Date of Award

2018

Document Type

Open Access Dissertation

Department

Psychology

Sub-Department

College of Arts and Sciences

First Advisor

Jessica Green

Abstract

This dissertation explores the occipital lobe’s response to non-visual inputs, and whether this responsivity partitions into separate localization and identification pathways as seen with visual inputs. We hypothesized that occipital areas may merely prefer visual inputs, while maintaining similar task-based sensory recruitment in response to other senses. Our secondary hypothesis was that the robust occipital activation seen in late-blind participants stems at least initially from standard connections present even in the typically sighted, and that these standard connections are functionally utilized by the typically sighted in spatially relevant non-visual analyses. Our initial literature review supported our hypotheses that the occipital lobe is a highly plastic, cross-modally responsive area and that recruitment of occipital areas in the blind stems from the strengthening of existing multi-modal connections.

To further explore our topic, we conducted meta-analyses on fMRI and PET studies reporting occipital response to non-visual input in congenital/early-blind participants and/or blindfolded but otherwise typically sighted participants. Through these analyses, we noted significant extrastriate activations for blind participants beyond that seen with sighted participants, which lent support to our task-based wiring hypothesis. We also observed common activations between blind and sighted participants, notably including activation in striate cortex, which supported the notion of functional connections to occipital lobe from other sensory inputs regardless of the presence or lack of visual input.

Finally, we conducted an fMRI study investigating the effects of short-term blindfolding on occipital responsivity to auditory stimuli in typically sighted participants. We did not observe greater activation in participants blindfolded for 45 minutes than we observed with non-blindfolded participants, but our study did further highlight the functional connections present between non-visual senses and the occipital lobe, and again supported our task-based wiring hypothesis.

Overall, we found support for the occipital lobe being multi-modally reactive, even in typically sighted individuals. We also found evidence of task-based wiring being maintained regardless of the sensory modality being responded to, and of the likelihood that these functional non-visual connections are at least initially what give rise to the widespread occipital activation observed with blind participants in response to non-visual stimuli.

Rights

© 2018, William J. Brixius

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