Biology subjects

Toso, A.

Publications and source records attributed to Toso, A..

8 recordsLinked to original sources

bioRxiv2026

Independent history traces for distinct percepts derived from a single stimulus

Perception is more than a direct readout of current sensory input; it is also shaped by recent experience, a phenomenon known as serial dependence. While the effects of recent experience have been well characterized for single stimulus features, it remains unclear how perceptual history operates when multiple perceptual dimensions must be extracted from a single sensory event. Here, human participants reported their judgment of vibrotactile stimuli, with the relevant feature - either the intensity or duration - randomly cued on each trial. Within trials, intensity and duration interacted bidirectionally - longer stimuli were perceived as stronger and stronger stimuli as longer - indicating that both features are derived from a shared sensory representation. Across trials, however, serial dependence was feature-specific: perceived intensity was selectively attracted toward previously perceived intensities, and perceived duration toward previously perceived durations. The current trial judgment was influenced by perceptual estimates from multiple preceding trials, but only those in which the same feature was task-relevant. We formalize these findings with a computational model in which perceptual history is maintained in parallel memory traces, each selectively updated when the corresponding feature is task-relevant. The model captured both the psychometric structure of behavior and the feature-specific, multi-trial dependence of perceptual judgments, with traces that accumulate past percepts and bias current estimates along the corresponding feature dimension.Serial dependence in this task operates on perceptual representations downstream of a shared sensory encoding stage, and is maintained simultaneously in feature-specific, task-gated memory traces within higher-level cortical circuits.

neuroscience↗

bioRxiv2026

Palaeoproteomic deconvolution of physical and genetic collagen mixtures

Species identification in palaeoproteomics relies on genome-derived protein sequences which are often poor-quality, and lacks tools to cope with multi-species samples. Here, we address both challenges through the analysis of physical and genetic mixtures. Species that are absent from our database are considered a genetic mixture, i.e. a patchwork of peptides from closely related species. Inversely, various overlapping peptide stretches allow us to resolve complex physical mixtures. This is benchmarked by analysing physical mixtures of modern bone fragments, including genetic mixtures. We illustrate the impact of our approach via a rapid and high-throughput analysis of >2500 bone fragments, revealing the Eemian-era faunal environment around Scladina Cave, including the first Palaeoloxodon antiquus identified at this site. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/732552v1_ufig1.gif" ALT="Figure 1"> View larger version (67K): org.highwire.dtl.DTLVardef@a33296org.highwire.dtl.DTLVardef@4e4b85org.highwire.dtl.DTLVardef@402290org.highwire.dtl.DTLVardef@9d35b6_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

History-dependent Biases in Perceptual Decisions Depend on NMDA Receptors

Perceptual decisions are governed not only by current sensory input but also by the history of previous stimuli, choices, or outcomes. Such history-dependent biases evolve across multiple timescales ranging from seconds to minutes. Synaptic plasticity is one possible mechanism mediating such effects. The by N-methyl-aspartate (NMDA) glutamate receptor is critical for synaptic plasticity, and indirect evidence points to its role in the generation of history-dependent biases. Here, we pharmacologically blocked NMDA receptors in healthy human participants performing a two-alternative visual decision-making task. Participants choices were biased by the accumulation of fluctuating sensory evidence within each trial as well as the accumulation of across-trial sequences of stimuli, which enabled them to adapt to changing stimulus statistics across blocks. NMDA receptor blockade reduced the task-adaptive across trials, history-dependent biases. In contrast, enhancing GABA-A receptor activity in the same participants increased the transiency of the within-trial evidence accumulation dynamics. Our findings provide direct evidence for the importance of NMDA receptor function in history-dependent biases in the human brain.

neuroscience↗

bioRxiv2025

Competing Neural Decision Variables in Human Frontal Cortex Shape Decision Confidence

Theories of the neural basis of decision-making postulate a competition between choice-selective populations of neurons that are distributed across many brain areas. We hypothesized that agents sense of confidence in a choice is shaped by the consensus among these distributed decision signals. To test this idea, we simultaneously tracked the dynamics of choice-selective signals within each of many cortical areas via magnetoencephalography, while human participants formed difficult decisions. Signals within premotor cortex that supported the choice option selected on a given trial, or the alternative, exhibited a signature of intra-cortical competition. Both competing neural signals made opposing and unique contributions to confidence. Critically, the number and strength of choice-selective signals in associative cortical areas supporting the selected option on each trial made an additional contribution to confidence. We conclude that confidence emerges from cortex-wide, competitive dynamics, through a mechanism that monitors the consensus across many local decision modules.

neuroscience↗

bioRxiv2025

Notes on the diet and size of Cassiopea

Medusae of the genus Cassiopea are common components of tropical and subtropical coastlines globally. Despite the broad distribution of this benthic scyphozoan, much about their ecology remains poorly described. Here, we collected over 100 adult Cassiopea individuals from Panama, the eastern United States, Cuba, the Philippines, Italy and Australia to examine continuity and differences in their diet across space, and to investigate whether their unique lifestyle is reflected in their diet. We found the majority of prey items to be associated with the epibenthos. The recovered prey were supermajority crustaceans, mainly harpacticoid copepods, with pteropods, nematodes, and miscellaneous eggs common as secondary components. Within the gastrovascular cavity of a single medusa, we found up to 379 items. There was a limited relationship between medusa size and prey items. Location had an impact on gut content diversity and medusa size had a small impact on the number of taxa found within the gut. In some sites, prey were scarce or absent from all medusae sampled. Overall, we reaffirm the diet previously recorded for small medusae in Puerto Rico and show that similar components are common in large and small medusae from throughout the East and West Atlantic and the Philippines.

ecology↗

bioRxiv2024

Large-scale Dynamical Fingerprints of Distributed Synaptic Alterations in Early-Stage Psychosis

Psychotic disorders, such as schizophrenia, present a major challenge for research and clinical practice: its pathogenesis is complex, the individual symptomatology is heterogenous, and there is a lack of biomarkers for the early detection, diagnosis, and individualized treatment. Mounting evidence indicates that the synaptic and microcircuitry alterations underlying psychosis are widely distributed in the brain. Here, we developed a magnetoencephalography approach to map the resulting alterations of local cortical population dynamics across the human cerebral cortex. We identified large-scale patterns of changes in neural dynamics that were remarkably similar between first-episode psychosis patients and individuals at clinical high risk for psychosis. These spatial patterns also resembled those induced by pharmacological manipulations of excitatory NMDA glutamate receptors and inhibitory GABA-A receptors in healthy participants. Differences in those spatial patterns of cortical dynamics between psychosis patients related to individual symptomatology. Our study opens a new window on the distributed pathophysiology of psychosis. TeaserCortex-wide changes in neural mass dynamics due to psychosis resemble changes due to GABA-A or NMDA receptor manipulation and relate to clinical symptoms.

neuroscience↗

bioRxiv2023

40 Hz Steady-State Responses in Human Auditory Cortex Depend on GABAergic Neuronal Inhibition

The 40 Hz auditory steady-state response (ASSR), an oscillatory brain response to periodically modulated auditory stimuli, is a promising, non-invasive physiological biomarker for schizophrenia and related neuropsychiatric disorders. The 40 Hz ASSR might be amplified by synaptic interactions in cortical circuits, which are, in turn, disturbed in neuropsychiatric disorders. Here, we tested whether the 40 Hz ASSR in human auditory cortex depends on two key synaptic components of neuronal interactions within cortical circuits: excitation via N-methyl-aspartate glutamate (NMDA) receptors and inhibition via gamma-amino-butyric acid (GABA) receptors. We combined magnetoencephalography (MEG) recordings with placebo-controlled, low-dose pharmacological interventions in the same healthy human participants. All participants exhibited a robust 40 Hz ASSR in auditory cortices, especially in the right hemisphere, under placebo. The GABAA receptor-agonist lorazepam increased the amplitude of the 40 Hz ASSR, while no effect was detectable under the NMDA-blocker memantine. Our findings indicate that the 40 Hz ASSR in auditory cortex involves synaptic (and likely intracortical) inhibition via the GABA-A receptor, thus highlighting its utility as a mechanistic signature of cortical circuit dysfunctions involving GABAergic inhibition. Significance statementThe 40 Hz auditory steady-state response is a candidate non-invasive biomarker for schizophrenia and related neuropsychiatric disorders. Yet, the understanding of the synaptic basis of this neurophysiological signature in humans has remained incomplete. We combined magnetoencephalography (MEG) recordings with placebo-controlled pharmacological interventions in healthy human subjects to test the modulation of the 40 Hz ASSR in auditory cortex by two synaptic components that have been implicated in the generation of neuronal oscillations in cortical microcircuits: glutamate N-methyl-aspartate glutamate (NMDA) receptors and gamma-amino-butyric acid (GABA) -A receptors. Boosting GABAergic transmission, but not blocking NMDA-receptors, increased the amplitude of this ASSR. Thus, GABAergic inhibition modulates 40 Hz steady-state responses in auditory cortex.

neuroscience↗

bioRxiv2020

A sensory integration account for time perception

The connection between stimulus perception and time perception remains unknown. The present study combines human and rat psychophysics with sensory cortical neuronal firing to construct a computational model for the percept of elapsed time embedded within sense of touch. When subjects judged the duration of a vibration applied to the fingertip (human) or whiskers (rat), increasing stimulus mean speed led to increasing perceived duration. Symmetrically, increasing vibration duration led to increasing perceived intensity. We modeled spike trains from vibrissal somatosensory cortex as input to dual leaky integrators - an intensity integrator with short time constant and a duration integrator with long time constant - generating neurometric functions that replicated the actual psychophysical functions of rats. Returning to human psychophysics, we then confirmed specific predictions of the dual leaky integrator model. This study offers a framework, based on sensory coding and subsequent accumulation of sensory drive, to account for how a feeling of the passage of time accompanies the tactile sensory experience.

neuroscience↗