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The Journal of Neuroscience, November 1, 2006, 26(44):11347-11358; doi:10.1523/JNEUROSCI.2376-06.2006

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Behavioral/Systems/Cognitive
Enhanced Performance with Brain Stimulation: Attentional Shift or Visual Cue?

James Cavanaugh, Bryan D. Alvarez, and Robert H. Wurtz

Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20982-4435

Correspondence should be addressed to James Cavanaugh, Laboratory of Sensorimotor Research, National Eye Institute, Building 49, Room 2A50, 49 Convent Drive, Bethesda, MD 20982-4435. Email: jrc{at}lsr.nei.nih.gov

The premotor theory of visual spatial attention proposes that the same brain activity that prepares for saccades to one part of the visual field also facilitates visual processing at that same region of the visual field. Strong support comes from improvements in performance by electrical stimulation of presaccadic areas, including the frontal eye field and superior colliculus (SC). Interpretations of these stimulation experiments are hampered by the possibility that stimulation might be producing an internal visual flash or phosphene that attracts attention as a real flash would. We tested this phosphene hypothesis in the SC by comparing the effect of interchanging real visual stimuli and electrical stimulation. We first presented a veridical visual cue at the time SC stimulation improved performance; if a phosphene improved performance at this time, a real cue should do so in the same manner, but it did not. We then changed the time of SC visual-motor stimulation to when we ordinarily presented the veridical visual cue, and failed to improve performance. Last, we shifted the site of SC stimulation from the visual-motor neurons of the SC intermediate layers to the visual neurons of the superficial layers to determine whether stimulating visual neurons produced a larger improvement in performance, but it did not. Our experiments provide evidence that a phosphene is not responsible for the shift of attention that follows SC stimulation. This added evidence of a direct shift of attention is consistent with a key role of the SC in the premotor theory of attention.

Key words: colliculus; attention; visual; phosphene; macaque; stimulation

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Received June 5, 2006; revised Sept. 8, 2006; accepted Sept. 10, 2006.

Correspondence should be addressed to James Cavanaugh, Laboratory of Sensorimotor Research, National Eye Institute, Building 49, Room 2A50, 49 Convent Drive, Bethesda, MD 20982-4435. Email: jrc{at}lsr.nei.nih.gov

This article has been cited by other articles:

				D. K. Murphey and J. H. R. Maunsell Electrical microstimulation thresholds for behavioral detection and saccades in monkey frontal eye fields PNAS, May 20, 2008; 105(20): 7315 - 7320. [Abstract] [Full Text] [PDF]

				K. M. Armstrong and T. Moore Rapid enhancement of visual cortical response discriminability by microstimulation of the frontal eye field PNAS, May 29, 2007; 104(22): 9499 - 9504. [Abstract] [Full Text] [PDF]

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