophilic infiltrates.ResultsAt the end of the experiment, liver tissue expressions of TNF-ɑ, IL-1β, iNOS and TNF-ɑ/IL-10 ratio were significantly reduced in the H group compared to N group, whereas IL-10 and eNOS were significantly increased in H group. Histopathological injury scores revealed a significant decrease in ischemia/reperfusion (I/R) injuries in H group.ConclusionSelective liver hypothermia prevented I/R injury by inhibiting the release of inflammatory cytokines, preserves microcirculation, prevents hepatocellular necrosis and leukocyte infiltration, allowing maintenance of the liver architecture.

Numerical Investigation of Influence of Diverse Winglet Configuration on Induced Drag

In this study, numerical calculations were conducted over 3D wing surface with varying winglet configuration and their modifications to understand effect of wingtip device on induced drag formation. NACA0012 airfoil was used for all configurations due to availability of experimental lift and drag data. Lift, drag and pressure coefficient were calculated with SST turbulence model at the Reynolds numbers of 6 × 106 and were compared with experimental data to validate the simulation accuracy of numerical approaches. The winglet with different relative angle with wing surface was designed, and numerical calculation was performed with commercial software COMSOL. The winglets attached to the wingtip were divided into 3 different categories such as single winglet up or down sloping, split winglet up and down sloping. To see normal wingtip vortex, conventional wingtip was simulated together with winglet in all cases. Pressure coefficient for the midline section of the wing is in a good agreement with the experimental data, but pressure coefficient at the tip section is very different. Maximum size of vortices was observed for the case of winglet 45° up sloping with the surface, but with the increasing winglet angle with the surface, size of vortex decreases. Results indicate that wingtip vortex formation was reduced considerably at the angle of attack relative to wing surface starting from 90° and considering only lift and pressure coefficients, up-sloping winglet can be considered to be more efficient than down sloped one and maximum efficiency increased between 4 and 6%.

In vivo measures of mammary development in gestating gilts.

Potential links between measures of udder morphology obtained in live pregnant gilts and mammary gland development and composition measured in mammary tissue collected at slaughter were studied. Thirty-three gilts were used. In vivo measures of gland morphology using a tape or ultrasound imaging (parenchymal area measured by ultrasound [AREA]) were obtained on d 108 ± 1 of gestation. Gilts were then slaughtered on d 110 ± 1 of gestation to collect mammary glands for dissection and compositional analyses. The various tape measures were the distance between each teat on one side of the udder (DIST-TEAT), the distance between each teat pair (DIST-PAIR), the length of the udder (sum of all DIST-TEAT), the distance between the base of the teat and the ventral midline section of the udder (MID), and the distance between the base of the teat and the exterior junction of the udder with the abdomen (EXT). The variables MID, DIST-TEAT, DIST-PAIR, and length had very poor correlations with parenchymal weight, extraparenchymal weight, or any of the measured compositional variables. On the other hand, both AREA and EXT were correlated ( < 0.01) with the weight of parenchymal tissue, total parenchymal protein, total DNA, and total RNA. The ultrasound measure AREA and the tape measure EXT were also correlated with each other ( < 0.05). These measures could, therefore, be helpful to estimate mammary development in studies where animals cannot be slaughtered. The tape measure EXT seemed to better reflect the volume of the gland than MID, and it provided as reliable an estimate of parenchymal weight as the measure of parenchymal area using ultrasound while being much easier and cheaper to obtain.

Intraductal injection as an effective drug delivery route in the management of salivary gland diseases.

While conservative approaches for chronic sialoadenitis are in current use, the utility of intraductal injection therapy remains unclear. The purpose of this study is to provide evidence that substances delivered through intraductal injection of the salivary gland are able to be effectively distributed throughout the gland. Methylene blue dye (0.1%) was injected intraductally into a porcine parotid gland (5ml) of one group and the porcine submandibular gland (1 or 2ml, n=6 for each preparation) of another group. After the injection, the ductal systems were evaluated, sectioned, and observed microscopically. Color area analysis was performed on submandibular gland sections, and the infiltration ratio of the dye was calculated. The papillae of both Stensen's and Wharton's duct openings were easily identified with intraductally delivered methylene blue dye. The dye infiltration began from the central ductal region of the gland and could be easily observed to gradually disperse to the peripheral regions in each acinar. There were no statistically significant differences in infiltration ratios between anterior, midline, and posterior section of the submandibular gland. Also, there were no statistically significant differences in the ratios between 1 and 2ml injections at all the three section positions. This study demonstrated that desired substances can be evenly delivered throughout the salivary gland through intraductal injections. The use of intraductal injections might serve as a potential therapeutic procedure in the management of salivary gland diseases.

Midline section of the medulla abolishes inspiratory activity and desynchronizes pre-inspiratory neuron rhythm on both sides of the medulla in newborn rats.

Each half of the medulla contains respiratory neurons that constitute two generators that control respiratory rhythm. One generator consists of the inspiratory neurons in the pre-Bötzinger complex (preBötC); the other, the pre-inspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG), rostral to the preBötC. We investigated the contribution of the commissural fibers, connecting the respiratory rhythm generators located on the opposite side of the medulla to the generation of respiratory activity in brain stem-spinal cord preparation from 0- to 1-day-old rats. Pre-I neuron activity and the facial nerve and/or first lumbar (L1) root activity were recorded as indicators of the pFRG-driven rhythm. Fourth cervical ventral root (C4) root and/or hypoglossal (XII) nerve activity were recorded as indicators of preBötC-driven inspiratory activity. We found that a midline section that interrupted crossed fibers rostral to the obex irreversibly eliminated C4 and XII root activity, whereas the Pre-I neurons, facial nerve, and L1 roots remained rhythmically active. The facial and contralateral L1 nerve activities were synchronous, whereas right and left facial (and right and left L1) nerves lost synchrony. Optical recordings demonstrated that pFRG-driven burst activity was preserved after a midline section, whereas the preBötC neurons were no longer rhythmic. We conclude that in newborn rats, crossed excitatory interactions (via commissural fibers) are necessary for the generation of inspiratory bursts but not for the generation of rhythmic Pre-I neuron activity.

Comparisons of the morbidity outcomes in repeated cesarean sections using midline and Pfannenstiel incisions

The aim of this study was to evaluate operative complications, operative time, postpartum complications and neonatal outcome in repeated cesarean section between previous low midline and previous Pfannenstiel cesarean section. This was a prospective comparative study conducted at the King Chulalongkorn Memorial Hospital in pregnant women with indication of repeated cesarean section for either low midline or Pfannenstiel incisions. A total of 320 pregnant women with previous cesarean section were enrolled into two groups: low midline (n = 160) and Pfannenstiel (n = 160) groups. Operative complications, postpartum complications and neonatal outcomes were not statistically different between the groups (P > 0.05). Median times for total operative time (50 vs 50 min, P = 0.833), time from skin incision to the uterus (4 vs 4 min, P = 0.877), and time from uterine incision to fetal delivery (3 vs 2 min, P = 0.871) were comparable between the groups. Operative complications, operative time, postpartum complications and neonatal outcomes were comparable between low midline and Pfannenstiel groups in repeated cesarean sections irrespective of the previous technique used.

Maternal corticosterone regulates nutrient allocation to fetal growth in mice

Stresses during pregnancy that increase maternal glucocorticoids reduce birth weight in several species. However, the role of natural glucocorticoids in the mother in fetal acquisition of nutrients for growth remains unknown. This study aimed to determine whether fetal growth was reduced as a consequence of altered amino acid supply when mice were given corticosterone in their drinking water for 5 day periods in mid to late pregnancy (day, D, 11-16 or D14-19). Compared to controls drinking tap water, fetal weight was always reduced by corticosterone. At D16, corticosterone had no effect on materno-fetal transfer of [(14)C]methylaminoisobutyric acid (MeAIB), although placental MeAIB accumulation and expression of the Slc38a1 and Slc38a2 transporters were increased. However, at D19, 3 days after treatment ended, materno-fetal transfer of MeAIB was increased by 37% (P < 0.04). During treatment at D19, placental accumulation and materno-fetal transfer of MeAIB were reduced by 40% (P < 0.01), although expression of Slc38a1 was again elevated. Permanent reductions in placental vascularity occurred during the earlier but not the later period of treatment. Placental Hsd11b2 expression, which regulates feto-placental glucocorticoid bioavailability, was also affected by treatment at D19 only. Maternal corticosterone concentrations inversely correlated with materno-fetal MeAIB clearance and fetal weight at D19 but not D16. On D19, weight gain of the maternal carcass was normal during corticosterone treatment but reduced in those mice treated from D11 to D16, in which corticosterone levels were lowest. Maternal corticosterone is, therefore, a physiological regulator of the amino acid supply for fetal growth via actions on placental phenotype.

The hemisegmental locomotor network revisited

The organization of the minimal neuronal substrate capable of generating locomotor rhythmicity in vertebrates is investigated in several species, with an emphasis on identifying evolutionary-conserved features. In lamprey, an eel-like lower vertebrate that swims by undulatory movements of the body, the network has been identified as a recurrent network of excitatory interneurons localized in each spinal hemisegment. This conclusion rested upon the observation that each side of the spinal cord is able to express rhythmic locomotor-related bursting after being surgically separated along the midline, even in the absence of inhibition. An important caveat, however, is that this rhythmicity must be an intrinsic capability of the hemisegmental networks and not a newly acquired property as a result of a plastic remodeling of the network occurring after the lesion. Here we examine this issue by recording the motor output expressed by the electrically activated hemicord in the first minutes after hemisection. We observed clear rhythmic bursting in the frequency range previously linked to the operation of the central pattern generator for swimming. Moreover, we recorded the output of the unilateral networks in the intact spinal cord (i.e. no midline section performed) by activating them with asymmetrical stimulation. We thus conclude that the lamprey hemicord does possess the intrinsic capability of generating the basic rhythmic drive of locomotion. The wider significance of these data stems from the lamprey being a model of axial locomotion, and from the many lesion studies previously performed in other animals.

Histological and MS spectrometric analyses of the modified tissue of bulgy form tadpoles induced by salamander predation

SummaryThe rapid induction of a defensive morphology by a prey species in face of a predation risk is an intriguing in ecological context; however, the physiological mechanisms that underlie this phenotypic plasticity remain uncertain. Here we investigated the phenotypic changes shown by Rana pirica tadpoles in response to a predation threat by larvae of the salamander Hynobius retardatus. One such response is the bulgy morph phenotype, a relatively rapid swelling in size by the tadpoles that begins within 4 days and reaches a maximum at 8 to 10 days. We found that although the total volume of bodily fluid increased significantly (P<0.01) in bulgy morph tadpoles, osmotic pressure was maintained at the same level as control tadpoles by a significant increase (P<0.01) in Na and Cl ion concentrations. In our previous report, we identified a novel frog gene named pirica that affects the waterproofing of the skin membrane in tadpoles. Our results support the hypothesis that predator-induced expression of pirica on the skin membrane causes retention of absorbed water. Midline sections of bulgy morph tadpoles showed the presence of swollen connective tissue beneath the skin that was sparsely composed of cells containing hyaluronic acid. Mass spectrographic (LC-MS/MS) analysis identified histone H3 and 14-3-3 zeta as the most abundant constituents in the liquid aspirated from the connective tissue of bulgy tadpoles. Immunohistochemistry using antibodies against these proteins showed the presence of non-chromatin associated histone H3 in the swollen connective tissue. Histones and 14-3-3 proteins are also involved in antimicrobial activity and secretion of antibacterial proteins, respectively. Bulgy tadpoles have a larger surface area than controls, and their skin often has bite wounds inflicted by the larval salamanders. Thus, formation of the bulgy morph may also require and be supported by activation of innate immune systems.

The Study of Anatomic Relationship Between the Müller Muscle and the Tarsus in Asian Upper Eyelid

This study was performed to clarify the detailed anatomic relationship between the insertion of Müller muscle and the tarsus in Asian upper eyelids. Eight upper eyelids of 4 formalin-fixed Asian cadavers (4 males; age range, 48-69 years; mean age, 60.2 years) were examined. Three perpendicular dissected sections with a 2-mm thickness were obtained from each eyelid. One section was obtained from the midline, and another 2 sections were obtained, each 3-mm from the lateral and medial ends of the tarsus, respectively. Samples were stained with hematoxylin-eosin, Masson trichrome, and antismooth muscle actin antibody and examined microscopically. Müller muscle did not insert directly in the tarsus. However, its muscle tissues were tapered to the superior margin of the tarsus, and the space between the Müller muscle and the tarsus was bridged by fibrous connective tissue strands. Meanwhile, according to a result that measured distance between the Müller muscle insertion and the tarsus, the insertion of Müller muscle was positioned closer in the tarsus at the midline section than at the lateral or medial sections. This study suggests that the Müller muscle is broadly distributed around the superior border of the tarsus as tapered, aggregated smooth muscle bundles without direct insertion on the superior border of the tarsus, despite a few limitation.

Intratumor Administration of the Photosensitizer Pc 4 Affords Photodynamic Therapy Efficacy and Selectivity at Short Drug-Light Intervals

We evaluated intratumor (IT) versus intravenous (IV) administration of the photosensitizer Pc 4 with respect to tumor photosensitizer concentration, specificity, and responses to irradiation. BALB/c mice bearing intradermal EMT6 tumors were given 0.3 mg/kg Pc 4 injected IT or IV through the tail vein. Photosensitizer concentration was evaluated by chloroform extraction and localization assessed by fluorescence imaging and spectroscopy in vivo. Tumors were irradiated at 667 nm, 50 mW/cm2, and 100 J/cm2. Cures were defined as no palpable tumor 90 days after irradiation. Tumor Pc 4 concentrations 1 hour after IT administration were 35,000-fold higher than measured 24 hours after IV administration (0.112 vs 0.317 x 10-5µg Pc 4/mg tumor). Exquisite tumor selectivity was observed 1 hour after IT injection. Fluorescence imaging of freshly sectioned tumors revealed no regions devoid of sensitizer at this time point, with pixel intensities in a midline section within a factor of 3 of the peak intensity. For identical photosensitizer doses, IT administration significantly improved tumor responses to irradiation, with more than 70% of tumors cured with IT-Pc 4-PDT. In this model, IT-Pc 4 administration provides improved tumor control, greater selectivity, and opportunity for a short drug-light interval.

Traitement chirurgical des malformations anorectales hautes du nouveau-né : l’apport de la laparoscopie

Two anomalies must be corrected in high-type imperforate anus: first, the rectal end is located above the puborectalis muscle, and there is a fistula between the rectum and the urinary tract (male) or the vagina (female). The standard approach is posterior sagittal anorectoplasty, as described by De Vries and Peña, which requires midline section of the muscle complex. Georgeson first reported laparoscopically assisted anorectal pull-through in 2000. This approach offers many advantages, such as division of the fistula under direct visual control, better visualization of the anatomical components of the pelvic floor, and especially avoidance of muscle section. Long-term follow-up will be needed to assess continence outcomes.

The role of sensory pathways in Pavlovian conditioning in rabbit

In an earlier experiment we showed that selective attention plays a critical role in rabbit eye blink conditioning (Steele-Russell et al. in Exp Brain Res 173:587-602, 2006). The present experiments are concerned to examine the extent to which visual recognition processes are a separate component from the motor learning that is also involved in conditioning. This was achieved by midline section of the optic chiasma which disconnected the direct retinal projections via the brainstem to the cerebellar oculomotor control system. By comparing both normal and chiasma-sectioned rabbits it was possible to determine the dependence or independence of conditioning on the motor expression of the eye blink response during training. Both normal and chiasma-sectioned animals were tested using a multiple test battery to determine the effect of this redirection of the visual input pathways on conditioning. All animals were first tested for any impairment in visual capability following section of the optic chiasma. Despite the loss of 90% of retinal ganglion cell fibres, no visual impairment for either intensity or pattern vision was seen in the chiasma animals. Also no difference was seen in nictitating membrane (NM) conditioning to an auditory signal between normal and chiasma animals. Testing for motor learning to a visual signal, the chiasma rabbits showed a complete lack of any NM conditioning. However the sensory tests of visual conditioning showed that chiasma-sectioned animals had completely normal sensory recognition learning. These results show that NM Pavlovian conditioning involves anatomically separate and independent sensory recognition and motor output components of the learning.

Neural Organization of the Pathways From the Superior Colliculus to Trochlear Motoneurons

The neural organization of the pathways from the superior colliculus (SC) to trochlear motoneurons was analyzed in anesthetized cats using intracellular recording and transneuronal labeling techniques. Stimulation of the ipsilateral or contralateral SC evoked excitation and inhibition in trochlear motoneurons with latencies of 1.1-2.3 and 1.1-3.8 ms, respectively, suggesting that the earliest components of excitation and inhibition were disynaptic. A midline section between the two SCs revealed that ipsi- and contralateral SC stimulation evoked disynaptic excitation and inhibition in trochlear motoneurons, respectively. Premotor neurons labeled transneuronally after application of wheat germ agglutinin-conjugated horseradish peroxidase into the trochlear nerve were mainly distributed ipsilaterally in the Forel's field H (FFH) and bilaterally in the interstitial nucleus of Cajal (INC). Consequently, we investigated these two likely intermediaries between the SC and trochlear nucleus electrophysiologically. Stimulation of the FFH evoked ipsilateral mono- and disynaptic excitation and contralateral disynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the ipsilateral SC facilitated FFH-evoked monosynaptic excitation. Stimulation of the INC evoked ipsilateral monosynaptic excitation and inhibition, and contralateral monosynaptic inhibition in trochlear motoneurons. Preconditioning stimulation of the contralateral SC facilitated contralateral INC-evoked monosynaptic inhibition. These results revealed a reciprocal input pattern from the SCs to vertical ocular motoneurons in the saccadic system; trochlear motoneurons received disynaptic excitation from the ipsilateral SC via ipsilateral FFH neurons and disynaptic inhibition from the contralateral SC via contralateral INC neurons. These inhibitory INC neurons were considered to be a counterpart of inhibitory burst neurons in the horizontal saccadic system.

Physiological Characterization of Synaptic Inputs to Inhibitory Burst Neurons From the Rostral and Caudal Superior Colliculus

The caudal superior colliculus (SC) contains movement neurons that fire during saccades and the rostral SC contains fixation neurons that fire during visual fixation, suggesting potentially different functions for these 2 regions. To study whether these areas might have different projections, we characterized synaptic inputs from the rostral and caudal SC to inhibitory burst neurons (IBNs) in anesthetized cats. We recorded intracellular potentials from neurons in the IBN region and identified them as IBNs based on their antidromic activation from the contralateral abducens nucleus and short-latency excitation from the contralateral caudal SC and/or single-cell morphology. IBNs received disynaptic inhibition from the ipsilateral caudal SC and disynaptic inhibition from the rostral SC on both sides. Stimulation of the contralateral IBN region evoked monosynaptic inhibition in IBNs, which was enhanced by preconditioning stimulation of the ipsilateral caudal SC. A midline section between the IBN regions eliminated inhibition from the ipsilateral caudal SC, but inhibition from the rostral SC remained unaffected, indicating that the latter inhibition was mediated by inhibitory interneurons other than IBNs. A transverse section of the brain stem rostral to the pause neuron (PN) region eliminated inhibition from the rostral SC, suggesting that this inhibition is mediated by PNs. These results indicate that the most rostral SC inhibits bilateral IBNs, most likely via PNs, and the more caudal SC exerts monosynaptic excitation on contralateral IBNs and antagonistic inhibition on ipsilateral IBNs via contralateral IBNs. The most rostral SC may play roles in maintaining fixation by inhibition of burst neurons and facilitating saccadic initiation by releasing their inhibition.