Whole brain and primary visual cortex layer fMRI signatures of afterimage perception

2540 

Abstract Submission 

Sharif Kronemer¹, Micah Holness¹, Burak Akin¹, Javier Gonzalez-Castillo¹, Laurentius (Renzo) Huber², Paul Taylor¹, A. Morgan¹, Joshua Teves¹, Victoria Gobo¹, Daniel Handwerker¹, Peter Bandettini¹

¹National Institute of Mental Health, Bethesda, MD, ²Functional MRI Core Facility, National Institute of Mental Health, Bethesda, MD

Sharif Kronemer  
National Institute of Mental Health
Bethesda, MD

Micah Holness  
National Institute of Mental Health
Bethesda, MD

Burak Akin  
National Institute of Mental Health
Bethesda, MD

Javier Gonzalez-Castillo, PhD  
National Institute of Mental Health
Bethesda, MD

Laurentius (Renzo) Huber, PhD  
Functional MRI Core Facility, National Institute of Mental Health
Bethesda, MD

Paul Taylor  
National Institute of Mental Health
Bethesda, MD

A. Morgan  
National Institute of Mental Health
Bethesda, MD

Joshua Teves  
National Institute of Mental Health
Bethesda, MD

Victoria Gobo  
National Institute of Mental Health
Bethesda, MD

Daniel Handwerker, PhD  
National Institute of Mental Health
Bethesda, MD

Peter Bandettini, Ph.D.  
National Institute of Mental Health
Bethesda, MD

Afterimages are prolonged visual perceptions that typically follow adaptation to light stimulation. Afterimages have been a source of interest for centuries because they offer insight on the neural mechanisms of vision and conscious perception (Goethe, 1970). A lingering question is to what degree are retinal versus cortical processes involved in afterimages? Answering this query is significant for relating afterimages to other categories of conscious perception (e.g., imagery and hallucinations). While the retinal view of afterimages is dominant (e.g., the bleaching of photoreceptors; Brindley et al., 1962), there is evidence of post-retinal processes in the formation and modification of afterimages (e.g., Downey, 1901; Shimojo et al., 2001). Meanwhile, there is a limited number of neuroimaging studies on afterimages that would help to measure its central neural mechanisms. Accordingly, in the current experiment, we aimed to interrogate the whole brain and primary visual cortex layer fMRI signals underpinning afterimage perception.

Healthy, adult participants (N = 34) completed a visual perception task where participants were shown images and afterimages. Afterimages were induced by a human face silhouette image. In initial task phases, participants reported on the perceptual sharpness, contrast, and duration of their afterimages. Participant perception reporting accuracy was confirmed on images with known sharpness, contrast, and duration. The afterimage perception reports were used to reconstruct a mock afterimage: an image that perceptually-matched the sharpness and contrast overtime of each participants' afterimage. In the main task phase, participants reported the onset and offset of their mock and real afterimages, during simultaneous eye-tracking (EyeLink 1000 Plus; SR Research, Inc.) and whole brain 7T fMRI was recorded (BOLD; voxel size: 1.2mm3; TR: 1000ms; Siemens, Inc.). A subset of participants (N = 12) also completed the main task while recording primary visual cortex (V1) cortical-layer resolution 7T fMRI (BOLD/VASO; voxel size 0.8mm3; TR: 3000ms, Siemens, Inc.). Analysis were completed with MATLAB (MathWorks, Inc.) and Analysis of Functional Neuroimages (AFNI) software.

The inducer stimulus reliably generated afterimages (>75% afterimage perception rate). Participants accurately reported on the image sharpness, contrast, and duration. The afterimage perceptual reports were sufficiently accurate such that a majority of participants (>90%) did not distinguish between their real and mock afterimages, even when they were presented side-by-side. Whole brain fMRI findings show that the mock and real afterimages recruit many of the same subcortical and cortical networks (Figure 1), including sensory regions (e.g., VI and fusiform gyrus [FG]), arousal and neuromodulatory regions (e.g., thalamus and brainstem), salience regions (e.g., insula and anterior cingulate cortex), and attention/detection regions (e.g., posterior parietal cortex [PPC] and dorsal lateral prefrontal cortex [DLPFC]). However, the mock afterimage showed greater fMRI responses relative to the real afterimage in several regions (e.g., FG, PPC, and DLPFC), and real afterimage revealed fMRI decreases absent in the mock afterimage, particularly in the prefrontal cortex (Figure 2). Preliminary analyses of the V1 cortical layer fMRI responses suggest similar dynamics between the mock and real afterimages.

As far as we know, the current investigation represents the first whole brain and layer fMRI study of human afterimage perception. These findings suggest that afterimages engage similar whole brain networks as normal sensory vision. However, in some brain areas, there are differences between mock and real afterimage conscious perception. Future analyses will interrogate subject-level dynamics (e.g., fMRI responses for participants with more or less vivid afterimage perception).

BOLD fMRI ²

Consciousness and Awareness

Perception: Visual ¹

Consciousness

Cortical Layers

FUNCTIONAL MRI

HIGH FIELD MR

NORMAL HUMAN

Perception

Vision