Pattern of brain activity during mental imagery of eye movements

NeuroImage

13, Number

6, 2001,

Part 2 of 2 Parts 10

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SENSORIMOTOR

Pattern of brain activity during mental imagery of eye movements F. Lui*, P. Baraldi*, F. Benuzzit, S. Fonda*, M. Maierong, M. Serafinig, P. Nichellit, R. Corazza*, C.A. Porro$ “Dipartimento

Science Biomediche, Universitd di Modena e Reggio Emilia

TDipartimento Patologia Neuropsicosensoriale, Universith di Modena e Reggio Emilia $Dipartimento Scienze e Tecnologie Biomediche, Universita ’ di Udine $A.S.L. Modena, Italia Previous studies have revealed that imagery of segmental motor events share a common neural performance (1,2). The present study is aimed at investigating whether the cortical regions activated during imagined activated during executed voluntary saccades.

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Methods The experiments were performed on a 1.5T GE Signa MR system, by a BOLD-sensitive EPI sequence (nihepi: courtesy of P. Jezzard; matrix: 3.75x3.75x4 mm). Eye movements were recorded during the fMRI acquisition by means of an infrared oculography apparatus (3). Eleven healthy, right-handed volunteers (4 males, 7 females), aged 20 to 45, were. shown one central fixation cross and two lateral targets (10” right and left from the center). The tasks consisted of 1) fixation of the central cross (FIX task); 2) execution of voluntary, self-paced saccades, starting from the central cross, to and from the lateral targets (MOV task); 3) mental imagery of the same movement sequence, without actual eye movement (IMM task). The task sequence was FIX-MOV-FIX-IMM-FIX, repeated twice for each run. Four runs were recorded for each subject. The tMRI data were analyzed by means of SPM99 (Wellcome Department of Cognitive Neurology, London, UK).

On-line eye movement recordings confirmed that the tasks were performed correctly, in that the average frequency of performed saccades was 1.2620.227 Hz during MOV, whereas during FIX and IMM it was only 0.011 ?O.OlO Hz and 0.027?0.029 Hz, respectively. A significant increase in fMRI signal intensity during MOV with respect to FIX was present, mainly in the left hemisphere, in the frontal eye fields (FBF: precentral gyrus and sulcus; mean Talairach coordinates, lxl= 29, y = -2, z = 55 mm), supplementary eye fields (SEF: dorsomedial portion of the superior frontal gyms; mean Talairach coordinates, 1x1 = 5, y = 3, z = 55 mm), parietal cortex (mean Talairach coordinates, 1x1 = 29, y = -54, z = 56 mm), and large portions of the occipital cortex. The same areas, but not the occipital cortex, were activated during imagery. In particular, signal intensity in the SEF increased in average 5% during both MOV and IMM. Statistical analysis (repeated measure ANOVA) of the Talairach coordinates of the peaks of activation showed no significant differences between the MOV and IMM tasks. Conclusions The present results demonstrate that mental imagery of saccadic eye movements induces comparable same frontal and parietal cortical regions that are activated during actual saccadic execution (4,5). References 1) 2) 3) 4) 5)

Porro et al., (1996) J. Neurosci. 16:7688-7698. Jeannerod and Frak, (1999) Curr Opin Neurobiol, 9:735-739. Kimming H et al., (1999) Exp. Brain Res. 126:443-449. Bodis-Wollner et al., (1997) Neurology 49:416-20. Lang et al., (1994) Neuroreport 5:921-924.

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