Posts Tagged ‘Dorsolateral prefrontal cortex’

Alzheimer’s Disease (AD)

September 24, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

As AD progresses from earlier to later stages, atrophy starts in the medial temporal lobe, extends to the parietal lobe, and finally includes the frontal lobe. The long-term memory impairment in early AD patients can be attributed to the disrupted processing in the hippocampus and parietal cortex, to regions that have been associated with this cognitive process. As the disease progresses, other cognitive processes are disrupted such as attention and language, which both depend on the dorsolateral prefrontal cortex.

In early AD patients, as atrophy begins in the parietal cortex and the frontal cortex, there have also been reports of increases in fMRI activity within cortical regions. It is unknown whether these increases in cortical fMRI activity reflect a compensatory mechanism, which is often assumed to be the case, or reflect non-compensatory hyperactivity due to neural disruption.

In addition to brain atrophy, AD patients have abnormal high levels of proteins in different brain regions. In the medial temporal lobe, the accumulation of tau protein leads to neurofibrillary tangles. In cortical regions, such as the parietal cortex in early AD, the accumulation of amyloid-B protein leads to amyloid plaques. The neurofibrillary tangles in the medial temporal lobe and amyloid plaques in cortical regions can be assumed to disrupt neural processing in these regions.

Dr. Slotnick writes, “There is an influential hypothesis that there is a causal relationship between default network activity that leads to deposition of amyloid that results in atrophy and disrupted metabolic activity, which impairs long-term memory in AD patients. The regions in the default network are active when participants are not engaged in a task and include the dorsolateral prefrontal cortex, the medial prefrontal cortex, the inferior prefrontal cortex and the medial parietal cortex. In AD patients, amyloid deposition occurs in the same regions, which suggest the default network activity may lead to amyloid deposition. Dr. Slotnick suggests that perhaps higher level of amyloid deposition, which occurs in late AD patients, is necessary to produce atrophy in the frontal cortex.

Healthy memory readers should recognize the similarity between the default network and Kahneman’s System 1 processing. System 1 processing is the default network that needs to be disrupted to engage in System 2 processing, better known as thinking.

Dr. Slotnick continues, “If high amyloid deposition is a causal factor in developing AD, older adults with low levels of amyloid should be at decreased risk for developing this disease. There is some evidence that cognitive engagement and exercise throughout life may reduce the amyloid level in the brains of healthy older adults as a function of cognitive engagement (System 2 processing), and this was compared to the cortical amyloid levels . Participants rated the frequency which they engaged in cognitively demanding tasks such as reading, writing, going to the library, or playing games at five different ages (6, 12, 18, 40, and their current age). Healthy older adults with greater cognitive engagement throughout their lifetime, as measured by the average cognitive activity at the five ages, had lower levels of amyloid in default network regions. Moreover, the healthy older adults in the lowest one-third of lifetime engagement had amyloid levels that were equivalent to AD patients, and the healthy older adults in the highest one-third of lifetime cognitive engagement had amyloid levels that were equivalent to young adults.

It should also be noted that many have died who upon autopsy had levels of amyloid plaque and neurofibrillary tangles definitive of AD, but who never exhibited any of the behavioral or cognitive symptoms characteristics of the disease. The explanation typically offered for these individuals is that they had built a cognitive reserve as a result of the mental activities they had engaged in during their lifetimes.

There is a wide variety of products sold to prevent AD, such as computer games and pills that increase short-term memory. But it should be clear from the posts on cognitive science that the entire brain is involved. That is why the healthy memory blog strongly recommends growth mindsets with continual learning throughout the lifespan. These make heavy use of System 2 processing. Of course, a healthy lifestyle that includes physical exercise must also be part of the mix.

Mild Traumatic Brain Imagery (mTBI)

September 22, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Patients with mTBI do not have any brain abnormalities, as measured using structural neuroimaging methods such as anatomic MRI. The diagnosis of mTBI includes loss of consciousness for less than 30 minutes and post-traumatic amnesia for less than 24 hours. Patients with mTBI can have attention and memory deficits, but these typically resolve within a few weeks.

The performance between mTBI patients and control participants did not differ on the memory task they were performing, but the mTBI patients had a greater extent and magnitude of fMRI activity in the dorsolateral prefrontal cortex and the parietal cortex than control participants.

Fifteen mTBI patients with concussions due to sports-related injuries were tested 2 days, 2 weeks, and 2 months after the injury. Only one of the 15 patients still had symptoms 2 months after the injury. Consistent with the previous research, there were no differences in the performance of the memory task between the patients and the control participants, but there was greater fMRI activity in the mTBI patients than the control participants within the dorsolateral prefrontal cortex at all three time points and within the parietal cortex at the first two time points. This greater fMRI activity 2 months after injury is concerning because they indicate there are differences in brain processing even after behavioral symptoms have been resolved. So there can be persistent brain disruptions even though there are no behavioral symptoms or brain abnormalities observable with anatomic neuroimaging methods.

Dr. Slotnick writes, “As mTBI patients may be more sensitive to repeated head trauma, it is arguable that they should not be allowed to continue participating in impact sports until their fMRI activity returns to normal.

There is also evidence that the magnitude of fMRI activity decreases in mTBI imagery with more severe or repeated head injuries. One working memory fMRI study had mTBI patients with more severe sports-related head injuries. These not-so-mild mTBI patients were tested 1 to 14 months after the most recent head injury. The large majority of participants had multiple previous concussions, and 15 of the 16 participants had persistent symptoms. As before, behavioral measures did not differ on the memory tasks between the mTBI patients and the control subjects. There was greater activity in the dorsolateral prefrontal cortex for the control participants than in mTBI patients, in direct opposition to the previous findings for less severe mTBI patients. Additionally, participants with greater post-concussive symptoms had a smaller magnitude and extent of firm activity within the dorsolateral prefrontal cortex during visual working memory blocks. The same pattern of fMRI results was obtained in a subsequent study that employed the identical visual working memory task and a similar group of not-so-mild mTBI participants. It is important to realized that repeated mTBI and sub-concussive head injuries ( due to boxing or football, for example) can lead to chronic traumatic encephalopathy (CTE).

There are eleven previous posts addressing chronic traumatic encephalopathy.

Memory and Other Cognitive Processes

September 20, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Memory is involved in all cognitive processes. Neuroscience is a new emerging, field and the research into other cognitive processes is just beginning. Much further research is needed before it is ready for public consumption.

The few definitive facts on this topic appear in the Chapter Summary, which follow:

“*Visual attention increases activity in visual sensory regions and is also associated with activity in dorsolateral prefrontal cortex and parietal cortex control regions.

Visual working memory is associated with the same sensory regions and control regions associated with attention, which likely reflects attention to the contents of working memory.

*Visual long-term memory is associated with the same regions associated with visual attention in addition to the medial temporal lobe, which indicates this cognitive priocess is distinct from attention.

*Imagery and working memory share the same cognitive operations and are associated with the same brain regions (i.e., the sensory cortex, the dorsolateral prefrontal cortex (i.e., Broca’s area) and the left posterior superior temporal cortex (i.e., Wernicke’s area).

*Memory for emotional information is thought to be enhanced through the interaction of the amygdala and the hippocampus.”

Motivated Forgetting

September 18, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Like retrieval-induced forgetting, motivated forgetting refers to an active process where retrieval of an item from memory is suppressed. Unlike retrieval-induced forgetting process, motivated forgetting is an intentional process.

So the research paradigm is obvious, present lists of words where words are designated to be remembered or forgotten. But the behavioral results of such an experiment would be obvious, and many would wonder why the study was done. Participants simply ignored the words designated to be forgotten and would study the words to be remembered.

Although a simple behavioral experiment would be silly, the same experiment measuring brain regions would be informative. The first study that investigated the brain regions associated with motivated forgetting employed fMRI. During the study phase, pairs of words were presented. During the think/no think phase, the initial words of some pairs were shown in red, which meant the associated word should not be thought about. The initial words of some pairs were shown in green, which meant that the associated word should be rehearsed. The initial words of some pairs were not shown, which served as a baseline measure of memory performance. During the final recall phase, all of the initial words pairs were shown.

The percentage of associated words recalled in the no-think condition was lower than the percentage of associated words recalled in the baseline condition, which reflected motivated forgetting. The percentage of associate words recalled in the think condition was higher than baseline performance, which was expected due to additional rehearsal.

Brain activity associated with motivated forgetting was identified by contrasting non-think trials (which were assisted with subsequent forgetting) and think trials (which were not associated with subsequent forgetting). Motivated forgetting was associated with an increase in activity within the dorsolateral prefrontal cortex and a decrease of activity in the hippocampus.

A literature review has shown that motivated forgetting consistently produces an increase in activity within the dorsolateral prefrontal cortex and a decrease of activity within the hippocampus. In addition, motivated forgetting of visual information produces a decrease in activity within the visual sensory regions. This overall pattern of brain activity during motivated forgetting is identical to that of retrieval-induced forgetting. These findings provide convergent evidence that active forgetting, whether retrieval-based or motivated, is cause by a top-down signal within the dorsolateral prefrontal cortex that inhibits the hippocampus and sensory cortical regions.

Retrieval-Induced Forgetting

September 17, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Retrieval-induced is an active process where retrieval of an item from memory inhibits the retrieval of related words. For example, if the word “banana” is recalled, the memory representation of the related word “orange,” which is also a fruit, will be inhibited to some degree. Presumably such inhibition occurs to reduce the likelihood that a similar but incorrect item will be retrieved (to avoid mistakenly saying “orange” when one intends to say “banana.”)

The paradigm used to study retrieval-induced forgetting includes an initial study phase, an intermediate retrieval practice, and a final recall phase. In one fMRI experiment, participants were presented with word pairs consisting of a category and an example of the category in the study phase. During the intermediate retrieval practice phase, participants were presented with a subset of the categories along with a two-letter word cue and were asked to mentally complete each word (during this phase, non-presented words from the same categories were inhibited). In the final recall phase, participants were presented with all of the categories and word cues corresponding to the word pairs from the study phase. Categories/words that were presented in the study phase but were not presented in the retrieval practice served as a baseline level of performance (since these words were not inhibited.) Retrieval-induced forgetting was revealed as a lower percentage of recall for words that were from the same category than the percentage of recall for words that were from a different category that were not presented during retrieval practice.

To identify brain regions associated with retrieval-induced forgetting during the final recall phase, non-presented words from the same category as those presented during retrieval practice (which were inhibited) were compared with practice words (which were not inhibited). This contrast produced activity in the dorsolateral prefrontal cortex. The larger the magnitude of activity in the dorsolateral prefrontal cortex, the higher the percentage of retrieval-induced forgetting. This suggests that the dorsolateral prefrontal cortex actively inhibits non-presented words from the same category as words presented during retrieval practice.

Another retrieval-induced forgetting study used transcranial direct current stimulation (tDCS) to disrupt activity in the right dorsolateral prefrontal cortex during the practice phase. This completely eliminated the retrieval-induced forgetting effect, indicating that the dorsolateral prefrontal cortex is necessary to produce this type of forgetting.

Sex Differences in Long Term Memory

September 13, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Males usually perform better on navigating previously learned environment. Females usually perform better on long-term memory tasks that can depend on verbal memory such as word list recognition and recall, associative memory, and autobiographical memory. Since almost all long-term memory tasks can be performed using verbal memory strategies, females generally have better behavioral performance than males. Females have larger numbers of estrogen receptors in the hippocampus and dorsolateral prefrontal cortex. These are two of the three regions associated with long-term memory, which can increase the activity of these regions. The hippocampus and the dorsolateral prefrontal cortex are larger in females than males, relative to overall brain size. Additionally, females have relatively larger volumes of language processing cortex, which likely contributes to their superior verbal memory.

In addition, females and males often employ different cognitive strategies and have distinct patterns of brain activity while they perform the same task. An fMRI study investigated whether there were sex differences in the hippocampus during memory for object-location associations. There were 10 female and 10 male participants. During study blocks, participants viewed a video as if they were walking through a virtual environment with five colored geometric objects. During recognition blocks, an aerial view of each object was shown in a old location or a new location. Participants responded whether each was in an “old” or “new” location. Each participant also used a four-point rating scale to describe the strategy they used to learn the object locations: (1) completely verbal, (2) more verbal than pictorial, (3) more pictorial than verbal, and (4) completely pictorial.

Although there was no difference in behavioral performance between female participants and male participants, the average strategy for female participants was 2.5 and the average strategy rating for male participants was 4.0 indicating that female participants employed more verbal memory strategies and male participants employed purely spatial/non-verbal strategies. The fMRI data indicated that activity was localized to the left hippocampus in the large majority of female participants and that activity was localize to the right hippocampus in the large majority of male participants. These results are consistent with patient studies indicating the lesions in the left medial temporal lobe impair verbal memory and lesions in the right medial temporal lobe impair visual memory.

Brain Regions Associated with Long-Term Memory

September 11, 2019

This post is based on an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Remember to consult the website http://www.brainfacts.org/
to see the anatomical information referred to in this post.

Dr. Slotnick writes, The term episodic memory can refer to many other related forms of memory including context memory, source memory, “remembering,” recollection, and autobiographical memory, which refers to a specific type of episodic memory for detailed personal events. As the names imply context memory and source memory refer to the context in which something occurred and source memory refers to where the event occurred.

Episodic memories are related to activity in both control regions and sensory regions of the brain. Sensory cortical activity reflects the contents of memory. The control regions that mediate episodic memory include the medial temporal lobe, the dorsolateral prefrontal cortex, and the parietal cortex. There are many regions associated with episodic memory but the primary regions are the medial temporal lobe, the dorsolateral prefrontal cortex, and the parietal cortex. The parahippocampal cortex processes the context of previously presented information such as the location or the color.

The hippocampus binds item information and context information to create a detailed episodic memory. Dr. Slotnick provides the following example. “If an individual went on a vacation to Newport Beach in California and later recalled meeting a friend on the beach, that individual’s perirhinal cortex would process item information (the friend), the parahippocampal cortex would process context information (the area of the beach on which they were standing), and the hippocampus would bind this information and context information into unified memory.”

Semantic memory refers to knowledge of facts that are learned through repeated exposure over a long period of time. These facts are processed and organized in semantic memory, which provides the basis for much thought. Subjectively, semantic memory is associated with “knowing.” Semantic memory includes definitions and conceptual knowledge, and this cognitive process is linked to the field of language.

Semantic memory has been associated with the left dorsolateral prefrontal cortex (in a different region associated with episodic memory), the anterior temporal lobes, and sensory cortical regions. The left dorsolateral prefrontal cortex may reflect the processing of selecting a semantic memory that is stored in other cortical memories. For example, naming animals activates more lateral inferior occipital-temporal cortex that has been associated with the perception of living things, while naming tools activates more medial inferior occipital-cortex that has been associated with perception of nonliving things.

In a study of Alzheimer’s patients, the impairment in an object naming task, which depends on intact semantic memory, was more highly correlated with cortical thinning in the left anterior temporal lobe. This finding suggests that the left anterior temporal lobe is necessary for semantic memory.

During long-term memory the hippocampus binds information between different cortical regions. But long-term memory may only depend on the hippocampus for a limited time. In the standard model of memory consolidation, a long-term memory representation changes from being based on hippocampal-cortical interactions to being based on cortical-cortical interaction, which takes a period of somewhere between 1 to 10 years. A person with hippocampal damage due to a temporary lack of oxygen might have impaired long-term memory for approximately 1 year before the time of damage from retrograde amnesia and have intact long-term memories for earlier events. This suggests that the hippocampus is involved in long-term memory retrieval for approximately 1year as more remote long-term memories no longer demand on the hippocampus so they are not disrupted.

The activity in the hippocampus did not drop to zero for older semantic memories but was well above baseline for events that were 30 years old. This indicates that the hippocampus was involved in memory retrieval for this entire period. If the hippocampus was no longer involved, the magnitude of activity in this regions would have dropped to zero for remote memories.

There is a growing body of evidence that the hippocampus is involved in long-term memories throughout the lifetime. As such, the process of consolidation does not appear to result in the complete transfer from hippocampus-cortical memory representation to cortical-cortical memory representations.

Brain Anatomy

September 8, 2019

The title of this post is identical to the title of a section in an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Brain Anatomy is a difficult topic to cover in a blog. The names can be learned and one can impress one’s friends and neighbors by reciting these names with their associated function. But the brain is a three dimensional structure and it is difficult illustrating these structures in two dimensions, especially since the position from which the brain is viewed is important. What is needed is a three dimensional model that can be rotated. Such a model can be found at http://www.brainfacts.org. Look for 3D Brain and click interact with the brain. It will likely take some practice interacting with the brain, but HM thinks this is the best source for this feature.

The brain is composed of four lobes: occipital, temporal, parietal, and frontal. Each lobe has gray matter on the surface, which primarily consists of cell bodies, and white matter below the surface, which primarily consists of cell axons that connect different cortical regions. The occipital lobe is associated with visual processing. The temporal lobe is associated with visual processing and language processing. The parietal lobe is associated with visual processing and attention, and the frontal lobe is associated with many cognitive processes. You can see that over half of the human brain is associated with visual processing. Obviously we are primarily visual animals.

The regions of the brain that are of relevance to memory include the occipital cortex, the temporal cortex, the parietal cortex, the dorsolateral prefrontal cortex, and the medial temporal lobe. The cortex is folded with gyri protruding out and sulk folding in.

The hippocampus (you can look for this using the link provided above) is a structure central to long-term memory. Its importance was realized when surgery was done on a patient, H.M., done to treat the severe epileptic seizures he was having. The medial temporal lobe, which contains the hippocampus, was removed in both hemispheres. This surgery did not affect his intelligence or personality, but it did cause a severe deficit in long-term memory referred to as amnesia. His semantic memory remained intact. He had almost no memory of events that occurred a few years before the surgery, and had no memory for events that occurred after the surgery. Ten months before the surgery he and his family moved to a new house a few blocks away from their old house. After the surgery he had no memory for his new address, he could not find his way to the new home, and he did not know where objects were kept in the new home. He had no memory of articles he had read before, so he would read the same articles repeatedly. He would eat lunch and a half-hour later could not remember he had eaten. Despite this severe deficit in long-term memory, his working memory appeared intact. He could remember a pair of words or a three-digit number for several minutes as long as he was not distracted. So a reasonable conclusion is that the hippocampus and the surrounding cortical regions are critical for long-term memory.

Dr. Slotnick writes, “Long-term memory typically refers to retrieval of previously presented information, However, the key stages of long-term memory include encoding, storage, and retrieval. The hippocampus has been associated with both long-term memory encoding and long-term memory retrieval. Long-term memory storage depends on a process called memory consolidation, which refers to changes in brain regions, including the hippocampus, underlying long-term memory. Thus, all three stages of long-term memory depend on the hippocampus.”

Sometimes people think of the hippocampus as being the location where long-term memories are stored. Memories are stored throughout the brain, it is the processing of these memories for which the hippocampus is critical.

Words With Friends

January 18, 2012

Alec Baldwin is responsible for a large amount of publicity going to the word game Words With Friends, www.wordswithfriends.com. So the Healthymemory Blog does not want to miss the opportunity to say that Words With Friends exemplifies both types of transactive memory, technical and human. As the Healthymemory Blog advocates both types of transactive memory for fostering both memory and brain health, it seems that a few words are in order given the opportunity that Alec Baldwin’s inappropriate behavior has afforded.

The game itself fosters vocabulary building, activates brain circuits searching through memory for appropriate words, as well as strategic thinking. All of which contribute to a healthy memory. Add to this the interaction with your fellow players that in itself is beneficial to a healthy memory.

It would be interesting to see brain imaging studies during the playing of Words with Friends. I would envision a large degree of activation of the hippocampus, the associative cortex, and the dorsolateral prefrontal cortex. The competitive aspect of the game might activate the amygdala. I would also wager that glucose metabolism would increase during the playing of the game, but would gradually decrease during the playing of the game as proficiency was gained.

It should be understood that this blog post in no way endorses the behavior of Alex Baldwin, and when the flight attendant tells you to shut down the game, shut down the game.

For readers who might not be so technologically oriented, I would suggest that an older form of technology, a scrabble board, would provide similar benefits.

© Douglas Griffith and healthymemory.wordpress.com, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

Improving Working Memory

January 15, 2012

As readers of the Healthymemory Blog well know, the primary constraint on cognitive performance is our limitation in working memory. The simplest way of thinking about working memory is that it is the information you can hold at one time. Phone numbers are a common example, although they are less relevant with today’s technology than they use to be. But suppose someone shouts out a phone number you want before you can get to your desk and either write it down or dial it. It is likely that you will need to keep rehearsing the number or it will be forgotten before you return to your desk. Phone numbers might appear to be trivial, but working memory limits the number of ideas you can keep active in your memory at one time. In other words, it limits the number of things that you can actively think about at the same time. Unfortunately, working memory is a function that tends to decline as we age. The dorsolateral prefrontal cortex is the physiological substrate where working memory takes place. It requires glucose to operate. As working memory improves, the rate of glucose metabolism decreases (that is, the dorsolateral prefrontal cortex functions more efficiently).

Given the importance of working memory, exercising it to improve its efficiency is highly recommended. Fortunately, there are exercises that do just that. Paul Verhaegen published a paper titled “A Working Memory Workout: How to Expand the Focus of Serial Attention from One to Four Items in 10 Hours or Less” published in the Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 30. no.6, 2004. Suppose you toss a handful of coins, somewhere between 10 and 15, and then count the number of pennies, nickels, dimes, and quarters. The easiest way to do this is to count each denomination before moving to the next. Unfortunately, this places minimal demands on working memory. If you want to expand your working memory, begin by tossing two denominations of coins. Rather than counting them systematically, count them randomly removing each coin as you count it. Here you need to keep a running count of each denomination in working memory. This should be easy, but do this until you can count each denomination without error. Then move on to three denominations. This will place much greater demands on working memory as you need to keep track of three tallies. Keep doing this until you can do it accurately consistently. This might take some time, multiple days, weeks even. When this is mastered move on to four denominations and keep working until you can keep count of four denominations accurately. This will probably take even more time. But once you reach this point you will have reached what is currently as the capacity of working memory, four items. You can be proud to have a highly efficient dorsolateral prefrontal cortex.

© Douglas Griffith and healthymemory.wordpress.com, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

How Using Mnemonic Techniques Exercises the Brain

December 18, 2011

The Healthymemory Blog has a category labeled “Mnemonic Techniques.” Not all of the posts in this category are strictly speaking mnemonic techniques. Posts on specific activities you can do to foster a healthy memory, meditation, for example, are also included here. But the mnemonic techniques specific to remembering specific items of information are touted as being doubly beneficial as they not only directly improve memory, but they also provide good mental exercise for the brain. Today’s post elaborates on how the different parts of the brain are exercised.

The first action that needs to be taken on information that you want to remember is to pay attention. Paying attention involves using working memory. This involves the dorsolateral prefrontal cortex. Maintaining information here requires glucose metabolism. The initially encoding is done in the hippocampi (there is one hippocampus in each of the two brain hemispheres) from which it is distributed throughout the rest of the brain. This distribution is needed to determine the meaning, or lack of meaning, of this information. Where there is meaning, this meaning is used to elaborate the meaning by relating it to other associations in the associative cortex. When there is little or no meaning, then the mnemonic provides a means of making the apparently meaningless information meaningful. This involves recoding, which involves the dorsolateral prefrontal cortex activating other associations found in the associative cortex. Often the technique involves the formation of a visual image which activates associative networks in both cerebral hemispheres via transmissions across the corpus callosum. There is no central memory center in the brain. Rather information is stored throughout the brain. Sensory information in the sensory portions, motor information in the motor portions, and verbal and semantic information is the associative portions. Information that you know well likely has many many links to other items of information, the job of the mnemonic technique is to establish solid new links to this new information you want to remember.

Mnemonic techniques require you to pay attention. Paying attention increases the glucose metabolism to the brain. This, in turn, activates the all important hippocampi and activates memory pathways throughout the associative and sensory cortices of the brain.

Click on the Category “Mnemonic Techniques” and you find a comprehensive listing of mnemonic techniques along with descriptions of the techniques and exercises. Try starting at the bottom of the category and proceeding up. There is a specific Healthymemory Blog post, “Memory Course”, which suggests an order in which the mnemonic techniques should be approached.

There are also some websites for learning and developing proficiency in mnemonic techniques. One is www.NeuroMod.org. Click on the Human Memory Site. Then click on the “read more” link under your preferred language. You can open up an account and record and track your progress. Another site is www.Thememorypage.net. Both of these websites are free.

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

Memory and Its Underlying Brain Structures

December 4, 2011

A variety of Healthymemory Blog posts have discussed the various brain structures underlying memory. As a book1 I have been reading has provided a succinct overview describing the interacting structures and areas of the brain that are responsible for memory I have decided to write the following post.

The initially encoding is done in the hippocampi (there is one hippocampus in each of the two brain hemispheres) from which it is distributed throughout the rest of the brain. This distribution is needed to determine the meaning, or lack of meaning, of this information. This takes place in short term or working memory. Meaningless information is quickly lost without further processing. Even the current instance of meaningful information will be lost without further processing (for example I need to meet Fred for lunch or I need to remember this for the examination). This working memory is maintained in an active mental state within the dorsolateral prefrontal cortex of the frontal lobes. Maintaining information here requires glucose metabolism.

This glucose metabolism is the physiological indication of paying attention. So when you are performing a task that requires you to pay attention, glucose metabolism is required. It is interesting to note that as you become more proficient in performing the task, the rate of glucose metabolism actually decreases. This indicates that you need to pay less attention due to your increase in proficiency.

The successful storing of information in long term memory via the hippocampi requires the establishing of links to other items in long term memory. Mnemonic techniques are developed to make what appears to be inherently meaningless into something meaningful so it can be linked to other items I long term memory for later retrieval. There is no central memory center in the brain. Rather information is stored throughout the brain. Sensory information in the sensory portions, motor information in the motor portions, and verbal and semantic information is the associative portions. Information that you know well likely has many many links to other items of information. Some memory theorists have likened human memory to a hologram. Holograms differ from photographs in that the entire image can be reconstructed from portions of the hologram. So if you break a hologram into two pieces, the entire hologram can be reconstructed from either piece, but the resulting image will be less distinct.

Memory theorists make a distinction between information being available in memory and information being accessible in memory. Information that can be readily retrieved is said to be accessible. However, if you cannot retrieve something at a given time, it is likely that that information is still not available in memory, but it is still accessible. Moreover, even after you have consciously given up trying to recall this information, it sometimes happens that at a later point in time when you are consciously thinking about something else, that this apparently lost memory pops into consciousness.

So how does this relate to maintaining and growing a healthy memory? Engaging in activities requiring significant amounts of attention increase the metabolic activity going to your working memory. This metabolic activity will decrease as you become more proficient in the activity. In many respects this is analogous to the effects of physical activity on cardiopulmonary activity. It should be noted that this practice effect is the result of transferring information to long term memory so less attention is required.

To maintain and grow long term memory developing new associative pathways throughout the brain is required. This will not be done by simply surfing the internet (which is primarily a working memory exercise). Long term memory growth is a matter of pursuing knowledge and skill in more depth to develop and strengthen associative pathways so that they are more resistant to forgetting. In other words, increasing the accessibility of the information. The very act of retrieving information is beneficial even if your initial retrieval attempts are unsuccessful. The searching for information activates memory pathways, some of which might have been long inactive. The memory search can reactivate them. Moreover, your memory will likely continuing working even after you have consciously given up the attempt.

1Restak, R., (2009). Think Smart: A Neuroscientist’s Prescription for Improving Brain Performance. New York: Riverhead Books.

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

More on the Dangers of Information Overload

March 9, 2011

I recently read another article on the dangers of information overload. In my view there cannot be too many articles on information overload as this is a serious problem. This Newsweek article1 is quite good. It reported the reseach of the Director of the Center for Neural Decision Making at Temple University, Angelika Dimoka, who employed brain imaging (fMRI) techniques to examine how the brain respond people are trying to make decisions when they are severely overtaxed. She found that activity in the dorsolateral prefrontal cortex, a region behind the forehead that is responsible for decision making and the control of emotions, suddenly fell off when the information load increased. It was similar to a circuit breaker popping. Now activity in the parts of the brain registering emotional activity, the parts of the brain normally kept in check by the dorsolateral prefrontal cortex, ran wild. So the research participants made stupid decisions and their anxiety levels soared.

The article also points out that this concern with information overload is not new. Leibniz bemoaned the “horrible mass of books which keeps on growing,” in the 17th Century. In 1729 Alexander Pope warned of “a deluge of authors covering the land.” But the problem today is many, many orders of magnitude larger, both respect to the amount of information and the rapidity with which it arrives.

The article notes that one reason for this limitation is the limited capacity of short-term memory. One way of looking at short-term memory is the number of items that we can attend to at one time. Here is where the Magic Number 7 Plus or Minus Two, created comes in. Actually subsequent research has indicated that the true magic number might be 5 or even lower. An important factor is the nature of the items to be remembered. It is prudent that you do not consider more options at a time than is warranted by your magic number. So if more items need to be evaluated, it is good to evaluate them in groups, with run-offs, if necessary.

Another ramification of this limitation in short-term memory is that recency trumps quality. So there is the risk of a poorer choice being made simply due to the order in which the options were considered. So in addition to considering options in groups, also consider the order in which the option was considered.

When the number of options is large, it is good to resort to transactive memory. That is, write things down, use a spreadsheet, whatever. Try to develop a systematic scoring system to evaluate options.

The Newsweek also mentions the neglected unconscious. Provide sufficient time to allow your unconscious mind to work for you. The article presents evidence supporting the benefits of unconscious processing. Also remember that making the optimal decision is often not realistic. Be satisfied with satisficing, the process identified by the Nobel Lauerate Herbert Simon. Be satasified with considering enough information to assure yourself that the decision is satisfactory and should not lead to disappointment.

1Begley, S. (2011). I Can’t Think. Newsweek, March 7, 28-33.

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