Wednesday August 01 2007
CEA
Weaker hemisphere-governed specificity for language in schizophrenia patients
Biol Psychiatry. 1;57(9):1020-1028
CEA
A joint CEA-CNRS team from the centre for neurosciences and imaging-based research against disease (I²BM-CI-NAPS), working with Caen University, Paris V University and Caen University Hospital, has used functional magnetic resonance imaging (fMRI) to make a recent breakthrough demonstrating that a change in the hemisphere lateralization1 of language in right-handed schizophrenic patients is persistent over time2.
In 95 to 100% of healthy right-handed subjects, it is the left hemisphere that is dominant for language. Broca’s area, the core site of speech processing, is also highly lateralized to the left in right-handers, whereas left-handers use either the left hemisphere or the right hemisphere, or even both.
In a previous study focused on schizophrenia patients, the CI-NAPS research team revealed that right-handed schizophrenics displayed weaker left-sided language lateralization, or even atypical (right-sided) language lateralization in around 30% of subjects3. This is a breakthrough finding, given that schizophrenia is essentially characterized by language-related disorders such as auditory hallucinations and disorganized thinking.
Two years on from this initial publication, the CI-NAPS team has demonstrated the stability of this functional alteration in schizophrenia patients via a long-term study. The ability to demonstrate that this kind of functional alteration is stable over time, independently of the severity of the symptoms, task performances and duration of the disease, opens perspectives for identifying a disease-inherent marker.
These results may have a significant impact on how a new therapy – repetitive transcranial magnetic stimulation (rTMS)4 – is handled. This technique is currently recommended in the treatment of auditory hallucinations in schizophrenic patients. fMRI, which is also a non-invasive method that makes it possible to assess language networks and functional language lateralization, could be employed to optimize guidance towards the rTMS target sites, i.e. either to the right or the left depending the that individual patient’s predominant lateralization, and thus significantly improve the therapeutic benefits of this novel strategy.
The illustration shows fMRI-detected activation patterns when listening to text : predominantly left-sided in a control subject but mainly right-sided in a schizophrenia patient
1 Lateralization is the term used to describe performance differences between the right and left brain hemispheres, each of which has its own way of understanding environment, language, action, space, emotions, etc.
2Razafimandimby A, Maiza O, Herve PY, Lecardeur L, Delamillieure P, Brazo P, Mazoyer B, Tzourio-Mazoyer N, Dollfus S. (2007) Stability of functional language lateralization over time in schizophrenia patients. Schizophrenia Research 94(1-3):197-206
3Dollfus S, Razafimandimby A, Delamillieure P, Brazo P, Joliot M, Mazoyer B, Tzourio-Mazoyer N. (2005) Atypical hemispheric specialization for language in right-handed schizophrenia patients. Biol Psychiatry. 1;57(9):1020-1028
4 rTMS (Repetitive transcranial magnetic stimulation). Repetitive transcranial magnetic stimulation is a method used for treatment-resistant or major depression. The painless stimulation is triggered via a magnetic coil placed at the frontal cortex (to treat depression) or the temporal cortex (to treat auditory hallucination).