Dottorato in PSICOLOGIA E SCIENZA COGNITIVA

Titolo della tesi: The Effectiveness of Targeted Memory Reactivation in Modulating Attentional Bias

Attention is a critical cognitive function that helps us filter and focus on relevant stimuli. Emotions play a crucial role in shaping our attention and steering our daily decisions and actions. Attentional bias (AB) in clinical populations refers to the tendency to focus on negative information while ignoring or discounting positive or neutral stimuli. This scenario leads to distorted cognitive processes, contributing to the development and maintenance of psychopathology. An AB index is provided by reaction times (RTs) in the dot-probe task (DPT), which measures the time taken to direct attention towards a target stimulus (i.e., white dot) appearing after the simultaneous presentation of two emotional stimuli (negative/positive). Individuals with pathological attentional bias show quicker responses and larger P300 amplitudes to dots replacing negative images than positive ones. Attentional Bias Modification (ABM) aims to correct these biases by training individuals to redirect their attention to positive stimuli. By increasing the probability of dot appearance to 80% behind positive images, individuals implicitly learn to redirect their attention away from negative stimuli and towards positive/neutral stimuli. Through repeated training sessions, ABM can reduce attentional bias towards negative stimuli by leveraging the brain's natural learning and implicit memory consolidation processes and, presumably, creating lasting changes in attentional patterns. Memory consolidation is critical for stabilizing and enhancing memories after initial acquisition, with sleep playing a crucial role. In this context, the TMR paradigm is an experimental technique that strengthens specific memory traces during sleep through sensory stimuli (odors/sounds) delivered primarily during slow-wave sleep (SWS). Our study investigates the effect of TMR on modulating AB at behavioral and electrophysiological levels. Twenty-two female students (mean age ± standard deviation, 21.86 years ± 2.64; age range: 20-30 years) were involved in a between-subjects study. AB was measured using a modified version of DPT, along with high-density EEG, before (T1) and after (T2) a nocturnal polysomnography with Acoustic Stimulation (ASTMR vs. ASCONTROL) during SWS. During the DPT, participants viewed pairs of emotional faces (happy/sad) followed by a probe and indicated their position (left/right). The participant response triggered a different auditory cue for trials in which the probe replaced the positive image (Positive Valence) and for trials in which the probe replaced the negative image (Negative Valence). During slow wave sleep, the ASTMR group was exposed to the sound stimuli linked to the Positive Valence trials, while the ASCONTROL group heard a novel sound. To evaluate the effects of TMR, Mixed Model Analysis was applied to RTs and P300 amplitude and latency of the ERP generated in response to the probe, including valence (Positive Valence vs Negative Valence), session (T1 vs T2), and group (ASTMR vs ASCONTROL) as within/between factors. The EEG correlates of TMR were assessed by comparing ERPs between the ASTMR and ASCONTROL groups, focusing on amplitude and time-frequency analysis using unpaired t-tests. Behaviorally, TMR led to a greater reduction in RTs at the DPT in the ASTMR group compared to ASCONTROL, although this was not valence-specific, indicating a general improvement in processing speed. At the electrophysiological level, TMR had valence-specific effects on P300 peak amplitude and latency in response to the probe, including a significant amplitude and latency reduction in the (reactivated) positive valence trials only, which was not observed in the ASCONTROL group. Additionally, the EEG correlates of TMR during sleep compared to those linked to the presentation of a completely new sound indicated a cortical response characterized by higher amplitude in the 700-1200 ms interval post-stimulation associated with increased spindle activity, suggesting an effective memory reactivation leading to successful memory consolidation in the ASTMR group. The findings highlight TMR's potential to modulate electrophysiological responses to emotional stimuli, providing a promising avenue for interventions targeting pathological AB through sleep-based processes. Future studies should explore the effects of repeated TMR sessions, leveraging advancements in home-based EEG technologies to conduct studies in more naturalistic settings. This scenario could open new avenues for developing sleep-based approaches to modify attentional biases and complement existing therapies for various psychological disorders.