Difference Between Visually and Electrically Evoked Gaze Saccades Disclosed by Altering the Head Moment of Inertia

2000 ◽  
Vol 83 (2) ◽  
pp. 1103-1107 ◽  
Author(s):  
Alexandre J. F. Coimbra ◽  
Philippe Lefèvre ◽  
Marcus Missal ◽  
Etienne Olivier
Keyword(s):  
Head Movements ◽  
Moment Of Inertia ◽  
Gaze Shifts ◽  
Feedback Information ◽  
Slowing Down ◽  
Movement Dynamics ◽  
On Line ◽  
Gaze Saccades ◽  
Visually Evoked Saccades

Differences between gaze shifts evoked by collicular electrical stimulation and those triggered by the presentation of a visual stimulus were studied in head-free cats by increasing the head moment of inertia. This maneuver modified the dynamics of these two types of gaze shifts by slowing down head movements. Such an increase in the head moment of inertia did not affect the metrics of visually evoked gaze saccades because their duration was precisely adjusted to compensate for these changes in movement dynamics. In contrast, the duration of electrically evoked gaze shifts remained constant irrespective of the head moment of inertia, and therefore their amplitude was significantly reduced. These results suggest that visually and electrically evoked gaze saccades are controlled by different mechanisms. Whereas the accuracy of visually evoked saccades is likely to be assured by on-line feedback information, the absence of duration adjustment in electrically evoked gaze shifts suggests that feedback information necessary to maintain their metrics is not accessible or is corrupted during collicular stimulation. This is of great importance when these two types of movements are compared to infer the role of the superior colliculus in the control of orienting gaze shifts.

scholarly journals Effect of Reversible Inactivation of Superior Colliculus on Head Movements

2008 ◽  
Vol 99 (5) ◽  
pp. 2479-2495 ◽  
Author(s):  
Mark M. G. Walton ◽  
Bernard Bechara ◽  
Neeraj J. Gandhi
Keyword(s):  
Superior Colliculus ◽  
Reaction Times ◽  
Movement Control ◽  
Head Movements ◽  
Gaze Shifts ◽  
Gaze Shift ◽  
Reversible Inactivation ◽  
The Gaze ◽  
Made In

Because of limitations in the oculomotor range, many gaze shifts must be accomplished using coordinated movements of the eyes and head. Stimulation and recording data have implicated the primate superior colliculus (SC) in the control of these gaze shifts. The precise role of this structure in head movement control, however, is not known. The present study uses reversible inactivation to gain insight into the role of this structure in the control of head movements, including those that accompany gaze shifts and those that occur in the absence of a change in gaze. Forty-five lidocaine injections were made in two monkeys that had been trained on a series of behavioral tasks that dissociate movements of the eyes and head. Reversible inactivation resulted in clear impairments in the animals’ ability to perform gaze shifts, manifested by increased reaction times, lower peak velocities, and increased durations. In contrast, comparable effects were not found for head movements (with or without gaze shifts) with the exception of a very small increase in reaction times of head movements associated with gaze shifts. Eye-head coordination was clearly affected by the injections with gaze onset occurring relatively later with respect to head onset. Following the injections, the head contributed slightly more to the gaze shift. These results suggest that head movements (with and without gaze shifts) can be controlled by pathways that do not involve SC.

Combined eye-head gaze shifts in the primate. III. Contributions to the accuracy of gaze saccades

1990 ◽  
Vol 64 (6) ◽  
pp. 1873-1891 ◽  
Author(s):  
R. D. Tomlinson
Keyword(s):  
Head Movement ◽  
Head Movements ◽  
Whole Body ◽  
Midsagittal Plane ◽  
Gaze Shifts ◽  
Gaze Shift ◽  
The Gaze ◽  
Gaze Stability ◽  
Gaze Saccade ◽  
Gaze Saccades

1. The behavior of the combined eye-head gaze saccade mechanism was investigated in the rhesus monkey under both normal circumstances and in the presence of perturbations delivered to the head by a torque motor. Animals were trained to follow a target light that stepped at regular intervals through an angle of 68 degrees (+/- 34 degrees with respect to the midsagittal plane). Thus all primary saccades were center crossing. On randomly occurring trials the torque motor was pulsed so as to perturb the trajectory of the head, thus allowing us to assess both the functional state of the vestibuloocular reflex (VOR) and the effects of such perturbations on gaze saccade accuracy (gaze is defined as the sum of eye-in-head plus head-in-space, and a gaze saccade as a combined eye-head saccadic gaze shift). 2. Gaze shifts can be divided into two discrete sections: the portion during which the gaze angle is changing (the saccadic portion), and the portion during which the gaze is stationary but the head continues to move (the terminal head-movement portion). For the system to accurately acquire eccentric targets, at least two criteria must be met: 1) the saccadic portion must be accurate, and 2) the compensatory eye movement that occurs during the terminal head-movement portion must be equal and opposite to the head movement, thereby maintaining gaze stability. Perturbations delivered during the terminal head-movement portion of the gaze shift indicated that VOR was functioning normally, and thus we concluded that the compensatory eye movements that accompany head movements were vestibular in origin. 3. As reported previously, during the saccadic portion of large-amplitude gaze saccades, the VOR ceases to function. In spite of this observation, the accuracy of the gaze saccade is not affected by perturbations delivered to the head. Gaze accuracy is maintained both by changing the duration of the saccadic portion and by altering the head trajectory. 4. Because rhesus monkeys often make very rapid head movements (1,200 degrees/s), we wished to discover the velocity range over which the monkey VOR might be expected to operate. Accordingly, in a second series of experiments, VOR function was assessed during passive whole-body rotations with the head fixed. By the use of spring-assisted manual rotations, peak velocities up to 850 degrees/s were achieved. When VOR gain was measured during such rotations, it was found to be equal to 0.9 up to the maximum velocities used.(ABSTRACT TRUNCATED AT 400 WORDS)

In Multiple-Step Gaze Shifts: Omnipause (OPNs) and Collicular Fixation Neurons Encode Gaze Position Error; OPNs Gate Saccades

2002 ◽  
Vol 88 (4) ◽  
pp. 1726-1742 ◽  
Author(s):  
André Bergeron ◽  
Daniel Guitton
Keyword(s):  
Superior Colliculus ◽  
Firing Frequency ◽  
Position Error ◽  
Head Movements ◽  
Gaze Shifts ◽  
Gaze Saccade ◽  
Saccade Onset ◽  
Gaze Position ◽  
Gaze Saccades ◽  
Multiple Step

The superior colliculus (SC), via its projections to the pons, is a critical structure for driving rapid orienting movements of the visual axis, called gaze saccades, composed of coordinated eye-head movements. The SC contains a motor map that encodes small saccade vectors rostrally and large ones caudally. A zone in the rostral pole may have a different function. It contains superior colliculus fixation neurons (SCFNs) with probable projections to omnipause neurons (OPNs) of the pons. SCFNs and OPNs discharge tonically during visual fixation and pause during single-step gaze saccades. The OPN tonic discharge inhibits saccades and its cessation (pause) permits saccade generation. We have proposed that SCFNs control the OPN discharge. We compared the discharges of SCFNs and OPNs recorded while cats oriented horizontally, to the left and right, in the dark to a remembered target. Cats used multiple-step gaze shifts composed of a series of small gaze saccades, of variable amplitude and number, separated by periods of variable duration (plateaus) in which gaze was immobile or moving at low velocity (<25°/s). Just after contralaterally (ipsilaterally) presented targets, the firing frequency of SCFNs decreased to almost zero (remained constant at background). As multiple-step gaze shifts progressed in either direction in the dark, these activity levels prevailed until the distance between gaze and target [gaze position error (GPE)] reached ∼16°. At this point, firing frequency gradually increased, without saccade-related pauses, until a maximum was reached when gaze arrived on target location (GPE = 0°). SCFN firing frequency encoded GPE; activity was not correlated to characteristics or occurrence of gaze saccades. By comparison, after target presentation to left or right, OPN activity remained steady at pretarget background until first gaze saccade onset, during which activity paused. During the first plateau, activity resumed at a level lower than background and continued at this level during subsequent plateaus until GPE ∼8° was reached. As GPE decreased further, tonic activity during plateaus gradually increased until a maximum (greater than background) was reached when gaze was on goal (GPE = 0°). OPNs, like SCFNs, encoded GPE, but they paused during every gaze saccade, thereby revealing, unlike for SCFNs, strong coupling to motor events. The firing frequency increase in SCFNs as GPE decreased, irrespective of trajectory characteristics, implies these cells get feedback on GPE, which they may communicate to OPNs. We hypothesize that at the end of a gaze-step sequence, impulses from SCFNs onto OPNs may suppress further movements away from the target.

scholarly journals The Mediterranean Diet, a Rich Source of Angiopreventive Compounds in Cancer

Nutrients ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 2036 ◽  
Author(s):  
Beatriz Martínez-Poveda ◽  
José Antonio Torres-Vargas ◽  
María del Carmen Ocaña ◽  
Melissa García-Caballero ◽  
Miguel Ángel Medina ◽  
...  
Keyword(s):  
Mediterranean Diet ◽  
Essential Role ◽  
Chemopreventive Agents ◽  
Angiogenic Potential ◽  
Slowing Down ◽  
Interesting Approach ◽  
The Mediterranean ◽  
Tumor Growth And Metastasis ◽  
Early Phases

Diet-based chemoprevention of cancer has emerged as an interesting approach to evade the disease or even target its early phases, reducing its incidence or slowing down tumor progression. In its basis in the essential role of angiogenesis for tumor growth and metastasis, angioprevention proposes the use of inhibitors of angiogenesis in cancer prevention. The anti-angiogenic potential exhibited by many natural compounds contained in many Mediterranean diet constituents makes this dietary pattern especially interesting as a source of chemopreventive agents, defined within the angioprevention strategy. In this review, we focus on natural bioactive compounds derived from the main foods included in the Mediterranean diet that display anti-angiogenic activity, as well as their possible use as angiopreventive agents.

scholarly journals The Role of Prosodic Breaks and Pitch Accents in Grouping Words during On-line Sentence Processing

2011 ◽  
Vol 23 (9) ◽  
pp. 2447-2467 ◽  
Author(s):  
Sara Bögels ◽  
Herbert Schriefers ◽  
Wietske Vonk ◽  
Dorothee J. Chwilla
Keyword(s):  
Sentence Processing ◽  
Information Structure ◽  
Pitch Accent ◽  
Semantic Interpretation ◽  
N400 Effect ◽  
Cambridge University ◽  
On Line ◽  
Group Words ◽  
Pitch Accents

The present study addresses the question whether accentuation and prosodic phrasing can have a similar function, namely, to group words in a sentence together. Participants listened to locally ambiguous sentences containing object- and subject-control verbs while ERPs were measured. In Experiment 1, these sentences contained a prosodic break, which can create a certain syntactic grouping of words, or no prosodic break. At the disambiguation, an N400 effect occurred when the disambiguation was in conflict with the syntactic grouping created by the break. We found a similar N400 effect without the break, indicating that the break did not strengthen an already existing preference. This pattern held for both object- and subject-control items. In Experiment 2, the same sentences contained a break and a pitch accent on the noun following the break. We argue that the pitch accent indicates a broad focus covering two words [see Gussenhoven, C. On the limits of focus projection in English. In P. Bosch & R. van der Sandt (Eds.), Focus: Linguistic, cognitive, and computational perspectives. Cambridge: University Press, 1999], thus grouping these words together. For object-control items, this was semantically possible, which led to a “good-enough” interpretation of the sentence. Therefore, both sentences were interpreted equally well and the N400 effect found in Experiment 1 was absent. In contrast, for subject-control items, a corresponding grouping of the words was impossible, both semantically and syntactically, leading to processing difficulty in the form of an N400 effect and a late positivity. In conclusion, accentuation can group words together on the level of information structure, leading to either a semantically “good-enough” interpretation or a processing problem when such a semantic interpretation is not possible.

Moments of inertia and B(E2;01+→21+)s in the NpNn scheme

2015 ◽  
Vol 93 (7) ◽  
pp. 711-715
Author(s):  
Rajesh Kumar ◽  
S. Sharma
Keyword(s):  
Nuclear Structure ◽  
Strong Dependence ◽  
Moment Of Inertia ◽  
Nucleon Pair ◽  
Valence Nucleon ◽  
Moments Of Inertia ◽  
Ground Band ◽  
Neutron Interaction ◽  
Medium Mass

We examine the collective nuclear structure of light and medium mass (Z = 50–82, N = 82–126) even–even nuclei using valence nucleon pair product (NpNn). We discuss the role of proton–neutron interaction in light mass nuclei and illustrate the variation of observables of collectivity and deformation (i.e., ground band moment of inertia) and B(E2) values with N and NpNn). The plot of these observables against NpNn vividly displays the formation of isotonic multiplets in quadrant I, strong dependence on NpNn in quadrant II and weak constancy with Z in quadrant III is illustrated.

scholarly journals The Animation of Gamers and the Gamers as Animators in Sierra On-Line’s Adventure Games

Animation ◽  
2021 ◽  
Vol 16 (1-2) ◽  
pp. 83-95
Author(s):  
Raz Greenberg
Keyword(s):  
Video Games ◽  
Digital Games ◽  
Free Play ◽  
Digital Gaming ◽  
Adventure Game ◽  
Adventure Games ◽  
Software Publisher ◽  
On Line ◽  
The Relationship

Produced throughout the 1980s using the company’s Adventure Game Interpreter engine, the digital adventure games created by American software publisher Sierra On-Line played an important and largely overlooked role in the development of animation as an integral part of the digital gaming experience. While the little historical and theoretical discussion of the company’s games of the era focuses on their genre, it ignores these games’ contribution to the relationship between the animated avatars and the gamers that control them – a relationship that, as argued in this article, in essence turns gamers into animators. If we consider Chris Pallant’s (2019) argument in ‘Video games and animation’ that animation is essential to the sense of immersion within a digital game, then the great freedom provided to the gamers in animating their avatars within Sierra On-Line’s adventure games paved the way to the same sense of immersion in digital. And, if we refer to Gonzalo Frasca’s (1999) divide of digital games to narrative-led or free-play (ludus versus paidea) in ‘Ludology meets narratology: Similitude and differences between (video) games and narrative’, then the company’s adventure games served as an important early example of balance between the two elements through the gamers’ ability to animate their avatars. Furthermore, Sierra On-Line’s adventure games have tapped into the traditional tension between the animator and the character it animated, as observed by Scott Bukatman in ‘The poetics of Slumberland: Animated spirits and the animated spirit (2012), when he challenged the traditional divide between animators, the characters they animate and the audience. All these contributions, as this articles aims to demonstrate, continue to influence the role of animation in digital games to this very day.

Sign in / Sign up

Export Citation Format

Share Document