CORTICAL DYNAMICS OF OBJECT CATEGORIZATION AND RECOGNITION WITH CATEGORY EXEMPLARS.
Abstract: Two experiments investigated the time-course of object knowledge
subsystems and how they might help explain novel object categorization. Experiment 1
compared ERP repetition effects in a 3 study (same or different exemplars of repeated
categories, new category) x 2 typicality (high, low) design during category and recognition
decisions. Repetition effects for same repeated objects bu... read moret not different exemplars were
found on the frontopolar N3, putative index of form representations. Effects on a posterior
N400, thought to reflect amodal semantic representation, were found only when participants
categorized. A centrofrontal N3 did show generalization, but only for high typicality items
when participants were categorizing. Task differences were not found on the LPC /P600, even
when analyses were limited to correct recognition trials. For Experiment 2, people
categorized objects during an indirect memory test in a 2 repetition (new, old perceptually
similar category exemplar) x 2 naming (same or different subordinate name from study to
test) design. Results showed generalization to perceptually similar category exemplars on
the frontopolar N3. Repetition and naming did not interact, inconsistent with semantic
influence on object model selection. Taken together, these experiments show that distinct
subsystems represent different aspects of object knowledge. From ~ 150 - 350 ms,
form-specific representations from a PRS were active and indexed by the frontopolar N3, as
was a system that showed greater generalization to different exemplars which may reflect
mapping onto conceptual representations. From 300 -500 ms evidence for two types of
semantic representation, one modality specific (anterior N400) and one amodal (posterior
N400) was found. Representations active after 500 ms may reflect conscious recollection or
evaluation of memory match.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Psychology.
Advisor: Holly Taylor.
Committee: Phillip Holcomb, Robert Cook, Katherine Midgley, Marianna Eddy, and Haline Schendan.
Keywords: Cognitive Psychology, and Neurosciences.read less