Institutionen för kvinnors och barns hälsa / Department of Women's and Children's Health
Abstract
Training of working memory (WM) is a research field that could result in
new therapeutic breakthroughs for people with impaired WM functions. In
support of this view, research in our group has previously shown that WM
training could increase WM capacity in children with attention deficits
and in healthy adults. Apart from that study, there had been no previous
literature on WM training presenting clear evidence for a clinically
relevant change on WM capacity or brain activity following WM training.
Study II and III were designed to investigate these issues.
Only a few previous studies have investigated the development of brain
activity related to WM. The results from those previous studies indicate
that the development of WM is related to changes in activity in the
frontal and parietal cortex. The aim of the developmental studies in this
thesis (Study I and IV) was to extend those previous findings using two
new approaches: 1) integration of data on brain function and brain
structure and 2) investigation of a critical WM function i.e. the ability
to ignore distraction.
Previous research in our group showed that increased brain activity in
prefrontal and parietal areas underlie the development of WM. In Study I,
we sought to investigate how this development is related to the
development of brain connectivity. Our aim was to present a network of
brain structure and function underlying development of WM, which has
previously never been shown. Consistently, the results from Study I
showed that development of WM was related to a frontoparietal network of
brain regions where brain activity and connectivity showed a similar
developmental trend.
The published research on brain activity related to training of WM is
very scarce. Therefore, Study II aimed at investigating the long-term
effects of WM training on brain activity using a training paradigm that
was designed to optimise the training effects for each individual. For
the first time we were able to show that training of a cognitive
function, WM, could result in changes in brain activity in the adult
human brain in task-related areas.
In Study III the aim was to establish whether WM training could result in
clinically relevant effects on performance and behaviour such that it
could be used as a new therapy for groups of people with attention
deficits. The resulting analyses included data from 44 children,
diagnosed with ADHD, who had participated in a five week WM training
program. Performance on executive functions, including WM, and
behavioural ratings of ADHD symptoms, improved significantly as an effect
of WM training.
In Study IV we investigated the development of brain activity related to
the ability to ignore distraction. This ability is central to WM since
distracting stimuli must be ignored in order to keep information in WM.
There is no previous published research on the neural mechanisms
underlying the development of this important ability. The unravelling of
those mechanisms would add to the understanding of the neurobiology
related to disorders affecting attention and impulsivity, in addition to
increasing our knowledge about WM functions. Furthermore, Study IV was
designed to analyse developmental changes in brain activity related to
each phase of a WM task. Importantly, we found that development of WM was
related to increased brain activity in frontal and parietal areas during
maintenance of information in WM. The ability to ignore distraction was
related to brain activity in the prefrontal cortex in adults. In children
another part of the prefrontal cortex was related to the presence of
distraction and this area corresponded to the area where information was
maintained.
To conclude, this thesis demonstrates previously unknown data on the
capacity of the human brain in relation to the healthy and deficient WM
system and identifies brain areas that are crucial for the development of
this system