Visual masking: past accomplishments, present status, future developments.
Bottom Line: However, visual masking also has been a phenomenon deemed worthy of study in its own right.Most of the recent uses of visual masking have focused on the study of central processes, particularly those involved in feature, object and scene representations, in attentional control mechanisms, and in phenomenal awareness.Key issues and problems are discussed with the aim of guiding future empirical and theoretical research.
Affiliation: Department of Psychology, University of Houston.
Visual masking, throughout its history, has been used as an investigative tool in exploring the temporal dynamics of visual perception, beginning with retinal processes and ending in cortical processes concerned with the conscious registration of stimuli. However, visual masking also has been a phenomenon deemed worthy of study in its own right. Most of the recent uses of visual masking have focused on the study of central processes, particularly those involved in feature, object and scene representations, in attentional control mechanisms, and in phenomenal awareness. In recent years our understanding of the phenomenon and cortical mechanisms of visual masking also has benefited from several brain imaging techniques and from a number of sophisticated and neurophysiologically plausible neural network models. Key issues and problems are discussed with the aim of guiding future empirical and theoretical research.
No MeSH data available.
Mentions: Based on their results and on the above reasoning, Macknik and Livingstone (1998) developed what I believe to be currently the most effective masking method, namely, the standing-wave illusion, for rendering stimuli invisible. In this method a mask appears about 100 ms before the target, which in turn is followed about 50 ms by the mask, followed 100 ms by the target and so on. Basically the target and mask are presented at optimal para- and metacontrast SOAs throughout the presentation (see Figure 5 below), thus giving the target a “double masking whammy” by suppressing first its feedforward activity and then in addition the (already weakened) re-entrant activity. While this method produces very powerful suppression of target visibility that correlates well with brain imaging (fMRI) findings (Tse, Martinez-Conde, Schlegel, & Macknik, 2005), it renders difficult any interpretations of results in terms of either para- or metacontrast effect alone. However, thanks to the work of Haynes, Driver, and Rees (2005) we do have brain imaging results that were obtained with an isolated metacontrast effect. What their findings show (see Figure 3) is that the functional correlation between earlier (V1) and later (fusiform gyrus) areas in visual cortex is suppressed by the metacontrast mask. In view of what I have outlined so far above, I suspect that the disruption of connectivity is due to a reduction of reentrant feedback from higher to lower areas. Is there independent, convergent evidence for this feedforward and reentrant scheme of para- and metacontrast?
No MeSH data available.