Biology subjects

Conto, F.

Publications and source records attributed to Conto, F..

5 recordsLinked to original sources

bioRxiv2025

Hemispheric Dissociation Revealed by Attentional Isolation and tRNS

Prolonged sensory imbalance, induced by directing attention to one visual field, can paradoxically enhance performance in the opposite, non-attended visual field. This effect is likely driven by the brains homeostatic mechanisms that regulate excitation and inhibition between hemispheres in homotopic attention processing regions. Here, we employed transcranial random noise stimulation (tRNS) to modulate cortical excitability and probe its role in interhemispheric dynamics controlling visual attention. Specifically, we used a procedure called attentional isolation, where neurotypical participants covertly focused their visual attention in one hemifield (the attended visual field) for 30 minutes. Performance changes in both the unattended (opposite) visual field and the attended visual field were measured following this manipulation. We applied transcranial random noise stimulation (tRNS) over the right or left frontoparietal cortex to modulate the excitability of one hemisphere relative to the other during attention isolation, probing the neural mechanisms underlying the observed contralateral performance shift. Our results showed improved performance in the previously unattended visual field following the attentional isolation period after sham stimulation. However, tRNS revealed a functional dissociation between the hemispheres: right hemisphere active stimulation abolished the performance improvement, while left hemisphere stimulation preserved it. These findings suggest distinct roles for the left and right hemispheres in modulating paradoxical visual performance shifts and may inform the development of novel neurorehabilitation strategies for clinical populations.

neuroscience↗

bioRxiv2024

When Attention Hurts: The Effect Of rTMS On Neural Correlates Of Time Perception

The parietal lobe plays a crucial role in the attentional networks that help shape our perception, including our perception of time. Based on neuropsychological and neurophysiological evidence, a "when" pathway including the right parietal lobe has been proposed as the critical cortical site for the discrimination of objects across time. When an oddball stimulus is presented in a stream of identical standard stimuli, it is perceived as lasting longer, even when its actual duration is shorter. While attentional capture seems to play a major role in this subjective expansion of time the cortical mechanisms responsible for this effect remain unclear. We therefore set to investigate the direct role of parietal brain areas in time perception using combined repetitive transcranial magnetic stimulation (rTMS) and electroencephalogram (EEG). We measured the perceived duration of an oddball stimulus in each participant before and after inhibitory 1-Hz rTMS stimulation at one of three scalp locations: the right intraparietal sulcus (rIPS), the right inferior parietal lobe (rIPL), or the occipital cortex as a control. EEG was recorded throughout. Stimulation over the rIPL caused a more veridical experience of times subjective expansion towards the oddball, while rTMS over the rIPS and the occipital cortex had no effect. These data provide theoretically challenging notions to the concept of the cortexes role within time perception and the mechanisms involved.

neuroscience↗

bioRxiv2022

The role of the parietal lobe in task-irrelevant suppression during learning

BackgroundAttention optimizes the selection of visual information, while suppressing irrelevant visual input through cortical mechanisms that are still unclear. We set to investigate these processes using an attention task with an embedded to-be-ignored interfering visual input. ObjectiveWe delivered electrical stimulation to attention-related brain areas to modulate these facilitatory/inhibitory attentional mechanisms. We asked whether training on a task while being simultaneously exposed to visual features from a different task tested at baseline and post-training might influence performance on the baseline task. MethodsIn Experiment one, subjects performed an orientation discrimination (OD) task using a pair of gratings presented at individuals psychophysical threshold. We then trained participants over multiple sessions on a temporal order judgment task (TOJ), using the exact same gratings but presented with different time offsets. On the last session we re-tested OD. We coupled training with transcranial random noise stimulation (tRNS) over the parietal cortex, the human middle temporal area or sham, in three separate groups. In Experiment two, subjects performed the same OD task at baseline and post-training, while tRNS was delivered at rest during training. ResultsResults showed that tRNS over parietal cortex facilitated learning of the trained task. Moreover, we found a detrimental effect on OD when subjects received parietal tRNS coupled with training, but a benefit on OD when subjects received stimulation while at rest. ConclusionsThese results clearly indicate that task-irrelevant information is actively suppressed during learning, and that this prioritization mechanism of selection likely resides in the parietal cortex.

neuroscience↗

bioRxiv2020

Attention network modulation via tRNS correlates with attention gain

Transcranial Random Noise Stimulation (tRNS) can enhance vision in the healthy and diseased brain. Yet, the impact of tRNS on large-scale cortical networks is still unknown. We investigated the impact of tRNS coupled with behavioral training on resting-state functional connectivity and attention. We trained human subjects for four consecutive days on two attention tasks, while receiving tRNS over the intraparietal sulci, the middle temporal areas, or sham stimulation. We measured resting state functional connectivity of nodes of the dorsal and ventral attention network (DVAN) before and after training. We found a strong behavioral improvement and increased connectivity within the DVAN after parietal stimulation only. Crucially, behavioral improvement positively correlated with connectivity measures. We conclude changes in connectivity is a marker for the enduring effect of tRNS upon behavior. Our results suggest that tRNS has strong potential to augment cognitive capacity in healthy individuals and promote recovery in the neurological population.

neuroscience↗

bioRxiv2020

Controlling brain state prior to stimulation of parietal cortex prevents deterioration of sustained attention

Sustained attention is a limited resource which declines during daily tasks. Such decay is exacerbated in clinical and aging populations. Recent research has demonstrated that inhibition of the intraparietal sulcus (IPS) using low-frequency transcranial magnetic stimulation (LF-rTMS) can lead to an upregulation of functional communication within the attention network. Attributed to functional compensation for the inhibited node, this boost outlasts the stimulation for tens of minutes. Despite the neural change, no behavioral correlate has been found in healthy subjects, a necessary direct evidence of functional compensation. To understand the functional significance of neuromodulatory induced fluctuations on attention, we sought to boost the impact of LF-rTMS through controlling neural excitability prior to LF-rTMS, with the goal to impact behavior. Brain state was controlled using high-frequency transcranial random noise stimulation (HF-tRNS), shown to increase and stabilizes neuronal excitability. Using fMRI-guided stimulation protocols combining HF-tRNS and LF-rTMS, we tested the post-stimulation impact on sustained attention via a multiple object tracking task (MOT). Whilst attention deteriorated across time in the control conditions, HF-tRNS followed by LF-rTMS maintained attention performance up to 94 minutes, doubling the length of successful sustained attention. Multimethod stimulation was also more effective when targeting right IPS, supporting the notion of specialized attention processing in the right hemisphere. Used in a cognitive domain dependent on network-wide neural activity, this tool may be effective in causing lasting neural compensation important for clinical rehabilitation.

neuroscience↗