Anatomical findings are presented that identify cortical and subcortical sources of afferents to the nucleus reticularis tegmenti pontis (NRTP) and basal pontine nuclei. Projections from the middle temporal visual area (MT), medial superior temporal visual area (MST), lateral intraparietal area (LIP), and areas 7a and 7b to the basal pontine nuclei were studied using 3H-leucine autoradiography. The results complemented a parallel study of retrograde neuronal labeling attributable to injecting WGA-HRP into NRTP and neighboring pontine nuclei. Small 3H-leucine injections confined to MT, MST, LIP, area 7a, or area 7b, produced multiple patches of pontine terminal label distributed as follows: (1) An injection within MT produced terminal label limited to the dorsolateral and lateral pontine nuclei. (2) Injections restricted to MST or LIP showed patches of terminal label in the dorsal, dorsolateral, lateral, and peduncular pontine nuclei. (3) Area 7a targets the dorsal, dorsolateral, lateral, peduncular, and ventral pontine nuclei, whereas area 7b projects, additionally, to the dorsomedial and paramedian pontine nuclei. Notably, no projections were seen to NRTP from any of these cortical areas. In contrast, injections made by other investigators into cortical areas anterior to the central sulcus revealed cerebrocortical afferents to NRTP, in addition to nuclei of the basal pontine gray. With our pontine WGA-HRP injections, retrograde neuronal labeling was observed over a large extent of the frontal cortex continuing onto the medial surface which included the lining of the cingulate sulcus and cingulate gyrus. Significant subcortical sources for afferents to the NRTP and basal pontine nuclei were the zona incerta, ventral mesencephalic tegmentum, dorsomedial hypothalamic area, rostral interstitial nucleus of the medial longitudinal fasciculus, red nucleus, and subthalamic nucleus. The combined anterograde and retrograde labeling data indicated that visuo-motor cortico-pontine pathways arising from parietal cortices target only the basal pontine gray, whereas the NRTP, together with select pontine nuclei, is a recipient of afferents from frontal cortical areas. The present findings implicate the existence of parallel direct and indirect cortico-pontine pathways from frontal motor-related cortices to NRTP and neighboring pontine nuclei.

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Suzuki DA, Betelak KF, Yee RD. Gaze pursuit responses in nucleus reticularis tegmenti pontis of head-unrestrained macaques. J Neurophysiol 101: 460 -473, 2009. First published November 5, 2008 doi:10.1152/jn.00615.2007. Eye-head gaze pursuit-related activity was recorded in rostral portions of the nucleus reticularis tegmenti pontis (rNRTP) in alert macaques. The head was unrestrained in the horizontal plane, and macaques were trained to pursue a moving target either with their head, with the eyes stationary in the orbits, or with their eyes, with their head voluntarily held stationary in space. Head-pursuit-related modulations in rNRTP activity were observed with some cells exhibiting increases in firing rate with increases in head-pursuit frequency. For many units, this head-pursuit response appeared to saturate at higher frequencies (Ͼ0.6 Hz). The response phase re:peak head-pursuit velocity formed a continuum, containing cells that could encode head-pursuit velocity and those encoding head-pursuit acceleration. The latter cells did not exhibit head position-related activity. Sensitivities were calculated with respect to peak head-pursuit velocity and averaged 1.8 spikes/s/deg/s. Of the cells that were tested for both head-and eye-pursuit-related activity, 86% exhibited responses to both head-and eye-pursuit and therefore carried a putative gaze-pursuit signal. For these gaze-pursuit units, the ratio of head to eye response sensitivities averaged ϳ1.4. Pursuit eccentricity seemed to affect head-pursuit response amplitude even in the absence of a head position response per se. The results indicated that rNRTP is a strong candidate for the source of an active headpursuit signal that projects to the cerebellum, specifically to the target-velocity and gaze-velocity Purkinje cells that have been observed in vermal lobules VI and VII. I N T R O D U C T I O NProper visual function is dependent on the accurate pointing of the fovea toward visual objects of interest. Rotations of the eyeball are the common means of accomplishing this foveation. However, head movements often accompany eye movements when large gaze shifts are required as we navigate our visual environment. Although much is known about the neuronal mechanisms involved with rotating the eyeball, less is known about the control of head movements.The numerous motor-related inputs to the nucleus reticularis tegmenti pontis (NRTP) together with functions known to date indicate that NRTP could be involved with the coordinated control of eye-and-head motor behavior. Projections to NRTP include inputs from the frontal and supplementary eye fields and the premotor and motor cortices (Brodal 1980a;Giolli et al. 2001;Hartmann-von Monakow et al. 1981;Huerta et al. 1986; Künzle and Akert 1977;Leichnetz 1986;Leichnetz et al. 1984; Shook et al. 1990;Stanton et al. 1988). Both the frontal eye field and NRTP have been shown to be involved with the control of smooth pursuit eye movements (Gottlieb et al. 1993(Gottlieb et al. , 1994Keating 1991;Lynch 1987;MacAvoy 1991;Ono...