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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.


Grand average difference ERPs computed by subtracting ERPs in two conditions. For display, waves were low pass filtered at 20 Hz. (A)Difference waves of impoverishment effects. Effects of impoverishment shown by subtracting the less impoverished (LI) condition from the more impoverished condition (MI). Up is negativity in MI greater than LI. Note, where the impoverishment difference wave was greater for real than pseudo objects reveals the impoverished-real-object effect. (B)Difference waves of object type effects. Effects of object knowledge shown by subtracting the real object condition from the pseudo object condition. Up is negativity for pseudo greater than real objects.
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Figure 7: Grand average difference ERPs computed by subtracting ERPs in two conditions. For display, waves were low pass filtered at 20 Hz. (A)Difference waves of impoverishment effects. Effects of impoverishment shown by subtracting the less impoverished (LI) condition from the more impoverished condition (MI). Up is negativity in MI greater than LI. Note, where the impoverishment difference wave was greater for real than pseudo objects reveals the impoverished-real-object effect. (B)Difference waves of object type effects. Effects of object knowledge shown by subtracting the real object condition from the pseudo object condition. Up is negativity for pseudo greater than real objects.

Mentions: For the four difference waves (Figure 7), cortical sources were estimated. The main focus was the time of the N3 peak from 300 to 400 ms (Figures 8A–D). Sources of this impoverishment effect (MI vs. LI) for real objects localized to occipitotemporal and lateral prefrontal areas found with fMRI (Ganis et al., 2007), whereas, for pseudo objects, impoverishment differences localized only to prefrontal areas. Sources of the object type effects (real vs. pseudo) on both LI and MI trials were in occipitotemporal areas. Sources at other times were also estimated. At all times after 200 ms, type effects continued in the same occipitotemporal areas (Figures 8C,D,G,H). Impoverishment sources varied over time and with object type (Figures 8A,B,E,F). The 200 to 300 ms time during the P250/N250 component showed the same impoverished-real-object pattern of sources as the peak N3 time period. Later, from 400 to 500 ms when the N3 ends and the N400 peaks, impoverishment effects for real objects showed only the occipitotemporal source (see intracranial ERP in Figure 8A). Around 450 ms, the maximum source shifted to anterotemporal cortex for both real and pseudo objects, suggesting an additional contribution from this region to the N400. From 500 to 700 ms, the estimated intracranial ERP for the anterotemporal source resembled the scalp P600 impoverishment waveform, which is maximal at this time, and more mediotemporal sources also contributed (Figures 8E,F). From 700 to 900 ms when the late SW dominates, anterotemporal impoverishment activity continued only for real objects. In addition, for both object types, impoverishment effects now appeared in the posterior cingulate cortex (PCC; Figures 8E,F).


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

Schendan HE, Ganis G - Front Psychol (2015)

Grand average difference ERPs computed by subtracting ERPs in two conditions. For display, waves were low pass filtered at 20 Hz. (A)Difference waves of impoverishment effects. Effects of impoverishment shown by subtracting the less impoverished (LI) condition from the more impoverished condition (MI). Up is negativity in MI greater than LI. Note, where the impoverishment difference wave was greater for real than pseudo objects reveals the impoverished-real-object effect. (B)Difference waves of object type effects. Effects of object knowledge shown by subtracting the real object condition from the pseudo object condition. Up is negativity for pseudo greater than real objects.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 7: Grand average difference ERPs computed by subtracting ERPs in two conditions. For display, waves were low pass filtered at 20 Hz. (A)Difference waves of impoverishment effects. Effects of impoverishment shown by subtracting the less impoverished (LI) condition from the more impoverished condition (MI). Up is negativity in MI greater than LI. Note, where the impoverishment difference wave was greater for real than pseudo objects reveals the impoverished-real-object effect. (B)Difference waves of object type effects. Effects of object knowledge shown by subtracting the real object condition from the pseudo object condition. Up is negativity for pseudo greater than real objects.
Mentions: For the four difference waves (Figure 7), cortical sources were estimated. The main focus was the time of the N3 peak from 300 to 400 ms (Figures 8A–D). Sources of this impoverishment effect (MI vs. LI) for real objects localized to occipitotemporal and lateral prefrontal areas found with fMRI (Ganis et al., 2007), whereas, for pseudo objects, impoverishment differences localized only to prefrontal areas. Sources of the object type effects (real vs. pseudo) on both LI and MI trials were in occipitotemporal areas. Sources at other times were also estimated. At all times after 200 ms, type effects continued in the same occipitotemporal areas (Figures 8C,D,G,H). Impoverishment sources varied over time and with object type (Figures 8A,B,E,F). The 200 to 300 ms time during the P250/N250 component showed the same impoverished-real-object pattern of sources as the peak N3 time period. Later, from 400 to 500 ms when the N3 ends and the N400 peaks, impoverishment effects for real objects showed only the occipitotemporal source (see intracranial ERP in Figure 8A). Around 450 ms, the maximum source shifted to anterotemporal cortex for both real and pseudo objects, suggesting an additional contribution from this region to the N400. From 500 to 700 ms, the estimated intracranial ERP for the anterotemporal source resembled the scalp P600 impoverishment waveform, which is maximal at this time, and more mediotemporal sources also contributed (Figures 8E,F). From 700 to 900 ms when the late SW dominates, anterotemporal impoverishment activity continued only for real objects. In addition, for both object types, impoverishment effects now appeared in the posterior cingulate cortex (PCC; Figures 8E,F).

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.