Christopher Benwell – David Fleming Brown Travel
Scholarship Report 2015
Research visit: Berenson-Allen Centre for Non-invasive Brain
Stimulation, Harvard University, Boston
About me:
I am a final-year Scottish PhD student based within the Institute of Neuroscience and
Psychology at the University of Glasgow, where I am studying the functional and
structural architecture of the visuo-spatial attention system in the human brain under
the supervision of Professor Gregor Thut and Dr Monika Harvey. My PhD research
has involved a combination of psychophysical measurements, EEG recordings and
non-invasive brain stimulation in healthy participants. Using these methods, I have
identified neurophysiological correlates of trait-like lateralised perceptual bias
(‘pseudoneglect’), with the majority of participants showing a bias for stimuli
presented in the left visual field. Additionally, using bilateral transcranial direct
current stimulation (tDCS) applied to the posterior parietal cortex, I have found that
this perceptual bias can be manipulated under specific stimulation and task
conditions.
Why did you apply for the David Fleming-Brown Scholarship?
An important open question with regard to my PhD research to date, and in cognitive
neuroscience and neuropsychology in general, is how brain stimulation modulates
ongoing neural activity in order to influence perception/behaviour. Thus, an exciting
approach for answering this question is to combine neurophysiological measurement
(such as EEG) with brain stimulation in order to obtain a real time measure of
changes in brain activity associated with brain stimulation. This is a field of research I
am particularly interested in pursuing, both for my current research interests and for
my future career. Being one of the leading centres for non-invasive brain stimulation
in the world, The Berenson-Allen Centre for Non-invasive Brain Stimulation within
Beth Israel Deaconess Medical Centre in Boston, a teaching hospital associated with
Harvard University, appeared to be the ideal place to learn the technical
specifications and cutting edge analysis methods required to successfully combine
brain stimulation and EEG, due to the world-leading resources, technology and
expertise on offer there. I was fortunate enough to be accepted for a six month lab
visit by the director of the centre, Dr Alvaro Pascual-Leone, who is one of the
foremost brain stimulation researchers in the world. Therefore, the funding
contributed to by the David Fleming-Brown Travel Scholarship offered me the
opportunity to undertake a six month lab visit in one of the most prestigious brain
stimulation labs in the world.
Details of my visit:
I spent six months working within the Berenson-Allen Centre for Non-invasive brain
Stimulation. The visit proved hugely enjoyable for me both personally and
professionally. The main motivation for my visit was to learn analysis techniques for
combined brain stimulation/electroencephalography (EEG) datasets, as well as how
to successfully record such data. To this end, I was provided access to a large
quantity of previously collected but unanalysed EEG datasets from various
transcranial magnetic stimulation (TMS)/EEG studies. I also assisted with several
experimental set-ups and sessions, thereby gaining valuable practical experience. I
have pre-processed and performed statistics on datasets from diabetic patients,
Alzheimer’s patients, young healthy participants and elderly healthy participants. The
aim of the ongoing research is to investigate differences in the neural response to
non-invasive brain stimulation between these patient groups and healthy controls.
This is interesting both for pure research and for clinical purposes, as non-invasive
brain stimulation offers the potential for rehabilitation of pathological brain function.
To do so, I used a combination of Matlab codes written by researchers within the
centre, and my own custom written codes to analyse the EEG data. The data show
overall differences in the relative and absolute power of diabetic and Alzheimer’s
patients as compared to healthy controls, and differences in how the brains of
diabetic and Alzheimer’s patients, relative to healthy controls, respond to intermittent
theta burst stimulation (iTBS), an excitatory TMS protocol. So far we have only
analysed resting state EEG data within the time/frequency domain. We are in the
process of performing an analysis on single pulse TMS-evoked potentials post-iTBS
which may reveal additional information over and above that which we have already
found. It is likely that this project will result in at least two publications (one as first
author).
Impact of the David Fleming-Brown Scholarship
I learned a huge amount regarding brain stimulation and EEG analysis during my
visit from the researchers at the Berenson-Allen Centre. I worked as part of an EEG
team with weekly meetings and seminars, as well as participating in regular one on
one session’s with Mouhsin Shafi who is an expert in TMS/EEG analysis. This
provided me with invaluable lessons in how to implement different types of EEG
analyses in Matlab using toolboxes such as EEGlab, Fieldtrip and the Network
Based Statistics toolbox. I now feel more proficient in time series and time/frequency
analysis of EEG data and I believe this knowledge will be very useful in helping me
to further my research career. Additionally, I have also learned how to process and
analyse TMS motor-evoked potential (MEP) data. I applied this knowledge to help
analyse data from ataxia patients receiving cerebellar TMS. This research project is
ongoing but is also likely to result in a publication. I am grateful to have had the
opportunity to work in such a stimulating environment and on such interesting
projects.
I would like to sincerely thank the arbiters of the David Fleming-Brown travel
scholarship awards for their generous contribution to the funding for my lab visit. The
visit was highly enjoyable and productive. I hope that the work I have carried out will
add meaningfully to the knowledge base on the neural action of non-invasive brain
stimulation and potentially facilitate the development of novel interventions for
pathological brain function.