Response properties of dorsolateral pontine units during smooth pursuit in the rhesus macaque

Abstract

1. The anatomical connections of the dorsolateral pontine nucleus (DLPN) implicate it in the production of smooth-pursuit eye movements. It receives inputs from cortical structures believed to be involved in visual motion processing (middle temporal cortex) or motion execution (posterior parietal cortex) and projects to the flocculus of the cerebellum, which is involved in smooth pursuit. To determine the role of the DLPN in smooth pursuit, we have studied the discharge patterns of 191 DLPN neurons in five monkeys trained to make smooth-pursuit eye movements of a spot moving either across a patterned background or in darkness. 2. Four unit types could be distinguished. Visual units (15%) discharged in response to movement of a large textured pattern, often in a direction-selective fashion but not during smooth pursuit of a spot in the dark. Eye movement neurons (31%) discharged during sinusoidal smooth pursuit in the dark with peak discharge rate either at peak eye position or peak eye velocity, but they showed no response during background movement or during other visual stimulation. These units continued to discharge when the target was extinguished (blanked) briefly, and the monkey continued to make smooth eye movements in the dark. The majority (54%) of our DLPN units discharged during both smooth pursuit in the dark and background movement while the monkey fixated. Blanking the target during smooth pursuit revealed that these units fell into two distinct classes. Visual pursuit units ceased discharging during a blank, suggesting that they had only a visual sensitivity. Pursuit and visual units continued to discharge during the blank, indicating that they had a combined oculomotor and visual sensitivity. 3. Ninety-five percent of the units that discharged during smooth pursuit were direction selective. These units had rather broad directional tuning curves with widths at half height ranging from 65 to 180 degrees. Many preferred directions for DLPN units were observed, although the vertical and near-vertical directions predominated. 4. Most units that responded to large-field background movement were direction selective. During sinusoidal movement of a large-field background, half of them also discharged in relation to stimulus velocity, whereas others did not.

Role of the Dorsolateral Pontine Nucleus in Short-Term Adaptation of the Horizontal Vestibuloocular Reflex

“…We first located the DLPN by its stereotaxic location relative to the oculomotor nucleus and by finding neurons that were modulated for motion of either a large-field (75 ϫ 75°) stimulus or during smoothpursuit of a small diameter (0.2°) target spot moving (Ϯ10°; 0.1-0.75 Hz) over a dark background (May et al 1988;Mustari et al 1988). In muscimol injection experiments, we used a small-diameter (Ͻ50 m) micropipette whose tip was positioned at the depth where smoothpursuit-related neurons were recorded.…”

“…DLPN injection sites were confirmed histologically using standard methods for Nissl staining as described in our earlier studies (Distler et al 2002;Mustari et al 1988Mustari et al , 1994Mustari et al , 2001.…”

“…In turn, the DLPN sends mossy fiber projections to the contralateral ventral paraflocculus and dorsal paraflocculus (Glickstein et al 1994;Nagao 1997) and vermal lobule VI and VII (Brodal 1979(Brodal , 1982Langer 1985). Single-unit recording (Kawano et al 1992;Mustari et al 1988;Suzuki and Keller 1984;Suzuki et al 1990;Thier et al 1988) and lesion studies (May et al 1988) demonstrate that DLPN neurons carry appropriate signals to play a role in the initiation and maintenance of smooth pursuit, optokinetic and ocular following eye movements. However, it is unknown whether the DLPN, which provides retinal image motion (slip) signals to the vestibulocerebellum, could also play a role in visual-vestibular behavior.…”

Neural dynamics of saccadic and smooth pursuit eye movement coordination during visual tracking of unpredictably moving targets

“…) LIP to SC, SC to LIP Saccadic target priming information (Lynch, Graybiel, & Lobeck, 1985) FEF to PPRF Motor Command for saccade generation (Huerta et al, 1987;Leichnetz, Smith, & Spencer, 1984 (Tusa & Ungerleider, 1988) MST to DLPN Target and background speed and direction input is projected (Glickstein et al, 1980;Mustari et al, 1988;Ono et al, 2004;Suzuki & Keller, 1984) MST to FPA Direction and speed sensitive of target data (Churchland & Lisberger, 2005;Maioli et al, 1992;Tian & Lynch, 1997; J. R. Tian & Lynch, 1996aTusa & Ungerleider, 1988) FPA to rNRTP Direction sensitive target input reach eye acceleration cells in rNRTP. (Suzuki et al, 1999;Suzuki et al, 2003;T.…”

“…(Suzuki et al, 1999;Suzuki et al, 2003;T. Yamada et al, 1996) DLPN to CBM (Mustari et al, 1988;Ono et al, 2005;Ono et al, 2004) DLPN to Vermis (Thielert & Thier, 1993;J. Yamada & Noda, 1987) DLPN to VPF Target and background speed and direction input is transferred.…”