- via Science 20 ^^"The most popular theory assumes that a clock-like mechanism -- which generates and counts regular fixed movements -- underlies timing in the brain. In contrast, Buonomano suggests a physical model that operates without using a clock. He offers an analogy to explain how it works.
"If you toss a pebble into a lake," he explained, "the ripples of water produced by the pebble's impact act like a signature of the pebble's entry time. The farther the ripples travel the more time has passed.
"We propose that a similar process takes place in the brain that allows it to track time," he added. "Every time the brain processes a sensory event, such as a sound or flash of light, it triggers a cascade of reactions between brain cells and their connections. Each reaction leaves a signature that enables the brain-cell network to encode time."
The UCLA team used a computer model to test this theory. By simulating a network of interconnected brain cells in which each connection changed over time in response to stimuli, they were able to show that the network could tell time.
Their simulations indicated that a specific event is encoded within the context of events that precede it. In other words, if one could measure the response of many neurons in the brain to a tone or a flash of light, the response would not only reveal the nature of the event, but the other events that preceded it and when they occurred.
The UCLA team tested the model by asking research volunteers in the study to judge the interval between two auditory tones under a variety of different conditions. The researchers found that volunteers' sense of timing was impaired when the interval was randomly preceded by a "distracter" tone.
"Our results suggest that the timing mechanisms that underlie our ability to recognize speech and enjoy music are distributed throughout the brain, and do not resemble the conventional clocks we wear on our wrists," said Buonomano.
Processing speed is not fixed in the brain; there is no system clock
The speed of neural information processing is subject to a variety of constraints, including the time for electrochemical signals to traverse axons and dendrites, axonal myelination, the diffusion time of neurotransmitters across the synaptic cleft, differences in synaptic efficacy, the coherence of neural firing, the current availability of neurotransmitters, and the prior history of neuronal firing. Although there are individual differences in something psychometricians call “processing speed,” this does not reflect a monolithic or unitary construct, and certainly nothing as concrete as the speed of a microprocessor. Instead, psychometric “processing speed” probably indexes a heterogenous combination of all the speed constraints mentioned above.
Similarly, there does not appear to be any central clock in the brain, and there is debate as to how clock-like the brain’s time-keeping devices actually are. To use just one example, the cerebellum is often thought to calculate information involving precise timing, as required for delicate motor movements; however, recent evidence suggests that time-keeping in the brain bears more similarity to ripples on a pond than to a standard digital clock.
via Sciencedaily ^^
For decades, neuroscientists have theorized that the brain "time stamps" events as they happen, allowing us to keep track of where we are in time and when past events occurred. However, they couldn't find any evidence that such time stamps really existed -- until now.
An MIT team led by Institute Professor Ann Graybiel has found groups of neurons in the primate brain that code time with extreme precision. "All you do is time stamp everything, and then recalling events is easy: you go back and look through your time stamps until you see which ones are correlated with the event," she says. (...)
Future studies in this area could shed light on how the brain produces these time stamps and how this function can control behavior and learning. The work also raises questions regarding how the brain interprets the passage of time differently under different circumstances.
"Sometimes time moves quickly, and in some situations time seems to slow down. All of this ultimately has a neural representation," says Strick.
- Dan RD: Nemes trigger cascades of Emo and Cog which enhance nStrings between experience and environment. This seems akin to the ripples that stimulate 'coherence potentials', (see NewScientist below) leading to a time stamp upon an event. Not necessarily a linear process caused by a neme in an environment, so much as its potential to cohere meaning with the nStrings of an individual's mind.
- Dan RD: This is a core teaching to Nemetics. How an individual nemifies their perception of Time and Space seems to determine its shape.
Via Newscientist ^^
Subatomic particles do it. Now the observation that groups of brain cells seem to have their own version of quantum entanglement, or "spooky action at a distance", could help explain how our minds combine experiences from many different senses into one memory.
Previous experiments have shown that the electrical activity of neurons in separate parts of the brain can oscillate simultaneously at the same frequency – a process known as phase locking. The frequency seems to be a signature that marks out neurons working on the same task, allowing them to identify each other.
Dietmar Plenz and Tara Thiagarajan at the National Institute of Mental Health in Bethesda, Maryland, wondered whether more complicated signatures also link groups of neurons. To investigate, they analysed neuronal activity using arrays of electrodes implanted in the brains of two awake macaque monkeys and embedded in dish-grown neuron cultures.
In both cases, the researchers noticed that the voltage of the electrical signal in groups of neurons separated by up to 10 millimetres sometimes rose and fell with exactly the same rhythm. These patterns of activity, dubbed "coherence potentials", often started in one set of neurons, only to be mimicked or "cloned" by others milliseconds later. They were also much more complicated than the simple phase-locked oscillations and always matched each other in amplitude as well as in frequency.
- Dan RD: It seems intention is increased with NEM, which results in phase locking and/or time stamping.