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

Abstract

Ono, Seiji, V. E. Das, and M. J. Mustari. Role of the dorsolateral pontine nucleus in short-term adaptation of the horizontal vestibuloocular reflex. J Neurophysiol 89: 2879 -2885, 2003; 10.1152/jn.00602.2002. The dorsolateral pontine nucleus (DLPN) is a major component of the cortico-ponto-cerebellar pathway that carries signals essential for smooth pursuit. This pathway also carries visual signals that could play a role in visually guided motor learning in the vestibular ocular reflex (VOR). However, there have been no previous studies that tested this possibility directly. The aim of this study was to determine the potential role of the DLPN in short-term VOR gain adaptation produced by viewing a scene through lenses placed in front of both eyes. In control experiments, adaptation of VOR gain was achieved by sinusoidal rotation (0.2 Hz, 30°/s) for 2 h while the monkey viewed a stationary visual surround through either magnifying (ϫ2) or minifying (ϫ0.5) lenses. This led to increases (23-32%) or decreases (22-48%) of VOR gain as measured in complete darkness (VORd). We used injections of muscimol, a potent GABA A agonist (0.5 l; 2%), to reversibly inactivate the DLPN, unilaterally, in three monkeys. After DLPN inactivation, initial acceleration of ipsilateral smoothpursuit was reduced by 35-68%, and steady-state gain was reduced by 32-61%. Despite these significant deficits (P Ͻ 0.01) in ipsilesional smooth pursuit, the VOR during lens viewing was similar to that measured in preinjection control experiments. Similarly, after 2 h of adaptation, VORd gain was not significantly different (P Ͼ 0.61) from control adaptation values for either ipsi-or contralesional directions of head rotation. This was the case even though a stable ipsilesional smooth pursuit deficit persisted throughout the full adaptation period. Our results suggest that visual error signals for short-term adaptation of the VOR are derived from sources other than the DLPN perhaps including other basilar pontine nuclei and the accessory optic system.

Cerebellar Motor Learning: When Is Cortical Plasticity Not Enough?

“…However, detailed measurement and modelling of both tracking capabilities and floccular output are needed to assess whether in any given experiment the actual tracking signal from the flocculus could or could not serve to induce brainstem plasticity. Similar considerations apply to the study of Ono et al [53], which showed impaired smooth pursuit in primates (produced by unilateral lesions of dorsolateral pontine nuclei) was not associated with any discernible effect on VOR adaptation.…”

Muscimol inactivation caudal to the interstitial nucleus of Cajal induces hemi-seesaw nystagmus

“…0.1–0.2 μl of muscimol (conc. 2%; Sigma–Aldrich) was delivered at the desired depth using a picoliter pump (WPI-PV830), connected to the micropipette, to provide timed air pressure pulses allowing for a gradual delivery of muscimol over several (5–10) minutes (Ono et al 2003). …”

The Long Journey of Pontine Nuclei Neurons: From Rhombic Lip to Cortico-Ponto-Cerebellar Circuitry

“…It receives major inputs from the visual cortex (Glickstein et al, 1980, 1994) and auditory cortex (Perales et al, 2006). The DLPN has been involved in optokinetic nystagmus including smooth-pursuit eye movements, ocular following, visually guided motor learning (Tziridis et al, 2009, 2012) and visually guided eye movements (May et al, 1988; Thier et al, 1988; Ono et al, 2003; Thier and Möck, 2006). …”