@phdthesis{Murali2023,
  author    = {Murali, Supriya},
  title     = {Understanding the function of spontaneous blinks by investigating internally and externally directed processes},
  doi       = {10.25972/OPUS-28747},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287473},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Humans spontaneously blink several times a minute. These blinks are strongly modulated during various cognitive task. However, the precise function of blinking and the reason for their modulation has not been fully understood. In the present work, I investigated the function of spontaneous blinks through various perceptual and cognitive tasks. Previous research has revealed that blinks rates decrease during some tasks but increase during others. When trying to understand these seemingly contradictory results, I observed that blink reduction occurs when one engages with an external input. For instance, a decrease has been observed due to the onset of a stimulus, sensory input processing and attention towards sensory input. However, for activities that do not involve such an engagement, e.g. imagination, daydreaming or creativity, the blink rate has been shown to increase. To follow up on the proposed hypothesis, I distinguished tasks that involve the processing of an external stimulus and tasks that involve disengagement. In the first part of the project, I explored blinking during stimulus engagement. If the probability of blinking is low when engaging with the stimulus, then one should find a reduction in blinks specifically during the time period of processing but not during sensory input per se. To this end, in study 1, I tested the influence of task-relevant information duration on blink timing and additionally manipulated the overall sensory input using a visual and an auditory temporal simultaneity judgement task. The results showed that blinks were suppressed longer for longer periods of relevant information or in other words, blinks occurred at the end of relevant information processing for both the visual and the auditory modality. Since relevance is mediated through top-down processes, I argue that the reduction in blinks is a top-down driven suppression. In studies 2 and 3, I again investigated stimulus processing, but in this case, processing was triggered internally and not based on specific changes in the external input. To this end, I used bistable stimuli, in which the actual physical stimulus remains constant but their perception switches between different interpretations. Studies on the involvement of attention in such bistable perceptual changes indicate that the sensory input is reprocessed before the perceptual switch. The results revealed a reduction in eye blink rates before the report of perceptual switches. Importantly, I was able to decipher that the decrease was not caused by the perceptual switch or the behavioral response but likely started before the internal switch. Additionally, periods between a blink and a switch were longer than interblink intervals, indicating that blinks were followed by a period of stable percept. To conclude, the first part of the project revealed that there is a top-down driven blink suppression during the processing of an external stimulus. In the second part of the project, I extended the idea of blinks marking the disengagement from external processing and tested if blinking is associated with better performance during internally directed processes. Specifically, I investigated divergent thinking, an aspect of creativity, and the link between performance and blink rates as well as the effect of motor restriction. While I could show that motor restriction was the main factor influencing divergent thinking, the relationship between eye blink rates and creative output also depended on restriction. Results showed that higher blink rates were associated with better performance during free movement, but only between subjects. In other words, subjects who had overall higher blink rates scored better in the task, but when they were allowed to sit or walk freely. Within a single subject, trial with higher blink rates were not associated with better performance. Therefore, possibly, people who are able to disengage easily, as indicated by an overall high blink rate, perform better in divergent thinking tasks. However, the link between blink rate and internal tasks is not clear at this point. Indeed, a more complex measurement of blink behavior might be necessary to understand the relationship. In the final part of the project, I aimed to further understand the function of blinks through their neural correlates. I extracted the blink-related neural activity in the primary visual cortex (V1) of existing recordings of three rhesus monkeys during different sensory processing states. I analyzed spike related multi-unit responses, frequency dependent power changes, local field potentials and laminar distribution of activity while the animal watched a movie compared to when it was shown a blank screen. The results showed a difference in blink-related neural activity dependent on the processing state. This difference suggests a state dependent function of blinks. Taken altogether, the work presented in this thesis suggests that eye blinks have an important function during cognitive and perceptual processes. Blinks seem to facilitate a disengagement from the external world and are therefore suppressed during intended processing of external stimuli.},
  subject      = {Lidschlag},
  language  = {en}
}
@phdthesis{Gschwendtner2013,
  author    = {Gschwendtner, Kathrin M.},
  title     = {Von den Genen zum Verhalten: Der Einfluss des COMT Val158Met Polymorphismus auf visuell-r{\"a}umliche Aufmerksamkeitslenkung bei emotionalen Verarbeitungsprozessen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-83278},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {Der Catechol-O-Methyltransferase (COMT) Val158Met Polymorphismus (rs4680) ist am Abbau von Dopamin und Noradrenalin im menschlichen Gehirn beteiligt. In bisherigen Studien konnte gezeigt werden, dass das Met-Allel mit einer erh{\"o}hten Reaktivit{\"a}t auf negative Stimuli assoziiert ist. Auf Basis der Tonischen/ Phasischen Dopaminhypothese wird postuliert, dass diese erh{\"o}hte Reaktivit{\"a}t auf negative Reize durch defizit{\"a}re Disengagementprozesse verursacht sein k{\"o}nnte. Das Ziel dieser Arbeit war es daher, diese theoretische Annahme mithilfe von Blickbewegungsmessungen zu {\"u}berpr{\"u}fen und zu untersuchen, ob die erh{\"o}hte Reaktivit{\"a}t sich auch in verl{\"a}ngerten Disengagementlatenzen von negativen Reizen widerspiegelt. Es wurden daf{\"u}r drei Studien durchgef{\"u}hrt, in denen eine adaptierte Version der emotionalen Antisakkadenaufgabe in Verbindung mit einer Blickbewegungsmessung eingesetzt wurde. In der zweiten Studie wurde zus{\"a}tzlich eine EEG-Messung durchgef{\"u}hrt. Außerdem wurde in der dritten Studie die Aufmerksamkeitslokation manipuliert. In der ersten und zweiten Studie zeigte sich nicht wie erwartet ein linearer Effekt in Relation zum COMT Val158Met Polymorphismus, sondern ein Heterosiseffekt. Dieser Effekt zeigte sich nur in der einfacheren Prosakkadenbedingung. In der ersten Studie wurde der Heterosiseffekt bei negativen Reizen gefunden, wohingegen in der zweiten Studie der Heterosiseffekt nur in einer EEG- Komponente, der Early Posterior Negativity (EPN), aber sowohl bei positiven als auch negativen Reizen gefunden wurde. In der dritten Studie zeigte sich kein Genotypeffekt. Es wird vermutet, dass der COMT Effekt in der emotionalen Verarbeitung aufgabenspezifisch sein k{\"o}nnte und daher, neben linearen Zusammenh{\"a}ngen, unter bestimmten Umst{\"a}nden auch ein Heterosiseffekt auftreten kann. Die Ergebnisse sollten nicht auf eine m{\"a}nnliche Stichprobe generalisiert werden, da in allen Studien lediglich weibliche Versuchspersonen teilnahmen.},
  subject      = {Dopaminstoffwechsel},
  language  = {de}
}
@phdthesis{Frey2011,
  author    = {Frey, Monika},
  title     = {Effects and mechanisms of a putative human pheromone},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-72292},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {There is evidence that pheromones are communicative signals in animals. However, the existence and function of human pheromones are still under discussion. During the last years several substances have been labeled as putative human pheromones and especially 4,16-androstadien-3-one (androstadienone), found in male and female sweat, became subject of intense investigation. In contrast to common odors androstadienone presumably modulates human physiological and psychological reactions. Data suggest that androstadienone might influence the processing of visual cues, specifically faces or affective stimuli, via projections from the fusiform gyrus and the amygdala. Moreover, attentional processes may be modulated, which is supported by explicit and implicit behavioral data. This thesis includes three experimental studies examining effects of androstadienone exposure on behavioral and cortical reactions to visual and emotional stimuli. The main hypotheses were that androstadienone might influence human behavior to and perception of visual cues. The first study sought to clarify androstadienone effects on attention-related reactions as well as on behavioral tendencies. Motoric approach-avoidance reactions in response to happy and angry facial expressions were investigated in 30 women and 32 men. Participants either inhaled androstadienone or a control solution, without knowing the real content, while performing the following task: they had to push away or to pull towards them a joystick as fast as possible in reaction to either an angry or a happy cartoon face, which was presented on a computer screen. Results showed that androstadienone modulated the participant´s task performance by accelerating the reaction speed compared to the control compound. Faster reactions were observed particularly when reacting to angry faces but not when reacting to happy faces. This might be explained by the finding that human body odors, the source of androstadienone, were found to activate the human fear system, i.e. modulating fear-related attentional processes. Therefore, the quicker reaction towards angry faces with exposure to androstadienone could be due to an enhanced allocation of attentional resources towards fear-related cues like angry faces. Results also showed that androstadienone enhanced men´s approach tendency towards faces independent of emotional expressions. This observation might be explained by androstadienone´s former shown ability to improve attractiveness ratings of other persons. In this regard, the endogenous odor might enhance evaluations of faces in men and, thus, might improve their willingness to approach social stimuli. In contrast to men, women already showed in the control condition higher approach tendency towards faces. Therefore, androstadienone might rather maintain than enhance the approach score in women. In the second study event-related brain potentials (ERPs) triggered by social and non-social visual stimuli were investigated by means of electroencephalography. In a double-blind between-subjects design 51 women participated. Twenty-eight women inhaled androstadienone, whereas 23 women inhaled a control solution. Four different picture categories, i.e. real faces, pictures with couples, pictures with social and non-social scenes, each including three different valence categories, i.e. positive, negative and neutral, should clarify the stimulus type or context androstadienone is acting on. The androstadienone compared to the control odor did not influence brain responses significantly. Explorative analyses, however, suggested that androstadienone influences the processing of faces. While in the control group angry faces elicited larger P300 amplitudes than happy faces, the androstadienone group showed similar P300 amplitudes concerning all emotional expressions. This observation tentatively indicates that the endogenous odor might indeed affect the neuronal responses to emotional facial stimuli, especially late components reflecting evaluative processes. However, this observation has to be verified and further investigated, in particular whether androstadienone caused reduced responses to angry faces or enhanced responses to happy faces. The third study investigated androstadienone effects on face processing especially in men. ERPs elicited by happy, angry and neutral cartoon faces, which were presented on a computer screen, were measured while 16 men, not knowing the applicated odor, inhaled either androstadienone or a control solution. Exposure to androstadienone significantly increased later neuronal responses, the P300 amplitude. This belated component of the ERP reflects attention allocation and evaluative processes towards important stimuli. Therefore, androstadienone might facilitate central nervous face processing by enhancing attention towards these stimuli. In sum, the current results corroborate the notion of androstadienone as an active social chemosignal. In minute amounts and not detectable as an odor it influenced cortical and motoric reactions. Therefore, it might be concluded that androstadienone indeed affects cognitive functions like attentional processes and in turn affects our behavior. The current results further support the notion that androstadienone acts like a human modulator pheromone, namely modulating ongoing behavior or a psychological reaction to a particular context, changing stimulus sensitivity, salience and sensory-motor integration. However, these conclusions remain tentative until further replication takes place, best in ecologically valid environments. Furthermore, one has to keep in mind that the current studies could not replicate several previous findings and could not verify some hypotheses assuming communicative effects of androstadienone. Thus, the main assumption of this thesis that androstadienone is an active chemosignal is still challenged. Also, whether the term "pheromone" is indeed suitable to label androstadienone remains open.},
  subject      = {Pheromon},
  language  = {en}
}