Hjärnan glömmer för att spara energi

Publicerad: 2015-10-27

Våra hjärnor har inte bara inlärningsmekanismer utan också glömskemekanismer som suddar ut ”onödig” inlärning. En forskargrupp vid Lunds universitet har nu kunnat beskriva en av dessa mekanismer på cellnivå.

Gruppens resultat, som publicerats i den internationella tidskriften PNAS (Proceedings of the National Academy of Sciences), förklarar ett inlärningsteoretiskt fenomen som hittills varit svårbegripligt.

Utgångspunkten är att en försöksperson eller ett försöksdjur kan lära sig att förknippa en viss ton eller en viss ljussignal med en luftpuff mot ögat. Luftpuffen får människan eller djuret att blinka, och så småningom blinkar hon så fort hon hör tonen eller ser ljussignalen. Det märkliga är dock att om tonen och ljuset sedan presenteras samtidigt, så blir inlärningen inte bättre utan sämre.

- Två stimuli ger alltså sämre resultat än bara en – det verkar ju som en paradox som strider mot sunt förnuft. Men vi tror att orsaken är att hjärnan vill spara på energi, säger hjärnforskaren professor Germund Hesslow.

Hans medarbetare Anders Rasmussen, som också deltar i den aktuella studien, har tidigare visat att när hjärnan lärt sig en viss association tillräckligt bra, så aktiveras vissa nervceller som stänger av inlärningen.

- Man kan säga att den delen av hjärnan som lärt sig associationen säger till sin "lärare" att "nu kan jag det här, håll tyst". När hjärnan har lärt sig två associationer blir denna avstängningsmekanism mycket starkare. Det är därför resultatet blir en glömska, som dock oftast är tillfällig, förklarar Germund Hesslow.

Att upprätthålla onödiga associationsbanor kostar energi för hjärnan. Det är skälet till att avstängningsmekanismen uppstått, menar forskarna – även om den i det här fallet råkat bli lite för stark.

Lundagruppen har kunnat beskriva nervcellernas arbete med inlärning och glömska i djurförsök, men menar att mekanismerna lär vara desamma i den mänskliga hjärnan. Fynden har därför ett principiellt intresse både för hjärnforskare och psykologer. De skulle också kunna ha ett praktiskt intresse för pedagoger.

- Det bör ju vara viktigt för alla som undervisar att känna till de mekanismer där hjärnan suddar ut sådant den inte anser sig behöva. Man vill ju inte av misstag aktivera dessa mekanismer, menar Germund Hesslow.

Ingela Björck

Danska Rigspolitiet har höjt bered-   
  skapen i landet. Det borde även Sverige göra om man vaknar.

Danmark-Zlatan 2-2 i kväll och Sverige till EM-slutspel. Välkommen ljuspunkt; ja nödvändig sådan.

BRA!

Regeringen beslutade i dag att införa 
  krav på legitimation på färjorna till 
  Sverige. Det innebär att den som      
  kommer som flykting till Sverige      
  söderifrån och saknar papper bara kan 
  ta sig in via Öresundsbron.

Kvalmatch: Danmark-Sverige

Sverige vann lördagens match i Solna med 2–1, det ger följande förutsättningar inför tisdagskvällens returmatch på Parken i Köpenhamn.

Sverige går till EM:
...vid seger eller oavgjort.

...vid uddamålsförlust med 2–3, 3–4 och så vidare.

Danmark går till EM:

...vid uddamålsseger med 1–0.

...vid seger med minst två måls marginal.

Om Danmark vinner med 2–1 väntar förlängning i 2x15 minuter. Om förlängningen slutar mållös vidtar straffläggning. Gör båda lagen mål i förlängningen gör det lag som gjort flest vidare till EM. Gör båda lagen lika många mål i förlängningen går Sverige till EM på grund av den regel som säger att mål på bortaplan är mer värt.

TV5 (matchstart kl 20:45)

Frankrike skickar hangarfartyget Charles de Gaulle mot Syrien

Charles de Gaulle är den franska flottans enda hangarfartyg och är flottans flaggskepp. Längd 262 m, Byggd 1989, Sjösattes 1984.

Usch - minst sagt

Solens upp- och nedgång den 16 november 2015 (Stockholm): 07.48/15:17.
Lägg till Paris och svensk invandringspolitik.

Only three local stars appear in this image, quartered by right-angled diffraction spikes. Everything besides them is a galaxy; floating like a swarm of microbes in a drop of water, and brought into view here not by a microscope, but by the Advanced Camera for Surveys on the Hubble Space Telescope.

In the foreground, the spiral arms of MCG+01-02-015 seem to wrap around one another, cocooning the galaxy. The scene suggests an abundance of galactic companionship for MCG+01-02-015, but this is a cruel trick of perspective. Instead, MCG+01-02-015’s unsentimental naming befits its position within the cosmos: it is a void galaxy, the loneliest of galaxies.

The vast majority of galaxies are strung out along galaxy filaments — thread-like formations that make up the large-scale structure of the universe — drawn together by the influence of gravity into sinuous threads weaving through space. Between these filaments stretch shallow but immense voids; the universe’s wastelands, where, outside of the extremely rare presence of a galaxy, there is very little matter — about one atom per cubic meter. One such desolate stretch of space is what MCG+01-02-015 reluctantly calls home.

The galaxy is so isolated that if our galaxy, the Milky Way, were to be situated in the same way, we would not even have known of the existence of other galaxies until the development of strong telescopes and detectors in the 1960s.

Image credit: ESA/Hubble & NASA and N. Grogin (STScI), Acknowledgement: Judy Schmidt
Text credit: European Space Agency

Last Updated: Nov. 16, 2015

Editor: Ashley Morrow

De behöver också hjälp. Eller...?

--> Mer än bara tak över huvudet

Had a transparent and dynamic public discussion been taking place in Sweden during the past months — a discussion that acknowledged both the need for human solidarity and the limitations of the country’s infrastructure — a more sustainable immigration policy might have emerged. Instead, it seems ill-fated policies will not be altered until the country brings itself to the brink of collapse.

--> Veiny 'Garden City' Site and Surroundings on Mount Sharp, Mars

Nu är kriget i full gång

                       

                 Franskt flyg(Rafael et Mirage) i bombräd         
         mot IS-fästen i Syrien 

      Sorry for the people

Salah Abdeslam är efterlyst för dåden i Paris

Apropå Paris

Galenskaper hela tiden på vår stackars rymdspillra. Vad gör man?

Languages Are Products of Their Environments - D-brief

--> Languages Are Products of Their Environments - D-brief

Taken by Marketa S Murray on November 11, 2015 @ Fairbanks - Alaska

Ingen kan förvånas över att SD nu toppar "ligan".

Enligt Migrationsverket kan de nya gränskontrollerna till och med innebära att fler kommer att söka asyl i Sverige

Greenland Is Melting Away (N Y Times)

www.nytimes.com/interactive/2015/10/27/world/greenland-is-melting-away.html?ref=world&_r=0

Ekvationens lösning

Jag såg en rubrik i tidningen häromdagen: "SCB: Befolkningen ökar kraftigt". 

Oj då, det hade vi ingen aning om.

Oavsett resultatet med gränskontroller: regeringen har i alla fall erkännt landets (under åratal) galna invandringspolitik. Alltid något!

Från Avpixlat

Around the world, 1.3 billion people lack access to electricity. More than 600 million are in sub-Saharan Africa, and more than 300 million are in India alone. Providing electric power to these unserved populations will cause a significant jump in demand in the coming decades. India has promised to place an emphasis on renewable sources of energy; there are programs in Africa to create “mini-grids” using renewables. But as electricity-generating capacity inevitably grows ever larger, India and the other countries of the developing world will not be able to avoid the increased use of fossil fuels as well — and especially coal. New coal-burning power plants will emit less carbon dioxide and other greenhouse gases than their predecessors, but the strain on the atmosphere will be substantial nonetheless. Read the related story.

LINICAL DECISIONS

Blood-Pressure Control

November 9, 2015DOI: 10.1056/NEJMclde1513565

 Comments open through November 16, 2015

 Poll open through December 2, 2015

Article

References

CASE VIGNETTE

A Woman with Hypertension

James S. Yeh, M.D., M.P.H.

Ms. Weymouth is a 75-year-old woman who presents to your geriatric clinic for routine follow-up. She mentions that she heard a report about blood-pressure control on the news recently that included something about “lower might be better.” She wonders to what level her blood pressure is controlled and whether her blood-pressure medications need to be adjusted today.

Her medical history is significant for hypertension, atrial fibrillation, peripheral arterial disease with mild intermittent claudication, and cataract. Her current treatments include 100 mg of metoprolol succinate daily, 5 mg of apixaban twice a day, 25 mg of chlorthalidone daily, 81 mg of aspirin daily, and 10 mg of atorvastatin daily. She does not have any known drug allergies. She had a left-wrist fracture 6 years ago when she slipped and fell on an icy sidewalk.

She lives at home with her husband, to whom she has been married for 55 years. They have 4 children and 14 grandchildren, all of whom live nearby. She has never smoked, and she drinks 1 to 2 glasses of red wine a week. She and her husband walk regularly for exercise, as you have recommended to reduce the incidence of claudication. She had worked in a bakery before her retirement 10 years ago. She enjoys gardening and other yard work and spending time with friends. A review of her systems is unremarkable.

On physical examination, she looks well. Her weight is 156 lb (71 kg), and her height is 5 ft 4 in. (163 cm); her body-mass index (the weight in kilograms divided by the square of the height in meters) is 26.8. Her heart rate is irregular at 70 to 72 beats per minute, and her blood pressure is 136/72 mm Hg. Her heart sounds are irregular and consistent with atrial fibrillation. There is no murmur. The rest of her physical examination is unremarkable.

Her most recent laboratory results revealed a total cholesterol level of 174 mg per deciliter (4.5 mmol per liter), a low-density lipoprotein cholesterol level of 87 mg per deciliter (2.2 mmol per liter), a high-density lipoprotein cholesterol level of 65 mg per deciliter (1.7 mmol per liter), a serum creatinine level of 0.9 mg per deciliter (80 μmol per liter), and an estimated glomerular filtration rate of 65 ml per minute per 1.73 m2 of body-surface area. An ankle–brachial index measured last year was 0.85 on the left and 0.95 on the right.

TREATMENT OPTIONS

After obtaining the history and performing the physical examination, what recommendation do you make to Ms. Weymouth about the management of her blood pressure?

1. Maintain the current antihypertensive regimen.

2. Modify the antihypertensive regimen to reduce the systolic blood pressure further.

To aid in your decision making, each of these approaches is defended in a short essay by an expert in the field. Given your knowledge of the patient and the points made by the experts, which option would you choose? Make your choice, vote, and offer your comments at NEJM.org.

• Treatment Option 1: Maintain the Current Antihypertensive Regimen
• Treatment Option 2: Modify the Antihypertensive Regimen to Reduce the Systolic Blood Pressure Further

Treatment Option 1 (0)

Treatment Option 2 (0)

TREATMENT OPTION 1

Maintain the Current Antihypertensive Regimen

George L. Bakris, M.D.

Ms. Weymouth's hypertension is adequately controlled. Given her history of falls, coupled with her exposure to anticoagulants, the potential harm of intensifying her antihypertensive regimen outweighs the benefit. Her calculated 10-year Framingham risk score is 7%. Apart from hypertension and peripheral arterial disease, the two other major factors associated with cardiovascular risk (i.e., lipid levels and blood pressure) are within the range associated with lower risk for people younger than 70 years of age. She is already receiving the most effective therapy to reduce cardiovascular risks.

Five randomized and six observational studies have evaluated the effects of blood-pressure control on cardiovascular outcomes in persons older than 65 years of age,1 with the mean age of participants in these trials ranging from 66 to 70 years. In the majority of these trials, the mean systolic blood pressure achieved was in the mid-140s. Hence, the 2013 Expert Panel Report recommended a blood-pressure goal of less than 150/90 mm Hg for persons over 60 years of age.2 However, according to data from National Health and Nutrition Examination Surveys (NHANES), the trends in blood-pressure control over the past 50 years, even with a blood-pressure target of 140/90 mm Hg, have been toward lower, not higher, blood pressures and lower cardiovascular event rates.3 Thus, in all other international guidelines regarding a blood-pressure goal in older people, the recommendation continues to be a goal of less than 140/90 mm Hg.1

The data from these trials have limitations, since there are few prospective outcome data from persons older than 75 years of age, with the exception of data from the Hypertension in the Very Elderly Trial.4 In that trial, in which the mean age of the patients was 84 years, patients in the active-treatment group, as compared with the placebo group, had a 64% reduction in the rate of heart failure and a 21% reduction in the rate of death from any cause. However, the achieved blood pressure was 144/78 mm Hg in the active-treatment group, as compared with 159/84 mm Hg in the placebo group.

The question remains whether the Systolic Blood Pressure Intervention Trial (SPRINT) provides new insights into how low this patient's blood pressure should be to further reduce her absolute risk of a cardiovascular event. In SPRINT, nearly 30% of the more than 9300 participants were 75 years of age or older.5 Participants who were assigned to a systolic blood-pressure goal of less than 120 mm Hg and were able to adhere to the medication regimen without unacceptable side effects had better outcomes than did those assigned to a goal of less than 140 mm Hg, which suggests the need for blood-pressure control tighter than that suggested by the results of previous trials. Although the results clearly showed a benefit with respect to all-cause mortality, the findings driving the cardiovascular benefit were a major reduction in the risk of heart failure and of sudden death rather than of coronary disease. A reduction in the risk of heart failure was also seen in all previous trials involving older people that assessed this outcome but at systolic pressures higher than those in the SPRINT trial.1

This patient's systolic blood pressure is higher than the 120 mm Hg systolic goal achieved in SPRINT, but given her history and coexisting conditions, attempts to reduce the current value to achieve a possible benefit would result in more complications if the more intensive regimen led to unacceptable side effects — all for a small reduction in absolute risk. In the SPRINT trial, the risks of serious adverse events of hypotension and syncope were 67% and 33% higher, respectively, with the lower blood-pressure target than with the higher target. Consequently, I would not be in favor of reducing her blood pressure further. I would recommend reassuring her and initiating a discussion with her about the benefit versus the harm of further blood-pressure reduction.

Disclosure forms provided by the author are available with the full text of this article at NEJM.org.

SOURCE INFORMATION

From the Department of Medicine, American Society of Hypertension Comprehensive Hypertension Center, University of Chicago Medicine, Chicago, IL.

Presidentval nästa år

Presidentval i USA om ett år. Hur det kan komma sig att det är ett val som alltid har intresserad mig vet jag inte.
Först s.k. primärval i februari då delegater ska nomineras. I Iowa hålls det första valet och den 14 juni det sista i Washington D.C (presidentkandidaterna nomineras på partikonventen). På partikonventet därefter ska den utsedde presidentkandidaten välja en vice president kandidat.  Både republikanerna och demokraterna håller sina konvent i Juli: republikanerna i Cleveland (Ohio) och demokraterna i Philadelphia (Pen.). Sedan  är et dags för de olika staternas utsedda delegater att rösta på favoritkandidaten. Den som får de flesta rösterna blir resp partis presidentkandiat. Presidentvalet hålls den 8e november. Man röstar fram elektorer och varje stat har ett antal elektorer beroende på sin folkmängd.  Elektorsystemet kan medföra att en president blir val trots att hen inte fått en majoritet av rösterna (minns farbror Georg W Bush år 2000).


Favoriter/demokraterna:
Bernie Sanders (bilden -74 år) och Hilary Clinton

Favoriter/republikanerna:
Ben Carson (bilden t.v. - 64 år), Donald Trump, Carly Florina, Jeb Bush och Marco Rubio.

Carly Florina (61 år)



  Donald Trump

Wikipedia om valet (rekommenderas); www.sv.wikipedia.org/wiki/Presidentvalet_i_USA_2016

PS

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Million-Dollar Donors in the 2016 Presidential Race /N Y Times