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

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

Temporal Dynamics of Decision-Making during Motion Perception in the Visual Cortex

How does the brain make decisions? Speed and accuracy of perceptual decisions covary with certainty in the input, and correlate with the rate of evidence accumulation in parietal and frontal cortical "decision neurons." A biophysically realistic model of interactions within and between Retina/LGN and cortical areas V1, MT, MST, and LIP, gated by basal ganglia, simulates dynamic properties of decision-making in response to ambiguous visual motion stimuli used by Newsome, Shadlen, and colleagues in their neurophysiological experiments. The model clarifies how brain circuits that solve the aperture problem interact with a recurrent competitive network with self-normalizing choice properties to carry out probablistic decisions in real time. Some scientists claim that perception and decision-making can be described using Bayesian inference or related general statistical ideas, that estimate the optimal interpretation of the stimulus given priors and likelihoods. However, such concepts do not propose the neocortical mechanisms that enable perception, and make decisions. The present model explains behavioral and neurophysiological decision-making data without an appeal to Bayesian concepts and, unlike other existing models of these data, generates perceptual representations and choice dynamics in response to the experimental visual stimuli. Quantitative model simulations include the time course of LIP neuronal dynamics, as well as behavioral accuracy and reaction time properties, during both correct and error trials at different levels of input ambiguity in both fixed duration and reaction time tasks. Model MT/MST interactions compute the global direction of random dot motion stimuli, while model LIP computes the stochastic perceptual decision that leads to a saccadic eye movement.National Science Foundation (SBE-0354378, IIS-02-05271); Office of Naval Research (N00014-01-1-0624); National Institutes of Health (R01-DC-02852

A retinotopic attentional trace after saccadic eye movements: evidence from event-related potentials

Saccadic eye movements are a major source of disruption to visual stability, yet we experience little of this disruption. We can keep track of the same object across multiple saccades. It is generally assumed that visual stability is due to the process of remapping, in which retinotopically organized maps are updated to compensate for the retinal shifts caused by eye movements. Recent behavioral and ERP evidence suggests that visual attention is also remapped, but that it may still leave a residual retinotopic trace immediately after a saccade. The current study was designed to further examine electrophysiological evidence for such a retinotopic trace by recording ERPs elicited by stimuli that were presented immediately after a saccade (80 msec SOA). Participants were required to maintain attention at a specific location (and to memorize this location) while making a saccadic eye movement. Immediately after the saccade, a visual stimulus was briefly presented at either the attended location (the same spatiotopic location), a location that matched the attended location retinotopically (the same retinotopic location), or one of two control locations. ERP data revealed an enhanced P1 amplitude for the stimulus presented at the retinotopically matched location, but a significant attenuation for probes presented at the original attended location. These results are consistent with the hypothesis that visuospatial attention lingers in retinotopic coordinates immediately following gaze shifts

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)

Atypical disengagement from faces and its modulation by the control of eye fixation in children with Autism Spectrum Disorder

By using the gap overlap task, we investigated disengagement from faces and objects in children (9–17 years old) with and without autism spectrum disorder (ASD) and its neurophysiological correlates. In typically developing (TD) children, faces elicited larger gap effect, an index of attentional engagement, and larger saccade-related event-related potentials (ERPs), compared to objects. In children with ASD, by contrast, neither gap effect nor ERPs differ between faces and objects. Follow-up experiments demonstrated that instructed fixation on the eyes induces larger gap effect for faces in children with ASD, whereas instructed fixation on the mouth can disrupt larger gap effect in TD children. These results suggest a critical role of eye fixation on attentional engagement to faces in both groups