(Image caption: The EyeCane: (A) A flow chart depicting the use of the device and an illustration of a user. Note the two sensor beams, one pointing directly ahead, and one pointing towards the ground for obstacle detection. (B) Photo of the “EyeCane.”)

User-Friendly Electronic “EyeCane” Enhances Navigational Abilities for the Blind

White Canes provide low-tech assistance to the visually impaired, but some blind people object to their use because they are cumbersome, fail to detect elevated obstacles, or require long training periods to master. Electronic travel aids (ETAs) have the potential to improve navigation for the blind, but early versions had disadvantages that limited widespread adoption. A new ETA, the “EyeCane,” developed by a team of researchers at The Hebrew University of Jerusalem, expands the world of its users, allowing them to better estimate distance, navigate their environment, and avoid obstacles, according to a new study published in Restorative Neurology and Neuroscience. 

“The EyeCane was designed to augment, or possibly in the more distant future, replace the traditional White Cane by adding information at greater distances (5 meters) and more angles, and most importantly by eliminating the need for contacts between the cane and the user’s surroundings [which makes its use difficult] in cluttered or indoor environments,” says Amir Amedi, PhD, Associate Professor of Medical Neurobiology at The Israel-Canada Institute for Medical Research, The Hebrew University of Jerusalem.

The EyeCane translates point-distance information into auditory and tactile cues. The device is able to provide the user with distance information simultaneously from two different directions: directly ahead for long distance perception and detection of waist-height obstacles and pointing downward at a 45° angle for ground-level assessment. The user scans a target with the device, the device emits a narrow beam with high spatial resolution toward the target, the beam hits the target and is returned to the device, and the device calculates the distance and translates it for the user interface. The user learns intuitively within a few minutes to decode the distance to the object via sound frequencies and/or vibration amplitudes.

Recent improvements have streamlined the device so its size is 4 x 6 x 12 centimeters with a weight of less than 100 grams. “This enables it to be easily held and pointed at different targets, while increasing battery life,” says Prof. Amedi.

The authors conducted a series of experiments to evaluate the usefulness of the device for both blind and blindfolded sighted individuals. The aim of the first experiment was to see if the device could help in distance estimation. After less than five minutes of training, both blind and blindfolded individuals were able to estimate distance successfully almost 70% of the time, and the success rate surpassed 80% for two of the three blind participants. “It was amazing seeing how this additional distance changed their perception of their environment,” notes Shachar Maidenbaum, one of the researchers on Prof. Amedi’s team. “One user described it as if her hand was suddenly on the far side of the room, expanding her world.”

A second experiment looked at whether the EyeCane could help individuals navigate an unfamiliar corridor by measuring the number of contacts with the walls. Those using a White Cane made an average of 28.2 contacts with the wall, compared to three contacts with the EyeCane – a statistically significant tenfold reduction. A third experiment demonstrated that the EyeCane also helped users avoid chairs and other naturally occurring obstacles placed randomly in the surroundings.

“One of the key results we show here is that even after less than five minutes of training, participants were able to complete the tasks successfully,” says Prof. Amedi. “This short training requirement is very significant, as it make the device much more user friendly. Every one of our blind users wanted to take the device home with them after the experiment, and felt they could immediately contribute to their everyday lives,” adds Maidenbaum.

The Amedi lab is also involved in other projects for helping people who are blind. In another recent publication in Restorative Neurology and Neuroscience they introduced the EyeMusic, which offers much more information, but requires more intensive training. “We see the two technologies as complementar,y” says Prof. Amedi. “You would use the EyeMusic to recognize landmarks or an object and use the EyeCane to get to it safely while avoiding collisions.”

A video demonstration of the EyeCane is available at http://www.youtube.com/watch?v=rpbGaPxUKb4

Can We Reconcile the Declarative Memory and Spatial Navigation Views on Hippocampal Function?

Some argue that hippocampus supports declarative memory, our capacity to recall facts and events, whereas others view the hippocampus as part of a system dedicated to calculating routes through space, and these two contrasting views are pursued largely independently in current research. Here we offer a perspective on where these views can and cannot be reconciled and update a bridging framework that will improve our understanding of hippocampal function.

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Memories Are ‘Geotagged’ With Spatial Information

Using a video game in which people navigate through a virtual town delivering objects to specific locations, a team of neuroscientists from the University of Pennsylvania and Freiburg University has discovered how brain cells that encode spatial information form “geotags” for specific memories and are activated immediately before those memories are recalled.

Their work shows how spatial information is incorporated into memories and why remembering an experience can quickly bring to mind other events that happened in the same place.

"These findings provide the first direct neural evidence for the idea that the human memory system tags memories with information about where and when they were formed and that the act of recall involves the reinstatement of these tags," said Michael Kahana, professor of psychology in Penn’s School of Arts and Sciences.

The study was led by Kahana and professor Andreas Schulze-Bonhage of Freiberg. Jonathan F. Miller, Alec Solway, Max Merkow and Sean M. Polyn, all members of Kahana’s lab, and Markus Neufang, Armin Brandt, Michael Trippel, Irina Mader and Stefan Hefft, all members of Schulze-Bonhage’s lab, contributed to the study. They also collaborated with Drexel University’s Joshua Jacobs.

Their study was published in the journal Science.

Kahana and his colleagues have long conducted research with epilepsy patients who have electrodes implanted in their brains as part of their treatment. The electrodes directly capture electrical activity from throughout the brain while the patients participate in experiments from their hospital beds.

As with earlier spatial memory experiments conducted by Kahana’s group, this study involved playing a simple video game on a bedside computer. The game in this experiment involved making deliveries to stores in a virtual city. The participants were first given a period where they were allowed to freely explore the city and learn the stores’ locations. When the game began, participants were only instructed where their next stop was, without being told what they were delivering. After they reached their destination, the game would reveal the item that had been delivered, and then give the participant their next stop.

After 13 deliveries, the screen went blank and participants were asked to remember and name as many of the items they had delivered in the order they came to mind.

This allowed the researchers to correlate the neural activation associated with the formation of spatial memories (the locations of the stores) and the recall of episodic memories: (the list of items that had been delivered).

“A challenge in studying memory in naturalistic settings is that we cannot create a realistic experience where the experimenter retains control over and can measure every aspect of what the participant does and sees. Virtual reality solves that problem,” Kahana said. “Having these patients play our games allows us to record every action they take in the game and to measure the responses of neurons both during spatial navigation and then later during verbal recall.”

By asking participants to recall the items they delivered instead of the stores they visited, the researchers could test whether their spatial memory systems were being activated even when episodic memories were being accessed. The map-like nature of the neurons associated with spatial memory made this comparison possible.

"During navigation, neurons in the hippocampus and neighboring regions can often represent the patient’s virtual location within the town, kind of like a brain GPS device," Kahana said. "These so-called ‘place cells’ are perhaps the most striking example of a neuron that encodes an abstract cognitive representation."

Using the brain recordings generated while the participants navigated the city, the researchers were able to develop a neural map that corresponded to the city’s layout. As participants passed by a particular store, the researchers correlated their spatial memory of that location with the pattern of place cell activation recorded. To avoid confounding the episodic memories of the items delivered with the spatial memory of a store’s location, the researchers excluded trips that were directly to or from that store when placing it on the neural map.

With maps of place cell activations in hand, the researchers were able to cross- reference each participant’s spatial memories as they accessed their episodic memories of the delivered items. The researchers found that the neurons associated with a particular region of the map activated immediately before a participant named the item that was delivered to a store in that region.

“This means that if we were given just the place cell activations of a participant,” Kahana said, “we could predict, with better than chance accuracy, the item he or she was recalling. And while we cannot distinguish whether these spatial memories are actually helping the participants access their episodic memories or are just coming along for the ride, we’re seeing that this place cell activation plays a role in the memory retrieval processes.”

Earlier neuroscience research in both human and animal cognition had suggested the hippocampus has two distinct roles: the role of cartographer, tracking

location information for spatial memory, and the role of scribe, recording events for episodic memory. This experiment provides further evidence that these roles are intertwined.

“Our finding that spontaneous recall of a memory activates its neural geotag suggests that spatial and episodic memory functions of the hippocampus are intimately related and may reflect a common functional architecture,” Kahana said.

Bat and Rat Brain Rhythms Differ When on the Move

To get a clear picture of how humans and other mammals form memories and find their way through their surroundings, neuroscientists must pay more attention to a broad range of animals rather than focus on a single model species, say two University of Maryland researchers, Katrina MacLeod and Cynthia Moss. Their new comparative study of bats and rats reports differences between the species that suggest the need to revise models of spatial navigation.

In a paper appearing in the April 19, 2013 issue of Science, the UMD researchers and two colleagues at Boston University reported significant differences between rats’ and bats’ brain rhythms when certain cells were active in a part of the brain used in memory and navigation.

These cells behaved as expected in rats, which mostly move along surfaces. But in bats, which fly, the continuous brain rhythm did not appear, said Moss, a professor in Psychology and Biology and the Institute for Systems Research.

The finding suggests that even though rats, bats, humans and other mammals share a common neural representation of space in a part of the brain that has been linked to spatial information and memory, they may have different cellular mechanisms to create or interpret those maps, said MacLeod, an assistant research scientist in Biology.

“To understand brains, including ours, we really must study neural activity in a variety of animals,” MacLeod said. “Common features across multiple species tell us ‘Aha, this is important,’ but differences can occur because of variances in the animals’ ecology, behavior, or evolutionary history.”

The research team focused on a brain region that contains specialized “grid cells,” so named because they form a hexagonal grid of activity related to the animal’s location as it navigates through space. This brain region, the medial entorhinal cortex, sits next to the hippocampus, the place that, in humans, forms memories of events such as where a car is parked. The medial entorhinal cortex acts as a hub of neural networks for memory and navigation.

Grid cells were first noticed in rats navigating their environment, but recent work by Nachum Ulanovsky (Moss’s former postdoctoral researcher at UMD) and his research team at the Weizmann Institute in Rehovot, Israel, has shown these cells exist in bats as well.

In rats, grid cells fire in a pattern called a theta wave when the animals spatially navigate. Theta waves are fairly low-frequency electrical oscillations that also have been observed at the cellular level in the medial entorhinal cortex. The prominence of theta waves in rats suggested they were important. As a result, neuroscientists, trying to understand the relationship between theta waves and grid cells, have developed models of the brain based on the assumption that theta waves are key to spatial navigation in mammals.

However, Moss said, “recordings from the brains of bats navigating in space contain a surprise, because the expected theta rhythms aren’t continuously present as they are in the rodent.”

The new Science study doubles down on the lack of theta in bats by reporting that theta rhythms also are not present at the cellular level. “The bat neurons don’t ‘ring’ the way the rat neurons do,” says MacLeod. “This raises a lots of questions as to whether theta rhythms are actually doing what the spatial navigation theory proposes in rats or even humans.”

Males’ superior spatial ability likely is not an evolutionary adaptation

Males and females differ in a lot of traits (besides the obvious ones) and some evolutionary psychologists have proposed hypotheses to explain why. Some argue, for example, that males’ slight, but significant, superiority in spatial navigation over females – a phenomenon demonstrated repeatedly in many species, including humans – is probably “adaptive,” meaning that over the course of evolutionary history the trait gave males an advantage that led them to have more offspring than their peers.

A new analysis published in The Quarterly Review of Biology found no support for this hypothesis. The researchers, led by University of Illinois psychology professor Justin Rhodes, looked at 35 studies that included data about the territorial ranges and spatial abilities of 11 species of animals: cuttlefish, deer mice, horses, humans, laboratory mice, meadow voles, pine voles, prairie voles, rats, rhesus macaques and talastuco-tucos (a type of burrowing rodent). Rhodes and his colleagues found that in eight out of 11 species, males demonstrated moderately superior spatial skills to their female counterparts, regardless of the size of their territories or the extent to which males ranged farther than females of the same species.

The findings lend support to an often-overlooked hypothesis, Rhodes said. The average superiority of males over females in spatial navigation may just be a “side effect” of testosterone, he said. (Previous studies have shown that women who take testosterone tend to see an improvement in their spatial navigation skills, he said.)

The analysis adds a new dimension to an ongoing debate about the evolutionary significance of some baffling human traits. Rhodes and his colleagues object to “creation stories” that seek to explain sexual phenomena like the female orgasm, rape or menopause by hypothesizing that they evolved because they provided an evolutionary advantage. Some evolutionary psychologists describe rape, for example, as an alternate mating strategy for males who otherwise are reproductively unsuccessful. Others say menopause evolved in women to enhance the survival of their genes by increasing the time spent nurturing their grandchildren. Some of these hypotheses seem intuitive, Rhodes said. “But these stories generally are not testable.”

Researchers tend to overlook the fact that many physical and behavioral traits arise as a consequence of random events, or are simply side effects of other changes that offer real evolutionary advantages, he said.

“For example, women have nipples because it’s an adaptation; it promotes the survival of their offspring,” Rhodes said. “Men get it because it doesn’t harm them. So if we see something that’s advantageous for one sex, the other sex will get it because it’s inheriting the same genes – unless it’s bad for that sex.”

Similarly, scientists who claim that the different spatial skills in men and women are adaptive must explain why women failed to inherit the superior spatial skills of their navigationally enhanced fathers, Rhodes said.

“The only way you will get a sex difference (in an adaptive trait) is where a trait is good for one sex and bad for the other,” he said. “But how is navigation bad for women? This is a flaw in the logic.”

“When people hear arguments made or stories told, particularly about human behaviors being products of adaptation, I think they should ask the question: ‘Where is the evidence?’ ” Rhodes said.

Fluctuations in the size of brain waves contribute to information processing

Cyclical variations in the size of brain wave rhythms may participate in the encoding of information by the brain, according to a new study led by Colin Molter of the Neuroinformatics Japan Center, RIKEN Brain Science Institute, Wako.

Brain waves are produced by the synchronized activity of large populations of neurons. Low frequency brain waves called theta oscillations are known to support memory formation. Researchers typically examine the frequency of oscillations in a given part of the brain and the timing of oscillations in different brain regions, but know very little about how variations in the size of these oscillations contribute to information processing.

Molter and his colleagues used electrode arrays to record brain waves from the rat hippocampus, a structure known to be critical for memory formation and spatial navigation, while the animals performed various behaviors, such as exploring open spaces, running through a maze and in a wheel, and sleeping. They observed fluctuations in the size of theta oscillations during all the behaviors—the brain waves did not remain the same size, but rather waxed and waned second by second.

During spatial navigation for example, individual hippocampal neurons called place cells become more active when the animal is in one or a few specific locations compared to the rest of the explored environment. The researchers found that the time of firing of many of the place cells correlated with the fluctuations in the size of the theta waves. During sleep, the activity of most of the cells was timed with the largest theta oscillations.

Even though the size of theta waves is correlated with motor behavior, their cyclic fluctuations at this time scale, observed while the rats ran and explored, were not correlated with the animals’ speed or acceleration. The fluctuations are instead likely to be generated by the brain itself, as their presence during sleep also suggests they are intrinsic.

The researchers speculate that this phenomenon could be helpful for the neuronal representation of space, resolving the ambiguity of space coding by place cells that become active in multiple preferred locations. “We are currently working on several new experiments to understand how the spatial location may affect the slow modulation and how the timing of the slow modulation affects behavior,” says Molter. “We are also trying to provide a model that incorporates the theta slow modulation to help propagation of activity between cell assemblies.”