Biology subjects

Silvanto, J.

Publications and source records attributed to Silvanto, J..

10 recordsLinked to original sources

bioRxiv2026

How the Body Shapes the Mind's Eye: Cardiac vagal reactivity predicts visual imagery vividness

Mental imagery is known to be accompanied by autonomic responses, traditionally viewed as merely downstream consequences of imagery. Recent theoretical work has challenged this view, proposing that mental imagery requires the integration of cortical sensory representations with ascending interoceptive signals supplied by the autonomic nervous system. These two views make opposite predictions: if autonomic activity is only a consequence of imagery, then the responsiveness of the autonomic nervous system should not predict imagery vividness. If instead autonomic input shapes the generation of mental images, individuals with greater autonomic responsiveness should experience more vivid imagery. The present study tested these competing predictions by examining whether individual differences in cardiac vagal reactivity predict self-reported visual imagery vividness, with imagery assessed at a separate time point from the paced breathing protocol. Cardiac vagal reactivity significantly predicted VVIQ scores after controlling for factors such as resting HRV, respiratory amplitude, age and negative affect (b = 13.75, p = .022; model R2 = 0.12), whereas neither baseline HRV nor fast-breathing evoked HRV change were linked to imagery, suggesting the effect is specific to the capacity to enter a high parasympathetic state rather than reflecting general autonomic capacity. Self-reported interoceptive noticing (MAIA Noticing) was significantly associated with both delta HRV and VVIQ, suggesting that cardiac vagal reactivity and imagery vividness are linked through a broader individual difference in interoceptive function. These findings indicate that the vividness of mental imagery is not exclusively central in origin but also appears to be shaped by the capacity of the autonomic nervous system to enter a high parasympathetic state. Imagery thus likely involves bidirectional interaction between cortical and autonomic processes, with descending efferent pathways activating autonomic responses while ascending interoceptive signals contributing to the construction of mental images.

physiology↗

bioRxiv2026

Cardio-respiratory coordination during memory encoding predicts performance

Cardiorespiratory coupling (i.e., the phase synchronization between cardiac and respiratory rhythms) varies with physiological state, but whether coupling strength functionally predicts cognitive performance remains unknown. Here we demonstrate that cardiorespiratory coupling predicts trial-level accuracy during the initial formation of mental representations but not during their subsequent retention, revealing temporal specificity in the relationship between bodily rhythms and cognition. We experimentally manipulated coupling via paced breathing (slow: 6 bpm vs. fast: 20 bpm) while participants performed mental imagery and working memory tasks with continuous physiological monitoring. Slow breathing enhanced parasympathetic activity (respiratory sinus arrhythmia), which strengthened baseline cardiorespiratory coupling. This coordinated autonomic state persisted into subsequent cognitive trials, predicting trial-by-trial accuracy specifically during the initial encoding phase when internal representations were actively constructed, but not during subsequent maintenance when representations were sustained. This temporal dissociation indicates that cardiorespiratory coordination selectively predicts performance when the brain constructs internal representations under elevated processing demands. Experimental manipulation of breathing improved behavioral accuracy, validating couplings functional relevance. These findings establish cardiorespiratory coupling as a physiological state marker that reliably predicts encoding success, providing a measurable target for interventions targeting memory and mental representation.

physiology↗

bioRxiv2026

Opposing Autonomic Pathways Link Childhood Trauma to Mental Imagery Deficits

Although childhood trauma alters neurobiological systems supporting emotion regulation and autonomic function, mechanisms linking trauma to mental imagery deficits remain unexplored. Here we examined whether autonomic nervous system symptoms mediate trauma-imagery associations in a general population sample (n = 433). All trauma types showed associations with reduced imagery vividness (r = -.12 to -.23), with emotional neglect and emotional abuse demonstrating the strongest effects. Physical trauma types and emotional abuse correlated with increased autonomic symptoms (r = .35-.38). Parallel mediation analyses revealed that autonomic symptom burden (BPQ ANS subscale), but not anxiety, significantly mediated trauma-imagery relationships through opposing mechanisms. Physical trauma types and emotional abuse showed negative indirect effects through heightened autonomic reactivity, with complete mediation for emotional abuse and physical neglect. In contrast, emotional neglect showed a positive indirect effect through reduced autonomic reactivity (a pattern that emerged when controlling for other trauma types) alongside the strongest direct effect on imagery. These findings demonstrate that childhood trauma impacts mental imagery through distinct autonomic mechanisms--hyperreactive dysregulation for physical/emotional abuse versus hyporeactive blunting for emotional neglect--suggesting autonomic-targeted interventions should be tailored to trauma type.

neuroscience↗

bioRxiv2025

Targeted Neuromodulation of Perceptual Decision-Making Networks Causally Dissociates Sensory and Metacognitive performance

Perceptual judgements and their subjective evaluation (i.e., metacognition) are considered tightly coupled aspects of decision-making. Yet, emerging evidence suggests that distinct neural mechanisms underlie these processes. In motion perception, studies have identified a neural network involving visual and associative parietal areas supporting these abilities. Whilst early (V1/V2) and specialized (V5/MT+) visual areas are associated with motion discrimination accuracy, the intraparietal sulcus (IPS/LIP) plays a critical role in the formation of subjective confidence for sensory decision, given its functionally coupling with the V5/MT+-V1/V2 network. Previous studies have consistently reported that increasing connectivity in the human V5/MT+-to-V1/V2 pathway by means of cortico-cortical paired associative stimulation (ccPAS) - a neurostimulation protocol inducing Hebbian-like changes in neuronal pathways - improves our perceptual ability to discriminate motion. Notably, we recently demonstrated that strengthening V5/MT+ influence over V1/V2 also leads to overconfidence - altering metacognitive bias for motion discrimination, suggesting that the manipulation of V5/MT+-V1/V2 network might functionally affect IPS/LIP activity. Here, we directly investigated this possibility by first strengthening the V5/MT+-V1 pathway with ccPAS, and subsequently interfering with IPS/LIP activity by means of continuous theta-burst stimulation (cTBS). In line with previous evidence, our results corroborate that enhancing V5/MT+-V1/V2 connectivity affects both motion discrimination and metacognitive bias. Crucially, IPS/LIP disruption through cTBS selectively affects metacognitive performance while leaving motion discrimination unaltered. These findings highlight distinct neural substrates for perceptual sensitivity and visual metacognition linked to V5/MT+ and IPS/LIP, respectively, opening to potential tailored applications of non-invasive brain stimulation (NIBS) to functionally improve sensory and metacognitive decision-making processes.

neuroscience↗

bioRxiv2024

Concurrent maintenance of visual imagery and short-term memory provides evidence for their distinct representations

Recent research indicates there is overlap in the neural resources used during imagery and visual short-term memory. But do visual short-term memory and visual imagery operate on similar representations during recall? Here we investigated this question by asking participants to perform a delayed match to sample task for the contrast of visual gratings as cues. In the "Imagery" condition, participants were asked to form an accurate mental image of the visual cue, and at the end of the trial, perform a matching task on the mental image contrast. In the "Memory" condition, participants were not required to perform visual imagery but merely instructed to perform the delayed contrast-matching task. In Experiment 1, participants were told at the beginning of each block whether to engage in memory or imagery. The results showed that for the relevant contrast feature, matching judgments were more accurately in the "Memory" than in the "Imagery" condition. Thus imagery did not maintain an accurate representation of the encoded image, even when the visual features could still be maintained in visual short-term memory. In Experiment 2, participants were required to engage in memory and imagery simultaneously, and were told which to base their judgment on after each trial. The key finding was that the superior accuracy for memory over imagery remained, indicating that the contents of VSTM and imagery are based on distinct representations.

neuroscience↗

bioRxiv2024

The causal role of early visual cortex in vividness of visual imagery

While numerous studies have demonstrated objective accuracy in visual imagery tasks to involve the early visual cortex (V1/V2), the role of this region in imagery vividness remains unclear. We addressed this question by combining Transcranial Magnetic Stimulation (TMS) with a cross-adaptation paradigm in which visual adaptation modulates the ability to engage in visual imagery in the adapted part of the visual field. As previously shown, in the control (Vertex) condition, mental imagery accuracy was impaired when the mental image was generated in the adapted region of visual space. This effect was removed by TMS, indicating that the locus of adaptation was the early visual cortex. In contrast, analysis of vividness ratings (collected on trial-by-trial basis) showed no effects of adaptation, indicating that the imagery vividness is somewhat orthogonal to the fidelity of the mental image. The key finding was that TMS impacted vividness ratings on trials when participants performed incorrectly in the imagery task. Thus, the effects of TMS on accuracy and vividness were observed on different trial types: TMS impaired accuracy of trials associated with high baseline performance, but increased vividness on incorrect trials. Overall, our findings suggest that the early visual cortex plays a role in both accuracy and vividness of mental images, yet these processes are dissociable.

neuroscience↗

bioRxiv2024

Vividness of Visual Imagery Supported by Intrinsic Structural-Functional Brain Network Dynamics

Vividness of visual imagery is subject to individual variability, a phenomenon with largely unexplored neurobiological underpinnings. By analyzing data from 273 participants we explored the link between the structural-functional organization of brain connectomes and the reported intensity of visual imagery (measured with VVIQ-2). Employing graph theory analyses we investigated both the structural (DTI) and functional (rs-fMRI) connectomes within a network of regions often implicated in visual imagery. Our results indicate a relationship between increased local efficiency and clustering coefficients in the structural connectome in individuals who experience more vivid visual imagery. Increased local efficiency and clustering coefficients were mirrored in the functional connectome with increases in left inferior temporal regions, a region frequently identified as a critical hub in the visual imagery literature. Furthermore, individuals with more vivid imagery were found to have lower levels of global efficiency in their functional connectome. We propose that the clarity and intensity of visual imagery are optimized by a network organization characterized by heightened localized information transfer and interconnectedness. Conversely, an excessively globally integrated network might dilute the specific neural activity crucial for generating vivid visual images, leading to less locally concentrated resource allocation in key regions involved in visual imagery vividness.

neuroscience↗

bioRxiv2023

Where in the brain do internally generated and externally presented visual information interact?

Conscious experiences normally result from the flow of external input into our sensory systems. However, we can also create conscious percepts independently of sensory stimulation. These internally generated percepts are referred to as mental images, and they have many similarities with real visual percepts. Consequently, mental imagery is often referred to as "seeing in the minds eye". While the neural basis of imagery has been widely studied, the interaction between internal and external sources of visual information has received little interest. Here we examined this question by using fMRI to record brain activity of healthy human volunteers while they were performing visual imagery that was distracted with a concurrent presentation of a visual stimulus. Multivariate pattern analysis (MVPA) was used to identify the brain basis of this interaction. Visual imagery was reflected in several brain areas in ventral temporal, lateral occipitotemporal, and posterior frontal cortices, with a left-hemisphere dominance. The key finding was that imagery content representations in the left lateral occipitotemporal cortex were disrupted when a visual distractor was presented during imagery. Our results thus demonstrate that the representations of internal and external visual information interact in brain areas associated with the encoding of visual objects and shapes.

neuroscience↗

bioRxiv2017

On mechanisms of Transcranial Magnetic Stimulation (TMS): How brain state and baseline performance level determine behavioral effects of TMS

The behavioral effects of Transcranial Magnetic Stimulation (TMS) can change qualitatively when stimulation is preceded by initial state manipulations such as priming or adaptation. In addition, baseline performance level of the participant has been shown to play a role in modulating the impact of TMS. Here we examined the link between these two. This was done using data from a previous study using a TMS-priming paradigm, in which, at group level, TMS selectively facilitated targets incongruent with the prime while having no statistically significant effects on other prime-target congruencies. Correlation and linear mixed-effects analyses indicated that, for all prime-target congruencies, a significant linear relationship between baseline performance and the magnitude of the induced TMS effect was present: low levels of baseline performance were associated with TMS-induced facilitations and high baseline performance with impairments. Thus as performance level increased, TMS effects turned from facilitation to impairment. The key finding was that priming shifted the transition from facilitatory to disruptive effects for targets incongruent with the prime, such that TMS-induced facilitations were obtained until a higher level of performance than for other prime-target congruencies. Given that brain state manipulations such as priming operate via modulations of neural excitability, this result is consistent with the view that neural excitability, coupled with nonlinear neural effects, underlie behavioral effects of TMS.

neuroscience↗

bioRxiv2017

Common framework for virtual lesion and state-dependent TMS: the facilitatory/suppressive range model of online TMS effects on behavior

The behavioral effects of Transcranial Magnetic Stimulation (TMS) are often nonlinear; factors such as stimulation intensity and brain state can modulate the impact of TMS on observable behavior in qualitatively different manner. Here we propose a theoretical framework to account for these effects. In this model, there are distinct intensity ranges for facilitatory and suppressive effects of TMS: low intensities facilitate neural activity and behavior whereas high intensities induce suppression. The key feature of the model is that these ranges are shifted by changes in neural excitability: consequently, a TMS intensity, which normally induces suppression, can have a facilitatory effect if the stimulated neurons are being inhibited. For example, adaptation reduces excitability of adapted neurons; the outcome is that TMS intensities which inhibit non-adapted neurons induce a facilitation on adapted neural representations, leading to reversal of adaptation effects. In conventional virtual lesion paradigms, similar effects occur because neurons not tuned to the target stimulus are inhibited. The resulting reduction in excitability can turn high intensity inhibitory TMS to low intensity facilitatory TMS for these neurons (whereas neurons tuned to the target stimulus are inhibited), leading to a reduction in signal-to-noise ratio. Thus differential excitability levels of neural populations contributing to behavior, combined with nonlinear neural effects, can explain how TMS modulates behavior.

neuroscience↗