Edge of Vision

Many of you have probably seen this animation of a spinning dancer silhouette from the Daily Telegraph, as it’s been making the rounds on various blogs and social networking sites. It’s a neat animation, but the blurb also states the following:

The Right Brain vs Left Brain test … do you see the dancer turning clockwise or anti-clockwise? If clockwise, then you use more of the right side of the brain and vice versa.

Personally, I can’t think of anything that would back up their source-less assertion, and a quick literature search doesn’t turn up anything either. I’ve chalked it up as a yet another misinformative popular-press write-up, but was wondering if any readers had further insight.

There’s a rather neat video from the Today Show featuring blind climber Erik Weihenmayer and a researcher, discussing BrainPort, a system which takes visual input from a camera and outputs as an array of tongue stimulation. Erik demonstrates recognizing some written numerals, while a video display gives an idea of what information is being output to his tongue. The tech seems nearly ready for market already, and I’m sure it’ll eventually become more portable.

A quick YouTube search brought up the following video from a few months ago from CBS News, which shows a blind tester walking around using the system and has some spiffy graphics which show how the system works:

Back when I was a youngin’, I dearly loved the characters Pinky and the Brain from the Animaniacs show; eventually the megalomaniacal rodent and his unique friend spun off into their own dedicated series. One of my favorite childhood memories is of the charmingly surreal segment where Pinky and the Brain sing about the parts of the brain to the melody of Camptown Races. Mo over at the neurophilosophy blog found a YouTube video of the segment, which I’ve pinned below. The neurophilosophy blog also has a transcript of the lyrics. A quick bit of trivia: Maurice LeMarche, who performed the voice of the Brain, also did the voices of Kif, Calculon, and Hedonism Bot in Futurama. Now you know!

According to an announcement (pasted below) on visionlist, the current issue of Advances in Cognitive Psychology is a special issue all about visual masking. The issue (consisting of 27 papers) is entirely free to download, and seems to be a pretty nice overview of recent research in the field.

We are pleased to announce the publication of a special issue of the
journal Advances in Cognitive Psychology on "Visual masking and the
dynamics of human perception, cognition, and consciousness."  Guest
editors for the special issue are Ulrich Ansorge, Greg Francis, Michael
Herzog and Haluk Öğmen.

The 27 papers in the special issue derived from a workshop that was
held at the Hanse-Wissenschafts Kolleg in Delmenhorst, Germany. The
workshop brought together an international group of researchers to
present state-of-the-art research on dynamic visual processing with a
focus on visual masking. This special issue provides a contemporary
synthesis of how visual masking can inform the dynamics of human
perception, cognition, and consciousness. The various papers discuss
empirical studies of perception, theoretical challenges, computational
models, and neuroscience techniques.

The special issue is available free of charge on-line at:

http://www.ac-psych.org/?id=2&rok=2007&issue=1-2

-Greg Francis

Professor of Psychological Sciences
Purdue University
http://www.psych.purdue.edu/~gfrancis/home.html

It looks like all the abstracts from the Vision Sciences Society conference we were at a few months ago have now been published in the Journal of Vision. Below is the text of the abstract for the poster I presented. If you have any questions, please leave a comment!

TMS induces detail-rich “instant replays” of natural images

We have previously demonstrated that transcranial magnetic stimulation (TMS) can cause the re-perception of recently presented visual stimuli. Here we find that such replays can be experienced for natural scene stimuli, with a level of detail suggesting low-level rather than iconic representations.

TMS was administered using a Magstim dual-pulse setup sending pulses with 50 ms separation through a figure-8 coil. The coil position over occipital cortex was optimized to elicit vivid flashes of brightness (phosphenes) in a darkened room. We screened subjects to find those that perceived large, bright phosphenes near fixation. To these subjects (N=7), we presented pictures of natural scenes and animals for 100 ms, followed by TMS at various ISIs. Subjects provided verbal descriptions, subjective ratings, and drew figures on the screen.

While TMS in a stable visual environment generally elicits phosphenes that are consistent across trials, colorless, and internally featureless, we found that TMS delivered shortly after image presentation led to the perception of clearly defined forms that varied according to the content of the flashed image.

In this experiment, five out of the seven subjects reported percepts that drew from the preceding images. In the most vivid cases, these would appear to be nearly photographic repetitions in portions of the display. In other cases, subjects would perceive uniformly-filled, phosphene-like figures whose outlines matched, in detail, contours drawn from the preceding image (abstract by Wu et. al. describes double-blind validation of these effects). In early trials, subjects experienced the most vivid replay effects within narrow time windows, which varied from subject to subject between 150-250 ms. With continued stimulation, longer ISIs (as much as one second) became effective.

This study indicates that rich, detailed visual information remains encoded well after visual perception has ended, and that TMS can allow conscious access to these nascent low-level representations.

Also, here’s the abstract for our complementary poster: TMS “instant replay” validated using novel double-blind stimulation technique

After a hiatus of more than a year, I’ve decided to try reactivating this jolly ol’ blog. As before, my plan is to periodically share commentary on various interesting happenings in neuroscience and artificial intelligence.

As for myself, for the past year I’ve been doing research using transcranial magnetic stimulation (TMS) to reactivate recently-viewed visual percepts in occipital cortex. The basis of the work can be found in the PhD thesis of my colleague Daw-An Wu, titled “How perception adheres color to objects and surfaces : studies using visual illusions and transcranial magnetic stimulation.” At some point I’ll elaborate on the directions we’ve been pursuing in the past year, which have had some rather fascinating results.