TERRA COGNITA: Rat pups emerge from the nest with many of the navigational cells they need to find their way around their environment just fine.
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Not everyone has a perfect sense of direction, whether they would like to admit it or not. But two new studies have found that even baby rats have a basic spatial framework in their brains ready to use as soon as they leave the nest for the first time—which is much earlier than had previously been documented.
The findings reveal that not all sense of space is learned. They show that at least some of that sense is innate, "that the basic constituents of the cognitive map develop independently of spatial experience or might even precede it," noted the authors of one of the new studies, both published online June 17 in Science.
For the two independent studies researchers record rats' neuronal firings as soon as newborn pups opened their eyes and began to explore their surroundings. Both teams were surprised to find adult-level cell function in some of the directional regions.
At this age, "the animals would not yet have had a chance to explore the environment beyond their nest," Francesca Cacucci, a researcher at the Institute of Behavioral Neuroscience at University College London and co-author of one of the papers, writes in an e-mail. "This suggests strongly that sense of direction is independent of spatial experience."
And because the mammalian hippocampus is relatively consistent in its make-up across species, these lab rat–based findings likely mirror a similar developmental trajectory in humans.
Other abilities, such as face perception or language use, are thought to be innate. But "space is such a basic cognitive function, and to have it be partly innate is really interesting and groundbreaking work," says Linda Palmer, a project scientist at the Department of Anatomy and Neurobiology at the University of California, Irvine, who coauthored a perspectives essay accompanying the two studies in Science.
Three-celled mapping
To navigate a space, mammals seem to need only three basic types of cells, and the new finding suggests that they are ready to fire up in the brain at a very early age.
These cells reside in the hippocampus and record direction (where the head is pointing), place (location in an environment), and grid (distance covered while moving).
In both studies researchers implanted electrodes in the brains of the rat pups about 14 days after birth. Before that age rat pups remain, eyes sealed shut, in the nest. As soon as their eyes open, however, the young pups begin to explore their environment.
"As soon as the baby rat is able to leave the nest it has the basic foundations of a neural map of the environment ready to use," Rosamund Langston, a lecturer in behavioral neuroscience at the Ninewells Hospital and Medical School in Scotland and lead author on the second study, notes in an e-mail.
The most developed cells were the head-direction cells, which "are there, fully fledged," as soon as the mouse opens its eyes and begins to explore, Palmer says.
Although these directional cells are functioning at near-adult levels early, there is a period of refinement over the next two weeks in which the place and grid cells develop more fully, suggesting that some spatial experience and learning might be involved. Place cells were first recorded at 16 days after birth in both experiments, but there was some discrepancy as to the grid cell emergence: Langston and her colleagues at the Kavli Institute for Systems Neuroscience at the Norwegian University of Science and Technology recorded early grid cells at day 16, whereas Cacucci and her group documented more mature ones at day 20.
That grid cells—presumed to record the distance an animal has traveled—developed after place cells was "unexpected," Cacucci noted. Both anatomically and computationally the reverse order would have seemed more likely because distance would help inform place cells, she said.
Global orientation
The new research explains the neuronal development of young rats as they explore their basic surroundings, but this process might seem much different than, say, birds navigating across continents or humans driving in an unfamiliar city.
Palmer explains that our larger sense of location and orientation (how a room fits into a building, which fits into a block, which fits into a city, etcetera) might simply be an extension of this basic, hippocampal cell–based understanding of our surroundings. As our known environment becomes more expansive, we assemble that into a larger representation, she speculates.
So why is it that some people always have to ask for directions (or refuse to even if they are lost)? This variability has not yet been pinned down at the neuronic level. In the rats there did not seem to be notable differences in the rate or onset of cell firing. "They have different characters or 'personalities' but all have these same neuronal signals," Langston noted, adding, however, that lab rats are bred to be as similar as possible for the sake of experiment replication.
Also, the researchers only observed the rats exploring a neutral enclosure and did not test the rats by pushing their individual navigational abilities to make a comparison between neuronal functioning and development. "We do not know whether having the neuronal correlates of space is a reflection of how well you can actually find your way around," Langston explained.
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9 Comments
Add CommentI'm not aware of any scholarly debate about the navigational skills of men versus women, but there often seems to be a conflict whenever both are a little lost together.
Reply | Report Abuse | Link to thisI understand it's been previously noted that men primarily seem to try to envision the spatial layout of the desired path, whereas women primarily look for critical landmarks along the way. Success seems to depend mostly on the complexity of the potential paths, the availability of landmarks along the desired path and the intensity of disagreement...
"Being able to construct a maplike concept of a space, however, does not occur until about 21 days after birth in ratsand nine months in babiesboth ages around the time of weaning, she pointed out."
Reply | Report Abuse | Link to thisI find it very odd that Cacucci thinks that nine months is "around the time of weaning" for humans. According to anthropologist Katherine Dettwyler, PhD, "The minimum predicted age for a natural age of weaning in humans is 2.5 years, with a maximum of 7.0 years."
My daughter weaned at 4 1/2 years and my son is still going strong at 3 1/2.
I have known for a long time that the internal map is not related to the external information. I always take the wrong turn and get lost easily. I tell myself where things ought to be but my brain tells me differently. I thought I was dyslexic. Because my mother language is Spanish, phonetic all the way, I never had problems learning to read. I did very well in school and have a PhD in quantitative Sociology. But I get lost inside buildings and have no sense of direction at all! I depend on my GPS.
Reply | Report Abuse | Link to thisIs there an innate sense of direction: I would suggest that there is but that it can be observed in a person with Acquired Brain Injury. As a person with same, I find this article most interesting. The suggestion that baby rats have a basic spatial framework that activates when they leave the nest interests me. The grid and idea of distance is also interesting.
Reply | Report Abuse | Link to thisAged 32 and following a riding accident; a fractured skull, speech, sight, mobility/balance problems, hearing, I found that while I could operate in a limited and basic spatial framework, it was the loss in memory span, attention and cognitive abilities that caused me to lose orientation. This then created a form of anxiety and frustration and the critical comparison. As the years lapsed the comparison became more acute as my memory became episodic. The grid failed to measure distance hence complicating life further.
My point is that nearly 20 years into living with an episodic memory and having gone through the painful endeavours of trying to get myself out of muddled states, I realised that my flaw was that I was thinking pre-accident and spatial capability at that time and this caused the anxiety which in turn caused unwarranted confusion hence the problem. Therefore according to the theory raised in this article, there could be an innate sense of direction but hampered by temperament and anxiety.
The irony is and the reason I believe that there is something innate about the spatial concept is that I early on recognised that if I returned to living in a geographic area that I knew well both driving, walking and living in, then I could cope more successfully with the ABI but at a slower pace of living. This has proved to be a wise decision.
Science is about learning and I appreciate that one must study the performance of the rat population but sometimes I wish that the person who has the experience of ABI, illness, experience is not consulted.
Michelle
Is there an innate sense of direction: I would suggest that there is but that it can be observed in a person with Acquired Brain Injury. As a person with same, I find this article most interesting. The suggestion that baby rats have a basic spatial framework that activates when they leave the nest interests me. The grid and idea of distance is also interesting.
Reply | Report Abuse | Link to thisAged 32 and following a riding accident; a fractured skull, speech, sight, mobility/balance problems, hearing, I found that while I could operate in a limited and basic spatial framework, it was the loss in memory span, attention and cognitive abilities that caused me to lose orientation. This then created a form of anxiety and frustration and the critical comparison. As the years lapsed the comparison became more acute as my memory became episodic. The grid failed to measure distance hence complicating life further.
My point is that nearly 20 years into living with an episodic memory and having gone through the painful endeavours of trying to get myself out of muddled states, I realised that my flaw was that I was thinking pre-accident and spatial capability at that time and this caused the anxiety which in turn caused unwarranted confusion hence the problem. Therefore according to the theory raised in this article, there could be an innate sense of direction but hampered by temperament and anxiety.
The irony is and the reason I believe that there is something innate about the spatial concept is that I early on recognised that if I returned to living in a geographic area that I knew well both driving, walking and living in, then I could cope more successfully with the ABI but at a slower pace of living. This has proved to be a wise decision.
Science is about learning and I appreciate that one must study the performance of the rat population but sometimes I wish that the person who has the experience of ABI, illness, experience is not consulted.
Michelle
I apologize in advance for my cryptic reflex comments sans the benefit of reading the complete report. Genetic memory is about the species in its habitual habitat + archetype genes to be influenced by environmental circumstances presenting a threat to its biological integrity. Claiming that we inherit the ability to orient ourselves in ecological niches unfamiliar to our species constitutes a categorical error UNLESS either we are thinking in archetypes being able to conceptually infer a probable solution for a new spatial (or otherwise ,, see Jacques & Monod) contingency OR that we suscribe to the idea of being able to inherit acquired data absent from their genetic endowment, a la Lysenko, i.e., extragerminal cell inheritance. This aspect should be expanded by the author. Dr.d
Reply | Report Abuse | Link to thisIt is an interesting reconsideration of Kant's aesthetics (his theory of space and time as synthetic a priori intuitions). I'm sure that research in this direction will reveal interesting things in the future. Particularly in relation to our intuition of time.
Reply | Report Abuse | Link to thistime, hmmm?
Reply | Report Abuse | Link to thisthe point is that we Are born with this particular sense; and rapidly develop its attachments.
I think I found "physiological evidence" that we have synthetic a priori intuition of space, as Kant asserted. But this will be the subject of a separate scientific communication (whether I will survive in this crisis). However, these investigations seem to lead decisively in the direction of Kantian aesthetics confirmation and denial of Locke's empiricist theory that our mind is in its relationship with the "objective reality" out there, a tabula rasa.
Reply | Report Abuse | Link to thisI wrote a book on this subject, but unfortunately I have not yet translated into English only a few pages.
http://www.scribd.com/doc/17474184/Marcel-Chelba-Kantian-tetralogy-Vol-I-Critical-Introduction-Kantinomus