Less brain - more brain

More grey matter is good. Right? Wrong. Loss of connections between the neurons is bad. Right? Wrong. Your brain is, quite literally, smarter than you think! Sometimes what may look like negative changes to you, turns out to be an adaptive way of optimising brain`s functioning so you can get most out of it!

Garden patch in your head

A baby is born with up to 100 billion neurons that make up the brain, or grey matter. When you stimulate baby`s brain with "pick-a-boos", out-of-tune lullabies and daily dose of  Nick Junior, neurons branch out extensively, growing new dendrites (branches) and forming connections with other neurons. Neuroscientists, possibly because of limited imagination and suppressed attraction to gardening, call neuronal branches dendritic trees  and a period of their maximal growth blooming. Here is what might a highly branched out neuron look like:
 

At a certain time, of course, your little one discovers that Nick Junior is not as much fun as the Babe Station. So the dendrites responsible for connections in the Nick Junior neural circuit are no longer of any use and they get simply eliminated, this is termed....get your gardening clogs on....  dendritic pruning!

Pruning of useless dendrites is one cause of the absolutely normal grey matter loss. On to the second.

When grey becomes white...

If Nick Junior only requires passive watching while munching on fish fingers, with the Babe Station you need to think fast and act appropriately. And before you think of anything rude, I only mean being able to turn it off as soon as  mum walks into the room. So, the older we are, the faster our brains become, and all because clever mother-nature designed special insulation for neuronal axons called myelin to speed up signal transmission.

Myelination continues well into the third decade of life, and white matter is nothing more than myelinated nerve fibres. Increased volume of the white matter logically means decrease in the grey matter, again, perfectly normal. In fact, patients with certain conditions like attention-deficit hyperactivity disorder (ADHD) or fetal alcohol syndrome (FAS) display abnormally large volume of grey matter due to insufficient myelination.

Less is more 

So, the good news is, not all grey matter loss is bad!  Synaptic pruning and myelination have evolved to make your Babe Station experience as efficient as possible!

Thanks for reading!

References for the curious:

Sowell, E. R. (2007)  Computational neuroanatomy presentation for UCLA Advanced Neuroimaging course (podcast)

Toga, A.W., Thompson, P.M. and Sowell, E.R. (2006) Mapping brain maturation, Trends in Neuroscience, 29 (3), 148-159

How low can you go?

Do not read any further if you are squeamish. There will be a lot of blood and detailed descriptions of gruesome neurosurgery.

Ok, now everybody is paying full attention.... How low can you go? We all get low, some of us get depressed, some will get treatment as drugs or psychotherapy, some will get better but a small minority will not respond to any intervention, no matter how many dozens of pills they take or how many hours of counselling they receive. It is known as treatment-resistant depression (TRD). So scientists figured out that the next logical step would be to open up the brain and fix it from the inside!

                                                           Shut down, restart

Brain cells communicate using electro-chemical signals. By implanting electrodes into the brain and sending electrical impulses it is possible to interfere with the functioning of the neuro-circuits that control everything from movements to feelings and thoughts. This is known as Deep Brain Stimulation (DBS). It works by temporarily disrupting electrical activity in the brain regions in order to normalise their functioning. Think about reloading your computer when it freezes in the middle of you preparing the most important report in your career.

I am depressed, get me out of here!

What does DBS have to do with severe depression? Researchers have established that depressed patients display abnormal activity in certain brain regions. In the picture below, red box is the area of TOO MUCH activity (ventral pathway) and blue box is the area of TOO LITTLE activity  (dorsal pathway) (Maybergh, 1997)

It turns out that these areas operate in a mutually-dependent manner - increase of activity in one region leads to decrease of activity in another. So, here is a clever thing, finally. To fight your depression, neurosurgeons would attach electrodes to the red area marked Cg25 in the overactive region through which electrical impulses will be delivered. And then...

The Panto

Electric impulse (to the red guys):
- C`mon dudes, you are working overtime here, slow down!
Red guys (some of them):
- Hurray! Annual leave! All expenses paid! But wait, someone has to work! (Shouting to the blue guys) Hey, you lot up there, work for ya money!
Blue guys stretch and yawn, put work suits on and line up in the kitchen for their morning SpecialK and Tropicana.   .

Work resumes in the blue department and slows down in the red department. Everybody happy.

Depression:
- Oh, for God`s sake.... (Leaves, slamming the door)

Applause

Treatment of severe depression using DBS is a new  but very promising approach. Now you know about it too!

Thanks for reading!

References for the curious

Kuhn, J., Grundler, T.O, Lenartz, D., Sturm, V., Klosterkotter, J, Huff, W. (2010) Deep brain stimulation for psychiatric disorders, Deutsches Ärzteblatt International, 107 (7): 105-13

Langevin, J.P (2012), Neuromodulation of the limbic system, Neurology Grand Rounds Lecture Series (podcast), University of Arizona

Lozano, A., Mayberg, H.S., Giacobbe, P., Hamani, C., Craddock, R.C., Kennedy, S.H. (2008)Subcallosal Cingulate Gyrus Deep Brain Stimulation for Treatment-Resistant Depression, Bilological Psychiatry, 64 (6): 461-467

Maybergh, H.S (1997) Limbic-cortical disregulation: a proposed model of depression, The Journal of Neuropsychiatry and Clinical Neuroscience, 9: 471–81

And finally...Watch this TED talk if you want to learn more about DBS:

http://www.youtube.com/watch?feature=player_embedded&v=7udZ5ux0dYE

 

 

How to spot a cheater

Wouldn`t you just love to know that your partner will never cheat on you? Or, for that matter, that you will never give into temptation to cheat on your partner? Despite being most sincere in their "I do`s" some people find it easier to  settle down with one partner for life, than others... Psychologists, being a very curious type of folk, of course, couldn't have left this topic uninvestigated and here`s what they found... 

Love rats 

Well, actually, not rats but voles. The story goes, that far away in Northern American there live two species of voles - Montane vole and Prairie vole. Both spend their days making burrows and happily muching on plants and seeds. But their family values couldn`t be more different! While Montate voles are incredibly promiscuous, Prairie voles are known to make a pair bond for life, sharing a nest and raising babies together "until the death does them apart".

With very similar lifestyles, this difference could have only been attributed to "something in the brain". Indeed, it turned out, that monogamous and polygamous voles have different patterns of distribution of oxytocine (OT) and vasopressine (VP) receptors in the brain - neurotransmitters known to be invloved in sexual behaviour, parental care, aggression and territory making. As one example, monogamous voles have overexpression of oxytocin receptors in nucleus accumbens, thought to be important for processing pleasure and reward, meaning that monogamous voles get a real buzz from living with the same partner!

In one particular fun experiment, female prairie voles have been injected with the -antagonist after mating and displayed no affection to the hearbroken male (sweet revenge....:-)))

Calculated love

 

Now for some fun scientific speculation! Fast-forward 100 years from now and we might see match-making services offering to scan of your potential partner`s brain to assess how likely he/she is to stay faithful. And chemists, along with morning-after pills, might start offering anti-heart-break injections! I am in... :)

 Thanks for reading!

 

 

References for the curious:


Insel, T (2010) The challenge of translation in social neuroscience: a review of oxytocin, vasopressin, and affiliative behaviour, in Neuron, 65 (768-779)

Liu, Y and Wang, Z.X. (2003) Nucleus accumbens oxytocin and dopamin interact to regulate pair bond formation in female prairie voles, in Neuroscience, 121 (537-554)


Wang, Z. and Aragona, B.G. (2004) Neurochemical regulation of pair bonding in male prairie voles, in Physiology & Behaviour 83 (319-328)

Meet your homunculus

What can you say about your brain? You would probably describe it as a main organ of the nervous system,  a control centre for all mental processes, a 3lb  mass of grey and white matter with wrinkled surface etc...

 

Now imagine for a moment that you asked your brain to do just opposite - to describe YOU. If you are hoping to hear something like "A sexy brown-eyed male with a great karaoke talent", think again. In your brain's view, you are quite an ugly creature with oversized tongue and lips and massive dangling hands. Meet your HOMUNCULUS.

Homunculus ("little man" in Latin) is, of course, not a creature living inside your head, but a way your body is "mapped" onto the surface of your brain. Huge tongue and small feet simply means that more of the cortical tissue is allocated to "service" your tongue than feet.

Two in one

In reality, there are two homunculi - a sensory one and a motor one (see the pic below). Corresponding brain areas are called somato-sensory cortex (in blue, this part receives sensations from your body parts) and motor cortex (in red, this part sends out movement commands to the body parts).

Many body areas are mapped to a similar scale in both cortices. For instance, both cortices have large representation of hands. This is, of course, because skin of our hands, in particular palms and fingers, has high density of touch receptors, and, at the same time, hands have large number of skeletal muscles, controlled by the motor cortex, enabling us to execute very fine movements like playing piano.

In other ways, the body maps differ. Motor homunculus, for example, is missing several areas, like intestines, back of the head or genitals. The reason for this being, although you can feel the pain in your intestines or pleasurable touch to your genitals, you cannot consciously command to these parts to move (imagine how much more entertaining your life would be if you could)...

 Never alone

So here is a comforting thought. Whenever you feel lonely - think of your homunculus who is always around, feeling what you are feeling and doing what you are doing, but who is nowhere near as good looking as you are!

Thanks for reading!