Zonal organization of cortico-nuclear and nucleo-cortical projections of the paramedian lobule of the cat cerebellum. 1. the C1 zone.

The cortico-nuclear (C-N) and nucleo-cortical (N-C) projections of the C1 cortical zone in pars anterior (pa) and pars copularis (pc) of the paramedian lobule (PML) in the posterior lobe of the cat cerebellum were investigated with a combined electrophysiological and neuroanatomical technique. In each experiment the mediolateral boundaries of the zone were located on the cortical surface by recording field potentials mediated via climbing fibres and evoked in the zone by activity elicited in spino-olivocerebellar paths through percutaneous stimulation of fore- and hindlimbs; a small (15-30 nl) injection of WGA-HRP was then made into the zone. The distributions in the deep cerebellar nuclei were determined (with light microscopy) both for terminal labelling due to anterograde axonal transport by Purkinje cells and for cell bodies labelled due to retrograde transport in N-C axons. The extent to which injection sites were confined to the C1 zone was assessed both by comparing injection site and zone widths and by determining the distributions of retrogradely labelled neurones within the contralateral inferior olive. The C-N projection from the part of the zone in PML pa (a forelimb part) terminates almost exclusively (perhaps exclusively) in nucleus interpositus anterior (NIA), primarily in caudal and dorsal parts, where it overlaps heavily with the C-N projections from the lobule V parts (also forelimb parts) of the C1 and C3 zones as previously defined. The C-N projection from the part of the zone in PML pc (a hindlimb part) also terminates virtually exclusively in NIA but primarily in almost all parts of the medial third of the nucleus. There is, nevertheless, sufficient overlap between the PML pa and PML pc projections that approximately one third of the termination territory of each projection overlaps that of the other. The PML pc part of the zone is almost entirely lacking in a N-C projection, as previously found for the lobule V part of the C1 zone (and C3 zone). However, the PML pa part of the zone receives N-C projections that arise, in descending order of size, from nucleus interpositus posterior (NIP), from NIA, from the NIA/nucleus lateralis (NL) fusion area and (perhaps) NL. The projection from NIP is similar in size to that provided by the nucleus to the C2 zone in lobule V of the anterior lobe. The findings are discussed, with particular emphasis on their implications for the hypothesis that the cerebellum is divisible into a number of olivo-cortico-nuclear complexes or compartments.

Zonal organization of cortico-nuclear and nucleo-cortical projections of the paramedian lobule of the cat cerebellum. 2. the C2 zone.

The cortico-nuclear (C-N) and nucleo-cortical (N-C) projections of the C2 cortical zone in pars anterior (pa) and pars posterior (pp) of the paramedian lobule (PML) in the posterior lobe of the cat cerebellum were investigated with a combined electrophysiological and neuroanatomical technique. In each experiment the mediolateral boundaries of the zone were localized on the cortical surface by recording field potentials mediated via climbing fibres and evoked in the zone by activity elicited in spino-olivocerebellar paths through percutaneous stimulation of the fore- and hindlimbs; a small (15-30 nl) injection of 1-2% WGA-HRP was then made into the zone. Distributions in the deep cerebellar nuclei were determined with light microscopy both for C-N terminal labelling due to anterograde axonal transport by Purkinje cells and for cell bodies labelled due to retrograde transport in N-C axons. The extent to which retrogradely labelled olivary neurones were confined to the part of the rostral medial accessory olive that innervates the C2 zone was estimated to provide an indication of the degree to which the injected tracer might have spread beyond the boundaries of the zone. The C-N projection from the part of the C2 zone in PML pa terminates almost exclusively (probably exclusively) in nucleus interpositus posterior (NIP) at all medio-lateral levels of the nucleus but most extensively at middle and lateral levels. At most levels the C-N termination territory forms a crescent with its outer curve following the caudal, dorsal and rostral borders of the nucleus and as a result it is mainly in the dorsal half of the nucleus. There is heavy overlap with the projection from the lobule V part of the C2 zone previously studied by us. The projection from the C2 zone in PML pp terminates entirely in NIP, but although at middle medio-lateral levels in the nucleus there is substantial overlap with the PML pa and lobule V projections, the projection territory is confined to the medial half of the nucleus. Evidence was obtained compatible with the view that throughout the C2 zone its lateral and medial parts project to different parts of NIP. In both PML pa and pp the C2 zone receives N-C projections from NIP. Most of the N-C cells concerned are in the dorsal half of NIP and the great majority lie within the corresponding C-N projection territory. However, the N-C projection to PML pa appears c. 6 times heavier than that to PML pp and the PML pa part of the zone also receives a minor additional projection from nucleus lateralis (NL). The findings are discussed in relation to the hypothesis of olivo-cortico-nuclear complexes or compartments, with particular reference to the internal organization of the C2 complex.

Numerical aspects of pontine, lateral reticular, and inferior olivary projections to two paravermal cortical zones of the cat cerebellum.

Two different olivo-cortico-nuclear zones in the cat cerebellum have been compared quantitatively as regards the numbers of cells projecting to them from within several sources of mossy fibres (MFs), namely the basal pontine nuclei (BPN), nucleus reticularis tegmenti pontis (NRTP), and the ipsilateral lateral reticular nucleus (LRN). The zones chosen were the C3 zone in lobule V of the anterior lobe and the C1 zone in pars copularis of the paramedian lobule (PMLpc), localised by recording climbing fibre-mediated potentials evoked on their surface as a result of volleys set up in their spino-olivocerebellar paths. The zones were injected with fluorescent-labelled latex microspheres and cell bodies, retrogradely labelled in the MF source nuclei and in the contralateral inferior olive, were counted and mapped. Evidence was obtained that tracer efficiency was very high in both the MF projections and the olivo-cerebellar projection and that each olivocerebellar axon may provide only one climbing fibre to the upper part of a lobule V folium but an average of nearly two to the same part of a PML folium. When the numbers of labelled cells in each MF source nucleus were expressed as a percentage of the total number of labelled pontine cells, the biggest source for lobule V was the contralateral BPN, followed by LRN, contralateral NRTP, ipsilateral BPN, and ipsilateral NRTP. For PMLpc, the order was similar except that ipsilateral BPNs exceeded contralateral NRTPs, but the dominance of contralateral BPN as a source was much greater. Cell totals were converted into projection densities (i.e., numbers of cells labelled per square millimetre of cortical sheet involved in the injection site); densities for PMLpc were found to be almost three times greater than those for lobule V for contralateral BPN but the two densities were not significantly different for ipsilateral BPN. The three other MF sources projected at higher densities to lobule V than to PML. These findings indicate that two cortical zones, both of which receive climbing fibres from the rostral part of the dorsal accessory olive and project to nucleus interpositus anterior, nevertheless differ markedly in regard to both the relative and the absolute sizes of the projections they receive from several of their most important sources of MFs.

Topographical organisation within the lateral reticular nucleus mossy fibre projection to the c1 and c2 zones in the rostral paramedian lobule of the cat cerebellum.

The organisation of the projection from the principal lateral reticular nucleus (LRN) to the electrophysiologically defined cerebellar cortical c1 and c2 zones within apical folia of the forelimb-receiving area of the rostral paramedian lobule was investigated in cats. In individual experiments, small injections of either of two retrograde tracers, wheat germ agglutinin-horseradish peroxidase or fluorescent-tagged beads, were made into one or the other of the two zones. The mossy fibre projection from the LRN was found to arise almost entirely from the ipsilateral nucleus, primarily from its magnocellular region. In the pars anterior (folia 1-3) of the paramedian lobule, the projection to the c1 zone arose from cells located throughout most of the rostrocaudal extent of the magnocellular LRN, whereas the projection to the c2 zone was from cells in the rostral half of this region. There was also a small projection from cells in the dorsolateral parvicellular LRN to the c2 zone, but there was none to the c1 zone. Double-label experiments showed that, in territories within LRN where overlap occurred, cells that target either zone were intermingled, and, at most, about 9% of cells had axons that branched to innervate both zones. In the pars posterior (folia 4-6), cells targeting the two zones arose from largely overlapping areas throughout both the magnocellular and the dorsolateral parvicellular LRN, although cells targeting the c2 zone appeared to be more restricted in distribution. In addition to these interzonal differences, it was found that the projection to the pars posterior from cells in the parvicellular LRN was stronger than that to the pars anterior, irrespective of the cortical zone injected. Overall, the present study provides evidence that there is at least some topographical organisation within the LRN mossy fibre projection to certain cerebellar cortical zones.

Micro-organization of olivocerebellar and corticonuclear connections of the paravermal cerebellum in the cat.

The olivocerebellar and corticonuclear connections of the forelimb area of the paravermal medial C3 zone were studied in the cat using a combined electrophysiological and fluorescent tracer technique. During an initial operation under barbiturate anaesthesia, lobules IV/V of the cerebellar anterior lobe were exposed and small injections of dextran amines tagged with rhodamine or fluorescein were made into areas selected from four different electrophysiologically defined parts of the zone. The inferior olive and the deep cerebellar nuclei were then scrutinized for retrogradely labelled cells and anterogradely labelled axon terminals respectively. The findings demonstrate a detailed topographical organization within the olivocerebellar projection to the medial C3 zone and provide some evidence for a topographical organization of its projection to nucleus interpositus anterior. Both projections are described at a level of resolution not previously attained in neuroanatomical studies and the results strongly support the notion of a micro-compartmentalization of cerebellar olivo-corticonuclear circuits.

A combined retrograde tracer and GABA-immunocytochemical study of the projection from nucleus interpositus posterior to the posterior lobe C2 zone of the cat cerebellum.

The extent to which the cells of origin of the cerebellar nucleocortical pathway are immunopositive for gamma-aminobutyric acid (GABA) was investigated in four cats using retrograde labelling of nucleocortical neurons in combination with immunocytochemistry. Neurons were retrogradely labelled by injection of fluorescent (coumarin)-tagged latex microspheres into the c2 zone in the rostral part of the paramedian lobule. The zone was identified electrophysiologically by the characteristics of the climbing fibre responses evoked on the cerebellar surface by percutaneous stimulation applied to the left and right forepaws in pentobarbitone-anaesthetized animals. Sections of the cerebellum containing the retrogradely labelled neurons were processed for GABA immunocytochemistry using a fluorescent (rhodamine)-tagged immunoglobulin. When viewed with epifluorescence microscopy and appropriate filter blocks the retrogradely labelled nucleocortical neurons could be visualized in the same sections as the GABA-immunopositive neurons. Almost all of a total of 254 labelled nucleocortical neurons were located in nucleus interpositus posterior, where a total of 711 GABAergic neurons were also found. None of these cells contained coumarin-tagged beads and displayed immunoreactivity for GABA (i.e. none was double-labelled). When compared by area of their cell body, the nucleocortical and GABA-immunopositive neurons appeared to form two partially overlapping populations. The mean cell area of the nucleocortical neurons was 620 +/- 233 microns2 (SD), whereas the GABA-immunopositive neurons were much smaller, with a mean cell area of 220 +/- 115 microns2. The results suggest that GABA does not play a major role in the nucleocortical pathway to the c2 zone of the rostral paramedian lobule of the cat cerebellum.

Zonal organization within the projection from the inferior olive to the rostral paramedian lobule of the cat cerebellum.

The projection from the inferior olivary nucleus to the forelimb-related regions of the c1, c2 and c3 zones within rostral folia of the paramedian lobule of the cat cerebellum was studied using a combined electrophysiological and neuroanatomical tracing technique. In each experiment, the cerebellar cortical zones were identified by their receipt of spino-olivocerebellar input evoked by percutaneous electrical stimulation of the limbs. A small (15-30 nl) injection of wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) was then made into the centre of one of the zones. The olivary regions projecting to each zone were compared with the regions within the olive that have previously been shown to project to the corresponding cortical zones within lobule V of the anterior lobe. The results show that some (but not all) of the paravermal zones in the anterior lobe are also represented in the paramedian lobule (PML). The most medial (c1) zone in rostral PML receives climbing fibre input from an area in the rostral dorsal accessory olive which overlaps partially with the area that projects to the medial half of the c1 zone in lobule V. A zone equivalent to the lateral half of the c1 zone (the cx zone) in lobule V does not appear to be present within rostral PML. A middle (c2) zone within rostral PML receives olivary input from a region within the rostral medial accessory olive that overlaps partially with the area that projects to the c2 zone in lobule V. The presence of a c3 zone within rostral PML was found to be variable between animals and it could be identified electrophysiologically in only two out of a possible nine cases. In summary, the results demonstrate that, although a number of similarities exist between the olivocerebellar projections to corresponding cortical zones in the two forelimb-receiving regions of the cat paravermal cortex, the differences in olivocerebellar connectivity between the two regions suggest that functional differences between them may also exist.

Lateral and medial sub-divisions within the olivocerebellar zones of the paravermal cortex in lobule Vb/c of the cat anterior lobe.

The olivocerebellar projection to the c1, c2 and c3 zones in the paravermal cortex of lobule Vb/c has been investigated in the cat using a combined electrophysiological/neuroanatomical tracing technique. The zonal boundaries in the paravermal cortex were located by recording, on the cerebellar surface, climbing fibre field potentials evoked in response to percutaneous stimulation of one or more paws. A small (10-30 nl) injection of WGA-HRP was then made either into the centre or into the medial or lateral geographical half of a chosen zone and the resultant distribution of retrogradely labelled cells within the contralateral inferior olive was plotted. The c1 and c3 zones were each found to consist of two mediolaterally oriented 'sub-zones' which could be distinguished by their olivocerebellar input. The medial part of the c1 zone received climbing fibre input from the rostromedial part of the dorsal accessory olive (DAO) while the lateral part of the c1 zone received climbing fibre input from middle/rostral regions of the medial accessory olive (MAO). Both medial and lateral 'sub-zones' within the c3 zone were found to receive climbing fibre input from the rostral pole of DAO but, whereas there was heavy overlap between the olivary territories projecting to the medial c1 and medial c3 subzones, olivary cells projecting to the lateral part of c3 were located more rostrally within DAO. The c2 zone was found not to be divisible into mediolaterally oriented subzones and to receive climbing fibre input from a region of MAO located rostral and somewhat lateral to the region projecting to the lateral part of the c1 zone. The sub-zonal organisation of the olivocerebellar projection to the c1, c2 and c3 zones is discussed in relation to the functional properties of the different zones.

A study of branching in the projection from the inferior olive to the x and lateral c1 zones of the cat cerebellum using a combined electrophysiological and retrograde fluorescent double-labelling technique.

The pattern of transverse branching in the olivocerebellar projection to the x zone in the vermis and the lateral c1 zone in the paravermis of the cat anterior lobe was studied using a combined electrophysiological and retrograde double-labelling tracer technique. Fluorochrome-tagged latex microspheres were well suited for this purpose. The results show that the region of olive that supplies climbing fibres to the two zones forms a continuous, rostrocaudally directed column about 2.25 mm in length, in a caudo-lateral to rostromedial part of the medial accessory olive (MAO), on average between A-P levels 12.50-10.50. This column may be divided into caudal and rostral halves that project respectively to the x and lateral c1 zones in the apical folia of lobules V/VIa. Partial overlap between these two territories occurs in an intermediate region (A-P levels 12.00-11.00) in middle MAO where olive cells that supply climbing fibres to either x or lateral c1 are intermingled with a smaller population of cells whose axons branch to provide climbing fibres to both zones. Quantitative analysis showed that, when different tracers were injected into each zone in the same animal, double-labeled cells represented only 5-7% of either single-labelled cell population within this area of overlap. It is concluded that, although some transverse branching is present within the olivocerebellar projection to the x and lateral c1 zones in the apical folia of lobule V, such branching is not extensive.

Topographical organisation within the cerebellar nucleocortical projection to the paravermal cortex of lobule Vb/c in the cat.

The projection from the intracerebellar nuclei to the paravermal (intermediate) cerebellar cortex of lobule Vb/c has been investigated in the cat using a combined electrophysiological and neuroanatomical technique. A small (10-30 nl) injection of WGA-HRP was made into one of the three paravermal zones (c1, c2 or c3) after the mediolateral boundaries of the zones had been delimited on the cerebellar surface by recording climbing fibre field potentials evoked in response to percutaneous stimulation of one or more paws. The distribution of retrogradely labelled cell bodies within the intracerebellar nuclei was compared with the distribution of terminal labelling arising from anterograde transport by cerebellar Purkinje cells. The three paravermal zones displayed marked heterogeneity in their receipt of a projection from the intracerebellar nuclei. The c1 and c3 zones received virtually no such input, although injections in either zone resulted in significant terminal labeling (which was largely restricted to nucleus interpositus anterior). By contrast, the intervening c2 zone received a much heavier nucleocortical input which arose almost exclusively from nucleus interpositus posterior (to which the zone also projected). A sparse contralateral nucleocortical input to the c2 zone was also demonstrated. This arose primarily from nucleus fastigius. It is concluded that the nucleocortical projection to the paravermal cortex of lobule Vb/c displays marked topographical specificity and some functional implications of this are discussed.

The cerebellar corticonuclear projection from lobule Vb/c of the cat anterior lobe: a combined electrophysiological and autoradiographic study. I. Projections from the intermediate region.

The present study examines the projection to the cerebellar nuclei of Purkinje cells in particular sagittal zones within the intermediate region of the cerebellar cortex. The boundaries between the zones were delimited electrophysiologically on the basis of their climbing fibre input so that a small volume (10-120 nl) of 3H-leucine could be injected into the centre of a chosen zone. The subsequent uptake and orthograde transport of labelled material by the Purkinje cells was studied autoradiographically. It was found that the smallest injections resulted in injection sites restricted to a single cortical zone and extremely reproducible results could be obtained using such a combined electrophysiological/autoradiographic technique. Larger injections sometimes spread to a neighbouring zone but the resultant terminal labelling within the deep nuclei was invariably consistent with the results obtained from smaller injections. The c1 and c3 olivocerebellar zones, which are known to receive climbing fibre input transmitted from the ipsilateral forelimb via a dorsal funiculus spino-olivo-cerebellar pathway (DF-SOCP), were found to project to partially overlapping regions within nucleus interpositus anterior (NIA). No projection to nucleus interpositus posterior (NIP) was demonstrated for either zone. No distinction could be seen between the terminal fields for the medial and lateral halves of the c1 zone which are, however, known to receive their climbing fibre input from quite separate regions within the inferior olive. The c2 zone, which was delimited on the basis of its climbing fibre input which is transmitted from both forelimbs via a lateral funiculus SOCP, was found to project exclusively to interpositus posterior. The hemispheral d1 zone was found to project to the transitional region where interpositus anterior and the dentate nucleus adjoin.

The cerebellar corticonuclear projection from lobule Vb/c of the cat anterior lobe: a combined electrophysiological and autoradiographic study. II. Projections from the vermis.

The present study is an investigation of the efferent pathways from Purkinje cells within particular sagittal zones of the vermal region of the cat cerebellar cortex. A combined electrophysiological/autoradiographic technique was used, in which a small volume (10-120 nl) of 3H-leucine was injected into the centre of a chosen cortical zone after the mediolateral extent of the zone had been delimited electrophysiologically on the basis of its climbing fibre input. Study of the uptake and orthograde transport of labelled material by the Purkinje cells showed that the smallest injections gave rise to injection sites which were restricted to a single zone and to terminal labelling which was very reproducible between cases. Larger injections usually resulted in spread of labelled material to neighbouring zones but the resultant distribution of terminal labelling was nevertheless consistent with that arising from smaller injections. The x zone, which receives climbing fibre input transmitted from the ipsilateral forelimb via a dorsal funiculus spino-olivo-cerebellar pathway (DF-SOCP), was found to project to the junctional region between nucleus fastigius and nucleus interpositus posterior (NIP). The b zone, which lies laterally in the vermis and receives climbing fibre input transmitted from both forelimbs (and both hindlimbs) via a slower conducting SOCP, was found to project, not to the cerebellar nuclei proper, but to the ipsilateral lateral vestibular nucleus. The projection of the third zone within the vermis, the a zone, was not examined but it is generally agreed that this zone projects mainly to nucleus fastigius.

Cranio-facial and dental anomalies in the Branchio-Skeleto-Genital (BSG) syndrome with suggestions for more appropriate nomenclature.

A Syndrome combining developmental, facial, skeletal, dental and genital abnormalities previously reported as the Branchio-Skeleto-Genital (BSG) Syndrome is discussed and the dental anomalies described more fully. The dentine dysplasia does not fit into the Shield's classification type I or II. The prefix Branchio- is misleading and suggestion is made of a more appropriate nomenclature.

Inhibition of gamma motoneurone discharge by contraction of the homonymous muscle in the decerebrated cat.

1. The aim of this study has been to determine the autogenetic reflex effects of tendon organ stimulation upon gamma motoneurones in the decerebrated cat. 2. Tendon organs serving a muscle were excited by isometric twitch contractions of some motor units of that muscle. Contractions were elicited by electrical stimulation of the cut peripheral end of part of the ventral root supply, using a stimulus strength at or below maximum for alpha motoneurone axons. Afferent recordings in the same cats as were used to study reflexes of gamma motoneurones showed that tendon organs were powerfully excited during twitch contractions of their muscle. Early discharges were also elicited in both tendon organs and spindle primary afferents. 3. Background discharges of forty-seven triceps surae gamma motoneurones, ranging in axonal conduction velocity from 17 to 40 m/sec, were recorded from filaments of the muscle nerve. The initial response of twenty-two (47%) neurones to twitches of the triceps surae was inhibition of their discharge. The latency from time of stimulation of the ventral root ranged from 10 to 22 msec. The lowered probability of firing lasted an average of 25 msec and, occasionally, was seen as a short silent period. 4. The inhibition was reduced in duration by decreasing the resting muscle length so that less active tension was developed during contraction. 5. The inhibition was observed, in one instance, in the spinally transected decerebrated cat. 6. We argue the case that early discharges in tendon organ afferents give rise to the onset of inhibition and that tension dependent discharges of tendon organs contribute further inhibition of gamma motoneurones. 7. Sixteen gamma motoneurones were not affected by contraction but seventeen showed a period of facilitation. The facilitation could occur after a period of inhibition (eight neurones) or as the sole response to contraction. In either case facilitation occurred mainly during relaxation of the muscle and may, in part, be attributable to increased spindle primary ending firing at this time. 8. In discussion a comparision is made of the reflex effects of muscle afferent discharges on alpha and gamma motoneurones.

Autogenetic reflex action on to gamma motoneurones by stretch of triceps surae in the decerebrated cat.

1. Tonically firing gamma motoneurones of known conduction velocity (total eighty-seven, range 15-43 m/sec) have been isolated in peripheral muscular nerves to triceps surae. Their responses to stretch of triceps surae have been studied in decerebrated cats. A small amplitude, quick stretch and release was used to provide a selective stimulus for primary endings of muscle spindles. 2. To check the selectivity, recordings were made from 135 afferents from triceps surae under conditions closely similar to the reflex experiments. The threshold of all but a few primary endings of muscle spindles law below 50 micrometer whereas threshold was above 50 micrometer for the majority of secondary endings and tendon organs. A 20 micrometer stretch excited approximately half the primary endings but only one of thirty-six secondaries and no tendon organs responded to such a small stretch. Nine group III afferents were also studied but none responded to stretch. 3. Stretch of up to 50 micrometer excited twenty-three and inhibited eleven gamma motoneurones while thirty-three remained unaffected. A further twenty showed mixed responses, being inhibited initially before being excited at longer latency. Thresholds for reflex responses of gamma motoneurones frequently occurred below 20 mum and responses were close to maximal for stretch of 50 micrometer. 4. Excitation always had a lower threshold to stretch than did inhibition for those gamma motoneurones showing mixed responses and was the more potent of the two effects. 5. Excitation to stretch had central delays, to the incoming group Ia volley, ranging from 5 to 14 msec while similarly calculated delays for excitation of alpha motoneurones ranged from 0.6 to 3.0 msec. Central delays of the gamma inhibitory responses lay in an intermediate range of 1.7-7.0 msec. 6. The long central delays of excitation of gamma motoneurones in response to stretch do not reflect transmission in supraspinal pathways since the reflex persisted following spinal section. 7. Excitation of gamma motoneurones was weak in comparison with that of tonically firing alpha motoneurones recorded in the same preparations and it was always necessary to sum a number of responses in order to reveal an effect...