Author ORCID Identifier
https://orcid.org/0000-0003-0735-8040
Date of Award
Winter 2-1-2025
Document Type
Thesis (Ph.D.)
Department or Program
Cognitive Neuroscience
First Advisor
Viola S. Störmer
Abstract
Visual attention refers to the mechanisms by which relevant visual information, such as location, simple features (e.g., color, orientation), and objects, is selected and prioritized for further processing. The current dissertation investigates capacity limitations on spatial and feature–based attention in early visual processing and behavioral performance. Specifically, I examined whether attention could be efficiently tuned across narrow and broad ranges of locations and colors, or even be split across noncontiguous locations in the case of spatial attention. I used several behavioral paradigms and frequency–tagging methods in electroencephalography (EEG) to illustrate the effects of narrowing or broadening the attentional focus on performance and early visual processing. My findings indicate that the spatial focus of attention can modulate the neural gain of early visual processing across varying ranges of locations but cannot be split into discrete spotlights within a visual quadrant. Furthermore, I found that feature–based attention can flexibly ‘zoom’ in and out across continuous narrow and broad ranges in color space with no performance cost. Interestingly, measures of early visual-cortical processing indicated a cost in neural gain when attention was directed to broader ranges of colors — drawing parallels to the previously reported processing cost in spatial attention. However, this cost at early processing stages appears to be compensated for at later stages, leading to overall no cost in behavioral performance. In sum, the current dissertation provides novel evidence for how spatial and feature–based attention can be tuned across varying ranges in location and feature space and demonstrates that each type of attention is constrained by the unique format of the sensory representations over which it operates.
Original Citation
Chapter 1:
Mert Özkan, Viola Störmer; When spatial attention cannot be divided: Quadrantic enhancement of early visual processing across task-Relevant and irrelevant locations. Imaging Neuroscience 2024; 2 1–18. doi: https://doi.org/10.1162/imag_a_00194
Recommended Citation
Özkan, Mert, "BEHAVIORAL AND NEURAL EFFECTS OF DISTRIBUTING VISUAL ATTENTION ACROSS LOCATION AND FEATURE SPACE" (2025). Dartmouth College Ph.D Dissertations. 323.
https://digitalcommons.dartmouth.edu/dissertations/323
