This
thesis
examines
how
the
human
brain
adapts
after
peripheral
vestibular
injury.
Vestibular
perceptual
function
is
used
as
a
probe
of
cortical
vestibular
function.
A
paradigm
determining
vestibular
perceptual
thresholds
to
yaw
axis
rotation
by
a
method
of
limits
is
described.
Asymmetry
in
the
thresholds
is
induced
in
normal
subjects
with
galvanic
vestibular
stimulation.
In
patients
with
acute
vestibular
neuritis,
perceptual
thresholds
were
bilaterally
elevated,
with
less
asymmetry
when
compared
to
the
brainstem
reflexive
function.
Thresholds
were
measured
in
a
prospective
longitudinal
study
in
vestibular
neuritis
patients,
assessed
acutely
and
at
follow-‐up
(n=16).
Assessments
comprised
vestibular
caloric
testing,
visual
dependency
measures,
questionnaire
measures
of
symptom
load,
anxiety,
depression
and
fear
of
body
sensations.
Clinical
recruitment
found
a
low
rate
of
correct
diagnoses
by
referring
clinicians.
Symptomatic
outcome
at
follow-up
was
associated
with
increased
visual
dependence,
asymmetric
caloric
function,
increased
anxiety
and
depression.
It
was
also
associated
with
increased
fear
and
anxiety
of
body
sensations
present
acutely,
suggesting
this
may
be
predisposing.
The
anatomical
substrate
of
central
compensation
was
investigated
in
patients
with
bilateral
vestibular
failure
(n=12)
and
normal
controls
(n=15)
using
functional
MRI.
A
novel
air
turbine-powered
vibrating
device
was
developed
to
provide
high
and
low
levels
of
proprioceptive
stimulus
to
neck
rotator
muscles.
This
was
combined
with
a
horizontal
visual
motion
paradigm
in
a
factorial
design.
A
lateralised
interaction
was
found
in
the
lateral
occipital
visual
processing
areas
in
the
avestibular
patients.
In
addition
to
the
known
visual-vestibular
interaction,
this
demonstrates
a
visuo-proprioceptive
interaction,
which
may
reflect
compensation
after
vestibular
injury. Conclusions:
Vestibular
perceptual
function
can
be
measured
in
disease,
and
is
elevated
in
patients
with
acute
peripheral
vestibulopathy.
Specific
psychological
and
physiological
factors
associated
with
clinical
recovery
after
vestibular
neuritis
are
proposed.
Functional
MRI
shows
that
proprioceptive
signals
interact
with
visual
motion
signals
in
patients
with
vestibular
failure
