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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1966

Oculometry.

Eye control in relation to visual process, showing derivation of position information from pointing of eyeball

EYE MOVEMENT↗
NASA NTRS1967

The oculometer

Automatic acquisition and tracking of pupil-iris boundary and of corneal reflection of light source in oculometer using electro-optic method for eye direction measurement

DATA ACQUISITION↗
NASA NTRS2003

Shared motion signals for human perceptual decisions and oculomotor actions

A fundamental question in primate neurobiology is to understand to what extent motor behaviors are driven by shared neural signals that also support conscious perception or by independent subconscious neural signals dedicated to motor control. Although it has clearly been established that cortical areas involved in processing visual motion support both perception and smooth pursuit eye movements, it remains unknown whether the same or different sets of neurons within these structures perform these two functions. Examination of the trial-by-trial variation in human perceptual and pursuit responses during a simultaneous psychophysical and oculomotor task reveals that the direction signals for pursuit and perception are not only similar on average but also co-vary on a trial-by-trial basis, even when performance is at or near chance and the decisions are determined largely by neural noise. We conclude that the neural signal encoding the direction of target motion that drives steady-state pursuit and supports concurrent perceptual judgments emanates from a shared ensemble of cortical neurons.

Visual Cortex/physiology↗
NASA NTRS2003

Functional organization of human intraparietal and frontal cortex for attending, looking, and pointing

We studied the functional organization of human posterior parietal and frontal cortex using functional magnetic resonance imaging (fMRI) to map preparatory signals for attending, looking, and pointing to a peripheral visual location. The human frontal eye field and two separate regions in the intraparietal sulcus were similarly recruited in all conditions, suggesting an attentional role that generalizes across response effectors. However, the preparation of a pointing movement selectively activated a different group of regions, suggesting a stronger role in motor planning. These regions were lateralized to the left hemisphere, activated by preparation of movements of either hand, and included the inferior and superior parietal lobule, precuneus, and posterior superior temporal sulcus, plus the dorsal premotor and anterior cingulate cortex anteriorly. Surface-based registration of macaque cortical areas onto the map of fMRI responses suggests a relatively good spatial correspondence between human and macaque parietal areas. In contrast, large interspecies differences were noted in the topography of frontal areas.

NASA Discipline Neuroscience↗
NASA NTRS2003

Ocular motor responses to abrupt interaural head translation in normal humans

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (approximately 200 ms), high-acceleration (0.4-1.4g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 +/- 5 ms at 15-cm and 20 +/- 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head velocity) was 0.38 and 0.37, and the median velocity gain, 0.52 and 0.62, at 15- and 30-cm viewing, respectively. These results suggest the tVOR scales proportionally at these viewing distances. Likewise, at both viewing distances, peak eye velocity scaled linearly with peak head velocity and gain was independent of peak head acceleration. A saccade commonly occurred in the compensatory direction, with a greater latency (165 vs. 145 ms) and lesser amplitude (1.8 vs. 3.2 deg) at 30- than 15-cm viewing. Even with saccades, the overall gain at the end of head movement was still considerably undercompensatory (medians 0.68 and 0.77 at 15- and 30-cm viewing). Monocular viewing was also assessed at 15-cm viewing. In 4 of 6 subjects, gains were the same as during binocular viewing and scaled closely with vergence angle. In sum the low tVOR gain and scaling of the response with viewing distance and head velocity extend previous results to higher acceleration stimuli. tVOR latency (approximately 20 ms) was lower than previously reported. Saccades are an integral part of the tVOR, and also scale with viewing distance.

Non-NASA Center↗
NASA NTRS2002

Heading perception in patients with advanced retinitis pigmentosa

PURPOSE: We investigated whether retinis pigmentosa (RP) patients with residual visual field of < 100 degrees could perceive heading from optic flow. METHODS: Four RP patients and four age-matched normally sighted control subjects viewed displays simulating an observer walking over a ground. In experiment 1, subjects viewed either the entire display with free fixation (full-field condition) or through an aperture with a fixation point at the center (aperture condition). In experiment 2, patients viewed displays of different durations. RESULTS: RP patients' performance was comparable to that of the age-matched control subjects: heading judgment was better in the full-field condition than in the aperture condition. Increasing display duration from 0.5 s to 1 s improved patients' heading performance, but giving them more time (3 s) to gather more visual information did not consistently further improve their performance. CONCLUSIONS: RP patients use active scanning eye movements to compensate for their visual field loss in heading perception; they might be able to gather sufficient optic flow information for heading perception in about 1 s.

Visual Perception↗
NASA NTRS2002

Context-specific adaptation of the gain of the oculomotor response to lateral translation using roll and pitch head tilts as contexts

Previous studies established that vestibular and oculomotor behaviors can have two adapted states (e.g., gain) simultaneously, and that a context cue (e.g., vertical eye position) can switch between the two states. The present study examined this phenomenon of context-specific adaptation for the oculomotor response to interaural translation (which we term "linear vestibulo-ocular reflex" or LVOR even though it may have extravestibular components). Subjects sat upright on a linear sled and were translated at 0.7 Hz and 0.3 gpeak acceleration while a visual-vestibular mismatch paradigm was used to adaptively increase (x2) or decrease (x0) the gain of the LVOR. In each experimental session, gain increase was asked for in one context, and gain decrease in another context. Testing in darkness with steps and sines before and after adaptation, in each context, assessed the extent to which the context itself could recall the gain state that was imposed in that context during adaptation. Two different contexts were used: head pitch (26 degrees forward and backward) and head roll (26 degrees or 45 degrees, right and left). Head roll tilt worked well as a context cue: with the head rolled to the right the LVOR could be made to have a higher gain than with the head rolled to the left. Head pitch tilt was less effective as a context cue. This suggests that the more closely related a context cue is to the response being adapted, the more effective it is.

Non-NASA Center↗
NASA NTRS2001

The human oculomotor response to simultaneous visual and physical movements at two different frequencies

In order to investigate interactions in the visual and vestibular systems' oculomotor response to linear movement, we developed a two-frequency stimulation technique. Thirteen subjects lay on their backs and were oscillated sinusoidally along their z-axes at between 0.31 and 0.81 Hz. During the oscillation subjects viewed a large, high-contrast, visual pattern oscillating in the same direction as the physical motion but at a different, non-harmonically related frequency. The evoked eye movements were measured by video-oculography and spectrally analysed. We found significant signal level at the sum and difference frequencies as well as at other frequencies not present in either stimulus. The emergence of new frequencies indicates non-linear processing consistent with an agreement-detector system that have previously proposed.

NASA Discipline Neuroscience↗