The visual system is among the best mapped neural systems in the brain. Despite this, fundamental questions remain about the processing architecture underlying visual experience, and what goes wrong in conditions like blindsight and aphantasia. Here we outline a simple anatomic-computational structure for visual processing by combining recent advances in the visual processing literature with a neuroscientifically derived minimal framework for reportable perceptual awareness. Throughout we charac…
Read moreThe visual system is among the best mapped neural systems in the brain. Despite this, fundamental questions remain about the processing architecture underlying visual experience, and what goes wrong in conditions like blindsight and aphantasia. Here we outline a simple anatomic-computational structure for visual processing by combining recent advances in the visual processing literature with a neuroscientifically derived minimal framework for reportable perceptual awareness. Throughout we characterize the functional operations of the perceptual and visual systems under consideration. For the constituent neural systems, we similarly outline their roles, and the evidence supporting their validity. Once established, we utilize this proposed visual processing framework to trace the processing constitutive of mental imagery generation, and then examine the specific neuro-computational aberrations which give rise to the phenomena of blindsight and aphantasia. In doing so we embrace Ian Phillips' call to take on the full scope of variability in human cognition, and share his view that distinct kinds of percepts are functionally distinguishable by their underlying dynamics. However, we disagree that blindsight and aphantasia are best understood as cases of degraded conscious perception. We instead propose that cases of function without direct awareness are indeed simply cases of function without direct awareness. We propose that blindsight involves genuinely unconscious processing by the visual system, and aphantasia reflects an inability to adequately utilize top-down signal flows to modulate visual cortex. We derive symptom profiles from the model and validate them against reported clinical cases, and close with three sets of testable predictions, including differential effects of transcranial stimulation across aphantasia subtypes and a proposed dissociation between the LIFG gateway mechanism and bottom-up perceptual processing, and a general discussion of what this system may tell us about consciousness and cognition.
