[Abstract Title]. - Society for Neuroscience

Authors: *S. IWAKI 1 , J. W. BELLIVEAU 2 ;
1 Inst. Human Sci. & Biol Engineer, AIST, Ikeda, Osaka, Japan; 2 Mass Gen. Hosp., Boston, MA
Abstract: Two-dimensional motions of the retinal images were known to be an important cue to
perceive 3-D structure of objects. Recent neuroimaging studies implicate both the dorsal and
ventral visual pathways, as well as motion perception area MT, in the perception of 3D structure
from 2D motion (3D-SFM). However, the neural dynamics underlying the reconstruction of a 3D
object from 2D optic flow is not known. Here we combined neuromagnetic
magnetoencephalography (MEG) and hemodynamic functional MRI (fMRI) measurements to
investigate the spatiotemporal brain dynamics during 3D-SFM.
We manipulated parametrically the coherence of randomly moving groups of dots to create
different levels of 3D perception and to study the associated changes in brain activity.
Neuromagnetic signals were measured with a 306-channel MEG system. The fMRI scanning
was conducted using a 3-T scanner with the EPI imaging sequence. The results of the fMRI
analysis were used to impose plausible constraints on the MEG inverse calculation using the
„weighted‟ minimum-norm approach to improve spatial resolution of the spatio-temporal activity
estimates.
The infero-temporal (IT), parieto-occipital (PO), and intraparietal (IP) regions showed at
different latencies increased neural activity during highly coherent motion conditions in which
subjects perceived a robust 3D object. Causality analysis between these regions indicated a
significant causal influence from IP to IT and from IT to PO only in conditions where subjects
perceived a robust 3D object. Current results suggest that the perception of a 3D object from 2D
movement includes integration of global motion and 3D mental image processing as well as
object recognition that are accomplished by interactions between the dorsal and ventral visual
pathways.
Disclosures: S. Iwaki , None; J.W. Belliveau, None.
Poster
261. Object and Faces: Neuronal Representation I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 261.2/BB33
Topic: D.04.j. Processing of objects and faces
Support: NIH MH64043
Title: Object representations in monkey posterior parietal cortex