Neural dynamics in cortex-striatum co-cultures-II. Spatiotemporal characteristics of neuronal activity

Neural dynamics in organotypic cortex-striatum co-cultures grown for three to six weeks under conditions of dopamine deficiency are described. Single neuron activities were recorded intra- and extracellularly, and spatiotemporal spreading of population activity was mapped using voltage-sensitive dyes. The temporal properties of spike firing were characterized by interspike interval histograms, autocorrelation and crosscorrelation.

Cortical pyramidal neurons (n = 40) showed irregular firing with a weak tendency to burst or to oscillate. Crosscorrelations revealed strong near-coincident firing and synaptic interactions. Disinhibition was a notable feature in a strongly firing cortical interneuron. Cortical activity spread in the co-culture, thus inducing an overall, homogeneous depolarization in the striatal part. Striatal cells were divided into principal cells and type I and II secondary cells. Principal cells (n = 40) were similar to those reported previously in vivo. Spiking activity ranged from irregular spiking at very low rates to episodic bursting, with an average burst duration of 1 s. Interspike intervals were single-peaked. Intracellular recordings revealed characteristic, long-lasting subthreshold depolarizations (“enabled state”) that were shortened by local muscarinic receptor blockade. During prolonged time periods in the “enabled state”, locally applied bicuculline induced strong firing in most principal neurons. Striatal secondary type I neurons (n = 25) showed high spiking rates, single- and double-peaked interval histograms and low-threshold, short-lasting stereotyped bursting activity and occasional rhythmic bursting. The firing of these neurons was increased by bicuculline. Crosscorrelations showed synchronization of these cells with principal cell activity. Secondary type II neurons (n = 15) revealed tonic, irregular firing patterns similar to cortical neurons, except with occasional firing in doublet spikes.

We conclude that under conditions of dopamine deficiency in corticostriatal co-cultures (i) the cortex induces the “enabled” state and typical bursting mode in striatal principal neurons; (ii) principal neurons are strongly inhibited during the “enabled” state; (iii) muscarinic activity, presumably from tonically active striatal cholinergic interneurons, stabilizes the “enabled” state; (iv) striatal GABAergic interneurons receive synaptic inhibition and take part in synchronized activity among striatal principal cells. Our results favor the view of the striatum as a lateral inhibition network.     

Spatial relation of the acetylcholinesterase-rich domain to the visual topography in the feline superior colliculus

Summary The superior colliculus (SC) of the cat shows a prominent compartmentalized organization at the level of its intermediate layers. The mosaic of these compartments is apparent in the pattern of acetylcholinesterase (AChE) staining. Patches of high AChE-activity are sharply set off from surrounding areas in the caudal SC while they are less distinct anteriorly. The rostral part lacks such obvious compartments. Thus, a structural reorganization apparently cuts across the topographical representations spread out in the SC. In order to test if this compartmental gradient relates to the topographic maps of the colliculus, retinotopic landmarks were visualized in the superficial layers by labeling the retinotectal pathway. In the SC ipsilateral to the eye injected with horseradish peroxidase (HRP) a paucity of labeling indicated the zone representing the ipsilateral visual half-field. Serial reconstructions of collicular sections, cut longitudinally or tangentially, revealed that the non-compartmentalized part of the intermediate layers corresponds to the representation of the ipsilateral visual half-field in the layers above, while an intricate mosaic array of compartments prevail in tectal zones related to the representation of the contralateral visual half-field.     

大鼠延髓网状背侧亚核下行投射终末在脊髓灰质的分布

本研究应用PHA－L顺行追踪技术研究了大风延髓网状背测亚核（SRD）至脊髓灰质下行投射的终止部位。结果表明：SRD发出的下行纤维走行于脊髓的背外侧京中，从高位至低位，脊髓灰质中的PHA－L顺标终末的密度逐渐降低。SRD的下行投射终未在脊髓中具有明显的同侧分布优势，主要终止在同侧脊历灰质的Ⅳ～Ⅶ层和X层，Ⅰ、Ⅱ层中只有少量的标记终末，对侧脊髓灰质中除了在Ⅳ层和X层中有中等密度的颁标终末分布外，其余各层中几乎无标记终未、PHA－L顺标终未与BSI-B4标记的初级传入C纤维终末在Ⅰ．Ⅱ层内重叠公布．本研究为SRD在调控脊髓的伤害性信息传递方面也起重要作用这一论点提供了直接的形态学依据．     

Vestibulo-thalamic projection to the anterior suprasylvian cortex of the cat

Summary Suggestive evidence as to the site of a major thalamic relay of the vestibular projection to the anterior suprasylvian (ASS) cortex in the cat has been obtained using the retrograde axonal transport of horseradish peroxidase. The thalamo-cortical neurons are located in several patches surrounding the posterior margins of the ventro-basal complex (VB). This area also was found to receive vestibulo-thalamic projections. It comprises different nuclear groups known to carry somatic, accoustic, visual or combined information, which possibly have certain functions related to kinaesthesia and body orientation in common.Abbreviations ANS ansate sulcus - ASSS anterior suprasylvian sulcus - CM, N centrum medianum - CL, N centralis lateralis - C.r Corpus restiformis - D, N vestibularis descendens - i.c., N intercalatus - L, N vestibularis lateralis - LD, N lateralis dorsalis - LG, N geniculatus lateralis - LP, N lateralis posterior - M, N vestibularis medialis - MG, N geniculatus medialis - mcMG pars magnocellularis of MG - MD, N medialis dorsalis - N.c., N cuneatus - N. in. VIII, N interstitialis of the VIIIth cranial nerve - N. pr. V principal sensory trigeminal nucleus - N. tr. sp. V nucleus of the spinal trigeminal tract - p.h., N praepositus hypoglossi - Pu pulvinar - S, N vestibularis superior - SG, N suprageniculatus - VL, N ventralis lateralis - VPL, N ventralis posterolateralis - VPM, N ventralis posteromedialis - VI, X, XII motor cranial nerve nuclei - y, z small cell groups of Brodal and Pompeiano Supported by Deutsche Forschungsgemeinschaft, SFB 70     

Real-time automatic extraction of lumen region and boundary from endoscopic images

A new approach to the automatic extraction of the lumen region and its boundary for gastrointestinal (GI) endoscopic images is presented. First, a quasi region of interest, the darker regions of the image, is segmented using a region splitting scheme termed progressive thresholding. The centre of mass of this segmented region acts as a seed for further processing. Then the lumen region is obtained using a region growing technique called the integrated neighbourhood search (INS). A new quad structure based technique is introduced to enhance the INS speed significantly. A back projection algorithm is suggested to optimise the search for pixels belonging to the lumen region and boundary. A boundary-thinning algorithm is also proposed to remove the redundant pixels from the lumen boundary and to generate a connected single pixel width boundary. The proposed approach does not need a priori knowledge about the image characteristics. The experimental results indicate that the proposed technique enhances the speed of conventional INS by 45.5% to 28.6% based on the lumen size varying from 22,709 pixels to 4947 pixels. The main advantage of the proposed technique is its high-speed response that facilitates real-time analysis of endoscopic images.     

Individual corticorubral neurons project bilaterally during postnatal development and following early contralateral cortical lesions

The corticorubral projections in adult cats are primarily uncrossed. However, early in development and after early unilateral lesions of the sensorimotor cortex, crossed corticorubral projections are also observed. The present study was performed to disclose (1) whether the crossed projections originate from neuronal subpopulations different from those producing uncrossed ones and (2) how the neurons that give rise to the crossed projections in the lesioned animals are related to those occurring in normal development. We injected fluorescent latex microspheres into the red nucleus of two groups of animals: (1) intact kittens at postnatal week 3 and (2) kittens that had received unilateral ablation of the cerebral cortex at this stage and were then allowed to survive for at least 4 weeks. Red fluorescing microspheres were injected on one side and green ones on the other. In both normal and lesioned kittens, a number of cells in the cortex were labeled as a result of the contralateral as well as the ipsilateral injections, and no difference in size or distribution was found between the cells labeled from contralateral and ipsilateral injections. More than half of the cells labeled from contralateral injections were double-labeled in both groups of animals. These results indicate that individual corticorubral cells project bilaterally in normal development as well as following unilateral lesions of the cortex. With respect to the cells producing crossed projections, they were similar in both laminar and regional distributions between the intact and lesioned animal, suggesting that the crossed projections arise from the same neuronal subpopulation before and after cortical lesions. This view was supported by sequential injections of the tracers, which indicated that cells normally projecting contralaterally maintained the crossed projection after the lesions. Taking into account our previous observations that growth and proliferation of crossed corticorubral axons took place in the red nucleus (Murakami et al. 1991a), it is likely that growth and proliferation of the axons in denervated targets play a major role in lesion-induced establishment of aberrant projections.     

The medullary projection from the mesencephalic trigeminal nucleus. An experimental study with comments on the intrinsic trigeminal connections

Summary The medullary projection from the mesencephalic trigeminal nucleus has been studied in cats where the wheat germ agglutinin-horseradish peroxidase complex has been used as a retrograde and anterograde tracer. All injections were made at the level of the caudal pole of the inferior olive and show that it is especially the lateral part of nucleus parvicellularis of the reticular formation which is the main area for termination of the fibres. In addition, it can not be excluded that the descending fibres also reach the medialmost part of the spinal trigeminal sensory nucleus (pars magnocellularis and the adjoining pars gelatinosa). All three cell types of the mesencephalic trigeminal nucleus are labelled, the large globular, the small globular and the polygonal cells. Some of these cells are only faintly labelled. The observations confirm previous studies of the intrinsic trigeminal connections, but show that when the wheat germ agglutinin-horseradish peroxidase complex is used as a tracer, the origin as well as the termination for the intrinsic fibres (also the commissural) can be studied in the same section. The use of this sensitive tracer also shows new details within the intrinsic connections. The findings are discussed with special reference to the recent observations by Ruggiero et al. (1982). These authors found that in rabbit and rat there is a more restricted termination for the descending mesencephalic trigeminal fibres. The discrepancies between the observations seem to indicate that there are species differences as regards the connections between the mesencephalic trigeminal nucleus and the nuclei in the lower part of the brain stem.     

黄喉鹀耳蜗核的传出投射

用HRP顺行追踪方法,研究黄喉鵐(emberiza elegans)的两对耳蜗核,即角状核和巨细胞核的传出投射.将HRP注入角状核,在双侧上橄榄核,对侧外侧丘系核腹侧部,外侧丘系腹核及中脑背外侧核的背侧1/4的区域见到顺行标记纤维或终末.将HRP注入巨细胞核,标记纤维或终末分布于双侧层状核;标记细胞分布于同侧上橄榄核.结果表明:角状核投射至双侧上橄榄核,对侧外侧丘系核腹侧部,外侧丘系腹核及中脑背外侧核的背侧部.巨细胞核投射至双侧层状核.此外,巨细胞核接受同侧上橄榄核的传人,它可能是一条听觉的反馈回路.     

Commissural and intrinsic connections of the vestibular nuclei in the rabbit: a retrograde labeling study

Summary The intrinsic and commissural projection of the vestibular nuclei were investigated by means of retrograde transport of normal (HRP) and wheatgerm-agglutinated horseradish peroxidase (WGA-HRP). It was found that within each vestibular complex, the superior (SV), medial (MV) and descending (DV) vestibular nuclei are reciprocally connected. A rostrocaudally oriented column of medium-sized and large neurons, comprising the central SV and the magnocellular MV (MVmc) receives input from the surrounding neurons and does not reciprocate this projection. Efferents from group y terminate in the SV, MV and DV. The infracerebellar nucleus (INF) as well as the interstitial nucleus of the VIII the nerve (IN) supply fibers to the MV and DV. The neurons that participate in the commissural projection are distributed throughout the vestibular complex with the exception of the lateral vestibular nucleus (LV) and group x. The largest number of cells was found in the MV. The HRP labeled cells show a tendency to cluster into rostrocaudally oriented groups. Each nucleus projects to more than one contralateral nucleus. Group y shows a more extensive contralateral projection than the bordering INF. It was concluded that quantitative differences in connectivity were present between a core region in the vestibular complex and peripheral parts. This core region comprises the central SV, the LV, the MVmc and extends into the rostral DV. It receives predominantly intrinsic input from the surrounding vestibular neurons and is in contrast to these latter neurons only minimally involved in the commissural projection.Abbreviations AChE acetylcholinesterase - bc brachium conjunctivum - bp brachium pontis - CE nucleus cuneatus externus - CO nuclei cochlearis - cr corpus restiforme - DV nucleus vestibularis descendens - DX nucleus dorsalis vagi - F nucleus fastigii - flm fasciculus longitudinalis medialis - gVII genu of the nervus facialis - group x, y, f groups x, y and f of Brodal - HRP horseradish peroxidase - IA nucleus interpositus anterior - IN nucleus interstitialis of nVIII - INF nucleus infracerebellaris - L nucleus lateralis - LV nucleus vestibularis lateralis - flm fasciculus longitudinalis medialis - MV nucleus vestibularis medialis - MVc caudal MV - MVmc magnocellular MV - MVpc parvocellular MV - nV nervus trigeminus - nVI nervus abducens - nVII nervus facialis - NV par nucleus vestibularis parabrachialis - PH nucleus prepositus hypoglossi - rV ramus descendens of nV - S nucleus and tractus solitarius - sad stria acustica dorsalis - SV nucleus vestibularis superior - tu tractus uncinatus - VI nucleus abducens - VM nucleus masticatorius - VOR vestibulo-ocular reflex - VP nucleus princeps trigemini - WGA-HRP wheatgerm-agglutinated HRP - XII nucleus hypoglossus