In the latest issue of this monthly digest series you can learn what marijuana has to do with Alzheimer's, what old monkeys and old humans have in common, why it's ok to forget stuff, and much more.
Changing our understanding of consciousness
Measuring and defining consciousness has been an ongoing challenge for neuroscientists, philosophers and psychologists for centuries. The concept of levels of consciousness is still mostly theoretical, such as the Glasgow Coma Scale (right), which ranks consciousness based on various behavioral criteria. Professor Jakob Hohwy from the School of Philosophical, Historical and International Studies at Monash University and his team have argued that the idea of consciousness levels is wrong. Professor Hohwy and his colleagues believe that unlike the human body's more objective measurements, such as blood pressure and height, consciousness has dimensions rather than discrete levels.
For example, a person in a vegetative state can't lift their arm when asked, while a conscious person can. But ask either to imagine themselves playing tennis—as a now famous study by co-author Adrian Owen of the University of Western Ontario did—and their brains may well light up in the same way. Clearly, their state of consciousness differs, however both may share an awareness and ability to respond to verbal demands.
The Hohwy team argues that the notion of a single scale doesn't fit within the little we know about consciousness. They argue that subjective experience cannot be partial. "It's either something you have or you don't. And if subjective experience can't be put on a single sliding scale, neither can consciousness," Hohwy says.
Rather than asking how conscious a person is, a better question might be to ask what the person is conscious of. Are they conscious of loved ones’ voices at their bedside, or only unintelligible noises? This could mean additional tests, such as brain imaging, to assess a person’s cognitive abilities. Gaining a greater understanding of consciousness could lead to more ethical end-of-life decisions for people with severe brain injuries.
The research was published in Trends in Cognitive Neurosciences, and can be accessed freely here.
Marijuana compound removes toxic Alzheimer's protein from the brain
Tetrahydrocannabinol (THC), the active compound found in marijuana, has been found to promote the removal of toxic clumps of amyloid beta protein in the brain, which are thought to kickstart the progression of Alzheimer's disease. The finding supports the results of previous studies that found evidence of the protective effects of cannabinoids, including THC, on patients with neurodegenerative disease.
"Although other studies have offered evidence that cannabinoids might be neuroprotective against the symptoms of Alzheimer's, we believe our study is the first to demonstrate that cannabinoids affect both inflammation and amyloid beta accumulation in nerve cells," says David Schubert from the Salk Institute for Biological Studies in California.
If you're not familiar with this special little compound, it's not only responsible for the majority of marijuana's psychological effects—including the high—thanks to its natural pain-relieving properties, it's also been touted as an effective treatment for the symptoms of everything from HIV and chemotherapy to chronic pain, post traumatic stress disorder, and stroke. The compound works by passing from the lungs to the bloodstream, where it attaches to two types of receptors, cannabinoid receptor (CB) 1 and 2, which are found on cell surfaces all over the body. In the brain, these receptors are most concentrated in neurons associated with pleasure, memory, thinking, coordination and time perception, and usually bind with a class of lipid molecules called endocannabinoids that are produced by the body during physical activity to promote cell-to-cell signalling in the brain.
Over the years, research has suggested that by binding to these receptors, THC could be having another effect on ageing brains, because it appears to help the body clear out the toxic accumulations (or 'plaques') of amyloid beta.
Back in 2006, researchers at the Scripps Research Institute found that THC inhibits the formation of amyloid plaques by blocking the enzyme in the brain that produces them, and now Schubert and his team have demonstrated that it can also eliminate a dangerous inflammatory response from the nerve cells, ensuring their survival.
"Inflammation within the brain is a major component of the damage associated with Alzheimer's disease, but it has always been assumed that this response was coming from immune-like cells in the brain, not the nerve cells themselves," says one of the team, Antonio Currais. "When we were able to identify the molecular basis of the inflammatory response to amyloid beta, it became clear that THC-like compounds that the nerve cells make themselves may be involved in protecting the cells from dying."
What old monkeys and old humans have in common
Humans spend less time monkeying around as they get older—and so do monkeys.
Dr. Freund, Julia Fischer, and their colleagues, who study primate cognition at the Primate Center in Goettingen, Germany wanted to know how age influenced the behavior of more than 100 Barbary macaque monkeys living in an enclosed 50-acre park in southern France. They studied how the monkeys, ranging in age from 4 to 29 (which is about 105 in human years, according to Dr. Fischer), responded to physical objects like novel toys and tubes baited with food; social interactions like grooming "friends" or fighting; and social information, like photos or calls of "friends" and "strangers".
What they found is that aging monkeys show physical losses and reductions in social activity, much like humans do. Monkeys' interest in toys waned when they became reproductive, and around 20, (their "retirement age") monkeys, like humans, had fewer social contacts and approached others less frequently. What surprised the researchers is that this apparent withdrawal wasn't driven by a social tendency to avoid old monkeys: Younger monkeys still approached and groomed their elders. And it wasn't that older monkeys just weren't interested in anything: They still responded to photos of other monkeys and hissed at others during fights. "They are still very much tuned into what's going on," said Dr. Fischer. "But they don’t want to participate themselves."
Whatever the reason behind the behavior of these distantly-related species is, there's a take-home message for humans: "Our behaviors that seem very much the result of our deliberation and choice," said Dr. Freund, "might be more similar to our primate ancestors than we might think."
New research from Umeå University in Sweden indicates that dispensed medication for psychiatric diagnosis can be related to air pollution concentrations. The study covers a large part of the Swedish population. (BMJ Open)
Human eyes are capable of detecting a single photon—the tiniest possible speck of light—researchers from the Rockefeller University has found. They also found that the human eye is more sensitive to single photons shortly after it has seen another photon. This was "an unexpected phenomenon that we just discovered when we analyzed the data," said physicist Alipasha Vaziri. These results may settle the debate on the ultimate limit of the sensitivity of the human visual system, a puzzle scientists have pondered for decades. Scientists are now anticipating possibilities for using the human eye to test quantum mechanics with single photons. (Nature Communications via ScienceNews)
A team of researchers from the University of California San Diego, The Scripps Research Institute (TSRI), and Illuminaas, developed the first scalable method to identify different subtypes of neurons in the human brain. The research lays the groundwork for "mapping" the gene activity in the human brain and could help provide a better understanding of brain functions and disorders, including Alzheimer's, Parkinson's, schizophrenia and depression. (via NeuroscienceNews)
A team of researchers at Arizona State University's (ASU) Human-Oriented Robotics and Control Lab have developed a system for managing swarms of robots with brain power. ASU's new system can be used to direct a group of small, inexpensive robots to complete a task. If one robot breaks down, it's not a big loss, and the rest can continue with their mission. In the future, humans can use their thoughts to manage a team of robots that will work together to accomplish a goal. (via ZDNet)
Turns out that humans need to forget as part of the brain's system for the management of memories acquired across a lifetime. "Understanding the process of forgetting could have an enormous impact on how we treat a whole range of diseases including Alzheimer's," said Ron Davis, chair of the Department of Neuroscience on the Florida campus of The Scripps Research Institute (TSRI). A new study now highlights how a protein called "Scribble" orchestrates the intracellular signaling processes for forgetting, joining several molecules to forge a pathway. By "knocking down" the expression of the gene that produces Scribble, the researchers produced flies that were able to remember twice as much as normal flies, simply because they failed to forget at the normal rate. The researchers also identified Scribble's crucial role in interacting with other key molecular players for forgetting within the fly brain. (via NeuroscienceNews)
Researchers from the National Institute on Aging in Baltimore discovered that consistent exercising upregulates a protein called cathepsin-B associated with improved memory in mice, Rhesus monkeys, and humans. This previously unrecognized function of cathepsin B may be controversial, as the protein is known to be secreted by tumors and has been implicated in cell death and amyloid plaque formation in the brain. Other studies have found that cathepsin B is neuroprotective and can clear amyloid plaques. van Praag hypothesizes that different levels of the protein and different physiological conditions may yield different effects. Going forward, the researchers want to better understand how cathepsin B is crossing the blood-brain barrier and whether the protein behaves the same in different species. (via NeuroscienceNews)
POSTECH researchers have developed an organic nanofiber based artificial synapse that emulates not only the important working principles and energy consumption of biological synapses but also the morphology. The organic nanofiber (ONF) electronic synapse is very similar to that of nerve fibers, which form crisscrossing grids to enable the high memory density of a human brain. Especially, based on the e-Nanowire printing technique, highly-aligned ONFs can be massively produced with precise control over alignment and dimension. This morphology potentially enables the future construction of high-density memory of a neuromorphic system. (ScienceAdvances via NeuroscienceNews)
Drugs prescribed to treat diabetes could cure Alzheimer's disease, a pioneering new study has found. Scientists believe that the two conditions are so similar that medications already used to control levels of glucose and regulate diabetes could also halt the onset of dementia. The research, published in the journal Diabetologia, was aimed at finding out why the two diseases are so commonly found together in elderly patients. The study also found increased levels of a gene involved in the production of toxic proteins in the brain not only led to Alzheimer's-like symptoms, but also to the development of diabetic complications. (via Telegraph)
Scientists at INSERM in France have shown how the brain anticipates all of the new situations that it may encounter in a lifetime by creating a special kind of neural network that is "pre-adapted" to face any eventuality. The authors demonstrated this by training a reservoir network to perform a novel problem solving task. They then compared the activity of neurons in the model with activity of neurons in the prefrontal cortex of a research primate that was trained to perform the same task. Remarkably, there were striking similarities in the activation of neurons in both the reservoir model and the primate. (via NeuroscienceNews)
Oligodendrocytes, a type of brain cell that plays a crucial role in diseases such as multiple sclerosis, are more diverse than previously thought, according to a new study by researchers at Karolinska Institutet in Sweden. The findings, published in the journal Science, will help increase our understanding of diseases in which these cells are affected and possibly provide clues to future treatment strategies. (Science)