Human adolescents exhibit higher levels of sensation seeking behaviour than younger or older individuals, and sensation seeking is higher in males than females from adolescence onwards. Data suggest that changes in gonadal hormone levels during adolescence and differences in the dopamine neurotransmitter system are the bases for why some people exhibit sensation seeking behaviour while others do not. However, causal relationships between physiology and behaviour have been difficult to establish in humans. In order to explore the physiological influences on novelty-seeking behaviour, we looked at response to novelty in a laboratory rodent. This research examined responses to novelty in the conditioned place preference (CPP) task and the novel object recognition (NOR) task in Lister-hooded rats, and assessed the benefits and limitations of each methodology. While the CPP task was not found to provide a reliable measure of response to novelty, the NOR task was more successful. In order to understand the ontogeny of sex differences in novelty responses, both males and females were tested from adolescence through to adulthood. While no sex difference was found in adults in the NOR test, mid-adolescent males exhibited higher novelty preference behaviour than either younger or older males, or females at each stage of development. Since gonadal hormones levels rise during adolescence, a pharmacological agent (a gonadotrophin-releasing hormone antagonist) was used to suppress gonadal hormone levels from early adolescence before again examining responses on the NOR test at mid-adolescence. Gonadal hormone suppression from early adolescence onwards eliminated the sex difference in the NOR test at mid-adolescence by reducing the male response to novelty, while no difference was measured in the female animals. These findings suggest that gonadal hormones play a significant role in the development of response to novelty, especially in males, and the implications for our understanding of human sensation-seeking behaviour are discussed.

Einleitung: Das Persönlichkeitsmerkmal Sensation Seeking (SS) zeichnet sich durch die Suche nach Spannung, Abwechslung und neuen Erlebnissen sowie der Vermeidung von Langeweile aus. In der Literatur wird diskutiert, dass sich unterschiedlich starke Ausprägungen darin auf einem individuellen optimalen Erregungsniveau begründen, das ständig angestrebt wird. Die körperliche Betätigung dient dabei als Möglichkeit, dieses Niveau zu erreichen. Ziel dieser Studie war die Untersuchung des Zusammenhangs zwischen SS und dem körperlichen Aktivitätslevel, welches mit einem Aktometer gemessen wurde. Methoden: Es wurden 51 körperlich und psychisch gesunde Probanden im Alter von 18 bis 59 Jahren untersucht. Zur Erfassung des Traits SS wurde das Arnett Inventory of Sensation Seeking (AISS) eingesetzt, welches keinerlei sport- bzw. aktivitätsspezifische Items beinhaltet und in die Subskalen Intensität und Neuigkeit unterteilt ist. Als objektives Maß der körperlichen Aktivität wurde der gesamte und aktive Energieumsatz benutzt, der anhand des Aktometers SenseWear PRO2 der Firma BodyMedia gemessen wurde und in Kalorien angegeben wird. Zur Berechnung des Zusammenhangs zwischen SS und körperlicher Aktivität wurden sowohl bivariate als auch partielle Korrelationen verwendet, wobei bei letzterem der BMI als Kontrollvariable diente. Zur Berechnung der AISS-Scores kamen für Alter und Geschlecht normierte T-Werte zum Einsatz. Ergebnisse: Signifikante Werte fanden sich bei beiden Korrelationsanalysen zwischen dem gesamten Energieumsatz und der Gesamtskala des AISS (partiell: r = 0,279; p < 0,05) sowie der Subskala Intensität (partiell: r = 0,363; p < 0,009). Der aktive Energieumsatz zeigte keinen signifikanten Zusammenhang zu SS. Diskussion: Die Ergebnisse stimmen mit den Aussagen vorangegangener Studien überein, die bereits Zusammenhänge zwischen SS und sportlicher Aktivität berichteten. SS scheint also nicht nur mit riskanten Sportarten assoziiert zu sein, sondern vielmehr mit einem generell erhöhten Aktivitätsniveau. Dieser Zusammenhang zeigt sich in der vorliegenden Studie vor allem im niedrigeren Aktivitätsbereich und deutet daher auf eine erhöhte Grundaktivität hin. Es konnte weiterhin gezeigt werden, dass der Zusammenhang nicht auf die Verwendung sport- bzw. aktivitätsspezifischer Items in den Fragebögen zurückzuführen ist. Kritisch anzumerken sei der geringe Stichprobenumfang der Studie von N = 51. Der Vorteil dieser Studie ist die in der SS-Forschung erstmalige Verwendung eines Aktometers zur Erhebung objektiver Aktivitätswerte.

The primary aim of this thesis was to investigate, using functional magnetic resonance imaging (fMRI), the neurophysiological basis of multisensory integration involving smell and vision. To achieve this goal, several technical challenges had to be addressed: the attainment of sufficiently high quality fMRI images in olfactory brain regions within the orbitofrontal cortex (OFC), the construction of a stimulus delivery system adequate for rapid and controlled odour delivery in the MRI environment, and optimal strategies for delivering and perceiving liquid flavour stimuli in the scanner. In two initial fMRI experiments, strategies including sensitivity encoding and passive shimming to improve OFC image quality were explored. The results demonstrated that both methods can improve signal detection in OFC, a brain area particularly sensitive to susceptibility artefacts. In a further fMRI study, the effectiveness of two methods of delivering odorants dissolved in liquids was compared. In this study, the same set of participants was required to either swallow the liquid immediately after delivery or hold it in their mouths for a brief period of time. The results indicated that while both methods allowed detection of activity in primary olfactory and gustatory cortices, activation of the OFC was not observed when participants swallowed the liquids immediately. This was presumed to be due to the increased head motion associated with swallowing. Finally, the mechanisms underlying visual-olfactory integration were investigated using a combination of behavioural and imaging methods. An initial behavioural study revealed strong colour-odour associations for certain smells associated with fruits (e.g. lemon - yellow). In a subsequent fMRI study, volunteers were presented with a selection of the most colour-associated odours from the prior behavioural study either in isolation or in the presence of congruent and incongruent colours. Analysis of the fMRI data revealed that a highly left lateralised network of brain areas comprising of the OFC and insular showed increasingly stronger responses to odour-colour combinations of higher congruency. In a follow-up fMRI study, this same network was also found to be responsible for integrating odours, not only with colours, but also with their corresponding visual images (objects). In sum, the series of fMRI studies undertaken in this thesis argue for a fundamental role of the OFC in the integration of olfactory-visual inputs in the human brain.

An increase in postural sway is one of the risk factors that have been linked to an increased incidence of falls in the older adult population. Researchers have shown that peripheral sensation is crucial in maintaining a static posture for adults of all ages. It has been reported that older adults have decreased tactile sensation of the plantar surface of their feet. and when the sensory feedback was increased older adults had improved postural control. It was hypothesized that facilitation of the sole of the foot with the use of a semirigid foot orthotic would result in improved postural stability in older adults. Twenty-seven volunteers (19 females, 8 males, mean age: 87 ± 5 yrs) were recruited as subjects from a retirement community. All subjects were supplied with the SmartStep™ Stabilization System. There were a total of 5 Test Days for each subject. The first 2 Test Days were performed while the subjects wore their own shoes, while the last 3 Test Days were performed while the subjects wore the SmartStep™. Test Days 1 and 2 were performed 48 hours apart. Test Day 3 occurred 2 to 4 weeks after Test 2. Test Days 4 and 5 occurred 4-weeks after the prior Test Day. During the 8-weeks between Test Days 3 and 5, subjects were asked to wear the SmartStep™ as their daily shoe. Clinical measures of balance, force plate measurements, sensation testing, and confidence and activity scales were collected on all subjects throughout the eight week test period. Statistical significance was found for 3 of the clinical measures. The Timed “Up & Go” improved from 17.25 to 15.47 sec. The Functional Reach and Lateral Reach Tests demonstrated a decline in scores during the eight weeks. There was only 1 statistically significant finding for the force plate measures. The center of pressure displacement in the anteriorposterior direction was increased from 4.6 to 5.3 cm. No significant differences where reported for any other dependent variable. The results did not indicate statistically that the in-shoe orthotic enhanced postural stability in this group of subjects. However, there were indications that there was a subset of the current population that benefited from the intervention and this needs to be investigated further.

No description available.

The development of fatigue has been an area of interest to athletes and scientists alike for many years. Often, particularly during prolonged exercise in the heat, there is no obvious peripheral reason for fatigue and the central nervous system is cited as the source. The mechanisms and potential manipulations of this fatigue remain largely unclear. Chapters Three and Four attempted to reduce the transport of the serotonin precursor tryptophan into the brain in order to reduce or delay serotonin synthesis and therefore increase exercise capacity. In Chapter Three branched-chain amino acid drinks were fed before and during prolonged cycling to exhaustion in the heat on two occasions and control drinks were fed on two other occasions. There was no effect of the branched-chain amino acids on exercise capacity and the intra-individual variability in seven of the eight participants was small. One participant did appear to cycle for longer on the branched-chain amino acid trials compared to the control trials. In Chapter Four a 104 g bolus of amino acids, designed to deplete plasma tryptophan concentration, was fed seven hours before a prolonged cycle to exhaustion in the heat. There was no difference in exercise capacity between the tryptophan depletion trial and the control trial in which tryptophan was also ingested. These findings suggest that the delivery of tryptophan to the central nervous system is not the only factor influencing the onset of fatigue. The investigation undertaken in Chapter Five looked at the serotonin transporter density on the blood platelets of current and retired international level athletes competing in either endurance or sprint running events and a sedentary control group. Using the platelet as an accessible and reliable model for the serotonergic neuron, the maximum number of binding sites was assessed using the radio-labelled serotonin reuptake inhibitor [3H]Paroxetine. Those currently training for endurance events had a greater number of binding sites than any of the other groups. This supports previous findings and suggests that endurance training can increase the number of serotonin transporters on blood platelet membranes. During resting heat exposure in Chapter Six, the application of a 1 % menthol solution to the skin of the forearms, back and forehead elicited a warming sensation in some individuals and a cooling sensation in other individuals, but never any change in skin or core temperature nor skin blood flow. A small proportion of individuals did not perceive any change in skin thermal sensation. Chapter Seven applied these findings to a pre-loaded twenty minute exercise performance test in the heat. It was hypothesised that those who perceived a warming effect may perform worse when a menthol solution was applied compared to a control solution and conversely, those who perceived a cooling sensation may perform better with a menthol solution than with a control solution. There was no difference in exercise performance between those who felt a warming sensation and those who felt a cooling sensation. Those who felt a warming sensation felt significantly warmer on the menthol trial than the control trial but this did not affect their performance. However, those who reported a cooling sensation tended to feel cooler on the menthol trial than the control trial, and there was a tendency for an improvement in performance on the menthol trial compared to the control trial. Due to the experimental protocols adopted in this thesis it was possible to assess the reliability of an exercise capacity test compared to an exercise performance test. Chapter Three showed a coefficient of variation of 11.0 ± 11.2 % and Chapter Four showed a 11.5 ± 12.4 % variability for exercise capacity tests. Chapter Seven showed a coefficient of variation in a pre-loaded time-trial exercise performance test of 3.9 ± 9.6 % suggesting that an exercise performance test may be more reliable than an exercise capacity test. However, the aims of an investigation are still likely to be the main factor influencing the choice of protocol. It seems likely that no single mechanism will be responsible for the cessation of exercise. The investigations undertaken in this thesis also highlight many avenues for future exploration.

This thesis proposes a test method for evaluating the perceived vibration which occurs at the driver's hand in automotive steering wheel interface. The objective of the research was to develop frequency weightings for quantifying the human perception of steering wheel hand-arm vibration. Family of frequency weightings were developed from equal sensation curves obtained from the psychophysical laboratory experimental tests. The previous literature suggests that the only internationally standardised frequency weighting Wh is not accurate to predict human perception of steering wheel hand-arm vibration (Amman et. al, 2005) because Wh was developed originally for health effects, not for the human perception. In addition, most of the data in hand-arm vibration are based upon responses from male subjects (Neely and Burström, 2006) and previous studies based only on sinusoidal stimuli. Further, it has been continuously suggested by researchers (Gnanasekarna et al., 2006; Morioka and Griffin, 2006; Ajovalasit and Giacomin, 2009) that only one weighting is not optimal to estimate the human perception at all vibrational magnitudes. In order to address these problems, the investigation of the effect of gender, body mass and the signal type on the equal sensation curves has been performed by means of psychophysical laboratory experimental tests. The test participants were seated on a steering wheel simulator which consists of a rigid frame, a rigid steering wheel, an automobile seat, an electrodynamic shaker unit, a power amplifier and a signal generator. The category-ratio Borg CR10 scale procedure was used to quantify the perceived vibration intensity. A same test protocol was used for each test and for each test subject. The first experiment was conducted to investigate the effect of gender using sinusoidal vibration with 40 test participants (20 males and 20 females). The results suggested that the male participants provided generally lower subjective ratings than the female participants. The second experiment was conducted using band-limited random vibration to investigate the effect of signal type between sinusoidal and band-limited random vibration with 30 test participants (15 males and 15 females). The results suggested that the equal sensation curves obtained using random vibration were generally steeper and deeper in the shape of the curves than those obtained using sinusoidal vibration. These differences may be due to the characteristics of random vibration which produce generally higher crest factors than sinusoidal vibration. The third experiment was conducted to investigate the effect of physical body mass with 40 test participants (20 light and 20 heavy participants) using sinusoidal vibration. The results suggested that the light participants produced generally higher subjective ratings than the heavy participants. From the results it can be suggested that the equal sensation curves for steering wheel rotational vibration differ mainly due to differences of body size rather than differences of gender. The final experiments was conducted using real road signals to quantify the human subjective response to representative driving condition and to use the results to define the selection method for choosing the adequate frequency weightings for the road signals by means of correlation analysis. The final experiment was performed with 40 test participants (20 light and 20 heavy participants) using 21 real road signals obtained from the road tests. From the results the hypothesis was established that different amplitude groups may require different frequency weightings. Three amplitude groups were defined and the frequency weightings were selected for each amplitude group. The following findings can be drawn from the research: • the equal sensation curves suggest a nonlinear dependency on both the frequency and the amplitude. • the subjective responses obtained from band-limited random stimuli were steeper and the deeper in the shape of the equal sensation curves than those obtained using sinusoidal vibration stimuli. • females provided higher perceived intensity values than the males for the same physical stimulus at most frequencies. • light test participants provided higher perceived intensity than the heavy test participants for the same physical stimulus at most frequencies. • the equal sensation curves for steering wheel rotational vibration differ mainly due to differences in body size, rather than differences of gender. • at least three frequency weightings may be necessary to estimate the subjective intensity for road surface stimuli.

Following stroke, a patient may fail to report touch administered by another person but claim that s/he feels touch when it is self-administered. In Part One, the self-touch rubber hand paradigm was used to investigate different explanations for this phenomenon, termed self-touch enhancement. The most important finding was that patients reported touch based on feeling rather than by using proprioceptive information. Some patients have residual sensation that could be targeted in sensory rehabilitation. Part Two is a systematic investigation of the illusion of self-touch conducted with neurologically healthy participants. Participants used the right hand to administer touch to a prosthetic hand while the left (receptive) hand, positioned 15 cm from the prosthetic hand, received Examiner-administered touch. Proprioceptively perceived position of the administering and receptive hand was measured. Most participants experienced the single event of self-touch at the location of the receptive hand. Previous investigations have relied on measurement of only one hand and have concluded that participants experience self-touch at the location of the prosthetic hand. Our findings have implications for the role of ownership in this illusion. There is also a series of experiments in Part Two which test four potential constraints on the illusion of self-touch – violated expectations about the object that is administering touch, increased distance between the hands, alignment mismatch, and anatomical implausibility. For example, one study uses a novel paradigm to demonstrate that, although the subjective intensity of the illusion of self-touch is diminished by anatomical implausibility, most participants report the impossible experience of touching their left elbow with their own left index finger. Taken together, these experiments highlight the malleability of body representation, and provide a comprehensive framework for understanding the illusion of self-touch.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Title: Sensation seeking tendency in freeskiing Objectives: The aim of this work is sensation seeking tendency in freeskiing. Methods: Were chosen due to parameters of examined group of freeskiers and required outputs. For sensation seeking tendency in freeskiing were chosen Sensation Seeking Scale form V. Results: The comparison of our group of freeskiers with population average was detected significant differences. Statistically significant differences were detected in all 4 subscales. In sensation seeking scale are freeskiers significant different compare to population average in total score of SSS. This was caused primarily due to score of subscale TAS- thrill and Adventure seeking. Keywords: Freeskiing, personality, experiencing, flow, sensation seeking scale