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October, 2006
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Eye Movements: Voluntary or reflex-controlled movements of the eye.


JoVE 10280

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Human vision depends on light-sensitive neurons that are arranged in the back of the eye on a tissue called the retina. The neurons, called the rods and cones because of their shapes, are not uniformly distributed on the retina. Instead, there is a region in the center of the retina called the macula where cones are densely packed, and especially so in a central sub-region of the macula called the fovea. Outside the fovea there are virtually no cones, and rod density decreases considerably with greater distance from the fovea. Figure 1 schematizes this arrangement. This kind of arrangement is also replicated in the visual cortex: Many more cells represent stimulation at the fovea compared to the periphery. Figure 1. Schematic depiction of the human eye and the distribution of light-sensitive receptor cells on the retina. The pupil is the opening in the front of the eye that allows light to enter. Light is then focused onto the retina, a neural tissue in the back of the eye that is made of rods and cones, light-sensitive cells. At the center of the retina is the macula, and in

 Sensation and Perception

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates

1McGovern Institute, Massachusetts Institute of Technology, 2Harvard-MIT Division of Heath Sciences and Technology, 3Department of Anesthesiology, Duke University Medical Center, 4Department of Biology, Massachusetts Institute of Technology, 5Division of Pharmacoengineering and Molecular Pharmaceutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, 6Media Lab and Department of Biological Engineering, Massachusetts Institute of Technology, 7Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology

JoVE 56330


Interictal High Frequency Oscillations Detected with Simultaneous Magnetoencephalography and Electroencephalography as Biomarker of Pediatric Epilepsy

1Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 3Division of Epilepsy Surgery, Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, 4Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School

JoVE 54883


Color Afterimages

JoVE 10194

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Human color vision is impressive. People with normal color vision can tell apart millions of individual hues. Most amazingly, this ability is achieved with fairly simple hardware.

Part of the power of human color vision comes from a clever bit of engineering in the human brain. There, color perception relies on what is known as an 'opponent system.' This means that the presence of one kind of stimulus is treated as evidence for the absence of another, and vice versa; absence of one kind of stimulus is taken as evidence for the presence of the other. In particular, in the human brain there are cells that fire both when they receive signals to suggest that blue light is present, or when they do not receive signals suggesting yellow light. Similarly, there are cells that fire in the presence of yellow or the absence of blue. Blue and yellow are thus treated as opponent values in one dimension, and can be thought of as negative versus positive values on one axis of a Cartesian plane. If a stimulus is characterized as having a negative value on that axis, it can't also have a positive value. So, if it is characterized as yellow, it can't also be characterized as blue. Similarly, green and red (or really, magenta), o

 Sensation and Perception

Brain Imaging Investigation of the Neural Correlates of Emotion Regulation

1Department of Psychology, University of Illinois, Urbana-Champaign, 2Department of Computing Science, University of Alberta, Edmonton, 3Department of Psychiatry, University of Alberta, Edmonton, 4Department of Psychology, University of Alberta, Edmonton, 5Centre for Neuroscience, University of Alberta, Edmonton, 6Neuroscience Program, University of Illinois, Urbana-Champaign, 7Beckman Institute, University of Illinois, Urbana-Champaign

JoVE 2430


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