The antisaccade task as a research tool in psychopathology: A critical review

The antisaccade task is a measure of volitional control of behavior sensitive to fronto-striatal dysfunction. Here we outline important issues concerning antisaccade methodology, consider recent evidence of the cognitive processes and neural mechanisms involved in task performance, and review how the task has been applied to study psychopathology. We conclude that the task yields reliable and sensitive measures of the processes involved in resolving the conflict between volitional and reflexive behavioral responses, a key cognitive deficit relevant to a number of neuropsychiatric conditions. Additionally, antisaccade deficits may reflect genetic liability for schizophrenia. Finally, the ease and accuracy with which the task can be administered, combined with its sensitivity to fronto-striatal dysfunction and the availability of suitable control conditions, may make it a useful benchmark tool for studies of potential cognitive enhancers

Structural neural networks subserving oculomotor function in first-episode schizophrenia

BACKGROUND: Smooth pursuit and antisaccade abnormalities are well documented in schizophrenia, but their neuropathological correlates remain unclear. METHODS: In this study, we used statistical parametric mapping to investigate the relationship between oculomotor abnormalities and brain structure in a sample of first-episode schizophrenia patients (n = 27). In addition to conventional volumetric magnetic resonance imaging, we also used magnetization transfer ratio, a technique that allows more precise tissue characterization. RESULTS: We found that smooth pursuit abnormalities were associated with reduced magnetization transfer ratio in several regions, predominantly in the right prefrontal cortex. Antisaccade errors correlated with gray matter volume in the right medial superior frontal cortex as measured by conventional magnetic resonance imaging but not with magnetization transfer ratio. CONCLUSIONS: These preliminary results demonstrate that specific structural abnormalities are associated with abnormal eye movements in schizophrenia

Cerebellar Control of Saccades in Health and Disease

Vision is one of the senses that are used for gathering information about the surrounding environment. Patterns of light reflecting from the environment enter the eye and are projected onto the retina. The retina harbors photoreceptors, which transform the patterns of light into the electrical activity that neurons use to convey visual information. This information enables humans to observe and interact with the environment. To gather detailed visual information about the properties of an object of interest, it must be projected on the fovea. The fovea is the part of the retina that has the highest density of photoreceptors and therefore provides the highest visual acuity. The projection of (moving) objects can be kept on the fovea using smooth pursuit eye movements, and new objects can be targeted by using saccadic eye movements. Eye movements can be recorded and quantified with relative ease. Current technology enables us not only to record eye movements in healthy adults in a laboratory setting, but also in more challenging subjects such as children or patients, or to record concurrently with functional imaging in a MR-scanner. Eye movements can be studied at multiple levels, ranging from the quantification of reflexive behavior to the inference of cognitive strategies involved in voluntary eye movement control. With properly designed studies it is possible to assign a functional role to the different stages in the visuo-oculomotor pathways. These characteristics propelled a large number of electrophysiological and behavioral studies on eye movements in non-human primates and humans. Functional imaging studies during the last twenty years have opened new ways for further investigations of the oculomotor system. The accumulating knowledge from these electrophysiological, behavioral and the more recent imaging studies has led to a detailed, but not complete, understanding of the neuronal pathways that subserve the oculomotor system. This also led to the appreciation that eye movements exhibit specific abnormalities when a confined part of the nervous system that is involved in these eye movements is affected by disease or trauma. Therefore, eye movement abnormalities have a clear clinical value and can contribute to the diagnostic process in a clinical setting. This thesis focuses on the neuronal pathways and clinical use of saccadic and smooth pursuit eye movements

Children and older adults exhibit distinct sub-optimal cost-benefit functions when preparing to move their eyes and hands

"© 2015 Gonzalez et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited"Numerous activities require an individual to respond quickly to the correct stimulus. The provision of advance information allows response priming but heightened responses can cause errors (responding too early or reacting to the wrong stimulus). Thus, a balance is required between the online cognitive mechanisms (inhibitory and anticipatory) used to prepare and execute a motor response at the appropriate time. We investigated the use of advance information in 71 participants across four different age groups: (i) children, (ii) young adults, (iii) middle-aged adults, and (iv) older adults. We implemented 'cued' and 'non-cued' conditions to assess age-related changes in saccadic and touch responses to targets in three movement conditions: (a) Eyes only; (b) Hands only; (c) Eyes and Hand. Children made less saccade errors compared to young adults, but they also exhibited longer response times in cued versus non-cued conditions. In contrast, older adults showed faster responses in cued conditions but exhibited more errors. The results indicate that young adults (18 -25 years) achieve an optimal balance between anticipation and execution. In contrast, children show benefits (few errors) and costs (slow responses) of good inhibition when preparing a motor response based on advance information; whilst older adults show the benefits and costs associated with a prospective response strategy (i.e., good anticipation)

Gaze Behavior, Believability, Likability and the iCat

The iCat is a user-interface robot with the ability to express a range of emotions through its facial features. This paper summarizes our research whether we can increase the believability and likability of the iCat for its human partners through the application of gaze behaviour. Gaze behaviour serves several functions during social interaction such as mediating conversation flow, communicating emotional information and avoiding distraction by restricting visual input. There are several types of eye and head movements that are necessary for realizing these functions. We designed and evaluated a gaze behaviour system for the iCat robot that implements realistic models of the major types of eye and head movements found in living beings: vergence, vestibulo ocular reflexive, smooth pursuit movements and gaze shifts. We discuss how these models are integrated into the software environment of the iCat and can be used to create complex interaction scenarios. We report about some user tests and draw conclusions for future evaluation scenarios

Localization of external stimuli during simulated self- and object-motion

This thesis comprises fife studies. In the first study we investigated the localization of brief visual targets during reflexive eye movements (optokinetic nystagmus). Localization during OKN, corrected for the bias observed during fixation, was shifted in the direction of the slow eye movement. This bias decreased shortly before a fast-phase and temporarily increased afterwards. Control experiments showed that localization errors were mainly due to the performance of eye movements rather than due to the background motion. Hence, our data show for the first time an influence of reflexive eye movements on the localization of briefly presented visual targets. In the second study, we determined mislocalization of flashed visual targets during optokinetic afternystagmus (OKAN). These eye movements are quite unique in that they occur in complete darkness, and are generated by subcortical control mechanisms. We found that during OKAN slow-phases subjects mislocalize targets away from the fovea. This corresponds to a perceived expansion of visual. Around the OKAN fast-phases, we found a bias in the direction of the fast-phase prior to its onset and opposite to the fast-phase direction thereafter. Such a biphasic modulation has also been reported in the temporal vicinity of saccades, and during optokinetic nystagmus (OKN). A direct comparison, however, showed that the modulation during OKAN was much larger and occurred earlier relative to fast-phase onset than during OKN. In the third study we analyzed the fast-phases of OKAN and OKN as well as visually guided and spontaneous saccades under identical background conditions. Our data clearly show that fast-phases of OKAN and OKN differ with respect to their main sequence. OKAN fast-phases were characterized by their lower peak-velocities and longer durations as compared to OKN fast-phases. Furthermore we found that the main sequence of spontaneous saccades depends heavily on background characteristics, with saccades in darkness being slower and lasting longer. On the contrary, the main sequence of visually guided saccades depended on background characteristics only very slightly. This implies that the existence of a visual saccade target largely cancels out the effect of background luminance. Our data underline the critical role of environmental conditions (light vs. darkness), behavioral tasks (e.g. spontaneous vs. visually guided) and the underlying neural networks for the exact spatio-temporal characteristics of fast eye movements. It is widely debated whether fast-phases of the reflexive optokinetic nystagmus (OKN) share properties with another class of fast eye movements, visually guided saccades. Conclusions drawn from previous studies were complicated by the fact that a subject’s task influences the exact type of OKN: stare- vs. look nystagmus. Therefore in the fourth study we set out to determine in the same subjects the exact dynamic properties (main sequence) of fast-phases of look- and stare-nystagmus as well as visually guided saccades. Our data clearly show that fast-phases of look- and stare-nystagmus differ with respect to their main sequence. Fast-phases of stare-nystagmus were characterized by their lower peak-velocities and longer durations as compared to fast-phases of look-nystagmus. Visually guided saccades were on the same main-sequence as fast-phases of look-nystagmus, while they had higher peak-velocities and shorter durations than fast-phases of stare-nystagmus. Our data underline the critical role of behavioral tasks (e.g. reflexive vs. intentional) for the exact spatio-temporal characteristics of fast eye movements. Primates perform saccades to stationary and moving targets. Yet, saccades towards moving targets are computationally more demanding since the oculomotor system must use speed and direction information to program an adequate saccade. In non-human primates different brain regions have been implicated in the control of voluntary saccades. One of these regions is the lateral intraparietal area (LIP). It is not known whether LIP neurons show differential activation related to the control of saccades towards stationary as compared to moving targets. To this end in the fifth study we recorded single unit activity in area LIP of two monkeys (Macaca mulatta). Monkeys performed visually guided saccades to either stationary targets or moving targets in pseudo-randomized order. Stationary saccade targets were located such that the amplitudes of saccades towards moving and stationary targets were identical. Confirming previous results, many LIP neurons showed saccade related discharges that were tuned for amplitude and direction. Yet, given identical saccade metrics, discharge varied depending on whether saccades were followed by stable fixation or smooth pursuit in about one third of these neurons. We conclude that area LIP is involved in the control of saccades towards stationary and moving targets