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.

•

Global atrophy was the only independent predictor of EF.

•

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

•

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.

More research support for the P-FIT neuro-model of intelligence (Gf and Gwm)

Another study, with an excellent integration of other research, supporting the parietal-frontal integration (P-FIT) neuro-model of intelligence, specifically the networks involvement in fluid reasoning (Gf) and working memory capacity (Gwm), but not Gs.  Click here for prior P-FIT related posts.  The amount of research providing some support for the P-FIT model can not be ignored.

Click on images to enlarge

The Complexity of the Frontal Lobes

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

Dorsolateral PreFrontal Cortex fun educational video rap

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

Neural efficiency, executive function and intelligence (g, IQ): An embarrasment of riches

I give up. I don't have the time, or maybe the neural efficiency, to read, digest, integrate, and summarize a wave of recent research articles dealing with the concept of neural efficiency (oscillations) and intelligence. That being said, I'm simply going to post the references and abstracts. Maybe an interested IQ's Corner blog reader would be interested in reading these articles and attempting to summarize (via a guest blog post)...something I had hoped to do.

When less is more and when more is more: The mediating roles of capacity and speed in brain-behavior efficiency (Bart Rypma and Vivek Prabhakaran). Intelligence 37 (2009) 207–22.

An enduring enterprise of experimental psychology has been to account for individual differences in human performance. Recent advances in neuroimaging have permitted testing of hypotheses regarding the neural bases of individual differences but this burgeoning literature has been characterized by inconsistent results. We argue that careful design and analysis of neuroimaging studies is required to separate individual differences in processing capacity from individual differences in processing speed to account for these differences in the literature. We utilized task designs which permitted separation of processing capacity influences on brainbehavior relationships from those related to processing speed. In one set of studies, participants performed verbal delayed-recognition tasks during blocked and event-related fMRI scanning. The results indicated that those participants with greater working memory (WM) capacity showed greater prefrontal cortical activity, strategically capitalized on the additional processing time available in the delay period, and evinced faster WM-retrieval rates than low-capacity participants. In another study, participants performed a digit-symbol substitution task (DSST) designed to minimize WM storage capacity requirements and maximize processing speed requirements during fMRI scanning. In some prefrontal cortical (PFC) brain regions, participants with faster processing speed showed less PFC activity than slower

Neuroanatomical correlates of intelligence (Eileen Luders, Katherine L. Narr, Paul M. Thompson and Arthur W. Toga). Intelligence 37 (2009) 156–163.

With the advancement of image acquisition and analysis methods in recent decades, unique opportunities have emerged to study the neuroanatomical correlates of intelligence. Traditional approaches examining global measures have been complemented by insights from more regional analyses based on pre-defined areas. Newer state-of-the-art approaches have further enhanced our ability to localize the presence of correlations between cerebral characteristics and intelligence with high anatomic precision. These in vivo assessments have confirmed mainly positive correlations, suggesting that optimally increased brain regions are associated with better cognitive performance. Findings further suggest that the models proposed to explain the anatomical substrates of intelligence should address contributions from not only (pre)frontal regions, but also widely distributed networks throughout the whole brain.

Exploring possible neural mechanisms of intelligence differences using processing speed and working memory tasks: An fMRI study (Gordon D. Waiter, Ian J. Deary, Roger T. Staff, Alison D. Murray, Helen C. Fox, John M. Starr and Lawrence J. Whalley). Intelligence 37 (2009) 199–206

To explore the possible neural foundations of individual differences in intelligence test scores, we examined the associations between Raven's Matrices scores and two tasks that were administered in a functional magnetic resonance imaging (fMRI) setting. The two tasks were an n-back working memory (N = 37) task and inspection time (N = 47). The subjects were members of the Aberdeen Birth Cohort 1936, aged in their mid–late 60s when tested for this study. Performance on both tasks was correlated significantly with scores on Raven's Matrices. In the inspection time task there were regions with significant correlations between the neural activity (BOLD response) and performance but not between BOLD response and scores on Raven's Matrices. In the working memory task there were no significant correlations between BOLD response and either performance or scores on Raven's Matrices. Moreover, there was almost no mediation of the Raven's Matrices versus n-back and inspection time scores correlations by the respective BOLD response. These findings partially replicate important aspects of a prominent report in this field [Gray, J.R., Chabris, C.F., & Braver, T.S. (2003). Neural mechanisms of general fluid intelligence. Nature Neuroscience, 6, 316–322.], but have also extended the those finding into both a unique population and a novel functional task.

Intelligence and neural efficiency: Measures of brain activation versus measures of functional connectivity in the brain (Aljoscha C. Neubauer and Andreas Fink). Intelligence 37 (2009) 223–229

The neural efficiency hypothesis of intelligence suggests a more efficient use of the cortex (or even the brain) in brighter as compared to less intelligent individuals. This has been shown in a series of studies employing different neurophysiological measurement methods and a broad range of different cognitive task demands. However, most of the studies dealing with the brain–IQ relationship used parameters of absolute or relative brain activation such as the eventrelated (de-)synchronization of EEG alpha activity, allowing for interpretations in terms of more or less brain activation when individuals are confronted with cognitively demanding tasks. In order to investigate the neural efficiency hypothesis more thoroughly, we also used measures that inform us about functional connectivity between different brain areas (or functional coupling, respectively) when engaged in cognitive task performance. Analyses reveal evidence that higher intelligence is associated with a lower brain activation (or a lower ERD, respectively) and a stronger phase locking between short-distant regions of the frontal cortex.

Gray matter and intelligence factors: Is there a neuro-g? (Richard J. Haier, Roberto Colom, David H. Schroeder, Christopher A. Condon, Cheuk Tang, Emily Eaves and Kevin Head). Intelligence 37 (2009) 136–144

Heterogeneous results among neuro-imaging studies using psychometric intelligence measures may result from the variety of tests used. The g-factor may provide a common metric across studies. Here we derived a g-factor from a battery of eight cognitive tests completed by 6929 young adults, 40 of whom also completed structural MRI scans. Regional gray matter (GM) was determined using voxel-based-morphometry (VBM) and correlated to g-scores. Results showed correlations distributed throughout the brain, but there was limited overlap with brain areas identified in a similar study that used a different battery of tests to derive g-scores. Comparable spatial scores (with g variance removed) also were derived from both batteries, and there was considerable overlap in brain areas where GM was correlated to the respective spatial scores. The results indicate that g-scores derived from different test batteries do not necessarily have equivalent neuro-anatomical substrates, suggesting that identifying a “neurog” will be difficult. The neuro-anatomical substrate of a spatial factor, however, appears more consistent and implicates a distributed network of brain areas that may be involved with spatial ability. Future imaging studies directed at identifying the neural basis of intelligence may benefit from usinga psychometric test battery chosen with specific criteria.

Intergenerational transmission of neuropsychological executive functioning ("Jennifer M. Jester, Joel T. Nigg, Leon I. Puttler, Jeffrey C. Long, Hiram E. Fitzgerald and Robert A. Zucker"). Brain and Cognition 70 (2009) 145–153

Relationships between parent and child executive functioning were examined, controlling for the critical potential confound of IQ, in a family study involving 434 children (130 girls and 304 boys) and 376 parents from 204 community recruited families at high risk for the development of substance use disorder. Structural equation modeling found evidence of separate executive functioning and intelligence (IQ) latent variables. Mother’s and father’s executive functioning were associated with child’s executive functioning (beta = 0.34 for father–child and 0.51 for mother–child), independently of parental IQ, which as expected was associated with child’s IQ (beta = 0.52 for father–child and 0.54 for mother–child). Familial correlations also showed a significant relationship of executive functioning between parents and offspring. These findings clarify that key elements of the executive functioning construct are reliably differentiable from IQ, and are transmitted in families. This work supports the utility of the construct of executive function in further study of the mechanisms and etiology of externalizing psychopathologies.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, IQ, intelligence, cognition, g, general intelligence, neural efficiency, neural oscillations

WCST: Does it really measure frontal lobe executive functions?

Does the WCST measure executive functioning? There is little doubt that the WCST is one of the predominant tests used in neuropsychological assessment to assess executive functions. However, studies have recently questioned the validity of drawing inferences about the site of executive functions (the frontal lobes of the brain) from performance on the WCST. The following "in press" article, which presents a nice review of the literature, suggests that in it's current administration formats the WCST is not the sensitive measure of frontal lobe executive functioning as is often thought. Below I present the abstract, a few select passages, and the primary conclusion from this excellent review article.

Nyhus, E., & Barceló, F. (in press). The Wisconsin Card Sorting Test and the cognitive assessment of prefrontal executive functions: A critical update. Brain and Cogntion.

Abstract

For over four decades the Wisconsin Card Sorting Test (WCST) has been one of the most distinctive tests of prefrontal function. Clinical research and recent brain imaging have brought into question the validity and specificity of this test as a marker of frontal dysfunction. Clinical studies with neurological patients have confirmed that, in its traditional form, the WCST fails to discriminate between frontal and non-frontal lesions. In addition, functional brain imaging studies show rapid and widespread activation across frontal and non-frontal brain regions during WCST performance. These studies suggest that the concept of an anatomically pure test of prefrontal function is not only empirically unattainable, but also theoretically inaccurate. The aim of the present review is to examine the causes of these criticisms and to resolve them by incorporating new methodological and conceptual advances in order to improve the construct validity of WCST scores and their relationship to prefrontal executive functions. We conclude that these objectives can be achieved by drawing on theory-guided experimental design, and on precise spatial and temporal sampling of brain activity, and then exemplify this using an integrative model of prefrontal function [i.e., Miller, E. K. (2000). The prefrontal cortex and cognitive control. Nature Reviews Neuroscience, 1, 59–65.] combined with the formal information theoretical approach to cognitive control [Koechlin, E., & Summerfield, C. (2007). An information theoretical approach to prefrontal executive function. Trends in Cognitive Sciences, 11, 229–235.].

According to the authors, there are at least two different systems of administration and scoring of the WCST. There is the "standard version by Grant and Berg (1948) with Milner´s (1963) correction criteria and the shortened version by Heaton (Heaton, 1981; Heaton, Chelune, Talley, Kay, & Curtis, 1993 ). Furthermore, the test has been administered in modified versions by Nelson (1976), Delis, Squire, Bihrle, and Massman (1992), and Barceló (1999, 2003)."

In the conventional administration:

the WCST consists of four key cards and 128 response cards with geometric figures that vary according to three perceptual dimensions (color, form, or number). The task requires subjects to find the correct classification principle by trial and error and examiner feedback. Once the subject chooses the correct rule they must maintain this sorting principle (or set) across changing stimulus conditions while ignoring the other – now irrelevant – stimulus dimensions. After ten consecutive correct matches, the classification principle changes without warning, demanding a flexible shift in set. The WCST is not timed and sorting continues until all cards are sorted or a maximum of six correct sorting criteria have been reached.

Conclusions

The present interest in prefrontal cortex function has renewed the use of the WCST in clinical and experimental settings. However, much criticism has questioned the utility of this test as a marker of prefrontal function. A critical review of clinical studies suggests that the original WCST does not distinguish between frontal and non-frontal lesions. Likewise, functional neuroimaging studies confirm that delivery of negative feedback during WCST rule transitions activates a widespread network of frontal and non-frontal regions within a split-second time scale. New methodological and conceptual advances from theory-guided experimental designs, precise spatial and temporal sampling of brain activity, and modern integrative models of prefrontal function (Miller, 2000) combined with a formal information theoretical approach to cognitive control (Koechlin & Summerfield, 2007) can improve our understanding of the WCST and its relationship to prefrontal executive functions. These advances suggest that simple modifications of the original version of the WCST may offer more valid and reliable measures of key component operations, such as the maintenance, shifting, and updating of task-set information over trials. Fast brain imaging techniques help us put into perspective the specificity of the test as a marker of prefrontal function as a key node within the widely distributed and tightly interconnected neural networks subserving human cognition.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, clinical psychology, intelliigence, cognition, executive functions, frontal lobes, Brain and Cognition, IQs Corner

Functional Impulsivity

Interesting research spotlight at the MIND BLOG

http://mindblog.dericbownds.net/2008/11/innovative-brain.html

Sent from KMcGrew iPhone (IQMobile)

Tic toc brain clock: More on temporal g

More research suggestive of temporal g. Check it out at IQ's Corner sister blog (The IQ Brain Clock).

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, IQ, intelligence, temporal g, temporal processing, IQ Brain Clock, prefrontal lobes

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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D-KEFS executive function battery information

No doubt about it. The area of executive function is hot in cognitive psychology and intellectual/neuropsychological assessment. One of the more frequent paths to the IQ Corner blog are people doing web searches for EF instruments, often the Delis-Kaplan Executive Function System (D-KEFS) battery.

I've never administered (nor do I own) a copy of the D-KEFS. However, I have posted information regarding D-KEFS research "as is"...without comment (since I've not done my homework with the battery). This is one of these posts. I just ran across a 2005 review of the D-KEFS in the Journal of Clinical and Experimental Neuropsychology (click here to view). In addition, I've made two prior posts re: the D-KEFS.

Enjoy.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, executive function, D-KEFS, intelligence, frontal lobe, IQ

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Cognitive construct of attention - a review

The most recent Annual Review of Psychology had a nice overview article (by Posner and Rothbart..click here to view) dealing with research on the cognitive construct of attention. I found Figure 2 and Table 1 (above) particularly informative. Below are some key quotes from the article. Given my prior reading and posts regarding the importance of executive attention, I was particularly interested in Posner and Rothbart's suggestion that executive attention may be a domain general learning mechanism that may be trainable. The italics and/or underlining below were added by this blogmaster.

• In recent years, attention has been one of the fastest growing of all fields within cognitive psychology and cognitive neuroscience.
• Certainly many, perhaps even most, imaging studies have been concerned with anatomical issues. As Figure 2 illustrates, several functions of attention have been shown to involve specific anatomical areas that carry out important functions.
• Imaging data have supported the presence of three networks related to different aspects of attention (Fan et al. 2005). These networks carry out the functions of alerting, orienting, and executive attention (Posner & Fan 2007). A summary of the anatomy and chemical modulators involved in the three networks is shown in Table 1. Alerting is defined as achieving and maintaining a state of high sensitivity to incoming stimuli; orienting is the selection of information from sensory input; and executive attention involves mechanisms for monitoring and resolving conflict among thoughts, feelings, and responses.
• ..we have argued that the executive attention network is involved in self-regulation of positive and negative affect as well as a wide variety of cognitive tasks underlying intelligence (Duncan et al. 2000). This idea suggests an important role for attention in moderating the activity of sensory, cognitive, and emotional systems.
• There is considerable evidence that the executive attention network is of great importance in the acquisition of school subjects such as literacy (McCandliss et al. 2003) and in a wide variety of other subjects that draw upon general intelligence (Duncan et al.2000).
• It has been widely believed by psychologists that training involves only specific domains, and that more general training of the mind, for example, by formal disciplines like mathematics or Latin, does not generalize beyond the specific domain trained (Thorndike 1903, Simon 1969). However, attention may be an exception to this idea. Attention involves specific brain mechanisms, as we have seen, but its function is to influence the operation of other brain networks (Posner & Rothbart 2007). Anatomically, the network involving resolution of conflict overlaps with brain areas related to general intelligence (Duncan et al. 2000). Training of attention either explicitly or implicitly is sometimes a part of the school curriculum (Posner&Rothbart 2007), but additional studies are needed to determine exactly how and when attention training can best be accomplished and its long-lasting importance.
• Executive attention represents a neurodevelopmental process in children and adolescents, the alteration which could affect the propensity for the development of a number of disorders.

Technorati Tags: psychology, educational psychology, neuropsychology, neuroscience, intelligence, IQ, cognition, executive attention, attention, domain general, learning, education, ADHD

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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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Human Front Lobes book - 2nd edition

FYI. I just received an email notification of the publication of the 2nd Edition of "The Human Frontal Lobes." I've not read this book...it is on my list to check out. This is just a "pass-along" FYI.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, frontal lobes, neurology, intelligence, cognition, executive function

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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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Excercise your frontal and parietal lobes

Interesting (and fun) post at SharpBrains re: an activity to exercise your frontal and parietal lobes...supposedly to improve attentionial processes


Technorati Tags: psychology, educational psychology, neuropsychology, brain, mental excercise, frontal lobes, parietal lobes, brain excercise, intelligence, attention, cognition, cognitive, BrainShape

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