Although texture segregation models confine border extraction to high-level processes, recent findings suggest the involvement of low-level mechanisms (Grieco et al, 2006 Vision Research 46 3526 ^ 3536). To investigate whether texture segregation is restricted to early-filtering mechanisms, or whether they involve later-levels of analysis, we measured how a backward-masking stimulus, known to interrupt re-entrant signals from high-level areas (Lamme et al, 2002 Journal of Cogni- tive Neuroscience 14 1044 ^ 1053), affects subject's accuracy in target-present (requiring texture segmentation) and target-absent (requiring distractors grouping) trials in a detection task, after a learning session without backward-masking. Here, we show that, although learning effects in texture segregation were specific to contrast polarity, indicating low-level filtering mechanisms, the improvements were abolished by a backward-mask presentation, suggesting the involvement of re-entrant signals from high-level areas. Instead, learning of distractor grouping was not specific to contrast polarity, nor was it affected by backward masking, indicating a high-level learning process. This finding raises an important challenge that must be faced in understanding the mechanisms underlying texture segregation and grouping by similarity.

Mask interrupts texture segregation but not grouping processes

GRIECO, ALBA;CAMPANA, GIANLUCA;CASCO, CLARA;RONCATO, SERGIO
2007

Abstract

Although texture segregation models confine border extraction to high-level processes, recent findings suggest the involvement of low-level mechanisms (Grieco et al, 2006 Vision Research 46 3526 ^ 3536). To investigate whether texture segregation is restricted to early-filtering mechanisms, or whether they involve later-levels of analysis, we measured how a backward-masking stimulus, known to interrupt re-entrant signals from high-level areas (Lamme et al, 2002 Journal of Cogni- tive Neuroscience 14 1044 ^ 1053), affects subject's accuracy in target-present (requiring texture segmentation) and target-absent (requiring distractors grouping) trials in a detection task, after a learning session without backward-masking. Here, we show that, although learning effects in texture segregation were specific to contrast polarity, indicating low-level filtering mechanisms, the improvements were abolished by a backward-mask presentation, suggesting the involvement of re-entrant signals from high-level areas. Instead, learning of distractor grouping was not specific to contrast polarity, nor was it affected by backward masking, indicating a high-level learning process. This finding raises an important challenge that must be faced in understanding the mechanisms underlying texture segregation and grouping by similarity.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11577/2516086
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