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Brain waves guide us in spotlighting surprises -- ScienceDaily
By measuring thousands of neurons along the surface, or cortex, of the brain in animals as they reacted to predictable and surprising images, the researchers observed that low frequency alpha and beta brain waves, or rhythms, originating in the brain's frontal cognitive regions tamped down neural activity associated with predictable stimuli. That paved the way for neurons in sensory regions in the back of the brain to push forward information associated with unexpected stimuli via higher-frequency gamma waves. The backflow of alpha/beta carrying inhibitory predictions typically channeled through deeper layers of the cortex, while the forward flow of excitatory gamma carrying novel stimuli propagated across superficial layers.
Mathematical framework explores how the brain keeps a beat - Neuroscience News
Using neurobiological principles, the researchers built a mathematical model of a group of neurons that can cooperate to learn a musical beat from a rhythmic stimulus and keep the beat after the stimulus stops. The model demonstrates how a network of neurons could act as a “neuronal metronome” by accurately estimating time intervals between beats within tens of millisecond accuracy. This metronome relies on rhythmic brain activity patterns known as gamma oscillations to keep track of time.
An Amygdala-Hippocampus Subnetwork that Encodes Variation in Human Mood: Cell
The most common subnetwork, found in 13 of 21 subjects, was characterized by β-frequency coherence (13-30 Hz) between the amygdala and hippocampus. Increased variability of this subnetwork correlated with worsening mood across these 13 subjects. Moreover, these subjects had significantly higher trait anxiety than the 8 of 21 for whom this amygdala-hippocampus subnetwork was absent.
Brain signature of depressed mood unveiled in new study: Direct recordings of human brain activity link memory, emotion, and anxiety during bouts of low mood -- ScienceDaily
Then, to compare results across the unique brains and distinct electrode placements of all 21 research participants, the researchers mapped each subject's ICNs onto neural connectivity diagrams. Comparing these standardized records of network activity across subjects revealed several "cliques" -- groups of brain regions that repeatedly became synchronized at specific frequencies, and were therefore likely to represent functional brain networks.
One such clique was highly active and coordinated in 13 research participants, all of whom had also scored high on a psychological assessment of baseline anxiety conducted prior to the start of the study. In these same individuals, changes in the activity of this brain network were also highly correlated with day-to-day bouts of low or depressed mood. This mood-related network was characterized by so-called beta waves -- synchronized oscillations between 13 and 30 cycles per second -- in the hippocampus and amygdala, two deep brain regions which have long been linked, respectively, to memory and to negative emotion.
Sohal said the research team was at first taken aback by the clarity of the finding. "We were quite surprised to identify a single signal that almost completely accounted for bouts of depressed mood in such a large set of people," said Sohal. "Finding such a powerfully informative biomarker was more than what we'd expected at this stage of the project."
Surprisingly, this powerful link between of mood-associated beta waves in the amygdala and hippocampus was entirely absent from eight other research participants, all of whom had comparatively low preexisting anxiety, suggesting new questions about how the brains of people prone to anxiety may differ from others in how they process emotional situations.
Bravery cells found in the hippocampus -- ScienceDaily
In an article published in the journal Nature Communications the authors show that neurons known as OLM cells, when stimulated, produce a brain rhythm that is present when animals feel safe in a threatening environment (for example, when they are hiding from a predator but aware of the predator's proximity). The study, produced by Drs. Sanja Mikulovic, Ernesto Restrepo, Klas Kullander and Richardson Leao among others, showed that anxiety and risk-taking behaviour can be controlled by the manipulation of OLM cells. To find a pathway that quickly and robustly modulates risk-taking behaviour is very important for treatment of pathological anxiety since reduced risk-taking behaviour is a trait in people with high anxiety levels.
The heart: Digital or analog? Researchers shed dramatic light on heart bioelectricity disorders -- ScienceDaily
"Sodium channels are literally stuck together between cells in way that seems to ensure that the firing of channels in one cell sparks partnering channels in the neighboring cell," Gourdie said. "The molecular machinery seems to be in place for bioelectrical signals to step between heart cells, not wholly unlike how impulses jump between nerve cells in a stepping-stone-like manner at neural synapses."
The spotlight of attention is more like a strobe light -- ScienceDaily
"Our subjective experience of the visual world is an illusion," said Sabine Kastner, a professor of psychology and the Princeton Neuroscience Institute (PNI). "Perception is discontinuous, going rhythmically through short time windows when we can perceive more or less."
The researchers use different metaphors to describe this throb of attention, including a spotlight that waxes and wanes in its intensity. Four times per second -- once every 250 milliseconds -- the spotlight dims and the house lights come up. Instead of focusing on the action "onstage," your brain takes in everything else around you, say the scientists.
Their work appears as a set of back-to-back papers in in the Aug. 22 issue of Neuron; one paper focuses on human research subjects, the other on macaque monkeys.
"The question is: How can something that varies in time support our seemingly continuous perception of the world?" said Berkeley's Randolph Helfrich, first author on the human-focused paper. "There are only two options: Is the data wrong, or is our understanding of our perception biased? Our research shows that it's the latter. Our brains fuse our perceptions into a coherent movie -- we don't experience the gaps."
Brain Activity Alternates While Stepping - Neuroscience News
The researchers found that activity in the 20-30 Hz (beta) range alternated between the left and right STN when the opposite foot touched the ground and the other foot was to be raised. The introduction of a metronome synchronized to the cartoon steps improved participants’ accuracy and enhanced their STN beta activity accordingly.
The Yogi masters were right -- meditation and breathing exercises can sharpen your mind: New research explains link between breath-focused meditation and attention and brain health -- ScienceDaily
Michael Melnychuk, PhD candidate at the Trinity College Institute of Neuroscience, Trinity, and lead author of the study, explained: "Practitioners of yoga have claimed for some 2,500 years, that respiration influences the mind. In our study we looked for a neurophysiological link that could help explain these claims by measuring breathing, reaction time, and brain activity in a small area in the brainstem called the locus coeruleus, where noradrenaline is made. Noradrenaline is an all-purpose action system in the brain. When we are stressed we produce too much noradrenaline and we can't focus. When we feel sluggish, we produce too little and again, we can't focus. There is a sweet spot of noradrenaline in which our emotions, thinking and memory are much clearer."
"This study has shown that as you breathe in locus coeruleus activity is increasing slightly, and as you breathe out it decreases. Put simply this means that our attention is influenced by our breath and that it rises and falls with the cycle of respiration. It is possible that by focusing on and regulating your breathing you can optimise your attention level and likewise, by focusing on your attention level, your breathing becomes more synchronised."
Cells communicate in a dynamic code: A critically important intercellular communication system is found to encode and transmit more messages than previously thought. -- ScienceDaily
The team studied two chemically similar Notch ligands, dubbed Delta1 and Delta4. They discovered that despite the ligands' similarity the two activated the same receptor with strikingly different temporal patterns. Delta1 ligands activated clusters of receptors simultaneously, sending a sudden burst of transcription factors down to the nucleus all at once, like a smoke signal consisting of a few giant puffs. On the other hand, Delta4 ligands activated individual receptors in a sustained manner, sending a constant trickle of single transcription factors to the nucleus, like a steady stream of smoke.
Neurons get the beat and keep it going in drumrolls -- ScienceDaily
The researchers recorded the activities of individual neurons in the hippocampus, which is located in the lower center of the brain, with a robotic device called a patch clamp. It's a hollow glass needle one micron in diameter that latches onto a single neuron via suction and measures its electrical activity.
The researchers observed electrical rumblings, symbolized here by a drumroll. And they observed spikes, symbolized here by a cymbal crash.
Though the pattern of rumblings wasn't uniform, it rose and fell like a drumroll undulating between softer and louder volumes. Spikes occurred much more rarely than drumbeats, but with notable timing.
"The spikes repeated in the same spots with high precision, so they weren't just random," Singer said. "They came around the peaks of rumblings, not always right on top of a peak but within a hair of it."
It would be like a cymbal crash hitting not every time, but every few times the undulating drumroll topped a volume peak. And the drumroll-cymbal-crash patterns sustained themselves for surprisingly long periods.
"The time periods of activity that was structured like this were much longer than we expected," Singer said. "People have shown sustained periods of signaling like this for 100 to 300 milliseconds before, but this appears to be the first time it's been seen for 900 milliseconds (nearly a full second), and it may go on even longer."
