New understanding of brain’s early spatial development

Researchers at the University of Bath have uncovered a new understanding of how the brain develops its sense of space by working with blind people.

The researchers from the University’s Department of Psychology found that people who lose their sight later in life use a different method of following directions to those who are born without sight. This means that the brain needs to have a visual experience early on in life in order to build a visual perspective, or frame of reference, to know what is where.

The researchers carried out a study with participants including those who were congenitally blind; those who became blind later in life; and others who were sighted, to learn which methods the different groups used to remember where things are.

The study revealed that people who have been sighted and then become blind use a ‘allocentric’ reference frame, meaning they remember locations as they are positioned relative to one another, and this is the same as sighted people who do this task, even when blindfolded.

In contrast congenitally blind participants preferred an ‘egocentric’ reference frame meaning they first remember a starting point at home and then store a memory of the locations from the home location. Dr Michael Proulx who led the study said the results help us to understand more about the role of a critical period for developmental vision on spatial cognition and brain organisation.

He said: “In our study we were curious as to whether having visual experience during child development was key to creating the structures in the brain to support such an allocentric reference frame. First we found an interesting difference between the congenitally blind and sighted people: although the sighted people preferred the allocentric, reference frame, the congenitally blind participants preferred the self-centred or egocentric reference frame for remembering locations.

“The important piece of the puzzle, however, was whether the late blind people would perform like the congenitally blind, showing that current visual experience matters, or like the sighted, showing the role of early visual experience. The results were clear: the late blind performed the same as the sighted participants. Therefore having the experience of vision early in life lays the groundwork in the brain for the representation of locations in a different reference frame than that found in people who never had visual experience.”

All of the participants of the study were blindfolded and then walked to the locations of objects in a large room. They were later tested on a computer with a virtual pointing task that asked them to remember objects in the room relative to the other object locations.

Dr Proulx and his colleagues are following up this finding with additional research to investigate how additional information, such as the texture or sound of the environment, might influence the frame of reference used.

This would allow for improved maps rendered in Braille or sound to be produced for visually impaired persons to use in public places, such as rail stations, or in new cities.

They are also examining the impact of visual experience on the neural basis for spatial learning and memory by examining how the congenitally blind and late blind brains represent spatial information in the absence of vision.

My mistake or yours? How the brain decides

Humans and other animals learn by making mistakes. They can also learn from observing the mistakes of others. The brain processes self-generated errors in a region called the medial frontal cortex (MFC) but little is known about how it processes the observed errors of others. A Japanese research team led by Masaki Isoda and Atsushi Iriki of the RIKEN Brain Science Institute has now demonstrated that the MFC is also involved in processing observed errors.

The team studied the brains of monkeys while the animals performed the same task. Two monkeys sat opposite each other and took turns to choose between a yellow and green button, one of which resulted in a liquid reward for both. Each monkey’s turn consisted of two choices.

After blocks of between 5 and 17 choices, the button that resulted in reward was switched unpredictably, usually causing an error on the next choice. The choices made by each monkey immediately after such errors, or errors that were random, showed that they used both their own errors and their partner’s to guide their subsequent choices. While the monkeys performed this task, the researchers recorded activity of single neurons in their brains.

In this way they were able to determine which behavioural aspect was most closely associated with each neuron’s activity, explains Isoda. “We found that many neurons in the medial frontal cortex were not activated when the monkey made an error itself, but they became active when their partner made an error.” This brain activity shows that it is the MFC which processes observations of another’s error, and the corresponding behavior shows that observing and processing such errors guides subsequent actions.

“Such error identification and subsequent error correction are of crucial importance for developing and maintaining successful social communities,” says Isoda. “Humans are tuned into other people’s mistakes not only for competitive success, but also for cooperative group living. If non-invasive techniques become available in humans, then we should be able to identify medial frontal neurons that behave similarly.”

Having identified the MFC as being involved, Isoda now wants to delve deeper into the process. “The next steps will be to clarify whether the inactivation of medial frontal cortex neurons reduces the ability to identify others’ errors, and to determine whether other brain regions are also involved in the processing of others’ errors.”

The pilot and autopilot within our mind-brain connection

Have you ever driven to work so deep in thought that you arrive safely yet can’t recall the drive itself? And if so, what part of “you” was detecting cars and pedestrians, making appropriate stops and turns? Although when you get to work you can’t remember the driving experience, you are likely to have exquisite memory about having planned your day.

How does one understand this common experience? This is the question posed by Professor of Biology, John Lisman and his former undergraduate student, Eliezer J. Sternberg, now in medical school, in a recent paper in the Journal of Cognitive Neuroscience. Lisman explains that once a task such as driving has become a habit, you can perform another task at the same time, such as planning your day. But looking closer at these two behaviors, driving and planning, one can see interesting differences. The Habit system that is driving you to work is non-flexible: if the new parking regulations at work require you to go left instead or right, the likelihood that you’ll go right is very high. On the other hand, if you heard yesterday that your boss has scheduled a group meeting for noon, the likehood that you’ll plan your day accordingly is high. In other words, your non-habit system is flexible.

What interests Lisman and Sternberg is the relationship of the habit/non-habit systems to concepts of conscious vs unconscious. These concepts were popularized by Freud, who posited a duality of the human mind. Behavior can be influenced by both the conscious system and unconscious system. Freud compared the mind to an iceberg——with the small conscious system above water and the larger unconscious system below. Modern cognitive neuroscience now accepts this duality.

The mind can be described as having an unconscious and conscious part. And the brain can be described as having both habit and non-habit systems. Lisman and Sternberg argue that these two views can be merged: there is a habit system of which we are unconscious and a non-habit system of which we are conscious.

This simple equation turns out to have enormous implications for research on the mind-brain connection. Experiments on consciousness are done in humans because you can ask them to report their awareness, something you can’t do with animals. On the other hand, there are many invasive procedures for studying what’s happening in the brain of animals. So how can you study consciousness in rats?

Lisman and Sternberg provide a simple answer — ask whether rats have habit and non-habits. Scientific literature demonstrates that rats indeed have both habits and non-habits. For instance, when a rat comes to a choice point on a maze (and the reward site is to left), rats display very different behavior depending on how much experience they’ve had with that maze. With relatively little experience, rats pause at the choice point and look both ways before making a decision; in contrast, a highly experienced rats zooms left without stopping. Experiments have shown that different parts of the brain are involved in these two phases. Lisman and Sternberg make two conclusions: first, that rats, like us, have conscious and unconscious parts of the brain and second, that from experiments on rats we can learn to identify the parts of the brain that mediate conscious vs unconscious processes.

In their paper, Lisman and Sternberg also discuss potential objections to their hypothesis, and suggest further tests.

(Photo: GETTY)

Dopamine regulates the motivation to act

The widespread belief that dopamine regulates pleasure could go down in history with the latest research results on the role of this neurotransmitter. Researchers have proved that it regulates motivation, causing individuals to initiate and persevere to obtain something either positive or negative.

The neuroscience journal Neuron publishes an article by researchers at the Universitat Jaume I of Castellón that reviews the prevailing theory on dopamine and poses a major paradigm shift with applications in diseases related to lack of motivation and mental fatigue and depression, Parkinson’s, multiple sclerosis, fibromyalgia, etc. and diseases where there is excessive motivation and persistence as in the case of addictions.

"It was believed that dopamine regulated pleasure and reward and that we release it when we obtain something that satisfies us, but in fact the latest scientific evidence shows that this neurotransmitter acts before that, it actually encourages us to act. In other words, dopamine is released in order to achieve something good or to avoid something evil", explains Mercè Correa.

Studies had shown that dopamine is released by pleasurable sensations but also by stress, pain or loss. These research results however had been skewed to only highlight the positive influence, according to Correa. The new article is a review of the paradigm based on the data from several investigations, including those conducted over the past two decades by the Castellón group in collaboration with the John Salamone of the University of Connecticut (USA), on the role of dopamine in the motivated behaviour in animals.

The level of dopamine depends on individuals, so some people are more persistent than others to achieve a goal. “Dopamine leads to maintain the level of activity to achieve what is intended. This in principle is positive, however, it will always depend on the stimuli that are sought: whether the goal is to be a good student or to abuse of drugs” says Correa. High levels of dopamine could also explain the behaviour of the so-called sensation seekers as they are more motivated to act.

Application for depression and addiction

To know the neurobiological parameters that make people be motivated by something is important to many areas such as work, education or health. Dopamine is now seen as a core neurotransmitter to address symptoms such as the lack of energy that occurs in diseases such as depression. “Depressed people do not feel like doing anything and that’s because of low dopamine levels,” explains Correa. Lack of energy and motivation is also related to other syndromes with mental fatigue such as Parkinson’s, multiple sclerosis or fibromyalgia, among others.

In the opposite case, dopamine may be involved in addictive behaviour problems, leading to an attitude of compulsive perseverance. In this sense, Correa indicates that dopamine antagonists which have been applied so far in addiction problems probably have not worked because of inadequate treatments based on a misunderstanding of the function of dopamine.

Is There a Period of Increased Vulnerability for Repeat Traumatic Brain Injury?

Repeat traumatic brain injury affects a subgroup of the 3.5 million people who suffer head trauma each year. Even a mild repeat TBI that occurs when the brain is still recovering from an initial injury can result in poorer outcomes, especially in children and young adults. A metabolic marker that could serve as the basis for new mild TBI vulnerability guidelines is described in an article in Journal of Neurotrauma, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available on the Journal of Neurotrauma website.

In an Editorial, “The Window of Risk in Repeated Head Injury,” accompanying this article, John T. Povlishock, PhD, Editor-in-Chief of Journal of Neurotrauma and Professor, VCU Neuroscience Center, Medical College of Virginia, Richmond, states that recent studies of TBI in animal models have shown that while repeat injury can exacerbate structural, functional, metabolic, and behavioral responses, “these responses only occur when the injury is repeated within a specific time frame post-injury.”

"Specifically, this window of risk is greatest when the interval between injuries is short, hours to days, while any risk for increased damage is obviated when the intervals between injuries are elongated over days to weeks," says Dr. Povlishock. It is not yet clear if these time periods of increased risk are age- or gender-specific or depend on the intensity of the initial injury.

A consistent finding following TBI in both humans and animal models is a decrease in glucose uptake by the brain. Mayumi Prins, Daya Alexander, Christopher Giza, and David Hovda, The UCLA Brain Injury Research Center, Los Angeles, CA, simulated single and repeat (after 1 or 5 days) mild TBI in rats and measured cerebral glucose metabolism. They tested the hypothesis that the rats’ brains would be more vulnerable to the damaging effects of repeat TBI at 1 day post-injury, when glucose metabolism was still decreased, than at 5 days, when it had returned to normal levels.

In the article, “Repeat Mild Traumatic Brain Injury: Mechanisms of Cerebral Vulnerability,” the authors propose that the duration of metabolic slowdown in the brain could serve as a valuable biomarker for how long a child might be at increased risk of repeat TBI.

Researchers Find Causality in the Eye of the Beholder

We rely on our visual system more heavily than previously thought in determining the causality of events. A team of researchers has shown that, in making judgments about causality, we don’t always need to use cognitive reasoning. In some cases, our visual brain—the brain areas that process what the eyes sense—can make these judgments rapidly and automatically.

The study appears in the latest issue of the journal Current Biology.

“Our study reveals that causality can be computed at an early level in the visual system,” said Martin Rolfs, who conducted much of the research as a post-doctoral fellow in NYU’s Department of Psychology. “This finding ends a long-standing debate over how some visual events are processed: we show that our eyes can quickly make assessments about cause-and-effect—without the help of our cognitive systems.”

Rolfs is currently a research group leader at the Bernstein Center for Computational Neuroscience and the Department of Psychology of Berlin’s Humboldt University. The study’s other co-authors were Michael Dambacher, post-doctoral researcher at the universities of Potsdam and Konstanz, and Patrick Cavanagh, professor at Université Paris Descartes.

We frequently make rapid judgments of causality (“The ball knocked the glass off the table”), animacy (“Look out, that thing is alive!”), or intention (“He meant to help her”). These judgments are complex enough that many believe that substantial cognitive reasoning is required—we need our brains to tell us what our eyes have seen. However, some judgments are so rapid and effortless that they “feel” perceptual – we can make them using only our visual systems, with no thinking required.

It is not yet clear which judgments require significant cognitive processing and which may be mediated solely by our visual system. In the Current Biology study, the researchers investigated one of these—causality judgments—in an effort to better understand the division of labor between visual and cognitive processes.