Salatino, A. | bioRxiv Science

bioRxiv2023

"Fire! Do Not Fire!": A new paradigm testing how autonomous systems affect agency and moral decision-making.

Autonomous systems have pervaded many aspects of human activities. However, research suggest that the interaction with those machines may influence human decision-making processes. These effects raise ethical concerns in moral situations. We created an ad hoc setup to investigate the effects of system autonomy on moral decision-making and human agency in a trolley-like dilemma. In a battlefield simulation, participants had to decide whether to initiate an attack depending on conflicting moral values. Our results suggest that our paradigm is suitable for future research aimed at understanding the effects of system autonomy on moral decision -making and human agency.

neuroscience↗

bioRxiv2023

Medial prefrontal cortex stimulation abolishes implicit reactions to threats and prevents the return of fear

Down-regulating emotional overreactions toward threats is fundamental for developing treatments for anxiety and post-traumatic disorders. The prefrontal cortex (PFC) is critical for top-down modulatory processes, and despite previous studies adopting repetitive Transcranial Magnetic Stimulation (rTMS) over this region provided encouraging results in enhancing extinction, no studies have hitherto explored the effects of stimulating the medial PFC (mPFC) on threat memory and generalization. Here we showed that rTMS applied before threat memory retrieval abolishes implicit reactions to learned and novel stimuli in humans. These effects were not due to inhibition of electrodermal reactivity and enduringly persisted one week later in the absence of rTMS. No effects were detected on explicit recognition. Critically, we observed stronger attenuation of defensive responses in subjects stimulated over the mPFC than the dlPFC. Our findings uncover a prefrontal region whose modulation can permanently hamper implicit reactions to learned dangers, representing an advance to long-term deactivating overreactions to threats.

neuroscience↗

bioRxiv2022

Evaluation of GABAAR-mediated inhibition in the human brain using TMS-evoked potentials

GABAA receptor (GABAAR) - mediated inhibition participates in the control of cortical excitability, and its impairment likely contributes to the pathologic excitability changes that have been associated with multiple neurological disorders. Therefore, there is a need for its direct evaluation in the human brain, and the combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) might represent the optimal tool. TMS-evoked brain potentials (TEPs) capture the spread of activity across the stimulated brain network, and since this process at least partially depends on the GABAAR-mediated inhibition, TEPs may constitute relevant biomarkers of local GABAAergic function. Here, we aimed to assess the effect of GABAARs activation using TEPs, and to identify TEP components that are sensitive to the state of GABAAergic inhibition. In 20 healthy subjects, we recorded TEPs evoked by sub- and supra-threshold stimulation of the primary motor cortex (M1), motor-evoked potentials (MEPs) and resting-state EEG (RS-EEG). GABAARs were activated (1) pharmacologically by oral administration of alprazolam compared to placebo within each subject, and (2) physiologically using a sub-threshold conditioning stimulus to characterize the effect of short-latency intracortical inhibition (SICI). In supra-threshold TEPs, alprazolam suppressed the amplitude of components N17, N100 and P180, and increased component N45. The pharmacological modulation of N17 correlated with the change observed in MEPs and with the alprazolam-induced increase of lower {beta}-band RS-EEG. Only a reduction of N100 and P180 was found in sub-threshold TEPs. TEP SICI manifested as a reduction of N17, P60 and N100, and its effect on N17 correlated with the alprazolam-induced N17 suppression and {beta} increase. Our results indicate that N17 of supra-threshold TEPs could serve as a non-invasive biomarker of local cortical excitability reflecting the state of GABAAR-mediated inhibition in the sensorimotor network. Furthermore, the alprazolam-induced increase of {beta}-band oscillations possibly corresponds to the increased inhibitory neurotransmission within this network.

neuroscience↗