To date, invasive brain-computer interface (BCI) research has largely focused on replacing lost limb functions using signals from hand/arm areas of motor cortex. However, the oculomotor system may be better suited to BCI applications involving rapid serial selection from spatial targets, such as choosing from a set of possible words displayed on a computer screen in an augmentative and alternative communication application. First, we develop an intracortical oculomotor BCI based on the delayed saccade paradigm and demonstrate its feasibility to decode intended saccadic eye movement direction in primates. Using activity from three frontal cortical areas implicated in oculomotor production – dorsolateral prefrontal cortex, supplementary eye field, and frontal eye field – we could decode intended saccade direction in real time with high accuracy, particularly at contralateral locations. In a number of analyses in the decoding context, we investigated the amount of saccade-related information contained in different implant regions and in different neural measures. A novel neural measure using power in the 80-500 Hz band is proposed as the optimal signal for this BCI purpose. In the second part of this thesis, we characterize the interactions between the neural signals recorded from electrodes in these three implant areas. We employ a number of techniques to quantify the spectrotemporal dynamics in this complex network, and we describe the resulting functional connectivity patterns between the three implant regions in the context of eye-movement production. In addition, we compare and contrast the amount of saccade-related information present in the coupling strengths in the network, on both an electrode-to-electrode scale and an area-to-area scale. Different frequency bands stand out during different epochs of the task, and their information contents are distinct between implant regions. For example, the 13-30 Hz band stands out during the delay epoch, and the 8-12 Hz band is relevant during target and response epochs. This work extends the boundary of BCI research into the oculomotor domain, and invites potential applications by showing its feasibility. Furthermore, it elucidates the complex dynamics of the functional coupling underlying oculomotor production across multiple areas of frontal cortex.

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Master of Science in Medicine / Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.

Previous research on mind wandering has used subjective verbal reports as a means to acquire the frequency and rate of its occurrence. I proposed the use of eye movements as an objective measure of mind wandering while participants attempted a reading task. Participants were placed in a self-classified probe-caught mind wandering paradigm while their eye movements were recorded. They were randomly probed every 2-3 minutes and were required to indicate whether their mind had been wandering before they were allowed to continue reading. The overall pattern showed that eye movement behaviour was slower and less frequent when participants reported mind wandering episodes, with duration and frequency of within-word regressions reaching levels of statistical significance. It may be that the cognitive processes that normally guide eye movements during reading exert less control during mind wandering episodes. Other implications and limitations are discussed.

Previous research on mind wandering has used subjective verbal reports as a means to acquire the frequency and rate of its occurrence. I proposed the use of eye movements as an objective measure of mind wandering while participants attempted a reading task. Participants were placed in a self-classified probe-caught mind wandering paradigm while their eye movements were recorded. They were randomly probed every 2-3 minutes and were required to indicate whether their mind had been wandering before they were allowed to continue reading. The overall pattern showed that eye movement behaviour was slower and less frequent when participants reported mind wandering episodes, with duration and frequency of within-word regressions reaching levels of statistical significance. It may be that the cognitive processes that normally guide eye movements during reading exert less control during mind wandering episodes. Other implications and limitations are discussed.

The rapid-eye-movement (REM) sleep is one of the most important parts in overnight sleep. In this study, an automatic REM sleep staging rule is introduced. Compared with the traditional REM detection method, a distinct feature of this method is that it only requires two EOG signals and thus reduces the number of input signal channels significantly. We calculate the correlation coefficient series between two EOG signals. By representing such a series with a VQ coding method, several techniques are proposed to improve the classification rate. Experimental results are given to demonstrate the effectiveness of the proposed approach.

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.

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Although heritability estimates of schizophrenia are high, studies attempting to identify specific genes for schizophrenia have been only modestly successful. Strategies to improve the power of genetic studies include the creation of homogeneous subtypes of schizophrenia based on symptom presentation, and the identification of behavioural abnormalities that reflect the presence of genes for schizophrenia ("behavioural markers of risk") even in the absence of the full clinical disorder. Oculomotor abnormalities are one of the most well-documented markers of risk. It is not known whether abnormalities in motor control are specific to the oculomotor system or whether they are found as well in other domains such as skeletomotor control. It is also not known whether different types of schizophrenia-related symptoms, which presumably have distinct neural bases, are associated with different behavioural abnormalities. / This thesis investigates oculomotor and skeletomotor function in clinically unaffected individuals who are at elevated risk for schizophrenia based on their scores on either a positive-symptom schizotypy questionnaire (Perceptual Aberration Scale) (n = 21) or a negative-symptom schizotypy questionnaire (Physical Anhedonia) (n = 20), and in Controls (n = 29). / In Manuscript 1, we review the evidence suggesting that skeletomotor deficits are present in neuroleptic-naive schizophrenia patients and high-risk populations. The review supports the notion of skeletomotor dysfunction in these groups and underscores the lack of studies using instrumentation to characterize the deficits. In Manuscript 2, we compare the oculomotor performance of positive-symptom and negative-symptom schizotypes to that of controls. Results suggest that smooth pursuit deficits identify high-risk individuals with either positive or negative symptomatology, while antisaccade deficits identify primarily individuals with positive symptoms. In Manuscript 3, we use high-speed instrumentation and kinematic measures to evaluate skeletomotor function, and to assess the relationship between oculomotor and skeletomotor deficits in positive and negative-symptom schizotypes. This study revealed differential patterns of skeletomotor deficits in positive- and negative-symptom schizotypy, with both patterns suggestive of frontal-striatal dysfunction. In general, oculomotor and skeletomotor deficits were not associated. / Together these results support the notion of motor deficits across domains in risk for schizophrenia. In addition, they highlight the importance of distinguishing between positive and negative symptomatology when investigating the pathophysiology of risk for schizophrenia.

This thesis investigates sensorimotor adaptive mechanisms that maintain the accuracy of goal-directed saccades in amblyopia, a developmental disorder characterized by impairment of spatiotemporal visual processing. Saccadic adaptation was induced by displacing the visual target toward initial fixation during the saccade. Eleven visually normal controls and seven patients with amblyopia were tested binocularly and monocularly with the amblyopic and fellow eye (non-dominant and dominant eye in controls) in three separate sessions. Patients with amblyopia exhibited reduced adaptation of saccadic gain compared to controls when viewing with the amblyopic eye and binocularly. Initiation of saccades was also delayed in patients when viewing with the amblyopic eye. It is proposed that the adaptive ability to modify the initial saccadic motor commands for maintaining short-term saccadic accuracy is impaired in amblyopia due to imprecise error signals. Moreover, this thesis reaffirms the notion that the error signals driving saccadic adaptation are visual in nature.