Modulation of neuronal activity by target uncertainty

Access through your institution Buy or subscribe Visual scenes are composed of many elements and although we can appreciate a scene as a whole, we can only move our eyes to one element of

the scene at a time. As visual scenes become more complex, the number of potential targets in the scene increases, and the uncertainty that any particular one will be selected for an eye

movement also increases. How motor systems accommodate this target uncertainty remains unknown. The activities of neurons in both the cerebral cortex1,2,3,4,5 and superior colliculus6,7,8

are modulated by this selection process. We reasoned that activity associated with target uncertainty should be evident in the saccadic motor system at the final stages of neural processing,

in the superior colliculus9,10. By systematically changing the number of stimuli from which a selection must be made and recording from superior colliculus neurons, we found that as the

target uncertainty increased, the neural activity preceding target selection decreased. These results indicate that neurons within the final common pathway for movement generation are active

well in advance of the selection of a particular movement. This early activity varies with the probability that a particular movement will be selected. The intermediate layers of the

superior colliculus receive input from extensive regions of the cerebral cortex and may be regarded as a virtual readout of the cerebral cortex for the control of eye movements. Moreover,

prelude burst neurons and buildup neurons in the superior colliculus increase their activity with the selection and preparation of a movement long before the activity closely related to

saccade generation6,7,8. We determined the effect of target uncertainty on buildup neurons in awake monkeys in two ways. In the first experiment, we manipulated target uncertainty by

presenting a different number of possible targets to monkeys on different trials. In a second experiment, we manipulated target uncertainty by presenting the same visual array of possible

targets on every trial and varying the probability that any one of the stimuli would be selected for a saccadic eye movement. In both experiments we found that buildup neurons decreased

their activity as uncertainty increased. This is a preview of subscription content, access via your institution ACCESS OPTIONS Access through your institution Subscribe to this journal

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Google Scholar  Download references ACKNOWLEDGEMENTS We thank the Laboratory of Diagnostic Radiology Research for magnetic resonance images. We thank J. Steinberg for secretarial assistance

preparing the manuscript. We gratefully acknowledge the critical comments made on previous versions by J. Gottlieb and M. A. Sommer. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Laboratory

of Sensorimotor Research, National Eye Institute, Bethesda, 20892-4435, Maryland, USA Michele A. Basso & Robert H. Wurtz Authors * Michele A. Basso View author publications You can also

search for this author inPubMed Google Scholar * Robert H. Wurtz View author publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to

Michele A. Basso. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Basso, M., Wurtz, R. Modulation of neuronal activity by target uncertainty. _Nature_

389, 66–69 (1997). https://doi.org/10.1038/37975 Download citation * Received: 30 January 1997 * Accepted: 17 June 1997 * Issue Date: 04 September 1997 * DOI: https://doi.org/10.1038/37975

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