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Top-down modulation of visual processing and knowledge after 250 ms supports object constancy of category decisions.

Schendan HE, Ganis G - Front Psychol (2015)

Bottom Line: N3 impoverishment effects localized to both prefrontal and occipitotemporal cortex for real objects only.The N3 also showed knowledge effects by 230 ms that localized to occipitotemporal cortex.Finally, response activity in supplementary motor area during a posterior SW after 900 ms showed impoverishment effects that correlated with RTs.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology, Cognition Institute, University of Plymouth Plymouth, UK.

ABSTRACT
People categorize objects more slowly when visual input is highly impoverished instead of optimal. While bottom-up models may explain a decision with optimal input, perceptual hypothesis testing (PHT) theories implicate top-down processes with impoverished input. Brain mechanisms and the time course of PHT are largely unknown. This event-related potential study used a neuroimaging paradigm that implicated prefrontal cortex in top-down modulation of occipitotemporal cortex. Subjects categorized more impoverished and less impoverished real and pseudo objects. PHT theories predict larger impoverishment effects for real than pseudo objects because top-down processes modulate knowledge only for real objects, but different PHT variants predict different timing. Consistent with parietal-prefrontal PHT variants, around 250 ms, the earliest impoverished real object interaction started on an N3 complex, which reflects interactive cortical activity for object cognition. N3 impoverishment effects localized to both prefrontal and occipitotemporal cortex for real objects only. The N3 also showed knowledge effects by 230 ms that localized to occipitotemporal cortex. Later effects reflected (a) word meaning in temporal cortex during the N400, (b) internal evaluation of prior decision and memory processes and secondary higher-order memory involving anterotemporal parts of a default mode network during posterior positivity (P600), and (c) response related activity in posterior cingulate during an anterior slow wave (SW) after 700 ms. Finally, response activity in supplementary motor area during a posterior SW after 900 ms showed impoverishment effects that correlated with RTs. Convergent evidence from studies of vision, memory, and mental imagery which reflects purely top-down inputs, indicates that the N3 reflects the critical top-down processes of PHT. A hybrid multiple-state interactive, PHT and decision theory best explains the visual constancy of object cognition.

No MeSH data available.


Related in: MedlinePlus

ERP effects of impoverishment (by fragmentation level) and object type. Same as Figure 3, except impoverishment is defined using picture fragmentation level: LI is levels 2–3; MI is levels 4–5. Results from this analysis replicate those in Figure 3 which used the median split of RTs to define impoverishment.
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Figure 10: ERP effects of impoverishment (by fragmentation level) and object type. Same as Figure 3, except impoverishment is defined using picture fragmentation level: LI is levels 2–3; MI is levels 4–5. Results from this analysis replicate those in Figure 3 which used the median split of RTs to define impoverishment.

Mentions: The results so far used the median split of RTs to define MI and LI conditions. In a separate analysis of ERPs until 900 ms, fragmentation levels 4–5 defined the MI condition and levels 2–3 defined the LI condition (Figure 10). Results of the fragmentation level analyses replicated all results from the RT split analyses. It may be noted that impoverishment effects for real objects were slightly smaller with fragmentation level defining impoverishment, but this would be expected. After all, the most and least fragmented images were excluded from this fragmentation based analysis but included in the RT based analysis and so stimulus differences were smaller with fragmentation instead of RT defining impoverishment. Further, as RT must completely capture all stimulus impoverishment that affects RTs, impoverishment effects should be larger for results based on RTs than any single factor such as fragmentation.


Top-down modulation of visual processing and knowledge after 250 ms supports object constancy of category decisions.

Schendan HE, Ganis G - Front Psychol (2015)

ERP effects of impoverishment (by fragmentation level) and object type. Same as Figure 3, except impoverishment is defined using picture fragmentation level: LI is levels 2–3; MI is levels 4–5. Results from this analysis replicate those in Figure 3 which used the median split of RTs to define impoverishment.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4584963&req=5

Figure 10: ERP effects of impoverishment (by fragmentation level) and object type. Same as Figure 3, except impoverishment is defined using picture fragmentation level: LI is levels 2–3; MI is levels 4–5. Results from this analysis replicate those in Figure 3 which used the median split of RTs to define impoverishment.
Mentions: The results so far used the median split of RTs to define MI and LI conditions. In a separate analysis of ERPs until 900 ms, fragmentation levels 4–5 defined the MI condition and levels 2–3 defined the LI condition (Figure 10). Results of the fragmentation level analyses replicated all results from the RT split analyses. It may be noted that impoverishment effects for real objects were slightly smaller with fragmentation level defining impoverishment, but this would be expected. After all, the most and least fragmented images were excluded from this fragmentation based analysis but included in the RT based analysis and so stimulus differences were smaller with fragmentation instead of RT defining impoverishment. Further, as RT must completely capture all stimulus impoverishment that affects RTs, impoverishment effects should be larger for results based on RTs than any single factor such as fragmentation.

Bottom Line: N3 impoverishment effects localized to both prefrontal and occipitotemporal cortex for real objects only.The N3 also showed knowledge effects by 230 ms that localized to occipitotemporal cortex.Finally, response activity in supplementary motor area during a posterior SW after 900 ms showed impoverishment effects that correlated with RTs.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology, Cognition Institute, University of Plymouth Plymouth, UK.

ABSTRACT
People categorize objects more slowly when visual input is highly impoverished instead of optimal. While bottom-up models may explain a decision with optimal input, perceptual hypothesis testing (PHT) theories implicate top-down processes with impoverished input. Brain mechanisms and the time course of PHT are largely unknown. This event-related potential study used a neuroimaging paradigm that implicated prefrontal cortex in top-down modulation of occipitotemporal cortex. Subjects categorized more impoverished and less impoverished real and pseudo objects. PHT theories predict larger impoverishment effects for real than pseudo objects because top-down processes modulate knowledge only for real objects, but different PHT variants predict different timing. Consistent with parietal-prefrontal PHT variants, around 250 ms, the earliest impoverished real object interaction started on an N3 complex, which reflects interactive cortical activity for object cognition. N3 impoverishment effects localized to both prefrontal and occipitotemporal cortex for real objects only. The N3 also showed knowledge effects by 230 ms that localized to occipitotemporal cortex. Later effects reflected (a) word meaning in temporal cortex during the N400, (b) internal evaluation of prior decision and memory processes and secondary higher-order memory involving anterotemporal parts of a default mode network during posterior positivity (P600), and (c) response related activity in posterior cingulate during an anterior slow wave (SW) after 700 ms. Finally, response activity in supplementary motor area during a posterior SW after 900 ms showed impoverishment effects that correlated with RTs. Convergent evidence from studies of vision, memory, and mental imagery which reflects purely top-down inputs, indicates that the N3 reflects the critical top-down processes of PHT. A hybrid multiple-state interactive, PHT and decision theory best explains the visual constancy of object cognition.

No MeSH data available.


Related in: MedlinePlus