Candide

catholic by birth; scientist by choice; sinner by merit. gaidhlig-speaking neuroscience student at oxford. likes to question everything! @di_macd

So I spent today playing with human brains. The first time you hold someone’s loves, hopes and fears between your hands is really quite a numinous moment. It is just amazing to reflect that a person’s entire memory, their desires and hates, their quirks and oddities, are all written as a pattern of neural connections onto that orange-sized chunk of porridgy stuff. It makes me remember why I’m here, that in spite of how heavy and difficult the work load is, I really am in the privileged position of learning how our biology, our brains, our behavior, really works.

Just thought I’d like to share…

Brain clocks. Just add sunlight.

deoxyribolove:

Batteries power the clock in your living room. Sunlight powers the one in your brain—or at least keeps it accurate. That jet lag you feel when you step off a plane after an epic trip is caused by a brain clock, or circadian rhythm, out of sync with the world. Therefore, the best thing you can do after such a trip? Is go out into the sunlight, and stay in it long enough for the sun and the brain clock to synchronize.   

Sunlight is absorbed by special cells in the eye called intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells do not need the rods and cones in the eye responsible for vision. Instead, they contain the pigment melanopsin that absorbs the sunlight directly. The ipRGCs then project to the superchiasmatic nucleus (SCN), which contains the “clock cells.” Levels of PER and CRY proteins in these cells increase and decrease on a regular time schedule, marking the 24 hours of the day (more or less), and tell the brain what time it is. [If you want more detail on that, let me know. It’s pretty amazing].

At least, that’s the classic model. 

But what’s this? New research is saying that we don’t need the ipRGCs for our circadian rhythms either. The rods and cones of the retina can do a fine job setting the brain clock without these special melanopsin-containing cells. Surprisingly, The retina seems to have a rhythm of its own! In fact, if you take a retina, put it in a petri dish, and then sync it to light, you can sync the clock of SCN cells by just plopping them into the same petri dish! No projections necessary!

Somehow, the retina is sending out signals that can synchronize the SCN. What it is sending out? Hormones? Neurotransmitters? Magic powers? No one knows. 

For now, though, it might be best to just keep syncing with sunlight. >_<

rayax:

One of the many things that fascinate me about neurological disorders and syndromes is how much they convey to us about the nature of reality, the complexity of consciousness and the ease at which our free will can be taken away from us without our realization. 
One such neurological disorder, known as Alien hand syndrome, involves having full sensation of one hand without being able to control its movements. The patient afflicted is led to believe that he or she does not have any ownership over the limb. 
AHS is usually a result of an impairment to the brain such as head trauma, stroke, tumor or infection. Depending on the cause of the injury, the movements of the hand may be random or purposeful. For instance, when the disorder is brought about as a result of brain tumor, aneurysm, or a stroke, the hand may be involved in complex purposeful behaviors such as undoing buttons, using tools or tearing clothes. In most cases, the owner of the hand is completely oblivious of what the hand is doing until it has been brought to his or her attention, or until they happen to see it for themselves. Interestingly, it is as if the the hand and the rest of the body both have separate brains of their own, where in fact they are still controlled by one organ. 
At the moment, there is currently no treatment or cure for alien hand syndrome, but the symptoms can often be reduced by keeping the afflicted hand preoccupied with an object. 

Magnetic stimulation in the lab can cause unsconscious movements and jerks of the hand. The subject is unaware of what the hand is up to. That is, the motor neurons are stimulated from outside rather than from a source within the volitional centres of the brain. I wonder whether alien hand has anything to do with this. i.e. the lesions etc break the motor pathway so movement of the hand is induced by electrical signals coming from elsewhere&#8230;
On the other hand, it could be a problem to do with feedback. We know that supposedly conscious actions are induced miliseconds before &#8216;we&#8217; are aware we want to do them. Maybe then the illusion conscious control depends on awareness of the unconscious pathway, and that it is this that is disrupted in alien hand.
This all just uninformed speculation though so don&#8217;t take it too seriously. I can&#8217;t wait til I can finally have the oportunity to test these ideas. 

rayax:

One of the many things that fascinate me about neurological disorders and syndromes is how much they convey to us about the nature of reality, the complexity of consciousness and the ease at which our free will can be taken away from us without our realization. 

One such neurological disorder, known as Alien hand syndrome, involves having full sensation of one hand without being able to control its movements. The patient afflicted is led to believe that he or she does not have any ownership over the limb. 

AHS is usually a result of an impairment to the brain such as head trauma, stroke, tumor or infection. Depending on the cause of the injury, the movements of the hand may be random or purposeful. For instance, when the disorder is brought about as a result of brain tumor, aneurysm, or a stroke, the hand may be involved in complex purposeful behaviors such as undoing buttons, using tools or tearing clothes. In most cases, the owner of the hand is completely oblivious of what the hand is doing until it has been brought to his or her attention, or until they happen to see it for themselves. Interestingly, it is as if the the hand and the rest of the body both have separate brains of their own, where in fact they are still controlled by one organ. 

At the moment, there is currently no treatment or cure for alien hand syndrome, but the symptoms can often be reduced by keeping the afflicted hand preoccupied with an object. 

Magnetic stimulation in the lab can cause unsconscious movements and jerks of the hand. The subject is unaware of what the hand is up to. That is, the motor neurons are stimulated from outside rather than from a source within the volitional centres of the brain. I wonder whether alien hand has anything to do with this. i.e. the lesions etc break the motor pathway so movement of the hand is induced by electrical signals coming from elsewhere…

On the other hand, it could be a problem to do with feedback. We know that supposedly conscious actions are induced miliseconds before ‘we’ are aware we want to do them. Maybe then the illusion conscious control depends on awareness of the unconscious pathway, and that it is this that is disrupted in alien hand.

This all just uninformed speculation though so don’t take it too seriously. I can’t wait til I can finally have the oportunity to test these ideas. 

(via lookingforether)