Preparation Lecture 6
Bettcher (2016). Neuroanatomical substrates of executive functions – prefrontal
Executive functions (EF) -> reflect a constellation of higher order cognitive processes that are
markedly vulnerable to the aging process. EF are often characterized as “frontal lobe tasks”.
Frontal lobe hypothesis/frontal hypothesis of aging -> posits that aging is characterized by
decrements in executive functions and speed of processing, and this negative trajectory systems from
structural changes in the prefrontal cortex. There is a relationship between poor executive functions
and both smaller prefrontal grey matter volume and worse matter integrity, suggesting that the selective
vulnerability of this domain is driven at least in part by frontal lobe changes.
Purpose study -> to assess whether prefrontal grey matter volumes independently predict executive
function performance when statistically differentiated from global atrophy and individual non-frontal
lobar volume contributions. There were three hypotheses:
1. Prefrontal volumes independently predict executive functions, even after accounting for global
atrophy and temporal/parietal contributions.
2. Global brain atrophy, as indexed by total volume, is a more robust predictor of executive functions
than individual lobar volume contributions.
3. Fronto-parietal white matter microstructure, as indexed by diffusion tensor imaging fractional
anisotropy, independently predicts executive functions, even after accounting for global grey
matter atrophy.
Material and methods
A sample of 202 neurologically healthy, older adult participants was selected. Participants were
administered different executive functioning tests: set-shifting, number-letter, and design fluency
(mental set shifting), enclosed flanker test, antisaccade task, and Stroop inhibition (inhibition), dot
counting, running letter memory, N-back 1 and 2, and digit span backwards (updating/working
memory). They also tested processing speed.
Results
- Executive function measurement model -> speech was highly correlated with shifting/inhibition.
- Analysis 1: executive function and lobar grey matter volumes -> frontal, temporal, parietal, and
occipital lobar volumes were associated with updating/working memory, shifting/inhibition, and
speed, and there was no clear difference in strength of effects associated with different lobes.
Frontal grey matter was related to all three executive and speed variables, but this was not the
strongest effect for any variable.
- Analysis 2: executive function and lobar grey matter independent of global atrophy -> global grey
matter was related to updating/working memory, shifting/inhibition, and speed. Temporal grey
matter was independently related to updating/working memory and occipital grey matter to
shifting/inhibition. Age effects were significant for shifting/inhibition and speed factors, and
approached significance for working memory.
1
, - Analysis 3: cingulum FA made significant contributions to all variables and corpus callosum FA
was related to shifting/inhibition and speed. In a final model, global grey matter made a strong
contribution to updating/working memory, global grey matter and corpus callosum FA both had
notable effects on shifting/inhibition, and corpus callosum FA was strongly related to speed.
Discussion
The findings suggest that while prefrontal grey matter volumes are significantly associated with
executive functions, they do not independently predict executive function when statistically isolated
from global atrophy. Thus, global atrophy was the major, independent predictor of executive functions
when considering the simultaneous role of individual lobar and global grey matter volumes. Study
results suggest that higher corpus callosum and cingulate (dorsal) FA predicted better executive
functions, independent of global matter atrophy.
Literature suggests that a dorsal fronto-parietal network of gray and white matter regions is important,
if not keystone structures for these higher order processes. Results from this study highlight that while
prefrontal lobe volumes are unsurprisingly associated with executive functions, they cannot be viewed
in isolation from more distributed volume effects in a healthy older adult cohort. The findings suggest
that sequestering prefrontal contribution to executive functions from other brain regions may obscure
and oversimplify important brain-behavior relationships.
Furthermore, results suggested that cortical grey matter makes a strong contribution to
updating/working memory, cortical grey matter and corpus callosum FA both contribute to
shifting/inhibition, and corpus callosum FA displays strong associations with speed. Study results
provide evidence for a critical, albeit distributed role of both grey and white matter structures in
supporting the broad construct of executive functions.
Age -> study results indicate that age did not have a substantive effect on the observed relationships
between shifting/inhibition, updating/working memory, speed and global grey matter volume, but did
attenuate the effect size of the associations.
In sum -> 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, particularly the corpus callosum,
continued to predict executive functions after accounting for global grey matter atrophy.
Burgess (2007). Fifty years of prefrontal cortex research – assessment
What did we already know 50 years ago?
The history of test development created two problems for the development of psychometric tests to
measure the symptoms of frontal lobe dysfunction:
1. The main concern of the early theorists was to measure intelligence. The object that was the focus
of the psychometric theorists seemed tangential to the characterization of the symptoms of frontal
lobe damaged patients.
2. The intelligence theorist empathized the psychometric properties of their tests such as internal
consistency and test-retest reliability.
2
Bettcher (2016). Neuroanatomical substrates of executive functions – prefrontal
Executive functions (EF) -> reflect a constellation of higher order cognitive processes that are
markedly vulnerable to the aging process. EF are often characterized as “frontal lobe tasks”.
Frontal lobe hypothesis/frontal hypothesis of aging -> posits that aging is characterized by
decrements in executive functions and speed of processing, and this negative trajectory systems from
structural changes in the prefrontal cortex. There is a relationship between poor executive functions
and both smaller prefrontal grey matter volume and worse matter integrity, suggesting that the selective
vulnerability of this domain is driven at least in part by frontal lobe changes.
Purpose study -> to assess whether prefrontal grey matter volumes independently predict executive
function performance when statistically differentiated from global atrophy and individual non-frontal
lobar volume contributions. There were three hypotheses:
1. Prefrontal volumes independently predict executive functions, even after accounting for global
atrophy and temporal/parietal contributions.
2. Global brain atrophy, as indexed by total volume, is a more robust predictor of executive functions
than individual lobar volume contributions.
3. Fronto-parietal white matter microstructure, as indexed by diffusion tensor imaging fractional
anisotropy, independently predicts executive functions, even after accounting for global grey
matter atrophy.
Material and methods
A sample of 202 neurologically healthy, older adult participants was selected. Participants were
administered different executive functioning tests: set-shifting, number-letter, and design fluency
(mental set shifting), enclosed flanker test, antisaccade task, and Stroop inhibition (inhibition), dot
counting, running letter memory, N-back 1 and 2, and digit span backwards (updating/working
memory). They also tested processing speed.
Results
- Executive function measurement model -> speech was highly correlated with shifting/inhibition.
- Analysis 1: executive function and lobar grey matter volumes -> frontal, temporal, parietal, and
occipital lobar volumes were associated with updating/working memory, shifting/inhibition, and
speed, and there was no clear difference in strength of effects associated with different lobes.
Frontal grey matter was related to all three executive and speed variables, but this was not the
strongest effect for any variable.
- Analysis 2: executive function and lobar grey matter independent of global atrophy -> global grey
matter was related to updating/working memory, shifting/inhibition, and speed. Temporal grey
matter was independently related to updating/working memory and occipital grey matter to
shifting/inhibition. Age effects were significant for shifting/inhibition and speed factors, and
approached significance for working memory.
1
, - Analysis 3: cingulum FA made significant contributions to all variables and corpus callosum FA
was related to shifting/inhibition and speed. In a final model, global grey matter made a strong
contribution to updating/working memory, global grey matter and corpus callosum FA both had
notable effects on shifting/inhibition, and corpus callosum FA was strongly related to speed.
Discussion
The findings suggest that while prefrontal grey matter volumes are significantly associated with
executive functions, they do not independently predict executive function when statistically isolated
from global atrophy. Thus, global atrophy was the major, independent predictor of executive functions
when considering the simultaneous role of individual lobar and global grey matter volumes. Study
results suggest that higher corpus callosum and cingulate (dorsal) FA predicted better executive
functions, independent of global matter atrophy.
Literature suggests that a dorsal fronto-parietal network of gray and white matter regions is important,
if not keystone structures for these higher order processes. Results from this study highlight that while
prefrontal lobe volumes are unsurprisingly associated with executive functions, they cannot be viewed
in isolation from more distributed volume effects in a healthy older adult cohort. The findings suggest
that sequestering prefrontal contribution to executive functions from other brain regions may obscure
and oversimplify important brain-behavior relationships.
Furthermore, results suggested that cortical grey matter makes a strong contribution to
updating/working memory, cortical grey matter and corpus callosum FA both contribute to
shifting/inhibition, and corpus callosum FA displays strong associations with speed. Study results
provide evidence for a critical, albeit distributed role of both grey and white matter structures in
supporting the broad construct of executive functions.
Age -> study results indicate that age did not have a substantive effect on the observed relationships
between shifting/inhibition, updating/working memory, speed and global grey matter volume, but did
attenuate the effect size of the associations.
In sum -> 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, particularly the corpus callosum,
continued to predict executive functions after accounting for global grey matter atrophy.
Burgess (2007). Fifty years of prefrontal cortex research – assessment
What did we already know 50 years ago?
The history of test development created two problems for the development of psychometric tests to
measure the symptoms of frontal lobe dysfunction:
1. The main concern of the early theorists was to measure intelligence. The object that was the focus
of the psychometric theorists seemed tangential to the characterization of the symptoms of frontal
lobe damaged patients.
2. The intelligence theorist empathized the psychometric properties of their tests such as internal
consistency and test-retest reliability.
2
