scholarly journals Prefrontal Neuronal Activity Encodes Spatial Target Representations Sequentially Updated After Nonspatial Target-Shift Cues

2004 ◽  
Vol 91 (3) ◽  
pp. 1367-1380 ◽  
Author(s):  
Tetsuya Fukushima ◽  
Isao Hasegawa ◽  
Yasushi Miyashita
Keyword(s):  
Neuronal Activity ◽  
Target Location ◽  
Spatial Working Memory ◽  
Target Position ◽  
Saccade Target ◽  
Visual Response ◽  
Initial Saccade ◽  
Preparatory Set ◽  
Dominant Activity ◽  
Selective Activity

We examined prefrontal neuronal activity while monkeys performed a sequential target-shift task, in which, after a positional cue indicated the initial saccade target among 8 peripheral positions, the monkeys were required to internally shift the target by one position on every flash of a target-shift cue. The target-shift cue appeared in the center 0 to 3 times within a single trial and was always the same in shape, size, and color. We found selective neuronal activity related to the target position: when the target-shift cue implied the target shift to particular peripheral positions, neurons exhibited early-dominant and late-dominant activity during the following delay period. The early-dominant target-selective activity emerged early in the delay just after the presentation of the target-shift cue, whereas the late-dominant activity gradually built up toward the end of the delay. Because the target-shift cue was not related to any specific target location, the early-dominant target-selective activity could not be a mere visual response to the target-shift cue. We suggest that the early-dominant activity reflects the transitory representation for the saccade target that was triggered by the nonspatial target-shift cue, whereas the late-dominant activity reflects the target representation in the spatial working memory or the preparatory set for the possible impending saccade, being repeatedly updated during sequential target shifts.

Neuronal activity in the supplementary eye field during acquisition of conditional oculomotor associations

1995 ◽  
Vol 73 (3) ◽  
pp. 1101-1121 ◽  
Author(s):  
L. L. Chen ◽  
S. P. Wise
Keyword(s):  
Neuronal Activity ◽  
Target Location ◽  
Discharge Rate ◽  
Premotor Cortex ◽  
Stimulus Response ◽  
Association Learning ◽  
Supplementary Eye Field ◽  
Eye Field ◽  
Correct Saccade ◽  
Selective Activity

1. The supplementary eye field (SEF) has been viewed as a premotor cortical field for the selection and control of saccadic eye movements. Drawing on studies of the neighboring premotor cortex, we hypothesized that if the SEF participates in the selection of action based on arbitrary stimulus-response associations, then task-related activity in the SEF should change during the learning of such associations. 2. Rhesus monkeys were operantly conditioned to make a saccadic eye movement to one of four targets (7 deg up, down, left, and right from center) in response to a foveal instruction stimulus (IS). One and only one of those four possible responses was arbitrarily designated "correct" for each IS. The monkeys responded to familiar ISs, four stimuli that remained unchanged throughout training and recording, as well as to novel ISs, which the monkeys had not previously seen. The monkeys initially chose responses to novel stimuli by trial and error, with near chance levels of performance, but quickly learned to select the correct saccade. 3. We studied 186 SEF cells as monkeys learned new visuomotor associations. Neuronal activity was quantified in four task periods: during the presentation of the IS, during an instructed delay period (i.e., after the removal of the IS but before a trigger or "go" stimulus), just before the saccade, and after the saccade during fixation of the target location. The discharge rate in each task period was considered a separate case for analysis, compared with that in a reference period preceding the IS, and eliminated from further analysis if not significantly different. 4. We observed two main categories of activity change during learning, which we termed learning selective and learning dependent. Learning-selective cases showed a significant evolution in activity as the monkeys learned which saccade was instructed by a novel IS, but had no significant modulation during trials with familiar ISs. Many of these cells were virtually inactive on trials with familiar ISs. However, they initially showed dramatic modulation when tested with a novel IS. As the monkey chose the correct saccade (or target) with increasing reliability, the modulation often decremented until the cell was again relatively unmodulated, as observed during familiar-IS trials. These cells usually remained relatively inactive until the monkeys were challenged to start learning another new stimulus-response association. Learning-selective activity was observed in all task periods, and 33 (18%) of the 186 adequately tested SEF cells showed learning-selective activity in one or more task periods.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of Saccade Efference Copy on the Spatiotemporal Properties of Remapping: A Neural Network Study

2010 ◽  
Vol 103 (1) ◽  
pp. 117-139 ◽  
Author(s):  
Gerald P. Keith ◽  
Gunnar Blohm ◽  
J. Douglas Crawford
Keyword(s):  
Neural Network ◽  
Target Position ◽  
Efference Copy ◽  
Saccade Target ◽  
Visual Response ◽  
Topographic Map ◽  
Velocity Signal ◽  
Ev Model ◽  
Hidden Layer ◽  
Eye Velocity

Remapping of gaze-centered target-position signals across saccades has been observed in the superior colliculus and several cortical areas. It is generally assumed that this remapping is driven by saccade-related signals. What is not known is how the different potential forms of this signal (i.e., visual, visuomotor, or motor) might influence this remapping. We trained a three-layer recurrent neural network to update target position (represented as a “hill” of activity in a gaze-centered topographic map) across saccades, using discrete time steps and backpropagation-through-time algorithm. Updating was driven by an efference copy of one of three saccade-related signals: a transient visual response to the saccade-target in two-dimensional (2-D) topographic coordinates ( Vtop), a temporally extended motor burst in 2-D topographic coordinates ( Mtop), or a 3-D eye velocity signal in brain stem coordinates ( EV). The Vtop model produced presaccadic remapping in the output layer, with a “jumping hill” of activity and intrasaccadic suppression. The Mtop model also produced presaccadic remapping with a dispersed moving hill of activity that closely reproduced the quantitative results of Sommer and Wurtz. The EV model produced a coherent moving hill of activity but failed to produce presaccadic remapping. When eye velocity and a topographic (Vtop or Mtop) updater signal were used together, the remapping relied primarily on the topographic signal. An analysis of the hidden layer activity revealed that the transient remapping was highly dispersed across hidden-layer units in both Vtop and Mtop models but tightly clustered in the EV model. These results show that the nature of the updater signal influences both the mechanism and final dynamics of remapping. Taken together with the currently known physiology, our simulations suggest that different brain areas might rely on different signals and mechanisms for updating that should be further distinguishable through currently available single- and multiunit recording paradigms.

Organization of local horizontal functional interactions between neurons in the inferior temporal cortex of macaque monkeys

2014 ◽  
Vol 111 (12) ◽  
pp. 2589-2602 ◽  
Author(s):  
Hiroshi Tamura ◽  
Yoshiya Mori ◽  
Hidekazu Kaneko
Keyword(s):  
Neuronal Activity ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Visual Object ◽  
Detailed Knowledge ◽  
Visual Response ◽  
Stimulus Preference ◽  
Macaque Monkeys ◽  
Functional Interactions ◽  
Cross Correlation Analysis

Detailed knowledge of neuronal circuitry is necessary for understanding the mechanisms underlying information processing in the brain. We investigated the organization of horizontal functional interactions in the inferior temporal cortex of macaque monkeys, which plays important roles in visual object recognition. Neuronal activity was recorded from the inferior temporal cortex using an array of eight tetrodes, with spatial separation between paired neurons up to 1.4 mm. We evaluated functional interactions on a time scale of milliseconds using cross-correlation analysis of neuronal activity of the paired neurons. Visual response properties of neurons were evaluated using responses to a set of 100 visual stimuli. Adjacent neuron pairs tended to show strong functional interactions compared with more distant neuron pairs, and neurons with similar stimulus preferences tended to show stronger functional interactions than neurons with different stimulus preferences. Thus horizontal functional interactions in the inferior temporal cortex appear to be organized according to both cortical distances and similarity in stimulus preference between neurons. Furthermore, the relationship between strength of functional interactions and similarity in stimulus preference observed in distant neuron pairs was more prominent than in adjacent pairs. The results suggest that functional circuitry is specifically organized, depending on the horizontal distances between neurons. Such specificity endows each circuit with unique functions.

Functional properties of monkey caudate neurons. III. Activities related to expectation of target and reward

1989 ◽  
Vol 61 (4) ◽  
pp. 814-832 ◽  
Author(s):  
O. Hikosaka ◽  
M. Sakamoto ◽  
S. Usui
Keyword(s):  
Spatial Information ◽  
Target Location ◽  
Hand Movement ◽  
Visual Fixation ◽  
Saccade Target ◽  
Tonic Activity ◽  
Sustained Activity ◽  
Neural Activities ◽  
Reward Expectancy ◽  
Mouth Movement

1. The present paper reports complex neural activities in the monkey caudate nucleus that precede and anticipate visual stimuli and reward in learned visuomotor paradigms. These activities were revealed typically in the delayed saccade task in which memory and anticipation were required. We classified these activities according to their relationships to the task. 2. Activity related to expectation of a cue (n = 46) preceded the presentation of a spot of light (target cue) that signified the future location of saccade target. When the target cue was delayed, the activity was prolonged accordingly. The same spot of light was preceded by no activity if it acted as a distracting stimulus. 3. The sustained activity (n = 80) was a tonic discharge starting after the target cue as if holding the spatial information. 4. The activity related to expectation of target (n = 109) preceded the appearance of the target whose location was cued previously. It started with or after a saccade to the cued target location and ended with the appearance of the target. The activity was greater when the target was expected to appear in the contralateral visual field. 5. The activity related to expectation of reward (n = 57) preceded a task-specific reward. It started with the appearance of the final target and ended with the reward. In most cases, the activity was nonselective for how the monkey obtained the reward, i.e., by visual fixation only, by a saccade, or by a hand movement. The activity was dependent partly on visual fixation. 6. A few neurons showed tonic activity selectively before lever release and are thus considered to be related to the preparation of hand movements. 7. The activity related to breaking fixation (n = 33) occurred phasically if the monkey broke fixation, aborting the trial. 8. Activity related to reward (n = 104) was a phasic discharge that occurred before or after a reward of water was delivered. The activity was not simply related to a specific movement involved in the reward-obtaining behavior (eye, hand, or mouth movement). 9. Fixation-related activity (n = 72) was tonic activity continuing as long as the monkey attentively fixated a spot of light. It was dependent on reward expectancy in most cases. 10. The present results, together with those in the preceding papers, indicate that the activities of individual caudate neurons--sensory, motor, or cognitive--are dependent on specific contexts of learned behavior.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Penentu Jarak Tembak Berdasarkan Kerusakan Proyektil Timah Tanpa Jacket untuk Senjata Api Genggam Jenis Revolver S&W Kaliber .38 Spesial pada Target Tulang

2015 ◽  
Vol 17 (3) ◽  
pp. 135
Author(s):  
Sudibyo Sudibyo
Keyword(s):  
Target Location ◽  
Target Position ◽  
Real Data ◽  
Criminal Cases ◽  
Shape Coefficient ◽  
A Value ◽  
Technical Specifications ◽  
Table Data ◽  
Throw Distance ◽  
Test Firing

Abstract This study aims to predict the shooting range based on damage the type of lead a projectile without jacket caliber.38 special fired from handguns kinds brand Revolver S & W caliber .38 specials. Based on the phenomenon of criminal cases of abuse handguns types Revolver and the fact that real data it was found that 8% of the amount of lead projectiles without jacket as forensic evidence, the condition has broken the deformed moderate to severe.         The study was conducted at the Police Forensic Laboratory experimental method test-fired in the shooting box at short throw distance range of 0.5 to 6 meters , where the bone is positioned at the target position changes location every 0.5 meters, so the total number of shots is 12 times shot on 12 position target location, and finally obtained 12 variations of deformation projectile shot results.        Stages test firing conducted through three stages as follows: 1). Phase sample preparation equipment and materials firearms, bullets and target bone. 2). Phase shooting target accurately. 3). Stages of deformation measurements and weighing projectile, arranged in the form of table data.        Material samples of bullet used was the type of lead bullets without jacket caliber .38 special with technical specifications diameter of projectile 9.09 mm (real 9.05 mm), length of projectile 17.90 mm (real 18.61 mm), projectile material lead antimony, projectile weight of 10.25 grams, muzzle velocity (initial) 265 m / sec, rounded nose shape, coefficient of form C = 2, the ballistic coefficient i = 0,9 effective range or the distance accurately of 25 meters.        Material samples of bone were used as target is 1694 SR veal ribs with bone hardness values (87 ± 1.5) shore, is used for the calibration test firing, a human skull age adults (≥ 35 years) with a value of hardness (78 ± 6 ) shore, is used as the target subjects of research, human ribs (costal C-3 / C-6) adult (≥ 35 years) with a value of hardness (69 ± 19.5) shore, is used as the target subjects of research. Keywords : deformation; projectiles; bones

scholarly journals Modulations of foveal vision associated with microsaccade preparation

2020 ◽  
Vol 117 (20) ◽  
pp. 11178-11183
Author(s):  
Natalya Shelchkova ◽  
Martina Poletti
Keyword(s):  
Eye Movements ◽  
Visual Discrimination ◽  
Target Location ◽  
Onset Time ◽  
Spatial Vision ◽  
Saccade Target ◽  
Foveal Vision ◽  
Movement Onset ◽  
High Acuity ◽  
Gaze Position

It is known that attention shifts prior to a saccade to start processing the saccade target before it lands in the foveola, the high-resolution region of the retina. Yet, once the target is foveated, microsaccades, tiny saccades maintaining the fixated object within the fovea, continue to occur. What is the link between these eye movements and attention? There is growing evidence that these eye movements are associated with covert shifts of attention in the visual periphery, when the attended stimuli are presented far from the center of gaze. Yet, microsaccades are primarily used to explore complex foveal stimuli and to optimize fine spatial vision in the foveola, suggesting that the influences of microsaccades on attention may predominantly impact vision at this scale. To address this question we tracked gaze position with high precision and briefly presented high-acuity stimuli at predefined foveal locations right before microsaccade execution. Our results show that visual discrimination changes prior to microsaccade onset. An enhancement occurs at the microsaccade target location. This modulation is highly selective and it is coupled with a drastic impairment at the opposite foveal location, just a few arcminutes away. This effect is strongest when stimuli are presented closer to the eye movement onset time. These findings reveal that the link between attention and microsaccades is deeper than previously thought, exerting its strongest effects within the foveola. As a result, during fixation, foveal vision is constantly being reshaped both in space and in time with the occurrence of microsaccades.

A Neural Network Model of Flexible Spatial Updating

2004 ◽  
Vol 91 (4) ◽  
pp. 1608-1619 ◽  
Author(s):  
Robert L. White ◽  
Lawrence H. Snyder
Keyword(s):  
Neural Network ◽  
Reference Frame ◽  
Spatial Information ◽  
Target Location ◽  
Target Position ◽  
Spatial Location ◽  
Spatial Updating ◽  
Gaze Shift ◽  
Fixed Reference ◽  
Gaze Position

Neurons in many cortical areas involved in visuospatial processing represent remembered spatial information in retinotopic coordinates. During a gaze shift, the retinotopic representation of a target location that is fixed in the world (world-fixed reference frame) must be updated, whereas the representation of a target fixed relative to the center of gaze (gaze-fixed) must remain constant. To investigate how such computations might be performed, we trained a 3-layer recurrent neural network to store and update a spatial location based on a gaze perturbation signal, and to do so flexibly based on a contextual cue. The network produced an accurate readout of target position when cued to either reference frame, but was less precise when updating was performed. This output mimics the pattern of behavior seen in animals performing a similar task. We tested whether updating would preferentially use gaze position or gaze velocity signals, and found that the network strongly preferred velocity for updating world-fixed targets. Furthermore, we found that gaze position gain fields were not present when velocity signals were available for updating. These results have implications for how updating is performed in the brain.

Path optimization for navigation of a humanoid robot using hybridized fuzzy-genetic algorithm

2019 ◽  
Vol 7 (3) ◽  
pp. 112-119 ◽  
Author(s):  
Asita Kumar Rath ◽  
Dayal R. Parhi ◽  
Harish Chandra Das ◽  
Priyadarshi Biplab Kumar ◽  
Manoj Kumar Muni ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Fuzzy Logic ◽  
Path Planning ◽  
Humanoid Robot ◽  
Fuzzy Logic Controller ◽  
Target Location ◽  
Target Position ◽  
Content Type ◽  
Hybrid Controller ◽  
Fuzzy Genetic

Purpose Humanoids have become the center of attraction for many researchers dealing with robotics investigations by their ability to replace human efforts in critical interventions. As a result, navigation and path planning has emerged as one of the most promising area of research for humanoid models. In this paper, a fuzzy logic controller hybridized with genetic algorithm (GA) has been proposed for path planning of a humanoid robot to avoid obstacles present in a cluttered environment and reach the target location successfully. The paper aims to discuss these issues. Design/methodology/approach Here, sensor outputs for nearest obstacle distances and bearing angle of the humanoid are first fed as inputs to the fuzzy logic controller, and first turning angle (TA) is obtained as an intermediate output. In the second step, the first TA derived from the fuzzy logic controller is again supplied to the GA controller along with other inputs and second TA is obtained as the final output. The developed hybrid controller has been tested in a V-REP simulation platform, and the simulation results are verified in an experimental setup. Findings By implementation of the proposed hybrid controller, the humanoid has reached its defined target position successfully by avoiding the obstacles present in the arena both in simulation and experimental platforms. The results obtained from simulation and experimental platforms are compared in terms of path length and time taken with each other, and close agreements have been observed with minimal percentage of errors. Originality/value Humanoids are considered more efficient than their wheeled robotic forms by their ability to mimic human behavior. The current research deals with the development of a novel hybrid controller considering fuzzy logic and GA for navigational analysis of a humanoid robot. The developed control scheme has been tested in both simulation and real-time environments and proper agreements have been found between the results obtained from them. The proposed approach can also be applied to other humanoid forms and the technique can serve as a pioneer art in humanoid navigation.

scholarly journals The lateral intraparietal area codes the location of saccade targets and not the dimension of the saccades that will be made to acquire them

2013 ◽  
Vol 109 (10) ◽  
pp. 2596-2605 ◽  
Author(s):  
Sara C. Steenrod ◽  
Matthew H. Phillips ◽  
Michael E. Goldberg
Keyword(s):  
Target Location ◽  
Rhesus Macaques ◽  
Oculomotor System ◽  
Saccade Target ◽  
Delayed Response ◽  
Lateral Intraparietal Area ◽  
Saccadic Adaptation ◽  
End Point ◽  
Priority Map ◽  
Response Task

Activity in the lateral intraparietal area (LIP) represents a priority map that can be used to direct attention and guide eye movements. However, it is not known whether this activity represents the location of saccade targets or the actual eye movement made to acquire them. We recorded single neurons from rhesus macaques ( Macaca mulatta) while they performed memory-guided delayed saccades to characterize the response profiles of LIP cells. We then separated the saccade target from the saccade end point by saccadic adaptation, a method that induces a change in the gain of the oculomotor system. We plotted LIP activity for all three epochs of the memory-guided delayed-response task (visual, delay period, and presaccadic responses) as a function of target location and saccade end point. We found that under saccadic adaptation the response profile for all three epochs was unchanged as a function of target location. We conclude that neurons in LIP reliably represent the locations of saccade targets, not the amplitude of the saccade required to acquire those targets. Although LIP transmits target information to the motor system, that information represents the location of the target and not the amplitude of the saccade that the monkey will make.

scholarly journals Peri-saccadic mislocalization is not influenced by the predictability of the saccade target location

2011 ◽  
Vol 51 (1) ◽  
pp. 154-159 ◽  
Author(s):  
Femke Maij ◽  
Eli Brenner ◽  
Jeroen B.J. Smeets
Keyword(s):  
Target Location ◽  
Saccade Target
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