Cortical activation patterns during voluntary blinks and voluntary saccades.

Abstract

To investigate the activation of frontal, parietal, and occipital areas in normal volunteers during voluntary blinks and during voluntary saccades using functional MRI (fMRI). A previous fMRI study revealed the activation of the precentral and posterior middle frontal gyrus ("frontal eye field" [FEF]), the medial part of the superior frontal gyrus ("supplementary eye field" [SEF]), and the visual cortex. The parietal cortex was not included in this study. Frontal and occipital cortical areas involved in voluntary blinking have not been shown previously using fMRI. A 1.5-T standard clinical scanner was used for both anatomic and functional studies in 12 observers. To conduct data analyses the authors used voxel-by-voxel cross-correlation. Voluntary blinks led to the activation (p < 0.05) of the FEF, the SEF, the posterior parietal cortex ("parietal eye field" [PEF]), and the visual cortex. Voluntary blinking produced activity in the same cerebral structures as voluntary saccades. However, the number of activated voxels was smaller during voluntary blinking than during voluntary saccades in the visual cortex and in the FEF (p < 0.01). In contrast, the extent of activation was significantly higher (p < 0.003) in the SEF and in the PEF during voluntary blinking. Voluntary blinks and saccades are associated with similar loci of activation patterns; however, the quantitative distribution of activation suggests that the middle part of the frontal gyrus and posterior parietal cortex are of special significance for voluntary blinks. The results argue for the importance of considering quantitative distributional properties of parallel cortical activities associated with saccades and blinks.