Fluctuations in electrodermal activity reveal variations in single trial brain responses to painful laser stimuli--a fMRI/EEG study.

Pain is a complex experience with sensory, emotional and cognitive aspects. It also includes a sympathetic response that can be captured by measuring the electrodermal activity (EDA). The present study was performed to investigate which brain areas are associated with sympathetic activation in experimental pain; an issue that has not been addressed with fMRI (functional magnetic resonance imaging) thus far. Twelve healthy subjects received painful laser stimulation to the left hand. The event-related fMRI BOLD (blood oxygen level dependent) response was measured together with simultaneous EEG (electroencephalography) and EDA recordings. Laser stimuli induced the expected EDA response, evoked EEG potentials and BOLD responses. Single trial EDA amplitudes were used to guide further analysis of fMRI and EEG data. We found significantly higher BOLD responses in trials with high EDA vs. low EDA trials, predominantly in the insula and somatosensory cortex (S1/S2). Likewise, in the EEG we found the N2 laser evoked potentials to have significantly higher amplitudes in trials with high vs. low EDA. Furthermore EDA-informed BOLD modeling explained additional signal variance in sensory areas and yielded higher group level activation. We conclude that the sympathetic response to pain is associated with activation in pain-processing brain regions, predominantly in sensory areas and that single trial (EDA)-information can add to BOLD modeling by taking some of the response variability across trials and subjects into account. Thus, EDA is a useful additional, objective index when pain is studied with fMRI/EEG which might be of particular relevance in the context of genetic- and pharmacoimaging.

Real-time monitoring of brain activity in patients with specific phobia during exposure therapy, employing a stereoscopic virtual environment.

Exposure therapy is a behavioral technique that is reported to be the most effective, long-lasting treatment for patients suffering from specific phobia. During the performance in enclosed spaces, the patients show a strong psychophysiological response to the phobic stimulus that is normally avoided. This psychophysiological response changes characteristically during the course of exposure. We implemented an electroencephalographic monitoring focusing on event-related potentials to resolve the modulation of preattentive information processing by the anxiety state of the subject. Therefore, mismatch-negativity (MMN) was chosen as parameter using a passive auditory oddball paradigm that does not interfere with performance in the virtual environment. The results of this neurophysiological monitoring are demonstrated in one patient suffering from claustrophobia.

Immersive virtual environments in cue exposure.

Cue reactivity to drug-related stimuli is a frequently observed phenomenon in drug addiction. Cue reactivity refers to a classical conditioned response pattern that occurs when an addicted subject is exposed to drug-related stimuli. This response consists of physiological and cognitive reactions. Craving, a subjective desire to use the drug of choice, is believed to play an important role in the occurrence of relapse in the natural setting. Besides craving, other subjective cue-elicited reactions have been reported, including withdrawal symptoms, drug-agonistic effects, and mood swings. Physiological reactions that have been investigated include skin conductance, heart rate, salivation, and body temperature. Conditioned reactivity to cues is an important factor in addiction to alcohol, nicotine, opiates, and cocaine. Cue exposure treatment (CET) refers to a manualized, repeated exposure to drug-related cues, aimed at the reduction of cue reactivity by extinction. In CET, different stimuli are presented, for example, slides, video tapes, pictures, or paraphernalia in nonrealistic, experimental settings. Most often assessments consist in subjective ratings by craving scales. Our pilot study will show that immersive virtual reality (IVR) is as good or even better in eliciting subjective and physiological craving symptoms as classical devices.