Developmental Dyslexia (DD) is a neurobiological condition affecting the ability to read fluently and/or accurately. Analyzing resting-state electroencephalographic (EEG) activity in DD may provide a deeper characterization of the underlying pathophysiology and possible biomarkers. So far, studies investigating resting-state activity in DD provided limited evidence and did not consider the aperiodic component of the power spectrum. In the present study, adults with (n = 26) and without DD (n = 31) underwent a reading skills assessment and resting-state EEG to investigate potential alterations in aperiodic activity, their impact on the periodic counterpart and reading performance. In parieto-occipital channels, DD participants showed a significantly different aperiodic activity as indexed by a flatter and lower power spectrum. These aperiodic measures were significantly related to text reading time, suggesting a link with individual differences in reading difficulties. In the beta band, the DD group showed significantly decreased aperiodic-adjusted power compared to typical readers, which was significantly correlated to word reading accuracy. Overall, here we provide evidence showing alterations of the endogenous aperiodic activity in DD participants consistently with the increased neural noise hypothesis. In addition, we confirm alterations of endogenous beta rhythms, which are discussed in terms of their potential link with magnocellular-dorsal stream deficit.

Objective: Expectations are known to be key determinants of placebo and nocebo phenomena. In previous studies, verbal suggestions to induce such expectations have mainly focused on the direction and magnitude of the effect, whereas little is known about the influence of temporal information. Methods: Using an experimental placebo and nocebo design, we investigated whether information about the expected onset of a treatment effect modulates the start and time course of analgesic and hyperalgesic responses. Healthy volunteers (n = 166) in three placebo and three nocebo groups were informed that the application of an (inert) cream would reduce (placebo groups) or amplify pain (nocebo groups) after 5, 15, or 30 minutes. Two control groups were also included (natural history and no expectations). Participants’ pain intensity rating of electrical stimuli administered before and 10, 20, and 35 minutes after cream application was obtained. Results: Mixed-method analysis of variance showed a significant interaction between group and time (F(12,262) = 18.172, p < .001, pη² = 0.454), suggesting that pain variations differed across time points and between groups. Post hoc comparisons revealed that the placebo and nocebo groups began to show a significantly larger change in perceived pain intensity than the no-expectancy control group at the expected time point (p < .05) but not earlier (p > .05). Once triggered, the analgesic effect remained constant over the course of the experiment, whereas the hyperalgesic effect increased over time. Conclusions: Our results indicate that temporal suggestions can shape expectancy-related treatment effects, which, if used systematically, could open up new ways to optimize treatment outcome.

Visual crowding is the difficulty in identifying an object when surrounded by neighbouring flankers, representing a bottleneck for object perception. Crowding arises not only from the activity of visual areas but also from parietal areas and fronto-parietal network activity. Parietal areas would provide the dorsal-to-ventral guidance for object identification and the fronto-parietal network would modulate the attentional resolution. Several studies highlighted the relevance of beta oscillations (15-25 Hz) in these areas for visual crowding and other connatural visual phenomena. In the present study, we investigated the differential contribution of beta oscillations in the parietal cortex and fronto-parietal network in the resolution of visual crowding. During a crowding task with letter stimuli, high-definition transcranial Alternating Current Stimulation (tACS) in the beta band (18 Hz) was delivered bilaterally on parietal sites, on the right fronto-parietal network, and in a sham regime. Resting-state EEG was recorded before and after stimulation to measure tACS-induced aftereffects. The influence of crowding was reduced only when tACS was delivered bilaterally on parietal sites. In this condition, beta power was reduced after the stimulation. Furthermore, the magnitude of tACS-induced aftereffects varied as a function of individual differences in beta oscillations. Results corroborate the link between parietal beta oscillations and visual crowding, providing fundamental insights on brain rhythms underlying the dorsal-to-ventral guidance in visual perception and suggesting that beta tACS can induce plastic changes in these areas. Remarkably, these findings open new possibilities for neuromodulatory interventions for disorders characterised by abnormal crowding, such as dyslexia.

Developmental dyslexia (DD) affects approximately 10% of individuals, impairing reading ability thus limiting professional fulfilment and psychological wellbeing. DD is associated with both phonological and visual deficits, and the latter are attributed to dysfunctions of the magnocellular-dorsal visual stream, which has a critical role in planning saccades and supporting the extraction of letters/words identity. Currently, there are no effective treatments to restore the brain networks underlying visuospatial analysis and oculomotor efficiency. Adults with DD were enrolled in a randomised clinical trial introducing a non-invasive neuromodulation protocol specifically designed to enhance dorsal stream functionality. We used bi-focal beta-band transcranial alternating current stimulation (tACS) in parietal areas, due to the recognized role of beta oscillation in the dorsal stream functionality. Coupled with a 12-session visuoattentional training, such protocol induced improvements in reading speed, oculomotor control, and visual motion perception. Additionally, beta-tACS led to long-term enhancement of working memory. These outcomes were exclusive or superior to those obtained with a placebo/sham neuromodulation, and were accompanied by plastic changes in the stimulated brain networks. Overall, our findings show the efficacy of multisession tACS in improving core visual, oculomotor and cognitive deficits associated with reading disorders.

The temporal relationship between incoming signals is crucial in determining whether multisensory information is integrated into unitary percepts. Temporal binding windows (TBWs) define the time range within which multisensory inputs are highly likely to be perceptually integrated, even if asynchronous. TBWs widen with stimulus complexity and neurodevelopmental conditions (e.g., autism and schizophrenia), yet the key factors underlying their malleability remain unclear. The (quasi)rhythmic properties of sensory inputs, frequently embedded in natural stimuli (e.g., speech), are among the possible exogenous modulators. Indeed, stimulus spectral features can influence the alignment of neural excitability across sensory regions, synchronizing brain rhythms with external rhythmic patterns through phase‐reset mechanisms and neural entrainment. In a series of psychophysical studies, we presented simultaneity judgement tasks with pulsing audio‐visual (AV) streams amplitude‐modulated according to different regular frequencies or following purely rhythmic vs. quasi‐rhythmic (speech‐like) envelopes. Results show that TBWs decrease as the stimulus frequency increases and that speech‐like streams are integrated across larger TBWs. These findings highlight the importance of stimulus spectral structure in shaping multisensory perception. Furthermore, they show that quasi‐rhythmic spectrotemporal features of speech‐like streams induce more tolerant cross‐modal temporal processing even when the leading stimulation frequency is controlled for, putatively reflecting an adaptation to the variable rhythmic structure of natural speech. Our results align with neurophysiological accounts of neural entrainment and motivate future research in clinical populations with multisensory processing deficits.