Reduced frontal functional asymmetry in schizophrenia during a cued continuous performance test assessed with near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) allows noninvasive, in vivo measurement o f changes in the concentrations of oxygenated hemoglobin (O(2)Hb) and deoxy genated hemoglobin (HHb) in brain tissue based on their distinctive optical properties. A previous NIRS investigation on healthy subjects (Fallgatter and Strik 1997) found indications of right frontal activation during a Cont inuous Performance Test (CPT) that are consistent with results from positro n emission tomography (PET) and event-related potentials studies. The indic ations consisted of right frontal blood oxygenation changes, consistent wit h a hemodynamic response, along with a significant left frontal increase in HHb The current study investigated whether this characteristic lateralized frontal NIRS activation pattern was present in a group of nine schizophren ia patients during the execution of a CPT. In contrast to the previous stud y, no overall or hemispheric activation effects were found in the schizophr enia subjects. Direct comparison of the results of the two studies confirme d group differences, with a lack of lateralized activation in schizophrenia patients. Furthermore, a trend of higher left/right HHb ratios at rest and during activation was found in patients with schizophrenia. The finding is interpreted as a sign of reduced specific lateralized frontal reactivity, possibly based on a left hemisphere functional deficit.