Confidence is higher in touch than in vision in cases of perceptual ambiguity

The inclination to touch objects that we can see is a surprising behaviour, given that vision often supplies relevant and sufficiently accurate sensory evidence. Here we suggest that this 'fact-checking' phenomenon could be explained if touch provides a higher level of perceptual certainty than vision. Testing this hypothesis, observers explored inverted T-shaped stimuli eliciting the Vertical-horizontal illusion in vision and touch, which included clear-cut and ambiguous cases. In separate blocks, observers judged whether the vertical bar was shorter or longer than the horizontal bar and rated the confidence in their judgments. Decisions reached by vision were objectively more accurate than those reached by touch with higher overall confidence ratings. However, while confidence was higher for vision rather than for touch in clear-cut cases, observers were more confident in touch when the stimuli were ambiguous. This relative bias as a function of ambiguity qualifies the view that confidence tracks objective accuracy and uses a comparable mapping across sensory modalities. Employing a perceptual illusion, our method disentangles objective and subjective accuracy showing how the latter is tracked by confidence and point towards possible origins for 'fact checking' by touch

Estudo neurofisiológico da discriminação de distância em humanos

Tactile width discrimination processing has been extensively studied in rodents and has demonstrated multiple relevant basic mechanisms. Despite this relevance, the number of studies of width discrimination in humans has been scarce. During the present dissertation, neurophysiological correlates of width discrimination were analyzed through electroencephalography recordings in participants performing a width discrimination task in active or passive modes. Analysis of power in the delta, theta, alpha, beta, and gamma frequency bands revealed differences in the power for different frequency bands and electrodes recorded. Active width discrimination processing was characterized by an increase in the power of delta, theta and gamma frequency bands in electrodes F3 and F4, and an increase in power in the gamma frequency band in T4. Passive tactile width processing was characterized by an increase in the power of delta in electrodes Fp1 and T4, and an increase in gamma frequency band in Tp10. Altogether these results suggest that active and passive tactile width discrimination processing are characterized by an asymmetrical network involving prefrontal, frontal and temporal electrodes, in delta, theta, and gamma frequency bands.O estudo do processamento tátil de distâncias encontra-se bastante desenvolvido em roedores, tendo sido útil para a demonstração de múltiplos mecanismos básicos relevantes. Apesar desta relevância, o estudo da discriminação de distâncias em humanos é ainda bastante reduzido. Durante a presente dissertação foram analisados os correlatos neurofisiológicos, através do registo de eletroencefalografia, em participantes que realizavam uma tarefa de discriminação de distância em modo ativo ou passivo. A análise da potência das bandas de frequências delta, teta, alfa, beta e gama revelou diferenças na potência do sinal para diferentes bandas de frequências e elétrodos. O processamento ativo era caracterizado por um aumento da potência nas bandas de frequências delta, teta e gama nos elétrodos F3, F4; e um aumento da atividade na banda de frequência gama no elétrodo T4. O processamento passivo era caracterizado por um aumento da potência de delta nos elétrodos Fp1 e T4 e um aumento da potência de gama em Tp10. No seu conjunto, estes resultados sugerem que o processamento ativo e passivo da distância são caraterizados por uma rede assimétrica envolvendo elétrodos pré-frontais, frontais e temporais nas bandas de frequência delta, teta e gama.Mestrado em Biomedicina Molecula

Neurophysiological correlates of tactile width discrimination in humans

Introduction: Tactile information processing requires the integration of sensory, motor, and cognitive information. Width discrimination has been extensively studied in rodents, but not in humans. Methods: Here, we describe Electroencephalography (EEG) signals in humans performing a tactile width discrimination task. The first goal of this study was to describe changes in neural activity occurring during the discrimination and the response periods. The second goal was to relate specific changes in neural activity to the performance in the task. Results: Comparison of changes in power between two different periods of the task, corresponding to the discrimination of the tactile stimulus and the motor response, revealed the engagement of an asymmetrical network associated with fronto-temporo-parieto-occipital electrodes and across multiple frequency bands. Analysis of ratios of higher [Ratio 1: (0.5–20 Hz)/(0.5–45 Hz)] or lower frequencies [Ratio 2: (0.5–4.5 Hz)/(0.5–9 Hz)], during the discrimination period revealed that activity recorded from frontal-parietal electrodes was correlated to tactile width discrimination performance between-subjects, independently of task difficulty. Meanwhile, the dynamics in parieto-occipital electrodes were correlated to the changes in performance within-subjects (i.e., between the first and the second blocks) independently of task difficulty. In addition, analysis of information transfer, using Granger causality, further demonstrated that improvements in performance between blocks were characterized by an overall reduction in information transfer to the ipsilateral parietal electrode (P4) and an increase in information transfer to the contralateral parietal electrode (P3). Discussion: The main finding of this study is that fronto-parietal electrodes encoded between-subjects’ performances while parieto-occipital electrodes encoded within-subjects’ performances, supporting the notion that tactile width discrimination processing is associated with a complex asymmetrical network involving fronto-parieto-occipital electrodes.info:eu-repo/semantics/publishedVersio

The impact of internal-generated contextual clues on EFL vocabulary learning: insights from EEG

With the popularity of learning vocabulary online among English as a Foreign Language (EFL) learners today, educators and researchers have been considering ways to enhance the effectiveness of this approach. Prior research has underscored the significance of contextual clues in vocabulary acquisition. However, few studies have compared the context provided by instructional materials and that generated by learners themselves. Hence, this present study sought to explore the impact of internal-generated contextual clues in comparison to those provided by instructional materials on EFL learners’ online vocabulary acquisition. A total of 26 university students were enrolled and underwent electroencephalography (EEG). Based on a within-subjects design, all participants learned two groups of vocabulary words through a series of video clips under two conditions: one where the contexts were externally provided and the other where participants themselves generated the contexts. In this regard, participants were tasked with either viewing contextual clues presented on the screen or creating their own contextual clues for word comprehension. EEG signals were recorded during the learning process to explore neural activities, and post-tests were conducted to assess learning performance after each vocabulary learning session. Our behavioral results indicated that comprehending words with internal-generated contextual clues resulted in superior learning performance compared to using context provided by instructional materials. Furthermore, EEG data revealed that learners expended greater cognitive resources and mental effort in semantically integrating the meaning of words when they self-created contextual clues, as evidenced by stronger alpha and beta-band oscillations. Moreover, the stronger alpha-band oscillations and lower inter-subject correlation (ISC) among learners suggested that the generative task of creating context enhanced their top-down attentional control mechanisms and selective visual processing when learning vocabulary from videos. These findings underscored the positive effects of internal-generated contextual clues, indicating that instructors should encourage learners to construct their own contexts in online EFL vocabulary instruction rather than providing pre-defined contexts. Future research should aim to explore the limits and conditions of employing these two types of contextual clues in online EFL vocabulary learning. This could be achieved by manipulating the quality and understandability of contexts and considering learners’ language proficiency levels

Neural divergence and convergence for attention to and detection of interoceptive and somatosensory stimuli

Body awareness is constructed by signals originating from within and outside the body. How do these apparently divergent signals converge? We developed a signal detection task to study the neural convergence and divergence of interoceptive and somatosensory signals. Participants focused on either cardiac or tactile events and reported their presence or absence. Beyond some evidence of divergence, we observed a robust overlap in the pattern of activation evoked across both conditions in frontal areas including the insular cortex, as well as parietal and occipital areas, and for both attention and detection of these signals. Psycho-physiological interaction analysis revealed that right insular cortex connectivity was modulated by the conscious detection of cardiac compared to somatosensory sensations, with greater connectivity to occipito-parietal regions when attending to cardiac signals. Our findings speak in favour of the inherent convergence of bodily-related signals and move beyond the apparent antagonism between exteroception and interoception

How does stress induce headache? An experimental study

Psychological stress triggers headaches, but how this happens is unclear. To explore this, 38 episodic migraine sufferers, 28 with tension-type headache (T-TH) and 20 controls rated nausea, negative affect, task-expectancies and headache at 5-minute intervals during an unpredictable and uncontrollable 25-minute mental arithmetic task with a non-contingent failure rate. Blood pressure and pulse rate were measured every 3 minutes and salivary cortisol was sampled before and after the task. Trigeminal activation was measured by nociceptive blink reflex measures during each of the three experimental phases. Multiple regression analyses indicated that negative affect (NA) was the strongest predictor of headache intensity during the task. Increases in stress-headache were unrelated to consistent changes in cardiovascular activity but were related to declines in cortisol and increased post-task trigeminal activity. In repeated measures ANOVAs, participants who developed headache had higher nausea, NA and self-efficacy expectancies than those with no-or-low headache (p <.05 to p <.001). In further multiple regression analyses to identify which aspects of the stress process contributed to the high NA preceding headache, discouragement, anxiety, irritation and tension mediated the relationship between headache intensity during the stressful task and primary and secondary appraisal processes (stressor exposure and stressor reactivity). Avoidant coping, perceived inability to decrease pain, and outcome expectancy independently predicted headache intensity during the stressful task. Anxiety mediated the relationship between headache intensity and the coping tactics of wishful thinking, self-criticism, pain catastrophizing and praying/hoping. Attachment anxiety and the personality traits of openness, agreeableness and conscientiousness moderated the relationship between stress appraisals and headache. Results were discussed using the model of stress-headache as allostatic load. Findings suggest that headache developed when participants overextended themselves during a stressful task, adopting an information processing style which impeded emotional adjustment to changing situational demands. Learning to modify perceptions of threat and adopting a more flexible, less outcome-dependent processing style which avoids response conflict might help to prevent headache from spiralling upward

Divide and conquer: an oscillatory division of labour in service of episodic memory

Both oscillatory synchronisation and oscillatory desynchronisation underpin the formation and retrieval of episodic memories. This paradox begs the question: how can two polar opposite neural phenomena produce the same outcome? Here, we investigate this conundrum by presenting a series of empirical experiments that test the hypothesis that these two phenomena reflect a division of labour in service of episodic memory. We demonstrate that neocortical desynchrony correlates with enhanced information representation, while hippocampal synchrony stiches this information together into a coherent memory trace. Critically, we demonstrate that these processes interact. Neocortical desynchrony precedes and predicts hippocampal synchrony during episodic memory formation, while hippocampal synchrony precedes and predicts neocortical desynchrony during episodic memory retrieval. This thesis suggests that the interaction between neocortical desynchrony and hippocampal synchrony sits at the heart of the formation and retrieval of episodic memories, providing empirical resolution to the so-called synchronisation/desynchronisation conundrum

Metacognition of attention during tactile discrimination

Contains fulltext : 181371.pdf (Publisher’s version ) (Open Access)The ability to monitor the success of cognitive processing is referred to as metacognition. Studies of metacognition typically probe post-decision judgments of confidence, showing that we can report on the success of wide range of cognitive processes. Much less is known about our ability to monitor and report on the degree of top-down attention, an ability of paramount importance in tasks requiring sustained attention. However, it has been repeatedly shown that the degree and locus of top-down attention modulates alpha (8-14Hz) power in sensory cortices. In this study we investigated whether self-reported ratings of attention are reflected by sensory alpha power, independent from confidence and task difficulty. Subjects performed a stair-cased tactile discrimination task requiring sustained somatosensory attention. Each discrimination response was followed by a rating of their attention at the moment of stimulation, or their confidence in the discrimination response. MEG was used to estimate trial-by-trial alpha power preceding stimulation. Staircasing of task-difficulty successfully equalized performance between conditions. Both attention and confidence ratings reflected subsequent discrimination performance. Task difficulty specifically influenced confidence ratings. As expected, specifically attention ratings, but not confidence ratings, correlated negatively with contralateral somatosensory alpha power preceding tactile stimuli. Taken together, these results demonstrate that the degree of attention can be subjectively experienced and reported accurately, independent from task difficulty and knowledge about task performance