Some 30 years ago, Trevarthen [1] introduced the idea of two separate visual systems, a focal system for fine motor acts and an ambient system for gross body movements such as ambulation. More recent developments indicating anatomically and physiologically separate pathways in primate vision [2] have led to a different idea of separate visual systems, one for conscious perception and one for action [3]. It has received empirical support from several studies showing that pointing, reaching, and grasping can remain accurate while the perceived position or size of objects is subject to illusory distortion 4, 5 and 6. However, much of this evidence has been challenged on the grounds of methodological flaws, particularly failure to match perfectly the conditions for verbal and motor tasks and failure to replicate results 7, 8, 9 and 10. Here we take advantage of the strong compression of perceived position that occurs around the time of saccadic eye movements 11 and 12. Under normal lighting conditions, stimuli flashed briefly over a wide range of spatial positions just before saccadic onset are neither seen nor reached for in their veridical positions, but are compressed toward the saccadic target. We validate the idea of separate systems by showing that, in the dark, subjects are able to point accurately to the correct target position, even though their verbal reports are still subject to compression.
Separate visual representations for perception and action revealed by saccadic eye movements / David C. Burr ;M.Concetta Morrone; ; John Ross. - In: CURRENT BIOLOGY. - ISSN 0960-9822. - STAMPA. - 11:(2001), pp. 798-802.
Separate visual representations for perception and action revealed by saccadic eye movements
BURR, DAVID CHARLES;
2001
Abstract
Some 30 years ago, Trevarthen [1] introduced the idea of two separate visual systems, a focal system for fine motor acts and an ambient system for gross body movements such as ambulation. More recent developments indicating anatomically and physiologically separate pathways in primate vision [2] have led to a different idea of separate visual systems, one for conscious perception and one for action [3]. It has received empirical support from several studies showing that pointing, reaching, and grasping can remain accurate while the perceived position or size of objects is subject to illusory distortion 4, 5 and 6. However, much of this evidence has been challenged on the grounds of methodological flaws, particularly failure to match perfectly the conditions for verbal and motor tasks and failure to replicate results 7, 8, 9 and 10. Here we take advantage of the strong compression of perceived position that occurs around the time of saccadic eye movements 11 and 12. Under normal lighting conditions, stimuli flashed briefly over a wide range of spatial positions just before saccadic onset are neither seen nor reached for in their veridical positions, but are compressed toward the saccadic target. We validate the idea of separate systems by showing that, in the dark, subjects are able to point accurately to the correct target position, even though their verbal reports are still subject to compression.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.