Research Byte: Executive functions are related to more than just the prefrontal strucutres--white matter matters

Neuroanatomical Substrates of Executive Functions: Beyond Prefrontal Structures

• Brianne M. Bettcher^{a, b, ,} ,
• Dan Mungas^c,
• Nihar Patel^a,
• Jonathan Elofson^a,
• Shubir Dutt^a,
• Matthew Wynn^a,
• Christa L. Watson^a,
• Melanie Stephens^a,
• Christine M. Walsh^a,
• Joel H. Kramer^a

• ^a University of California, San Francisco; Department of Neurology, Memory and Aging Center; San Francisco, CA
• ^b University of Colorado, Denver Anschutz School of Medicine; Departments of Neurosurgery and Neurology; Rocky Mountain Alzheimer’s Disease Center; Aurora, CO
• ^c University of California, Davis; Department of Neurology; Davis, CA

Received 6 August 2015, Revised 29 February 2016, Accepted 3 March 2016, Available online 3 March 2016

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Highlights

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Executive functions (EF) are not synonymous with ‘frontal’ tasks.

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Global atrophy was the only independent predictor of EF.

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Frontal volumes do not predict EF when statistically isolated from global atrophy.

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White matter metrics remain predictors of EF, independent of global atrophy.

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Abstract

Executive functions are often considered lynchpin “frontal lobe tasks”, despite accumulating evidence that a broad network of anterior and posterior brain structures supports them. Using a latent variable modeling approach, we assessed whether prefrontal grey matter volumes independently predict executive function performance when statistically differentiated from global atrophy and individual non-frontal lobar volume contributions. We further examined whether fronto-parietal white matter microstructure underlies and independently contributes to executive functions. We developed a latent variable model to decompose lobar grey matter volumes into a global grey matter factor and specific lobar volumes (i.e. prefrontal, parietal, temporal, occipital) that were independent of global grey matter. We then added mean fractional anisotropy (FA) for the superior longitudinal fasciculus (dorsal portion), corpus callosum, and cingulum bundle (dorsal portion) to models that included grey matter volumes related to cognitive variables in previous analyses. Results suggested that the 2-factor model (shifting/inhibition, updating/working memory) plus an information processing speed factor best explained our executive function data in a sample of 202 community dwelling older adults, and was selected as the base measurement model for further analyses. Global grey matter was related to the executive function and speed variables in all four lobar models, but independent contributions of the frontal lobes were not significant. In contrast, when assessing the effect of white matter microstructure, cingulum FA made significant independent contributions to all three executive function and speed variables and corpus callosum FA was independently related to shifting/inhibition and speed. Findings from the current study indicate that while prefrontal grey matter volumes are significantly associated with cognitive neuroscience measures of shifting/inhibition and working memory in healthy older adults, they do not independently predict executive function when statistically isolated from global atrophy and individual non-frontal lobar volume contributions. In contrast, better microstructure of fronto-parietal white matter, namely the corpus callosum and cingulum, continued to predict executive functions after accounting for global grey matter atrophy. These findings contribute to a growing literature suggesting that prefrontal contributions to executive functions cannot be viewed in isolation from more distributed grey and white matter effects in a healthy older adult cohort.

The Complexity of the Frontal Lobes

http://jonlieffmd.com/blog/the-complexity-of-the-frontal-lobes

Another article implicating dlPFC and P-FIT model of intelligence--Importance to general intelligence

Another study implicating dorsolateral prefrontal cortex (dlPFC) and PFIT model of intelligence with regard to general intelligence (g), working memory and white matter tract-moderated functional brain network connectivity. Supports significant components of the three-level explanatory model articulated in MindHub Pub #2.

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Dorsolateral PreFrontal Cortex fun educational video rap

DorsoLateral PreFrontal CortexTechnorati Tags: neuroscience, neuropsychology, prefrontal cortex, executive functions, dorsolateral prefrontal cortext, DLPFC, DLPFC rap

The Cognitive Atlas Project - way cool stuff

Very intriguing article and description of the Cognitive Atlas Project, a scientific social collaborative knowledge project.









Poldrack, R. A. (2010). Mapping Mental Function to Brain Structure: How Can Cognitive Neuroimaging Succeed? Perspectives on Psychological Science, 5(6), 753-761

Abstract

The goal of cognitive neuroscience is to identify the mapping between brain function and mental processing. In this article, I examine the strategies that have been used to identify such mappings and argue that they may be fundamentally unable to identify selective structure–function mappings. To understand the functional anatomy of mental processes, it will be necessary for researchers to move from the brain-mapping strategies that the field has employed toward a search for selective associations. This will require a greater focus on the structure of cognitive processes, which can be achieved through the development of formal ontologies that describe the structure of mental processes. In this article, I outline the Cognitive Atlas Project, which is developing such ontologies, and show how this knowledge could be used in conjunction with data-mining approaches to more directly relate mental processes and brain function.










The article , with annotations, is available here, as part of this blogs IQ's Reading feature.



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intelligence IQ tests IQ testing IQ scores CHC intelligence theory CHC theory Cattell-Horn-Carroll human cognitive abilities psychology school psychology individual differences cognitive psychology neuropsychology psychology special education educational psychology psychometrics psychological assessment psychological measurement IQs Corner neuroscience Cognitive Atlas Project

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Older brains distracted not slower

From Scientific American

http://www.sciam.com/article.cfm?id=brains-more-distracted

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Intellectual performance and executive function

I just made a post re: an excellent overview article dealing with the theoretical/research literature over at IQ's Corner sister blog - the IQ Brain Clock. Check it out.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, intelligence, cognition, IQ, prefrontal cortext, dorsolateral prefrontal lobes, temporal processing, mental time keeping, IQ Brain Clock, conative, self-regulated learning

WJ III measures of RAN?, speed of lexical access, executive functions?

When time permits, I've been carefully skimming the approx. 30 CHC/WJ III dissertations that I recently acquired and noted at this blog. When I've discovered something of potential importance, I've made DD (Dissertation Dish) posts (all DD-related posts can be found by clicking on the "dissertation" keyword in this blogs index--scroll down left-side of blog).

I just finished skimming a dissertation by one of Dawn Flanagan's students (Kyvelos, 2003). Kyvelos reanalyzed (via CFA) the speeded tests from the WJ III/CAS validity sample (155 elementary school-age subjecxts) which was the foundation of Keith et al.'s CHC-based WJ III/CAS SPR article (2001). At variance from the SPR publication was the inclusion of the WJ III Retrieval Fluency and Rapid Picture Naming Speed tests in the analysis. These tests were NOT included in the Keith et al. 2001 formal publication.

[Conflict of interest note - I'm a coauthor of the WJ III battery]

Although no support was found for the classification of the WJ III and/or CAS speeded tests at the narrow (stratum I) ability level, the analysis did support the validity of separate broad Gs and Glr factors, factors with a latent factor correlation of .74. What I find particularly interesting was the validity for a rate-based Glr factor, which was defined by the following significant loadings:

• WJ III Retrieval Fluency = .69
• WJ III Rapid Picture Naming = .56
• CAS Expressive Attention = .30

In contrast, all other WJ III (Decision Speed, Cross Out, Visual Matching) and CAS speeded tests (Receptive Attention, Planned Connections, Planned Codes, Number Detection, Matching Numbers) all loaded on the broad Gs factor.

Why is this interesting?

First, the most robust post-WJ III publication structural finding I've discovered (in various unpublished analyses I've conducted with the WJ III data files) is the finding that the WJ III Rapid Picture Naming (measures the ability to rapidly identify and orally name pictures of common objects) and Retrieval Fluency (measures fluency in retrieving the names of objects.. the subject is asked to state as many items as they can of three different types) tests "hang together." These two tests seem to be tapping a rate retrieval (Glr) ability distinct from traditional Gs tests. As reported in the broad+narrow CFA in WJ III technical manual, we did specify these two tests to represent the narrow ability of "Naming Facility" under Glr.

• NA- Ability to rapidly produce accepted names for concepts or things when presented with the thing itself or a picture of it (or cued in some other appropriate way). The naming responses must be in an individuals long-term memory store (i.e., objects or things to be named have names that are very familiar to the individual). In contemporary reading research is ability is called rapid automatic naming (RAN)

That is...evidence was presented in the WJ III TM that these two tests measure the rate aspect (versus the "level" aspect) of Glr. I've repeatedly found these tests grouping together in various exploratory factor analyses, multidimensional scaling analysis, cluster analysis, etc. The Kyvelos (2003) study supports this finding. I've speculated that the common ability is "speed of lexical access"....which I first ran across in Perfetti's reading research.

Second, the other test that loaded on this rate Glr factor was the CAS Expressive Attention test. This task is based on the classic Stroop task (1935) that is typically interpreted as a valid measure of interference, inhibition/disinhibition, and executive control. In this task a subject must name as fast as possible (when presented with printed words in different colored fonts) the color in which the words red, blue, yellow, and green, are printed instead of reading the words themselves. Clearly such a task requires response inhibition and rapid/fluent accessing of a person's lexicon (speed of lexical access).

Bottom line - I believe, based both on published and unpublished research, that the combination of the WJ III Retrieval Fluency and Rapid Picture Naming tests measure some sort of Glr fluency/rate ability, especially as it relates to speed of semantic processing or speed of accessing one's lexicon. The association of these two WJ III tests with a CAS Stroop-like task (Expressive Attention) also suggests that response inhibition is a potentially important component for successful performance on these two WJ III tests. In other words, these two WJ III tests may measure, aside from speed of lexical access or word retrieval fluency (possibly some shared abilities with RAN tasks?), aspects of executive functioning - namely, ability to deal with interference effects and response inhibition.

RE: possible WJ III measures of executive functioning, check out recent posts re: the WJ III Pair Cancellation test.

Technorati Tags: psychology, school psychology, educational psychology, neuropsychology, intelligence, IQ, IQ test, intelligence quotient, CAS, WJ III, Woodocck-Johnson, executive function, inhibition, Gs, Glr, CHC, CHC theory

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WJ III Pair Cancellation - Part 2

More on the WJ III Pair Cancellation test (click here for prior post). I just finished skimming Carper's (2003) dissertation (comparing relations between select NEPSY and WJ III tests). I thought Carper's task analysis description of abilities measured by the WJ III Pair Cancellation test was informative. Carper included the following under Pair Cancellation: Visual scanning, Response inhibition, Interference control, Sequencing, Speed and Fluency, Sustained Attention, Processing Speed, and Motoric Speed

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, intelligence, IQ test, IQ scores, intelligent quotient, cancellation test, Pair Cancellation, WJ III, executive function, attention, concentration, vigilance, CHC, CHC theory

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Vigilance tasks/tests meta-search

I've added my 3rd IQ's Corner web meta-search link to the appropriate section of this blog (scroll down left side of blog to the "Meta-web searches" section). The topic is cancellation tasks/tests....a test format used primarily in neuropsychology settings to assess vigilance (a component of executive function).

Can frontal brain age-related atrophy increase gambling, depression and prejudice?

Another nice research summary in one of my favorite journals for quick contemporary research updates....Current Directions in Psychological Science. von Hippel (2007) presents a summary that suggests that age-related atrophy of the brains frontal lobes (which is the primary seat of executive functions), which can produce increased disinhibition in behavior, might be causative variables in increased prejudice, gambling, and depression in the elderly.


Technorati Tags: psychology, school psychology, educational psychology, neuropsychology, neuroscience, aging, developmental, executive functions, inhibition, gambling, prejudice, depression.Stroop test

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Random tidbits from the mind blogosphere - 9-6-07

• Thanks to the Brain Injury blog for the sad news re: evidence of extensive brain damage to WWE wrestler Benoit.
• Check out ENL for a post re: thinking abilities (and prefrontal cortex activity) and dyslexia
• Gene Expression adds more to the never-ending discussion of the Flynn Effect (click here and here)
• Positive Technology Journal has a brief post on a small study investigating the relationship between visual and motor imagery
  

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, brain injury, dyslexia, reading, Flynn Effect, Gv, imagery

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Brain damage can make you smarter?

Interesting post on the ever great DI blog on a recent study that suggests that brain injury to the prefrontal cortex might actually help with certain kinds of problem solving.

Now...this does not mean you should run out and bang the front of your head on a brick wall.

Technorati Tags: psychology, educational psychology, neuropsychology, neuroscience, intelligence, cognition, IQ, prefrontal cortext, executive function, brain injury

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Planning ability post at DI blog

Check out an interesting post re: the neural substrates of planning ability (part of the executive function system) at the always interesting Developing Intelligence blog.

Technorati Tags: psychology, educational psychology, neuroscience, neuropsychology, planning, executive function, cognition, intelligence

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Asperger's and executive functioning

I ran across an interesting small-sample (but well controlled with subject matching) study in the recent issue of Neuropsychologia re: possible impairments in executive processes/function (EF) in adults with Asperger's Syndrome. The article presents a nice summary (in table form) of prior matched-control studies that have examined the performance of individuals with Asperger's on many classic executive function measures (e.g., Wisconsin Cart Sort Test; Delis-Kaplan).

The most important finding from this study is the possibility that specific EF deficits (viz., response initiation and intentionality, in particular the ability to engage and disengage actions in the service of overarching goals),may be associated with Asperger's, but this may not have emerged in prior research that has used traditional EF measures. IN particular, the authors identify two less frequently used EF measures (Behavioral Assessment of Dysexecutive Syndrome, BADS; Hayling Test) as being potentially important for clinicians to evaluate for possible diagnostic use.

• Hill, E. Bird, C. (2006) Executive processes in Asperger syndrome: Patterns of performance in a multiple case series Neuropsychologia,44, 2822–2835 (click here to view)
  

Abstract

• Mixed evidence exists for executive dysfunction in autism spectrum disorders (ASD). This may be because of the nature of the tasks used, the heterogeneity of participants, and difficulties with recruiting appropriate control groups. A comprehensive battery of ‘executive’ tests was administered to 22 individuals with Asperger syndrome and 22 well-matched controls. Performance was analysed both between groups and on an individual basis to identify outliers in both the ASD and control groups. There were no differences between the groups on all ‘classical’ tests of executive function. However, differences were found on newer tests of executive function. Specifically, deficits in planning, abstract problem solving and especially multitasking. On the tests that discriminated the groups, all of the ASD individuals except one were identified as significantly impaired (i.e. below the 5th percentile of the control mean) on at least one executive measure. This study provides evidence for significant executive dysfunction in Asperger syndrome. Greatest dysfunction appeared in response initiation and intentionality at the highest level—the ability to engage and disengage actions in the service of overarching goals. These deficits are best observed through using more recent, ecologically valid tests of executive dysfunction. Moreover, performance on these measures correlated with autistic symptomatology.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, Aspergers, autism, intelligence, IQ, executive system, executive function, Wisconsin Card Sort Test, WCST, Delis-Kaplan, BADS, Hayling test

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Random tidbits from mind blogsphere 1-10-07

• Developing Intelligence continues its excellent streak of neuroscience posts. Today dealt with the possible functional organization of the prefrontal cortex...that part of the brain integral to executive functions
• Yippeeeee!!!!!!!! Another report (at Happy Neuron) that suggests coffee may be beneficial to my brain health. This is one of the few vices I have left. I'm pumped. I think I'll go get a triple shot.
• Check out Mind Hacks for information on "neural time travel."
• More on memory improvement methods at Sharp Brains.

Technorati Tags: psychology, educational psychology, neuropsychology, neuroscience, blogsphere, mind, executive function, brain fitness, prefrontal cortex, coffee, caffeine, intelligence, cognition

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Developmental aspects of planning ability - Wisconsin Card Sort

The Eide Neurolearning blog just made a post commenting/summarizing a recent article that studied the performance of children on the Wisconsin Cart Sort test, an established test of planning (part of executive function).

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, Wisconsin Cart Sort, WCST, planning ability, executive function, intelligence, cognition


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Age decline in reasoning - speed and executive abilities

[Double click on table to enlarge for easier viewing]

What may be the reasons for decreased fluid intelligence (Gf) with increasing age?

According to recent study (see reference and abstract below),two of the primary causative factors for decreased fluid intelligence (as established by recent research) are (a) decreased speed of cognitive processing (a generalized cognitive slowing mechanism) and (b) decreases in the executive functions of the frontal lobes as evidenced by decreased frontal lobe volume, alterations in frontal lobel cell morphology, and reductions in cerebral blood flow to the frontal and prefrontal brain lobes. The current study investigated the relative contributions of processing speed and frontal lobe function on decreases in Gf. The abstract for the article (together with URL link) is reproduced below. I will summarize some of the major findings plus add my two cents.

I have 2 cents worth of methodological comments. First, measures of reaction time (Gt) operationally defined cognitive processing speed in this study. According to the CHC taxonomy, these measures represent aspects of the broad domain of Gt (broad reaction time), which is NOT to be confused with broad cognitive processing speed (Gs). Thus, the current results are specific to the influence of Gt and may not be generalizable to Gs abilities. Additional research with valid Gs markers is needed.

Second, the authors continue the unfortunate tradition of using the Wechsler Block Design test as a marker for Gf. Contemporary Gf-Gc/CHC joint exploratory and confirmatory factor studies have convincly indicated that Block Design is a strong measure of visual-spatial processing (Gv)...not Gf. Luckily, the authors also use the Wechsler Matrix Reasoning test which is a valid indicator of Gf. Given the problems with Block Design, I recommend that readers of this article only pay attention to the results focused on understanding the decline in the Matrix Reasoning test (Of course, the Block Design findings can be interpreted in the context of Gv if that is what is of interest.)

Given this caveat, below are the major conclusions regarding possible explanations for age-related declines in Gf. I believe readers should only focus on the composite Gt measure as the indicator of general reaction time (Gt) and only the analyses that included the Gt, frontal function measures, and age in the analysis (as these provide the most valid and comprehensive explanations from the current study). These findings have been highlighted in red in the above table picture.

• Frontal (executive) function and Gt, collectively, account for approximately 27 % of the decrease in Gf with age. Chronological age explains and additional 15-16 % of the decline in Gf, above and beyond frontal function and Gt abilities.

• As noted by the authors, a generalized slowing of cognitive speed contributes to decreased Gf abilities...but, speed is not the entire picture. Decreased frontal functions, as well as other unaccounted for variables realated to age, also contribute to decreased Gf with age. Decreased frontal functions and Gt both contribute uniquely to age-related declines in Gf abilities.

• Declines in cognitive abilities, in this case Gf, are multiply determined. No one single mechanism can explain age-related changes in cognitive ability.

• Bottom line - age-related decreases in the ability to reason inductively/deductively and solve novel problems (Gf - fluid intelligence) appear due, in part, to age-related decreased speed of cognitive thinking and decreases in ability to think and manage (executive function) one's own thinking processes ("thinking about thinking"), plus additional factors not clearly delineated.
  

Bugg, J., Zook, N., DeLosh, E., Davalos, D. & Hasker, D, (2006). Age differences in fluid intelligence: Contributions of general slowing and frontal decline. Brain and Cognition, 62, 9–16 (click here to view)

Abstract

• The current study examined the contributions of general slowing and frontal decline to age differences in fluid intelligence. Participants aged 20–89 years completed Block Design, Matrix Reasoning, simple reaction time, choice reaction time, Wisconsin Card Sorting, and Tower of London tasks. Age-related declines in fluid intelligence, speed of processing, and frontal function were observed. Hierarchical regression analyses showed that the processing speed and frontal function measures accounted for significant variance in fluid intelligence performance, but there was also a residual effect of age after controlling for each variable individually as well as both variables. An additional analysis showed that the variance in fluid intelligence that was attributable to processing speed was not fully shared with the variance attributable to frontal function. These findings suggest that the age-related decline in fluid intelligence is due to general slowing and frontal decline, as well as other unidentified factors.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, aging, developmental, fluid intelligence, Gf, visual-spatial, Gv, frontal lobes, executive function, intelligence, IQ scores, cognition

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Do the sexes use different brain areas when "planning"?

Mixing Memory has a VERY interesting post regarding recent studies of possible gender differences in "planning" ability (part of executive functioning), as measured by the classic Tower of London task. MM's post speaks for itself. Of particular interest are findings suggesting no manifest performance difference between genders, BUT, significant differences in the areas of the brain's used (based on fMRI analyses). Check it out

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, brain, fMRI, planning, executive function, Tower of London, intelligence, cognition, cognitive, gender differences

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On Intelligence: Hawkins HTM computational theory

I LOVE blogging.

Two days ago I made the FYI post "Brain boss (prefrontal cortext) acts in step-wsie manner?" Shortly thereafter, someone posted a "comment" suggesting a link between the sequential step-wise hypothesized functioning of the prefrontal cortex and Hawkin's (2005) Hierarchical Temporal Memory (HTM) computational theory of intellectual functioning (as outlined in his book "On Intelligence"). I had never heard of this book or theory.

What I find intriguing is the fact that Hawkins is no minor player on the modern technology stage. He is well known for a number of activities--namely, he has founded founded three companies: Palm Computing (who has not heard of Palm Pilots?), Handspring, and Numenta, and the non-profit Redwood Neuroscience Institute, a scientific research institute focused on understanding how the human neocortex works.

The typical reader of IQs Corner may be wondering why someone with his background is now dabbling in understanding human intelligence. I wondered this myself. The answer lies in the Prologue to On Intelligence. A portion is reproduced below.

Maybe some readers of IQs Corner will explore this area in greater detail

• You may be wondering why a computer designer is writing a book about brains. Or put another way, if I love brains why didn't I make a career in brain science or in artificial intelligence? The answer is I tried to, several times, but I refused to study the problem of intelligence as others have before me. I believe the best way to solve this problem is to use the detailed biology of the brain as a constraint and as a guide, yet think about intelligence as a computational problem—a position somewhere between biology and computer science. Many biologists tend to reject or ignore the idea of thinking of the brain in computational terms, and computer scientists often don't believe they have anything to learn from biology. Also, the world of science is less accepting of risk than the world of business. In technology businesses, a person who pursues a new idea with a reasoned approach can enhance his or her career regardless of whether that particular idea turns out to be successful. Many successful entrepreneurs achieved success only after earlier failures. But in academia, a couple of years spent pursuing a new idea that does not work out can permanently ruin a young career. So I pursued the two passions in my life simultaneously, believing that success in industry would help me achieve success in understanding the brain. I needed the financial resources to pursue the science I wanted, and I needed to learn how to affect change in the world, how to sell new ideas, all of which I hoped to get from working in Silicon Valley.
• In August 2002 I started a research center, the Redwood Neuroscience Institute (RNI), dedicated to brain theory. There are many neuroscience centers in the world, but no others are dedicated to finding an overall theoretical understanding of the neocortex—the part of the human brain responsible for intelligence. That is all we study at RNI. In many ways, RNI is like a start-up company. We are pursuing a dream that some people think is unattainable, but we are lucky to have a great group of people, and our efforts are starting to bear fruit.
• The agenda for this book is ambitious. It describes a comprehensive theory of how the brain works. It describes what intelligence is and how your brain creates it

Technorati Tags: psychology, educational psychology, neuropsychology, neuroscience, computational models, intelligence, IQ, cognition, cognitive, HTM, hierarchical temporal theory, On Intelligence, Jeff Hawkins, Numenta, Handspring, Redwood Neuroscience Institute, prefrontal cortext, brain, IQs Corner

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