Spectral sensitivity of cones “Blue” cones “Green” cones “Red” cones ˙ Three types of opsins ˙ Color blindness is caused by lack of one or more cone types Relateive response Wavelength (nm) Figure by MIT OCW. After figure 9.20 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Color space is 3d ˙ Any color can be synthesized by mixing three primary colors. ˙ Young-Helmholtz trichromacy theory Image removed due to copyright reasons. Please see figure 9-21 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Retinal ganglion cells Output cells of the retina Send a million axons in the optic nerve Background rate of spiking Rate of spiking is modulated up or down by visual stimulation

Visual neurophysiology Anesthetized cat Video: visual stimulus seen by cat Audio: extracellular recording

Receptive field The area of retina (or of visual space) in which a stimulus can cause changes in the activity of a neuron. The “preferred stimulus” is that which causes the most increase in rate of action potential firing.

Center-surround antagonism OFF-center ganglion Cell output: Ganglion cell Receptive field Patch of retina Center Surround Dark spot Figure by MIT OCW. After figures 9.23 a, b, and c in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Visual stimuli Moving spot Flashed spot Annulus Spot with changing ciameter Moving bar

Transient vs. sustained M-type Ganglion cell (ON center) P-type Ganglion cell (ON center) Light in receptive field center ON OFF Action potentials per second note: offset of visual stimulus can lead to suppression of spiking below background rate (not shown here) Figure by MIT OCW. A fter figure 9.27 in: B ear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

P and M ganglion cells ˙ Smaller P-type (90%) ˙ Larger M-type (5%) ˙ Sustained ˙ Stimulus form ˙ Color-opponent ˙ Larger M-type (5%) ˙ Transient ˙ Stimulus movement Figure by MIT OCW. After figure 9.26 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Color aftereffect ˙ Psychological evidence of red-green and blue-yellow opponency ˙ Hering’s opponent process theory Figure by MIT OCW. After figure 9.29 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Neural basis of color opponency Images removed due to copyright reasons. Please see figure 9.28 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Dual process theory Resolution of the debate with a hybrid theory Photoreceptors - Young-Helmholtz trichromacy Ganglion cells - Hering color opponency Further reading: S.E. Palmer, Vision Science, MIT Press (1999).

Sensitivity to spatial differences Four categories of OFF-center ganglion cells responding to an edge Ganglion cell Receptive field OFF-center ganglion Cell output: Patch of retina Center Surround Responses of cells near the edge a exaggerated contrast-enhancement Dark spot Figure by MIT OCW. After figure 9.24 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Simultaneous contrast illusion Figure by MIT OCW. After figure 9.25 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Mach and Chevreul

Lateral inhibition Horizontal cells Amacrine cells Images removed due to copyright reasons. Please see figures 9.22 a, b, and c in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Convolution Mathematical idealization of retinal computation Image removed due to copyright reasons.

Engineering applications Silicon retinas - Kwabena Boahen (U penn) Retinal prosthetics - John Wyatt (MIT)

Central visual system

Retinofugal projection Eye Optic Nerve Optic Chiasm Stalk of Pituitary Gland Optic Tract Cut Surface of Brain Stem Figure by MIT OCW. After figure 10.2 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Right and left visual hemifields Binocular Visual Field Fixation Point Right Visual Hemifield Left Visual Hemifield Right Eye Right Optic Nerve Left Eye Right Optic Tract Left Optic Nerve Left Optic Tract Optic Chiasm ˙ The left visual hemifield is “viewed” by the right hemisphere, and vice versa. Figure by MIT OCW. After figure 10.3 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964

Retinogeniculocortical pathway Retina LGN V1 pathway for conscious visual perception Images removed due to copyright reasons. Please see figures 10.4 a and b in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Lateral geniculate nucleus ˙ dorsal thalamus ˙ major targets of optic tracts Images removed due to copyright reasons. Please see figure 10.8 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

Retinotopy Neighboring retinal cells project to neighboring LGN cells. There are maps of visual space in the LGN. Magnification of map for central vision.

LGN input is segregated Left LGN Right LGN Left Temporal Retina Left Nasal Retina Right Temporal Retina Right Nasal Retina ˙ contra: layers 1,4,6 ˙ ipsi: layers 2,3,5 ˙ retinotopic map in each layer ˙ maps are aligned Figure by MIT OCW. After figure 10.9 in: Bear, Mark F., Barry W. Connors, and Michael A. Paradiso. Neuroscience: Exploring the Brain. 2nd ed. Baltimore, Md.: Lippincott Williams & Wilkins, 2001. ISBN: 0683305964.

LGN function?? Receptive fields like retinal ganglion cells 80% of excitatory synapses from conrtex Neuromodulatory input - alertness - attention - sleep