Ž . Cognitive Brain Research 8 1999 143–156 www.elsevier.comrlocaterbres Research report Effects of exogenous and endogenous attention on visually guided hand movements Daeyeol Lee ) Department of Neurobiology and Anatomy, Wake Forest UniÕersity School of Medicine, Winston-Salem, NC 27157, USA Accepted 6 April 1999 Abstract Attention can be directed to a peripheral location by either a peripheral visual stimulus or a central cue indicating the likely location of an upcoming target. The present study examined the effects of peripheral and central cuing on reaching. When the target was presented in Ž . a location different from that indicated by either type of attentional cue, movements with short latencies -200 ms were mostly initiated toward the cued location. When the target was presented 908 away from the direction indicated by the attentional cue, movements with Ž . intermediate latencies 200–300 ms were often initiated in directions intermediate between the cue and the target, and the latencies of movements initiated toward the target were prolonged. This suggests that the location of an attentional cue was utilized as an initial value in the process specifying movement direction, and this was gradually modified by signals related to target location. When peripheral and central cues were combined in the same trials, effects of peripheral cues were substantially diminished, compared to when they were examined separately. Furthermore, movements were seldom initiated in directions intermediate between the two cues, suggesting that effects of peripheral and central cues are combined independently from the process that specifies movement direction. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Human subject; Kinematics; Reaching; Spatial attention 1. Introduction Previous studies have demonstrated that attention can w x be controlled in at least two distinct modes 5,15,23 . For example, when an area of the peripheral visual field is suddenly illuminated, it tends to capture attention automat- ically, and facilitate the processing of a visual stimulus presented shortly thereafter in the same area. This is w x referred to as exogenous control of attention 15,23,38 . This facilitation lasts only for a couple of hundred mil- liseconds, and gradually turns into suppression as the presentation of the target stimulus is delayed, a process w x known as inhibition of return 20,24,25 . Attention can be also summoned to a particular region in visual space by a Ž . symbolic cue e.g., arrow presented in the central visual field, and this is referred to as endogenous control of w x visual attention 15,23 . In contrast to exogenous attention, w x effects of endogenous attention develop more slowly 3,21 , w x and can be controlled voluntarily 15 . Several studies, comparing relative effectiveness of peripheral and central ) Fax: q1-336-716-4534; E-mail: dlee@wfubmc.edu cues in controlling attention, demonstrated that peripheral w x cues capture attention more effectively 15,16,18 . How- ever, the effects of peripheral cues are not completely obligatory, because they can be prevented by prior alloca- w x tion of attention in a different location 16,18,36,39 . Whereas most of the above studies used reaction time measures obtained from key pressing, attention may also have effects on other aspects of movements, such as initial movement direction or trajectory. Only a few studies have examined this issue, and most of them have demonstrated inhibitory effects of attention on movement trajectory, w x w x namely, eye 29,30 or hand 14,35 movements were found to deviate away from the cued location. In those studies, however, cued locations never became the targets of movements, raising the possibility that effects of atten- tion on movement trajectory may be facilitatory, veering trajectory toward cued locations, if they become targets in some trials. To test this possibility for different types of attention, in the present study, the effects of exogenous and endogenous attention on the initial direction and la- tency of reaching movements were examined, using pe- Ž . Ž . ripheral Experiment 1 and central Experiment 2 cues, 0926-6410r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0926-6410 99 00014-2