Mental workload is commonly defined as the proportion of a person's total mental capacity in use at a given moment. A measure of mental workload would have utility in a number of rehabilitation medicine applications, but no method has been adequately examined for these purposes. A candidate measure is the intersaccadic interval (ISI), which is the duration between two successive saccades. Previous studies indicate that ISI length may be linked to mental workload, but this link is poorly understood for tasks that are not primarily visual. Therefore, the current study was an investigation of ISI and workload intensity in three non-visual tasks: mental arithmetic, verbal fluency, and audio perception. Workload was manipulated through changes in task difficulty as well as study participant motivation level. An analysis of eye movements and other experimental workload measures indicated a significant association between audio perceptual workload and ISI length.

Magistro baigiamajame darbe nagrinėjama Miulerio-Lajerio geometrinės iliuzijos įtaka sakadiniams bei sekamiesiems akių judesiams. Siekta nustatyti žmogaus akių judesių vaidmenį regos sistemai. Akių judesiai priklauso nuo iliuzijos nuo 0,1 % iki 10 %. Rezultatai rodo, kad sąmoningai atliktos sakados yra 40 % - 50 % labiau įtakojamos iliuzijos, lyginant su refleksinėmis sakadomis. Akies sekamieji judesiai, sekant taikinį, turintį iliuzijos efektą, gali būti naudojami objektyviam dinaminės (judančios ir dėl to stebimos trumpą laiko tarpą) iliuzijos, poveikio ir laipsnio nustatymui. Darbą sudaro įvadas, trys skyriai, išvados ir literatūros sąrašas. Išnagrinėti 45 literatūros šaltiniai. Darbo apimtis 52 puslapiai, įskaitant 3 lenteles ir 29 paveikslus. / There is dealing influence of Muller – Layer geometrical illusion to saccadic and followed eyes movements in final Master’s work. It is sought to set the role of human eyes’ movements to visual system. Movements of eyes depend on illusion from 0,1 % to 10 %. Results show consciously made saccades are 40 % - 50 % more influenced illusions compared with reflexives saccades. Followed eyes movements when they follow the target which has effect of illusion might be using to set objective dynamic (moving and therefore observed short time) illusion, influence and degree. The final work contains introduction, three chapters, conclusions and literature‘s list. There are explored 45 sources of literature. Workload is 52 pages including 3 tables and 29 pictures.

Behavioural choices of animals as they acquire resources in the wild are well characterized by foraging theory; however, the neural mechanisms underlying these behaviours are not well understood. The goal of this thesis is to understand the brain mechanisms involved in selecting and executing such foraging behaviours. To do so, rhesus monkeys performed a novel visuosaccadic foraging task while we recorded the activity of single neurons in the intermediate layers of the superior colliculus (SCi). An important innovation of this task is that both target profitability – the measure of value in the simplest case of foraging theory – and saccade choice are measured separately. We hypothesized that target profitability is represented in the SCi in addition to its well characterized role in saccade planning and preparation. Visual Foraging Task: Monkeys harvested coloured dots representing prey items by fixating them for a pre-specified handling time. On each trial, multiple prey are presented, sharing identical physical attributes except that each was one of three colours. All prey of the same colour shared the same profitability [Profitability = reward magnitude (ml)/handling time (s)]. According to foraging theory, intake of reward is maximized if prey are selected in descending order of their profitability. Indeed, we found subjects gradually approached optimal efficiency. We computed an index of the relative subjective profitability of each prey colour, which compared the rank order with which monkeys chose prey of each colour. This subjective index of profitability was then compared to concomitant SC activity attributed to the prey item in the neuron’s response field (RF). First, we found that the amount of SC activity reflected the subjective profitability of the RF targets, and established that this effect was not simply a result of saccade goal planning. Second, profitability information remains dominant throughout the handling period until reward delivery, after which activity also became selective for upcoming saccades. Together, our results highlight the prominent role of target profitability in shaping SCi activity. We propose that profitability information in the SCi may play an important role in resolving competition between numerous target representations to choose the next saccade goal. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-02-21 15:37:43.468

Background: Prenatal alcohol exposure causes behavioural, growth and central nervous system deficits in the offspring, termed Fetal Alcohol Spectrum Disorder (FASD). Our lab has previously shown that structured saccadic eye movement tasks probe executive functioning and can be used to measure cognitive dysfunction in children with an FASD, because performance of these tasks reflects the structural integrity of brain areas shown to be vulnerable to prenatal alcohol exposure. Recently developed portable electroencephalographic (EEG) devices record brain activity using a single dry-sensor electrode. Our objectives were: 1) to assess attention and working memory via a delayed memory-guided saccadic eye movement task of varying mnemonic load and 2) to explore the use of a portable single-channel EEG recording device in measuring differences in frontal lobe activity in children with FASD during the performance of this eye movement task. Methods: A total of 18 children with an FASD diagnosis and 19 typically developing control children performed a memory-guided saccadic eye movement task with one, two or three target stimuli. During the task, frontal lobe EEG was recorded using the Neurosky Mindwave Mobile® portable recording device. Results: In the delayed, memory-guided task when two or three target stimuli were required to be held in working memory, children with an FASD performed the task correctly less often than children in the control group. During task performance, children with FASD exhibited a reduction in theta frequency band power, and in alpha frequency band power only at higher mnemonic loads, suggesting that children with FASD recruited more cognitive resources to complete the task. Conclusion: The results of this study suggest that a portable EEG recording device can be used to assist in the recognition of underlying neural mechanisms of executive functioning deficits in children with FASD. Portable devices offer greater user comfort than typical EEG recording equipment as well as flexibility for use outside the laboratory. This could greatly facilitate the study of children with FASD, and other groups who may be less tolerant of typical laboratory environments. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-08-14 20:22:10.995

Background: The progesterone metabolite allopregnanolone is involved in several clinical conditions in women, e.g. premenstrual dysphoric disorder. It is a very potent GABA-steroid with GABA-A receptor effects similar to other GABA-agonists, e.g. benzodiazepines, and it causes sedation. An objective way to examine effects on the GABA-A receptor in humans is to measure saccadic eye velocity (SEV), which is reduced by GABA-agonists, e.g. allopregnanolone. Animal studies suggest that allopregnanolone is involved in the regulation of gonadotropin secretion via the GABA-A receptor, but this has not been studied in humans. Polycystic ovary syndrome (PCOS) is the most common endocrine disturbance among women of fertile age (5–10%), characterized by polycystic ovaries, menstrual dysfunction, hyperandrogenity, and 50% have obesity. Studies have shown higher allopregnanolone levels in overweight people. PCOS women have increased levels of androstanediol, an androgen metabolite which is an GABA-A receptor agonist. Tolerance often occurs when persons are exposed to high levels of GABAergic modulators. It has not been studied whether GABA-A receptor sensitivity in PCOS women is changed. Another progesterone metabolite, isoallopregnanolone, is the stereoisomere of allopregnanolone but has not been shown to have any GABA-A receptor effect of its own. Instead it has often been used to control steroid specificity to allopregnanolone. Aims: To compare the effects of allopregnanolone and isoallopregnanolone on gonadotropin secretion. To compare allopregnanolone levels, GABA-A receptor sensitivity to allopregnanolone and effects on gonadotropin secretion in both cycle phases and PCOS conditions. To examine pharmacokinetics and pharmacodynamic properties for isoallopregnanolone. Method: In the follicular phase healthy women were examined for the effect of allopregnanolone or isoallopregnanolone on gonadotropin secretion. PCOS women and healthy women in both cycle phases were given allopregnanolone and the differences in effects on SEV were examined, as well as changes in serum levels of gonadotropins and allopregnanolone at baseline and during the test day. Pharmacokinetics and GABA-A receptor sensitivity using SEV were explored for isoallopregnanolone in healthy women. Results: Allopregnanolone decreases gonadotropin serum levels in healthy controls in both cycle phases, but has no effect on gonadotropin secretion in women with PCOS. PCOS women have higher baseline serum levels of allopregnanolone than follicular phase controls, but lower levels than luteal phase controls. PCOS women show greater reduction in SEV to allopregnanolone than controls. Isoallopregnanolone has no effect on gonadotropin secretion. There is an effect of isoallopregnanolone on SEV, explained by a metabolism of isoallopregnanolone into allopregnanolone. Conclusion: There are significant differences in the GABA-A receptor response to a GABA-steroid in different endocrine conditions in women of fertile age examined with saccadic eye velocity. The GABA-steroid allopregnanolone decreases gonadotropin serum levels in healthy women but not in PCOS women. The lack of effect on gonadotropins by isoallopregnanolone suggests an involvement of the GABA-A receptor.

xiv, 152 p. Adviser: Terry Takahashi (Biology Dept.). Chapter 2 of this dissertation has been previously published in the Journal of Neurophysiology. Citation: Whitchurch EA and Takahashi TT. Combined auditory and visual stimuli facilitate head saccades in the barn owl (Tyto alba). J Neurophysiol 96: 730-745, 2006. / A print copy of this title is available through the UO Libraries under the call number: SCIENCE QL696.S85 W54 2006 / Survival depends on our ability to detect and integrate sensory information from multiple modalities, allowing for the most efficient behavioral response. For example, barn owls must combine sights and sounds from the environment to localize potential prey. A vole scurrying through a drift of dried leaves is more likely to meet its doom if a nearby owl can both faintly see and hear it. How does the brain take two physically discreet inputs and combine them into a unified representation of the surrounding multisensory world? Moreover, how is this internal representation transformed into the most efficient behavioral response? This dissertation comprises original research addressing these questions in the barn owl with two distinct approaches: First, Chapters II and III describe orientation behavior in response to auditory, visual, and audiovisual stimuli. Chapter II probes the effect of stimulus strength on saccadic behavior and the nature of audiovisual integration, and was taken from a co-authored publication. Chapter III explores the behavioral consequence of an induced stimulus asynchrony in audiovisual integration and was taken from a co-authored manuscript being prepared for publication. The second experimental approach is described in Chapters IV and V. These chapters probe the physiological basis of saccadic behavior by measuring single-neuron responses to auditory, visual, and audiovisual stimuli. Chapter IV describes how auditory responses of neurons from the external nucleus of the inferior colliculus depend on sound pressure level. Chapter V describes activity of optic tectum neurons in response to auditory, visual, and audiovisual stimuli. The behavioral findings described herein suggest that barn owls often incorporate both the speed of the auditory system and the accuracy of the visual system when localizing a multisensory stimulus, even when the two modalities are presented asynchronously. The physiological studies outlined in this dissertation show that sensory representations in the midbrain can be used to predict general trends in saccadic behavior: Neuronal thresholds were within the range of observed behavioral thresholds. Responses to multisensory stimuli were enhanced relative to unisensory stimuli, possibly corresponding to enhanced multisensory behavior. These data support fundamental rules in multisensory integration that may apply across species.

No description available.

Afin de poursuivre une cible en mouvement, le système nerveux central (SNC) utilise deux types de mouvements oculaires: la poursuite et les saccades. Les saccades sont des mouvements rapides et brefs de redirection de l’axe visuel d’un centre d’intérêt à un autre. La poursuite est un mouvement lent qui tend à maintenir la cible d’intérêt sur la fovéa. La vitesse de l’œil étant toujours inférieure à celle de la cible, une erreur positionnelle entre l’œil et la cible va croître en l’absence de mouvement correctif. Des saccades de rattrapage sont déclenchées par le SNC pour corriger cette erreur. Alors qu’il est largement reconnu que le système de la poursuite utilise un modèle interne du mouvement de la cible pour améliorer ses capacités, la modalité de contrôle de l’amplitude des saccades de rattrapage est sujette à controverse quant au rôle direct d’afférences sensorielles ou d’un modèle interne de la cible en mouvement. Nous avons développé un nouveau paradigme de transition de poursuite oculaire appliqué à l’Homme sain, dans lequel la cible change de manière imprévisible d’un profil de vitesse non constant périodique à un profil de vitesse non constant apériodique. Nos résultats confirment que le SNC utilise un modèle interne de la cible en mouvement pour contrôler l’amplitude des saccades de rattrapage. Ce modèle se construit progressivement à partir de 168 millisecondes après le changement de profil de vitesse et est utilisé conjointement par les systèmes de la poursuite et saccadique. Le substrat neuronal potentiel de ce modèle interne sera discuté à la lumière des connaissances issues de la littérature concernant le contrôle moteur et oculomoteur. / Two types of eye movements are combined while tracking a moving object: smooth pursuit and saccades. Saccades are rapid redirections of the visual axis between two centers of interest. Because pursuit gain is smaller than one, the eye would increasingly lag behind the target without any correcting movements. Thus, “catch-up saccades” are triggered by the central nervous system (CNS) to cancel this growing position error between the eye and the target. It is widely accepted that an internal model of target motion is used by the CNS to cancel inherent delays between visual input and smooth pursuit motor output, ensuring accurate tracking of moving targets. The amplitude of catch-up saccades triggered during smooth pursuit could be corrected by a delayed sensory signal to account for the ongoing target displacement during catch-up saccades. Yet, recent studies suggested that the correction of catch-up saccade amplitude must also be done through an internal model of target motion. We developed a new paradigm in which the target switches unexpectedly from one target with a non-constant periodic velocity profile to another with a non-constant aperiodic velocity profile. Our results in healthy humans confirm that the CNS uses an internal model of target motion to correct catch-up saccade amplitude. Internal model is being built gradually from 168 ms after the target switch. We show that a common internal model of target motion is shared within the CNS to control smooth pursuit and to correct catch-up saccade amplitude. The potential neuronal substrate of such an internal model will be discussed in the light of the knowledge from the literature on motor and oculomotor control.

Les modèles de décision conventionnels, basés sur l’utilisation du système saccadique comme modèle sensorimoteur, considèrent typiquement les temps de réaction comme un sous-produit des processus décisionnels, reflétant le temps nécessaire pour prendre une décision. Cependant, des recherches ont montré que les latences saccadiques sont deux fois plus longues que le temps de décision, ainsi que l’organisation de l’environnement affecte les latences saccadiques. Cette thèse propose une interprétation alternative des temps de réaction saccadiques (SRTs) en montrant que les distributions de latences saccadiques peuvent être altérées par leurs propres conséquences. Nous défendons l’hypothèse que les latences saccadiques dépendent de relations fonctionnelles avec leur environnement.Cette thèse a réalisé une analyse fonctionnelle des latences saccadiques. La première étude a évalué s’il était possible de choisir ses propres latences en fonction des contingences de renforcement en cours, dans le but d’explorer l’étendue du contrôle temporel des saccades. L’allocation des latences courtes et longues correspondait au renforcement relativement obtenu, démontrant un contrôle fin des SRTs. La seconde étude a évalué de manière plus approfondie l’effet de conséquences bénéfiques sur les SRTs, en utilisant le phénomène de taille-latence. La procédure de renforcement a été efficace pour manipuler le bénéfice de SRTs plus courts et pour réduire le phénomène de taille-latence. La troisième étude a démontré comment les stimuli antécédents en viennent à contrôler des temps de réaction spécifiques à l’aide d’un apprentissage opérant. Les contingences de renforcement ont induit un contrôle discriminatif des latences entre des stimuli différents. Enfin, la dernière expérience a exploré l’implication des processus d’apprentissage classique dans le contrôle par le stimulus des latences saccadiques. Cette étude pilote met en évidence l’influence de l’environnement et de l’historique d’apprentissage dans le contrôle temporel des saccades.Nos résultats soulignent l’incroyable plasticité du système saccadique, et l’étend au contrôle temporel des saccades. Cette thèse montre qu’un processus général d’apprentissage, basé sur les conséquences fonctionnelles des saccades, peut expliquer de manière parcimonieuse les changements dans les latences saccadiques. Démontrant que la latence est une dimension opérante des saccades, l’organisation de l’environnement contrôle l’organisation temporelle des saccades. / Conventional decision models, based on the saccadic system as a sensorimotor model, typically view reaction time as a byproduct of decisional processes, reflecting the time needed to make a decision. However, research has shown that saccadic latencies are twice as long as the decision time and that the organization of the environment affects saccade latencies. This thesis dissertation provides an alternative view of saccadic reaction times (SRTs) by showing that saccade latency distribution can be altered by their own consequences. We defend that saccadic latency depends on functional relations with its environment.This thesis conducted a functional analysis of saccadic latencies. The first study probed whether it is possible to choose one’s latencies depending on the reinforcement contingencies in force, in order to assess the extent of temporal control with saccades. The allocation of short and long latencies matched the relative reinforcement obtained, demonstrating a fine control of SRTs. The second study further investigated the effect of beneficial consequences on SRTs, using the size-latency phenomenon. The reinforcement procedure was effective in manipulating the benefit of shorter SRTs and reducing the size- latency phenomenon. The third experiment demonstrated how antecedent stimuli come to control specific reaction times through operant learning. Reinforcement contingencies induced discriminative control of latencies between different stimuli. Finally, the last experiment explored the involvement of classical learning processes in stimulus control of saccade latencies. This pilot study highlighted the influence of the environment and learning history in the temporal control of saccades.Our results emphasize the exquisite plasticity of the saccadic system, and extend it to the temporal control of saccades. This thesis shows that a general learning process, based on the functional consequences of saccades, can parsimoniously explain changes in saccadic latency. Demonstrating that latency is an operant dimension of saccades, the organization of the environment controls the temporal organization of saccades.

Part of the aim of this thesis was to explore a model for producing very fast saccade latencies in the 80 to 120ms range. Its primary motivation was to explore a possible interaction by uniquely combining three independent saccade factors: the gap effect, target-feature-discrimination, and saccadic inhibition of return (IOR). Its secondary motivation was to replicate (in a more conservative and tightly controlled design) the surprising findings of Trottier and Pratt (2005), who found that requiring a high resolution task at the saccade target location speeded saccades, apparently by disinhibition. Trottier and Pratt’s finding was so surprising it raised the question: Could the oculomotor braking effect of saccadic IOR to previously viewed locations be reduced or removed by requiring a high resolution task at the target location? Twenty naïve untrained undergraduate students participated in exchange for course credit. Multiple randomised temporal and spatial target parameters were introduced in order to increase probability of exogenous responses. The primary measured variable was saccade latency in milliseconds, with the expectation of higher probability of very fast saccades (i.e. 80-120ms). Previous research suggested that these very fast saccades could be elicited in special testing circumstances with naïve participants, such as during the gap task, or in highly trained observers in non-gap tasks (Fischer & Weber, 1993). Trottier and Pratt (2005) found that adding a task demand that required naïve untrained participants to obtain a feature of the target stimulus (and to then make a discriminatory decision) also produced a higher probability of very fast saccade latencies. They stated that these saccades were not the same as saccade latencies previously referred to as express saccades produced in the gap paradigm, and proposed that such very fast saccades were normal. Carpenter (2001) found that in trained participants the probability of finding very fast saccades during the gap task increased when the horizontal direction of the current saccade continued in the same direction as the previous saccade (as opposed to reversing direction) – giving a distinct bimodality in the distribution of latencies in five out of seven participants, and likened his findings to the well known IOR effect. The IOR effect has previously been found in both manual key-press RT and saccadic latency paradigms. Hunt and Kingstone (2003) stated that there were both cortical top-down and oculomotor hard-wired aspects to IOR. An experiment was designed that included obtain-target-feature and oculomotor-prior-direction, crossed with two gap level offsets (0ms & 200ms-gap). Target-feature discrimination accuracy was high (97%). Under-additive main effects were found for each factor, with a three-way interaction effect for gap by obtain-feature by oculomotor-prior-direction. Another new three-way interaction was also found for anticipatory saccade type. Anticipatory saccades became significantly more likely under obtain-target-feature for the continuing oculomotor direction. This appears to be a similar effect to the increased anticipatory direction-error rate in the antisaccade task. These findings add to the saccadic latency knowledge base and in agreement with both Carpenter and Trottier and Pratt, laboratory testing paradigms can affect saccadic latency distributions. That is, salient (meaningful) targets that follow more natural oculomotor trajectories produce higher probability of very fast latencies in the 80-120ms range. In agreement with Hunt and Kingstone, there appears to be an oculomotor component to IOR. Specifically, saccadic target-prior-location interacts differently for obtain-target-feature under 200-ms gap than under 0ms-gap, and is most likely due predominantly to a predictive disinhibitory oculomotor momentum effect, rather than being due to the attentional inhibitory effect proposed for key-press IOR. A new interpretation for the paradigm previously referred to as IOR is offered that includes a link to the smooth pursuit system. Additional studies are planned to explore saccadic interactions in more detail.