Limits...
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.


ERP effects of impoverishment and object type. Grand average ERPs at all channels show effects of impoverishment (more [MI], less [LI] impoverished) and object type (real, pseudo). Unless otherwise specified, ERPs in this and following figures were low-pass filtered at 30 Hz and were referenced to the average of left and right mastoids. Numerals label electrode locations; ns, nose. Impoverishment and object type modulated the N3 complex (including P250/N250 and D220 components; components inverted polarity between frontal and occipitotemporal sites), N400, P600, and slow wave (SW) components after 200 ms, but not the earlier VPP/N170.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4584963&req=5

Figure 3: ERP effects of impoverishment and object type. Grand average ERPs at all channels show effects of impoverishment (more [MI], less [LI] impoverished) and object type (real, pseudo). Unless otherwise specified, ERPs in this and following figures were low-pass filtered at 30 Hz and were referenced to the average of left and right mastoids. Numerals label electrode locations; ns, nose. Impoverishment and object type modulated the N3 complex (including P250/N250 and D220 components; components inverted polarity between frontal and occipitotemporal sites), N400, P600, and slow wave (SW) components after 200 ms, but not the earlier VPP/N170.

Mentions: The aim was to determine when impoverishment and object type interact such that the impoverishment effect is larger for real than pseudo objects. Table 1 summarizes ERP results, which were most consistent with late parietal-prefrontal PHT, MUSI, and decision theories. After 200 ms, impoverishment affected knowledge activation, modulating the N3 complex, N400, P600, and SW (Figures 3, 4); note, as results suggested no distinct LPC effects, henceforth, we refer only to the P600 and the SW.


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 and object type. Grand average ERPs at all channels show effects of impoverishment (more [MI], less [LI] impoverished) and object type (real, pseudo). Unless otherwise specified, ERPs in this and following figures were low-pass filtered at 30 Hz and were referenced to the average of left and right mastoids. Numerals label electrode locations; ns, nose. Impoverishment and object type modulated the N3 complex (including P250/N250 and D220 components; components inverted polarity between frontal and occipitotemporal sites), N400, P600, and slow wave (SW) components after 200 ms, but not the earlier VPP/N170.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: ERP effects of impoverishment and object type. Grand average ERPs at all channels show effects of impoverishment (more [MI], less [LI] impoverished) and object type (real, pseudo). Unless otherwise specified, ERPs in this and following figures were low-pass filtered at 30 Hz and were referenced to the average of left and right mastoids. Numerals label electrode locations; ns, nose. Impoverishment and object type modulated the N3 complex (including P250/N250 and D220 components; components inverted polarity between frontal and occipitotemporal sites), N400, P600, and slow wave (SW) components after 200 ms, but not the earlier VPP/N170.
Mentions: The aim was to determine when impoverishment and object type interact such that the impoverishment effect is larger for real than pseudo objects. Table 1 summarizes ERP results, which were most consistent with late parietal-prefrontal PHT, MUSI, and decision theories. After 200 ms, impoverishment affected knowledge activation, modulating the N3 complex, N400, P600, and SW (Figures 3, 4); note, as results suggested no distinct LPC effects, henceforth, we refer only to the P600 and the SW.

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.