Object substitution masking and the object updating hypothesis who is andrienne balion dating now
Moreover, it did not appear that the patients’ deficit was due to issues in initial processing of the target because when using the same SOAs and using a single dot to indicate which target to identify, we found: (1) that there was no group difference in behavior; and (2) iconic decay of the target was not different between groups.
Therefore, the increased masking effects in schizophrenia patients appeared to be due to the presence of the mask and not other factors. Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text Lamme, V.
Four-dot masking can occur when both target and mask have the same onset (termed “common-onset masking”) and the mask remains visible longer than the target and can also occur when the onset of the mask appears at varying stimulus onset asynchronies (SOAs) relative to the target (Enns and Di Lollo, 2000). Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text Leitman, D.
Using this second type of four-dot masking in a behavioral study we found impairments in schizophrenia patients (Green et al., 2011). The distinct modes of vision offered by feedforward and recurrent processing.
Considering that the VAN is thought to reflect reentrant processing, one interpretation of the findings is that patients’ lack of VAN response and poorer performance may be related to dysfunctional reentrant processing.
Patients with schizophrenia exhibit several visual processing impairments (Green et al., 1994; Butler et al., 2003; Butler and Javitt, 2005; Rassovsky et al., 2005; Wynn et al., 2005; Silverstein and Keane, 2011), and these impairments have been tied to specific neural abnormalities, such as magnocellular pathway dysfunction, NMDA functioning, and activation in the lateral occipital complex (Butler et al., 2005; Green et al., 2009; Javitt, 2009). Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text Rassovsky, Y., Green, M.
Several ERP studies have examined backward masking in healthy participants. (2007) found that both masked and unmasked targets produced a strong bilateral anterior occipito-temporal activation that occurred prior to 110 ms (likely consistent with the visual P100), which the authors attributed to feedforward processing of visual stimuli.
However, only unmasked trials resulted in activity between 110–140 ms at posterior occipital sites, with no activity for masked trials seen at this time frame.
Object substitution masking, therefore, has provided a method to examine reentrant visual processing (Woodman and Luck, 2003).
The P100 is a positive wave peaking approximately 100 ms post stimulus onset.
Several neural generators of the P100 have been identified, with activity largest over dorsal stream sites, with extrastriate and striate contributions (Maier et al., 1987; Aine et al., 1995; Di Russo et al., 2001; Vanni et al., 2004).
The premise underlying object substitution is that the feedforward sweep of the target must be refined at higher cortical levels through reentrant processes to the lower input levels. Principal component analysis for source localization VEPs in man.
If the mask is presented before the target is identified at this higher-level, there will be a mismatch between the feedforward and reentrant sweeps, and processing will switch to the mask. Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text Maier, J., Dagnelie, G., Spekreijse, H., and van Dijk, B.