Abnormal language lateralisation in schizophrenia: Causal relations investigated with TMS

ABNORMAL LANGUAGE LATERALISATION IN SCHIZOPHRENIA, CAUSAL RELATIONS
INVESTIGATED WITH TMS.
Previous studies have shown, using functional magnetic resonance imaging
(fMRI), decreased cerebral lateralisation of language processing in
schizophrenia. Specifically, in addition to left hemisphere language areas,
patients with schizophrenia recruit right hemisphere homologue areas during
language tasks. We hypothesize that this activation of right hemisphere areas
reflects a compensatory functional pattern for language processing in
schizophrenia. We will investigate whether, using transcranial magnetic
stimulation (TMS), right hemisphere homologue areas contribute functionally to
language processing in schizophrenia, in contrast to control subjects in which
only left hemisphere areas are important for language processing.
Repetitive TMS will be used with a coil centered over the individual language
related brain areas (regions determined on the basis of available functional
MRI data) where after subjects perform three language tasks. We predict that
for all subjects, both healthy controls and patients, performance of the
language tasks will decrease after stimulating those areas in the brain that
have shown significant activation during a language task in the MRI scanner. In
schizophrenia patients these language related areas in the brain are found both
in the right and in the left brain, whereas in healthy controls only left
hemisphere areas are activated. Thus, in schizophrenia patients language areas
in both hemispheres are stimulated, both leading to reduced performance. In
healthy controls the left hemisphere area that shows activation during the fMRI
session is stimulated, leading to reduced performance, whereas stimulating the
homologue area in the right hemisphere does not lead to reduced performance.

The aim of this experiment is to test whether the right sided activity observed
in schizophrenics during language processing is either contributing,
interfering or just epiphenomenal by nature, as compared to healthy controls
with normal left lateralized language activation.

In this transcranial magnetic stimulation study, brain areas that showed
activation during a language task adminstered in another fMRI study, are
stimulated during 20 minutes. In schizophrenia patients we expect areas in both
hemispheres are related to language activation, in healthy controls only the
left hemisphere will show activation during language processing. After the rTMS
train we ask participants to make three language tasks on the computer. Results
on these tasks are analysed.

First we will inform the participants about our study, and ask them if they are
interested to participate. If they are interested we will send or give them an
information letter and explain them our study. Subsequently, if someone can and
wants to participate, we ask the participant to come two times for the
experiment which will take 60 minutes. During each session rTMS will be applied
on one of two brain areas, one in the left and one in the right hemisphere,
during 20 minutes. After stimulation the subject is asked to perform three
tasks on the computer. All are language tasks. From our own experience and from
colleagues, we know this is do-able. The subject can stop at every time during
the experiment.
There is no direct benefit for the participant. There is no risk in
participating in the study, every subjects is checked on TMS exclusion
criteria.