External Sensory Input Research Articles

Synchrony dynamics underlie irregular neocortical spiking.

Cortical neurons are characterized by their variable spiking patterns. We challenge prevalent theories for the origin of spiking variability. We examine the specific hypothesis that cortical synchrony drives spiking variability in vivo . Using dynamic clamp, we demonstrate that intrinsic neuronal properties do not contribute substantially to spiking variability, but rather spiking variability emerges from weakly synchronous network drive. With large-scale electrophysiology we quantify the degree of synchrony and its time scale in cortical networks in vivo . We demonstrate that physiological levels of synchrony are sufficient to generate irregular responses found in vivo . Further, this synchrony shifts over timescales ranging from 25 to 200 ms, depending on the presence of external sensory input. Such shifts occur when the network moves from spontaneous to driven modes, leading naturally to a decline in response variability as observed across cortical areas. Finally, while individual neurons exhibit reliable responses to physiological drive, different neurons respond in a distinct fashion according to their intrinsic properties, contributing to stable synchrony across the neural network.

Sensorimotor Simulation's Influence on Stress: EEG and Autonomic Responses in Digital Interviews.

This study explored the role of sensorimotor simulation in modulating the stress response in individuals exposed to stressful digital simulated interviews. Participants were assigned to two different versions of a Digital Social Stress Test: a simulated version with a dynamic-realistic examining committee (Dyn-DSST) and a version with a static examining committee (Stat-DSST). During interview preparation, behavioral indices reflecting stress regulation and resistance, response times, and electroencephalographic (EEG) and autonomic indices were collected. Higher regulation scores were found for the Stat-DSST group compared to the Dyn-DSST group, probably induced by the presence of limited external sensory input in time and space, perceived as less stressful. The EEG results revealed a distinct contribution of the low- and high-frequency bands for both groups. Dyn-DSST required greater cognitive regulation effort due to the presence of a continuous flow of information, which can enhance sensory and motor activation in the brain. The SCR increased in the Dyn-DSST group compared to the Stat-DSST group, reflecting greater emotional involvement in the Dyn-DSST group and reduced sensory stimulation in the static version. In conclusion, the results suggest that sensorimotor simulation impacts the stress response differently in dynamic interviews compared to static ones, with distinct profiles based on behavioral, EEG, and autonomic measures.

Endogenous cannabinoids in the piriform cortex tune olfactory perception

Sensory perception depends on interactions between external inputs transduced by peripheral sensory organs and internal network dynamics generated by central neuronal circuits. In the sensory cortex, desynchronized network states associate with high signal-to-noise ratio stimulus-evoked responses and heightened perception. Cannabinoid-type-1-receptors (CB1Rs) - which influence network coordination in the hippocampus - are present in anterior piriform cortex (aPC), a sensory paleocortex supporting olfactory perception. Yet, how CB1Rs shape aPC network activity and affect odor perception is unknown. Using pharmacological manipulations coupled with multi-electrode recordings or fiber photometry in the aPC of freely moving male mice, we show that systemic CB1R blockade as well as local drug infusion increases the amplitude of gamma oscillations in aPC, while simultaneously reducing the occurrence of synchronized population events involving aPC excitatory neurons. In animals exposed to odor sources, blockade of CB1Rs reduces correlation among aPC excitatory units and lowers behavioral olfactory detection thresholds. These results suggest that endogenous endocannabinoid signaling promotes synchronized population events and dampen gamma oscillations in the aPC which results in a reduced sensitivity to external sensory inputs.

Encoding without perceiving: Can memories be implanted?

ABSTRACT The origin of memories is thought to be found in sensory perception. This conception is central to how the memory sciences characterize encoding. This paper considers how novel memory traces can be formed independently of external sensory inputs. I present a case study in which memory traces are created without sensory perception using a technique I call optogenetic memory implantation. Comparing this artificial process with normal memory encoding, I consider its implications for rethinking the causal chain that leads to remembering.

First activity and interactions in thalamus and cortex using raw single-trial EEG and MEG elicited by somatosensory stimulation.

One of the primary motivations for studying the human brain is to comprehend how external sensory input is processed and ultimately perceived by the brain. A good understanding of these processes can promote the identification of biomarkers for the diagnosis of various neurological disorders; it can also provide ways of evaluating therapeutic techniques. In this work, we seek the minimal requirements for identifying key stages of activity in the brain elicited by median nerve stimulation. We have used a priori knowledge and applied a simple, linear, spatial filter on the electroencephalography and magnetoencephalography signals to identify the early responses in the thalamus and cortex evoked by short electrical stimulation of the median nerve at the wrist. The spatial filter is defined first from the average EEG and MEG signals and then refined using consistency selection rules across ST. The refined spatial filter is then applied to extract the timecourses of each ST in each targeted generator. These ST timecourses are studied through clustering to quantify the ST variability. The nature of ST connectivity between thalamic and cortical generators is then studied within each identified cluster using linear and non-linear algorithms with time delays to extract linked and directional activities. A novel combination of linear and non-linear methods provides in addition discrimination of influences as excitatory or inhibitory. Our method identifies two key aspects of the evoked response. Firstly, the early onset of activity in the thalamus and the somatosensory cortex, known as the P14 and P20 in EEG and the second M20 for MEG. Secondly, good estimates are obtained for the early timecourse of activity from these two areas. The results confirm the existence of variability in ST brain activations and reveal distinct and novel patterns of connectivity in different clusters. It has been demonstrated that we can extract new insights into stimulus processing without the use of computationally costly source reconstruction techniques which require assumptions and detailed modeling of the brain. Our methodology, thanks to its simplicity and minimal computational requirements, has the potential for real-time applications such as in neurofeedback systems and brain-computer interfaces.

Active and Passive Cycling Decrease Subthalamic β Oscillations in Parkinson's Disease.

Preserved cycling capabilities in patients with Parkinson's disease, especially in those with freezing of gait are still poorly understood. Previous research with invasive local field potential recordings in the subthalamic nucleus has shown that cycling causes a stronger suppression of β oscillations compared to walking, which facilitates motor continuation. We recorded local field potentials from 12 patients with Parkinson's disease (six without freezing of gait, six with freezing of gait) who were bilaterally implanted with deep brain stimulation electrodes in the subthalamic nucleus. We investigated β (13-30 Hz) and high γ (60-100 Hz) power during both active and passive cycling with different cadences and compared patients with and without freezing of gait. The passive cycling experiment, where a motor provided a fixed cadence, allowed us to study the effect of isolated sensory inputs without physical exercise. We found similarly strong suppression of pathological β activity for both active and passive cycling. In contrast, there was stronger high γ band activity for active cycling. Notably, the effects of active and passive cycling were all independent of cadence. Finally, β suppression was stronger for patients with freezing of gait, especially during passive cycling. Our results provide evidence for a link between proprioceptive input during cycling and β suppression. These findings support the role of continuous external sensory input and proprioceptive feedback during rhythmic passive cycling movements and suggest that systematic passive mobilization might hold therapeutic potential. © 2023 International Parkinson and Movement Disorder Society.

Prominent in vivo influence of single interneurons in the developing barrel cortex.

Spontaneous synchronous activity is a hallmark of developing brain circuits and promotes their formation. Ex vivo, synchronous activity was shown to be orchestrated by a sparse population of highly connected GABAergic 'hub' neurons. The recent development of all-optical methods to record and manipulate neuronal activity in vivo now offers the unprecedented opportunity to probe the existence and function of hub cells in vivo. Using calcium imaging, connectivity analysis and holographic optical stimulation, we show that single GABAergic, but not glutamatergic, neurons influence population dynamics in the barrel cortex of non-anaesthetized mouse pups. Single GABAergic cells mainly exert an inhibitory influence on both spontaneous and sensory-evoked population bursts. Their network influence scales with their functional connectivity, with highly connected hub neurons displaying the strongest impact. We propose that hub neurons function in tailoring intrinsic cortical dynamics to external sensory inputs.

Postural stability and plantar pressure parameters in healthy subjects: variability, correlation analysis and differences under open and closed eye conditions.

Introduction: The "postural control system" acts through biomechanical strategies and functional neuromuscular adaptations to maintain body balance under static and dynamic conditions. Postural stability and body weight distribution can be affected by external sensory inputs, such as different visual stimuli. Little information is available about the influence of visual receptors on stabilometric and plantar pressure parameters. The aim of this study was to analyze variability, correlations, and changes in these parameters under open- (OE) and closed-eye (CE) conditions. Methods: A total of 31 stabilometric and plantar pressure parameters were acquired in 20 young and healthy adults during baropodometric examination performed in bipedal standing under both visual conditions. Variability of parameters was evaluated via the coefficient of variation, correlation analysis via Pearson's R2, and statistical differences via the Wilcoxon test. Results: High intra-subject repeatability was found for all plantar pressure parameters and CoP-speed (CV < 40%) under OE and CE conditions, while CoP-sway area (CoPsa) and length surface function (LSF) showed larger variability (CV > 50%). Mean and peak pressures at midfoot and total foot loads showed the least number of significant correlations with other parameters under both visual conditions, whereas the arch-index and rearfoot loads showed the largest number of significant correlations. The limb side significantly affected most plantar pressure parameters. A trend of larger LSF and lower CoPsa and mean and peak pressures at the right forefoot was found under the CE condition. Discussion: The present study provides a deeper insight into the associations between postural stability and foot load. Interesting postural adaptations, particularly with respect to different visual stimuli, the effect of the dominant side, and the specific role of the midfoot in balance control were highlighted.

Reduced Environmental Stimulation Therapy (REST) in anxiety and depression: An experience sampling study

BackgroundReduced Environmental Stimulation Therapy (REST) is a behavioral intervention that systematically attenuates external sensory input to the nervous system. Previous studies have demonstrated acute anxiolytic and antidepressant effects of single sessions of REST in anxious individuals, however the duration and time course of these effects is unknown. In the current study, we used experience sampling and multiple sessions of REST to explore the time course of the anxiolytic and antidepressant effects over a 48-hour time period. Methods75 adults with anxiety and/or depression were randomized to complete 6 sessions of REST (either pool-REST, pool-REST preferred, or chair-REST). Post-REST effects were tracked using experience sampling on a smartphone with a ten-item survey administered at 6 time points for each session (i.e., immediately before and after REST and then 4, 8, 24, and 48 h later). Using principal component analysis, responses to survey items at baseline were reduced to broad symptom clusters of anxiety, depression, and serenity and were utilized in linear mixed effects models to determine the magnitude and time course of post-REST effects. ResultsREST was associated with significant decreases in anxiety and depression, and significant increases in serenity, with effects lasting for 48 h. Repeated exposure to REST was associated with lower baseline levels of anxiety at later sessions. ConclusionThese initial findings suggest that the anxiolytic and antidepressant effects of REST persist for at least two days, and that repeated REST sessions may have additive effects on lowering anxiety-related symptoms. These findings could help to determine the optimal intervention frequency of REST and facilitate future investigations focused on the combination of REST with standard treatments for anxiety and depression.

Cerebellar control of a unitary head direction sense

The head-direction (HD) system, a key neural circuit for navigation, consists of several anatomical structures containing neurons selective to the animal's head direction. HD cells exhibit ubiquitous temporal coordination across brain regions, independently of the animal's behavioral state or sensory inputs. Such temporal coordination mediates a single, stable, and persistent HD signal, which is essential for intact orientation. However, the mechanistic processes behind the temporal organization of HD cells are unknown. By manipulating the cerebellum, we identify pairs of HD cells recorded from two brain structures (anterodorsal thalamus and retrosplenial cortex) that lose their temporal coordination, specifically during the removal of the external sensory inputs. Further, we identify distinct cerebellar mechanisms that participate in the spatial stability of the HD signal depending on sensory signals. We show that while cerebellar protein phosphatase 2B-dependent mechanisms facilitate the anchoring of the HD signal on the external cues, the cerebellar protein kinase C-dependent mechanisms are required for the stability of the HD signal by self-motion cues. These results indicate that the cerebellum contributes to the preservation of a single and stable sense of direction.

The Topo-Speech sensory substitution system as a method of conveying spatial information to the blind and vision impaired.

Humans, like most animals, integrate sensory input in the brain from different sensory modalities. Yet humans are distinct in their ability to grasp symbolic input, which is interpreted into a cognitive mental representation of the world. This representation merges with external sensory input, providing modality integration of a different sort. This study evaluates the Topo-Speech algorithm in the blind and visually impaired. The system provides spatial information about the external world by applying sensory substitution alongside symbolic representations in a manner that corresponds with the unique way our brains acquire and process information. This is done by conveying spatial information, customarily acquired through vision, through the auditory channel, in a combination of sensory (auditory) features and symbolic language (named/spoken) features. The Topo-Speech sweeps the visual scene or image and represents objects' identity by employing naming in a spoken word and simultaneously conveying the objects' location by mapping the x-axis of the visual scene or image to the time it is announced and the y-axis by mapping the location to the pitch of the voice. This proof of concept study primarily explores the practical applicability of this approach in 22 visually impaired and blind individuals. The findings showed that individuals from both populations could effectively interpret and use the algorithm after a single training session. The blind showed an accuracy of 74.45%, while the visually impaired had an average accuracy of 72.74%. These results are comparable to those of the sighted, as shown in previous research, with all participants above chance level. As such, we demonstrate practically how aspects of spatial information can be transmitted through non-visual channels. To complement the findings, we weigh in on debates concerning models of spatial knowledge (the persistent, cumulative, or convergent models) and the capacity for spatial representation in the blind. We suggest the present study's findings support the convergence model and the scenario that posits the blind are capable of some aspects of spatial representation as depicted by the algorithm comparable to those of the sighted. Finally, we present possible future developments, implementations, and use cases for the system as an aid for the blind and visually impaired.

Autism, hypersensitivity and language ability

A study with 36 German participants (divided in 3 age groups: 1 gr. 7-11 years; 2 gr. 12-18 years and 3 gr. 19-50 years) was conducted to test the Polyvagal Theory. Our data analysis evaluated a therapeutic intervention using the so-called SSP (Safe and Sound Protocol) developed by Stephen Porges. Frequency modulated music stimulates the parasympathetic vagus nerve with an (musical) input process evaluated by the brain as socially-communicatively salient (musical signals with enhanced prosodic characteristics of human voices). Thus, acoustical processes of (musical) perception become available to the brain's assessment of social signals via the neurophysiology of the ANS. This, in turn, allows for internally processed signals of social safety, resulting in a reduced sense of stress from external sensory inputs. The SSP aims to generally reduce sensory hypersensitivity by stimulating the vagus nerve via the middle ear – and thus, to contribute to a better capacity of (down)-regulating sensory hypersensitivity. In the current study, we demonstrated that participants with ASD showed reduced hyper-sensitivity (visual, auditory, tactile and digestive) after using the SSP. In a second data analysis, we tested the overall impact of language ability and the influence on hyper sensory sensitivity in the autism spectrum. It seems that language ability in general already leads to better regulation and integration of sensory inputs via cognitive-linguistic processing in cortex areas: if a strong sensory stimulus can be assigned and evaluated linguistically, the strength of the stimulus is adjusted thereby. Conversely, different language abilities did not result in a more effective response to the SSP. Since the SSP amplifies prosodic elements of human speech in a characteristic way, the effect of reduced sensitivity to stimuli seems to be due to the autonomic response to paraverbal signals. The results are statistically analyzed using ANOVA.

A proposed attention-based model for spatial memory formation and retrieval.

Animals use sensory information and memory to build internal representations of space. It has been shown that such representations extend beyond the geometry of an environment and also encode rich sensory experiences usually referred to as context. In mammals, contextual inputs from sensory cortices appear to be converging on the hippocampus as a key area for spatial representations and memory. How metric and external sensory inputs (e.g., visual context) are combined into a coherent and stable place representation is not fully understood. Here, I review the evidence of attentional effects along the ventral visual pathway and in the medial temporal lobe and propose an attention-based model for the integration of visual context in spatial representations. I further suggest that attention-based retrieval of spatial memories supports a feedback mechanism that allows consolidation of old memories and new sensory experiences related to the same place, thereby contributing to the stability of spatial representations. The resulting model has the potential to generate new hypotheses to explain complex responses of spatial cells such as place cells in the hippocampus.

Exploring the acute cardiovascular effects of Floatation-REST.

[https://clinicaltrials.gov/show/NCT03051074], identifier [NCT03051074].

Chemosensation: Corollary discharge filters out self-generated chemical cues

Corollary discharge allows organisms to discriminate external sensory inputs from self-generated cues. However, the underlying synaptic and molecular mechanisms are not well understood. A new study has identified a tyraminergic corollary discharge signal that extrasynaptically modulates chemosensory neurons in Caenorhabditis elegans.

Spatiotemporal patterns of spontaneous brain activity: a mini-review.

.The brain exists in a state of constant activity in the absence of any external sensory input. The spatiotemporal patterns of this spontaneous brain activity have been studied using various recording and imaging techniques. This has enabled considerable progress to be made in elucidating the cellular and network mechanisms that are involved in the observed spatiotemporal dynamics. This mini-review outlines different spatiotemporal dynamic patterns that have been identified in four commonly used modalities: electrophysiological recordings, optical imaging, functional magnetic resonance imaging, and electroencephalography. Signal sources for each modality, possible sources of the observed dynamics, and future directions are also discussed.

Diagnosing Disease with Multifractality

The resting activity of the heart, without external sensory input, has provided novel information on the interactions that occur between biological and entropic systems in the body. The intersection between multifractality and disease diagnosis has been extensively worked on in the biophysical field, and yet, it is one that still has a lot of potential for new discoveries. In this paper, I will attempt to briefly describe the current literature on the use of multifractality on disease diagnosis, in addition to briefly comment on the future of this diagnostic methodology in the fight against cancer. A fractal is described as a never-ending pattern, one that is infinitely complex and seems to repeat a process over and over in a loop. Fractals exhibit self-similarity, meaning they are patterns that are identical or near-identical on many scales, including time scales. In the context of this paper, fractals are visible patterns in the heartbeat 1[Formula: see text]s into a time series that will also be visible 1 day into a time series. This self-similarity is described by exponents. For example, monofractal processes only scale fractally in one manner, meaning that one exponent will help define them mathematically. On a graph of a power law over time, a monofractal state would present as a linear curve, as one exponent is defining it. Multifractality, on the other hand, is a term defining a spectrum of exponents used to help mathematically define a natural state. It would present as a nonlinear curve on the graph of a power law, as multiple exponents of multiple orders are describing its self-similarity over time. 1 A heartbeat time series, in this paper, will be defined as 1800 evenly-spaced measurements of heart rate from one patient.5 In addition, the term crucial renewal events, also called crucial events, will be defined as events in a heartbeat time series that store the long-term memory of the heartbeat, therefore impacting the future patterns of the heartbeat. Crucial events build upon each other, meaning that the occurrence of earlier crucial events will correlate to the occurrence of subsequent crucial events. Over time, a decrease in the correlation between crucial events would indicate the presence of Poisson-like events, which in this paper will be defined as a disturbance in the healthy physiological process of a heartbeat. 3 The concept that multifractality and crucial events may play a role in disease diagnosis has been presented in different ways in the past. The first method was through broad multifractal spectrum analysis, in which Ivanov et al. determined that a loss of multifractality occurs in a non-healthy state, specifically when they analyzed congestive heart failure. This finding suggested that the presence of pathology moved the heartbeat closer to a monofractal state, making the difference between healthy and pathological individuals easy to identify. 2 The second method, presented later on, presented evidence that healthy patients were less likely to have unrelated Poisson-like events than diseased or unhealthy patients. Crucially, West and Grigolini in 2017 were able to find an intersection between these two methods by proving that increasing the percentage of unrelated Poisson-like events occurring in a system would directly correlate to a narrower multifractal spectrum, connecting the two diagnostic methods and providing a view of multifractality such that it could have a drastic impact on potential diagnosis methodologies in the future. 3 , 4

Real Bodies Not Required? Placebo Analgesia and Pain Perception in Immersive Virtual and Augmented Reality

Pain represents an embodied experience, wherein inferences are not only drawn from external sensory inputs, but also from bodily states. Previous research has demonstrated that a placebo administered to an embodied rubber hand can effectively induce analgesia, providing first evidence that placebos can work even when applied to temporarily embodied, artificial body parts. Using a heat pain paradigm, the present study investigates placebo analgesia and pain perception during virtual embodiment. We examined whether a virtual placebo (a sham heat protective glove) can successfully induce analgesia, even when administered to a virtual body. The analgesic efficacy of the virtual placebo to the real hand (augmented reality setting) or virtual hand (virtual reality setting) was compared to a physical placebo administered to the own, physical body (physical reality setting). Furthermore, pain perception and subjective embodiment were compared between settings. In this mixed design experiment, healthy participants (n = 48) were assigned to either an analgesia-expectation or control-expectation group, where subjective and objective pain was measured at pre- and post-intervention time points. Results demonstrate that pre-intervention pain intensity was lower in the virtual reality setting, and that participants in the analgesia-expectation group, after the intervention, exhibited significantly higher pain thresholds, and lower pain intensity and unpleasantness ratings than control-expectation participants, independent of the setting. Our findings show that a virtual placebo can elicit placebo analgesia comparable to that of a physical placebo, and that administration of a placebo does not necessitate physical bodily interaction to produce analgesic responses. PerspectiveThis study demonstrates that a virtual placebo treatment, even when administered to a virtual body, can produce placebo analgesia. These findings indicate that the efficacy of a virtual placebo is comparable to that of a physical placebo, which could pave the way for effective new non-pharmacological approaches for pain management.

Shielding working-memory representations from temporally predictable external interference

Protecting working-memory content from distracting external sensory inputs and intervening tasks is an ubiquitous demand in daily life. Here, we ask whether and how temporal expectations about external events can help mitigate effects of such interference during working-memory retention. We manipulated the temporal predictability of interfering items that occurred during the retention period of a visual working-memory task and report that temporal expectations reduce the detrimental influence of external interference on subsequent memory performance. Moreover, to determine if the protective effects of temporal expectations rely on distractor suppression or involve shielding of internal representations, we compared effects after irrelevant distractors that could be ignored vs. interrupters that required a response. Whereas distractor suppression may be sufficient to confer protection from predictable distractors, any benefits after interruption are likely to involve memory shielding. We found similar benefits of temporal expectations after both types of interference. We conclude that temporal expectations may play an important role in safeguarding behaviour based on working memory – acting through mechanisms that include the shielding of internal content from external interference.

LSD degrades hippocampal spatial representations and suppresses hippocampal-visual cortical interactions.

Lysergic acid diethylamide (LSD) produces hallucinations, which are perceptions uncoupled from the external environment. How LSD alters neuronal activities invivo that underlie abnormal perceptions is unknown. Here, we show that when rats run along a familiar track, hippocampal place cells under LSD reduce their firing rates, their directionality, and their interaction with visual cortical neurons. However, both hippocampal and visual cortical neurons temporarily increase firing rates during head-twitching, a behavioral signature of a hallucination-like state in rodents. When rats are immobile on the track, LSD enhances cortical firing synchrony in a state similar to the wakefulness-to-sleep transition, during which the hippocampal-cortical interaction remains dampened while hippocampal awake reactivation is maintained. Our results suggest that LSD suppresses hippocampal-cortical interactions during active behavior and during immobility, leading to internal hippocampal representations that are degraded and isolated from external sensory input. These effects may contribute to LSD-produced abnormal perceptions.