A note on the definition and the development of cerebellar Purkinje cell zones.

The definition of Purkinje cell zones by their white matter compartments, their physiological properties, and their molecular identity and the birthdate of their Purkinje cells will be reviewed.

Prediction of plant species occurrence as affected by nitrogen deposition and climate change on a European scale.

Plant species occurrence in Europe is affected by changes in nitrogen deposition and climate. Insight into potential future effects of those changes can be derived by a model approach based on field-based empirical evidence on a continental scale. In this paper, we present a newly developed empirical model PROPS, predicting the occurrence probabilities of plant species in response to a combination of climatic factors, nitrogen deposition and soil properties. Parameters included were temperature, precipitation, nitrogen deposition, soil pH and soil C/N ratio. The PROPS model was fitted to plant species occurrence data of about 800,000 European relevés with estimated values for pH and soil C/N ratio and interpolated climate and modelled N deposition data obtained from the Ensemble meteo data set and EMEP model results, respectively. The model was validated on an independent data set. The test of ten species against field data gave an average Pearson's r-value of 0.79. PROPS was applied to a grassland and a heathland site to evaluate the effect of scenarios for nitrogen deposition and climate change on the Habitat Suitability Index (HSI), being the average of the relative probabilities, compared to the maximum probability, of all target species in a habitat. Results for the period 1930-2050 showed that an initial increase and later decrease in nitrogen deposition led to a pronounced decrease in HSI, and with dropping nitrogen deposition to an increase of the HSI. The effect of climate change appeared to be limited, resulting in a slight increase in HSI.

Development of a reactor for the in situ monitoring of 2D materials growth on liquid metal catalysts, using synchrotron x-ray scattering, Raman spectroscopy, and optical microscopy.

Liquid metal catalysts (LMCats) (e.g., molten copper) can provide a new mass-production method for two-dimensional materials (2DMs) (e.g., graphene) with significantly higher quality and speed and lower energy and material consumption. To reach such technological excellence, the physicochemical properties of LMCats and the growth mechanisms of 2DMs on LMCats should be investigated. Here, we report the development of a chemical vapor deposition (CVD) reactor which allows the investigation of ongoing chemical reactions on the surface of a molten metal at elevated temperatures and under reactive conditions. The surface of the molten metal is monitored simultaneously using synchrotron x-ray scattering, Raman spectroscopy, and optical microscopy, thereby providing complementary information about the atomic structure and chemical state of the surface. To enable in situ characterization on a molten substrate at high temperatures (e.g., ∼1370 K for copper), the optical and x-ray windows need to be protected from the evaporating LMCat, reaction products, and intense heat. This has been achieved by creating specific gas-flow patterns inside the reactor. The optimized design of the reactor has been achieved using multiphysics COMSOL simulations, which take into account the heat transfer, fluid dynamics, and transport of LMCat vapor inside the reactor. The setup has been successfully tested and is currently used to investigate the CVD growth of graphene on the surface of molten copper under pressures ranging from medium vacuum up to atmospheric pressure.

Dissipation and resonance frequency shift of a resonator magnetically coupled to a semiclassical spin.

We calculate the change of the properties of a resonator, when coupled to a semiclassical spin by means of the magnetic field. Starting with the Lagrangian of the complete system, we provide an analytical expression for the linear response function for the motion in the case of a mechanical resonator and the current for the case of an electromagnetic resonator, thereby considering the influence of the resonator on the spin and vice versa. This analysis shows that the resonance frequency and effective dissipation factor can change significantly due to the relaxation times of the spin. We first derive this for a system consisting of a spin and mechanical resonator and thereafter apply the same calculations to an electromagnetic resonator. Moreover, the applicability of the method is generalized to a resonator coupled to two-level systems and more, providing a key to understand some of the problems of two-level systems in quantum devices.

Fast and reliable pre-approach for scanning probe microscopes based on tip-sample capacitance.

Within the last three decades Scanning Probe Microscopy has been developed to a powerful tool for measuring surfaces and their properties on an atomic scale such that users can be found nowadays not only in academia but also in industry. This development is still pushed further by researchers, who continuously exploit new possibilities of this technique, as well as companies that focus mainly on the usability. However, although imaging has become significantly easier, the time required for a safe approach (without unwanted tip-sample contact) can be very time consuming, especially if the microscope is not equipped or suited for the observation of the tip-sample distance with an additional optical microscope. Here we show that the measurement of the absolute tip-sample capacitance provides an ideal solution for a fast and reliable pre-approach. The absolute tip-sample capacitance shows a generic behavior as a function of the distance, even though we measured it on several completely different setups. Insight into this behavior is gained via an analytical and computational analysis, from which two additional advantages arise: the capacitance measurement can be applied for observing, analyzing, and fine-tuning of the approach motor, as well as for the determination of the (effective) tip radius. The latter provides important information about the sharpness of the measured tip and can be used not only to characterize new (freshly etched) tips but also for the determination of the degradation after a tip-sample contact/crash.

Lodewijk Bolk and the comparative anatomy of the cerebellum.

The cerebellum of mammals is histologically uniform, but it varies greatly in the relative size of its different parts. The Dutch anatomist Lodewijk Bolk studied a large series of mammalian cerebella, and put forward a general scheme of organization that can be applied to all mammals. Bolk also speculated about the functional role of different regions of the cerebellum, based on the idea that there might be a single somatotopically organized representation of the body surface on the cerebellar cortex. Although his idea of a single map is wrong, Bolk's anatomical descriptions are thorough, and his insights are profound. These descriptions formed the basis for much subsequent thinking about the structure of the cerebellum.

The anatomy of the cerebellum.

Vertebrate cerebella occupy a position in the rostral roof of the 4th ventricle and share a common pattern in the structure of their cortex. They differ greatly in their external form, the disposition of the neurones of the cerebellar cortex and in the prominence of their afferent, intrinsic and efferent connections.

The anatomy of the cerebellum.

Vertebrate cerebella occupy a position in the rostral roof of the 4th ventricle and share a common pattern in the structure of their cortex. They differ greatly in their external form, the disposition of the neurons of the cerebellar cortex and in the prominence of their afferent, intrinsic and efferent connections.

Organization of projections from the inferior olive to the cerebellar nuclei in the rat.

The detailed organization of projections from the inferior olive to the cerebellar nuclei of the rat was studied by using anterograde tracing. The presence of a collateral projection to the cerebellar nuclei could be confirmed, and a detailed organization was recognized at the nuclear and subnuclear level. Olivary projections to the different parts of the medial cerebellar nucleus arise from various parts of the caudal half of the medial accessory olivary nucleus. The interstitial cell groups receive olivary afferents from the intermediate part of the medial accessory olive and from the dorsomedial cell column. A mediolateral topography was noted in the projections from the rostral half of the medial accessory olive to the posterior interposed nucleus. Olivary projections to the lateral cerebellar nucleus are derived from the principal olive according to basically inversed rostrocaudal topography. Projections from the dorsomedial group of the principal olive to the dorsolateral hump were found to follow a basically rostrocaudal topography. The anterior interposed nucleus receives olivary afferents from the dorsal accessory olive. Its rostromedial parts are directed to the lateral part of the anterior interposed nucleus and its caudolateral part reach the medial anterior interposed nucleus. No terminal arborizations in the cerebellar nuclei were found to originate from (1) the dorsal fold of the dorsal accessory olive, which resulted in projections to the lateral vestibular nucleus and (2) the dorsal cap of Kooy. It was noted that the olivary projection to the cerebellar nuclei is strictly reciprocal to the nucleo-olivary projection as described by Ruigrok and Voogd (1990). Moreover, it is suggested that the olivonuclear projection adheres to the organization of the climbing fiber projection to the cerebellar cortex and to the corticonuclear projection, thus, establishing and extending the detailed micromodular organization of the connections between inferior olive and cerebellum.

The projection of the nucleus reticularis tegmenti pontis and adjacent regions of the pontine nuclei to the central cerebellar nuclei in the cat.

The projection of the nucleus reticularis tegmenti pontis (NRTP) and the pontine nuclei (NP) to the central cerebellar nuclei (CCN) was investigated by means of anterograde transport of tritiated leucine. Although termination was found in all the CCN, it was most pronounced in the lateral nucleus and the lateral aspect of the posterior interposed nucleus. The extreme lateral aspect of the anterior interposed nucleus and the caudal part of the fastigial nucleus received a projection of modest intensity. Termination in the infracerebellar nucleus and group Y is likely to be present but could not be confirmed with certainty from the light microscopical material. The contribution from the NP was small and originated from the dorsolateral and dorsal paramedian subdivisions of the NP. Within the NRTP the total area giving rise to projections to the CCN was extensive, and the origin of the projections to the individual CCN overlapped considerably. The projection of the NRTP to the ventrocaudal part of the lateral nucleus was found in conjunction with a projection to the ventrolateral part of the posterior interposed nucleus. Both projections seemed to branch off the fiber bundle terminating in the ventral paraflocculus. Similar correlations could be established in the projection of the NRTP to the dorsal paraflocculus and crus II of the ansiform lobule with other parts of the lateral and posterior interposed nuclei. It was concluded that the transverse, lobular organization of mossy fibers, which differs fundamentally from the longitudinal, modular organization of climbing fibers, is maintained in the collateral projection to the CCN. The results are further discussed in relation to the corticonuclear projection and the engagement of the NRTP and different parts of the CCN in pontocerebellar circuits.

Myeloarchitecture of the cerebellum of the chicken (Gallus domesticus): an atlas of the compartmental subdivision of the cerebellar white matter.

A myeloarchitectonic atlas of the longitudinal (or mediolateral) subdivision of the cerebellum of the chicken (white Leghorn) was prepared from serial Häggqvist or toluidine-blue-stained sections of five animals. This myeloarchitectonic subdivision is based on the alternate occurrence of large fiber accumulations (LFAs) and small fiber areas (SFAs) in the cerebellar white matter and allows the distinction of a number of parasagittal fiber compartments, each of which consists of a medial LFA and a lateral SFA. The compartmental subdivision of the cerebellar white matter in mammals and birds derives its importance from the fact that essentially it corresponds to the organization of the afferent and efferent connections of the cerebellar cortex. The simple structure of the avian cerebellum makes it ideally suited for a complete description of its compartmental subdivision and may serve as a natural system of coordinates in future anatomical and physiological studies. The number of fiber compartments that can be counted in the chicken cerebellum on either side of the midline varies from six (in the narrowest folium I) to nine (in the widest folia IX and X) and is approximately the same as in mammals, in which a maximum of eight or ten compartments can be recognized. On the basis of the organization of its myeloarchitecture and the otherwise relatively scarce data on the organization of the connections of its cortex, it can, therefore, be postulated that the avian cerebellum is the homologue of the entire mammalian cerebellum. In addition, the present knowledge of the connections of the cerebellar cortex in birds indicates that the avian compartments 1-3 may correspond to the mammalian compartments A1, A2, and A3 (or X), whereas the avian compartment 4 or 5 (or both) may represent the mammalian B compartment. Lack of further anatomical data so far precludes conclusions on a possible homology between the avian compartments 6-9 and the mammalian C and D compartments.

Time dependence of terminal degeneration in spino-cerebellar mossy fiber rosettes in the chicken and the application of terminal degeneration in successive degeneration experiments.

Mossy fiber rosettes in the granular layer of the cerebellar cortex were studied after sections of the lateral funiculus of the spinal cord of the chicken and silver impregnation with the Fink-Heimer ('67) method I. After a survival time of two or three days two types of degenerated rosettes were found. The first type is characterized by digitiform protrusions, the second type of rosette is spherical. Both types are covered by small argyrophilic particles which disappear when the degeneration proceeds. With longer survival times the rosettes become swollen and finally disintegrate and lose their argyrophilia. After a survival time of 30 days only debris of rosettes can be found. These observations were used to determine the cerebellar cortical projection mossy fibers originating from segments of the spinal cord isolated in "successive degeneration" experiments consisting of a chronic cordotomy followed by an acute cordotomy rostral to the first one.

The parasagittal zonation within the olivocerebellar projection. I. Climbing fiber distribution in the vermis of cat cerebellum.

After lesions of inferior olive, survival times of 5 to 12 days and Nauta staining, degeneration is present in white matter and central cerebellar nuclei and Deiters' nucleus. Shorter survival times from 40 to 60 hours and Fink-Heimer impregnantion reveal degenerating climbing fiber terminals in the molecular layer. With 3H-leucine autoradiography and survival times of three to seven days the entire trajectory of the climbing fibers can be traced. Olivocerebellar fibers cross in the brain stem and terminate contralaterally in cortex and central nuclei. Occasional labeling of mossy fiber terminals is explained by involvement of reticular nuclei. Small parts of the inferior olive connect with narrow longitudinal zones in the cortex through compartments in the white matter. The corresponding distribution of olivocerebellar fibers and Purkinje cell axons over these compartments suggests that the organization of the olivocerebellar and corticonuclear projection is essentially similar. Collaterals always terminate in the central cerebellar nucleus which receives a corticonuclear projection from the zone in which the parent fibers terminate. Caudal medial accessory olive projects to medial vermal zone A and to fastigial nucleus, subnucleus beta projecting to lobule VII and caudal fastigial nucleus. Caudal dorsal accessory olive projects to lateral vermal zone B in lobules I-VI, Deiters' nucleus and dorsomedial subnucleus of interposed nucleus. The caudal principal olive (dorsal cap, ventrolateral outgrowth receiving visual and vestibular input) projects to flocculo-nodular lobe.

Acetylcholinesterase staining in subdivisions of the cat's inferior olive.

The present paper describes a unique distribution of true AChE activity in the IO. In the dorsal accessory olive three areas with high AChE activity can be distinguished. The medial accessory olive can be subdivided into a caudal part which shows rostro-caudally directed bands with different enzymatic activity, and a rostral part which shows a more uniform, medium activity. In the nucleus beta and the dorso-medial cell column, AChE activity is low. The ventral and dorsal lamellae of the principal olive contain areas with high, medium, and low activity. The dorsal cap is strongly positive, while the ventrolateral outgrowth is negative for AChE. Enzyme distribution cannot be fully explained on the base of the known afferent and efferent connections with the IO. However, histochemical results provide evidence that generally supports a subdivision of the IO that mirrors these connections (Brodal, '40; Armstrong et al., '74' Boesten and Voogd, '75; Groenewegen et al., '75).

Cerebellar nucleo-olivary projections in the rat: an anterograde tracing study with Phaseolus vulgaris-leucoagglutinin (PHA-L).

In order to evaluate the reciprocity of olivo-cerebellar and cerebello-olivary connections, a detailed description of the cerebellar nucleo-olivary projection in the rat is presented using small, iontophoretic injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin. Sparse projections were found to arise from the rostral part of the medial cerebellar nucleus toward the lateral part of the caudal medial accessory olive. Its medial parts receive a projection from the dorsolateral protuberance of the medial cerebellar nucleus. Caudal and lateral regions of the medial cerebellar nucleus project to the "beta" group and dorsomedial cell column. Heavy olivary projections to circumscribed parts of the inferior olive were found after injections in the remaining cerebellar nuclei. The medial part of the posterior interposed nucleus connects to caudolateral areas of the rostral half of the medial accessory olive, whereas lateral areas project to more rostromedial parts. The most ventromedial part of the lateral cerebellar nucleus projects to the ventrolateral outgrowth. Adjacent medial, ventral, and caudal regions connect to the ventral leaf of the principal olive. The cerebellar origin of the projection to its dorsal leaf is located in lateral, dorsal, and rostral parts of the lateral cerebellar nucleus. The dorsolateral hump projects to the dorsomedial group of the rat inferior olive. Rostromedial projections to the dorsal accessory olive originate from the lateral part of the anterior interposed nucleus, whereas its medial parts project to more lateral and caudal regions of this olivary subnucleus. The dorsal fold of the dorsal accessory olive does not receive a projection from the cerebellar nuclei but from the lateral vestibular nucleus. No cerebellar projections were found to the dorsal cap. Relatively strong ipsilateral projections, which were the mirror images of the contralateral projections, were observed in the dorsomedial group, rostral medial accessory olive, and ventral leaf of the principal olive. When both the inferior olive and the cerebellar nuclei are considered as folded but continuous sheets of grey matter, the complete nucleo-olivary projection can be described as a simple transformation.

Projections of the dorsal column nuclei and the spinal cord on the inferior olive in the cat.

This study demonstrated partially overlapping fiber termination areas in the inferior olive originating from the dorsal column nuclei and the spinal cord. Based on the distribution of the dorsal accessory olive can be divided into a rostral and a caudal part. In the caudal part terminations are found of fibers originating in the contralateral gracile nucleus and in the lumbar and cervical spinal cord. Terminations in the rostro-medial part of the dorsal accessory olive arise from the contralateral internal cuneate nucleus and from the opposite intermediate grey at C.1. Fibers from more caudal regions of the internal cuneate nucleus terminate in the dorsal accessory olive caudal to those originating from more rostral regions of this nucleus. The gracile nucleus and the lumbar spinal cord project to the rostro-lateral portion of the dorsal accessory olive. The terminations in the medial accessory olive from the lumbar spino-olivary fibers are found in a laterally located zone in the caudal half of the medial accessory olive, while terminations of the contralateral internal cuneate nucleus are found at a more rostral level in the medial part of the medial accessory olive. Connections between the inferior olive and the caudal part of the spinal trigeminal nucleus, the lateral cervical nucleus and the cervical dorsal horn could not be demonstrated.

Ultrastructural identification and localization of climbing fiber terminals in the fastigial nucleus of the cat.

Following injections of 3H-leucine and 35S-methionine in the caudal half of the medial accessory olive, labeled climbing fibers were found contralateral to the injection site in the sagittal A-zone of the cerebellar vermis and in the fastigial nucleus. Labeling in the fastigial nucleus was analyzed with ultrastructural autoradiography. Labeled boutons of climbing fibers were found in the neuropil but never on somata. They contain spherical vesicles and occasionally some dense core vesicles in an electron-lucent matrix. The terminals of climbing fiber collaterals in the fastigial nucleus resemble climbing fiber terminals in the molecular layer with respect to their internal ultrastructural characteristics.

Anatomical compartments in the white matter of the rabbit flocculus.

The white matter of the rabbit flocculus is subdivided into five compartments by narrow sheets of densely staining acetylcholinesterase-positive fibers. The most lateral compartment is continuous with the C2 compartment of the paraflocculus and contains the posterior interposed nucleus. The other four compartments are numbered from lateral to medial as floccular compartments 1, 2, 3, and 4 (FC1-4). FC1-3 continue across the posterolateral fissure into the adjacent folium (folium p) of the ventral paraflocculus. FC4 is present only in the rostral flocculus. In the caudal flocculus FC1 and FC3 abut dorsal to FC2. Fibers of FC1-4 can be traced into the lateral cerebellar nucleus and the floccular peduncle. The presence of acetylcholinesterase in the deep stratum of the molecular layer of the flocculus and ventral paraflocculus distinguishes them from the dorsal paraflocculus. The topographical relations to the flocculus and the floccular peduncle with group y and the cerebellar nuclei are discussed.

Zonal organization of the flocculovestibular nucleus projection in the rabbit: a combined axonal tracing and acetylcholinesterase histochemical study.

With the use of retrograde transport of horseradish peroxidase we confirmed the observation of Yamamoto and Shimoyama ([1977] Neurosci Lett. 5:279-283) that Purkinje cells of the rabbit flocculus projecting to the medial vestibular nucleus are located in two discrete zones, FZII and FZIV, that alternate with two other Purkinje cell zones, FZI and FZIII, projecting to the superior vestibular nucleus. The retrogradely labeled axons of these Purkinje cells collect in four bundles that occupy the corresponding floccular white matter compartments, FC1-4, that can be delineated with acetylcholinesterase histochemistry (Tan et al. [1995a] J. Comp. Neurol., this issue). Anterograde tracing from small injections of wheat germ agglutin-horseradish peroxidase in single Purkinje cell zones of the flocculus showed that Purkinje cell axons of FZII travel in FC2 to terminate in the medial vestibular nucleus. Purkinje cell axons from FZI and FZIII occupy the FC1 and FC3 compartments, respectively, and terminate in the superior vestibular nucleus. Purkinje cell axons from all three compartments pass through the floccular peduncle and dorsal group y. In addition, some fibers from FZI and FZII, but not from FZIII, arch through the cerebellar nuclei to join the floccular peduncle more medially. No anterograde tracing experiments were available to determine the projections of the FZIV and C2 zones. The functional implications of these results are discussed.

Organization of inferior olivary projections to the flocculus and ventral paraflocculus of the rat cerebellum.

The climbing fiber projection to the rat flocculus and adjacent ventral paraflocculus was investigated by using Phaseolus vulgaris-leucoagglutinin as an anterograde and horseradish peroxidase as a retrograde tracer. Large injections of horseradish peroxidase in the flocculus and ventral paraflocculus indicated that the climbing fibers to this region are derived exclusively from any of the following contralateral olivary regions: the dorsal cap of Kooy, the ventrolateral outgrowth, the caudal half of the ventral leaf of the principal olive near its lateral bend, and the rostral pole of the medial accessory olive. Subsequent anterograde and retrograde studies with small injections demonstrated that the latter area projects to the C2 zone, which runs caudally in the ventral paraflocculus and enters the caudal most aspect of the flocculus. The ventral leaf of the principal olive is connected to a D zone in the cerebellar hemisphere and paraflocculus, which, upon entering the ventral paraflocculus, divides into a caudal and rostral strip, termed FD and FD', respectively. The dorsal cap and the ventrolateral outgrowth each project to two distinct zones in the flocculus and part of the ventral paraflocculus. Two floccular zones, which are continuous with the parafloccular FD and FD' zones, receive their climbing fibers from the ventrolateral outgrowth. Two other zones, (FE and FE') receive their climbing fibers from the dorsal cap. The FE' zone is found at the rostral pole of the flocculus and is followed caudalwards by the FD', FE, FD, and C2 zones, respectively. The rostromedial part of the dorsal cap is connected to the continuation of the FE zone into the ventral paraflocculus. The observation that the dorsal cap and the ventrolateral outgrowth are both connected to a set of two alternating zones of floccular/ventral parafloccular Purkinje cells is in agreement with recent studies in the rabbit, and suggests that these zones reflect functionally distinct and discrete units related to specific aspects of visuomotor control.