[Abstract Title]. - Society for Neuroscience

263. Eye Movements: Eye and Head Control
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 263.7/DD7
Topic: D.06.c. Eye and head control
Support: CIHR
HFSP
Canada Research Chair
Title: Superior colliculus activity during cued planning of sequenced head-free gaze shifts
Authors: M. AVILLAC 1,3 , *X. YAN 1 , J. ASENSCIO-MONTEON 1 , J. D. CRAWFORD 1,2 ;
1 Ctr. Vision Res., 2 Departments of Psychology, Biology, and Kinesiology & Hlth. Sci., York
Univ., Toronto, ON, Canada; 3 Neurobio. of Learning, Memory and Communication Laboratory,
CNRS UMR 8620, Paris-Sud Univ., Orsay, France
Abstract: Humans and non-human primates use different patterns of gaze sequences in eye-head
coordination as a function of the behavioral context. For example, both people and monkeys
show different eye-head kinematics when they plan a centrifugal-centripetal sequence of gaze
shifts vs. a centrifugal-centrifugal sequence, either in repetitive patterns (Oommen et al., Exp.
Brain. Res. 2004) or in response to a color cue (Ascensio-Monteon et al. Soc. Neurosci. Abst.
2007). The latter study also showed that these context-dependent behaviors are retained in gaze
saccades evoked during stimulation of the frontal eye fields, suggesting the presence of statedependent
signals in the brain. The aim of this study is to test the role of the superior colliculus
(SC) in processing these context-dependent signals. One rhesus monkey was trained to perform a
cued head-free gaze saccade sequence from a central fixation point, either out-in (back to centre),
or out-out (two equal sized gaze shifts) along any radial direction. The animal was cued to the
type of paradigm (red fixation light for out-in and green for out-out), but the saccade target and
required gaze displacement for the first saccade was constant. Eye and head movements were
tracked using search coils and a chamber was implanted over both SCs. After training, the outout
paradigm was always accompanied by a much larger head movement. Movement tuning
fields were characterized for 101 SC neurons, which were then tested in both paradigms along
their preferred and anti-preferred directions. 13 of these neurons were classified as primarily
visual (stimulus onset related), 36 as primarily motor (saccade related), 22 as visual and motor
(stimulus and saccade related), and 20 as primarily fixation-related. Our preliminary analysis
suggests that some units with a strong motor response show a greater response in their preferred
direction when the animal is cued that this will be followed by another saccade in the same
direction. Activity during subsequent movements was often predictable, but some units showed
unexpected activity in their off-direction before the second movement of the cued sequence. This
might reflect „confusion‟ over the meaning of the cue and the expected direction of the second