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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

Method and performance. (A) A 2 × 2 repeated measures design was used with impoverishment (less, more) and object type (real, pseudo) as factors. Fragmented line drawings of real and pseudo objects were shown. Pseudo objects had been created by re-locating the local parts of each real object to create a closed, perceptually coherent but unknown more global shape that could exist in a Euclidean 3-dimensional world but cannot be categorized (Schendan et al., 1998). Subjects pressed “1” to report that they categorized the object or, if not, they pressed “2,” as soon as possible after the picture appeared. A median split of the RTs to real and pseudo objects, separately, for correct responses (i.e., 1 for real objects, 2 for pseudo objects) separated these conditions into more (MI) and less (LI) impoverished conditions. Shown are real objects of an LI fish at fragmentation level 3, and MI piano at level 4, and an LI pseudo-fish at level 5, and MI pseudo-piano at level 4; note, sample stimuli reflect the consistent finding that more fragmented real objects are related to slower RTs, whereas more fragmented pseudo objects are related to faster RTs. Stimuli subtended 6 by 6 degrees of visual angle, on average, with a visual contrast of approximately 30% (dark pixels against a brighter background). (B) Custom 60-channel geodesic montage for EEG recording (Electrocap International). Circles show electrode locations. Numbers label each electrode. Approximate locations of 10–20 sites are shown in gray italics; site 57 is at Cz, site 60 is Oz; pairs 31–32, and 49–50 are 1 cm below the inion. (C) Response times to MI and LI real and pseudo objects. Error bars show the 95% confidence interval (Morey, 2008). *Significant impoverishment effect.
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Figure 2: Method and performance. (A) A 2 × 2 repeated measures design was used with impoverishment (less, more) and object type (real, pseudo) as factors. Fragmented line drawings of real and pseudo objects were shown. Pseudo objects had been created by re-locating the local parts of each real object to create a closed, perceptually coherent but unknown more global shape that could exist in a Euclidean 3-dimensional world but cannot be categorized (Schendan et al., 1998). Subjects pressed “1” to report that they categorized the object or, if not, they pressed “2,” as soon as possible after the picture appeared. A median split of the RTs to real and pseudo objects, separately, for correct responses (i.e., 1 for real objects, 2 for pseudo objects) separated these conditions into more (MI) and less (LI) impoverished conditions. Shown are real objects of an LI fish at fragmentation level 3, and MI piano at level 4, and an LI pseudo-fish at level 5, and MI pseudo-piano at level 4; note, sample stimuli reflect the consistent finding that more fragmented real objects are related to slower RTs, whereas more fragmented pseudo objects are related to faster RTs. Stimuli subtended 6 by 6 degrees of visual angle, on average, with a visual contrast of approximately 30% (dark pixels against a brighter background). (B) Custom 60-channel geodesic montage for EEG recording (Electrocap International). Circles show electrode locations. Numbers label each electrode. Approximate locations of 10–20 sites are shown in gray italics; site 57 is at Cz, site 60 is Oz; pairs 31–32, and 49–50 are 1 cm below the inion. (C) Response times to MI and LI real and pseudo objects. Error bars show the 95% confidence interval (Morey, 2008). *Significant impoverishment effect.

Mentions: A 2 × 2 repeated measures factorial design (Figure 2A) included factors of impoverishment (LI, MI) and object type (real, pseudo). General health history and Edinburgh Handedness (Oldfield, 1971) questionnaires were administered before each session. The ERP session started with instructions on the computer screen that subjects paraphrased aloud, and any misconceptions were corrected. They were instructed on the task, to maintain eye gaze on the fixation mark at the center of the screen, and blink only in the fixation period. They then received 10 practice trials using the experiment methods but different stimuli. On each experiment trial, a fixation period of 5400–5700 ms preceded each picture, which was presented for 1000 ms while subjects decided whether they could categorize each object. They pressed “1” as soon as they knew what the object was, or “2” if they did not know, as quickly as possible without sacrificing accuracy. Participants were informed that categorization would be challenging by design because the images were degraded. They were not informed that some objects were impossible to categorize (i.e., pseudo objects) and so, from the subjects' perspective, pseudo objects were just images that they could not categorize (i.e., possible “real” objects that they failed to categorize).


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

Schendan HE, Ganis G - Front Psychol (2015)

Method and performance. (A) A 2 × 2 repeated measures design was used with impoverishment (less, more) and object type (real, pseudo) as factors. Fragmented line drawings of real and pseudo objects were shown. Pseudo objects had been created by re-locating the local parts of each real object to create a closed, perceptually coherent but unknown more global shape that could exist in a Euclidean 3-dimensional world but cannot be categorized (Schendan et al., 1998). Subjects pressed “1” to report that they categorized the object or, if not, they pressed “2,” as soon as possible after the picture appeared. A median split of the RTs to real and pseudo objects, separately, for correct responses (i.e., 1 for real objects, 2 for pseudo objects) separated these conditions into more (MI) and less (LI) impoverished conditions. Shown are real objects of an LI fish at fragmentation level 3, and MI piano at level 4, and an LI pseudo-fish at level 5, and MI pseudo-piano at level 4; note, sample stimuli reflect the consistent finding that more fragmented real objects are related to slower RTs, whereas more fragmented pseudo objects are related to faster RTs. Stimuli subtended 6 by 6 degrees of visual angle, on average, with a visual contrast of approximately 30% (dark pixels against a brighter background). (B) Custom 60-channel geodesic montage for EEG recording (Electrocap International). Circles show electrode locations. Numbers label each electrode. Approximate locations of 10–20 sites are shown in gray italics; site 57 is at Cz, site 60 is Oz; pairs 31–32, and 49–50 are 1 cm below the inion. (C) Response times to MI and LI real and pseudo objects. Error bars show the 95% confidence interval (Morey, 2008). *Significant impoverishment effect.
© Copyright Policy
Related In: Results  -  Collection

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Figure 2: Method and performance. (A) A 2 × 2 repeated measures design was used with impoverishment (less, more) and object type (real, pseudo) as factors. Fragmented line drawings of real and pseudo objects were shown. Pseudo objects had been created by re-locating the local parts of each real object to create a closed, perceptually coherent but unknown more global shape that could exist in a Euclidean 3-dimensional world but cannot be categorized (Schendan et al., 1998). Subjects pressed “1” to report that they categorized the object or, if not, they pressed “2,” as soon as possible after the picture appeared. A median split of the RTs to real and pseudo objects, separately, for correct responses (i.e., 1 for real objects, 2 for pseudo objects) separated these conditions into more (MI) and less (LI) impoverished conditions. Shown are real objects of an LI fish at fragmentation level 3, and MI piano at level 4, and an LI pseudo-fish at level 5, and MI pseudo-piano at level 4; note, sample stimuli reflect the consistent finding that more fragmented real objects are related to slower RTs, whereas more fragmented pseudo objects are related to faster RTs. Stimuli subtended 6 by 6 degrees of visual angle, on average, with a visual contrast of approximately 30% (dark pixels against a brighter background). (B) Custom 60-channel geodesic montage for EEG recording (Electrocap International). Circles show electrode locations. Numbers label each electrode. Approximate locations of 10–20 sites are shown in gray italics; site 57 is at Cz, site 60 is Oz; pairs 31–32, and 49–50 are 1 cm below the inion. (C) Response times to MI and LI real and pseudo objects. Error bars show the 95% confidence interval (Morey, 2008). *Significant impoverishment effect.
Mentions: A 2 × 2 repeated measures factorial design (Figure 2A) included factors of impoverishment (LI, MI) and object type (real, pseudo). General health history and Edinburgh Handedness (Oldfield, 1971) questionnaires were administered before each session. The ERP session started with instructions on the computer screen that subjects paraphrased aloud, and any misconceptions were corrected. They were instructed on the task, to maintain eye gaze on the fixation mark at the center of the screen, and blink only in the fixation period. They then received 10 practice trials using the experiment methods but different stimuli. On each experiment trial, a fixation period of 5400–5700 ms preceded each picture, which was presented for 1000 ms while subjects decided whether they could categorize each object. They pressed “1” as soon as they knew what the object was, or “2” if they did not know, as quickly as possible without sacrificing accuracy. Participants were informed that categorization would be challenging by design because the images were degraded. They were not informed that some objects were impossible to categorize (i.e., pseudo objects) and so, from the subjects' perspective, pseudo objects were just images that they could not categorize (i.e., possible “real” objects that they failed to categorize).

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