Posture affects emotional responses: a Head Down Bed Rest and ERP study.

Body posture, mainly represented by horizontal bed rest, has been found to be associated with cortical inhibition, altered perceptual and cognitive processing. In the present research, the influence of Head Down Bed Rest (HDBR)--a condition also termed simulated microgravity--on emotional responses has been studied. Twenty-two male subjects were randomly assigned to either Sitting Control or HDBR group. After 3-h, subjects attended to a passive viewing emotional task in which 75 IAPS slides, divided into 25 pleasant, 25 neutral and 25 unpleasant, were presented in random order for 6s each, while EEG was recorded from F7, F8 and Pz locations. Results showed in Sitting Controls the expected greater P300 and Late Positive Potential (LPP) to pleasant and unpleasant compared with neutral slides, an effect which indicates greater processing of emotional arousing stimuli. The HDBR group showed smaller non-significant differences among all emotional conditions in both ERP components. Arousal and valence subjective evaluations, typically less sensitive to experimental manipulation, did not differentiate groups. The observed ability of HDBR to inhibit cortical emotional responses raises an important issue on the risk that astronauts underestimate a dangerous/threatening situation or that long-term bedridden inpatients develop depressive symptoms.

The efficacy of EEG neurofeedback aimed at enhancing sensory-motor rhythm theta ratio in healthy subjects.

Scientific evidence supporting the reliability of neurofeedback (NF) in modifying the electroencephalographic (EEG) pattern is still limited. Several studies in NF research and clinical setting have been focused to increase sensory-motor rhythm (SMR) and simultaneously decrease theta activity with the aim of increasing attention performance and reducing hyperactive and impulsive behaviors. The goal of the present study was to assess the efficacy of NF training to enhance the SMR/theta ratio across sixteen sessions of training in eight healthy volunteers. Results suggested an increase of SMR/theta across weeks of training. Theta activity was strongly and steadily inhibited since the first session of training with slight decreases in the following weeks; instead, SMR was strongly inhibited at the beginning and progressively increased across sessions. These results suggest that individuals are able to inhibit theta activity easily while they fail to increase SMR in the first sessions. On the other hand, a separate analysis performed on the baseline preceding NF revealed a decreasing trend of SMR/theta ratio across the 8 weeks of training. Results point to the importance of providing EEG data in addition to behavioral modification, during NF training, to avoid possible misinterpretation of results.

Gender differences in emotional responses: a psychophysiological study.

Gender differences in emotional responses have been investigated in two groups of students, 22 males and 21 females. Participants watched a set of sixty emotional standardized slides divided into pleasant, neutral and unpleasant, while Startle reflex, Evoked Potentials, Heart Rate, facial EMG and Skin Conductance were recorded. Startle reflex amplitude, an index modulated by amygdala and orbitofrontal cortex and sensitive to aversive emotional stimuli, was overall larger in women. In addition, startle emotion modulation was greater in women with respect to men. Slow Evoked Potentials (400-800 ms), a measure representing the cognitive component of the emotional response, revealed gender differences in the left prefrontal site, with women showing greater positivity to unpleasant compared with pleasant slides while men had greater positivity to pleasant vs. neutral slides. Women, compared with men, perceived all slides as less pleasant and reported greater arousal to unpleasant condition. Results are in line with known functional brain differences, at level of limbic and paralimbic structures, between men and women, and point to biologically grounded greater sensitivity and vulnerability of women to adverse/stressful events.

Effects of simulated microgravity on brain plasticity: a startle reflex habituation study.

There is limited but increasing evidence that space environment, namely weightless condition, may affect astronauts' cerebral neurotransmitters and cognitive performance. The present experiment hypothesized that learning and brain plasticity are affected by simulated microgravity condition. To this aim, 22 male subjects matching astronauts' characteristics were divided in two groups, Head-Down Bed Rest (HDBR) and Sitting Control. After 3-h bed rest (or sitting condition) subjects started a picture viewing task during which 30 acoustic startle probes (100 dBA loudness), divided into three consecutive blocks, were delivered through headphones while startle reflex amplitude was measured from the EMG of the orbicularis oculi muscle. Habituation analysis of the startle reflex showed a normal reflex inhibition across blocks in sitting controls and no habituation in HDBR subjects. Results point to a microgravity-induced lack of startle reflex plasticity in subjects matching astronauts, a learning deficit which may affect the success of long-term space missions.

Decision Preceding Negativity in the Iowa Gambling Task: an ERP study.

The present study aimed to investigate the slow negative potential (termed Decision Preceding Negativity, DPN, from the family of the Readiness Potential) which precedes a willed risky decision. To this end, evoked potentials preceding and following an economic choice were measured in a sample of 16 male students during the Iowa Gambling Task modified for ERPs recording. Statistics revealed reduced positivity/relative greater negativity (marking relative activation) in right prefrontal sites and reduced negativity (indicating relative inhibition of DPN) in central clusters over left premotor cortex, 500 ms before picking from economically disadvantageous risky decks. Analyses of the potentials elicited by the economic outcome (wins vs. losses) showed the classical frontal negativity (N260) to the economic losses. Results are consistent with the view that an economically risky decision is preceded by a relative inhibition of the planned motor response together with the activation of emotion-related right frontal sites.

Reduced startle reflex and aversive noise perception in patients with orbitofrontal cortex lesions.

In the present study, the primary emotional response represented by the acoustic startle reflex was investigated in a group of six male patients, selected with lesions of the orbitofrontal cortex, and twenty matched healthy controls. Accurate neuropsychological assessment and lesion mapping showed relatively spared cognitive functioning in the patient group, most of the lesions being confined to the bilateral polar orbitofrontal cortex. Patients had significant inhibition of startle amplitude, together with a reduced self-evaluated perception of the unpleasantness of the acoustic probe stimulus. Results add to current literature on the circuit of the human startle reflex, by suggesting cortical-limbic down-regulation of the orbitofrontal cortex on the main startle pathway, probably at the level of the activating reticular system. The orbitofrontal cortex, together with the amygdala, is confirmed to represent the main center organizing both primary and secondary learned aspects of emotions.