Electrophysiological Correlates of the Influences of Past Experience on Conscious and Unconscious Figure-Ground Perception

Persistent Link:
http://hdl.handle.net/10150/194981
Title:
Electrophysiological Correlates of the Influences of Past Experience on Conscious and Unconscious Figure-Ground Perception
Author:
Trujillo, Logan Thomas
Issue Date:
2007
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Figure-ground perception can be modeled as a competitive process with mutual inhibition between shape properties on opposite sides of an edge. This dissertation reports brain-based evidence that such competitive inhibition can be induced by access to preexisting object memory representations during figure assignment. Silhouette stimuli were used in which the balance of properties along an edge biased the inner, bounded, region to be seen as a novel figure. Experimental silhouettes (EXP) suggested familiar objects on their outside edges, which nonetheless appeared as shapeless grounds. Control silhouettes (CON) suggested novel shapes on the outside.In an initial task, human observers categorized masked EXP and CON silhouettes (175 ms exposure) as "novel" versus a third group of silhouettes depicting "familiar" objects on the inside. Signal detection measures verified that observers were unconscious of the familiar shapes within the EXP stimuli. Across three experiments, novel categorizations were highly accurate with shorter RTs for EXP than CON. Event-related potential (ERP) indices of observers' brain activity (Experiments 2 and 3) revealed a Late Potential (~300 ms) to be less positive for EXP than CON, a reduction in neural activity consistent with the presence of greater competitive inhibition for EXP stimuli. After controlling for stimulus confounds (Experiment 3), the P1 ERP (~100 ms) was larger for EXP than CON conditions, perhaps reflecting unconscious access to object memories.In a second task, observers were informed about familiar shapes suggested on the outsides of the EXP silhouettes before viewing masked (Experiments 1 and 2) or unmasked (Experiment 3) EXP and CON silhouettes to report whether they saw familiar shapes on the outside. Experiment 3 observers were more accurate to categorize CON vs. EXP stimuli as novel vs. familiar, with shorter RTs for EXP than CON. Task 2 N170 ERPs (~170 ms) were larger for EXP than CON in Experiments 2 and 3, reflecting the conscious perception of familiar shape in the outsides of EXP silhouettes. LP magnitudes were greater for CON than EXP, although ERP polarity was dependent on the presence/absence of a mask. Task 2 LPs may reflect competitive inhibition or longer processing times for CON stimuli.
Type:
text; Electronic Dissertation
Keywords:
Inhibition; Figure Assignment; Object Memory; Neural Feedback; Consciousness; ERP
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Psychology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Peterson, Mary A.
Committee Chair:
Peterson, Mary A.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleElectrophysiological Correlates of the Influences of Past Experience on Conscious and Unconscious Figure-Ground Perceptionen_US
dc.creatorTrujillo, Logan Thomasen_US
dc.contributor.authorTrujillo, Logan Thomasen_US
dc.date.issued2007en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractFigure-ground perception can be modeled as a competitive process with mutual inhibition between shape properties on opposite sides of an edge. This dissertation reports brain-based evidence that such competitive inhibition can be induced by access to preexisting object memory representations during figure assignment. Silhouette stimuli were used in which the balance of properties along an edge biased the inner, bounded, region to be seen as a novel figure. Experimental silhouettes (EXP) suggested familiar objects on their outside edges, which nonetheless appeared as shapeless grounds. Control silhouettes (CON) suggested novel shapes on the outside.In an initial task, human observers categorized masked EXP and CON silhouettes (175 ms exposure) as "novel" versus a third group of silhouettes depicting "familiar" objects on the inside. Signal detection measures verified that observers were unconscious of the familiar shapes within the EXP stimuli. Across three experiments, novel categorizations were highly accurate with shorter RTs for EXP than CON. Event-related potential (ERP) indices of observers' brain activity (Experiments 2 and 3) revealed a Late Potential (~300 ms) to be less positive for EXP than CON, a reduction in neural activity consistent with the presence of greater competitive inhibition for EXP stimuli. After controlling for stimulus confounds (Experiment 3), the P1 ERP (~100 ms) was larger for EXP than CON conditions, perhaps reflecting unconscious access to object memories.In a second task, observers were informed about familiar shapes suggested on the outsides of the EXP silhouettes before viewing masked (Experiments 1 and 2) or unmasked (Experiment 3) EXP and CON silhouettes to report whether they saw familiar shapes on the outside. Experiment 3 observers were more accurate to categorize CON vs. EXP stimuli as novel vs. familiar, with shorter RTs for EXP than CON. Task 2 N170 ERPs (~170 ms) were larger for EXP than CON in Experiments 2 and 3, reflecting the conscious perception of familiar shape in the outsides of EXP silhouettes. LP magnitudes were greater for CON than EXP, although ERP polarity was dependent on the presence/absence of a mask. Task 2 LPs may reflect competitive inhibition or longer processing times for CON stimuli.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectInhibitionen_US
dc.subjectFigure Assignmenten_US
dc.subjectObject Memoryen_US
dc.subjectNeural Feedbacken_US
dc.subjectConsciousnessen_US
dc.subjectERPen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePsychologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorPeterson, Mary A.en_US
dc.contributor.chairPeterson, Mary A.en_US
dc.contributor.committeememberAllen, John J.B.en_US
dc.contributor.committeememberKaszniak, Alfred W.en_US
dc.contributor.committeememberRyan, Leeen_US
dc.identifier.proquest2039en_US
dc.identifier.oclc659747120en_US
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