Connections of the medial posterior parietal cortex (area 7m) in the monkey.

The afferent and efferent cortical and subcortical connections of the medial posterior parietal cortex (area 7m) were studied in cebus (Cebus apella) and macaque (Macaca fascicularis) monkeys using the retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique. The principal intraparietal corticocortical connections of area 7m in both cebus and macaque cases were with the ipsilateral medial bank of the intraparietal sulcus (MIP) and adjacent superior parietal lobule (area 5), inferior parietal lobule (area 7a), lateral bank of the IPS (area 7ip), caudal parietal operculum (PGop), dorsal bank of the caudal superior temporal sulcus (visual area MST), and medial prestriate cortex (including visual area PO and caudal medial lobule). Its principal frontal corticocortical connections were with the prefrontal cortex in the shoulder above the principal sulcus and the cortex in the shoulder above the superior ramus of the arcuate sulcus (SAS), the area purported to contain the smooth eye movement-related frontal eye field (FEFsem) in the cebus monkey by other investigators.

Prearcuate cortex in the Cebus monkey has cortical and subcortical connections like the macaque frontal eye field and projects to fastigial-recipient oculomotor-related brainstem nuclei.

The cortical and subcortical connections of the prearcuate cortex were studied in capuchin monkeys (Cebus apella, albifrons) using the anterograde and retrograde transport capabilities of the horseradish peroxidase technique. The findings demonstrate remarkable similarities to those of the macaque frontal eye field and strongly support their homology. The report then focuses on specific prearcuate projections to oculomotor-related brainstem nuclei that were shown in a companion experiment to entertain connections with the caudal oculomotor portion of the cerebellar fastigial nucleus.

Respiratory failure without pulmonary edema following injection of a glutamate agonist into the ventral medullary raphe of the rat.

Injection of ibotenic acid (IA), a glutamate agonist, into the ventral medullary raphe (VMR; especially the nucleus raphe magnus) of the rat produced respiratory failure and death following a predictable course of events. The response to the IA injection was characterized initially by increased respiratory frequency and was followed by pulmonary arterial hypertension, systemic arterial hypoxemia, acidosis, and hypothermia. Within 90 min apnea occurred as a terminal event in all animals.

Connections of the caudal cerebellar interpositus complex in a new world monkey (Cebus apella).

The afferent and efferent connections of the cerebellar interpositus complex were studied in a capuchin monkey (Cebus apella) that had received a transcannular horseradish peroxidase implant into the caudal portion of the anterior interpositus nucleus and posterior interpositus nucleus. While the heaviest anterogradely labeled ascending projections were observed to the contralateral ventral posterolateral nucleus of the thalamus, pars oralis (VPLo), efferent projections were also observed to the contralateral ventrolateral thalamic nucleus (VLc) and central lateral (CL) nucleus of the thalamic intralaminar complex, magnocellular (and to a lesser extent parvicellular) red nucleus, nucleus of Darkschewitsch, zona incerta, nucleus of the posterior commissure, lateral intermediate layer and deep layer of the superior colliculus, dorsolateral periaqueductal gray, contralateral nucleus reticularis tegmenti pontis and basilar pontine nuclei (especially dorsal and peduncular), and dorsal (DAO) and medial (MAO) accessory olivary nuclei, ipsilateral lateral (external) cuneate nucleus (LCN) and lateral reticular nucleus (LRN), and to a lesser extent the caudal medial vestibular nucleus (MVN) and caudal nucleus prepositus hypoglossi (NPH), and dorsal medullary raphe. The heaviest retrograde labeling was corticonuclear Purkinje cells in the paramedian cerebellar cortex lateral to the vermis of lobules IV-VIII.

Preoccipital cortex receives a differential input from the frontal eye field and projects to the pretectal olivary nucleus and other visuomotor-related structures in the rhesus monkey.

The bidirectional axonal transport capabilities of the horseradish peroxidase (HRP) technique facilitated the study of the frontal-eye-field (FEF) input and pretectal output of two regions of extrastriate preoccipital cortex (POC). Following horseradish peroxidase (HRP) gel implants into the middle and dorsal POC in two rhesus monkeys, the middle POC implant demonstrated retrograde frontal cortical labeling largely restricted to the inferior frontal eye field (iFEF) and adjacent inferior prefrontal convexity, whereas the dorsal POC implant showed labeling in the caudal ventral bank of the superior ramus of the arcuate sulcus (sas) and middle-to-dorsal region of the rostral bank of the concavity of the arcuate sulcus (dorsal FEF). Prominent anterogradely labeled efferent preoccipital projections were observed to the ipsilateral pretectal olivary nucleus (PON) and to a lesser extent the anterior pretectal nucleus.

Projections of the medial cerebellar nucleus to oculomotor-related midbrain areas in the rat: an anterograde and retrograde HRP study.

The mesencephalic projections of the medial cerebellar nucleus (MCN) were studied in the rat by using the method of anterograde transport of wheat germ agglutinin/horseradish peroxidase to establish connections of the nucleus with oculomotor-related nuclei as a basis for its proposed role in eye movement. The principal targets of projections were the supraoculomotor ventral periaqueductal gray (PAG) and lateral PAG, and paraoculomotor cell groups (nucleus of Darkschewitsch and medial accessory nucleus of Bechterew). Lesser projections were observed to the intermediate layer of the superior colliculus, nucleus of the posterior commissure, and prerubral field.

Afferents of the caudal fastigial nucleus in a New World monkey (Cebus apella).

The afferents of the fastigial nucleus (FN) were studied in two capuchin monkeys (Cebus apella) one of which had received a unilateral injection of horseradish peroxidase in the caudal FN, and a second monkey which received a control injection that involved the lateral caudal FN but extended into the cerebellar white matter between the FN and posterior interposed nucleus (PIN). All of the sources of FN afferents were found to be labeled bilaterally. In addition to the restricted distribution of labeled Purkinje cells in lobules VI and VII of the posterior lobe vermis ("oculomotor vermis"), retrogradely labeled cells were present in the dorsolateral pontine nucleus (DLPN), dorsomedial pontine nucleus (DMPN), nucleus reticularis tegmenti pontis (NRTP), pontine raphe (PR), paramedian nucleus reticularis pontis caudalis (NRPC), nucleus prepositus hypoglossi (NPH), subnucleus b of the medial accessory olivary nucleus (sbMAO), and vestibular complex (VC).

Inferior frontal eye field projections to the pursuit-related dorsolateral pontine nucleus and middle temporal area (MT) in the monkey.

Inferior frontal eye field (FEF) projections to the dorsolateral pontine nucleus (DLPN), and corticocortical connections with the superior temporal sulcal (STS) cortex, were studied in five macaque monkeys which had received horseradish peroxidase (HRP) gel implants into the inferior prearcuate cortex (including area 45 of Walker, 1940). These connections were contrasted with those from the dorsal FEF (area 8a) in another macaque monkey. Findings of heavy inferior FEF projections to the ipsilateral DLPN (light to the contralateral DLPN) and reciprocal connections with the deep caudal bank and fundus of the superior temporal sulcus (STS), presumed to be the middle temporal (MT) visual area (Maunsell & Van Essen, 1983a), appeared to go hand in hand with more pronounced projections to the stratum superficialis of the superior colliculus (SC).

Afferent and efferent connections of the cholinoceptive medial pontine reticular formation (region of the ventral tegmental nucleus) in the cat.

Following minor concussive brain injury when there is an otherwise general suppression of CNS activity, the ventral tegmental nucleus of Gudden (VTN) demonstrates increased functional activity (32). Electrical or pharmacological activation of a cholinoceptive region in this same general area of the medial pontine tegmentum contributes to certain components of reversible traumatic unconsciousness, including postural atonia (31, 32, 45). Therefore, in an effort to examine the neuroanatomical basis of the behavioral suppression associated with a reversible traumatic unconsciousness, the afferent and efferent connections of the VTN and putative cholinoceptive medial pontine reticular formation (cmPRF) were studied in the cat using the retrograde horseradish peroxidase (HRP), HRP/choline acetyltransferase (ChAT) double-labeling immunohistochemistry, and anterograde HRP and autoradiographic techniques.

Origin of cerebellar projections to the region of the oculomotor complex, medial pontine reticular formation, and superior colliculus in New World monkeys: a retrograde horseradish peroxidase study.

Cerebellar projections to oculomotor-related brainstem regions were studied in four groups of New World (capuchin, squirrel) monkeys by using the retrograde transport of horseradish peroxidase (HRP) to determine the origin of the principal cerebellar influence on eye movement. Group A monkeys had HRP injections or transcannular HRP gel implants into the oculomotor complex (OMC), the largest of which involved adjacent paraoculomotor nuclei (e.g.

Higher centers concerned with eye movement and visual attention: cerebral cortex and thalamus.

A comparison of the connectivity and physiology of the frontal and parietal eye fields, showing a closer relationship between the frontal eye fields and oculomotor processing than for the parietal region. The involvement of thalamic regions in the generation of eye movements is also reviewed.

The origin of brainstem afferents of the paramedian pontine reticular formation in the cat.

Transcannular microinjections of horseradish peroxidase (HRP) were made into the paramedian pontine reticular formation (PPRF) in adult cats to determine the origin of the principal sources of inputs to this important preoculomotor center for the production of saccadic eye movements. Retrogradely labeled cells were observed in numerous oculomotor-related structures, including the prerubral field (rostral interstitial nucleus of the medial longitudinal fasciculus), nucleus of Darkschewitsch, nucleus of the posterior commissure, deep superior colliculus, supraoculomotor ventral periaqueductal gray, contralateral paramedian pontine reticular formation, pontine raphe and dorsal medial pontine tegmentum medial to the abducens nucleus (purported to contain omnipause neurons), cell group Y, and the perihypoglossal complex (nucleus prepositus hypoglossi). Other sources of afferents to the region included the zona incerta, lateral and medial habenular nuclei, medial hypothalamus, medial mammillary nucleus, nucleus cuneiformis, medial medullary reticular formation, and the medial and lateral cerebellar nuclei.

Frontal projections to the region of the oculomotor complex in the rat: a retrograde and anterograde HRP study.

The retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique were employed to study frontal projections to the perioculomotor region in the rat. Following HRP microinjections or transcannular HRP gel implants into the oculomotor complex (OMC), the majority of retrogradely labeled pyramidal cells were located in lamina V of the dorsomedial frontal shoulder cortex, i.e.

The frontal eye field and prefrontal cortex project to the paramedian pontine reticular formation in the cat.

Transcannular microinjections of horseradish peroxidase were made into the paramedian pontine reticular formation (PPRF) in adult cats to identify regions of the cerebral cortex having direct influence on this important center for the production of saccadic eye movements. The majority of retrogradely labeled cortico-(ponto)reticular neurons were located in lamina V of the dorsomedial precruciate shoulder cortex and presylvian sulcal cortex, the medial and lateral frontal eye fields of the cat respectively. In most cases, labeled cells also extended into the gyrus proreus, the cat prefrontal cortex.

Collateralization of cerebellar efferent projections to the paraoculomotor region, superior colliculus, and medial pontine reticular formation in the rat: a fluorescent double-labeling study.

Collateralization of cerebellar efferent projections to the oculomotor region, superior colliculus (SC), and medial pontine reticular formation (mPRF) was studied in rats using fluorescent tracer substances. In one group, True Blue (TB) was injected into the oculomotor complex (OMC), including certain paraoculomotor nuclei and supraoculomotor ventral periaqueductal gray (PAG), and Diamidino Yellow (DY) was injected into the medial pontine reticular formation (mPRF) or pontine raphe. The largest number of single-TB-labeled (paraoculomotor-projecting) cells was observed in the medial cerebellar nucleus (MCN) and posterior interposed nucleus (PIN), whereas the largest number of single-DY-labeled (mPRF-projecting) cells was in the MCN.

Collateralization of frontal eye field (medial precentral/anterior cingulate) neurons projecting to the paraoculomotor region, superior colliculus, and medial pontine reticular formation in the rat: a fluorescent double-labeling study.

Paired injections of fluorescent tracers (True Blue, Diamidino-Yellow) were made into the oculomotor complex (OMC) and medial pontine reticular formation (mPRF), and superior colliculus (SC) and mPRF, in adult rats to retrogradely label the cortical cells of origin of projections to these oculomotor-related brainstem structures. While large numbers of single-labeled cells in the medial frontal cortex projected only to the mPRF, the presence of many double-labeled cells in the dorsomedial shoulder cortex (medial precentral/anterior cingulate areas), the rat frontal eye field (FEF), indicated that this cortical region contains lamina V pyramid neurons whose axons collateralize to project to the region of the OMC, SC, and mPRF. The similarities of rat and monkey FEF connections, and their relevance to the control of eye movement, are discussed.

Afferent and efferent connections of the dorsolateral precentral gyrus (area 4, hand/arm region) in the macaque monkey, with comparisons to area 8.

The afferent and efferent connections of the dorsolateral precentral gyrus, the primary motor cortex for control of the upper extremity, were studied by using the retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique in three adult macaque monkeys that had received HRP gel implants in this cortical region. Reciprocal corticocortical connections were observed primarily with the supplementary motor area (SMA) in medial premotor area 6 and dorsal bank of the cingulate sulcus, postarcuate area 6 cortex, dorsal cingulate cortex (area 24), superior parietal lobule (area 5, PE/PEa), and inferior parietal lobule (area 7b, PF/PFop, including the secondary somatosensory SII region). In these heavily labeled regions, the associational intrahemispheric afferents originated primarily from small and medium sized pyramidal cells in layer III, but also from layer V.

The frontal eye field projects to the nucleus prepositus hypoglossi in the monkey.

Following horseradish peroxidase gel implants in prearcuate cortex involving the frontal eye field (area 8) in Old and New World monkeys, bilateral anterograde labelling was observed in the nucleus prepositus hypoglossi, an important preoculomotor nucleus.

Cortical projections to the paramedian tegmental and basilar pons in the monkey.

The efferent connections of the cerebral cortex to paramedial tegmental and basilar pons were studied in the monkey by using the retrograde and orthograde capabilities of the horseradish peroxidase (HRP) technique. Six capuchin monkeys (Cebus apella) received transcannular pontine HRP gel implants to retrogradely label the cells of origin of corticopontine projections. Four additional capuchin monkeys, one rhesus (Macaca mulatta), and one cynomolgus (Macaca fascicularis) monkey, received HRP gel implants in premotor (area 6), frontal eye field (FEF, area 8), superior (area 5), and inferior (area 7) parietal lobules to orthogradely label the course and termination of corticopontine projections, and thus to confirm the retrograde studies.

Cortical projections to nuclei adjacent to the oculomotor complex in the medial dien-mesencephalic tegmentum in the monkey.

Cortical projections to cell groups surrounding the oculomotor complex were studied by using the retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique in old and new world monkeys. Fluid HRP injections or transcannular solid polyacrylamide HRP gel implants were made into the oculomotor nucleus (OMN) and adjacent nuclei to label retrogradely corticofugal neurons that project to this region, and cortical HRP gel implants were made in various areas of the frontal lobe to label anterogradely the trajectories and terminations of cortico-paraoculomotor projections and thus to confirm the retrograde findings. Projections to the paraoculomotor cell groups in the medial dien-mesencephalic tegmentum originate almost exclusively from the frontal lobe.

Paralemniscal reticular formation: response of cells to a noxious stimulus.

Extracellular single unit recordings were made in the paralemniscal reticular formation in adult male rats. A majority of the cells studied were characterized as nociceptive because a noxious stimulus evoked a change (either an increase or decrease) in their spontaneous firing rates. Norepinephrine (NE) administered microiontophoretically usually mimicked the response to the noxious stimulus (foot pinch).

Supramedullary afferents of the nucleus raphe magnus in the rat: a study using the transcannula HRP gel and autoradiographic techniques.

Afferents of the nucleus raphe magnus (NRM) were retrogradely labelled by using a transcannula HRP gel technique in conjunction with tetramethylbenzidine neurohistochemistry to determine the sources of inputs to the nucleus which could potentially influence the descending antiociceptive raphe-spinal system. Large numbers of HRP-labelled neurons were seen in the frontal cortex, dorsomedial nucleus of the hypothalamus, zona incerta, nucleus parafascicularis prerubralis (NPfPr), pretectum, dorsal and lateral periaqueductal gray, nucleus cuneiformis (NC), deep superior colliculus (dSC), a paraoculomotor cell group which may be the medial accessory nucleus of Bechterew, dorsal column nuclei, and spinal trigeminal nucleus. Smaller numbers of labelled cells were also observed in the preoptic area, nucleus of Darkschewitsch, ventral peri(third)ventricular gray, nucleus reticularis pontis oralis and caudalis, medial and lateral vestibular nuclei, and a subdivision of the hypoglossal nucleus.

The medial accessory nucleus of Bechterew: a cell group within the anatomical limits of the rostral oculomotor complex receives a direct prefrontal projection in the monkey.

The medial accessory nucleus of Bechterew, a vertically oriented cell group in the rostral lateral oculomotor nucleus (OMN), contiguous dorsally with the nucleus of Darkschewitsch (ND) and ventrally with the parvocellular red nucleus, is separated from the interstitial nucleus of Cajal (IC) by a small paraoculomotor fascicle (POF) that forms the anatomical limits of the OMN. Horseradish peroxidase (HRP) gel implants in the prearcuate frontal cortex dorsal to the caudal third of the principal sulcus in the monkey resulted in an anterogradely labeled bilateral projection to this paraoculomotor cell group. The functional role of this largely overlooked nucleus is yet to be determined.

Projections from the nucleus parafascicularis prerubralis to medullary raphe nuclei and inferior olive in the rat: a horseradish peroxidase and autoradiography study.

Horseradish peroxidase gel implants into either the nucleus raphe magnus (NRM) or inferior olive (IO) led to large numbers of retrogradely labeled cells in the prerubral subthalamic region in a cell group that surrounds the fasciculus retroflexus, which we suggest should be referred to as the nucleus parafascicularis prerubralis (nPfPr) to avoid the confusion of previous terminology. Autoradiographic studies, following injections of tritiated leucine into the nPfPr, confirmed projections to both medullary raphe nuclei (MRN) and IO. This common prerubral projection to IO, a well-established precerebellar nucleus, and MRN, again raises the question of whether the latter are involved in brainstem-mediated reflexes in addition to their well documented role in analgesic mechanisms.

Connections between the frontal eye field and pretectum in the monkey: an anterograde/retrograde study using HRP gel and TMB neurohistochemistry.

Horseradish peroxidase (HRP) gel implants in the frontal eye field (FEF) of macaque monkeys, processed with tetramethylbenzidine (TMB) neurohistochemistry and studied with darkfield microscopy, demonstrated bidirectional HRP labeling of the afferents and efferents of this cortical area. It was evident that among the entire scope of its inputs, the FEF received a prominent afferent projection from the nucleus of the optic tract (NOT, nucleus limitans) and the suprageniculate nucleus, and projected to a medial subdivision of NOT, sublentiform nucleus, nucleus of the pretectal area, nucleus of the posterior commissure, and the rostral periaqueductal gray. The direct afferent projections to FEF from NOT could provide a route for visual input to reach FEF via the pretectum without first going to the visual cortex.