The term biological motion has been coined by G. Johansson (1973) to refer to the ambulatory patterns of terrestrial bipeds and quadripeds. In this paper a computational theory of the visual perception of biological motion is proposed. The specific problem addressed is how the three dimensional structure and motions of animal limbs may be computed from the two dimensional motions of their projected images. It is noted that the limbs of animals typically do not move arbitrarily during ambulation. Rather, for anatomical reasons, they typically move in single planes for extended periods of time. This simple anatomical constraint is exploited as the basis for utilizing a "planarity assumption" in the interpretation of biological motion. The analysis proposed is: (1) divide the image into groups of two or three elements each; (2) test each group for pairwise-rigid planar motion; (3) combine the results from (2). Fundamental to the analysis are two 'structure from planar motion' propositions. The first states that the structure and motion of two points rigidly linked and rotating in a plane is recoverable from three orthographic projections. The second states that the structure and motion of three points forming two hinged rods constrained to move in a plane is recoverable from two orthographic projections. The psychological relevance of the analysis and possible interactions with top down recognition processes are discussed.

Observers can retrieve the facing direction of a walker from point-light displays that are devoid of structure-from-motion information and retain solely local motion signals. This ability is orientation-dependent and relies on the motions representing the feet of the agent. The experiments described here were designed to investigate visual sensitivity to local cues contained in biological motion. Initial experiments revealed that local biological motion carries information about animacy in addition to the agent’s facing direction in an orientation-dependent manner (Chapter 2). The mechanism underlying the perception of local biological motion can be dissociated from that underlying the retrieval of global structure-from-motion information according to characteristics such as sensitivity to learning and noise (Chapter 3). Further experiments revealed that the orientation-dependency for perceiving local biological motion is carried by vertical acceleration in the foot’s motion (Chapter 4). The importance of acceleration for biological motion perception raises the need to achieve a better understanding of acceleration sensitivity across various parameters such as stimulus size. To this end, Chapter 5 showed that acceleration thresholds for perceiving a linearly accelerating stimulus scale according to mean velocity as predicted by size invariance and are inversely proportional to stimulus duration. An important role for acceleration for the perception of biological motion was further corroborated by findings in an evolutionarily guided psychophysical search for the adequate local motion, defined as one that carries maximal directional information and a large inversion effect (Chapter 6). Finally, although orientation-dependency is a pervasively demonstrated characteristic of biological motion perception, the reference systems in which the stimuli are encoded are unclear. The experiments in Chapter 7 revealed that both global structure and local motion aspects of biological motion, like faces, are primarily coded in an egocentric frame of reference. Unlike faces however, there is an additional contribution of non-visual information about gravity for the perception of biological motion. These findings are finally discussed in the context of emerging behavioural, neuroimaging, and electrophysiological work that further characterize a local motion mechanism that is proposed to serve as a fundamental first stage towards interpreting animate motion patterns. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2010-07-21 08:34:58.564

No description available.

Biological motion perception, defined as the ability to retrieve information from minimal displays of animal motion, has often been discussed as though it represents a single mechanism. However, depending on the task and details of the stimuli, there have been divergent results as to whether this ability is primarily based on motion or form processing, whether it relies more on local or global information, and whether the knowledge that is applied is learned or innate. These results can be reconciled by a multi-component framework, with five major components: local motion invariant processing, structure-from-motion, figure-ground segregation, action categorization, and style recognition. Several experiments are reported that are motivated by this framework. To investigate the sensitivity of the visual system to local motion invariants, performance was tested on a direction discrimination and a detection task with a point-light walker based on real motion-capture data or a synthetic walker created by Cutting (Chapter 2). When the walkers were displayed normally, performance was equal for both stimuli. However, when the walkers were spatially scrambled, the direction could only be determined for the natural walker, demonstrating that the invariant is found in subtle features of the local motion trajectories. Another experiment examined the difference in attentional distribution due to the task requirements (Chapter 3). Participants looked more often at the feet in a direction task than they did in a gender task, lending support to the idea that useful information can be derived from the local motion of the feet. Finally, Chapter 4 describes a battery of psychophysical tests that assesses each of the components of biological motion perception as independently as possible. The fact that individual performance does not correlate between tests is evidence that they measure different underlying mechanisms, supporting the multi-component framework. In the concluding chapter, multi-component computational models of biological motion perception are evaluated within this framework, and the evidence relating the components to activity in particular brain regions is reviewed. / Thesis (Ph.D, Psychology) -- Queen's University, 2011-05-27 09:25:30.774

Orthographically-projected biological motion point-light displays generally contain no information about their in-depth orientation, yet observers consistently prefer the facing-the-viewer (FTV) interpretation (Vanrie, Dekeyser and Verfaillie, 2004). This bias has been attributed to the social relevance of such stimuli (Brooks et al., 2008) although local stimulus properties appear to influence the bias (Schouten, Troje and Verfaillie, 2011). In the present study we investigated the cause of the FTV bias. In Experiment 1 we compared FTV bias for various configurations of stick-figures and depth ambiguous human silhouettes. The FTV bias was not present for silhouettes, but was strongly elicited for most stick-figures. We concluded that local attitude assignments for intrinsic structures of stick-figures are subject to inferences about the flexion of body surfaces, and that a visual bias that assumes surfaces to be convex drives the FTV bias. In Experiment 2 we manipulated silhouettes to permit local attitude assignments by using point-lights on emphasized flexion points. As predicted, the inclusion of intrinsic structures produced FTV bias for silhouettes. The results help to unify various findings regarding the FTV bias. We conclude that the FTV bias emerges during the 2 ½-D sketch stage of visual processing (Marr and Nishihara, 1978). / Thesis (Master, Psychology) -- Queen's University, 2013-08-08 19:06:06.84

The visual recognition of complex movements and actions is crucial for communication and survival in many species. Remarkable sensitivity and robustness of biological motion perception have been demonstrated in psychophysical experiments. In recent years, neurons and cortical areas involved in action recognition have been identified in neurophysiological and imaging studies. However, the detailed neural mechanisms that underlie the recognition of such complex movement patterns remain largely unknown. This paper reviews the experimental results and summarizes them in terms of a biologically plausible neural model. The model is based on the key assumption that action recognition is based on learned prototypical patterns and exploits information from the ventral and the dorsal pathway. The model makes specific predictions that motivate new experiments.

<p>Previous studies have reported inconsistent results for people with Autism Spectrum Disorders (ASD) in both biological motion and Navon tasks. Each of these tasks require both local and global processing and were used in this study to compare processing styles of both ASD and typical groups. In the biological motion study, the ASD and the typical groups completed an emotion and a direction-discrimination experiment with happy and angry point-light walkers, which were presented in four different stimulus conditions: upright, inverted, scrambled and random. Overall, the ASD group had higher reaction times and lower accuracy, but the effect of condition did not differ between groups. Both groups performed worse in terms of accuracy and reaction times in the scrambled (i.e., local information only) conditions, therefore revealing a global bias in the processing of biological motion information. In the Navon task study with the same participants, typical individuals exhibited a global precedence effect, manifested as lower reaction times for global stimuli as well as global interference in “look for only local digits” task. However, individuals in the ASD group did not, on average, show a local or a global bias. In a subsequent analysis, the ASD group was divided into locally-biased and globally-biased sub-groups. Now, when a three way analysis between typical and the two ASD groups was performed, the globally-biased group’s performance was not distinguishable from that of the typical group, while no global bias was observed for the locally-biased group. When these two groups were compared on the Biological Motion study, the locally-biased group had no reaction time difference across conditions including both biological motion and Navon tasks, unlike the globally-biased group, who displayed higher reaction times for the scrambled condition, just like the typical group did. Therefore, it is possible that the inconsistencies in the local-global processing literature of individuals with ASD may have resulted because the studies did not account for individual differences in processing styles within the ASD groups that may be variable, unlike typical individuals who have a global bias for most tasks.</p> / Master of Science (MSc)

Despite a rise in the use of “learning by doing” pedagogical methods in praxis, little is known as to how the brain benefits from these methods. Learning by doing strategies that utilize complementary information (“enrichment”) such as gestures have been shown to optimize learning outcomes in several domains including foreign language (L2) training. Here we tested the hypothesis that behavioral benefits of gesture-based enrichment are critically supported by integrity of the biological motion visual cortices (bmSTS). Prior functional neuroimaging work has implicated the visual motion cortices in L2 translation following sensorimotor-enriched training; the current study is the first to investigate the causal relevance of these structures in learning by doing contexts. Using neuronavigated transcranial magnetic stimulation and a gesture-enriched L2 vocabulary learning paradigm, we found that the bmSTS causally contributed to behavioral benefits of gesture-enriched learning. Visual motion cortex integrity benefitted both short- and long-term learning outcomes, as well as the learning of concrete and abstract words. These results adjudicate between opposing predictions of two neuroscientific learning theories: While reactivation-based theories predict no functional role of specialized sensory cortices in vocabulary learning outcomes, the current study supports the predictive coding theory view that these cortices precipitate sensorimotor-based learning benefits.:I. Abkürzungsverzeichnis II. Abbildungsverzeichnis III. Einleitung 1. Fremdsprachenlernen 1.1 Sensorische Modalitätsvergleiche 1.2 Sensomotorisches Lernen 2. Lerntheorien 2.1 Theorie des prädiktiven Kodierens 2.2 Theorie des prädiktiven Kodierens für multisensorisches Lernen 3. Sulcus temporalis superior für biologische Bewegung 4. Transkranielle Magnetstimulation 4.1 Passagere Funktionsinhibition mittels transkranieller Magnetstimulation IV. Ableitung der Rationale V. Publikationsmanuskript VI. Zusammenfassung VII. Literaturverzeichnis VIII. Appendix A. Abbildungen B. Ergänzendes Material der Publikation C. Darstellung des eigenen Beitrags D. Erklärung über die eigenständige Abfassung der Arbeit E. Lebenslauf F. Publikationen G. Danksagung

Schizophrenia (SCZ) is associated with robust social deficits, which have been shown to precede illness onset and predict functional outcome. As a result, social functioning is an important developmental domain affected by SCZ, which likely has a downstream negative impact on other functional abilities, such as interpersonal relationships and vocational capacity. Patients with SCZ also demonstrate significant visual perceptual deficits; however, a remaining question is whether basic impairment in visual processing gives rise to the deficits observed in social perception. In this context, previous research has shown that biological motion contains relevant social information, such as emotional states and intention, which is easily interpreted by healthy observers. Given that biological motion perception is an important source of social information, and that patients with SCZ have known visual perceptual impairment including motion processing deficits, it is possible that poor biological motion perception meaningfully impacts social perception among individuals with SCZ. While previous studies have documented preliminary evidence of biological motion processing deficits in this population, there is a current lack of understanding regarding the basic visual perceptual mechanisms that may underpin this impairment, including the importance of basic visual motion processing with respect to biological motion. Moreover, the ability of individuals with SCZ to extract relevant social information from biological motion, and its relationship with social perception more generally, have yet to be investigated. Thus, the specific aims guiding the current thesis were to examine whether basic visual motion processes may give rise to biological motion deficits and to examine the ability of individuals with SCZ to extract social information, in the form of emotion, from biological motion. Several experimental tasks were used to examine these aims. Overall, the results from this thesis confirm that individuals with SCZ have difficulty perceiving biological motion; however, this deficit was not specific to biological motion, but instead reflected more widespread visual motion processing deficits, including impairment in global coherent motion perception. Additionally, results from this thesis suggest that individuals with SCZ demonstrated disproportionate difficulty extracting social cues, in the form of emotion, from biological motion, and that this deficit was related to perceiving unambiguous expressions of emotion. In contrast, the discrimination of more subtle or ambiguous emotion was relatively preserved. Moreover, impairment in biological motion processing was found to be unrelated to social perceptual abilities among individuals with SCZ. These experiments provide interesting suggestions regarding clinical approaches to treatment and remediation, although further research is needed to fully understand the brain- behaviour mechanisms underlying SCZ-related deficits in biological motion processing. / Dissertation / Doctor of Philosophy (PhD) / As people navigate though day-to-day life, they encounter many objects in the world that move, such as other people. Research has shown that humans are adept at discriminating human movement and accurate in discerning the emotional states of other people based on this movement. These observations have lead researchers to speculate that, because biological motion is both easy to discriminate and emotionally informative, it plays an essential role in social processing among humans. Research has shown that individuals with Schizophrenia have difficulty understanding social environmental cues, such as the emotions of others. As such, this thesis aims to determine first, whether people with Schizophrenia have difficulty identifying human motion, and second, if they are able to identify emotions embedded within human motion. This thesis will help researchers understand and explain deficits in social perception among people with Schizophrenia.

Facial motion provides an abundance of information necessary for mediating social communication. Emotional expressions, head rotations and eye-gaze patterns allow us to extract categorical and qualitative information from others (Blake & Shiffrar, 2007). Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterised by a severe impairment in social cognition. One of the causes may be related to a fundamental deficit in perceiving human movement (Herrington et al., 2007). This hypothesis was investigated more closely within the current thesis. In neurotypical controls, the visual processing of facial motion was analysed via EEG alpha waves. Participants were tested on their ability to discriminate between successive animations (exhibiting rigid and nonrigid motion). The appearance of the stimuli remained constant over trials, meaning decisions were based solely on differential movement patterns. The parieto-occipital region was specifically selective to upright facial motion while the occipital cortex responded similarly to natural and manipulated faces. Over both regions, a distinct pattern of activity in response to upright faces was characterised by a transient decrease and subsequent increase in neural processing (Girges et al., 2014). These results were further supported by an fMRI study which showed sensitivity of the superior temporal sulcus (STS) to perceived facial movements relative to inanimate and animate stimuli. The ability to process information from dynamic faces was assessed in ASD. Participants were asked to recognise different sequences, unfamiliar identities and genders from facial motion captures. Stimuli were presented upright and inverted in order to assess configural processing. Relative to the controls, participants with ASD were significantly impaired on all three tasks and failed to show an inversion effect (O'Brien et al., 2014). Functional neuroimaging revealed atypical activities in the visual cortex, STS and fronto-parietal regions thought to contain mirror neurons in participants with ASD. These results point to a deficit in the visual processing of facial motion, which in turn may partly cause social communicative impairments in ASD.