How the brain leads us to believe we have sharp vision

We assume that we can see the world around us in sharp detail. In fact, our eyes can only process a fraction of our surroundings precisely. In a series of experiments, psychologists at Bielefeld University have been investigating how the brain fools us into believing that we see in sharp detail. The results have been published in the scientific magazine ‘Journal of Experimental Psychology: General.’ Its central finding is that our nervous system uses past visual experiences to predict how blurred objects would look in sharp detail.

"In our study we are dealing with the question of why we believe that we see the world uniformly detailed," says Dr. Arvid Herwig from the Neuro-Cognitive Psychology research group of the Faculty of Psychology and Sports Science. The group is also affiliated to the Cluster of Excellence Cognitive Interaction Technology (CITEC) of Bielefeld University and is led by Professor Dr. Werner X. Schneider.

Only the fovea, the central area of the retina, can process objects precisely. We should therefore only be able to see a small area of our environment in sharp detail. This area is about the size of a thumb nail at the end of an outstretched arm. In contrast, all visual impressions which occur outside the fovea on the retina become progressively coarse. Nevertheless, we commonly have the impression that we see large parts of our environment in sharp detail.

Herwig and Schneider have been getting to the bottom of this phenomenon with a series of experiments. Their approach presumes that people learn through countless eye movements over a lifetime to connect the coarse impressions of objects outside the fovea to the detailed visual impressions after the eye has moved to the object of interest. For example, the coarse visual impression of a football (blurred image of a football) is connected to the detailed visual impression after the eye has moved. If a person sees a football out of the corner of her eye, her brain will compare this current blurred picture with memorised images of blurred objects. If the brain finds an image that fits, it will replace the coarse image with a precise image from memory. This blurred visual impression is replaced before the eye moves. The person thus thinks that she already sees the ball clearly, although this is not the case.

The psychologists have been using eye-tracking experiments to test their approach. Using the eye-tracking technique, eye movements are measured accurately with a specific camera which records 1000 images per second. In their experiments, the scientists have recorded fast balistic eye movements (saccades) of test persons. Though most of the participants did not realise it, certain objects were changed during eye movement. The aim was that the test persons learn new connections between visual stimuli from inside and outside the fovea, in other words from detailed and coarse impressions. Afterwards, the participants were asked to judge visual characteristics of objects outside the area of the fovea. The result showed that the connection between a coarse and detailed visual impression occurred after just a few minutes. The coarse visual impressions became similar to the newly learnt detailed visual impressions.

"The experiments show that our perception depends in large measure on stored visual experiences in our memory," says Arvid Herwig. According to Herwig and Schneider, these experiences serve to predict the effect of future actions ("What would the world look like after a further eye movement"). In other words: "We do not see the actual world, but our predictions."

Learning to see better in life and baseball

With a little practice on a computer or iPad—25 minutes a day, 4 days a week, for 2 months—our brains can learn to see better, according to a study of University of California, Riverside baseball players reported in the Cell Press journal Current Biology on February 17. The new evidence also shows that a visual training program can sometimes make the difference between winning and losing.

The study is the first, as far as the researchers know, to show that perceptual learning can produce improvements in vision in normally seeing individuals.

"The demonstration that seven players reached 20/7.5 acuity—the ability to read text at three times the distance of a normal observer—is dramatic and required players to stand forty feet back from the eye chart in order to get a measurement of their vision," says Aaron Seitz of the University of California, Riverside. For reference, 20/20 is considered normal visual acuity.

In the training game, the players’ task was to find and select visual patterns modeled after stimuli to which neurons in the early visual cortex of the brain respond best, Seitz explains. As game play commenced, those patterns were made dimmer and dimmer, exercising the players’ vision as they searched.

"The goal of the program is to train the brain to better respond to the inputs that it gets from the eye," Seitz says. "As with most other aspects of our function, our potential is greater than our normative level of performance. When we go to the gym and exercise, we are able to increase our physical fitness; it’s the same thing with the brain. By exercising our mental processes we can promote our mental fitness."

After the 2 month training period, players reported “seeing the ball much better,” “greater peripheral vision,” “easy to see further,” “able to distinguish lower-contrasting things,” “eyes feel stronger, they don’t get tired as much,” and so on.

The players also showed greater-than-expected improvements in their game. They were less likely to strike out and got more runs. The researchers estimate that those gains in batting statistics may have given the team an additional four or five wins in the 2013 season.

The researchers are now extending their work to include different groups, including members of the Los Angeles and Riverside Police Departments and people with low vision due to cataracts, macular degeneration, or amblyopia. They will also apply the same principles to other aspects of cognition, including memory and attention.

It all comes down to one thing: “Understanding the rules of brain plasticity unlocks great potential for improvement of health and wellbeing,” Seitz says.

Activating the ‘mind’s eye’ — sounds, instead of eyesight, can be alternative vision

Common wisdom has it that if the visual cortex in the brain is deprived of visual information in early infanthood, it may never develop properly its functional specialization, making sight restoration later in life almost impossible.

Scientists at the Hebrew University of Jerusalem and in France have now shown that blind people – using specialized photographic and sound equipment – can actually “see” and describe objects and even identify letters and words.

The new study by a team of researchers, led by Prof. Amir Amedi of the Edmond and Lily Safra Center for Brain Sciences and the Institute for Medical Research Israel-Canada at the Hebrew University and Ph.D. candidate Ella Striem-Amit, has demonstrated how this achievement is possible through the use of a unique training paradigm, using sensory substitution devices (SSDs).

SSDs are non-invasive sensory aids that provide visual information to the blind via their existing senses. For example, using a visual-to-auditory SSD in a clinical or everyday setting, users wear a miniature camera connected to a small computer (or smart phone) and stereo headphones.

The images are converted into “soundscapes,” using a predictable algorithm, allowing the user to listen to and then interpret the visual information coming from the camera. The blind participants using this device reach a level of visual acuity technically surpassing the world-agreed criterion of the World Health Organization (WHO) for blindness, as published in a previous study by the same group.

Researchers reveal first brain study of Temple Grandin

Temple Grandin, perhaps the world’s most famous person with autism, has exceptional nonverbal intelligence and spatial memory, and her brain has a host of structural and functional differences compared with the brains of controls, according to a presentation Saturday at the 2012 Society for Neuroscience annual meeting in New Orleans.

Grandin, professor of animal sciences at Colorado State University, is an outspoken advocate for autism research and awareness. She is known as a ‘savant,’ or a person who shows characteristic social deficits of autism and yet also has some exceptional abilities. For instance, she has extremely sharp visual acuity.

This is the first study to take a close look at Grandin’s brain, and one of the first to look at the brains of savants.