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P. Sehatpour, V.M. Zemon, S. Molholm, B. Higgins, A. Mehta, T. Schwartz, D.C. Javitt, J.J. Foxe; Perceptual Closure Processes During Object Recognition: An Integrative Investigation in Humans . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2438.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the spatiotemporal dynamics of perceptual closure processes. "Perceptual closure" refers to the neural processes responsible for "filling–in" missing information in the visual image under adverse viewing conditions (e.g., occlusion, poor lighting). Methods: A multi–pronged approach was adopted using high–density scalp electrical recordings (ERPs), human intracranial recordings, and functional magnetic resonance imaging (fMRI) while observers performed a perceptual closure task. Observers were presented randomly interspersed highly fragmented images and scrambled images. Fragmented images were calibrated to be ‘just’ recognizable as objects (i.e., perceptual closure was necessary), whereas the scrambled images were unrecognizable. Comparison of responses to these two stimulus classes revealed the neural processes underlying perceptual closure. The same event–related design was used for the ERP and the fMRI recordings with modifications to the interstimulus intervals to accommodate for the sluggishness of the hemodynamic response as compared to the electophysiologic response. A 3–Tesla system was used to acquire T2*–weighted echo–planar functional images (EPIs) emphasizing the blood oxygenation level dependent (BOLD) response. Scalp EEGs were acquired through a high–density 128 channel system. Intracranial recordings were made using grids and or strips of electrodes placed directly on the cortex and hippocampal depth electrodes. These electrodes were placed for clinical reasons and their number and distributions varied on an individual basis. Results: Analysis of the fMRI data revealed an object recognition system that mediates closure processes, the core of which consists of the lateral occipital complex (LOC). ERP recordings resulted in the well–characterized NCL component (for negativity associated with closure), a robust relative negativity over bilateral occipito–temporal scalp that occurs in the 230–400 ms timeframe (Doniger 2000, 2001). Inverse source analysis techniques and human intracranial recordings showed that NCL is localized to within LOC as defined by the fMRI recordings. This analysis helped to illustrate the temporal dynamics of the generators involved in perceptual closure. Conclusions: The lateral occipital complex is crucially involved in closure processing during object recognition, and through an integrative approach we illustrated the spatiotemporal dynamics of these processes.
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