Human Movement and Balance Unit,
Institute of Neurology,
University College London
will speak on
A fMRI Study of Anticipation and Learning in Smooth Pursuit Eye Movements
Smooth pursuit eye movements to predictable visual stimuli presented in the dark lead not only to improved tracking accuracy but also to anticipatory responses. In a functional magnetic imaging (fMRI) study of human volunteers (n=5) with simultaneous eye movement recording, such predictable conditions were achieved by an audio-cued, repeated presentation of a white dot moving at constant velocity (20o or 40o s-1, to the left or right). After 3 to 4 of the 10 presentations per condition the stimulus evoked a steady state response in which anticipatory smooth eye movements were initiated up to 300ms before stimulus onset. This was contrasted to smooth pursuit in a nonpredictable situation where timing of the audio cue, the velocities and directions were balanced but pseudo-randomised. This abolished the anticipation and improvement in tracking. In a control condition subjects were asked to gaze at the centre of the projection screen. The fMRI images were analyzed with the SPM99 software package for fixed effects of the 24s epochs per condition using mean and exponential decay functions to model changes in the blood oxygenation level dependent (BOLD) signal. Comparison of smooth pursuit with the control condition revealed statistical parametric maps in a network of brain areas known to be involved in visuomotor tasks and motion processing including prefrontal, premotor, medial temporal, parietal and cerebellar areas. While activations in the dorsolateral prefrontal cortex and the parietal areas around the intraparietal sulcus increased with time (p<0.001, corrected for multiple comparisons) during nonpredictable conditions, the anterior cingulate and preSMA showed an increase in activation during predictable epochs (pcluster= 0.015 and 0.003 respectively). These changes in activation over time may be associated with a type of short-term learning of the timing and eye movement trajectory and are reminiscent of findings in other types of motor and sequence learning. Intriguingly, the experiment revealed also a clear correlation of activation in the cuneus with the contraversive eye movement condition (p<0.001, corrected for multiple comparisons).
The lecture will take place in the Lecture Hall, Room 203, 44 Cummington St.
on Thursday, August 3, 2000
at 11:00 am
Hosted by the Brain and Vision Research Laboratory