Author : Daniel E. Berman
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (114 download)
Book Synopsis Representations of Spatial Frequency, Depth, and Higher-level Image Content in Human Visual Cortex by : Daniel E. Berman
Download or read book Representations of Spatial Frequency, Depth, and Higher-level Image Content in Human Visual Cortex written by Daniel E. Berman and published by . This book was released on 2018 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The human visual system has been studied in great detail for millennia, but there are substantial, unanswered questions regarding the underlying characteristics of such an important sensory system. Many of these unanswered questions involve the neural correlates in which low-level features are processed in higher-level visual areas. Here, we use functional magnetic resonance imaging (fMRI) to address some of these questions concerning depth and spatial frequency perception in order to elucidate upon such fundamental aspects of visual processing and the mechanisms in which we are able to perceive the world around us. In Chapter 2, we examine the neural correlates of scene content with regards to the spatial frequency contained in these scenes. It has been long debated whether low or high spatial frequencies are what primarily represent the content of a scene and how different scene selective areas such as parahippocampal place area (PPA), retrospenial cortex (RSC) and occipital place area (OPA) process this component of the image we are viewing. Both low and high spatial frequencies contribute to scene representations, but what we find using both univariate and multivariate pattern analysis (MVPA) is that scene content is primarily represented throughout the majority of visual cortex via high spatial frequency information. Interestingly, we find that the posterior portion of PPA may have a unique role in processing low-level features like spatial frequency. Next, we address depth perception, another element of our visual system that is not fully understood. In Chapter 3 we examine whether category-selective areas such as scene-selective areas PPA, RSC and OPA, object-selective area lateral occipital cortex (LOC), face-selective areas fusiform face area (FFA) and occipital face area (OFA), and motion area (MT), are sensitive to a stimulus’ position-in-depth. We find that the scene areas prefer stimuli both behind and in front of fixation, while areas MT and LOC prefer front stimuli. Finally, in Chapter 4 we will examine whether depth representations are organized in a topographical (or “map-like”) manner. Much like classic retinotopic maps defined throughout visual cortex that are based on polar angle and eccentricity measurements utilizing 2-dimensional stimuli, we also find “depthotopic” maps using analogous methodology and analyses, known as phase-encoding mapping, The main modification is that our stimulus periodically cycles through different positions in depth instead of the x and y coordinates of visual field. These experiments provide us with a greater understanding of the neural correlates in which spatial frequency and depth are processed in high-level areas of human visual cortex.
