Tag Archives: spatial navigation

rat-navigation

Virtual reality for rats shows how different brain functions cooperate during navigation

Some people are better navigators than others, i.e. men better than women. Whether you can make your way effortlessly through the woods to reach a safe house or get seemingly lost on your way home from a different bus stop, it doesn’t make that much of a different at a sensory level. Navigation is often taken for granted, but the truth is it’s one of the most complex neurological function of the brain, one which requires a great of energy and complexity. This fundamental skill is paramount to avoiding threats and locating food (the reward), and through the mechanisms of evolution which promotes survival traits, it has steadily improved generation after generation.

rat-navigation

Rat in virtual reality. (c) UCLA

The connection between spatial reasoning and reward (anticipating and actually locating food) has been very difficult to measure, mainly because current technology doesn’t permit to simultaneously study both while an animal was moving. A team of researchers at UCLA have devised, however, an ingenious multisensory virtual world for rats in order to understand how the brain processes the environmental cues available to it and whether various regions of the brain cooperate in this task.

Rats are inserted in a sort of cube, with displays on each side, and are trained to navigate their environment that changes each time through a trackball to reach their reward (sugar water). Since the animal moves on the trackball, it actually is stationary, but is offered the illusion of movement aided by visual and auditory cues.

Previously, the same team of  UCLA researchers, led by neurophysicist Mayank Mehta, discovered how individual brain cells compute how much distance the subjects traveled. All animals, including humans, need to know where they’re located at a certain point in order to compare to their reference frame and navigate. Which way is left, right, up, down etc. How reward anticipation and reward seeking or navigation are connected has escaped scientists for some time.

“Look at any animal’s behavior,” Mehta said, “and at a fundamental level, they learn to both anticipate and seek out certain rewards like food and water. But until now, these two worlds — of reward anticipation and navigation — have remained separate because scientists couldn’t measure both at the same time when subjects are walking.”

Navigation requires the animal to form a spatial map of its environment so it can walk from point to point. An anticipation of a reward requires the animal to learn how to predict when it is going to get a reward and how to consume it. Mehta and colleagues, using their rat virtual environment, have now found a way to correlated the two.

The rat MATRIX

While the rats where navigating their environment in search for the reward (food), visual and auditory cues were played. When both sound and visual was played, the rats used both their legs and tongue to navigate in harmony and easily locate the feed tube. Yum!  This confirmed a long held expectation, that different behaviors are synchronized. When the visual cues were shut off, and only sound was there, the rats legs seemed to be “lost” as the rodents randomly walked about, but their tongue showed a clear map of space, as if the tongue knew where the food was.

“They demonstrated this by licking more in the vicinity of the reward. But their legs showed no sign of where the reward was, as the rats kept walking randomly without stopping near the reward,” he said. “So for the first time, we showed how multisensory stimuli, such as lights and sounds, influence multimodal behavior, such as generating a mental map of space to navigate, and reward anticipation, in different ways. These are some of the most basic behaviors all animals engage in, but they had never been measured together.”

Previously, Mehta said, it was thought that all stimuli would influence all behaviors more or less similarly.

“But to our great surprise, the legs sometimes do not seem to know what the tongue is doing,” he said. “We see this as a fundamental and fascinating new insight about basic behaviors, walking and eating, and lends further insight toward understanding the brain mechanisms of learning and memory, and reward consumption.”
The study results were reported in the journal  PLOS ONE.
The caveman theory that says men are better navigators than women because they had to find their back home after hunting is flawed, University of Illinois researchers show.

Why are men better navigators than women? Testosterone, not evolution might be the answer

The caveman theory that says men are better navigators than women because they had to find their back home after hunting is flawed, University of Illinois researchers show.

The caveman theory that says men are better navigators than women because they had to find their back home after hunting is flawed, University of Illinois researchers show.

It’s a rather well-attested fact that men are significantly better than women at spatial navigation, something that holds across a wide variety of species, not just humans. General belief holds that evolution triggered this response since our ancestors needed to return home after traveling vast distances in search of food, while the females stayed home. This theory is flawed according to the University of Illinois, who have proven this not to be the case. Instead, they suggest testosterone as a more reasonable explanation for spatial differences between men and women.

If the evolutionary theory were correct, as in males that were better at navigating had a better chance of survival and thus passed on their genes, then basic genetics tells us that these genes would have been passed to women as well. Still, the discrepancy holds.

The only way a certain gene might be passed to a sex of a species, and not the other, is if that gene would negatively affect one of the sexes and not the other. A good example is nipples. For women, nipples are indispensable and is fairly obvious why (nurture young), however, they serve no purpose in men. So why do men have them? The answer is simple: because it doesn’t hurt them. If nipples would negatively affect men in some sort of way, then they would have disappeared in a matter of a couple of generations.

Still, to test plug holes even further in this evolutionary theory for spatial ability, University of Illinois researchers aggregated data from 35 studies on territorial ranges and spatial abilities in humans and a number of animals, including cuttlefish, deer mice, horses, laboratory mice, meadow voles, pine voles, prairie voles, rats, rhesus macaques and talas tuco-tucos (a type of burrowing rodent).

If the theory was true, then the researchers should have seen a sort of correlation or even a simple link between territorial range and spatial ability. No such thing, however. The scientists found that in the eight out of eleven species where males showed better spatial reasoning than females, this behavior applied regardless of territory size or the extent to which male ranges spanned farther than female ranges. So even though females roamed just as much as males, they still weren’t as good at making their way around as males.

“We find no support for the hypothesis that species differences in home range size dimorphism are positively associated with parallel differences in spatial navigation abilities.”

“The alternative hypothesis that sex differences in spatial cognition result as a hormonal side effect is better supported by the data,” the authors write.

And the key hormone that the researchers believe is actually driving better spatial reasoning is testosterone. Navigational abilities may be a side effect of higher testosterone levels: previous studies have shown that women who take testosterone tend to see an improvement in their spatial navigation abilities.

What’s more important to take away from this, however, is that while a theory might seem intuitive, it might be flawed and showed be considered flawed until solid evidence is brought on the table. An unfounded theory is not a theory, but a story.

The findings of the present study were reported in The Quarterly Review of Biology.