1,720,995 research outputs found
Environmental control and psychosis-relevant traits modulate the prospective sense of agency in non-clinical individuals
No full textThe sense of agency concerns the experience of being the source of one's own actions and their consequences. An altered sense of agency can occur due to task automation and in psychosis. We tested in a non-clinical sample the hypothesis that reducing voluntary task control diminishes intentional binding as an implicit indicator of the sense of agency, possibly interacting with psychosis-relevant personality traits. Agent-device interactions were manipulated obtaining positive-control (voluntary interaction), no-control (automation), and negative-control (device-commanded interaction) groups. The main results showed reduced prospective intentional binding (predictive coding of action consequences) in the no-control and negative-control groups, compared to the positive-control group. Psychosis-like experiences covaried positively with intentional binding in the no-control group, but negatively in the negative-control group. Moreover, positive-social traits were associated with increased intentional binding in the positive-control group. These findings demonstrate the interplay between environmental and individual differences variables in establishing the implicit sense of agency
Respiratory phases modulate heartbeat-evoked cortical responses
No full textHeartbeat Evoked Responses (HERs) are EEG event-related potentials time-locked to the heartbeat that reflect the cortical processing of cardiac activity. HER amplitude has been related to various behavioural measures of interoception, but the reliability of such findings is controversial, given possible confounding effects driven by the electric cardiac field, as well as by other somatosensory or interoceptive factors. One of such interoceptive factors may be the respiratory phase. In fact, despite recent studies demonstrating optimized neural processing of incoming exteroceptive (sensory) information during inhalation, virtually nothing is known about mechanisms through which respiratory activity influences incoming interoceptive (cardiac) information. We simultaneously recorded 64-channel EEG, cardiac and respiratory activity in 20 healthy volunteers during an eyes-open resting state. We extracted HERs detected during inspiratory (when respiratory activity is at maximum) and post-expiratory (when respiratory activity is at a minimum) phases. In order to reduce cardiac field artefacts, HERs were time-locked to the T-peak and pruned with ICA-based procedures. HERs were compared performing a repeated-measures, two-tailed
cluster mass permutation test (10 000 permutations), including all time points between 80 and 350 ms post T-peak. We found that respiratory phases modulate HER amplitude, which was significantly higher during post-expiratory phases as compared to inspiratory phases, in a time window ranging from 176ms to 254ms post T-peak. This “respiratory HER effect” was detected in central and parietal areas known to be involved in various experimentally-induced HER modulations. Present finding indicates an often-unnoticed influence of respiration on cardiac interoception, suggesting increased neural processing of the heartbeat during post-expiratory phases, when respiratory interoceptive afference is at a minimum, as compared to inspiratory phases. Finally, starting from recent studies that independently showed that cardiac interoceptive accuracy increased during breath-holding and is predicted by HER amplitude, we conducted another study investigating if: i) the performance on the heartbeat tapping task changes depending on the specific respiratory
phase, and ii) these changes correlate with the “respiratory HER effect”
Toward a brain theory of meditation
No full textThe rapidly progressing science of meditation has led to insights about the neural correlates of focused attention meditation (FAM), open monitoring meditation (OMM), compassion meditation (CM) and loving kindness meditation (LKM), in terms of states and traits. However, a unified theoretical understanding of the brain mechanisms involved in meditation-related functions, including mindfulness, is lacking. After reviewing the main forms of meditation and their relationships, the major brain networks and brain states, as well as influential theoretical views of consciousness, we outline a Brain Theory of Meditation (BTM). BTM takes the lead from considerations about the roles of the major brain networks, i.e., the central executive, salience and default mode networks, and their interplay, in meditation, and from an essential energetic limitation of the human brain, such that only up to 1% of the neurons in the cortex can be concurrently activated. The development of the theory is also guided by our neuroscientific studies with the outstanding participation of Theravada Buddhist monks, with other relevant findings in literature. BTM suggests mechanisms for the different forms of meditation, with the down-regulation of brain network activities in FAM, the gating and tuning of network coupling in OMM, and state-related up-regulation effects in CM and LKM. The theory also advances a leftward asymmetry in top-down regulation, and an enhanced inter-hemispheric integration, in meditation states and traits, also with implications for a theoretical understanding of conscious access. Meditation thus provides a meta-function for an efficient brain/mind regulation, and a flexible allocation of highly limited and often constrained (e.g., by negative emotion and mind wandering) brain activity resources, which can be related to mindfulness. Finally, a series of experimental predictions is derived from the theory
Walking-related locomotion is facilitated by the perception of distant targets in the extrapersonal space
No full textThe Gibsonian notion of affordance has been massively employed in cognitive sciences to characterize the tight interdependence between hand-related actions, manipulable objects and peripersonal space. A behavioural facilitation effect, indeed, is observed for grasping actions directed to objects located in the ‘reachable’ peripersonal space. Relevantly, this relationship is supported by dedicated neural systems in the brain. The original notion of affordance, however, was directly inspired by real-time interactions between animals and their extended natural environment. Consistently, also the extrapersonal space representation can be significantly modulated by action-related factors, and the brain contains dedicated systems for the representation of topographical space and navigation. Here we examined whether a facilitation effect could be also described for a walking-related action in the far extrapersonal space. To this aim, we employed a go/no-go paradigm requiring subjects to execute a footstep ahead in response to pictures of a virtual reality environment containing objects located at different distances (near, far) and eccentricities (central, peripheral). A walking-related, facilitation effect for distant extrapersonal locations was found, suggesting an automatic trigger of walking by positions that preferentially guide spatial exploration. Based on the parallelism with the literature on micro-affordances, we propose that this effect can be described in terms of “macro-affordances”
Modulation of heartbeat-evoked oscillations and connectivity by respiration and focus of attention
No full textHeartbeat evoked potentials (HEPs) are EEG voltage fluctuations that reflect the cortical processing of cardiac signals. In the time-frequency domain, recent studies have observed significant heartbeat evoked oscillations (HEOs) and connectivity at rest and during a task involving bodily self-consciousness.1,2 In the time domain, we recently found higher HEP positivity during exhalation compared to inhalation in a task focused on attending to cardiac sensations, likely reflecting heightened cardiac interoceptive attention.3 Here, we aimed to investigate whether HEOs and functional connectivity can be modulated by cardiac interoceptive attention and the respiratory phase. We assessed HEOs (heartbeat-related power and inter-trial coherence) and network connectivity across the respiratory cycle in 28 healthy volunteers at rest, during a cardiac interoceptive task (Heartbeat Counting Task), and during its exteroceptive control condition (Cardiac-Tone Counting Task). We found a significant increase in power, inter-trial coherence, and synchronization between cortical regions evoked by the heartbeat in theta and alpha bands during exhalation compared to inhalation, specifically during the cardiac interoceptive task. These data corroborate previous results highlighting the capability of respiration to modulate cardiac interoception, offering significant insights for clinical interventions to improve self-regulation. These results also suggest that changes in HEOs and functional connectivity in the alpha band may be related to the selective inhibition or disengagement from competing or distracting exteroceptive stimuli that are outside the focus of attention, particularly during exhalation
Slow Resting State Fluctuations Enhance Neuronal and Behavioral Responses to Looming Sounds
No full textWe investigate both experimentally and using a computational model how the power of the electroencephalogram (EEG) recorded in human subjects tracks the presentation of sounds with acoustic intensities that increase exponentially (looming) or remain constant (flat). We focus on the link between this EEG tracking response, behavioral reaction times and the time scale of fluctuations in the resting state, which show considerable inter-subject variability. Looming sounds are shown to generally elicit a sustained power increase in the alpha and beta frequency bands. In contrast, flat sounds only elicit a transient upsurge at frequencies ranging from 7 to 45 Hz. Likewise, reaction times (RTs) in an audio-tactile task at different latencies from sound onset also present significant differences between sound types. RTs decrease with increasing looming intensities, i.e. as the sense of urgency increases, but remain constant with stationary flat intensities. We define the reaction time variation or “gain” during looming sound presentation, and show that higher RT gains are associated with stronger correlations between EEG power responses and sound intensity. Higher RT gain further entails higher relative power differences between loom and flat in the alpha and beta bands. The full-width-at-half-maximum of the autocorrelation function of the eyes-closed resting state EEG also increases with RT gain. The effects are topographically located over the central and frontal electrodes. A computational model reveals that the increase in stimulus–response correlation in subjects with slower resting state fluctuations is expected when EEG power fluctuations at each electrode and in a given band are viewed as simple coupled low-pass filtered noise processes jointly driven by the sound intensity. The model assumes that the strength of stimulus-power coupling is proportional to RT gain in different coupling scenarios, suggesting a mechanism by which slower resting state fluctuations enhance EEG response and shorten reaction times
Respiratory rhythm and multisensory perception
No full textIntroduction: The brain continuously processes information coming from both the external environment and visceral signals generated by the body. This constant information exchange between the body and the brain allows rhythmic signals originating from the heart and lungs, among others, to influence perception. In previous work, we have shown that cardiac cycle phase interacts with multisensory integration, i.e., the non-linear combination of information coming from multiple senses. Here, we investigated respiratory modulations of reaction times and multisensory integration in a simple detection task. Methods: Forty healthy participants were presented with unimodal (Auditory, Visual, Tactile) and bimodal (Audio-Tactile, Audio-Visual, Visuo-Tactile) stimuli while respiratory activity was recorded. Linear mixed effects models were performed on reaction times and the Race Model Inequality approach was employed to quantify multisensory integration, with a specific focus on respiratory phases. Results: First, respiration was found to significantly modulate reaction times irrespective of the stimulus type, with distinct temporal dynamics for unimodal and bimodal stimuli. Notably, reaction times were slower during the expiration-to-inspiration phase. Then, the Race Model Inequality analysis revealed higher multisensory integration for Audio-Tactile and Audio-Visual stimuli during expiration-toinspiration phase. Participants also adapted their respiratory cycle, as their response onsets preferentially occurred during early expiration. Discussion: These findings indicate that respiration is not merely a bottom-up mechanism but is actively adjusted to optimize the signalto-noise balance between interoceptive and exteroceptive signals. From a predictive processing perspective, these results suggest that respiration acts as a "master clock" aligning external information sampling with fluctuating states of neural excitability. This intricate interplay between respiration and neural processes sheds light on the dynamic nature of multisensory integration and its modulation by peripheral factors
Walking-related locomotion is facilitated by the perception of distant targets in the extrapersonal space
Full text linkThe Gibsonian notion of affordance has been massively employed in cognitive sciences to characterize the tight interdependence between hand-related actions, manipulable objects and peripersonal space. A behavioural facilitation effect, indeed, is observed for grasping actions directed to objects located in the ‘reachable’ peripersonal space. Relevantly, this relationship is supported by dedicated neural systems in the brain. The original notion of affordance, however, was directly inspired by real-time interactions between animals and their extended natural environment. Consistently, also the extrapersonal space representation can be significantly modulated by action-related factors, and the brain contains dedicated systems for the representation of topographical space and navigation. Here we examined whether a facilitation effect could be also described for a walking-related action in the far extrapersonal space. To this aim, we employed a go/no-go paradigm requiring subjects to execute a footstep ahead in response to pictures of a virtual reality environment containing objects located at different distances (near, far) and eccentricities (central, peripheral). A walking-related, facilitation effect for distant extrapersonal locations was found, suggesting an automatic trigger of walking by positions that preferentially guide spatial exploration. Based on the parallelism with the literature on micro-affordances, we propose that this effect can be described in terms of “macro-affordances”
When the heart inhibits the brain: Cardiac phases modulate short-interval intracortical inhibition
Full text linkThe phasic cardiovascular activity influences the central nervous system through the systolic baroreceptor inputs, inducing widespread inhibitory effects on behavior. Through transcranial magnetic stimulation (TMS) delivered during resting-state over the left primary motor cortex and across the different cardiac phases, we measured corticospinal excitability (CSE) and distinct indices of intracortical motor inhibition: short (SICI) and long (LICI) interval, corresponding to GABAA and GABAB neurotransmission, respectively. We found a significant effect of the cardiac phase on short-intracortical inhibition, without any influence on LICI. Specifically, SICI was stronger at systole compared to diastole. These results show a tight relationship between the cardiac cycle and the inhibitory neurotransmission within M1, and in particular with GABAA-ergic-mediated motor inhibition. We hypothesize that this process requires greater motor control via the gating mechanism and that this, in turn, needs to be recalibrated through the modulation of intracortical inhibition
Heart is deceitful above all things: Threat expectancy induces the illusory perception of increased heartrate
Full text linkIt has been suggested that our perception of the internal milieu, or the body's internal state, is shaped by our beliefs and previous knowledge about the body's expected state, rather than being solely based on actual interoceptive experiences. This study investigated whether heartbeat perception could be illusorily distorted towards prior subjective beliefs, such that threat expectations suffice to induce a misperception of heartbeat frequency. Participants were instructed to focus on their cardiac activity and report their heartbeat, either tapping along to it (Experiment 1) or silently counting (Experiment 2) while ECG was recorded. While completing this task, different cues provided valid predictive information about the intensity of an upcoming cutaneous stimulation (high- vs. low- pain). Results showed that participants expected a heart rate increase over the anticipation of high- vs. low-pain stimuli and that this belief was perceptually instantiated, as suggested by their interoceptive reports. Importantly, the perceived increase was not mirrored by the real heart rate. Perceptual modulations were absent when participants executed the same task but with an exteroceptive stimulus (Experiment 3). The findings reveal, for the first time, an interoceptive illusion of increased heartbeats elicited by threat expectancy and shed new light on interoceptive processes through the lenses of Bayesian predictive processes, providing tantalizing insights into how such illusory phenomena may intersect with the recognition and regulation of people's internal states
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