Category Archives: Brain

Sleep in preindustrial societies

Brain, Cell physiology

There are complaints that sleep in industrial communities (with electric light, noise all over) is severely compromised. These complaints have already been raised about 150 years ago, at the beginning of the industrialization. Sleep before is supposed to be calmer and longer.

This seems not to be true. Measuring the sleep durations and sleep onset and wakening in three societies that have no electric light, that remain in a pre-industrial state even in the 21st century, Yetish and colleagues report in Current Biology that sleep duration are the same as in industrial settings. Measurements were done in the last corner of Bolivia, in the Tsimane community, in Central Africa with the Ju/’hoansi San people, and in northern Tanzania with the Hadza.

There is an News and Views article on the same issue in Nature. Both articles are highly recommended.

Puberty – new evidence for its regulation

Brain, Cell physiology, Endocrinology, GnRH

It has been a long standing mystery how the start of puberty is initiated. Fact is that menarche, the begin of active reproduction capacity is preceded by and a consequence of the adrenarche, the begin of androgen production in the adrenal gland. Puberty is characterized by the beginning of sporadic gonadotropin releasing hormone (GnRH) pulses which in time become regular and finally acquire their one-in-two hour rhythm at the end of puberty.

A report in the Journal of Molecular Endocrinology by Abreu and colleagues from Boston and Sao Paulo has uncovered  that the Makorin ring finger 3 (MKRN3) gene is mutated in cases of central precocious puberty (CPP) . CPP is diagnosed when the children enter into puberty much to early for their age. They analyzed the protein in more detail then and found the decline of MKRN3 expression in the arcuate nucleus (area of the hypothalamus to control GnRH secretion) is necessary for the increase of GnRH secretion. Without GnRH puberty can not take place. By which stimulus the decline of MKRN3 is initiated has not been described. It is discussed whether MKRN3 acts directly on GnRH secretion or on kisspeptin, neuromedin B or dynorphin, known mediators of GnRH secretion. It can not act on GnRH expression since the GnRH neurons only reach with their axons into the arcuate nucleus where their release is controlled by other neurons and mediators.

This is a nice paper, adding valuable information to people concerned with the mechanisms of puberty. Recommended!

Prediction of the prey’s path by dragonflies

Brain, Circuits, Evolution

Hunting a moving target involves reaction to the prey’s movement, so you would think. It involves, however, in vertebrates also a model how the prey may move, to be able to predict the possible flight routes. This model was thought to be lacking in invertebrates.

In a paper in Nature Mischiati and colleagues describe that dragonflies have this internal model, too. They show that vision is to react to the prey’s escape but underlying the dragonfly’s steering is brain model how the prey might fly. You have to keep in mind that dragonflies hunt in 3D and not in 2D as tetrapods do. We are proud that comet lander does find and land on the target some 100000 miles away, and use immense computer power for this task. Dragonflies have it all in their tiny heads.

The paper uses fly models in the lab as prey. It will be some time before it will be possible to test the facts on free flying dragonfly. But it is a nice piece of information already.

Recommended

Gray matters in grass research

Brain, Cell physiology, THC

Whether long-term marijuana smoking has robust effects for the human brain has been a matter of debate. In a paper in PNAS Silbey and colleagus from Dallas, Frisco, and Albuquerque have addressed this question using “multimodal measures in a large group of chronic marijuana” smokers. They claim that marijuna smokers the longer the more have decreasing gray matter in orbitofrotal cortex (OFC).

This part of the brain (citation from wikipedia:)

is considered anatomically synonymous with the ventromedial prefrontal cortex.[2] Therefore the region is distinguished due to the distinct neural connections and the distinct functions it performs.[3] It is defined as the part of the prefrontal cortex that receives projections from the magnocellular, medial nucleus of the mediodorsal thalamus, and is thought to represent emotion and reward in decision making.[4] It gets its name from its position immediately above the orbits in which the eyes are located. Considerable individual variability has been found in the OFC of both humans and non-human primates.

The authors are very cautious to attribute these changes to THC. They also found increased connectivity within the OFC and suggest that the OFC gray matter is more vulnerable to the THC effects.

Recommended!

 

Oxytocin for pairing — in mice

Brain, Circuits, Endocrinology, G-protein Coupled Receptors, Hormones, Oxytocin

Oxytoxin is the hormone of social interactions, the mechanism of the interaction mostly unknown. Therefore, it is a nice surprise that Nakajima, Görlich, and Heintz from the Rockefeller Univ. in New York report in Cell on a newly identified subset of somatostatin interneurons from the prefrontal cortex of mice which bear the oxytocin receptor.

They silenced then this receptor in some mice. The females in these silenced mice with the  oxytocin receptor inactive lacked the social interactions with male mice only during the estrus phase, when copulation would ensure progeny. The interactions with female mice were normal. In the diestrus phase interactions with males  were not disturbed.

Similarily they could produce mice where the oxytocin gene was removed in the prefrontal cortex. The female mice showed the same deficit. Even mice treated with an oxytocin antagonist blocking the action of oxytocin had the same effect on the social interactions of the females thus treated.

We do not know whether oxytoxin is acting here in an endocrine way via the blood or as a neurotransmitter via synapses. It is not to far fetched to think oxytocin stimulating these interneurons is required – in mice – for social interactions leading to progeny although it is not in the paper.

A nice bit of information!

The map in your brain

Brain,

How can we know where we are? This question has for centuries  pestered philosophs. In the area of GPS this now is no longer even a practical question, anyone with a smartphone can easily determine her/his position in space with unprecedented certitude. 

However, what is technically possible, does not bear on the perception of space in the human mind. Agreed, that this would pose problem came not even to my mind. Therefore, the announcement of the Nobelprice to the three researchers John O’ Keefe (USA) and the couple May-Britt and Edvard Moser (Norway) comes as a surprise. But it shows that there was a question and already the solution these three researchers provided. I cite from the press release of Nobel Assembly at the Carolinka Institute (Nobelprizse.org):

The discoveries of John O´Keefe, May-Britt Moser and Edvard Moser have solved a problem that has occupied philosophers and scientists for centuries – how does the brain create a map of the space surrounding us and how can we navigate our way through a complex environment?

Continue reading The map in your brain →

GABA receptor structure revealed

Biochemistry, Brain, Cell physiology, Neurotransmitters

GABA (gamma-amino butyric acid) receptors belong to the group of pentameric ligand-gated ion channels as serotonin receptors or acetylcholin receptors. Since these membrane proteins have been impossible to chrystallize for a long time and there are still difficulties to determine their structure by X-ray spectometry. However, in recent years it became fashionable to analyze membrane receptors of different types, the determination of the GABA receptor is not a great surprise.

In this week Nature (doi:10.1038/nature13293) Miller and Aricescu from Oxford, UK, show the structure of the so-called β3-homopentamer. BTW that only two authors succeded in this task comes as a surprise.

The GABA receptor is involved in a number of diseases: epilepsy, insomnia, anxiety and panic disorders, has a role in alcohol abuse, binds to benzodiapines. Miller and Aricescu have chrystallized the receptor with a so far unkown agonist (a molecule to activate): benzamidine which allows predictions about the way ligands are bound and how they function.

The paper shows a abundance of beautiful  structural graphs which were drawn with Pymol a nice program used by myself in Hormone und Hormonsystem.

Seasonal Regulation of Endocrine Functions.

Biochemistry, Brain, Cell physiology, Endocrinology, Evolution, Hormones,

Almost any animal regulates its metabolism as well as its reproductive life according to the time of the year. (The fact that some domestic animals do not is the exception). This dependence on the season has long been a mystery for endocrinologists. Even then it was found that the Nucleus suprachiasmaticus in the hypothalamus controls and generates a circadian (daily) rhythm which is reflected in all animals analyzed the circannual (yearly) rhythm remained obcur.

Recent developments have shown that some pituitary cells in Pars tuberalis (PT; close to the pituitary stalk) measure the length of day via the melatonin they receive. Since melatonin is only produced in the dark, much melatonin means long nights and few melatonin means short nights. These cells therefore have been named calendar cells.

In an Open Access review in the Journal of Endocrinology Shona Wood and Andrew Loudon have summarized what is known about the physiology and biochemistry of this circannual regulation. They show that thyriod hormones and their conversion from thyroxine to triiodothyronine by deiodinase are an important part in the short day response. They analyse the melatonin response in the PT. They also show how clock genes are differential regulated during the seasons. Finally they show that a ancient gene, the eye absent protein 3 (EYA3) is specifically upregulated when the days get longer.

These genes are ancient and found in insects as well as in birds and mammals pointing to a very old mechanism.

Nice paper, worth studying!

 

Brain structures and hormones in parents when children are raised

Brain, Circuits, Hormones, Oxytocin

In a comment on a paper in the same issue of PNAS Sarina Saturn describes how Abraham et coworkers have analysed the complex relationship of neural activation, hormones and behaviour in first time parents comparing primary care /PC) mothers and secondary care (SC) fathers who are partners of mothers and primary care (PC) fathers who raise a child without a mother.

Abraham  et al. have identified characteristic features common to fathers and mothers and, not surprisingly, also features where mothers and fathers differ. An emotional network including  the amygdala (AMY),* ventral anterior cingulate cortex (vACC),* insula,* inferior frontal gyrus (IFG), and ventral tegmental area (VTA).* *Subcortical and paralimbic structures not located at the outer cortical surface was found as well as a mentalizing network which includes superior temporal sulcus (STS), frontopolar cortex (FPC), ventromedial prefrontal cortex (vmPFC), and temporal poles (TP).  Cites from PNAS:

PC-mothers displayed the greatest activation of the emotional system, and this activation significantly related to parent–infant synchrony and oxytocin levels. SC-fathers, in contrast, exhibited more activation of the cortical system. Fascinatingly, PC-fathers showed amygdala activation similar to PC-mothers and STS activation similar to SC-fathers, with pronounced functional connectivity between the two regions. This suggests that when a baby is raised by PC-fathers, both systems are used for optimal childrearing.

For both PC-fathers and SC-fathers, the STS–amygdala overlap directly related to how much the men were involved in tending to the baby, and STS activation correlated with oxytocin levels and parent–infant synchrony. This provides evidence that exposure to the infants and caretaking activities can groom oxytocin and neural systems to carry out the degree of paternal involvement.

This is a first time that these interactions have been studied. Nicely done!