Modeling of smooth pursuit-related neuronal responses in the DLPN and NRTP of the rhesus macaque.
The dorsolateral pontine nucleus (DLPN) and nucleus reticularis tegmenti pontis (NRTP) comprise obligatory links in the cortico-ponto-cerebellar system supporting smooth pursuit eye movements. We examined the response properties of DLPN and rNRTP neurons during step-ramp smooth pursuit of a small target moving across a dark background. Our neurophysiological studies were conducted in awake, behaving juvenile macaques (Macaca mulatta). We used multiple linear-regression modeling to estimate the relative sensitivities of neurons to eye parameters (position, velocity, and acceleration) and retinal-error parameters (position, velocity, and acceleration). We found that a large proportion of pursuit-related DLPN neurons primarily code eye-velocity information, whereas a large proportion of rNRTP neurons primarily code eye-acceleration information. We calculated the relative decrease in variance found when using a six-component model that included both eye- and retinal-error parameters compared with three-component models that include either eye or retinal error. These comparisons show that a majority of DLPN (14/20) and rNRTP (17/19) neurons have larger contributions from eye compared with retinal-error parameters (P < 0.001, paired t-test). Even though eye-motion parameters provide the strongest contributions in a given model, a significant contribution from retinal error was often present (i.e., >20% reduction in variance in 6-component model compared with 3-component models). Thus our results indicate that the DLPN plays a larger role in maintaining steady-state smooth pursuit eye velocity, whereas rNRTP contributes to both the initiation and maintenance of smooth pursuit.
Yerkes National Primate Research Center, Division of Visual Science, Emory University, 954 Gatewood Road N.E., Atlanta GA 30322, USA.
Seiji
S
Ono
Vallabh E
VE
Das
John R
JR
Economides
Michael J
MJ
Mustari
D000054:Acceleration; D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D008253:Macaca mulatta; D008954:Models, Biological; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011149:Pons / Q000166:cytology* / Q000502:physiology; D011698:Pursuit, Smooth / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*