Some neurons puts the brakes on learning

by Tanja Jensen

Our memories are stored in the connections between neurons, and while our brain has mechanism to store memories it also has mechanisms to forget. Or stop learning all together. Now, one of the learning mechanisms has been unraveled at a cellular level.

IMG_6806A research team at Lund University in Sweden studied something called associative learning, by recording activity in ferrets´s Purkinje cells. Purkinje cells are neurons that cause movements, such as blinking. The ferrets learned to associate a specific tone or light beam with a puff of air to the eye, which then blinks. After repeating the procedure of presenting a tone or light beam together with an air puff, the ferrets soon started to blink already when they heard the tone or saw the light – even when no air was puffed at the eye.

Purkinje cells release the brakes on the active cerebellar nuclei, an output structure in the brain. However, while the signal from the cerebellar nuclei tell the eye to blink in response to a tone or beam of light, their activity also leads to putting the brakes on a different structure altogether, called the inferior olive. This structure leads to blinking in response to the air puff – a reflex – and all the events of activities suggest a loop controlling learning.

This learning is the same type of learning described by Pavlov, when he experimented on his dogs´ drooling. Pavlov rang a bell and then fed the dogs. Soon the dogs started drooling, expecting food, as soon as Pavlov rang the bell. While Pavlov observed the associative learning, many researchers have since tried to tease apart the underlying cellular mechanisms, which the Lund University researchers now have done.

Learning gets worse with two cues presented together

They describe how Purkinje cells learn and forget. Their recordings of the cells´ activity connect them to associative learning. When the team presented the tone and the light together, and at the same time as the air puff, the ferret´s learning to associate the cues with the air puff did not improve. It got worse.

The research team believes the neurons puts the brakes on further learning to save energy, as maintenance of association pathways consumes energy. And the brakes can become very powerful. That results in forgetting.

While the cellular mechanisms of neurons acting as brakes are described for animals in this study, it is not unlikely that the same cognitive process is at play in humans. As such, the finding may contribute to more efficient learning tools.

 

The study was recently published in PNAS

Leave a comment

Filed under Cognition

Manipulative parasite reprograms the host´s brain to take more risks

By Tanja Jensen

The parasite toxoplasmos gondii is a manipulative engineer, leaving its host´s brain with genetically altered machinery. A scratch by a cat and an unlikely path may follow leading up to changes in behaviour, with reprogramming of the brain itself as a consequence.

Cats are carries of the parasite toxoplasmos gondii. When the parasite´s spores enter the bloodstream, they form cysts that bury themselves in the muscles and the brain

The parasite´s life is a cycle with various stages. To go through a full cycle the parasite needs the cat as its host. This means it somehow has to get back to the cat from a, say, a girl or a rat. How can the parasite possibly pull this off? This would mean it has to get the girl or the rat to fancy cats. Strikingly, that´s exactly what it does.

Toxoplasmos makes women aggressive, men impulsive and rats drawn to cats

The amazing findings by the researchers Hari Dass and Vyas at Nanyang Technological University in Singapore, show that the parasite has a repertoire of epigenetic (deliberately turn genes on and off) engineering techniques to manipulate the phenotype of rats. That is, the function or characteristics of the gene changes, but the code stays the same.

This means that the parasite reprograms the rat brain. It rewires the connections in the amygdala, sometimes referred to as the fear centre.

Just like the brakes of a car are used by some to slow down before a curve, our amygdala signals fear and tells us to be suspicious. And just like the bad guys in some movies tamper with the brakes to get the driver into an accident, toxoplasmos gondii tampers with the genes of its host to change neural processes and behaviour.

Interestingly, when rats are infected they are no longer afraid of cats, since they lose their natural aversion to cat smell, and instead become attracted to them.

http://www.ncbi.nlm.nih.gov/pubmed/23225875When people are infected, their behaviour change. Women become (more) aggressive and men become (more) impulsive, as shown by Dan Rujescu, at Martin-Luther-University Halle-Wittenberg in Germany and Teodor T Postolache at University of Maryland-Baltimore School of Medicine in USA. The infection is possibly associated to some neuropsychiatric disorders, like schizophrenia too.

Nearly one in three persons is infected with toxoplasmos (which also prolongs reactions times by the way). Perhaps aggressive women and impulsive men can get targeted treatment for the toxoplasma parasite? Imagine what that would lead to during rush hour.

Leave a comment

Filed under Okategoriserade

Not so novel after all

by Tanja Jensen

In my previous post, I describe the seemingly new findings of lymphatic vessels in the brain.

However, this issue of Nature comments on the novelty of the research and show other studies describing the brain´s lymphatic vessels.

Nature concludes that “Perhaps old papers that are not available as online PDFs are easily overlooked in today´s literature searches, depriving many of our scientific predecessors of the recognition they deserve.”

Leave a comment

Filed under Cognition

Vessels in the limelight link the immune system with the brain

by Tanja Jensen

The news that the lymphatic vessels reach into the brain (right) will likely rewrite text books.  Image credit: University of Virginia Health System

The news that the lymphatic vessels reach into the brain (right) will likely rewrite text books. Image credit: University of Virginia Health System

Scientists found vessels directly linking the brain with the immune system. Jonathan Kipnis and his team at University of Virginia found that the vessels actually exist – despite the common belief that the brain lacks a lymphatic system, that is, a drainage system for fluid and immune cells typical for the rest of the body. As such, the team´s finding may turn out to open up for new research areas and change existing ones, and thereby answer how the immune system attacks the brain.

The immune response of neurological disorders, like multiple sclerosis (MS) or perhaps Alzheimer´s, is poorly understood. That the immune system somehow attacks the brain in MS is known. However, in Alzheimer´s chunks of proteins pile up in the brain, the scientists suggest, perhaps because the vessels fail to drain them out.

Immune cells exit and enter the central nervous system, that is, the brain and spinal cord, non-stop. In search for how a certain type of immune cells, the T-cells, move into and out of the central nervous system in mice, the team of researchers by chance came across the well-hidden lymphatic vessels.

The team studied the membranes covering the brain, the meninges, and noticed the pattern of lymphatic vessels in the microscope. To find out if the pattern indeed was caused by lymphatic vessels, they tested for it, in action in live mice, by imaging.

The linking vessels are a game changer in the world of science. And the finding, published in Nature, sheds new light on the cause of certain brain disorders linked to the immune system attacking the brain. Although the reasons for neurological disorders, like MS and Alzheimer´s, are poorly understood, it´s likely that the vessels might play a role. This opens up for new opportunities to study the diseases plaguing the brain.

Find images and information about the research team here.

 

Leave a comment

Filed under Okategoriserade

Can the ´love´ hormone help depressed mothers bond with their baby?

by Tanja Jensen

Credit to GaborfromHungary

Credit to GaborfromHungary

Nasal spray with the ´love´ hormone oxytocin seems to help depressed moms to better bond with their newborn baby. This is promising news, since moms with postnatal depression lack oxytocin. The hormone plays an important role in mother-infant bonding, with lasting effects on the child´s social development, such as social engagement with others and their capacity for empathy.

To simplify treatment of postnatal moms, neuroscientist Jaak Panksepp and his team at Washington State University in USA and University of Trieste in Italy, bridged neuroscience and psychology. The research team believes these disciplines complement each other and, therefore, bridged certain aspects of emotional brain issues with psychoanalytical concepts about how the mind works.

Oxytocin, is well known to strengthen social behavior and, in particular, have antidepressant effects. The hormone, which is active in the central nervous system (the brain and spinal cord) also raises people´s feelings of commitment, in the sense that the hormone seems important to lower self-centered activities in moms and strengthen their concern along with confidence to handle the baby´s needs.

Oxytocin strengthens social behavior

 

Based on these effects, Panksepp and his team wanted to find out whether oxytocin could have any therapeutic effect on moms with postnatal depression, that is, depression and other symptoms like flattened affect and irritability, appearing within a few weeks after giving birth.

The researchers therefore studied 16 moms for 12 weeks. All the moms took part in psychotherapy once weekly and also used nasal spray with either oxytocin or placebo.

Strikingly, there was no difference on depressive symptoms between the moms in the two groups. Instead, Panksepp and his colleagues realized that oxytocin lowered the mom´s narcissistic, or self-centered, trait.

Postnatal depression seems to

include a disturbed sense of self

 

It turns out that oxytocin eased acceptance of and interaction with the newborn. This improved the mom´s ability to recognize her baby´s needs. So what is generally defined as postnatal depression, in fact, also seems to include a disturbed sense of self, or narcissistic balance. And oxytocin counteracts this. At least as it seems.

Although Pankseep and the team did a small study, it still serves as a pointer. The researchers showed that oxytocin might ease the self-centered dimension of postnatal depression, rather than the depressive symptom itself. If the results are confirmed, then preventive measures could be implemented as treatment. This means that mom´s and their infants could get help to bond during a critical time that tends to affect the rest of the child´s life.

The paper was recently published in Frontiers in Psychology.

Leave a comment

Filed under Cognition

Potential haywire behind spooky intruder

by Tanja Jensen

http://mrg.bz/CykjQN

image credit jkt_de

Going to bed alone and waking up in the middle of the night with company is probably not what most people wish for, yet it is not uncommon. At least as it seems.

Some sleepers see, hear and sense a terrifying, shadowy intruder in their bedroom. About 18-40 % of the population perceives an intruder in their sleep and for the majority, the events occur due to sleep irregularities like jet lag.

The arising of an intruder made the neuroscientists Vilayanur Ramachandran and Baland Jalal at University of California curious. What happens in the brain when, in a seemingly empty room, sleepers perceive an intruder? Some argue visit from the other side, while the researchers Ramachandran and Jalal suggest a different reason.

They suggest that the intruder may be caused by a brain wiring conflict in a very specific region of the brain called the right parietal cortex. And they think that the intruder arises when the brain processes sensory information from many sources of the body and the self. Simply put, the brain is hallucinating your genetically wired body image, the researcher think, and it occurs in the same circuits in the right parietal region that forms our sense of our body shape as well as sexual preference.

Your intruder occurs during sleep paralysis, possibly due to a projection of your body image 

 

The underlying cause arises during sleep paralysis, which is common when we are just about to fall asleep or are about to wake up. During sleep paralysis we are, just as the word implies, paralyzed, while our senses are clear.

Some sleepers move into wakefulness before muscle paralysis has waned and dream with their eyes open. Since all senses are involved, the dreaming leads to a hallucination where the sleeper sees, hears, senses a shadowy intruder. The intruder is mostly interpreted in ways to fit with cultural ideas, since it often lacks clear facial features. Sometimes the intruder also assaults the sleeper by, for example, strangling him or her.

One way to find out whether the intruded indeed is caused by haywire, is to study individuals with a distorted body image, such as in those with anorexia nervosa, the researchers suggest. If these individuals’ irregular body image is genetically acquired, then their shadowy intruders would mirror their bigger internal body image.

If the researchers are right, they would offer a neurological explanation of the shadowy intruder that causes great horror in many sufferers.

The study was published in Medical Hypotheses.

 

Presentation1

1 Comment

Filed under Cognition

Cross your fingers to numb your pain

http://www.morguefile.com/archive/display/824922

by Tanja Jensen

The pattern of hot and cold stimulation affects how you feel physical pain, and crossing your fingers can change the pain you feel on a single finger, show researchers at University College London (UCL).

Angela Marotta and Elisa Raffaella Ferrè wanted to find out whether sensory pain depends on spatial or somatotopic (related to particular areas of the body) cues.

Using the thermal grill illusion, an established pain experiment, the UCL research team used a pattern of warm and cold temperatures applied to the fingers to find out.

When the UCL research team presented the pattern warm-cold-warm temperatures to the ring, middle and index finger respectively, this caused a sensation of heat on the middle finger, even though this finger was presented with cold.

The thermal grill illusion confuses the brain to sometimes feel pain or burning heat, even though a cold stimulus is applied to the skin. In the thermal grill illusion neural pathways interact. Simply put, the pain and warmth signals override the cold signal, which is then blocked. Since cold normally blocks pain, the warmth now gives rise to a sensation of pain.

The burning sensation in the cold finger vanished when it crossed over the warm index finger.

Strikingly, the fingers´ stimulation pattern of hot and cold greatly affects the pain level, the researchers show. The burning sensation caused by the thermal grill effect vanished, when the cold middle finger crossed over the index finger. What else is, pain spawned when, instead, the index finger was cold, and the warm middle finger crossed over it.

Amazingly, these findings suggest that the thermal grill illusion can be tampered with. Stimulation pattern rather than body posture may determine sensory perception of pain.

So how can I use this research to ease my pain, you wonder? You can´t. Yet. But since the mechanisms, underlying spatial body representation to pain perception, is still unclear, the findings raise interesting possibilities. Perhaps neural pathways underlying pain perception, could be tampered with by changing the spatial pattern of interacting stimulation?

The results were published in the journal Current Biology.

 

Leave a comment

Filed under Pain

Neuroplasticity – our changing brain

by Tanja Jensen

Image credit Taylor Maley/Flickr

Image credit Taylor Maley/Flickr

 

What is neuroplasticity? Simply put, it means our brain, along with the rest of the nervous system, is adaptable. In this sense, our experiences have the ability to change our brain – at any age. Our brain re-wires.

Neuroplasticity is a term I have used in quite a few of my post. Most likely, I will use the term in future posts as well. But what is neuroplasticity?

Think of the brain as orderly wires carrying information. Special, orderly wires with the power of Play Doh to remodel themselves.

Our brain is soft-wired, as neuroscientist Michael Merzenich puts it, with the potential to change. This means that the adult brain possesses an ability to create and fuse new neurons, and re-wire existing neural circuits. It does this in mainly three ways.

  1. Neurogenesis. This is the birth and integration of new neurons (brain cells) into existing neural pathways.
  2. Synaptic plasticity. Information from one neuron to another flows across a synapse, a neural intersection. Synaptic plasticity means synapses are added, removed or changed. When changed, the synapses´ efficiency to communicate strengthens or weakens. Activity strenghtens pathways. Passivity withers pathways.
  3. Myelination. Just like electrical wires have a sheath of insulation, so do axons – the bundle of wires making up nerves. This insulation is called myelin and consits by a type of brain cells called oligodendrocyte. The development of a myelin sheath increases or decreases depending on activity patterns in the neural circuits. Myelination speeds up processing, or communication in the nervous system.

Considering how this comes about is when it´s get really exciting. Neurons communicate with each other over the synapses, through the help of chemical messengers called neurotransmitters. These are released by an electrical impulse. A new impulse is ignited when the neurotransmitter docks on the neighbouring neuron – carrying the impulse forward to its destination.

The neural impulses are a code. They are a code for your thoughts and everything else that is going on in your brain to run the machinery – your body. To run your body smoothly, the brain is dependent on signals from various parts of your body, to inform it about what your hand is up to, if the food smells foul or even what you are thinking. The brain is constantly bombarded with sensory information screaming for attention.

Amazingly, also fantasies have nearly the same effect on shaping the brain as real experience.

The brain sifts through this information to respond appropriately. And in the process it´s being shaped by it. Thoughts, emotions, actions, feelings. All experiences continually alter the neural pathways. Their structure reorganize and their function change.

Neuroplasticity can also help injured brains grow. There are many things you can do to keep your brain health and fight of brain aging. Trying new things for example. Exercise and food also plays an important role for brain health. Doing demanding tasks or thinking differently does too. The list can be made long. Amazingly, also fantasies have nearly the same effect on shaping the brain as real experience [1]. Imagine that!

The daily activities you choose to engage in can contribute to optimize your brain and maintain a healthy brain. The result is an optimized response, created by the brain, to the world around us and within us. So challenge yourself, be focused and do some hard work to reap the benefits of your plastic brain.

 

 

For further reading about neuroplasticity and concrete examples to improve yourself check out neuroscientist Michael Merzenich´s book Soft-Wired.

 

1 Comment

Filed under Okategoriserade

Hope for new Alzheimer´s therapy

by Tanja Jensen

A new treatment for Alzheimer´s disease shows positive results, say researchers at Karolinska Institute in Sweden. By surgically placing protein covered implants in the patients´ brains, they could slow down the pace at which, so called cholinergic, neurons wither and die.

Although the research team can see a clear link between the treatment and worsening of nerve function, they firmly point out that it is still far too early to tell whether the treatment is going to work in the long run.

image credit #13min/Flickr

image credit #13min/Flickr

The implants they used were covered with the protein called nerve growth factor, which is important for growth, survival and maintenance of neurons. Nerve growth factor wanes in Alzheimer´s disease, and this is thought to be coupled to the breakdown of cholinergic neurons. Cholinergic neurons produce acetylcholine – a molecule communicating between neurons and important for learning and memory. 

Six patients had the implants for a year. Then markers from the cholinergic neurons were analyzed and compared to patients with Alzheimer´s disease, but without implants.

 

The team recently published their results in the journal Alzheimer´s and Dementia

Leave a comment

Filed under Cognition

Key gene specific to the human brain discovered

by Tanja Jensen

https://www.flickr.com/photos/99843102@N05/14025817193/in/photolist-9FGf8L-nmFCVu-nmY4ER-nkmZoh-667tcX-njNjk5-6tV9nc-7JMe3g-6H5EcX-nX2Ru-nnpYNn-nnpZe2-nkDnjH-6tVcdz-nkFFSj-7GUzKk-6aV2Yg-6aV2Yn-66bB5U-p7zXLe-bgKpqv-6tVgnr-bxfMk5-upyV-qZoinN-btFUt5-jT7XZZ-eEDp1o-fJ82LS-eEDpoU-eEDpzC-eExi5i-eEDpmG-eEDpfq-eExhvD-7pkwgA-7umgaQ-feHhNJ-fet1WV-feHhem-fet1DK-feHhtE-eEDoNq-eExhKF-eEDp5S-eEDoBQ-8kPC6d-nxiPCx-ng4yag-nghmEr

Image credit Mehmet Pinarci/Flickr

A gene that sets apart the human brain from other brains has been discovered by German scientists. The scientists wondered what causes our human brain to be the largest and most complex among primates.

Marta Florio, and her colleagues at the Dresden laboratory studied 56 genes lacking a corresponding lineage in mice. They discovered that one particular gene boosts the number of brain stem cells.

The stem cells make neurons in the neocortex, a region for long term memories, language, and conscious thoughts. Instead of maturing and dividing into two neurons, the gene caused the cells to multiply and divide into many neurons, leading to the human brain´s unique mental capacity.

The gene can have pivotal impact on mouse brain development. Mice embryo injected with the gene grew larger brains and sometimes also folded, like the human brain.

Now the researcher have to wait, to tell whether the injection boosts adult mice intelligence, memory and learning skills.

 

The reference is from the journal Science.

Leave a comment

Filed under Cognition