**8.1 Brain-computer interfaces**

28 Neuroimaging for Clinicians – Combining Research and Practice

Like in most neurodegenerative diseases, neuroimaging in Parkinson's disease has been challenging because the majorities of neurons are affected before clinical symptoms evolve and diagnosis is made. The clinical symptoms of PD appear when approximately 50-80% of the nigral dopamine (DA) neurons have been lost already. Consequently, structural imaging has in general been unrewarding, although some newer MRI techniques, such as diffusion tensor imaging or shape analysis, are somewhat more promising and provided evidence for a reduced volume and changed connectivity of substantia nigra (Stössl, 2011). Functional neuroimaging is a promising candidate to detect specific changes in PD. Functional connectivity measured with resting state MRI provided evidence for changed pattern in motor network (Wu et al., 2009; Helmich et al., 2010) and in the default network (Palmer et al., 2010). MRI spectroscopy may be useful in differentiating between PD and atypical parkinsonian syndromes (Firbank et al., 2002). Functional MRI in PD has been widely used and proven to be sensitive to e.g. polymorphism of catechol-O-metyltransferase (COMT) in PD. Different activation patterns in fronto-parietal areas in an fMRI task provided a clear link to genotype, dopaminergic medication and cognitive performance in PD patients (Williams-Gray et al., 2007, 2008). In the future, functional neuroimaging may be used to get a fast and objective

Among neurodegenerative disorders, HD is unique in that individuals destined to develop symptoms can be identified through genetic testing before clinical signs of the disease begin. This raises the possibility of developing therapies to prevent or delay the onset of clinical manifestations in HD gene carriers. Therefore, substantial effort has been dedicated to the characterization of quantitative descriptors of disease progression in premanifest individuals (Eidelberg & Surmeier, 2011). Neuroimaging may be used to clarify diagnosis in the pre-symptomatic stage. The idea of imaging as a preclinical marker in HD was

The vast number of neuroimaging studies in HD traditionally was on single brain regions like structural and functional studies on the striatum. Several PET studies revealed association of striatal and cortical dysfunction in association with genetic alterations and cognitive function. However, with the evolvement of MRI volumetric studies with low patient load, better insight on striatal function was found in a faster and easier way. However, even with this technique, systems-level changes might not be detectable. Connectivity studies like in resting state MRI might be more susceptible and applicable in

Despite different aetiology of neurodegenerative diseases, similar approaches have been used in diseases of the central and peripheral nervous system. MRI based neuroimaging has extended our understanding of involvement of cortical structures which by far outreach the usually described clinical changes. Different neuroimaging techniques provide limitations that can be compensated by other techniques. Structural and functional MRI has taken over radio nucleotide dependent measurements in clinical

**6.2 Functional neuroimaging in Parkinson's disease** 

means of functional and genetic status in advanced stage PD patients.

supported by findings in a prospective observational study (Tabrizi et al., 2011).

**6.3 Functional neuroimaging in Huntington's disease** 

the future.

**7. Conclusion** 

Brain computer interfaces (BCIs) are a technique, which transfers and translates brain signals to technical devices for communication, control of environment (e.g. light switches) or prosthetic devices. BCIs are the only applicable means for communication in patients with advanced neurodegenerative diseases and no voluntary muscle control like in complete locked-in patients (CLIS) at end stage of ALS. There has been the unsolved question why patients in CLIS are unable to control EEG BCIs (Kübler & Birbaumer, 2008). With the means of functional neuroimaging, the question of activity of the idling brain of CLIS patients might be solved. Neuroimaging provide essential insight into the brains of patients with neurodegenerative diseases who are unable to communicate due to the loss of motor control like in ALS or cognitive ability like in dementia.
