Katja Valli - Academia.edu (original) (raw)
Papers by Katja Valli
Despite a surge of studies on the effects of COVID-19 on our well-being, we know little about how... more Despite a surge of studies on the effects of COVID-19 on our well-being, we know little about how the pandemic is reflected in people’s spontaneous thoughts and experiences, such as mind-wandering (or daydreaming) during wakefulness and dreaming during sleep. We investigated whether and how COVID-19 related general concern, anxiety, and daily worry are associated with the daily fluctuation of the affective quality of mind-wandering and dreaming, and to what extent these associations can be explained by poor sleep quality. We used ecological momentary assessment by asking participants to rate the affect they experienced during mind-wandering and dreaming in daily logs over a two-week period. Our preregistered analyses based on 1758 dream logs from 172 individuals and 1517 mind-wandering logs from 153 individuals showed that, on days when people experienced more worry, they reported higher levels of negative affect, and lower levels of positive affect, during mind-wandering. Only dail...
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The Threat Simulation Theory (TST) postulates that dreaming evolved as a mental simulation for th... more The Threat Simulation Theory (TST) postulates that dreaming evolved as a mental simulation for the rehearsal of the neurocognitive mechanisms essential for threat recognition and avoidance behaviors. In the present study, we tested the predictions of the TST that dreams are specialized in the frequent simulation of realistic and severe threatening events targeted against the dream self, and that the dream self is likely to take appropriate defensive actions against the threat. The subjects were 50 Swedish university students who kept home-based dream diaries for a period of two or four weeks. The dreams were analyzed with a content analysis method specifically designed for identifying and classifying threatening events in dreams, the Dream Threat Scale. Our results show that in the dreams of ordinary young adults threatening events are frequent, severe, realistic and targeted against the self and significant others. Appropriate defensive actions are frequently undertaken when the si...
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British journal of anaesthesia, 2020
BACKGROUND Coherent alpha electroencephalogram (EEG) rhythms in the frontal cortex have been corr... more BACKGROUND Coherent alpha electroencephalogram (EEG) rhythms in the frontal cortex have been correlated with the hypnotic effects of propofol and dexmedetomidine, but less is known about frontal connectivity as a state-specific correlate of unresponsiveness as compared with long-range connectivity. We aimed to distinguish dose- and state-dependent effects of dexmedetomidine and propofol on EEG connectivity. METHODS Forty-seven healthy males received either dexmedetomidine (n=23) or propofol (n=24) as target-controlled infusion with stepwise increments until loss of responsiveness (LOR). We attempted to arouse participants during constant dosing (return of responsiveness [ROR]), and the target concentration was then increased 50% to achieve presumed loss of consciousness. We collected 64-channel EEG data and prefrontal-frontal and anterior-posterior functional connectivity in the alpha band (8-14 Hz) was measured using coherence and weighted phase lag index (wPLI). Directed connectiv...
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Consciousness and Cognition, 2021
To understand how anesthetics with different molecular mechanisms affect consciousness, we explor... more To understand how anesthetics with different molecular mechanisms affect consciousness, we explored subjective experiences recalled after responsive and unresponsive sedation induced with equisedative doses of dexmedetomidine, propofol, sevoflurane, and S-ketamine in healthy male participants (N = 140). The anesthetics were administered in experimental setting using target-controlled infusion or vapouriser for one hour. Interviews conducted after anesthetic administration revealed that 46.9% (n = 46) of arousable participants (n = 98) reported experiences, most frequently dreaming or memory incorporation of the setting. Participants receiving dexmedetomidine reported experiences most often while S-ketamine induced the most multimodal experiences. Responsiveness at the end of anesthetic administration did not affect the prevalence or content of reported experiences. These results demonstrate that subjective experiences during responsive and unresponsive sedation are common and anesthetic agents with different molecular mechanisms of action may have different effects on the prevalence and complexity of the experiences, albeit in the present sample the differences between drugs were minute.
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British Journal of Psychology, 2021
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Neuroscience of Consciousness, 2020
The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of... more The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a step-wise and simplified form, capturing its core idea. The Dream Catcher experiment involved a Data Team, which measured participants’ brain activity during sleep and collected dream reports, and a blinded Analysis Team, which was challenged to predict, based solely on brain measurements, whether or not a participant had a dream experience. Using a serial-awakening paradigm, the Data Team prepared 54 1-min polysomnograms of non-rapid eye movement sleep—27 of dreamful sleep and 27 of dreamless sleep (three of each condition from each of the nine participants)—redacting from th...
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Nightmares are vivid, extended and extremely dysphoric dreams that awaken the dreamer. Twin studi... more Nightmares are vivid, extended and extremely dysphoric dreams that awaken the dreamer. Twin studies indicate that nightmare frequency has a heritability between 36 and 51% providing evidence for genetic factors underlying predisposition to nightmares. Furthermore, while cross-sectional epidemiological findings suggest that heavy alcohol usage, traumatic experiences and psychiatric diseases associate with nightmares, the causal relationships between these conditions and nightmares have remained unknown. To examine the biological mechanisms behind nightmares, we performed a genome-wide association study in 28,596 individuals from Finland and the United States. We identified individual genetic variants that predispose to nightmares near MYOF (rs701873, p=2.18e-8) and PTPRJ (rs11039471,p=3.7e-8), a gene previously associated with sleep duration. We found a strong genetic correlation between the frequency of nightmares and traits related to personality and psychiatric disorders; neurotic...
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Imagination, Cognition and Personality, 2018
The Dark Triad (i.e., Machiavellianism, narcissism, and psychopathy) of personality has been asso... more The Dark Triad (i.e., Machiavellianism, narcissism, and psychopathy) of personality has been associated with behaviors that facilitate a fast life history strategy, such as aggressiveness and increased interest in sex. In this online study (N = 265), we investigated the possibility that these personality traits have an association with dream content, namely, increased frequency of sexual and aggressive dreams. In regression analyses, we found that the frequency of aggressive dreams was predicted by Machiavellianism and psychopathy. The frequency of sexual dreams was predicted by psychopathy and narcissism. The results support a number of previous studies, suggesting that especially psychopathy is a manifestation of a fast life history strategy. Further, individuals high in this trait may simulate evolutionarily relevant actions in their dreams.
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Frontiers in Psychology, 2019
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International Journal of Psychophysiology, 2019
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Neuropsychologia, 2019
The neural and perceptual mechanisms that support the efficient visual detection of snakes in hum... more The neural and perceptual mechanisms that support the efficient visual detection of snakes in humans are still not fully understood. According to the Snake Detection Theory, selection pressures posed by snakes on early primates have shaped the development of the visual system. Previous studies in humans have investigated early visual electrophysiological activity in response to snake images vs. various alternative dangerous or non-dangerous stimuli. These studies have shown that the Early Posterior Negativity (EPN) component is selectively elicited by snake or snake-like images. Recent findings yielded the complementary/alternative hypothesis that early humans (and possibly other primates) evolved an aversion especially for potentially harmful triangular shapes, such as teeth, claws or spikes. In the present study we investigated the effect of triangular and diamond-shaped patterns in snake skins on the ERP correlates of visual processing in humans. In the first experiment, we employed pictures of snakes displaying either triangular/diamond-shaped patterns or no particular pattern on their skins, and pictures of frogs as control. Participants observed a random visual presentation of these pictures. Consistent with previous studies, snakes elicited an enhanced negativity between 225 and 300 ms (EPN) compared to frogs. However, snakes featuring triangular/diamond-shaped patterns on their skin produced an enhanced EPN compared to the snakes that did not display such patterns. In a second experiment we used pictures displaying only skin patterns of snakes and frogs. Results from the second experiment confirmed the results of the first experiment, suggesting that triangular snake-skin patterns modulate the activity in human visual cortex. Taken together, our results constitute an important contribution to the snake detection theory.
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The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of... more The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a graded and simplified form, capturing its core idea. The experiment involved a Data Team, who measured…
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British Journal of Anaesthesia, 2018
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The Journal of Neuroscience, 2019
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Recently, cortical correlates of specific dream contents have been reported, such as the activati... more Recently, cortical correlates of specific dream contents have been reported, such as the activation of the sensorimotor cortex during dreamed hand clenching. Yet, the causal mechanisms underlying specific dream content remain largely elusive. Here, we investigated how alterations in the excitability of sensorimotor areas through transcranial direct current stimulation (tDCS) might alter dream content. Following bihemispheric tDCS or sham stimulation, participants who were awakened from REM sleep filled out a questionnaire on bodily sensations in dreams. tDCS, compared to sham stimulation, significantly decreased reports of dream movement, especially repetitive actions. Contrary to this, other types of bodily experiences, such as tactile or vestibular sensations, were not affected by tDCS, confirming the specificity of stimulation effects. In addition, tDCS reduced interhemispheric coherence in parietal areas and altered the phasic electromyography correlation between the two arms. T...
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Journal of Clinical Sleep Medicine, 2019
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Consciousness and Cognition, 2019
Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social ... more Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social events. The Sociality Bias and the Strengthening hypotheses of SST were tested. Social Content Scale (SCS) was developed to quantify social events. Additionally, we attempted to replicate a previous finding (McNamara et al., 2005, Psychological Science) of REM dreams as predisposed to aggressive, and NREM dreams to prosocial interactions. Further, we investigated the frequency and quality of interactions in late vs early REM and NREM dreams. Data consisted of wake, REM and NREM home dream reports (N = 232, 116, 116, respectively) from 15 students. Dreams overrepresented social events compared to wake reports, supporting the Sociality Bias hypothesis. However, the Strengthening Hypothesis was not supported. We weren't able to replicate the McNamara et al. finding, and no time of night effect was found. While SST gained partial support, further research on social contents in dreams is required.
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Emotion (Washington, D.C.), Jan 26, 2018
The snake detection hypothesis claims that predatory pressure from snakes has shaped the primate ... more The snake detection hypothesis claims that predatory pressure from snakes has shaped the primate visual system, but we still know very little about how the brain processes evolutionarily important visual cues, and which factors are crucial for quick detection of snakes. We investigated how visual features modulate the electrophysiological markers of early attentional processes. In Experiment 1, we compared snake, rope, gun, and bird images to isolate the effects due to curvilinearity of the stimuli. The results showed that both snake and rope images elicited enhanced P1 and N1 event-related potential components as well as early posterior negativity (EPN). In Experiment 2, we studied whether nonthreatening curvilinear images (i.e., ropes) still elicit the enhanced electrophysiological responses when snake images are not presented as stimuli, and therefore the context does not provoke top-down attention to curvilinear shapes. Rope images still evoked an enhanced EPN, suggesting that c...
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Despite a surge of studies on the effects of COVID-19 on our well-being, we know little about how... more Despite a surge of studies on the effects of COVID-19 on our well-being, we know little about how the pandemic is reflected in people’s spontaneous thoughts and experiences, such as mind-wandering (or daydreaming) during wakefulness and dreaming during sleep. We investigated whether and how COVID-19 related general concern, anxiety, and daily worry are associated with the daily fluctuation of the affective quality of mind-wandering and dreaming, and to what extent these associations can be explained by poor sleep quality. We used ecological momentary assessment by asking participants to rate the affect they experienced during mind-wandering and dreaming in daily logs over a two-week period. Our preregistered analyses based on 1758 dream logs from 172 individuals and 1517 mind-wandering logs from 153 individuals showed that, on days when people experienced more worry, they reported higher levels of negative affect, and lower levels of positive affect, during mind-wandering. Only dail...
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The Threat Simulation Theory (TST) postulates that dreaming evolved as a mental simulation for th... more The Threat Simulation Theory (TST) postulates that dreaming evolved as a mental simulation for the rehearsal of the neurocognitive mechanisms essential for threat recognition and avoidance behaviors. In the present study, we tested the predictions of the TST that dreams are specialized in the frequent simulation of realistic and severe threatening events targeted against the dream self, and that the dream self is likely to take appropriate defensive actions against the threat. The subjects were 50 Swedish university students who kept home-based dream diaries for a period of two or four weeks. The dreams were analyzed with a content analysis method specifically designed for identifying and classifying threatening events in dreams, the Dream Threat Scale. Our results show that in the dreams of ordinary young adults threatening events are frequent, severe, realistic and targeted against the self and significant others. Appropriate defensive actions are frequently undertaken when the si...
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British journal of anaesthesia, 2020
BACKGROUND Coherent alpha electroencephalogram (EEG) rhythms in the frontal cortex have been corr... more BACKGROUND Coherent alpha electroencephalogram (EEG) rhythms in the frontal cortex have been correlated with the hypnotic effects of propofol and dexmedetomidine, but less is known about frontal connectivity as a state-specific correlate of unresponsiveness as compared with long-range connectivity. We aimed to distinguish dose- and state-dependent effects of dexmedetomidine and propofol on EEG connectivity. METHODS Forty-seven healthy males received either dexmedetomidine (n=23) or propofol (n=24) as target-controlled infusion with stepwise increments until loss of responsiveness (LOR). We attempted to arouse participants during constant dosing (return of responsiveness [ROR]), and the target concentration was then increased 50% to achieve presumed loss of consciousness. We collected 64-channel EEG data and prefrontal-frontal and anterior-posterior functional connectivity in the alpha band (8-14 Hz) was measured using coherence and weighted phase lag index (wPLI). Directed connectiv...
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Consciousness and Cognition, 2021
To understand how anesthetics with different molecular mechanisms affect consciousness, we explor... more To understand how anesthetics with different molecular mechanisms affect consciousness, we explored subjective experiences recalled after responsive and unresponsive sedation induced with equisedative doses of dexmedetomidine, propofol, sevoflurane, and S-ketamine in healthy male participants (N = 140). The anesthetics were administered in experimental setting using target-controlled infusion or vapouriser for one hour. Interviews conducted after anesthetic administration revealed that 46.9% (n = 46) of arousable participants (n = 98) reported experiences, most frequently dreaming or memory incorporation of the setting. Participants receiving dexmedetomidine reported experiences most often while S-ketamine induced the most multimodal experiences. Responsiveness at the end of anesthetic administration did not affect the prevalence or content of reported experiences. These results demonstrate that subjective experiences during responsive and unresponsive sedation are common and anesthetic agents with different molecular mechanisms of action may have different effects on the prevalence and complexity of the experiences, albeit in the present sample the differences between drugs were minute.
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British Journal of Psychology, 2021
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Neuroscience of Consciousness, 2020
The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of... more The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a step-wise and simplified form, capturing its core idea. The Dream Catcher experiment involved a Data Team, which measured participants’ brain activity during sleep and collected dream reports, and a blinded Analysis Team, which was challenged to predict, based solely on brain measurements, whether or not a participant had a dream experience. Using a serial-awakening paradigm, the Data Team prepared 54 1-min polysomnograms of non-rapid eye movement sleep—27 of dreamful sleep and 27 of dreamless sleep (three of each condition from each of the nine participants)—redacting from th...
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Nightmares are vivid, extended and extremely dysphoric dreams that awaken the dreamer. Twin studi... more Nightmares are vivid, extended and extremely dysphoric dreams that awaken the dreamer. Twin studies indicate that nightmare frequency has a heritability between 36 and 51% providing evidence for genetic factors underlying predisposition to nightmares. Furthermore, while cross-sectional epidemiological findings suggest that heavy alcohol usage, traumatic experiences and psychiatric diseases associate with nightmares, the causal relationships between these conditions and nightmares have remained unknown. To examine the biological mechanisms behind nightmares, we performed a genome-wide association study in 28,596 individuals from Finland and the United States. We identified individual genetic variants that predispose to nightmares near MYOF (rs701873, p=2.18e-8) and PTPRJ (rs11039471,p=3.7e-8), a gene previously associated with sleep duration. We found a strong genetic correlation between the frequency of nightmares and traits related to personality and psychiatric disorders; neurotic...
Bookmarks Related papers MentionsView impact
Imagination, Cognition and Personality, 2018
The Dark Triad (i.e., Machiavellianism, narcissism, and psychopathy) of personality has been asso... more The Dark Triad (i.e., Machiavellianism, narcissism, and psychopathy) of personality has been associated with behaviors that facilitate a fast life history strategy, such as aggressiveness and increased interest in sex. In this online study (N = 265), we investigated the possibility that these personality traits have an association with dream content, namely, increased frequency of sexual and aggressive dreams. In regression analyses, we found that the frequency of aggressive dreams was predicted by Machiavellianism and psychopathy. The frequency of sexual dreams was predicted by psychopathy and narcissism. The results support a number of previous studies, suggesting that especially psychopathy is a manifestation of a fast life history strategy. Further, individuals high in this trait may simulate evolutionarily relevant actions in their dreams.
Bookmarks Related papers MentionsView impact
Frontiers in Psychology, 2019
Bookmarks Related papers MentionsView impact
International Journal of Psychophysiology, 2019
Bookmarks Related papers MentionsView impact
Neuropsychologia, 2019
The neural and perceptual mechanisms that support the efficient visual detection of snakes in hum... more The neural and perceptual mechanisms that support the efficient visual detection of snakes in humans are still not fully understood. According to the Snake Detection Theory, selection pressures posed by snakes on early primates have shaped the development of the visual system. Previous studies in humans have investigated early visual electrophysiological activity in response to snake images vs. various alternative dangerous or non-dangerous stimuli. These studies have shown that the Early Posterior Negativity (EPN) component is selectively elicited by snake or snake-like images. Recent findings yielded the complementary/alternative hypothesis that early humans (and possibly other primates) evolved an aversion especially for potentially harmful triangular shapes, such as teeth, claws or spikes. In the present study we investigated the effect of triangular and diamond-shaped patterns in snake skins on the ERP correlates of visual processing in humans. In the first experiment, we employed pictures of snakes displaying either triangular/diamond-shaped patterns or no particular pattern on their skins, and pictures of frogs as control. Participants observed a random visual presentation of these pictures. Consistent with previous studies, snakes elicited an enhanced negativity between 225 and 300 ms (EPN) compared to frogs. However, snakes featuring triangular/diamond-shaped patterns on their skin produced an enhanced EPN compared to the snakes that did not display such patterns. In a second experiment we used pictures displaying only skin patterns of snakes and frogs. Results from the second experiment confirmed the results of the first experiment, suggesting that triangular snake-skin patterns modulate the activity in human visual cortex. Taken together, our results constitute an important contribution to the snake detection theory.
Bookmarks Related papers MentionsView impact
The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of... more The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a graded and simplified form, capturing its core idea. The experiment involved a Data Team, who measured…
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British Journal of Anaesthesia, 2018
Bookmarks Related papers MentionsView impact
The Journal of Neuroscience, 2019
Bookmarks Related papers MentionsView impact
Recently, cortical correlates of specific dream contents have been reported, such as the activati... more Recently, cortical correlates of specific dream contents have been reported, such as the activation of the sensorimotor cortex during dreamed hand clenching. Yet, the causal mechanisms underlying specific dream content remain largely elusive. Here, we investigated how alterations in the excitability of sensorimotor areas through transcranial direct current stimulation (tDCS) might alter dream content. Following bihemispheric tDCS or sham stimulation, participants who were awakened from REM sleep filled out a questionnaire on bodily sensations in dreams. tDCS, compared to sham stimulation, significantly decreased reports of dream movement, especially repetitive actions. Contrary to this, other types of bodily experiences, such as tactile or vestibular sensations, were not affected by tDCS, confirming the specificity of stimulation effects. In addition, tDCS reduced interhemispheric coherence in parietal areas and altered the phasic electromyography correlation between the two arms. T...
Bookmarks Related papers MentionsView impact
Journal of Clinical Sleep Medicine, 2019
Bookmarks Related papers MentionsView impact
Consciousness and Cognition, 2019
Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social ... more Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social events. The Sociality Bias and the Strengthening hypotheses of SST were tested. Social Content Scale (SCS) was developed to quantify social events. Additionally, we attempted to replicate a previous finding (McNamara et al., 2005, Psychological Science) of REM dreams as predisposed to aggressive, and NREM dreams to prosocial interactions. Further, we investigated the frequency and quality of interactions in late vs early REM and NREM dreams. Data consisted of wake, REM and NREM home dream reports (N = 232, 116, 116, respectively) from 15 students. Dreams overrepresented social events compared to wake reports, supporting the Sociality Bias hypothesis. However, the Strengthening Hypothesis was not supported. We weren't able to replicate the McNamara et al. finding, and no time of night effect was found. While SST gained partial support, further research on social contents in dreams is required.
Bookmarks Related papers MentionsView impact
Emotion (Washington, D.C.), Jan 26, 2018
The snake detection hypothesis claims that predatory pressure from snakes has shaped the primate ... more The snake detection hypothesis claims that predatory pressure from snakes has shaped the primate visual system, but we still know very little about how the brain processes evolutionarily important visual cues, and which factors are crucial for quick detection of snakes. We investigated how visual features modulate the electrophysiological markers of early attentional processes. In Experiment 1, we compared snake, rope, gun, and bird images to isolate the effects due to curvilinearity of the stimuli. The results showed that both snake and rope images elicited enhanced P1 and N1 event-related potential components as well as early posterior negativity (EPN). In Experiment 2, we studied whether nonthreatening curvilinear images (i.e., ropes) still elicit the enhanced electrophysiological responses when snake images are not presented as stimuli, and therefore the context does not provoke top-down attention to curvilinear shapes. Rope images still evoked an enhanced EPN, suggesting that c...
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