Biology subjects

Iannetti, G.

Publications and source records attributed to Iannetti, G..

8 recordsLinked to original sources

bioRxiv2026

Scene Structure Predicts Perceptual Decisions in Naturalistic Detection Tasks

The human visual system can identify objects in complex natural scenes, yet the mechanisms supporting robust perception under such variable conditions remain incompletely understood. Here, we investigate how the statistical structure of natural scenes shapes perceptual evidence formation and determines whether near-threshold stimuli are perceived correctly or incorrectly. We combine controlled psychophysics, outdoor augmented reality (AR), deep neural networks (DNNs), image-feature analysis, and EEG to examine how background context modulates perceptual decisions. Across multiple detection tasks, human performance was systematically influenced by probe-free background structure. DNNs trained on background images alone predicted correct and incorrect behavioral outcomes, with stronger effects in postcue conditions, suggesting that global scene context contributes to local perceptual decisions when spatial uncertainty is higher. AR experiments further showed that these context-driven effects persist in naturalistic viewing environments. To identify the visual information underlying these effects, we analyzed low-level image statistics. Texture entropy and edge density emerged as informative features, and conventional machine-learning models trained on these measures achieved meaningful correct/incorrect classification. Finally, EEG analyses revealed neural signatures of image-driven perceptual variability: activity during the probe-free preimage window distinguished later correct from incorrect trials, and combining EEG with image-derived features improved decoding performance. Together, these findings show that perception in natural scenes is not determined solely by the target, but is shaped by the statistical structure of the surrounding context. By linking psychophysics, AR, DNN modeling, image statistics, and EEG, this work provides a unified framework for understanding how environmental structure and neural dynamics jointly support perceptual decision-making.

neuroscience↗

bioRxiv2026

Spontaneous locus coeruleus bursts coincide withtransient global brain state changes similar to thoseelicited by surprise

Sudden and isolated sensory stimuli (SISS) engage the extralemniscal system and elicit widespread electrocortical responses in the brain. These responses, consisting of both time-domain transients and spectral changes, reflect a switch of the global brain state that likely prepares the organism for subsequent urgent behaviours. Crucially, SISS also elicit a short-latency phasic response in a key component of the extralemniscal system in the brainstem, the noradrenergic Locus Coeruleus (LC) nucleus. Such stimulus-evoked LC firing is associated with the electrocortical markers of extralemniscal activation. LC neurons also display burst-like firing spontaneously, i.e., without imposed sensory stimuli, for example, during quiet wakefulness, sleep, or anaesthesia. However, this phenomenon remains underexplored. We therefore measured, in freely behaving rats, the prefrontal electrocorticogram (ECoG) responses following spontaneous LC bursts. In addition, we compared these ECoG responses to those triggered by electrical LC stimulation or auditory SISS. We found that ECoG responses were proportional to the magnitude of the spontaneous LC bursts or microstimulation, and remarkably similar to those elicited by SISS. Finally, suppression of noradrenergic transmission with systemic clonidine administration attenuated the auditory-evoked ECoG response. These results suggest that LC plays a role in generating the transient brain state changes elicited by SISS.

neuroscience↗

bioRxiv2024

A replicable and generalizable neuroimaging-based indicator of pain sensitivity across individuals

Developing neural indicators of pain sensitivity is crucial for revealing the neural basis of individual differences in pain and advancing individualized pain treatment. To identify reliable neural indicators of pain sensitivity, we leveraged six large and diverse functional magnetic resonance imaging (fMRI) datasets (total N=1046). We found replicable and generalizable correlations between nociceptive-evoked fMRI responses and pain sensitivity for laser heat, contact heat, and mechanical pains. These fMRI responses correlated more strongly with pain sensitivity than with tactile, auditory, and visual sensitivity. Moreover, we developed a machine learning model that accurately predicted not only pain sensitivity but also pain reduction from different interventions in healthy individuals. Notably, these findings were influenced considerably by sample sizes, requiring >200 for univariate correlation analysis and >150 for multivariate machine learning modelling. Altogether, we demonstrate the validity of decoding pain sensitivity from fMRI responses, thus facilitating interpretations of subjective pain reports and promoting more mechanistically informed investigation of pain physiology.

neuroscience↗

bioRxiv2023

A cortical mechanism linking saliency detection and motor reactivity in rhesus monkeys

Sudden and surprising sensory events trigger neural processes that swiftly adjust behavior. To study the phylogenesis and the mechanism of this phenomenon, we trained two rhesus monkeys to keep a cursor inside a visual target by exerting force on an isometric joystick. We examined the effect of surprising auditory stimuli on exerted force, scalp electroencephalographic (EEG) activity, and local field potentials (LFP) recorded from the dorso-lateral prefrontal cortex. Auditory stimuli elicited (1) a biphasic modulation of isometric force: a transient decrease followed by a corrective tonic increase, and (2) EEG and LFP deflections dominated by two large negative-positive waves (N70 and P130). The EEG potential was maximal at the scalp vertex, in all respects similar to the human vertex potential. Electrocortical potentials and force were tightly coupled: the P130 amplitude predicted the magnitude of the corrective force increase, particularly in the EEG electrodes contralateral to the limb exerting force, and in the LFP recorded from deep rather than superficial cortical layers, suggesting a direct effect of the vertex potential on the motor output determining the behavior. These results disclose a phylogenetically-preserved cortico-motor mechanism supporting adaptive behavior in response to salient sensory events.

neuroscience↗

bioRxiv2022

Cold stimulation without touch: a method for perceptual and neurophysiological studies of thermal processing and multimodal interactions

BackgroundThermal and tactile stimuli are transduced by different receptor classes. However, mechano- and thermo-sensitive afferents interact at spinal and supraspinal levels. Yet, most studies on responses to cooling stimuli are confounded by mechanical contact, making these interactions difficult to isolate. Methods for precise control of non-mechanical thermal stimulations remain challenging, particularly in the cold range. New MethodWe developed a non-tactile, focal, temperature-controlled, multi-purpose cooling stimulator. This method controls the exposure of a target skin region to a dry-ice source. Using a thermal camera to monitor skin temperature, and adjusting the source-skin distance accordingly, we could deliver non-tactile cooling stimuli with customisable profiles, for studying different aspects of cold sensation. ResultsTo validate our method, we measured absolute and relative thresholds for cold sensation without mechanical contact in 13 human volunteer participants, using the method of limits. We found that the absolute cold detection threshold was 32.71{degrees}C {+/-} 0.88 {degrees}C. This corresponded to a threshold relative to each participants baseline skin temperature of -1.08 {degrees}C {+/-} 0.37 {degrees}C. Comparisons with Existing MethodOur method allows cooling stimulation without the confound of mechanical contact, in a controllable and focal manner. ConclusionsWe report a non-contact cooling stimulator and accompanying control system. We used this to measure cold thresholds in the absence of confounding touch. Our method enables more targeted studies of both cold sensory pathways, and of cold-touch interactions. HighlightsMost studies on cold sensation fail to control for concomitant tactile input. A method to deliver non-tactile cooling stimuli was developed. The method combines dry ice, a thermal camera, and motorised stages. The method delivers rapid ramps and feedback-controlled pulses. Thresholds for contactless cold perception were estimated in humans.

neuroscience↗

bioRxiv2020

The Hard Limits of Decoding Mental States: The Decodability of fMRI

High-profile studies claim to assess mental states across individuals using multi-voxel decoders of brain activity. The fixed, fine-grained, multi-voxel patterns in these "optimized" decoders are purportedly necessary for discriminating between, and accurately identifying, mental states. Here, we present compelling evidence that the efficacy of these decoders is overstated. Across a variety of tasks, decoder patterns were not necessary. Not only were "optimized decoders" spatially imprecise and 90% redundant, but they also performed similarly to simpler decoders, built from average brain activity. We distinguish decoder performance when used for discriminating between, in contrast to identifying, mental states, and show even when discrimination performance is strong, identification can be poor. Using similarity rules, we derived novel and intuitive discriminability metrics that capture 95% and 68% of discrimination performance within- and across-subjects, respectively. These findings demonstrate that current across-subject decoders remain inadequate for real-life decision making.

neuroscience↗

bioRxiv2019

Ultra-low frequency neural entrainment to pain

Nervous systems exploit regularities in the sensory environment to predict sensory input and adjust behavior, and thereby maximize fitness. Entrainment of neural oscillations allows retaining temporal regularities of sensory information, a prerequisite for prediction. Entrainment has been extensively described at the frequencies of periodic inputs most commonly present in visual and auditory landscapes (e.g. >1 Hz). An open question is whether neural entrainment also occurs for regularities at much longer timescales. Here we exploited the fact that the temporal dynamics of thermal stimuli in natural environment can unfold very slowly. We show that ultra-low frequency neural oscillations preserved a long-lasting trace of sensory information through neural entrainment to periodic thermo-nociceptive input as low as 0.1 Hz. Importantly, revealing the functional significance of this phenomenon, both power and phase of the entrainment predicted individual pain sensitivity. In contrast, periodic auditory input at the same ultra-low frequency did not entrain ultra-low frequency oscillations. These results demonstrate that a functionally-significant neural entrainment can occur at temporal scales far longer than those commonly explored. The non-supramodal nature of our results suggests that ultra-low frequency entrainment might be tuned to the temporal scale of the statistical regularities characteristic of different sensory modalities.

neuroscience↗

bioRxiv2018

Preserved cortical maps of the body in Complex Regional Pain Syndrome

Chronic pain can be associated with functional and morphological changes in the brain. It has long been thought that some severe chronic pain conditions, such as Complex Regional Pain Syndrome (CRPS), are not only associated with, but even maintained by a reorganisation of the somatotopic representation of the affected limb in the primary somatosensory cortex (S1). This notion has driven treatments that aim to restore S1 representations, such as sensory discrimination training and mirror therapy. However, this notion is based on both indirect and incomplete evidence obtained with imaging methods with low spatial resolution. Here, we used functional MRI to characterize the S1 representation of the affected and unaffected hand in patients with unilateral CRPS of one hand. Our study demonstrates that the cortical area, location, and geometry of the S1 representation of the CRPS hand are comparable to those of the healthy hand, as well as to those of controls. Given that S1 representations are largely preserved in CPRS patients, it is compelling to reconsider not only the cortical mechanisms that underlie the disorder, but also the rationale for interventions that aim to \"restore\" somatotopic representations.

neuroscience↗