Some Neurology About Color Specializations (Meadows, 1974) Axial view IPL Fusiform V1

GIRKIN AND MILLER Surv Ophthalmol 45 (5) March–April 2001 Lingual and Fusiform Gyri: Ventral Occipital Cortex

Cerebral achromatopsia or dyschromatopsia Following a cortical lesion, a human subject loses specifically the ability to see the world in colour Appearance is ‘dirty shades of grey’ Often accompanied by a transient inability to recognize faces (prosopagnosia) No obvious loss of form vision measured by acuity The signals relayed to the brain are normal, but the mechanism used to construct color appearance is defective.

Examples of dissociation – A little Neurology Oliver Sacks patient suffered a car accident; artist for whom color vision was lost while pattern vision was retained There are instances in which color vision is spared, while form vision is lost: carbon monoxide poisoning (Wechsler, 1933); also SB and Michael May

Cortical Color Blind Perimetry (Meadows, 1978) Intensity 1Intensity 2

Munsell Organization

Munsell Page Example

Farnsworth-Munsell 100 Hue Test A method for determining color vision abnormalities and testing color discrimination. Provides reliable data which can be applied to many psychological and industrial color vision problems. The set consists of four trays containing a total of 85 removable color reference caps that have incremental hue variation on one side and are numbered on the reverse side. Color vision anomalies and color aptitude are detected by a subject's ability to place the color caps in hue order. The four trays are boxed in a wooden carrying case. Used by government and industry for over 50 years.

Color Blind Farnsworth-Munsell (Meadows, 1974) Protanope Deuteranope Tritanope (a) Cone loss(b) Cortical color blind (errors/2)

Li Fu Human Ventral Occipital Cortex, Near hV4, Responds Powerfully to Color Signals; Damage Can Cause A Hemifield Loss of Color Perception V3-ventral upper visual field hV4-hemifield Ventral Surface Human Brain

Lingual and Fusiform Gyri (McKeefry and Zeki, 1997)

Upper and Lower Visual Field Representatio n (V-Zeki)

Color Anomia (Meadows, 1978) Infer Parietal Lobule

Inferior Parietal Lobule

Classical Cone Specific Center- Surround Hypothesis (Hubel and Wiesel, 1966; Calkins and Sterling, 2001)

Anatomy: Midget Cell Surrounds Receive From All Cone Classes (Calkins and Sterling) H1 Horizontals receive non- selective L,M input Amacrine populations receive non-selective L,M input

Hypothesis: Midget Cone Inputs Differ With Eccentricity Central Peripheral

Small Bistratified (Calkins and Sterling)

Measurements of single unit responses in visual cortex to simple colored patterns

Let’s talk about action spectra in V4 (Zeki) Inhibitory Excitatory Method

Subject: WAP Visual Sensitivity and Opposing L-M signals: Eye-Same Contrast (%)

Eye-Different Condition Eye-Different Left eyeRight eye

Eye-different condition BWWAP JRSH

V1 V2d V2v V3d V3v PosteriorAnterior cm Retinotopic Areas in Human Occipital Lobe

2 -2 FMRI signal modulation (%) Time FMRI Signal Time Course Measure signal contrast needed to obtain criterion signal level Permits comparison with threshold psychophysics Criterion

Human V1: fMRI time (L,M) Iso-response Contour L-cone contrast (%) M-cone contrast 050 fMRI Contrast (%) Subject: WAP

Exchange measurements are a way to begin the exploration of color signals in human cortex (Zeki, many papers)

Color exchange principles Spatial structure is constant Achromatic (L+M+S) vs. Achromatic + Color (L-M, S – (L+M)) Subtractive: differential responses are due to color Time

Calcarine Ventral surface Color exchange ventral signal locations with respect to the visual areas (A v. A+C)

Visual area Foveal confluence V1 V2 V3 V3B V3A hV4 V7 Ventral surface Calcarine

We are now carrying out human-macaque comparisons using functional MRI (Wade, Augath, Logothetis, Wandell)