Mirror Location Research Articles

Testing Tc5 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and at Least in One Mirror Location

Testing Tc5 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and at Least in One Mirror Location

Testing Tc5 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and at Least in One Mirror Location (Null)

Testing Tc5 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and at Least in One Mirror Location (Null)

Testing Tc8 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But Exists in All Mirror Locations

Testing Tc8 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But Exists in All Mirror Locations

Testing Tc9 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But at Least One Exists in the Mirror Location (Null)

Testing Tc9 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But at Least One Exists in the Mirror Location (Null)

Testing Tc8 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But Exists in All Mirror Locations (Null)

Testing Tc8 Verify the Field Doc_Status When the Pdf File Does Not Exist in the Main Repository But Exists in All Mirror Locations (Null)

Testing Tc4 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and All Mirror Locations

Testing Tc4 Verify the Field Doc_Status When the Pdf File Exists in the Main Repository and All Mirror Locations

Blindsight after hemidecortication: Visual stimuli in blind hemifield influence anti-saccades directed there

Patients missing a cortical hemisphere, removed surgically at adulthood, cannot consciously see a visual probe stimulus (P) flashed in their blind contralesional, hemifield. Nevertheless, they have a low-level form of blindsight wherein P can affect the reaction time of a manual response to the appearance of a visual target in their seeing hemifield. This ability is thought to require the pathway from retina-to-ipsilesional superior colliculus (SC) to cortex of the remaining hemisphere (Leh et al., 2006a, 2006b, 2009). Apart from emitting ascending signals, the SC normally sends saccade commands to the brainstem, a function seemingly conserved after hemidecortication because such patients can generate voluntary and accurate saccades bilaterally (Herter and Guitton, 2004). However, they cannot generate goal-directed saccades to P in their blind hemifield. We hypothesized that, in hemidecorticate patients, P might influence anti-saccades directed to the blind hemifield, to the mirror location of a visual cue presented in the seeing hemifield. We used anti-saccades because our patients could scale their anti-saccade amplitudes approximately according to different cue locations, thereby permitting us to control the end point of their anti-saccades to the blind hemifield. We identified in these patients a new form of blindsight wherein unseen P, if properly timed at the anti-saccade goal location in the blind hemifield, reduced the reaction time and improved the accuracy of anti-saccades directed to that general location. We hypothesize that P in the blind hemifield produced low-level signals in the ipsilesional SC that, if appropriately located and timed relative to anti-saccade goal and onset, interacted with anti-saccade motor preparatory activity – produced by descending commands to SC from the remaining hemisphere – so as to modify both anti-saccade reaction time and end point. Our results support normally encoded and functionally useful, but subliminal, signals in the retina-to-ipsilesional SC-to-reticular pathway of hemidecorticate patients.

An analysis of gaze following to a hidden location in long-tailed macaques (Macaca fascicularis)

Gaze following, the ability to track the direction of another’s gaze, is thought to be an important component of human and animal social cognition. Several animal species attend to the gaze direction of others, but in Old World monkeys it remains unclear whether this behaviour is based on a simple co-orientation mechanism or on a more sophisticated perception of the other’s visual behaviour. The capacity to follow another’s gaze to a location hidden behind a physical obstacle has been argued to indicate refined skills in determining the exact direction of the other’s gaze (‘geometrical gaze following’) and a representation of space outside one’s own visual field. Human infants, great apes, new world monkeys, wolves (Canis lupus) and ravens (Corvus corax) have been shown to have this capacity. We investigated whether long-tailed macaques (Macaca fascicularis), an Old World monkey, follow conspecific gaze, indicated by head direction and visual orientation, to a hidden location. When a conspecific demonstrator gazed at a mirror hidden behind a barrier, subjects relocated to a position where they could see the mirror location and showed a trend, not statistically significant, to direct more focussed looks behind the barrier than in a situation where there was no conspicuous gaze cue by the demonstrator. The strength of this reaction was greatest in those individuals that looked most frequently at the demonstrator. Thus, long-tailed macaques may follow gaze to a hidden location, suggesting that they possess geometrical gaze following and represent space outside their own visual field. In addition, this capacity may be widespread across the animal kingdom.

Stimulation of the nucleus accumbens as behavioral reward in awake behaving monkeys

It has been known that monkeys will repeatedly press a bar for electrical stimulation in several different brain structures. We explored the possibility of using electrical stimulation in one such structure, the nucleus accumbens, as a substitute for liquid reward in animals performing a complex task, namely visual search. The animals had full access to water in the cage at all times on days when stimulation was used to motivate them. Electrical stimulation was delivered bilaterally at mirror locations in and around the accumbens, and the animals’ motivation to work for electrical stimulation was quantified by the number of trials they performed correctly per unit of time. Acute mapping revealed that stimulation over a large area successfully supported behavioral performance during the task. Performance improved with increasing currents until it reached an asymptotic, theoretically maximal level. Moreover, stimulation with chronically implanted electrodes showed that an animal's motivation to work for electrical stimulation was at least equivalent to, and often better than, when it worked for liquid reward while on water control. These results suggest that electrical stimulation in the accumbens is a viable method of reward in complex tasks. Because this method of reward does not necessitate control over water or food intake, it may offer an alternative to the traditional liquid or food rewards in monkeys, depending on the goals and requirements of the particular research project.

Spatiotemporal Properties of Neuron Response Suppression in Owl Monkey Primary Somatosensory Cortex When Stimuli Are Presented to Both Hands

Despite the lack of ipsilateral receptive fields (RFs) for neurons in the hand representation of area 3b of primary somatosensory cortex, interhemispheric interactions have been reported to varying degrees. We investigated spatiotemporal properties of these interactions to determine the following: response types, timing between stimuli to evoke the strongest bimanual interactions, topographical distribution of effects, and their dependence on similarity of stimulus locations on the two hands. We analyzed response magnitudes and latencies of single neurons and multineuron clusters recorded from 100-electrode arrays implanted in one hemisphere of each of two anesthetized owl monkeys. Skin indentations were delivered to the two hands simultaneously and asynchronously at mirror locations (matched sites on each hand) and nonmirror locations. Since multiple neurons were recorded simultaneously, stimuli on the contralateral hand could be within or outside of the classical RFs of any given neuron. For most neurons, stimulation on the ipsilateral hand suppressed responses to stimuli on the contralateral hand. Maximum suppression occurred when the ipsilateral stimulus was presented 100 ms before the contralateral stimulus onset (p < 0.0005). The longest stimulus onset delay tested (500 ms) allowed contralateral responses to recover to control levels (p = 0.428). Stimulation on mirror digits did not differ from stimulation on nonmirror locations (p = 1.000). These results indicate that interhemispheric interactions are common in area 3b, somewhat topographically diffuse, and maximal when the suppressing ipsilateral stimulus precedes the contralateral stimulus. Our findings point to a neurophysiological basis for "interference" effects found in human psychophysical studies of bimanual stimulation.

Neuromuscular recruitment related to stimulus presentation and task instruction during the anti-saccade task

The contextual control of movement requires the transformation of sensory information into appropriate actions, guided by task-appropriate rules. Previous conceptualizations of the sensorimotor transformations underlying anti-saccades (look away from a stimulus) have suggested that stimulus location is first registered and subsequently transformed into its mirror location before being relayed to the motor periphery. Here, by recording neck muscle activity in monkeys performing anti-saccades, we demonstrate that stimulus presentation induces a transient recruitment of the neck muscle synergy used to turn the head in the wrong direction, even though subjects subsequently looked away from the stimulus correctly. Such stimulus-driven aspects of recruitment developed essentially at reflexive latencies (∼60-70 ms after stimulus presentation), and persisted at modest eccentricities regardless of head-restraint. Prior to stimulus presentation, neck muscle activity also reflected whether the animals were preparing for an anti-saccade or a pro-saccade (look toward a stimulus). Neck muscle activity prior to erroneous anti-saccades also resembled that observed prior to pro-saccades. These results emphasize a parallel nature to the sensorimotor transformations underlying the anti-saccade task, suggesting that the top-down and bottom-up processes engaged in this task influence the motor periphery. The bottom-up aspects of neck muscle recruitment also fit within the context of recent results from the limb-movement literature, showing that stimulus-driven activation of muscle synergies may be a generalizing strategy in inertial-laden systems.

Effect of the Silver Mirror Location on the Luminance Intensity of Double Roughened GaN Light-Emitting Diodes

Four kinds of mirror systems were used to investigate the effect of the Ni thin film on the reflectivity of GaN light-emitting diodes after annealing at 200° for 1 h. Samples designated as "ITO/Ag " were ITO/Ag films without Ni layer. "ITO/Ni/Ag " and "ITO/Ag/Ni " were ITO/Ag films with a Ni layer either between the ITO and Ag films, or on the backside of Ag film. "ITO/Ni/Ag/Ni " were ITO/Ag films with Ni layers on both sides of Ag film. It was found that annealed-ITO/Ni/Ag/Ni had the highest reflectivity (96.3%). The thin Ni film could served as a diffusion barrier to retard the in-diffusion of Ag into ITO and the agglomeration of Ag. Therefore annealed-ITO/Ni/Ag/Ni had the highest reflectivity.

Environment of Aneurysms and Endovascular Considerations

Intracranial, saccular (berry) aneurysms arise from metamerically distributed, parent artery segments located within subarachnoid cisternal compartments, wherein they develop and eventually manifest themselves clinically. Aneurysms research has been traditionally dominated by luminal hemodynamics and underlying vascular geometry, applied extensively on in-vitro vascular models and on flow-sensitive neuroimaging techniques in-vivo to investigate aneurysm formation and growth, aneurysmal shapes and secondary lobulations (daughter sacs), aneurysmal size and propensity of aneurysms for rupture. Daily observation of aneurysms cases shows an almost infinite variability of aneurysm shapes and sizes across all locations, characteristic (repeatedly observable) shapes of aneurysms at certain locations, usually different shapes and sizes of aneurysms at mirror locations, rare or absent occurrence of surface irregularities and daughter formation at certain aneurysm locations as opposed to other aneurysm locations with frequent occurrence of surface irregularities and of mono- or multilobular daughter formation, great variability in the orientation of the main axis of the fundus of aneurysms arising at the same location, great variability of daughter morphology and of indentations on the aneurysmal sac surface as well as a variable evolution of aneurysmal shapes and sizes over time. Attempts at explaining these observations exclusively with the underlying vascular geometry and intrinsic luminal hemodynamics proved inadequate, prompting the consideration of mural factors of aneurysmal pathobiology (i.e. segmental vulnerability and aneurysmal vasculopathy) as well as of extrinsic factors related to the perianeurysmal subarachnoid space in the investigation of aneurysmal morphology, phenomenology and dynamic behavior. In the past five years we investigated the anatomy of the basal subarachnoid space, its compartmentalization into distinct apposing cisterns intercommunicating through characteristic entry and exit sites (openings), the subcompartmentalization of cisterns by characteristic intracisternal arachnoid membranes of loose network, dense network or true membranous texture and the intrinsic architectonic organization of the intracisternal compartmental and subcompartmental innervated trabecula, which stabilize the position of cisternal arterial segments in relation to the cisternal walls, the position and configuration of the cisternal arterial segments and the position and configuration of branches arising from the main arterial segments, by correlating anatomic dissection studies with advanced 3 Tesla-MR-cisternographic techniques performed in-vivo. In a second step, we correlated 3D-CTA, 3D-MRA, 3D-DSA visualizations as well as intraoperative demonstrations of unruptured and of ruptured aneurysms with the corresponding anatomic disposition of the individual subarachnoid cisternal subcompartment occupied by the aneurysm. Here we show, that 1) the orientation, thickness, texture and strength of intracisternal arachnoid membranes determine the orientation of the main fundus axis mostly irrespective of the underlying vascular geometry pattern and contribute to the basic shape of aneurysms, 2) the architectonic arrangement of intracisternal perianeurysmal trabecula of the various types being in contact with the aneurysmal adventitia influences the aneurysmal configuration and the direction of intracisternal aneurysms extension, 3) characteristic tough diagonal or transverse arachnoid bands in certain cisterns, such as the lateral Sylvian, the carotid, the interpeduncular and premedullary cisterns, create marked short, long or circumferential extrinsic indentations on the outer aneurysm wall thus influencing the shape of the aneurysmal fundus and the number of aneurysmal lobes as well as the configuration and number of bulging parts, secondary lobulations and blebs, 4) in the early acute phase of SAH, contraction of innervated trabecula inserting on the aneurysmal adventitia elicited by the exiting jet and distortion/stretching of trabecula in contact with the aneurysm wall caused by the intertrabecularly deposited blood clots may deform or strangulate the fundus of the ruptured aneurysm thus altering temporarily its shape and decreasing its size. Endovascular treatment performed during this phase will be based on selection of smaller coils. Later relaxation of contracted of stretched trabecula will re-establish the original size and shape of the coiled aneurysms. This phenomenon may explain the observed and reported significantly higher recanalization rate of aneurysms treated in the early acute phase of SAH as compared with the recanalization rates of aneurysms treated later or in the unruptured stage. We conclude, that the compartmentalized perianeurysmal subarachnoid space and its complex intrinsic arachnoid-membranous and trabecular architectonic organization influence significantly the morphology and phenomenology of unruptured and ruptured aneurysms as well as the dynamic aneurysms behavior observed during the acute phase of SAH. We recommend consideration of these factors in the indication for, timing of and technique selection for the endovascular treatment of unruptured and ruptured aneurysms.

Effect of the Silver Mirror Location on the Luminance Intensity of Double Roughened GaN Light-Emitting Diodes

not Available.

Microstimulation of monkey dorsolateral prefrontal cortex impairs antisaccade performance

The dorsolateral prefrontal cortex (DLPFC) has been implicated in various cognitive functions, including response suppression. This function is frequently probed with the antisaccade task, which requires suppression of the automatic tendency to look toward a flashed peripheral stimulus (prosaccade), and instead generate a voluntary saccade to the mirror location. To test whether activity in the DLPFC is causally linked to antisaccade performance, we applied electrical microstimulation to sites in the DLPFC of two monkeys, while they performed randomly interleaved pro- and antisaccade trials. Microstimulation resulted in significantly longer saccadic reaction times for ipsilaterally directed prosaccades and antisaccades, and increased the error rate on ipsilateral antisaccade trials. These findings provide causal evidence that activity in the DLPFC influences saccadic eye movements.

On the limited role of target onset in the gap task: Support for the motor-preparation hypothesis

Saccade latency is reduced when the fixation stimulus is removed shortly before a saccade target appears (gap task) as compared to when the fixation stimulus remains present (overlap task). To test the assumption that this gap effect benefits from advanced motor preparation (M. Paré & D. P. Munoz, 1996), we manipulated target onset independently of the signal to launch a saccade (peripheral offset at the mirror location). In Experiment 1, we showed that, when the target appears at one of only two possible locations, target onset strongly improves performance (lower latency, higher accuracy) in the overlap task but not in the gap task. In Experiment 2, we found that the lack of an effect of target onset in the gap task was not due to inhibition of a reflexive response to the transient associated with the offset (go signal) in our task. In Experiment 3, we manipulated target onset and target uncertainty (two, four, or eight potential target locations) in gap and overlap tasks. As target uncertainty increased, the gap effect decreased, and the effect of target onset on saccade latency in the gap condition became greater. Overall, our results suggest, in line with the motor-preparation hypothesis, that saccade metrics in a gap task are computed before the target is actually displayed and that advanced motor preparation is enhanced when the location of the target is predictable. Analyses of anticipations and regular-latency errors corroborated this view.

Visual vector inversion in the posterior parietal cortex

In the antisaccade task, a saccade must be triggered towards the mirror location of a visual target. The neural basis required for this visual vector inversion remains unclear, although neuronal activities reflecting this process have been recorded in the monkey lateral intraparietal area. We examined a patient with a small, right-sided, posterior parietal stroke who complained of difficulty in manipulating visual information. Antisaccades were markedly hypometric rightwards but normal leftwards. Largely unaffected performances in other saccade tasks revealed that visual and motor processing were not significantly affected. Antisaccade inaccuracy could therefore be ascribed to the impairment of visual vector inversion, a processing specifically required in this task. These findings provide the first evidence in humans that visual vector inversion could be an intrinsic property of the posterior parietal cortex.

Neurovascular changes after four-layer compression bandaging in people with chronic venous leg ulcers

Venous leg ulcers represent a major clinical problem, with poor rates of healing. Ideal treatment is compression bandaging. The effect of compression on neurovascular tissues involved in wound repair is unclear. This study aims to assess the effect of four-layer compression therapy (40 mmHg) on neurovascular function and wound healing in people with chronic venous leg ulcers--15 people (55 years or older) with venous leg ulcers for more than six weeks. Basal microvascular perfusion measurement (MPM), oxygen tension (tcpO2) measured at sensor temperatures of 39 degrees C and 44 degrees C and sensory nerve function using electrical cutaneous perception thresholds (ECPT) at 5, 250 and 2000 Hz (corresponding to C, Adelta and Abeta fibres) were assessed adjacent to the ulcer site, and at a mirror location on the non-ulcerated limb. Testing was undertaken before and after therapy for 5-12 weeks of four-layer compression bandaging. There was significant improvement in tcpO2 at 44 degrees C and ECPT at 2000 Hz (P < 0.05) compared with pre-intervention. Changes in basal MPM, tcpO2 at 39 degrees C and ECPT at 5 and 250 Hz after compression therapy did not reach statistical significance. Four-layer compression bandaging in people with venous leg ulcers improved some components of neurovascularture in people with chronic venous leg ulcers. Whether this improvement has contributed to wound healing in this study requires further investigation.

Effect of the Silver Mirror Location on the Luminance Intensity of Double-Roughened GaN Light-Emitting Diodes

Three kinds of GaN light-emitting diodes (LEDs) were used to investigate the effect of the silver (Ag) mirror location on the performance of LEDs. Samples designated as PR-LED were LEDs with roughened p-GaN surface. and DRSM-LED were LEDs with double-roughened (p-GaN and undoped-GaN) surfaces and a Ag mirror system either at the undoped-GaN/sapphire interface or on the back side of sapphire substrate. It was found that the light intensity of DRM-LED was 235.8 mcd, which was 3.05 times higher than that of the PR-LED, and 1.45 times higher than that of the DRSM-LED.

The mirror antisaccade task: direction–amplitude interaction and spatial accuracy characteristics

In this study we examined the performance of human subjects in three oculomotor tasks: a visually guided saccade task (VST), a simple antisaccade task (SAT) and a mirror antisaccade task (MAT). The stimulus presentation was identical for all three tasks, and the differentiation of the tasks was based on the instruction given to the subjects. Subjects were instructed to either look at a visually presented target location (visually triggered saccade task), or to look at the opposite direction of the visually presented target (simple antisaccade task) or finally to look at the mirror location opposite to the location of the visually presented target (mirror antisaccade task). The loading of the simple antisaccade task with the addition of the amplitude requirement did not affect the percentage of directional errors but slowed down the onset of antisaccade execution by 19 ms. The amplitude of the directionally correct antisaccade in the mirror antisaccade task showed a significant distortion of the true mirror target location. This dysmetria followed the same qualitative pattern to that observed for the visually guided saccades, i.e., a near-target hypermetria together with a far-target hypometria, but both these features were exaggerated in the mirror antisaccade task. This distorted amplitude modulation of mirror antisaccade amplitude was completely lost in corrected antisaccades that followed a directional error.