Humans to the rescue

Images like the one above are familiar to any of us who have ever used webmail, Ticketmaster, or any other web service that wants to prevent automated spammers and scalpers from exploiting their systems. The distorted, fuzzy letters don't provide a challenge to humans, but are indecipherable to the most sophisticated computer algorithms. Our genius is facilitated by our "invariant" perceptual abilities; that is, we can recognize objects, faces, and letters independent of rotation, translation, and scale.

However, these CAPTCHAs (Completely Automated Public Turing Test to Tell Computers and Humans Apart) were designed with a wonderfully clever ulterior motive. In addition to preventing rogue bots from devastating our virtual lives, CAPTCHAs like the one above are actually exploiting you, the human, and the invariance of your human perception, to help digitize the world. The words presented in these CAPTCHAs are pulled from the book-scanning project of the Internet Archive, which aims to scan millions of public-domain books and put them online for free. One word of the CAPTCHA is known to the computer, and is used to verify your humanness, while the other was indecipherable to the Archive's scanners. When you type in that word, you're actually translating the image into text for the Archive.

There's a fantastic article in Wired Magazine about this type of "human computation," "the art of using massive groups of networked human minds to solve problems that computers cannot." The article profiles the work of Luis von Ahn, who designs clever ways to harness the powerful brains of bored web surfers to solve computing problems (e.g. judging random pictures as "pretty," tagging images and audioclips, etc.)

From Wired Magazine:

If people could so easily recognize pictures of letters and numbers, could [they] use this ability to identify and label the vast number of images on the Web?

...

The way to do it, he realized, was as a game. It would pull images off the Web, then randomly pair two players from around the world. They would be shown the same images, then each would type in as many words as they could to describe those images, hoping to hit upon the same ones as their anonymous partner. They'd get 50 points for each match, and two and a half minutes to earn as many points as possible. Von Ahn suspected that whenever the players agreed on a word — "meadow" to describe a tree-lined clearing, for example — they would be choosing a highly accurate label for the picture.

Von Ahn cobbled the game together in a week — "crappy, totally terrible code," he admits — and threw it online. He dubbed it The ESP Game and emailed the URL to a few friends. Within days it was Slashdotted, whereupon his server nearly crashed under the load of new players. Astonished, von Ahn watched for the next four months as 13,000 players produced 1.3 million labels for some 300,000 images — with a few hardcore fans clocking more than 50 hours of play. "It's like crack," as one player complained in an email to von Ahn. The labels his players generated were far more accurate than what other image-search technologies produced. Most search engines are limited to sniffing out words associated with a picture, such as the name given to the image, words in the page around it, or links pointing to it. That's inherently imprecise: When von Ahn recently searched for "dog" on Google, a third of the pictures showed no dogs at all. When he queried the ESP database, almost all the results contained canines. Better yet, players often generated labels that were subtle and nuanced. A search for "funny" found a picture of Ronald McDonald being hauled away by police and one of Queen Elizabeth picking her nose.

Even the DHS wants to employ your brainpower as you procrastinate on the web:

This spring, von Ahn got a call from the Department of Homeland Security. He went to Washington to meet with DHS officials, and together they devised a game in which people are challenged to find dangerous objects in images of x-rayed baggage. The pictures would be fed from airport scanners, and players would act as a second set of eyes for overtaxed security employees. If enough players noticed something amiss, an alert would be triggered.

Von Ahn's other games that capitalize on human superiority (supposedly available at Games with a Purpose "in July," but as of now the site isn't running yet) include:

1) Matchin' Players are shown the same pair of images, then each tries to pick the one they'll both agree is more attractive. Creates a database of images searchable by aesthetic value, a task no algorithm can perform.

2) Babble Two English-speaking players are shown a sentence in a foreign language that neither of them speak. A list of possible English meanings appears below each word. Players try to agree upon a set of English words that forms the most coherent sentence. Translates foreign text into English without requiring anyone fluent in both languages.

3) InTune Players listen to the same audioclip and then try to come up with the same phrase to characterize it. Tags sounds with searchable descriptive text.

4) Squigl Two players are shown the same picture and a word describing an element within the image (e.g., a picture of a dog and the word "leash"). They each draw a border around the element. Produces a set of pictures with their internal components tagged — terrific for very specific image searches.

5) Verbosity One player is given a word, and the other tries to guess that word by completing phrases such as "It is near a ____" or "It is a type of ____." The first player answers "true" or "false" but can't use the word itself. Creates a database of commonsense knowledge describing the objects.

Link to the full Wired article.

Adult Entertainment

The biology of brain plasticity, including adult neurogenesis, synaptic plasticity, axon regrowth, and synaptic reorganization, is currently one of the most intensively studied areas of neuroscience. One of the burgeoning avenues of research for this field explores how altered plasticity may account for some of the behavioral and neural changes afflicting the aging brain, and is leading to efforts of fostering plasticity and thus "rejuvenate" the brain.

Perhaps the most popular products to emerge from this research are "brain games," which are activities designed to enhance cognitive function. These games have encountered a healthy bit of well-deserved skepticism from the scientific community; few of them have been validated by techniques even remotely "scientific" (by including, for example, controls), yet many make grand claims of improving some general notion of "intelligence" and well-being. There are, however, a few exceptions: "brain fitness" products emerging from within the scientific community, such as Posit Science, intended for people in their 60s and 70s, and Lumosity, which targets a younger population (i.e. baby boomers.) Since many functions, such as processing speed, working memory, and attention, begin declining around the age of 30, it seems reasonable to start on the early side.

Lumosity is a new program, so the games are still in "beta" phase and thus free, and these games are easily the most entertaining of any I've previously played (evoking behavior reminiscent of my childhood Tetris addiction.) More importantly, the games are inspired by research on human cognition; the company's head of neuroscience research studied with Jon Cohen at Princeton and John Gabrieli when the latter was at Stanford, among others, and there are a number of cognitive neuroscientists on the board of advisors. I recently met one of the founders at Stanford, and after discussing my research on adult hippocampal neurogenesis, I ended up joining these cognitive neuroscientists as a fellow scientific advisor. Anyways, the group at Lumos Labs performed a randomized, controlled study, which I can personally endorse, showing that Lumosity users improved on tasks of working memory and visual attention (there's an SFN poster and white paper available for your scrutiny as well).

Further scientific validation of the program's ability to improve various cognitive functions is certainly needed, and is in progress. Most importantly, of course, will be evidence that this sort of cognitive training can have long-term effects that translate to "real-world" functional improvements. In the meantime, the games are fun (with enticingly impressive high score lists) and certainly can't hurt.

Young, restless neurons may bully their elders

Neurogenesis--the birth and integration of neurons--occurs in the adult brains of all mammals, including humans. I've posted on the phenomenon of adult neurogenesis here and here, and it happens to the focus of my thesis in grad school. One of the major issues in the field is how the generation of new neurons translates into a functional change in the brain. Birth is the first of a number of daunting challenges: new cells must then survive, make connections, and integrate into the circuitry of the mature brain. It is this last undertaking--joining existing networks without disrupting the circuit--which has proved the most conceptually challenging.

Since Alan Turing and the dawn of computer science, the prevailing model of the brain has been based on a computer analogy. The networks of neurons composing the brain were likened to the hard-wired circuits of computer hardware, cemented in place at an early age. Plasticity, which refers to the brain's ability to learn and adapt to the environment, was attributed solely to changes occurring within the operating circuitry, between its existing components (i.e. synaptic plasticity). In line with the computer analogy, this synaptic plasticity is thought to resemble the process of changing computer operations by adding software, which operate within the context of a hard-wired network and thus do not require structural reorganization of the circuitry.

Although synaptic plasticity is a crucial mechanism underlying the brain's remarkable adaptive capabilities, it is not the only mechanism. In the 60s and 70s, theories of structural plasticity, such as axonal elongation and synaptic reorganization, began to emerge and gradually creep into the analogy with computers. However, these activities involved neural pathways being reorganized between existing neurons; new neurons continued to be excluded from the conceptual framework.

About a decade ago, adult neurogenesis finally gained widespread acceptance in the scientific community, initiating a gradual shift in the concept of brain plasticity and adaptability. These new neurons, which integrate into existing neural networks, provided a previously unrecognized, and far more dramatic, form of structural and functional plasticity. The crucial question of how new neurons impact the adult neuronal circuitry remains a challenge, and is dictated by two parameters: their physiological properties and their synaptic connectivity.

Recent work has shown that new neurons in the adult hippocampus (a structure crucial for the formation of memories, and one of the two major locations of adult neurogenesis) have unique physiological properties: they are more excitable (i.e. more likely to fire action potentials subsequent to a given stimulation) and have an enhanced potential for synaptic plasticity. But what about their connectivity? Do the existing neurons send out new axons to accommodate new neurons, or do the new neurons incorporate themselves into the existing circuits?

New findings from Rusty Gage’s lab at the Salk Institute for Biological Sciences, published their results online last week in Nature Neuroscience, support the latter. The researchers tracked the fate of newborn neurons by injecting a retrovirus engineered to carry the gene for green fluorescent protein (GFP) into the hippocampus. This technique is useful because retroviruses can only infect dividing cells (with the exception of lentiviruses like HIV, which can infect nondividing cells such as mature neurons). Thus, cells that dividing at the time of the injection, including newly born neurons, are labeled green, and can be tracked as they make the initial connections with the existing hippocampal circuitry.

They used an impressive combination of high-resolution imaging techniques to examine the fine structural details of the emerging connections pioneered by these new neurons. Their analysis allowed them to digitally reconstruct synapses during formation, and showed that initially, new neurons send out small protrusions, called filopodia, to make contact with synapses that already exist between two "older" neurons. When the filopodia mature, they become functional dendritic "spines," which are small protrusions from dendrites that actually participate in synaptic communication. Thus, the new neurons join into a preexisting synapse, forming a "multi-synapse" connection, suggesting that new neurons are making connections with established networks.

Once they've elbowed their way into an existing communication, the new neurons take their intrusion up another notch. As the neurons aged, they became less likely to be involved in "multi-synapse" connections, and concomitantly more likely to be involved in single-synapse connections. This suggests that the formerly multi-synapse connections were transforming into single-synapse connections; in other words, new neurons were taking over the connections of older neurons, effectually replacing those neurons in a particular part of the circuit. The Gage lab has previously shown that new neurons depend on neuronal input to survive; it's possible that new neurons have to compete with older neurons for those connections, and that their unique physiological properties may give them a competitive advantage.

This hypothesized replacement mechanism, which must still be tested by live-cell imaging, makes the incorporation of new neurons into functional networks easier to conceptualize. Instead of forming new circuits willy-nilly, or forcing old networks bring them in, new neurons muscle their way into the established circuitry, occasionally replacing older, less vigorous neurons. One of the implications here is new neurons may be able to functionally replace dead or dying neurons in neurodegenerative diseases such as Parkinson's or Alzheimer's. Further, these new neurons, with their enhanced plasticity, may continually "reinvigorate" an old hippocampus, even in healthy adults, allowing learning and memory to continue at higher levels that would otherwise be possible.

Reference:
Toni N, Teng EM, Bushong EA, Aimone JB, Zhoa C, Consiglio A, van Praag H, Martone ME, Ellisman MH, Gage FH. Synapse formation on neurons born in the adult hippocampus. Nature Neuroscience. 2007, May 7. Advanced online publication.