Seeing without knowing: Operational principles along the early visual pathway.
Single cases may lead to unexpected hypotheses in psychology. We retrospectively analyzed single case studies that suggested organizational principles along the early visual pathway, which have remained unanswered until now.


METHODS
In spite of the inhomogeneity of sensitivity, paradoxically the visual field on the subjective level appears to be homogeneous; constancy of brightness of supra-threshold stimuli throughout the visual field is claimed to be responsible for homogeneity; specific summation properties of retinal ganglion cells are hypothesized to guarantee this effect.


METHODS
With a brain-injured patient having suffered a partial visual field loss it can be shown that color induction is a retinal phenomenon; lateral inhibitory processes at the level of amacrine cells are hypothesized as neural network. Third case: In a patient having suffered a bilateral occipital lobe infarction, some functional recovery has been demonstrated; divergence and convergence of projection in the ascending neural pathway are suggested as a structural basis for recovery. Slowed down binocular rivalry discloses a sequential mechanism in the construction of a visual percept. Fourth case: The pre-wired projection of the retina to the visual cortex in spite of a severe squint of one eye is confirmed, but paradoxically some local neuroplasticity is also suggested. Fifth case: Using habituation of local sensitivity in the visual field and its resetting by interhemispheric interactions as an experimental paradigm, it is suggested that spatial attention is controlled at the midbrain level. Sixth case: Observations on residual vision or "blindsight" support the hypothesis that the visual cortex is the one and only structure responsible for visual perception on a conscious level. The unifying principle of these retrospective analyses is that subjective visual phenomena can lead to unexpected but testable hypotheses of neural processing on the structural and functional level in the early visual pathway.
Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
Bin
B
Zhou
School of Psychological and Cognitive Sciences, Key Laboratory of Machine Perception (Ministry of Education), and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China.|Institute of Medical Psychology and Human Science Center, Ludwig-Maximilians-University, Munich, Germany.
Ernst
E
Pöppel
School of Psychological and Cognitive Sciences, Key Laboratory of Machine Perception (Ministry of Education), and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China.
Lingyan
L
Wang
Institute of Medical Psychology and Human Science Center, Ludwig-Maximilians-University, Munich, Germany.
Taoxi
T
Yang
Institute of Medical Psychology and Human Science Center, Ludwig-Maximilians-University, Munich, Germany.|Department of National IT System of Mental Health and Brain Monitoring, National Institute of Mental Health, Klecany, Czech Republic.|Department of Psychiatry and Medical Psychology, 3rd Faculty of Medicine, Charles University, Prague, Czech Republic.
Yuliya
Y
Zaytseva
School of Psychological and Cognitive Sciences, Key Laboratory of Machine Perception (Ministry of Education), and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China. baoyan@pku.edu.cn.|Institute of Medical Psychology and Human Science Center, Ludwig-Maximilians-University, Munich, Germany. baoyan@pku.edu.cn.
Yan
Y
Bao
D001288:Attention / Q000502:physiology; D001766:Blindness / Q000503:physiopathology; D020520:Brain Infarction / Q000503:physiopathology; D001930:Brain Injuries / Q000503:physiopathology; D003118:Color Perception; D005829:Geniculate Bodies / Q000502:physiology; D006801:Humans; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology; D012189:Retrospective Studies; D014793:Visual Cortex / Q000502:physiology; D014794:Visual Fields; D014795:Visual Pathways / Q000502:physiology*
attentional control; binocular rivalry; blindsight; brightness perception; color perception; consciousness; eccentricity effect; habituation; neuroplasticity; restitution of function