Temporal (EEG) and spatial (fMRI) aspects of functional brain dysfunctions in schizophrenic patients

Currently, there is evidence demonstrating that schizophrenia is an illness characterized by multiple deficits in cognitive processes such as attention and memory. It is assumed that these are the consequence of functional and anatomical variations especially comprising frontal and temporo-parietal brain regions as well as abnormal interactions between these areas. These variations may result in altered neuronal contribution of affected brain regions during cognitive processes not only concerning the intensity of neuronal reactivity but also regarding their temporal aspects. We simultaneously recorded ERP and functional MRI data to examine brain regions involved in information processing and examined differences in the intensity of neuronal activity as well as temporal aspects of neuronal participation in schizophrenics and healthy controls.

14 male schizophrenic patients and age-matched healthy controls were examined with an auditory oddball paradigm in which subjects were required to press a button when an infrequent tone is presented in a series of frequent tones of a different pitch. FMRI data were collected in a 1.5 T Scanner with Gradient Echo EPI sequences [TE/TR=53ms/3s; 12 slices; matrix: 128×128; slice thickness: 8mm]. Simultaneous EEG recordings were done with MR-compatible EEG-amplifier (Brain Products) [61 channels according to the international 10–10 system; reference: Cz].

Behavioural data showed increased reaction times in schizophrenic patients compared to healthy controls. Electrophysiologically we replicated findings of previous studies revealing a P300 component after the presentation of rare stimuli mainly in parietal brain regions which was slightly less pronounced in patients than controls. Concerning functional MRI the rare stimuli led to the expected BOLD activations in SMA, anterior cingulate cortex, insula, thalamus, putamen, middle prefrontal gyrus, as well as temporo-parietal brain structures in healthy persons [Fig. 1; p(Bon)<0.001]. In patients comparable brain regions were activated but to a significantly lesser extent indicating pathological processes in a widespread network of brain regions [Fig. 2; p(Bon)<0.001]. Further analysis will determine the temporal characteristics of their contribution.

Fig. 1

Fig. 2