Summary of the articles for the course
Neurocognition
Table of content:
Week 1 - Development page 2 - 13
Week 2 - Genes and pharmacology page 13 - 28
Week 3 - Memory page 28 - 32
Week 4 - Emotion and motivation page 33 - 39
Week 5 - Attention page 39 - 41
Week 6 - Executive functions page 41 - 48
Week 7 - Motor control page 48 - 54
Week 8 - Interpretation of test results page 54 - 60
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,Week 1 - Development
Article: T
he aging mind: Neuroplasticity in response to cognitive training
Authors: Park & Bischof
Published: 2013
Introduction
Neuroplasticity is the brain’s ability to increase capacity in response to sustained experience. In order to
improve cognitive functioning in the aging brain, the brain must have plasticity. Most studies focus on proving
that cognitive training improves cognitive function. However, most cognitive functions show a natural
age-related decline (even in highly educated people). Thus the focus should not only be on improving cognitive
function, but also on slowing cognitive aging. It is estimated that the onset of Alzheimer’s disease (AD) could be
postponed by approximately five years by successful training, resulting in a 50% decrease in AD diagnoses.
Reserve is essentially an increased supply of neural resources created as a result of experiences, whereas
neural compensation is the ability to draw more effectively and efficiently on networks.
Theories
Baltes and Baltes proposed “reserve capacity”: the idea that older adults are able to maintain cognitive function
by using resources to ‘neutralize’ aging effects. For working memory and episodic encoding, it was shown that
there was increased contralateral hemispheric recruitment as a form of compensation.
The scaffolding theory of aging and cognition (STAC) states that cognitive function is a balance between the
magnitude of neural insults that the brain has sustained and the compensatory neural activities (=scaffolding).
“Scaffolding” is the recruitment of additional brain circuitry to support failing/inefficient brain circuitries.
Effective compensatory activation in response to this degradation mitigates age-related decline in cognition.
The use of training/exercise might enhance the scaffolding, to further protect cognitive functioning. See the
model on the next page.
The cognitive reserve model proposes that there are specific experiences/behaviors that provide protection
from age-related decline (e.g., education, engaging work, an active lifestyle). However, the causal component of
this theory remains unclear.
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,Will the brain improve by experience?
Stroke patients with significant damage can show dramatic recovery: this proves the plasticity that even older
brains can have. New parts of the brain take over functions that were performed by damaged brain areas. Two
important side notes on this:
- Stroke patients receive a lot of therapy and the regained function will be continuously trained because
the patient will use the functions in daily life.
- In stroke patients, a part of the brain is shut down and no longer used for any function. It might be that
this extreme condition will allow more plasticity than the brain would under normal conditions.
The potential of brain reorganization does occur even in late adulthood. Nevertheless, the conditions under
which healthy older brains reorganize in an adaptive matter to enhance cognitive function are poorly
understood.
Plasticity will only manifest itself if the person experiences substantial and sustained demands on their
cognitive function. Plasticity will occur when the existing abilities and task demands do not meet. There are
individual differences in when something is considered cognitively challenging. Novelty has an important
influence on plasticity.
What constitutes change?
Increases in neural volume
- Sedentary older adults who did aerobic exercise, showed delay shrinkage in the prefrontal cortex, an
area maximally sensitive to age-related volumetric shrinkage.
- Older adults that were trained to juggle for 90 days showed increased neural volume in the mid
temporal regions, hippocampus and nucleus accumbens. However, this effect was not maintained after
90 days of non-juggling.
- Older men who played a demanding spatial navigational game every other day for 4 months exhibited
stability of hippocampal volume over a 4-month period, whereas control subjects declined.
However, evidence that training will improve neural volume is sparse. Most improvements require maintained
training to maintain the improvements. It is unknown if maintained training should remain challenging or if a
basic level of training would suffice.
Changes in neural activity
New regions can be activated or known regions can be more/less activated. Noack and colleagues argue that
changes in neural activity might be the result of switching strategies rather than plasticity and a change in the
neurocognitive system.
There is evidence that training will increase neural efficiency and thus decrease neural activation on the trained
task. However, there is also evidence that suggests that e nhanced n
eural activity is facilitative for old adults.
Conclusion: The neurological literature on cognitive training is at an early stage, and results are varied and
actually quite limited. It is difficult to predict whether training will increase or decrease neural activity, and how it
might interact with age, as well as how durable effects are over time. It also is surprisingly difficult to assess
whether any observed brain changes reflect a fundamental increase in neural capacity or merely a change in
strategy.
Near versus far transfer
There is evidence that older adults can show training improvements that are still visible even years later.
However, there is little evidence that training induces a fundamental change in processes that transfer to
unrelated tasks in everyday life (=far transfer). Recent work shows provocative evidence for far transfer from
training on a working memory task to improvement in general intelligence; young adults who improved on a
n-back training task showed an increase in general measures of fluid intelligence. A study by Dahlin et al.
investigated far transfer in young and old adults. Young adults showed transfer (and improved striatal function)
and old adults did not show transfer (and showed no striatal activity). Thus, it seems as the striatal function was
trained in young adults and this was transferred to other striatum-based tests; this is evidence that a neural
process (rather than a task) was trained.
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,Maintenance of gains
There are many studies that found that gains from cognitive training in older adults lasted from 3 m months to 5
years. There is some evidence for far transfer from language training to memory tasks in older adults, but the
findings are somewhat inconsistent across studies.
Overall, there is a growing body of evidence suggesting that training gains can be maintained for long periods
on the originally trained task, but that transfer effects are not easily demonstrated, particularly in older adults.
Engagement as a cognitive intervention
There is evidence that a high level of education and an active lifestyle will protect against neurocognitive aging.
However, these epidemiological studies are primarily correlational and the direction of the correlation is not
entirely clear. Although much more experimental work is needed on the issue of engagement, there is a small
but promising body of literature which suggests that modest amount of cognitive gains can be realized by
engagement in tasks that demand sustained cognitive effort. A benefit of socially engaging tasks (as opposed
to (computer-based) cognitive tasks) is that it not only might protect cognitive function, but will also help the
older adult meet psychological needs for social interactions and purpose in life.
Chapter 5: The brain
Authors: Baars & Gage
Published: 2010
The brain anatomy is not a static and settled field; knowledge of the brain is constantly expanding. The brain
has developed and changed through time and so some areas of the brain are ‘older’ than others. The cortex or
neocortex represents recent brain developments in the human.
The nervous system
The nervous system consists of the central nervous system (CNS; brain+spinal cord) and the peripheral nervous
system (PNS; the autonomic and peripheral sensory and motor system). This chapter will focus on 2 sensory
systems (vision and hearing) and two output systems (speech and hand-arm control), because these have been
studied the most.
The geography of the brain
The two hemispheres are entirely separate and joined through the corpus callosum. Each hemisphere consists
of 4 lobes:
Finding your way in the brain:
- Some gyri (grooves) and sulci (‘hills’) in the brain are seen as ‘landmarks’ of the brain; to divide the brain
into separate areas.
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,- The Brodmann areas are based on small regional differences in cells and groups of cells are clustered
into Brodmann areas with unique numbers (about 100). These areas correspond well to different
specialized functions of the cortex, such as the visual and auditory areas, motor cortex, and areas
involved in language and cognition.
- The Talairach coordinates have a 3D zero point (x=0, y=0, z=0) and the three dimensions can be used to
specify any point in the brain precisely.
- The upper direction of the human brain is both called ‘dorsal’, meaning ‘toward the back’ and also
‘superior’, meaning ‘upward’.
- ‘Ventral’ means ‘toward the belly’ and ‘inferior’ means ‘downward’.
The cortex is vital for cognitive functions and constantly interacts with other regions.
The cortex and the thalamus show the closest connections: the t halamo-cortical system
handles signal traffic. The outer sheet of the cortex is called the gray matter (cell
bodies) and the white matter (axons with myelin) of the cortex fills the large cortical
hemispheres. The cortex can be h orizontally divided into layers. T
he neocortex consists
of six layers, older regions of the cortex (referred to as ‘paleocortex’) have five cortical
layers. The layer most close to the skull is layer I; largely consisting of dendrites forming
a woven sheet, also called ‘feltwork’. The cortex is v ertically organized in ‘cortical
columns’. Columns can be clustered in hypercolumns.
Picture on the left: here you can see the 6 cortical layers and 3 columns.
Growing a brain from the bottom up
The brain grows and evolved from the inside out. Lower regions (e.g., the brainstem,
with basic survival functions) are generally more ancient than higher regions. We will
start with the older regions and work our way up:
- The brainstem is continuous with the spinal cord and controls some basic
functions (breathing/heart rate). Its upper section, the pons, has nerve fibers that
connect the two halves of the cerebellum.
- The 2 thalami (a thalamus in both hemispheres!) form the upper end of the
brainstem.
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, - The hypothalamus is located in front of and below each thalamus. It is connected to the pituitary gland.
Many physiological homeostasis are monitored by the hypothalamus. It also has crucial emotional
functions.
- On top of each hypothalamus is a hippocampus, nestled inside the temporal lobe. Plays a role in
transferring experiential information to longer-term memory, retrieving episodic memories and spatial
navigation.
- Near the hippocampi are the amygdalae; important in emotions and emotional association.
- The four ventricles are cavities with CSF. It is part of a circulatory system that descends into the spinal
cord through the ‘aquaduct’.
- There is one basal ganglia outside each thalamus.
- A shield-like structure (putamen) has an outward tube looping around (caudate nucleus) is important for
control of movement and cognition.
Some regions (like the hippocampi and olfactory surface) can replace their cells. Up till recently, scientists
thought that that was not possible.
The functional roles of brain regions
The cerebral hemispheres
The hemispheres are divided by the longitudinal fissure. The corpus callosum is a large arch of white matter
that provides a link between the two hemispheres to integrate information from both sides. Many aspects of
sensory and motor processing entail the crossing over of input (sensory) or output (motor) information from the
left side to the right, and vice versa. Only the olfactory nerve stays on the same side of the brain on its way to
the cortex. Callosotomy (complete slicing of the corpus callosum) was used to improve uncontrollable epilepsy.
Nowadays, callosectomy (a partial cut) is preferred.
Synesthesia is the fusion of different sense experiences: stimulation of one sense triggers an experience in a
different sense. Synesthesia seems to be the result of increased crosstalk among sensory areas in the brain.
Back and front of the brain
The back of the brain (parietal, occipital and temporal lobe) are responsible for processing sensory information
and associative processes. The frontal lobe is responsible for motor - or output - responses. The frontal cortex
is also involved in action control, planning, some working memory functions and language production. In the
somatosensory cortex and motor cortex, different regions of the body are not equally represented, which can be
shown in a map (or “homunculus”):
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