Intrinsic motion pertains to the relative movements of a character’s body parts while mobile, while extrinsic motion pertains to those movements in relation to external landmarks. The current study aimed to explore whether the removal of identifiable features of a person (race and color of clothing) would force witnesses to move their focus to extrinsic motion. Previous studies regarding the concept of intrinsic and extrinsic motion have found that witnesses are more likely to encode intrinsic motion with the identity of a person, while extrinsic motion is encoded separately. This made it easier for participants to recognize an actor based on their manner of movement, rather than where the actor was initially seen. By silhouetting the actors and manipulating the background they were shown in later, the current study was able to identify a negative impact on recognition ability when actors were shown against a background they were not initially shown against while silhouetted. The implications of these results are discussed. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Trois hypothèses principales existent quant aux indices locaux du contour étant les plus informatifs pour le processus de structuration de la forme, et permettant l’identification visuelle des objets : les angles et les indices de tridimensionnalité (Biederman, 1987 ; Boucart et al, 1995), les éléments mi-segments (Kennedy & Domander, 1985, Singh & Fulvio, 2005), et l’interaction entre le type de fragmentation et le degré de spécificité de la forme globale (Panis & Wagemans, 2009). L’objectif de ce travail consiste donc à confronter ces trois hypothèses, en tentant de déterminer par ailleurs le niveau (conscient ou non conscient) auquel s’opèrent la détection et le traitement de ces indices. Les paradigmes d’amorçage supra et infraliminaire sont employés. Des dessins d’objets fragmentés selon deux modes (angles et indices de tridimensionnalité versus éléments mi-segments) sont insérés en tant qu’amorce, précédant une image cible du même objet, elle-même fragmentée et présentant des zones de contours strictement identiques ou complémentaires à l’amorce. Aucune des quatre expériences proposées ne met en évidence un effet « qualitatif » du type de fragmentation. En revanche, certaines conditions temporelles permettent un effet d’amorçage de type lié à la quantité de contour présenté. Nos résultats confirment l’ambiguïté émergeant de la littérature relative aux zones de contours les plus informatives, et semblent conforter la nécessité d’un haut degré d’automaticité des processus impliqués dans la perspective de mettre en évidence des effets d’amorçage perceptif / Three main hypotheses exist concerning the most informative local features of contour for binding processes, allowing visual object identification: vertices and 3D features (Biederman, 1987 ; Boucart et al, 1995), midsegments elements (Kennedy R& Domander, 1985, Singh & Fulvio, 2005), and the interaction betweenfragmentation type and complexity of the global form (Panis & Wagemans, 2009). The aim of this work is to confront these hypotheses, while trying to determine the level (conscious or unconscious) at which the detection and the processing of these features occur. Conscious and unconscious priming paradigms are employed. Drawings of fragmented objects contain either vertices and 3D features or midsegment elements. They are used as primes, preceding a fragmented target image of the same object containing identical or complementary contour features. None of these four experiments highlight a qualitative effect of fragmentation types. However, a quantitative priming effect can be observed under certain timing conditions. Our results confirm the ambiguity emerging from literature concerning the most informative contour features and the necessity of a high degree of automatism of the processes involved in order to highlight perceptual priming effects

Our brains handle vast amounts of information incoming through our senses. Continuously exposed to sensory input, the sense of touch, however, may miss tactile stimuli, no matter how much attention we pay to them. In four empirical studies, this thesis tested (1) the feasibility of investigating undetectable stimulation by electrical finger nerve pulses, (2) how its neural correlates dissociate from detectable stimulation and (3) whether and how selective somatosensory attention nevertheless affects the neural representation of undetectable stimuli. The first two studies showed that there is a natural range of electrical stimulation intensities that cannot be detected. A rigorous statistical evaluation with Bayes factor analysis indicated that the evidence of chance performance after undetectable stimulation reliably outweighed evidence of above-chance performance. A subsequent study applying electroencephalography (EEG) revealed qualitative differences between the processing of detectable and undetectable stimulation, which is evident in altered event-related potentials (ERP). Specifically, undetectable stimulation evokes a single component that is not predictive of stimulus detectability but lacks a subsequent component, which correlates with upcoming stimulus detection. The final study showed that attention nevertheless affects neural processing of undetectable stimuli in a top-down manner as it does for detectable stimuli and fosters the view of attention and awareness being two separate and mostly independent mechanisms. The influence of the pre-stimulus oscillatory (~10 Hz) alpha amplitude—a putative marker of attentional deployment—on the ERP depended on the current attentional state and indicates that both processes are interacting but not functionally matching.:1 Touch, Consciousness, And Attention – Theoretical Considerations ........ 1-11 1.1 A Neural Account To (Un-) Consciousness ............................................ 1-12 1.2 Controlling detectability of external stimulation ...................................... 1-14 1.3 Thresholds in the light of signal detection theory ................................... 1-17 1.4 Selective attention in touch .................................................................... 1-19 1.5 Research questions ............................................................................... 1-21 2 Empirical Evidence .................................................................................... 2-25 2.1 General methods .................................................................................... 2-25 2.1.1 Stimulation ........................................................................................... 2-25 2.1.2 Threshold assessment procedure ....................................................... 2-25 2.1.3 Behavioral analysis .............................................................................. 2-26 2.1.4 Electrophysiological measurement ...................................................... 2-28 2.1.5 Analysis of event-related potentials ..................................................... 2-30 2.1.6 Spectral Analysis resolved over time ................................................... 2-30 2.2 Psychophysical assessment of subthreshold stimulation ........................ 2-33 2.2.1 A method for assessing the individual absolute detection threshold (ADTH) ......................................................................................................... 2-33 2.2.2 Validation of absolute detection threshold assessment by signal detection theory measures and Bayesian Null-Hypothesis testing ................ 2-39 2.3 Non-invasive neural markers of unconscious perception ....................... 2-47 2.3.1 Neural Correlates of Undetectable Somatosensory Stimulation in EEG and fMRI ...................................................................................................... 2-47 2.3.2 Prediction of stimulus perception by features of the evoked potential for different stimulation intensities along the psychometric function ................. 2-51 2.4 The role of Rolandic Alpha Activity in Somatosensation and its Relation to Attention ................................................................................................. 2-75 3 General Discussion and Conclusions ...................................................... 3-101 3.1 Summary of empirical results ................................................................ 3-101 3.2 Neural processing of undetectable stimulation ..................................... 3-102 3.3 Attention, awareness and neural oscillatory activity ............................. 3-104 3.4 Limits of the current studies and future perspectives ........................... 3-109 References .................................................................................................... 113 Summary ....................................................................................................... 137 Zusammenfassung ........................................................................................ 143 Curriculum Vitae ............................................................................................ 151 Selbständigkeitserklärung ............................................................................. 155 Nachweis über die Anteile der Co-Autoren .................................................... 157

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Η σύγχρονη μελέτη της κεντρικής και αυτόνομης δραστηριότητας θεωρούνται χρήσιμες στην ανάδειξη της σχέσης των δύο συστημάτων και της φυγόκεντρου ανατροφοδότησης των περιφερικών αλλαγών. Στην εργασία αυτή διερευνώνται οι πιθανές σχέσεις μεταξύ κεντρικών και αυτόνομων απαντήσεων σε σωματαισθητικούς ερεθισμούς. Η ηλεκτροδερμική δραστηριότητα (ΗΔΑ) είναι δείκτης της αυτόνομης δραστηριότητας. Προκλητά δυναμικά και ΗΔΑ καταγράφονταν ταυτόχρονα έπειτα από μια σειρά ερεθισμών του μέσου νεύρου ,με τρείς διαφορετικές εντάσεις, σε έξι φυσιολογικά άτομα. Η χαμηλότερη ένταση ερεθισμού ρυθμίζονταν έτσι ώστε να μη γίνεται αντιληπτή από το άτομα. Τα επάρματα P40, P100, N200 και P300 των προκλητών δυναμικών εξήχθησαν από το καταγεγραμμένο σήμα. Μελετήσαμε το πλάτος και τον λανθάνοντα χρόνο και διερευνήσαμε την πιθανή συσχέτιση των μεγεθών αυτών της ΗΔΑ. Χρησιμοποιήσαμε την συνηθισμένη μέθοδο της μεσοποίησης (average), καθώς και την προσέγγιση των μοναδιαίων απαντήσεων, εξάγωντας τις απαντήσεις με την χρήση χωρικού φίλτρου. Το συμπαθητικό νευρικό σύστημα φαινόταν να απαντά ακόμα και σε ερεθισμούς μη αντιληπτούς από το υποκείμενο. Η φλοιική επεξεργασία των αντιληπτών και μη ερεθισμάτων όπως αποτυπώνονταν με τα επάρματα των προκλητών δυναμικών, φαίνεται να είναι όμοια και στις δύο περιπτώσεις κατά τη διάρκεια των πρώτων 40ms έπειτα από τον ερεθισμό, ενώ τα μακρά κύματα ήταν απόνατ στους μη αντιληπτούς ερεθισμούς. Τα πλάτη της ΗΔΑ και του P300 με την προσέγγιση των μοναδιαίων απαντήσεων παρουσίαζαν μια σημαντική θετική συσχέτιση. / Concurrent studies of central and autonomic activity are considered useful in elucidating the relationship between the two systems and indicating the centripetal feedback of peripheral changes. The SSR (sympathetic skin response) is one index of autonomic arousal. In our study we examine the possible relationships between central and autonomic responses to somatosensory stimuli. EPs (evoked potentials) and SSRs were simultaneously recorded during a series of electrical stimuli of median nerve in six normal adults using three different intensities of stimuli. The weakest of them was unperceived by subject. The P40, P100, N200 and P300 waves of EPs were extracted and their latencies and amplitudes were analysed in order to find correlations with those of the SSRs. We used the conventional method of signal averaging and the single trial (ST) approach, as the EP waves were subtracted by spatial filtering. Interestingly, sympathetic nervous system seemed to react even to stimuli unperceived by the subject. The cortical processing of consciously perceived and unperceived somatosensory stimuli as it was expressed by the evoked potentials seems to be identical during the first 40ms after the stimulus onset while later waves were absent for unperceived stimuli. SSR and P300 amplitude at the ST level had a positive correlation.