The Art of Seeing and Painting

The human urge to represent the three-dimensional world using two-dimensional pictorial representations dates back at least to Paleolithic times. Artists from ancient to modern times have struggled to understand how a few contours or color patches on a flat surface can induce mental representations of a three-dimensional scene. This article summarizes some of the recent breakthroughs in scientifically understanding how the brain sees that shed light on these struggles. These breakthroughs illustrate how various artists have intuitively understand paradoxical properties about how the brain sees, and have used that understanding to create great art. These paradoxical properties arise from how the brain forms the units of conscious visual perception; namely, representations of three-dimensional boundaries and surfaces. Boundaries and surfaces are computed in parallel cortical processing streams that obey computationally complementary properties. These streams interact at multiple levels to overcome their complementary weaknesses and to transform their complementary properties into consistent percepts. The article describes how properties of complementary consistency have guided the creation of many great works of art.

Contribution of S opponent cells to color appearance

We measured the regions in isoluminant color space over which observers perceive red, yellow, green, and blue and examined the extent to which the colors vary in perceived amount within these regions. We compared color scaling of various isoluminant stimuli by using large spots, which activate all cone types, to that with tiny spots in the central foveola, where S cones, and thus S opponent (So) cell activity, are largely or entirely absent. The addition of So input to that from the L and M opponent cells changes the chromatic appearance of all colors, affecting each primary color in different chromatic regions in the directions and by the amount predicted by our color model. Shifts from white to the various chromatic stimuli we used produced sinusoidal variations in cone activation as a function of color angle for each cone type and in the responses of lateral geniculate cells. However, psychophysical color-scaling functions for 2° spots were nonsinusoidal, being much more peaked. The color-scaling functions are well fit by sine waves raised to exponents between 1 and 3. The same is true for the color responses of a large subpopulation of striate cortex cells. The narrow color tuning, the discrepancies between the spectral loci of the peaks of the color-scaling curves and those of lateral geniculate cells, and the changes in color appearance produced by eliminating So input provide evidence for a cortical processing stage at which the color axes are rotated by a combination of the outputs of So cells with those of L and M opponent cells in the manner that we postulated earlier. There seems to be an expansive response nonlinearity at this stage.

Spotting the difference : identifying player opponent preferences in FPS games

This paper describes a study designed to understand player responses to artificially intelligent opponents in multi-player First Person Shooter games. It examines the player's ability to tell the difference between artificially intelligent opponents and other human players, and investigates the players' perceptions of these opponents. The study examines player preferences in this regard and identifies the significance of the cues and signs players use to categorise an opponent as artificial or human.

Voltammetric, spectroscopic, and microscopic investigations of electrocrystallized forms of semiconducting AgTCNQ (TCNQ=7,7,8,8-tetracyanoquinodimethane) exhibiting different morphologies and colors

Chemically synthesized AgTCNQ exists in two forms that differ in their morphologies (needles and microcrystals) and colors (red and blue). It is now shown that both forms exhibit essentially indistinguishable X-ray diffraction, spectroscopic, and thermochemical data, implying that they are not separate phases, as implied in some literature. Electrochemical reduction of TCNQ((MeCN)) in the presence of Ag+((MeCN)) generates both red and blue AgTCNQ. On glassy carbon, platinum, or indium tin oxide electrodes and at relatively positive deposition potentials, slow growth of high aspect ratio, red needle AgTCNQ crystals occurs. After longer times and at more negative deposition potentials, blue microcrystalline AgTCNQ thin films are favored. Blue AgTCNQ is postulated to be generated via reduction of a Ag+\[(TCNQ(center dot-))(TCNQ)]((MeCN)) intermediate. At even more negative potentials, Ag-(metal) formation inhibits further growth of AgTCNQ. On a gold electrode, Ag-(metal)) deposition occurs at more positive potentials than on the other electrode materials examined. However, surface plasmon resonance data indicate (hat a small potential region is available between the stripping of Ag-(metal)) and the oxidation of TCNQ(center dot-)(MeCN) back to TCNQ(MeCN) where AgTCNQ may form. AgTCNQ in both the red and blue forms also can be prepared electrochemically on a TCNQ((s)) modified electrode in -0.1 M AgNO3(aq) where deposition of Ag(m,,,I) onto the TCNQ((s)) crystals allows a charge transfer process to occur. However, the morphology formed in this solid-solid phase transformation is more difficult to control.

Selectivity of human retinotopic visual cortex to S-cone-opponent, L/M-cone-opponent and achromatic stimulation

Our aim was to make a quantitative comparison of the response of the different visual cortical areas to selective stimulation of the two different cone-opponent pathways [long- and medium-wavelength (L/M)- and short-wavelength (S)-cone-opponent] and the achromatic pathway under equivalent conditions. The appropriate stimulus-contrast metric for the comparison of colour and achromatic sensitivity is unknown, however, and so a secondary aim was to investigate whether equivalent fMRI responses of each cortical area are predicted by stimulus contrast matched in multiples of detection threshold that approximately equates for visibility, or direct (cone) contrast matches in which psychophysical sensitivity is uncorrected. We found that the fMRI response across the two colour and achromatic pathways is not well predicted by threshold-scaled stimuli (perceptual visibility) but is better predicted by cone contrast, particularly for area V1. Our results show that the early visual areas (V1, V2, V3, VP and hV4) all have robust responses to colour. No area showed an overall colour preference, however, until anterior to V4 where we found a ventral occipital region that has a significant preference for chromatic stimuli, indicating a functional distinction from earlier areas. We found that all of these areas have a surprisingly strong response to S-cone stimuli, at least as great as the L/M response, suggesting a relative enhancement of the S-cone cortical signal. We also identified two areas (V3A and hMT+) with a significant preference for achromatic over chromatic stimuli, indicating a functional grouping into a dorsal pathway with a strong magnocellular input.

Conflict-Free Coloring for Rectangle Ranges Using O(n.382) Colors

Given a set of points P ⊆ R2, a conflict-free coloring of P w.r.t. rectangle ranges is an assignment of colors to points of P, such that each nonempty axisparallel rectangle T in the plane contains a point whose color is distinct from all other points in P ∩ T . This notion has been the subject of recent interest and is motivated by frequency assignment in wireless cellular networks: one naturally would like to minimize the number of frequencies (colors) assigned to base stations (points) such that within any range (for instance, rectangle), there is no interference. We show that any set of n points in R2 can be conflict-free colored with O(nβ∗+o(1)) colors in expected polynomial time, where β∗ = 3−√5 2 < 0.382.

Sequence Characterization of the MC1R Gene in Yak (Poephagus grunniens) Breeds with Different Coat Colors

Melanocortin 1 receptor (MC1R) gene plays a key role in determining coat color in several species, including the cattle. However, up to now there is no report regarding the MC1R gene and the potential association of its mutations with coat colors in yak (

Opponent appetitive-aversive neural processes underlie predictive learning of pain relief.

Termination of a painful or unpleasant event can be rewarding. However, whether the brain treats relief in a similar way as it treats natural reward is unclear, and the neural processes that underlie its representation as a motivational goal remain poorly understood. We used fMRI (functional magnetic resonance imaging) to investigate how humans learn to generate expectations of pain relief. Using a pavlovian conditioning procedure, we show that subjects experiencing prolonged experimentally induced pain can be conditioned to predict pain relief. This proceeds in a manner consistent with contemporary reward-learning theory (average reward/loss reinforcement learning), reflected by neural activity in the amygdala and midbrain. Furthermore, these reward-like learning signals are mirrored by opposite aversion-like signals in lateral orbitofrontal cortex and anterior cingulate cortex. This dual coding has parallels to 'opponent process' theories in psychology and promotes a formal account of prediction and expectation during pain.

Controlled Synthesis of Ln(3+) (Ln = Tb, Eu, Dy) and V5+ Ion-Doped YPO4 Nano-/Microstructures with Tunable Luminescent Colors

YPO4 nano/microcrystals with multiform crystal phases and morphologies, such as hexagonal nano/submicroprisms, spherical-like nanoparticles, and nanorods with different length/diameter ratios as well as tetragonal nanospindles, have been synthesized via a facile hydrothermal route. A series of controlled experiments indicate that the pH values in the initial solution, phosphorus sources, and the organic additive trisodium citrate (Cit(3-)) are responsible for crystal phase and shape determination of final products. It is found that Cit(3-) as a ligand and shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of various geometries of the final products. The possible formation mechanisms for products with diverse architectures have been presented.

Realization of high efficiency microcavity top-emitting organic light-emitting diodes with highly saturated colors and negligible angular dependence

An alternative way to optimize the emission characteristics of a microcavity top-emitting organic light-emitting diode (TOLED) based on a simple device structure is demonstrated via combining a comprehensive theoretical analysis in the microcavity effects with the experimental modification in the carrier injection of both electrodes. It can be seen that the resulting TOLED exhibits much higher efficiencies and a more saturated color than those of the corresponding conventional bottom-emitting device, as well as hardly detectable color shift with viewing angles. Such a strategy may be more feasible in practical application for active-matrix organic light-emitting diode displays.

Cerebellar Learning in an Opponent Motor Controller for Adaptive Load Compensation and Synergy Formation

This paper shows how a minimal neural network model of the cerebellum may be embedded within a sensory-neuro-muscular control system that mimics known anatomy and physiology. With this embedding, cerebellar learning promotes load compensation while also allowing both coactivation and reciprocal inhibition of sets of antagonist muscles. In particular, we show how synaptic long term depression guided by feedback from muscle stretch receptors can lead to trans-cerebellar gain changes that are load-compensating. It is argued that the same processes help to adaptively discover multi-joint synergies. Simulations of rapid single joint rotations under load illustrates design feasibility and stability.

Equilibria and Dynamics of a Neural Network Model for Opponent Muscle Control

One of the advantages of biological skeleto-motor systems is the opponent muscle design, which in principle makes it possible to achieve facile independent control of joint angle and joint stiffness. Prior analysis of equilibrium states of a biologically-based neural network for opponent muscle control, the FLETE model, revealed that such independent control requires specialized interneuronal circuitry to efficiently coordinate the opponent force generators. In this chapter, we refine the FLETE circuit variables specification and update the equilibrium analysis. We also incorporate additional neuronal circuitry that ensures efficient opponent force generation and velocity regulation during movement.

Neural Representations for Sensory-Motor Control I: Head-Centered 3-D Target Positions from Opponent Eye Commands

This article describes how corollary discharges from outflow eye movement commands can be transformed by two stages of opponent neural processing into a head-centered representation of 3-D target position. This representation implicitly defines a cyclopean coordinate system whose variables approximate the binocular vergence and spherical horizontal and vertical angles with respect to the observer's head. Various psychophysical data concerning binocular distance perception and reaching behavior are clarified by this representation. The representation provides a foundation for learning head-centered and body-centered invariant representations of both foveated and non-foveated 3-D target positions. It also enables a solution to be developed of the classical motor equivalence problem, whereby many different joint configurations of a redundant manipulator can all be used to realize a desired trajectory in 3-D space.

High-sensitivity rod photoreceptor input to the blue-yellow color opponent pathway in macaque retina.

Small bistratified cells (SBCs) in the primate retina carry a major blue-yellow opponent signal to the brain. We found that SBCs also carry signals from rod photoreceptors, with the same sign as S cone input. SBCs exhibited robust responses under low scotopic conditions. Physiological and anatomical experiments indicated that this rod input arose from the AII amacrine cell-mediated rod pathway. Rod and cone signals were both present in SBCs at mesopic light levels. These findings have three implications. First, more retinal circuits may multiplex rod and cone signals than were previously thought to, efficiently exploiting the limited number of optic nerve fibers. Second, signals from AII amacrine cells may diverge to most or all of the approximately 20 retinal ganglion cell types in the peripheral primate retina. Third, rod input to SBCs may be the substrate for behavioral biases toward perception of blue at mesopic light levels.

The Voyage of Impressionism in Three Violin Recitals: To See the World in Different Colors

Impressionism serves as the transition between romantic and modern music. This dissertation examines the varying characteristics and colors of Impressionism in the works of late-romantic French composers, French Impressionistic composers, and composers with Impressionistic influence from countries other than France. Violin Sonata in g minor, L. 140 (1917) is the last work composed by Claude Debussy. The impressionistic characters in this work includes the ambiguous yet innovative and variant sonority and form. As a work also written in 1917, Ottorino Respighi's Violin Sonata in b minor is deeply rooted in Italian Romanticism. Some of the Impressionistic characters can be found in the second movement where the harmonies are in parallel motion. César Franck, a forerunner of impressionism, heavily influenced Debussy with the use of cyclic form. The Violin Sonata in A major (1886) is rich in harmonic language. Ernest Chausson's works mark the transition between Franck and Debussy. The Poème portrays a love story, Song of Love Triumphant by Turgenev. The work is a symphonic poem for violin and orchestra. The Mythes, Op. 30 (1915) by Karol Szymanowski is based on Greek mythology. Ravel's Sonata for Violin and Cello (1922), dedicated to Debussy, points to the future with a sophisticated harmonic language extending into atonality, spare texture, and expanded palate of impressionistic colors and techniques. Ernest Bloch's Violin Sonata No. 1 (1920) portrays the feeling of torment. Beneath the soaring cries of the violin, the harmonic sonority of Impressionism are present. Gabriel Fauré's Violin Sonata No. 1 in A major, op. 13 (1876) is the earliest work of this project. The scherzo movement became a prototype for future scherzo movements for Ravel and Debussy. Ravel's Tzigane (1924), at once a paragon of French impressionism, a delightful gypsy-style dance-fantasy, and a breathtaking virtuoso piece, is the perfect conclusion to my dissertation project. The pieces discussed above were presented in three recitals. Compact disc recordings of these recitals are available in the Michelle Smith Performing Arts Library of the Clarice Smith Performing Arts Center at the University of Maryland.