Dementia

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Study shows early cognitive problems among those who eventually get Alzheimer’s

People who study or treat Alzheimer’s disease and its earliest clinical stage, mild cognitive impairment (MCI), have focused attention on the obvious short-term memory problems. But a new study suggests that people on the road to Alzheimer’s may actually have problems early on in processing semantic or knowledge-based information, which could have much broader implications for how patients function in their lives.

Do people with MCI have trouble accessing different types of knowledge? Are there obvious semantic impairments that have not been picked up before? The answer was “yes.”

… “If you ask someone what is bigger, a key or an ant, they would be slower in their response than if you asked them what is bigger, a key or a house,” explained Dr. Goldberg. The greater the difference in size between two objects, the faster a person—normal or otherwise—can recognize the difference and react to the question.

…They found large differences between the healthy controls and the MCI and Alzheimer’s patients. “This finding suggested that semantic processing was corrupted.  MCI and AD (Alzheimer’s disease) patients are really affected when they are asked to respond to a task with small size differences.”

They then tweaked the task by showing pictures of a small ant and a big house or a big ant and a small house. This time, the MCI and AD patients did not have a problem with the first part of the test—they were able to choose the house over the ant when asked what was bigger. But if the images were incongruent – the big ant seemed just as big as the small house – they were confused, they answered incorrectly or took longer to arrive at a response.

Patients with MCI were functioning somewhere between the healthy people and those with AD. “When the decision was harder, their reaction time was slower,” he said.

Would this damaged semantic system have an effect on everyday functions? To answer this question, investigators turned to the UCSD Skills Performance Assessment scale, a tool that they have been using in MCI and AD patients that is generally used to identify functional deficits in patients with schizophrenia. The test taps a person’s ability to write a complex check or organize a trip to the zoo on a cold day.

This is actually a good test to figure out whether someone has problems with semantic knowledge. Semantic processing has its seat in the left temporal lobe. “The semantic system is organized in networks that reflect different types of relatedness or association…Semantic items and knowledge have been acquired remotely, often over many repetitions, and do not reflect recent learning.”

… “It tells us that something is slowing down the patient and it is not episodic memory but semantic memory,” he said. They will continue to study these patients over time to see if these semantic problems get worse as the disease advances.

…. the “semantic memory deficit demonstrated by this study adds confidence to the growing perception that subtle decline in this cognitive domain occurs in patients with amnestic mild cognitive impairment.  Because the task places minimal demands on the effortful retrieval process, overt word retrieval, or language production, it also suggests that this deficit reflects an early and gradual loss of integrity of semantic knowledge.”

He added that a “second important aspect of this study is the demonstration that semantic memory decrements in patients with mild cognitive impairment may contribute to a decline in the ability to perform usual activities of daily living.”

Humans Evolved to Basically Walk and Do Endurance Work All the Time – Not Tweet

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We mustn’t forget that those individuals [early humans] were also hunter-gatherers. They worked extremely hard every day to get a living.

  • A typical hunter-gatherer has to walk between nine and 15 kilometers a day.
  • A typical female might walk 9 kilometers a day,
  • a typical male hunter-gatherer might walk 15 kilometers a day, and that’s every single day.
  • That’s day-in, day-out, there’s no weekend, there’s no retirement, and you do that for your whole life. It’s about the distance if you walk from Washington, DC to LA every year.

That’s how much walking hunter-gatherers did every single year. Continue reading

“…human brains are fairly typical primate brains; they just became unusually large. “

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….it turns out also that the idea that brains got large early on in human evolution is incorrect as well. We now know that:

  • humans and chimpanzees split maybe around six to seven million years ago
  • and the very earliest hominins, those are creatures that are more closely related to humans than to chimpanzees, had really small brains.
  • In fact, early Australopithecus, like Lucy, also had quite small brains. Even the early members of the genus Homo had small brains.
  • Some tools first started appearing around 2.6 million years ago, and those hominins have slightly larger brains than Australopithecus.

But if you actually factor out the effects of body size, what’s called their encephalization quotient (the ratio of brain size to body size for what you expect for a mammal of a body size versus what you actually got) it was actually not that much bigger than chimpanzees or early Australopiths. To put it into perspective:

  • an EQ of one means that your brain size is exactly the size of a brain you predict for your body size.
  • Chimpanzees have an EQ of 2.1
  • humans have an EQ of about f5.1.
  • Australopiths have EQ’s of about 2.5
  • the earliest members of the genus Homo have EQ’s of about 3.0 to 3.3.

Their brains are a little bit bigger than a chimpanzee’s, but not hugely so, and it wasn’t until long after the genus Homo evolved that brains actually started getting really, really large. So increases in brain size were not really an early event in human evolution, and in fact, they didn’t occur until after hunting and after the invention of hunting and gathering, and not even until cooking and various other technological inventions, which gave us the energy necessary to have really large brains.

Brains are very costly. Right now, just sitting here, my brain (even though I’m not doing much other than talking) is consuming about 20- 25 percent of my resting metabolic rate. That’s an enormous amount of energy, and to pay for that, I need to eat quite a lot of calories a day, maybe about 600 calories a day, which back in the Paleolithic was quite a difficult amount of energy to acquire. So having a brain of 1,400 cubic centimeters, about the size of my brain, is a fairly recent event and very costly.

http://edge.org/conversation/-brains-plus-brawn

“young people who were exposed to the most music, compared to those who listened to music the least, were 8.3 times more likely to be depressed. However, compared to those with the least time exposed to books, those who read books the most were one-tenth as likely to be depressed. The other media exposures were not significantly associated with depression.”

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“In species where males fight for mates, bigger, heavier males have a better chance of winning fights, fending off their rivals and gaining access to females. After generations of male-male competition, the males of some species evolve to be much larger than their mates. “

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Birdsong and Music Stimulate Same Brain Parts

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Two studies on audio signaling thru birdsong songs and mating states:Birdsong study pecks theory that music is uniquely human

(Medical Xpress)—A bird listening to birdsong may experience some of the same emotions as a human listening to music, suggests a new study on white-throated sparrows, published in Frontiers of Evolutionary Neuroscience.

“We found that:

  • the same neural reward system is activated in female birds in the breeding state that are listening to male birdsong…For male birds listening to another male’s song, it was a different story: They had an amygdala response that looks similar to that of people when they hear discordant, unpleasant music.

The study, co-authored by Emory neuroscientist Donna Maney, is the first to compare neural responses of listeners in the long-standing debate over whether birdsong is music.

“Scientists since the time of Darwin have wondered whether birdsong and music may serve similar purposes, or have the same evolutionary precursors…But most attempts to compare the two have focused on the qualities of the sound themselves, such as melody and rhythm.”

“Birdsong is a signal…And the definition of a signal is that it elicits a response in the receiver. Previous studies hadn’t approached the question from that angle, and it’s an important one.”

During the non-breeding season, both sexes of sparrows use song to establish and maintain dominance in relationshipsDuring the breeding season, however, a male singing to a female is almost certainly courting her, while a male singing to another male is challenging an interloper.

For the females in the breeding state every region of the mesolimbic reward pathway that has been reported to respond to music in humans, and that has a clear avian counterpart, responded to the male birdsongFemales in the non-breeding state, however, did not show a heightened response.
And the testosterone-treated males listening to another male sing showed an amygdala response, which may correlate to the amygdala response typical of humans listening to the kind of music used in the scary scenes of horror movies.

“The neural response to birdsong appears to depend on social context, which can be the case with humans as well…Both birdsong and music elicit responses not only in brain regions associated directly with reward, but also in interconnected regions that are thought to regulate emotion. That suggests that they both may activate evolutionarily ancient mechanisms that are necessary for reproduction and survival.”

A major limitation of the study…is that many of the regions that respond to music in humans are cortical, and they do not have clear counterparts in birds.

Study #2:

Is that song sexy or just so-so?

A songbird study conducted by Emory University sheds new light on this question, showing that a change in hormone levels may alter the way we perceive social cues by altering a system of brain nuclei, common to all vertebrates, called the “social behavior network.”

“Social behaviors such as courtship, parenting and aggression depend primarily on two factors: a social signal to trigger the behavior, and a hormonal milieu that facilitates or permits it….Our results demonstrate a possible neural mechanism by which hormones may alter the processing of these signals and affect social decision-making.”

Across most of the network,

song-specific neural responses were higher in the “breeding” females than the “non-breeding” ones. But the effects of estrogen were not identical in every regionIf every node in the network just responded more in the presence of estrogen, then we’d conclude that estrogen acts as an on-off switchBut what we’re seeing is more complicated than that. Some activity goes up with estrogen, and some goes down. We are seeing how estrogen changes the big picture as the brain processes social information.”

The findings suggest that the perceived meaning of a stimulus may be related to the activity in the entire social behavior network, rather than a single region of the brain. “The same neural mechanism may be operating in humans,”

“In women, preferences for male faces, voices, body odors and behavior change over the course of the menstrual cycle as estrogen levels rise and fall. Our work with these songbirds shows a possible neural basis for those changes.”