Color and Motion

From humans to insects, color and motion information are thought to be channeled through separate neural pathways for efficient visual processing, but it remains unclear if and how these pathways interact in improving perception of moving colored stimuli. By using sophisticated Drosophila genetics, intracellular electrophysiology, two-photon imaging, and behavioral experiments, Trevor Wardill et al. found that early in the processing stage, color photoreceptors influence the motion pathway and that this input improves the flies' optomotor performance in a flight simulator.

Read the paper Multiple Spectral Inputs Improve Motion Discrimination in the Drosophila Visual System in Science, 18 May 2012: Vol. 336 no. 6083 pp. 925-931 DOI: 10.1126/science.1215317.

do not fear

Words displayed in large fonts elicit stronger emotional responses, according to a new study. Mareike Bayer, Werner Sommer, and Annekathrin Schacht measured brain activity in 25 adults while showing them 72 emotionally positive, negative, and neutral words. They included words for gift, death, and chair. The team displayed the words in either 28-point or 125-point Arial font. Volunteers displayed stronger emotion-related brain activity 10 milliseconds earlier for the larger font size versus the smaller one, the authors reported online yesterday in PLoS ONE (open access). What's more, emotional signals elicited by the larger font size lasted a total of 180 milliseconds longer. The results are similar to emotional responses to large and small versions of pictures with fearful, disgusting, or sex-related content. Pictures hold biological relevance for people, since a big photo of a predator probably signals proximity to you. Similar emotional effects on font sizes probably reflect the importance language holds in our society, the authors speculate.

Lou Silverstein

In the mid-80s, when we were building up the new digital color research area at PARC, we invited as many color scientists active in digital reproduction as we could. We had two motives: scope the field and identify potential candidates to hire.

One visitor stood out for his deep knowledge both in color vision science and in the mathematical modeling of reproduced color. With his tall slender figure he was immediately recognizable, and his soft voice was very determined in technical discussions. He also had a unique curriculum vitæ: he developed the avionics color displays for Honeywell and Boeing while never changing location; his employer would change, but his lab remained intact. While others were trying to characterize CRTs, he build a complete model for LCD displays; without him, we would not have high fidelity color LCD displays today.

Dr. Louis D. Silverstein has died at age 61. Farewell Lou!

color semiotics survey

I has been almost a year since we posted on Maryam's color semiotics research.
Everyone is talking about it these days, but where can we find a certain rule or framework which defines it? What parameters are involved? Is this framework useful for designers? Can it be communicated? Can its variation be modelled?

Last January 23^rd Maryam reached the 1800^th response to her survey. This is the last chance for your participation before her ultimate analysis. Please take to survey now at https://www.keysurvey.co.uk/votingmodule/s180/survey/365495/1a02/

processing retinae

We know very little about the physiology of color vision. For example, in the case of dichromatic color vision, in the past the trick was to have a rolodex of unattached dichromates, volunteering as an emergency physician, and when an expired dichromat showed up in the ER, there was an hour's time for wet color science.

Recently, a lot of progress has been made in color vision physiology by leveraging state-of-the-art equipment. A couple of months ago we reported on Kathy Mullen's breakthrough leveraging a new fMRI scanner in Australia. Today we cross the big pond and look at an application of big data technology.

Michele Fiscella harvests the retina of a mouse, places it on a MEA chip, sprinkles it with a nourishing fluid, and for the couple of hours the retina remains functional, projects patterns on the retina and captures the interneural traffic.

MEA—for Micro Electrode Array—is a technology from the lab of Prof. Andreas Hierlemann. On a surface of 3.6 mm², 11,011 elliptical microelectrodes probe the retina. On the average, for each neuron there are 14 microelectrodes, and each one delivers 20,000 measurements per second. The hope is to sleuth what information is passed bottom up from the retina to the LGN.

To do that, the retina has to be placed upside down on the MEA, i.e., with the retinal ganglions on the microelectrodes and the photoreceptors towards the stimulus source. This is not necessarily contra naturam, as there is nothing coming top down from the LGN, which is not part of the experiment.

Analytical engines, here the big data come…

color consolidation

In a recent press release, Danaher Corporation on 2200 Pennsylvania Avenue, NW in Washington, D.C. announced that it purchased X-Rite for approximately $625 million. X-Rite had purchased Pantone and Gretag, and the latter had purchased Macbeth. Danaher already owns well-known brands like Tektronix, Fluke, Leica Microsystems, Beckman Coulter, Videojet, and Esco (a leader in industrial digital printing) among others.

imagination and vision

In last month's post on conscious awareness I mentioned Kathy Mullen's work using an fMRI machine in Australia. Although that machine is one of the finest available, it is still a blunt instrument, but that it is all we can do with humans, where we are limited to non-invasive procedures.

A Digital Digit Camera

Color Blindness Simulator

Color Oracle is a free color blindness simulator for Windows, Mac OS X and Linux. It claims to take the guesswork out of designing for color blindness by showing you in real time what people with common color vision impairments will see.

Related posts:

• The First Time Ever I Heard Your Face
• The Colorful Blind Painter

Conscious awareness

When in the late Eighties I first compiled an introductory color tutorial, I spent considerable time to come up with a diagram illustrating that vision is not hierarchical, i.e., the simple "camcorder model" of a distal event followed by a proximal stimulus which is in turn followed by a brain event is incorrect, because there is no homunculus in our head looking at the brain event.

In this diagram—for which, by the way, I received quite a bit of negative criticism—this is indicated by making the arrows in the turquoise lines bidirectional, and I used to say, "at every level there is feedback." The most critical people were those who believed perception is strictly bottom-up.

Besides of the homunculus paradox, there has long been physiological evidence that vision has a top-down component. For example, the diameter of the center-surround fields at the cone level in the retina is modulated by a fountain of chemicals, which is global and therefore controlled by higher up stages. In fact, there are about 15 different hormones implicated in retinal fountains. More in general, chemical messengers (peptides) are more important than electrical signals for propagating information in the body (see Susan Greenfield).

At the Color Imaging Conference in San Jose last November, Kathy Mullen presented some very interesting new results obtained through fMRI studies. For example, much more information flows from the cortex to the LGN than from the retina to the LGN.

As all the cycles on my PC are consumed by a long backup, I am catching up with my reading. I am looking at Kaspar Meyer's perspective Another Remembered Present on page 415 of Science volume 335 (27 January 2012).

First of all, I had the direction of the feedback backwards. If we have a mental model of reality and use the visual system to confirm or adjust it, then the feedback is from the bottom in direction up, not the other way as I was saying.

Meyer writes that "A particularly intriguing observation is that while the initial bottom-up activation sweep along the sensory pathways can accomplish stimulus processing of considerable complexity and yield certain automated behaviors, conscious awareness of a sensory object appears to depend on top-down signals."

After presenting two influential theories of consciousness, Meyer cites some recent physiological findings and concludes: "Taken together, such data suggest that top-down signals, contrary to their common designation as 'feedback signals', have more than a modulatory function: They can reconstruct neural representations of considerable resolution in the early sensory cortices. Why would the conscious mind be grounded in dispositional records held in convergence-divergence zones, rather than the 'raw' version of reality initially established in the early sensory cortices through bottom-up signals from the thalamus? One potential answer is tied to prediction: The brain 'constantly and internally [generates] varieties of hypotheses and [tests] them upon the outside world, instead of having the environment impose (instruct) solutions directly upon the internal structure of the brain'."