Eukaryotic cell chemotaxis, or directed cell migration in response to a chemoeffector gradient, plays a central role in many important biological process such as wound healing, cancer metastasis, and embryogenesis. In vivo, cells migrate on fibrous ECM, but chemotaxis studies are typically conducted on flat substrates which fail to recapitulate ECM or 3D gel environments with heterogeneous and poorly defined biophysical properties. To address these challenges, this thesis focused on developing a microfluidic assay device which utilizes a reductionist approach to study single cell chemotaxis on aligned, suspended ECM-mimicking nanofibers. The device is comprised of a network of microfluidic mixing channels which produce a temporally invariant, linear chemical gradient over nanofiber scaffolds in an observation channel. The microfluidic device design was guided by a numerical model and validated with experimental testing. This device was used to study mouse embryonic fibroblast NIH/3T3 response to platelet derived growth factor (PDGF) on flat polystyrene and suspended, polystyrene nanofibers with small (15 μm), and large (25 μm) spacing. Cell aspect ratio is lowest for flat polystyrene (spread morphology) and highest for large-spaced fibers (spindle morphology). Cells migrating on fibers begin to show a chemotaxis response to a PDGF gradient 10 times shallower than that required for chemotaxis response on a flat substrate. Furthermore, cells with spindle morphology maintain a robust and strong response over a broad range of chemoattractant concentration. These cells also had a 45% increase in speed and 26% increase in persistence over cells on flat polystyrene. The findings of this thesis suggest that 2D substrates may not be sufficient for studying physiologically relevant chemotaxis. / Master of Science

No / The purpose of this article is to determine the relative importance to adaptive locomotion of peripheral visual cues provided by different parts of the visual field. Twelve subjects completed obstacle crossing trials while wearing goggles that provided four visual conditions: upper visual field occlusion, lower visual field occlusion (LO), circumferential peripheral visual field occlusion (CPO), and full vision. The obstacle was either positioned as a lone structure or within a doorframe. Given that subjects completed the task safely without cues from the lower or peripheral visual field, this suggests that subjects used exteroceptive information provided in a feed-forward manner under these conditions. LO and CPO led to increased foot placement distance from the obstacle and to increased toe clearance over the obstacle with a reduced crossing-walking velocity. The increased variability of dependent measures under LO and CPO suggests that exproprioceptive information from the peripheral visual field is generally used to provide online control of lower limbs. The presence of the doorframe facilitated lead-foot placement under LO by providing exproprioceptive cues in the upper visual field. However, under CPO conditions, the doorframe led to a further reduction in crossing velocity and increase in trail-foot horizontal distance and lead-toe clearance, which may have been because of concerns about hitting the doorframe with the head and/or upper body. Our findings suggest that exteroceptive cues are provided by the central visual field and are used in a feed-forward manner to plan the gait adaptations required to safely negotiate an obstacle, whereas exproprioceptive information is provided by the peripheral visual field and used online to “fine tune” adaptive gait. The loss of the upper and lower peripheral visual fields together had a greater effect on adaptive gait compared with the loss of the lower visual field alone, likely because of the absence of lamellar flow visual cues used to control egomotion.

Nos recherches ont porté sur l'étude des indices d'orientation (sonores et verbaux) de l'attention auditive dans une situation d'écoute dichotique au cours du développement. Quatre expériences ont été proposées à des enfants âgés de 8 à 12 ans ainsi qu'à des adultes. Si les deux types d'indices permettent aux populations adultes d'orienter efficacement leur attention vers leurs deux oreilles pour identifier les stimuli cibles et pour résoudre les conflits cognitifs induits par les conditions d'orientation, en revanche, seuls les enfants de plus de 9 ans utilisent les indices verbaux pour orienter efficacement leur attention et résoudre les conflits cognitifs. L'ensemble des résultats suggère (a) que les capacités d'orientation de l'attention se développent en synergie avec le développement cérébral (maturation du cortex préfrontal qui connait une accélération vers 9 ans) et (b) que des indices verbaux favorisent une orientation efficace de l'attention des enfants de moins de 9 ans ainsi que des performances élevées d'identification des stimuli dans leurs deux oreilles. Nous avançons l'hypothèse selon laquelle le rôle facilitateur des indices verbaux résulterait de la pré-activation des processus top-down qu'ils suscitent. En effet, les processus top-down s'avèrent être nécessaires à un contrôle attentionnel de qualité. Ainsi, la présentation de ces indices favoriserait l'activation de ces processus, qui sont difficilement sollicités par les jeunes enfants. L'immaturité du cortex pré-frontal des enfants de moins de 9 ans pourrait expliquer les difficultés d'activation spontanée. / Our work focused on the study of auditory orienting attention cues (with tone cues and verbal cues) in dichotic listening situations across development. Four experiments were carried out with 8 to 12 years old children and with adults. If adults appeared to benefit from the use of tone cues as much as the use of verbal cues to improve their performance of identification in both ears, and thus to improve their cognitive control, however, only 9 years old children took advantage of verbal cues to orient more efficiently their attention and resolve cognitive conflicts. Below this age, only tones cues helped the children to orient and control their attention to the indicated ear.Altogether our results reveal that (a) auditory orienting capacities develop in synergy with cerebral development (the maturation of the prefrontal cortex increases at around 9 years of age), and that (b) verbal cues lead to an efficient orientation of attention and high performance of identification in both ears, even under the age of 9.We suggest that the facilitator role of verbal cues could result from the pre-activation of the top-down processes that they involve. Indeed, top-down processes are essential for cognitive control. Therefore, the presentation of this type of cues would enhance the activation of processes that are not so easily recruited by young children. The immaturity of the pre-frontal cortex of children below 9 years of age could explain the difficulties encountered by this age group.

Die Dissertation untersucht 1) welche Cues Kinder und Erwachsene in ihrer Cuebox haben, d.h. welche Cues für Inferenzen herangezogen wird, 2) wie Intuition über die Wichtigkeit von Cues die Informationssuche beeinflusst, und 3) wie das Framing eines Problems und das experimentelle Design die Intuition beeinflussen. Das erste Projekt untersucht den Effekt verschiedener Domänen und Objektrepräsentationen auf Erfragungsstrategien von Kindern und Erwachsenen in einer Kategorisierungsaufgabe. Ergebnisse zeigen, dass eine Basis-Level-Repräsentation (z.B. Hund) das Generieren von höher geordneten Merkmalen, welche die Objekte innerhalb einer übergeordneten Kategorie unterscheiden, für Kinder erleichtern und dadurch benutzt werden können, um effektive Fragen zu stellen. Dieser Effekt wurde nicht gefunden, wenn Kinder nicht selbst solche Merkmale generierten, sondern aus einem vordefinierten Set auswählen mussten. Das zweite Projekt untersuchte Kinder und junge Erwachsene bezüglich zweier Inferenzprobleme. In einer Bedingung mussten Cues selbst generiert werden, in einer anderen wurde ein Set von Cues vorgegeben. Ergebnisse zeigen, dass nur, wenn Cue selbst generiert wurden, junge Kinder gleich gut oder besser als ältere Kinder oder Erwachsene abschnitten, da sie Cues generierten, die ebenso informativ waren wie die der anderen beiden Altersgruppen. In dem dritten Projekt wurde getestet, wie die Art, Anzahl und Qualität der Cues die Fähigkeit von Kindern und jungen Erwachsenen beeinflusst, die informativsten Cues zu generieren bzw. auszuwählen. Ergebnisse zeigen, dass die Cuebox von Kindern mehr perzeptuelle Cues beinhaltet als jene junger Erwachsener. Dennoch war der Informationsgehalt der generierten Cues in beiden Gruppen gleich. Junge Erwachsene zeigten die Tendenz, nicht-perzeptuelle Cues systematisch als informativer zu erachten als perzeptuelle Cues. Kinder zeigten die gleiche Tendenz nur dann, wenn sie aus einem vordefinierten Set auswählen mussten. / My dissertation addresses the questions 1) what cues children and adults have in their cuebox (i.e., the set of cues available for making inferences or categorizing), 2) how people’s intuition about the importance of the cues drives their information search, and 3) how the framing of a problem and the experimental design influence these intuitions. A first project investigated developmental differences in how children and adults solve a sequential binary categorization task. Results show that, apart from age-related differences, children’s but not adults’ inquiry strategies improve if objects are represented at the basic level (e.g., dog) but not if represented at the subordinate level (e.g., Dalmatian) or when the basic level is specified by additional features (e.g., dog, kennel, to wag, collar). Explanations are that, unlike other representations, basic level objects trigger features that are useful for categorization, and therefore help children ask more effective questions. A second project tested children and young adults on two inference problems, by manipulating whether cues were generated or given. Results show that, only when generating their own cues, younger children matched or even outperformed the accuracy of older children and young adults, by generating cues that were as informative as the those generated by older children and young adults. A third project examined the type, amount and informativeness of the cues in people’s cuebox. Further, it investigated the influence of the type of cues on the ability of children and young adults to generate or select the most informative cue available. Results show that children’s cuebox contains more perceptual cues than young adults’. We found no difference between the two age groups in terms of informativeness of the cues generated. Young adults showed the tendency to systematically consider non-perceptual cues more informative than perceptual cues. Children showed such tendency only in a cue-selection task.

The research was undertaken to quantify the power of selected extrinsic (price and country of origin) and intrinsic cues (acid in chardonnay and fat in brie) on consumer evaluations of both experienced and expected product quality, and further, to measure the respective influences of objective knowledge, subjective knowledge and self-confidence on these quality assessments. The study also seeks to determine if a survey conducted measuring expectations of quality would yield comparable results with quality assessments based on actual product experience. The study was comprised of sensory experiments using full profile conjoint analysis experimental design to measure quality perception, followed by a survey where only product description profiles were provided. The analysis from both stages show findings that are remarkably similar in most respects. Results of the sensory experiment for chardonnay show both extrinsic cues tested to be more important than acid levels, while results for the survey show price maintained the strongest influence, with comparable expectations regarding the importance of country of origin and acid. For brie (both stages) consumer opinions were consistent; with price found the most influential; and while country of origin was considered relatively important, fat levels were more influential for both groups. Whilst for chardonnay (both stages) respondents held consistent beliefs regarding each acid level tested, for brie respondents experiencing the highest level of fat held an opposite view to respondents assessing quality based on their expected liking for this type of product. The influence of knowledge (objective and subjective) and self-confidence was found to be sporadic and weak, likely due to respondents’ general lack of objective knowledge in both stages of the survey. In the case of self-confidence, results are surprising given that respondents in both studies exhibited reasonably healthy degrees of self-confidence. The research provides important information to marketers seeking to exploit the most attractive aspects of their products and platform for a number of subsequent studies. / Thesis(PhD)-- School of Commerce, 2007

In einer multiplen Einzelfallstudie mit zehn aphasischen Patienten wurde die Wirksamkeit eines semantischen und eines phonologischen Therapieansatzes zur Behandlung von Wortabrufstörungen verglichen. Detaillierte Einzelfalluntersuchungen ermöglichten die Diagnose der zugrundeliegenden funktionalen Störungen bei jedem Patienten. Auf diese Weise konnten die erzielten Therapieeffekte auf die individuellen kognitiv-neurolinguistischen Störungsmuster bezogen werden. Im Vordergrund der Therapie stand in beiden Ansätzen das mündliche Benennen von Objektabbildungen mit unterschiedlichen Arten von Hilfen. Während in der semantischen Therapie Teilaspekte des semantischen Zielkonzepts als Benennhilfen eingesetzt wurden, handelte es sich bei den phonologischen Hilfen um Teilinformationen der Zielwortform. Bei der Erhebung von spezifischen Therapieeffekten wurde zwischen itemspezifischen und itemübergreifenden Verbesserungen sowie kurz- und langfristigen Effekten auf die mündlichen Benennleistungen unterschieden. Dabei wurden neben den quantitativen Verbesserungen (% korrekt) auch die qualitativen Effekte (Fehlertypen) der beiden Ansätze berücksichtigt, und es wurden Transfereffekte in die Spontansprache der Patienten untersucht. Zusätzlich wurden auch die Soforteffekte der verschiedenen Benennhilfen in den Therapiesitzungen erhoben. Im Methodenvergleich zeigte sich, dass die phonologische Therapiephase kurzfristig bei der Mehrzahl der Patienten signifikante Verbesserungen beim Bildbenennen bewirkte, diese Effekte haben sich jedoch überwiegend als nicht stabil erwiesen. Im Gegensatz dazu erwies sich die semantische Therapiephase auch als langfristig effektiv. Im Unterschied dazu erwiesen sich die phonologischen Benennhilfen bei fast allen Patienten als unmittelbar effektiver als die semantischen Benennhilfen. Somit waren die Soforteffekte der Hilfetypen in den Therapiesitzungen kein sicherer Indikator für die Dauer der Gesamteffekte einer Therapiephase. Außerdem zeigte sich nicht bei allen Patienten ein direkter Zusammenhang zwischen der Art ihrer zugrundeliegenden funktionalen Störung und den erzielten Therapieeffekten. Einerseits profitierten Patienten mit erhaltenen semantischen Verarbeitungsleistungen von der semantischen Therapie, andererseits zeigten sich signifikante phonologische Therapieeffekte bei Patienten mit zentral-semantischen Störungen. Die Wirkmechanismen der beiden Therapieansätze werden unter Berücksichtigung unterschiedlicher kognitiv-neurolinguistischer Theorien zum mündlichen Wortabrufprozess beim Bildbenennen interpretiert. / This study compared semantic and phonological treatments of word retrieval in ten aphasic patients using a multiple single case paradigm. The patients' single word processing was investigated before therapy, so that specific treatment effects could be interpreted with regard to underlying functional deficit(s) in each patient. In both treatments, the main task was spoken picture naming with different types of cues. In the semantic treatment, different aspects of the semantic target concept were used as a cue in picture naming, in the phonological treatment, different types of word-form specific information were provided as a cue. Treatment effects were assessed in terms of both short- and long-lasting effects on spoken picture naming accuracy in each patient. Both quantitative (proportion of correct responses) and qualitative (error types) improvements were evaluated. Furthermore, generalisation to untreated pictures (control items) and related tasks and transfer effects into spontaneous speech were examined. In addition, the immediate effects of the different types of prompts in the phonological and semantic treatment sessions were analysed. Regarding the stability of effects, different outcomes were found for semantic versus phonological treatments. The phonological treatment phase produced only short-lasting effects in most of the patients. In contrast, the semantic treatment phase produced more stable effects in some participants. With regard to the immediate effects of the different types of cues in the treatment sessions, it turned out that the phonological cues produced stronger effects than the semantic cues in most of the participants. Nevertheless, the effects of the semantic treatment phase were more stable than the phonological treatment effects. Specific effects of the phonological and the semantic treatment were not directly linked to the underlying functional disorder in each patient. Patients with preserved and with impaired semantic processing of concrete nouns could profit from both methods. The underlying mechanisms of effectiveness of the two treatment methods are interpreted in the framework of different cognitive-neuropsychological theories of spoken picture naming.

The preferential looking paradigm was used to investigate how toddlers integrate recently learned grammatical cues with well-established social cues in a novel word-learning scenario. To test this we examined children’s ability to decipher the referent of a novel noun using the grammatical information from a plural cue and social information from an eye-gaze cue. Experiment 1 is the first study showing that children as young as 24 months of age can rely on plural markings alone to infer the referent of a novel noun. Preliminary results of Experiment 2 suggest that when the plural cue is presented alongside contradicting information from a gaze direction cue, children still map the novel word to the grammatically cued object. Taken together, these results suggest that by the time children reach their second birthday, even newly learned grammatical information, such as plural markings, might already outweigh established social cues.

The preferential looking paradigm was used to investigate how toddlers integrate recently learned grammatical cues with well-established social cues in a novel word-learning scenario. To test this we examined children’s ability to decipher the referent of a novel noun using the grammatical information from a plural cue and social information from an eye-gaze cue. Experiment 1 is the first study showing that children as young as 24 months of age can rely on plural markings alone to infer the referent of a novel noun. Preliminary results of Experiment 2 suggest that when the plural cue is presented alongside contradicting information from a gaze direction cue, children still map the novel word to the grammatically cued object. Taken together, these results suggest that by the time children reach their second birthday, even newly learned grammatical information, such as plural markings, might already outweigh established social cues.

Ephemeral patches of hydrodynamic and chemical sensory cues at fine scales are fundamentally important to the life success of plankton populations and thus the overall health and vitality of nearshore marine ecosystems. We employed various tools from experimental fluid mechanics to create ecologically-relevant hydrodynamic and chemical conditions in a recirculating flume system for zooplankton behavioral assays. The goal was to quantify and correlate changes in zooplankton behavior with coincident sensory cues. A laminar, planar free jet (the Bickley jet) was used to create finescale, free shear layers with targeted hydrodynamic characteristics as well as finescale, sharp-edged layers of both beneficial and toxic ("red tide") phytoplankton species. Planar particle image velocimetry (PIV) and laser-induced fluorescence (LIF) were used to quantify the flow and concentration fields, respectively. Behavioral assays with a variety of crustacean zooplankton species including Antarctic krill (Euphausia superba), estuarine crab larvae (Panopeus herbstii), and calanoid copepods (Temora longicornis and Acartia tonsa), each unique in its ecology, morphology, and life history, show clear and statistically-significant behavioral responses to relevant hydrodynamic and chemical cues. Estuarine crab larvae optimize short term and long term behavioral needs (foraging and habitat selection) by sensing and exploiting the information contained in multi-directional free shear flows. In the presence of thin layers of toxic algal exudates (Karenia brevis), T. longicornis and A. tonsa exhibit explicit avoidance behaviors through significant increases in swimming speed and overall behavioral variability resulting in a conspicuous hydrodynamic signature in a risk/benefit behavioral response. Finally, Antarctic krill exploit the hydrodynamic cues contained in a free shear layer to modify swimming behaviors and ultimately graze in a thin phytoplankton layer (Tetraselmis spp.). Each species is able to sense and exploit the information contained in coherent hydrodynamic and chemical sensory cues to change swimming kinematics and alter macroscale trajectory characteristics. Quantifying changes in zooplankton behavior in response to ecologically-relevant sensory cues is a crucial step towards modeling (e.g. via biophysically-coupled individual-based ecosystem models) and managing sustainable marine fisheries.

This study examined the role of olfactory and visual cues in host finding of the pine bark beetles Hylastes ater and Hylurgus ligniperda and the burnt pine longhorn beetle Arhopalus ferus. The ultimate aim of this research was to provide new information on attractant and repellent (such as non-host leaf volatiles) stimuli to improve monitoring methods and reduce the attack by wood-boring and bark beetle species. A field trapping trial of visual and olfactory cues near Nelson caught 7842 H. ater, 274,594 H. ligniperda and 16,301 A. ferus adults. There were significant effects of both visual (colour and sihoutte) and olfactory (host and non-host volatiles) cues for all three species. The highest catches were in black (host mimicking), panel flight intercept traps baited with attractant (α-pinene and ethanol) and the lowest in clear or white (non-host mimicking) control traps. The repellent, green leaf volatiles (GLV) ((E)-2-hexen-1-ol & (Z)-3-hexen-1-ol) when present on traps with attractant reduced catches significantly but modestly in H. ater and H. ligniperda, but had no significant effect on A. ferus. A field trial near Christchurch found that GLV applied as a topical repellent halved the number of beetles attacking Pinus radiata logs. This reduction was significant in H. ligniperda, but not quite (P = 0.07) in H. ater. Placing logs among broadleaved plants (natural sources of non-host volatiles) significantly reduced attack of H. ligniperda by about 75% compared to logs in the open, but had no effect on H. ater. Attack by H. ater was found on 4% of 500 P. radiata seedlings in a field trial near Dunedin. Treatment of seedlings with GLV significantly affected the severity and proportion of seedlings attacked by H. ater, compared with insecticide-treated and control seedlings, but the treatment effect was apparently driven by an unexpected direct damaging effect of GLV on the health of seedlings. It is recommended that future research explores the use of non-host volatiles from natural sources that influence host finding in wood–boring and bark beetle species for the protection of plantation forests in New Zealand.