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Saturday, August 26, 2017

Do We See the World Like a Movie?

We have the feeling that we experience the world like a continuously sampled data stream. If we perceive multiple objects of events seemingly at the same time, we may actually be multiplexing the several data streams; that is, we take a sample from one data stream, switch to take a sample from the next stream and so onall on a millisecond time scale.

But another possibility is that we perceive objects and events like a movie frame, where the brain takes working-memory snapshots and plays them in succession. Like still frames in a movie, if played at a high-enough speed, the frames will blend in our mind to give the illusion of continuous monitoring.

In either case, we have to account for working memory. That is, we can only hold a small amount of information in our working memory at any one instant, as in being able to dial a seven-digit phone number you just looked up. In the phone number case, does our brain accumulate and buffer the representation of each integer until reaching the working memory holding capacity and then report it to consciousness as a set? Or is each integer transferred to consciousness and concantenated until the working memory capacity is filled?

A profound recent model of perception addresses the issue of continuous or movie-like perception, but unfortunately, it did not take working memory into consideration.  The model did address the issue of how consciousness integrates the static and dynamic aspects of the object of attention. For example, when viewing a white and moving baseball, consciousness apparently tracks both the static white color and shape of the ball and its movement at the same time. Are these two visual features bundled together and made available to consciousness on a continual basis or as a batch frame?
A related issue is the so-called flash-lag illusion. Displaying a moving object and a stationary light flash at the same time and location creates the illusion that the flash is lagging. There is some debate over why this happens, but it does argue against continuous monitoring of linked objects.

Another phenomenon that argues against continuous monitoring is the “color phi” phenomenon. Here, if two differently colored disks are shown at two locations in rapid succession, a viewer perceives just one disk that moves from the first location to the second, and the color of the first disk changes along the illusory path of movement. But the viewer cannot know in advance what the color and location of the second disk is. The brain must construct that perception after the fact.
Another way of studying fusion phenomenon is to show two different colored disks in rapid succession at the same location. In this case, an initial red disk followed by a green disk will be perceived as only one yellow disk. A viewer cannot consciously recognize the individual properties if there is not enough time between the two disks. This suggests that information is batched processed unconsciously and later made available to conscious awareness. Transcranial magnetic stimulation can disrupt the fusion, but only for about 400 milliseconds after the first stimulus when presumably the processing is unconscious. Since the presentation of the two disks only takes about 60 msecs, it means that unconscious processing of the fusion takes some 340 milliseconds before the results become available for conscious recognition.

Similar fusion can occur with other sense modalities. For example, the “cutaneous rabbit” effect is a somatosensory fusion illusion in which touch stimulation of first the wrist followed quickly by stimulation near the elbow produces the feeling of touch along the nerve pathway between the two points, as if a rabbit was hopping along the nerve. There is no way for conscious mind to know the pathway without the second touch near the elbow actually occurring. Perception of that pathway information is delayed until the information has been processed unconsciously.

So while these examples argue against continuous conscious monitoring of sensation, they don’t really fit well with the movie-frame idea either. We can distinguish two visual stimuli only 3 msecs apart, but a snapshot model that samples stimuli say every 40 msecs would miss the second stimulus. So to reconcile these conflicting possibilities, the authors advance a two-step model in which sensations are processed unconsciously at high speed, but the conscious percept is reported periodically or is read out when unconscious activity reaches a certain threshold or when there is top-down demand.. This fits the data from others that conscious awareness is delayed after the actual sensory event. For visual stimuli, this delay can be as long as 400 msecs.

Here the question of interest is why sensory awareness might require a mixture of continuous monitoring and periodic reporting of immediately prior data segments. Continuous monitoring and processing permits high-temporal resolution. Snapshot reporting conserves neural resources because information accumulates as a batch (a few bytes) before becoming available to consciousness. The really interesting question is what, if anything, happens to that string of movie-like snapshots that are captured in consciousness. How do these frames affect subsequent unconscious processing in the absence of further sensory input? Can unconscious processes capture and operate on the frames of conscious data? Or can successive frames of conscious data be processed batch wise in consciousness? A useful analogy might be whole-word reading. A beginning reader must sound out each letter in a word, which is comparable to the high-resolution time tracking of sensory input. However, whole word reading allows the more efficient capture of meaning because meaning has been batch pre-processed.

How do these ideas fit with the claim of other scholars that consciousness is just an observer witnessing the movie of life as it occurs? However, this assumption ignores the role that consciousness might have in reasoning, making decisions, and issuing commands. I argue this point elsewhere in my books, Mental Biology, and Making a Scientific Case for Conscious Agency and Free Will.

Research claimed as showing that free will is illusory needs reinterpretation in light of this two-step model of perception. Those experiments typically involved asking a subject to make a simple movement, like press a button, whenever they “freely” want to do so. They are to note when they made the decision by looking at a large, high-resolution clock. At the same time, their brain activity is monitored before, during, and after the chain of events.

The first event is the intention to button press. Intention is a conscious event. Was it preceded by unconscious high-resolution processing? If so, what was the need for high resolution? Or maybe this is just the way the brain is built to operate. The button press decision-making is a slow, deliberative process, which perhaps could be handled consciously as a slow progression of successive frames of conscious thought. Critics may say that there is no such thing as conscious processing, but there is no evidence for such conjecture. Once an intent is consciously realized, the subject is now thinking about when to make the press. This decision may well be determined unconsciously, but again there is no need for high temporal resolution. Moreover, there are intervening conscious steps, where the subject may think to himself, “I just did a press. Shouldn’t I wait? Is there any point in making many presses with short intervals? Or with long intervals? Or with some random mixture? Are each of these questions answered by the two-step model of sensory processing?” However the decision developed, corresponding brain electrical activity is available to be measured.

Then, there is the actual button press, the conscious realization that it has occurred, and the conscious registration of the time on the clock when the subject thought the decision to button press was made. Does the two-step model apply here? If so, there has to be a great deal of timing delays between what actually happened consciously in the brain and what the subject eventually realized the conscious thoughts.

The point is that the two-stage model of perception may have profound implications beyond sensation that involve ideation, reasoning, decision-making, and voluntary behavior. I have corresponded with the lead author to verify that I have a correct understanding of the publication. He said that his group does plan to study the implications for working memory and for free will.


Herzog, M. H., Kammer, Thomas, and Scharnowski, F. (2017). Time slices: What is the duration of a pecept? PLOS. April 12. Hrp://

Tuesday, August 15, 2017

Is Your Brain Older Than You Are?

"You are as old as you think you are," the saying goes. Well, not quite. You, that is the inner you in your brain, is as old as your brain is. But your brain age may or may not correlate with chronological age.

The other day at my gym workout, I again saw a young black guy, built like Captain America, whose workout schedule sometimes overlaps with mine. We had not met, and out of the blue he came up to me and said, “You are my inspiration. You inspire me to be able to work out like you when I get your age.” Wow! I inspire somebody! Then my balloon popped when I realized that he knew I was old just by looking at me. My body may not look like I’m 83, but I guess hair loss and the lines in my face betray me.

The point of this story is that the bodily organs do not have the same rate of aging. Skin ages rather conspicuously in most older people. Specific organs may age at different rates depending on what they have been exposed to, for example skin and sun, liver and alcohol, lungs and smoking, or fat tissue and too many calories. The brain may age more rapidly than other organs if you damage it with drugs or concussion, or clog its small arteries with high cholesterol, or shrivel its synaptic connections by lack of mental stimulation or not coping with stress.

Is there some biological equivalent to tree rings to show how old your brain actually is?  A scientist at the Imperial College in London, James Cole, is developing an interesting approach for estimating brain age. Moreover, the technique seems to predict approximately when you will die.

In the study thus far, MRI brain scans were taken on 2,001 people between 18 and 90 years of age. A computer algorithm evaluated these scans to construct a frame of reference for what is normal for a given age. Then the scans from 669 adults, all born in 1936, were compared against the norms to determine whether the 81 year-old brains were normal for that age.

The people whose brains were older than normal performed more poorly on fitness measures such as lung function, walking speed, and fluid intelligence. They also had increased risk of dying sooner. Predictions became more reliable when the brain-scan data were combined with the methylation of blood DNA, a marker of life experience effects on gene expression.

Another group of workers at UCLA had determined that these kinds of gene changes predict the risk of mortality. This group, headed by Steve Horvath, evaluated these gene expression changes in various tissues of a 112-year-old woman and found that her brain was younger than her other tissues. A "young" brain will help you to live longer and also have a better quality of life.

There are two take-home implications of such research. The first is that lifestyle and environmental influences affect one's age and that not all tissues age at the same rate. The second is that it may now be possible to test which interventions to slow brain aging actually work. We currently think aging brain is slowed by exercise, by anti-oxidants, by healthy diets, by reducing stress. Having objective measures for aging in general and brain in particular will help us decide how well such preventive measures work. There is also the possibility that such measurement tools may help us identify who is aging too fast and why that is happening, which in turn may lead to better therapy. 

While we wait on technology, there is one symptom of excessive brain aging we can all notice: memory loss. As the title of my book suggests, memory is the canary in your brain's coal mine.

Get the most out of life as you age. You can slow brain aging by following the advice in Memory Medic's inexpensive e-book, "Improve Your Memory for a Healthy Brain. Memory Is the Canary in Your Brain's Coal Mine." It is available in Kindle at Amazon and all formats at


Kwon, Diana (2017). How to tell a person's "brain age." The Scientist. May 22.

Cole, James H. et al. (2015). Prediction of brain age suggests accelerated atrophy after traumatic brain injury. Annals Neurology.77(4), 571-581.  doi: 10.1oo2/ana.24367.

Friday, August 04, 2017

Mental Down-time Affects Memory

Research has shown that recent experiences are reactivated during sleep and wakeful rest. This "downtime" recall of memories is part of the process for consolidating long-term memory and serves as memory rehearsal that can strengthen the memory. Thus, the old saying, "all work and no play makes Jack a dull boy," might be re-framed, "all work and no rest makes Jack a poor learner."
To expand on this idea, a study was conducted to test whether this memory enhancing effect of mental downtime applied to new learning of related material. In other words, does downtime help form memories for new experiences as well as it does for recent past experiences? The researchers hypothesized that the degree to which memory processes are engaged during mental downtime determines whether or not prior knowledge promotes or interferes with new learning.

To test this idea, human adults were trained on learning face-object pairs over four repetitions. This initial learning was followed by fMRI brain scans while subjects engaged in passive mental downtime and during a new learning period in which a new set of face-object pairs was presented, except that the same object was used as before in order to provide a learning task that overlapped and related to the first task. Also, there was a new task in which both face and object were different from those in the first task. After scanning, subjects completed a cued recall test for memory of the new learning task.

In the initial learning task, all subjects achieved near-perfect recall during the last of the four repetitions. The fMRI data of interest was the activity level in the face-recognition areas of the cerebral cortex during the mental downtime, where the level of neural activity predicted memorization of the new learning, both overlapping and non-related face-object pairs. That is, if some face-area fMRI activity was present during the down-time, learning of related new learning was more effective.

New learning of face-object pairs was better when the new pairs overlapped the earlier pre-training pairs, suggesting that the initial learning was reactivated during mental rest and used to promote the new learning. However, this did not occur in nearly half of the subjects, and recall was actually poorer than with original pairs. This process is well known from other studies, and is termed proactive interference. In other words, prior learning may help or hinder related new learning, depending on the situation and individual differences. It appears that prior learning promotes new learning if the original learning is particularly strong. Strong initial learning is better reactivated during downtime and is more available to contribute to the learning of related new material.
Bottom-line: the right kind of mental rest can help strengthen memories and make it easier to learn related new information. During mental rest, it probably helps to avoid new learning tasks, to allow the brain to work on the residual effect of the initial learning.  Such rest probably works best on initial memories that are strongly encoded.

As for practical application in education, the authors suggested that before presenting new information, it would help for learners to recall some related things they already know. Their example was for a professor to begin a lecture by asking students questions on some aspects of the lecture that students should already know something about. I would add some additional tactics:

1. Strengthen initial encoding by at least four forced-recall attempts at the time of initial learning. Add to the strengthening by using mental images and mnemonic devices.
2.  Introduce breaks in presenting information, with a mental rest period in between.
3. Avoid new learning or mental challenges during the down-time period.
4. Review information presented in the past that relates to new information that is to be learned (as in reviewing past lecture notes before a new lecture).
5. Periodically think about what you have learned as it might relate to what you want to learn next.

Readers should also want to read Memory Medic's e-book for students (Better Grades, Less Effort, available at, or the paperbacks available at Amazon and bookstores (for parents and teachers: The Learning Skills Cycle, or for a general audience: Memory Power 101 (available at Amazon and bookstores).


Schlichting, Margaret L., and Preston, Alison R. (2014). Memory reactivation during rest supports upcoming learning of related content. Proc. Nat. Acad. Sci. (USA). 111 (44), 15845-15850