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Do extraocular motoneurons encode head velocity during head-restrained versus head-unrestrained saccadic and smooth pursuit movements?
| Content Provider | Semantic Scholar |
|---|---|
| Copyright Year | 2001 |
| Abstract | Microstimulation experiments in the superior colliculus1 and single-unit recordings from its target, the premotor saccadic burst neurons2 (SBNs, located in the paramedian pontine reticular formation), have shown that the saccadic burst generator encodes head as well as eye movements during head-unrestrained gaze shifts. There is also evidence suggesting that premotor circuits likely encode eye and head motion during head-unrestrained gaze pursuit.3,4 Hence, although extraocular muscle motoneurons directly drive the eye movements, the premotor inputs they receive during voluntary gaze redirection behaviors are related to eye and head motion. To account for this apparent mismatch in premotor/motor drives during head-unrestrained movements, two mechanisms have been envisaged: (1) a premotor signal proportional to the head contribution of the gaze shift is subtracted out at the level of the motoneurons, or (2) individual motoneurons encode eye and head motor commands, and proper eye movements result from interactions at the level of the oculomotor plant. Rather surprisingly, previous metric-based studies of extraocular motoneuron discharges during gaze shifts have suggested that the latter mechanism may be more appropriate.5,6 Here, we have characterized the firing rates of extraocular motoneurons in head-restrained and head-unrestrained conditions using a more sophisticated dynamic-based approach and find that metric-based analyses can yield misleading results. As we have previously shown, the firing rates of extraocular motoneurons and internuclear neurons in the abducens nucleus (collectively referred to as ABNs) during head-restrained eye movements could be well approximated using a first-order dynamic model of eye motion.7 In the present study, we characterized and compared the discharge dynamics of the same isolated ABNs (n = 7, obtained from two trained rhesus monkeys) during (1) head-restrained saccades versus head-unrestrained gaze shifts, and (2) head-restrained smooth pursuit versus head-unrestrained gaze pursuit. We first observed that the activity of ABNs, in contrast to that of SBNs, remains related to the eye motion by the same dynamic relationship during head-restrained saccades and head-unrestrained gaze shifts.5 This is illustrated in FIGURE 1A (head- |
| Starting Page | 497 |
| Ending Page | 500 |
| Page Count | 4 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.mcgill.ca/vestibular-gazecontrol-lab/files/vestibular-gazecontrol-lab/52_sylvestre_roy_cullen_2002.pdf |
| PubMed reference number | 11710499v1 |
| Volume Number | 942 |
| Journal | Annals of the New York Academy of Sciences |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Behavior Body Fluid Discharge CDISC ADAS-Cog - Commands Summary Score Cell Nucleus Encode (action) Eye Movements Intrinsic drive Macaca mulatta Monkeys Motor Neurons Movement Muscle of orbit Pontine structure Pursuit, Smooth Reticular Formation Saccades Structure of abducens nucleus |
| Content Type | Text |
| Resource Type | Article |
