Visual selective attention and the control of tracking eye movements: a critical review

People’s eyes are directed at objects of interest with the aim of acquiring visual information. However, processing this information is constrained in capacity, requiring task-driven and salience-driven attentional mechanisms to select few among the many available objects. A wealth of behavioral and neurophysiological evidence has demonstrated that visual selection and the motor selection of saccade targets rely on shared mechanisms. This coupling supports the premotor theory of visual attention put forth more than 30 years ago, postulating visual selection as a necessary stage in motor selection. In this review, we examine to which extent the coupling of visual and motor selection observed with saccades is replicated during ocular tracking. Ocular tracking combines catch-up saccades and smooth pursuit to foveate a moving object. We find evidence that ocular tracking requires visual selection of the speed and direction of the moving target, but the position of the motion signal may not coincide with the position of the pursuit target. Further, visual and motor selection can be spatially decoupled when pursuit is initiated (open-loop pursuit). We propose that a main function of coupled visual and motor selection is to serve the coordination of catch-up saccades and pursuit eye movements. A simple race-to-threshold model is proposed to explain the variable coupling of visual selection during pursuit, catch-up and regular saccades, while generating testable predictions. We discuss pending issues, such as disentangling visual selection from preattentive visual processing and response selection, and the pinpointing of visual selection mechanisms, which have begun to be addressed in the neurophysiological literature.

Prevalence of Ocular Abnormalities in Term Infants

Objective: To exhibit the results of routine ophthalmologic screening in infants between 0-1 years of age referred to the ophthalmology clinic from the departments of pediatrics and family medicine. Method: Referred to the ophthalmology clinic between August 2014 and November 2019, 11196 eyes of 5598 term infants were retrospectively investigated in the study, and all participants were ophthalmologically examined at 1st, 6th, and 12th months of age. Infants’ pupils were dilated with 0.5% tropicamide and 2.5% phenylephrine. On examination, eye and face symmetries were evaluated with inspection, fixation, and ocular tracking. Pupil responses and motility were evaluated with the light source. While the red reflex test was evaluated using a direct ophthalmoscope, fundus was assessed through an indirect ophthalmoscope. Results: Congenital cataract (6), congenital glaucoma (3), strabismus (81), epiphora (426), non-specific retinal hemorrhages (42) and retinal pigmentation changes (10), coloboma (4) (one eyelid, four iris, one optical disc and three chorioretinal), optic disc abnormalities (3), congenital ptosis (13) (unilateral in 12 patients and bilateral in one patient), corneal dysgenesis (2) and microphthalmia (3) were determined in 11196 eyes of 5598 infants (2709 females, 2889 males). Conclusion: Perinatal ophthalmologic screening program is likely to diagnose several diseases earlier, such as congenital cataracts, congenital glaucoma, strabismus, corneal opacities, causing vision losses in infants. Treatment options are available, and some diseases can be treated due to early intervention. Early treatment can also eliminate the problems precluding the development of complex visual ability continuing in perinatal period. Consequently, final visual acuity may be increased.

A relação do usuário surdo com a tipografia em movimento nos materiais educacionais em Libras: um estudo por meio do rastreamento ocular | The relation of the deaf user with type in motion in educational materials in Brazilian Sign Language: a study with ocular tracing

As tecnologias de informação proporcionaram avanços na comunicação para usuários com necessidades especiais, tais como os surdos, que utilizam a língua de sinais (LIBRAS) para trocar informações. Atualmente, é obrigatória a oferta de ensino bilíngue (Libras – Português) aos alunos surdos. Em materiais educacionais digitais para deficientes auditivos é comum identificar o conteúdo sendo apresentado por diferentes elementos de mídia, como vídeos, imagens e texto em movimento de maneira simultânea. Desta forma, o presente artigo verificou os principais focos de atenção do usuário surdo tendo em vista a tipografia em movimento em materiais didáticos bilíngues. Para tanto, realizou um estudo por meio do rastreamento ocular com o auxílio do equipamento eye trackingna interação de um usuário surdo com conteúdos educacionais desenvolvidos pelo Instituto Nacional de Educação para Surdos (INES) juntamente com uma entrevista. Como resultado percebeu-se a dificuldade na compreensão das informações simultâneas, a preferência pelo conteúdo apresentado em Libras, bem como a possibilidade de melhorias nos materiais didáticos destinados ao público surdo.*****Information technologies have provided advances in communication for users with special needs, such as deaf people, who use sign language to exchange information. Currently, the offer of bilingual education in Brazil is compulsory for deaf students. In digital educational materials for the hearing impaired is common to identify the content being presented by different media elements, such as videos, images and moving text simultaneously. Therefore, the present paper verified the main attention focuses of the deaf user in view of the typography in motion in bilingual didactic material. To do so, a study was carried out using ocular tracking with the aid of eye-tracking equipment in the interaction of a deaf user with educational content developed by the National Institute of Education for the Deaf (INES - Brazil) together with an interview. As a result, the difficulty in understanding the information presented by different elements of the media simultaneously was perceived. Also, the preference for the content presented in Libras was identified, as well as the possibility of improvements in the didactic material destined to the deaf public.

ORIENTATION IN SPACE, VESTIBULAR FUNCTION AND OCULAR TRACKING IN THE CHANGED GRAVITATIONAL ENVIRONMENT

The paper reports results of the author's sensorimotor physiology studies made under the guidance of I.B.Kozlovskaya. The vestibular function and ocular tracking tests were performed by more than 100 cosmonauts prior to and after long-term missions to the Mir and International space station. Fifty two of them implemented these tests between mission days 129 to 215. We studies orientation illusions, spontaneous eye movements, static vestibulo-ocular response to head turns (static otolith-cervical reflex), dynamic vestibulo-ocular reactions to the head roll about the body axis, precision of fixational eye movements, and smooth tracking. Results of testing in the real changed gravity were compared with the data from 7 to 21-day simulation studies in horizontal dry immersion. The tests revealed 4 forms of vestibular disorders characterized by disturbances of spatial perception, orientation illusions, inversions of vection illusions, weakening of static and strengthening of dynamic vestibulo-ocular reactions, a new visual tracking strategy termed a saccadic approximation, that is the gaze approaches or tracks a target using a series of saccadic movements. In addition, the tests made it possible to specify the impact of afferentation deficit (sensory deprivation) on accuracy of ocular and ocular-manual tracking and validate additional sensory stimulation as a method to counteract the effects of sensory deprivation in real and simulated microgravity.

Role of motor execution in the ocular tracking of self-generated movements

When human observers track the movements of their own hand with their gaze, the eyes can start moving before the finger (i.e., anticipatory smooth pursuit). The signals driving anticipation could come from motor commands during finger motor execution or from motor intention and decision processes associated with self-initiated movements. For the present study, we built a mechanical device that could move a visual target either in the same direction as the participant's hand or in the opposite direction. Gaze pursuit of the target showed stronger anticipation if it moved in the same direction as the hand compared with the opposite direction, as evidenced by decreased pursuit latency, increased positional lead of the eye relative to target, increased pursuit gain, decreased saccade rate, and decreased delay at the movement reversal. Some degree of anticipation occurred for incongruent pursuit, indicating that there is a role for higher-level movement prediction in pursuit anticipation. The fact that anticipation was larger when target and finger moved in the same direction provides evidence for a direct coupling between finger and eye motor commands.

LRP predicts smooth pursuit eye movement onset during the ocular tracking of self-generated movements

Several studies have indicated that human observers are very efficient at tracking self-generated hand movements with their gaze, yet it is not clear whether this is simply a by-product of the predictability of self-generated actions or if it results from a deeper coupling of the somatomotor and oculomotor systems. In a first behavioral experiment we compared pursuit performance as observers either followed their own finger or tracked a dot whose motion was externally generated but mimicked their finger motion. We found that even when the dot motion was completely predictable in terms of both onset time and kinematics, pursuit was not identical to that produced as the observers tracked their finger, as evidenced by increased rate of catch-up saccades and by the fact that in the initial phase of the movement gaze was lagging behind the dot, whereas it was ahead of the finger. In a second experiment we recorded EEG in the attempt to find a direct link between the finger motor preparation, indexed by the lateralized readiness potential (LRP) and the latency of smooth pursuit. After taking into account finger movement onset variability, we observed larger LRP amplitudes associated with earlier smooth pursuit onset across trials. The same held across subjects, where average LRP onset correlated with average eye latency. The evidence from both experiments concurs to indicate that a strong coupling exists between the motor systems leading to eye and finger movements and that simple top-down predictive signals are unlikely to support optimal coordination.