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ucsdhealthsciences:

Scientists Discover “Dimmer Switch” For Mood Disorders

Researchers at University of California, San Diego School of Medicine have identified a control mechanism for an area of the brain that processes sensory and emotive information that humans experience as “disappointment.”

The discovery of what may effectively be a neurochemical antidote for feeling let-down is reported Sept. 18 in the online edition of Science.

“The idea that some people see the world as a glass half empty has a chemical basis in the brain,” said senior author Roberto Malinow, MD, PhD, professor in the Department of Neurosciences and neurobiology section of the Division of Biological Sciences. “What we have found is a process that may dampen the brain’s sensitivity to negative life events.”

Because people struggling with depression are believed to register negative experiences more strongly than others, the study’s findings have implications for understanding not just why some people have a brain chemistry that predisposes them to depression but also how to treat it.

Specifically, in experiments with rodents, UC San Diego researchers discovered that neurons feeding into a small region above the thalamus known as the lateral habenula (LHb) secrete both a common excitatory neurotransmitter, glutamate, and its opposite, the inhibitory neurotransmitter GABA.

Excitatory neurotransmitters promote neuronal firing while inhibitory ones suppress it, and although glutamate and GABA are among two of the most common neurotransmitters in the mammalian brain, neurons are usually specialists, producing one but not both kinds of chemical messengers.

Indeed, prior to the study, there were only two other systems in the brain where neurons had been observed to co-release excitatory and inhibitory neurotransmitters – in a particular connection in the hippocampus and in the brainstem during development of the brain’s auditory map.

“Our study is one of the first to rigorously document that inhibition can co-exist with excitation in a brain pathway,” said lead author Steven Shabel, a postdoctoral researcher with Department of Neurosciences and neurobiology section of the Division of Biological Sciences. “In our case, that pathway is believed to signal disappointment.”

The LHb is a small node-like structure in the epithalamus region of the brain that is critical for processing a variety of inputs from the basal ganglia, hypothalamus and cerebral cortex and transmitting encoded responses (output) to the brainstem, an ancient part of the brain that mammals share with reptiles.

Experiments with primates have shown that activity in the LHb increases markedly when monkeys are expecting but don’t get a sip of fruit juice or other reward, hence the idea that this region is part of a so-called disappointment pathway.

Proper functioning of the LHb, however, is believed to be important in much more than just disappointment and has been implicated in regulating pain responses and a variety of motivational behaviors. It has also been linked to psychosis.

Depression, in particular, has been linked to hyperactivity of the LHb, but until this study, researchers had little empirical evidence as to how this overstimulation is prevented in healthy individuals given the apparent lack of inhibitory neurons in this region of the brain.

"The take-home of this study is that inhibition in this pathway is coming from an unusual co-release of neurotransmitters into the habenula," Shabel said. Researchers do not know why this region of the brain is controlled in this manner, but one hypothesis is that it allows for a more subtle control of signaling than having two neurons directly counter-acting each other.

Researchers were also able to show that neurons of rodents with aspects of human depression produced less GABA, relative to glutamate. When these animals were given an antidepressant to raise their brain’s serotonin levels, their relative GABA levels increased.

"Our study suggests that one of the ways in which serotonin alleviates depression is by rebalancing the brain’s processing of negative life events vis-à-vis the balance of glutamate and GABA in the habenula," Shabel said. "We may now have a precise neurochemical explanation for why antidepressants make some people more resilient to negative experiences."

Pictured: Basal ganglia neurons (green) feed into the brain and release glutamate (red) and GABA (blue) and sometimes a mix of both neurotransmitters (white).

(via albfit)

"Biologists call a small male fish who darts in to fertilize eggs a “sneaker,”, a medium male who resembles a female a “female mimic,”, and a large aggressive territorial male a “parental,” to place a positive spin of his egg guarding. Both the sneaker and the female mimic are “sexual parasites” of the parental male’s “investment” in nest construction and territorial defense. The sneaker and the female mimic are said to express a gene for “cuckoldry,” as though the parental male were married to a female in his territory and victimized by her unfaithfulness. In fact, a territorial male and the female who is temporarily in his territory are not pair-bonded. Scientists sneak gender stereotypes into the primary literature and corrupt its objectivity. Are these descriptions only harmless words? No. The words affect the view of nature that emerges from biology."
Joan Roughgarden (2004) Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People, University of California Press, Berkley
(via 420-catnip)

(Source: onychophorawesome, via laughterkey)

neurosciencestuff:

Study links physical activity in older adults to brain white-matter integrity
The study, reported in the journal PLOS ONE, tracked physical activity in 88 healthy but “low-fit” participants aged 60 to 78. The participants agreed to wear accelerometers during most of their waking hours over the course of a week, and also submitted to brain imaging.
The team found that the brains of older adults who regularly engaged in moderate-to-vigorous exercise generally “showed less of the white-matter lesions,” Burzynska said.
The association between physical activity and white-matter structural integrity was region-specific, the researchers reported. Older adults who engaged more often in light physical activity had greater structural integrity in the white-matter tracts of the temporal lobes, which lie behind the ears and play a key role in memory, language, and the processing of visual and auditory information.
In contrast, those who spent more time sitting had lower structural integrity in the white-matter tracts connecting the hippocampus, “a structure crucial for learning and memory,” Burzynska said.
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neurosciencestuff:

Study links physical activity in older adults to brain white-matter integrity

The study, reported in the journal PLOS ONE, tracked physical activity in 88 healthy but “low-fit” participants aged 60 to 78. The participants agreed to wear accelerometers during most of their waking hours over the course of a week, and also submitted to brain imaging.

The team found that the brains of older adults who regularly engaged in moderate-to-vigorous exercise generally “showed less of the white-matter lesions,” Burzynska said.

The association between physical activity and white-matter structural integrity was region-specific, the researchers reported. Older adults who engaged more often in light physical activity had greater structural integrity in the white-matter tracts of the temporal lobes, which lie behind the ears and play a key role in memory, language, and the processing of visual and auditory information.

In contrast, those who spent more time sitting had lower structural integrity in the white-matter tracts connecting the hippocampus, “a structure crucial for learning and memory,” Burzynska said.

(via iwakeupblack)

juhavantzelfde:

(via ISIS’s Call of Duty - The New Yorker)

The similarities between ISIS recruitment films and first-person-shooter games are likely intentional. Back in June, an ISIS fighter told the BBC that his new life was “better than that game Call of Duty.” Video-game-themed memes traced back to ISIS have been floating around the Internet for months, including one that reads, “THIS IS OUR CALL OF DUTY AND WE RESPAWN IN JANNAH.” (“Respawn” is the gamer word for reincarnate.) Another ISIS video, as the Intercept notes, looks like a deliberate homage to Grand Theft Auto. Audio clips that sound much like ones in Call of Duty have been spliced into otherISIS videos. Many of the ISIS recruitment videos are dedicated to showcasing rocket launchers, mines, and assault rifles, as if to say, “If you join us, you’ll get to shoot these things.”

(via juhavantzelfde)