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Ergebnisse 4 Einträge
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Recent research suggests that our sense of time intervals in the range of seconds is directly related to activity in the insular cortex, which contains the primary sensory area for interoception. We therefore investigated whether performance in a duration reproduction task might correlate with individual interoceptive awareness and with measurable changes in autonomic activity during the task. Thirty-one healthy volunteers participated in an interoceptive (heartbeat) perception task and in repeated temporal reproduction trials using intervals of 8, 14, and 20s duration while skin conductance levels and cardiac and respiratory periods were recorded. We observed progressive increases in cardiac periods and decreases in skin conductance level during the encoding and (less reliably) the reproduction of these intervals. Notably, individuals' duration reproduction accuracy correlated positively both with the slope of cardiac slowing during the encoding intervals and with individual heartbeat perception scores. These results support the view that autonomic function and interoceptive awareness underpin our perception of time intervals in the range of seconds.
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During affective priming, perception of an emotional “prime stimulus” influences the reaction time to the subsequent emotional “target stimulus”. If prime and target have the same valence (congruent trials), reactions to the target are faster than if prime and target have different valences (incongruent trials). Bem introduced a backward priming paradigm in 2011, where first the target was presented and then the prime after the response. Similar to the classical affective forward priming effects, he found faster reaction times in congruent compared to incongruent trials, and interpreted these results as evidence supporting precognition. In the present exploratory study, while measuring EEG, we combined a forward priming paradigm with a related backward priming paradigm, following Bem’s study. We analysed the EEG data on a group level (ERPs) and on an individual level (single participants, applying artificial neural networks). We found significantly faster reaction times for congruent compared to incongruent trials in the forward priming experiment (p = 0.0004) but no statistically significant differences in the backward priming experiment (p = 0.12). We also found significant differences in ERP amplitude in the forward priming congruent vs incongruent conditions (P8 electrode: p = 0.0002). Backward priming results show weaker, shorter, and less significant differences between congruent and incongruent trials, with maxima at electrodes P7, P3, CP5, and CP1. The neural network results were very variable across participants in both the backward and forward priming and on average, the accuracy results were at chance level for both the forward priming as well as the backward priming. Our results replicate behavioural findings and extend the EEG findings for forward priming. We did not replicate Bem’s backward priming results. These exploratory EEG results are weak, however they give a good starting point for future studies.
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Intuitively, being aware of one's inner processes to move should be crucial for the control of voluntary movements. However, research findings suggest that we are not always aware of the processes leading to movement execution. The present study investigated induced first-person access to inner processes of movement initiation and the underlying brain activities which contribute to the emergence of voluntary movement. Moreover, we investigated differences in task performance between mindfulness meditators and non-meditators while assuming that meditators are more experienced in attending to their inner processes. Two Libet-type tasks were performed; one in which participants were asked to press a button at a moment of their own decision, and the other one in which participants' attention was directed towards their inner processes of decision making regarding the intended movement which lead them to press the button. Meditators revealed a consistent readiness potential (RP) between the two tasks with correlations between the subjective intention time to act and the slope of the early RP. However, non-meditators did not show this consistency. Instead, elicited introspection of inner processes of movement initiation changed early brain activity that is related to voluntary movement processes. Our findings suggest that compared to non-meditators, meditators are more able to access the emergence of negative deflections of slow cortical potentials (SCPs), which could have fundamental effects on initiating a voluntary movement with awareness.
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The readiness potential is an ongoing negativity in the EEG preceding a self-initiated movement by approximately 1.5s. So far it has predominantly been interpreted as a preparatory signal with a causal link to the upcoming movement. Here a different hypothesis is suggested which we call the selective slow cortical potential sampling hypothesis. In this review of recent research results we argue that the initiation of a voluntary action is more likely during negative fluctuations of the slow cortical potential and that the sampling and averaging of many trials leads to the observed negativity. That is, empirical evidence indicates that the early readiness potential is not a neural correlate of preconscious motor preparation and thus a determinant of action. Our hypothesis thereafter challenges the classic interpretation of the Libet experiment which is often taken as proof that there is no free will. We furthermore suggest that slow cortical potentials are related to an urge to act but are not a neural indicator of the decision process of action initiation.
Erkunden
Team
- Wittmann (4)
Eintragsart
Sprache
- Englisch (4)
Thema
- Electroencephalography
- Adult (2)
- Analysis of Variance (1)
- Attention/physiology (1)
- *Awareness (1)
- Awareness/*physiology (1)
- Behavior (1)
- Brain/physiology (1)
- Cerebral Cortex/*physiology (1)
- *Contingent Negative Variation (1)
- Contingent Negative Variation/*physiology (1)
- Electrocardiography (1)
- Emotions/*physiology (1)
- Event-related potentials (1)
- Female (2)
- *Free will (1)
- Galvanic Skin Response (1)
- Heart/*physiology (1)
- Heart Rate/physiology (1)
- Humans (3)
- *Intention (1)
- Intention (1)
- Libet experiment (1)
- *Libet task (1)
- Male (2)
- Meditation (1)
- Middle Aged (1)
- Movement (1)
- Movement/physiology (1)
- Neural networks (1)
- Parapsychology (1)
- Perception/*physiology (1)
- Photic Stimulation/methods (1)
- Priming (psychology) (1)
- Reaction Time (1)
- Reaction time (1)
- Readiness potential (1)
- *Readiness potential (1)
- Respiration (1)
- Semantics (1)
- *Slow cortical potential (1)
- Time Factors (1)
- Time Perception/*physiology (1)
- Volition (1)
- Volition/physiology (1)
- *Voluntary action (1)
- Young Adult (1)