Imagery Performance Research Articles

Vibration-free stirling cryocooler for high definition microscopy

The normal operation of high definition Scanning Electronic and Helium Ion microscope tools often relies on maintaining particular components at cryogenic temperatures. This has traditionally been accomplished by using liquid coolants such as liquid Nitrogen. This inherently limits the useful temperature range to above 77 K, produces various operational hazards and typically involves elevated ownership costs, inconvenient logistics and maintenance. Mechanical coolers, over-performing the above traditional method and capable of delivering required (even below 77 K) cooling to the above cooled components, have been well-known elsewhere for many years, but their typical drawbacks, such as high purchasing cost, cooler size, low reliability and high power consumption have so far prevented their wide-spreading. Additional critical drawback is inevitable degradation of imagery performance originated from the wideband vibration export as typical for the operation of the mechanical cooler incorporating numerous movable components. Recent advances in the development of reliable, compact, reasonably priced and dynamically quiet linear cryogenic coolers gave rise to so-called “dry cooling” technologies aimed at eventually replacing the traditional use of outdated liquid Nitrogen cooling facilities. Although much improved these newer cryogenic coolers still produce relatively high vibration export which makes them incompatible with modern high definition microscopy tools. This has motivated further research activity towards developing a vibration free closed-cycle mechanical cryocooler. The authors have successfully adapted the standard low vibration Stirling cryogenic refrigerator (Ricor model K535-LV) delivering 5 W@40 K heat lift for use in vibration-sensitive high definition microscopy. This has been achieved by using passive mechanical counterbalancing of the main portion of the low frequency vibration export in combination with an active feed-forward multi-axes suppression of the residual wideband vibration, thermo-conductive vibration isolation struts and soft vibration mounts. The attainable performance of the resulting vibration free linear Stirling cryocooler (Ricor model K535-ULV) is evaluated through a full-scale experimentation.

Age and gender-related differences in the temporal congruence development between motor imagery and motor performance

Temporal congruence between motor imagery and motor performance was evaluated in 30 elementary school children (7 and 8-year-olds) and 61 middle school children (11 and 12-year-olds), using the “Harre's Chase” obstacle-course [Harre, D. (1976). Trainingslehre. Berlin: Sportverlag]. It is made of successive elementary actions including running, rolling forward, changing direction, jumping and crawling. The children were requested to perform the obstacle-course both actually and mentally. Results showed that motor imagery duration was closer to that of actual execution in the middle school children group, as compared to elementary school children. We also found a gender difference, boys being more able than girls to reach the temporal congruency between imagined and physical times. Developmental factors, as well as gender differences in socio-cognitive traits, are discussed as the main factors explaining the development of the isochrony between actual and imagined movements.

Abstract: P484 ANALYSIS OF NEOINTIMAL HYPERPLASIA AFTER IMPLANTATION OF A MONOCLONAL ANTIBODY ELUTING STENT

The recent northward expansion of Southern Pine Beetle (SPB) outbreaks associated with warming winters has caused extensive tree mortality in temperate pine forests, significantly affecting forest dynamics, structure, and functioning. Spatially-explicit early warning and detection of SPB-induced tree mortality is critical for timely and sustainable forest management practices. The unique contributions of remote sensing technologies to mapping the location, extent, and severity of beetle outbreaks, as well as assisting in analyzing the potential drivers for outbreak predictions, have been well recognized. However, little is known about the performance of moderate resolution satellite multispectral imagery for early warning and detection of SPB-induced tree mortality. Thus, we conducted this study, as the first attempt, to capture the spatial-temporal patterns of SPB infestation severity at the regional scale and to understand the underlying environmental drivers in a spatially-explicit manner. First, we explored the spectral signatures of SPB-killed trees based on 30-m plot measurements and Landsat-8 imagery. Then, to improve detection accuracy for areas with low-moderate SPB infestation severity, we added spectral-temporal anomaly information in the form of a linear trend of the spectral index trajectory to a previously developed approach. The best overall accuracy increased from 84.7% to 90.1% and the best Macro F1 value increased from 0.832 to 0.900. Next, we compared the performances of spectral indices in mapping SPB infestation severity (i.e., % red stage within the 30-m grid cell). The results showed that the combination of Normalized Difference Moisture Index and Tasseled Cap Greenness had the best performance for mapping SPB infestation severity (2016: R2 = 0.754; RSME = 15.7; 2017: R2 = 0.787; RSME = 12.4). Finally, we found that climatic and landscape variables can explain the detected patterns of SPB infestation from 2014 to 2017 in our study area (R2 = 0.751; RSME = 9.67), providing valuable insights on possible predictors for early warning of SPB infestation. Specifically, in our study area, winter dew point temperature was found to be one of the most important predictors, followed by SPB infestation locations in the previous year, canopy cover of host species, elevation, and slope. In the context of continued global warming, our study not only provides a novel framework for efficient, spatially-explicit, and quantitative measurements of forest damage induced by SPB infestation over large scales, but also uncovers opportunities to predict future SPB outbreaks and take precautions against it.

Facilitation of motor imagery through movement-related cueing

In the past few years, the use of motor imagery as an adjunct to other forms of training has been studied extensively. However, very little attention has been paid to how imagery could be used to greatest effect. It is well known that the provision of external cues has a beneficial effect on motor skill acquisition and performance during physical practice. Since physical execution and mental imagery share several common mechanisms, we hypothesized that motor imagery might be affected by external cues in a similar way. To examine this, we compared the motor imagery performance of three groups of 15 healthy participants who either physically performed or imagined performing a goal-directed cyclical wrist movement in the presence or the absence of visual and/or auditory external cues. As outcome measures, the participants' imagery vividness scores and eye movements were measured during all conditions. We found that visual movement-related cues improved the spatial accuracy of the participants' eye movements during imagery, while auditory cues specifically enhanced their temporal accuracy. Furthermore, both types of cues significantly improved the participants' imagery vividness. These findings indicate that subjects may imagine a movement in a better way when provided with external movement-related stimuli, which may possibly be useful with regard to the efficiency of mental practice in (clinical) training protocols.

Effects of action on children’s and adults’ mental imagery

The aim of this study was to investigate whether and which aspects of a concurrent motor activity can facilitate children’s and adults’ performance in a dynamic imagery task. Children (5-, 7-, and 9-year-olds) and adults were asked to tilt empty glasses, filled with varied amounts of imaginary water, so that the imagined water would reach the rim. Results showed that in a manual tilting task where glasses could be tilted actively with visual feedback, even 5-year-olds performed well. However, in a blind tilting task and in a static judgment task, all age groups showed markedly lower performance. This implies that visual movement information facilitates imagery. In a task where the tilting movement was visible but regulated by means of an on-and-off remote control, a clear age trend was found, indicating that active motor control and motor feedback are particularly important in imagery performance of younger children.

Suppression of cryocooler-induced microphonics in infrared imagers

Sophisticated portable infrared imagers developed for surveillance, reconnaissance, targeting and navigation play a vital role in the modern tactics used for carrying out military and antiterrorist operations. Their superior performance relies on novel optronic technologies and maintaining the infrared focal plane arrays at cryogenic temperatures using close cycle mechanical Stirling cryogenic coolers. Such coolers are well known sources of high-frequency interference contaminating the image signal and causing essential degradation in the overall imagery performance. This phenomenon is generally referred to as microphonics, which mostly manifests itself at the resonant frequencies of sensitive mechanical components of infrared packages. The ruggedizing of these components involves stiffening and dampening which are, evidently, not the best solutions to implement inside, say, an evacuated envelope, where the issues of added heat load, thermal mass, ageing, vacuum contamination due to outgassing are of the primary concern. The paper examines the idea of using externally mounted wideband dynamic absorbers for suppressing the above resonant responses and associated microphonic noise. The suggested analytical model relies on a set of complex frequency response functions experimentally captured on the original infrared package. The optimised dynamic absorber yields about a tenfold suppression of the resonant responses and a threefold attenuation of the overall RMS level of microphonic noise. The results of the analytical prediction are in fair agreement with experimental data.

Synthesis of snubber's spectral characteristics for vibration protection of sensitive components in airborne gyrostabilized electro-optic payloads

Low-frequency vibration isolation of airborne gyrostabilized electro-optic payloads is the ultimate and proven solution aimed at improving their imagery performance, primarily during a quiet cruise flight. This portion of the airborne mission is characterized by rather moderate environmental conditions, under which vibration mounts operate in a linear working range within the predefined working rattle space, which eventually results in better performances. Compliant snubbers are indispensable emergency components in such vibration protection arrangements primarily needed during exposure to the extreme environmental conditions typical of the relatively short periods of airborne missions such as take-off, landing, weapon application, etc. Their primary objective is to protect these soft vibration mounts and prevent their bottoming and disintegration without any impulsive accelerations that compromise the integrity of the payload frame and fragile internal components mounted upon it. The optimal approach for designing a snubbed vibration isolator, delivering a fail-safe environment for both the payload frame and critical components subjected to tight constraints imposed on the size, weight, and price does not seem to exist. It is intended to devise the optimal design approach and to demonstrate its application on low-frequency vibration mounted electro-optic payload comprising the vibration sensitive integrated dewar-detector-cooler assembly.

Acquisition and processing of backscatter data for habitat mapping – Comparison of multibeam and sidescan systems

Often marine habitat surveys use multibeam bathymetry systems to model the seafloor. This describes the morphology but not the terrain lithology or substrate. Backscatter imagery helps the interpreter to better classify the physical environment that may support a particular biological community. In this contribution, the acquisition performance of both multibeam and sidescan sonar backscatter imagery are contrasted and examples shown. The logistical factors affecting the two systems during surveying are discussed and data from both systems compared. Choice of systems for habitat mapping is discussed. A relative cost analysis of the various survey systems is presented with varying resolution and coverage. The size and shape of the footprint, and thus resolution, is variable dependant on many factors, including ship speed, data processing and sampling. The resolution and formation of imagery is important, but high sampling rates are shown not to be a complete solution as over-sampling can present a false impression of high resolution. However, it is suggested that backscatter imagery should have least 7 bit sensitivity to aid visual and digital inspection. Habitat mapping examples are shown using multibeam backscatter and sidescan sonar, where the processing has been optimised for backscatter imagery. A key question is how much of high resolution bathymetry data is essential for habitat mapping, and whether backscatter imagery can provide more of the information required at a higher resolution than a bathymetric morphology map.

Verbal overshadowing in visual imagery is due to recoding interference

Verbal overshadowing reflects the impairment in memory performance following verbalisation of nonverbal stimuli. A recent debate has concerned the mechanisms that govern the verbal overshadowing phenomenon in different domains. In the present paper, we explore the dynamics of verbal overshadowing in the imagery domain, by manipulating the presence of visual and verbal cues at retrieval. In particular, the role of self-generated names as retrieval cues was investigated to contrast the Transfer-Inappropriate Processing (TIP) and the Recoding Interference (RI) accounts of verbal overshadowing. Results from three experiments revealed that verbal overshadowing in visual imagery can be attenuated by any cues (visual or verbal) that trigger the activation of featural representations necessary to complete an image transformation task. Counterintuitively, like visual cues, self-generated common nouns, but not proper nouns or nonwords, significantly improved visual imagery performance, hence supporting a recoding interference account of VO.

Correction of Attitude Fluctuation of Terra Spacecraft Using ASTER/SWIR Imagery With Parallax Observation

Accurate attitude estimation of spacecrafts is the main requirement to provide good geometric performance of remote-sensing imagery. The Advanced Spaceborne Thermal Emission and Reflection Radiometer/short-wave-infrared subsystem has six linear-array sensors arranged in parallel, and each line scans the same ground target with a time interval of 356.238 ms between neighboring bands. The registration performance between bands becomes worse when attitude fluctuation occurs during a time lag between observations. Since the time resolution of the line scan is higher than that of the attitude information provided from the satellite, attitude data are estimated with a high frequency. We succeeded in correcting the image-registration error using the revised attitude information. As a result, the image distortion of 0.2 pixels caused by spacecraft-attitude jitter is reduced to less than 0.08 pixels, showing that band-to-band registration errors of a sensor with parallax observation are available to improve the image distortion caused by attitude fluctuation.

Mental rotation of congenitally absent hands

We compared motor imagery performance of normally limbed individuals with that of individuals with one or both hands missing since birth (i.e., hand amelia). To this aim, 14 unilaterally and 2 bilaterally amelic participants performed a task requiring the classification of hands depicted in different degrees of rotation as either a left or a right hand. On the same task, 24 normally limbed participants recapitulated previously reported effects; that is, that the hand motor dominance and, more generally, a lifelong use of hands are important determinants of left-right decisions. Unilaterally amelic participants responded slower to hands corresponding to their absent, compared with their existing, hand. Moreover, left and right hand amelic participants showed prolonged reaction times to hands (whether left or right) depicted in unnatural orientations compared with natural orientations. Among the bilateral amelics, the individual with phantom sensations, but not the one without, showed similar differentiation. These findings demonstrate that the visual recognition of a hand never physically developed is prolonged, but still modulated by different rotation angles. They are further compatible with the view that phantom limbs in hand amelia may constrain motor imagery as much as do amputation phantoms.

REPRODUCIBILITY OF TRIAL-BASED FUNCTIONAL MRI ON MOTOR IMAGERY

The investigation of the reproducibility in functional MRI (fMRI) is an important step in the quantification and analysis of paradigm-related brain activation. This article reports on reproducibility of cortical activation characterized by repeated fMRI runs (10 times) during the performance of a motor imagery and a passive auditory stimulation as a control task. Two parameters, the size of activation and BOLD signal contrast, were measured from regions-of-interest for 10 subjects across different threshold conditions. The variability of these parameters was normalized with respect to the mean obtained from 10 runs, and represented as the intrasession variability. It was found that the variability was significantly lower in the measurement of BOLD signal contrast as compared to the measurement of the size of activation. The variability of the activation volume measurement was greater in the motor imagery task than in the auditory tasks across all thresholds. This task-dependent difference was not apparent from the measurement of the BOLD signal contrast. The presence of threshold dependence in the variability measurement was also examined, but no such dependency was found. The results suggest that a measurement of BOLD signal itself is a more reliable indicator of paradigm-related brain activation during repeated fMRI scans.

The Influence of Physical and Cognitive Activities on Simple and Complex Cognitive Tasks in Older Adults

This study examined the relative benefits of physical and cognitive activities on simple and complex cognitive task performance in older adults. Participants were 24 young (18–27 years), 24 young-old (65–74 years), 24 middle-old (75–84 years), and 24 old-old (85–92 years) adults. Participants recorded the amount of time engaged in physically and cognitively stimulating activities as well as the effort exerted during these activities. They also completed a simple and complex version of a visual imagery task. Age-related declines were evident in activity and imagery performance. Both physical and cognitive activities were related to better cognitive performance. Furthermore, cognitive activity was a stronger predictor than physical activity of the complex, but not the simple task. However, within each activity domain there were no significant differences between performance on the simple and complex task. These results suggest that physical and cognitive stimulation are useful in protecting against cognitive decline with age, but that they may exert their influence via different paths.

The influence of expertise level on the visuo-spatial ability: differences between experts and novices in imagery and drawing abilities

This study analyzed the spatial skills of experts in visual art. Empirical evidences suggested that drawing training involves changes in perceptual, spatial and imagery abilities of artists. Several studies investigated cognitive abilities of individuals that carry on artistic activities comparing them with non-artists. These studies provided results indicating artists advantage in imagery processing. Studies on non-experts samples analyzed the relationship between imagery and artistic involvement and the contribution of cognitive and motor components in drawing ability. This study will explore imagery and drawing abilities of expert artists, adding to commonly used imagery performance tasks (objective tests of mental imagery), self-reports of imagery and various drawing tasks. We considered imagery ability as a multifactorial component and the drawing ability as dependent on both cognitive-perceptual and motor skills. The results showed that: (a) there were no significant differences between artists and non-artists on self-reported imagery vividness measures; (b) on imagery performance and drawing tasks the artists’ performance was undoubtedly superior compared to non-artists performance; (c) in the drawing conditions, involving different perceptual and motor processes, experts equally showed a better performance compared to non-expert subjects. These results were interpreted as an overall advantage in perceptual and imagery abilities for visual art experts, both on tasks involving graphic rendering (drawing tasks) and on tasks where it was not requested (imagery tasks). Furthermore, artists’ abilities were interpreted as not limited to a cognitive domain, but different cognitive-motor and essentially motor skills were equally relevant in expert’s drawing.

Neural Encoding Correlates of High and Low Verbal Memory Performance

Neuroimaging studies have indicated involvement of left prefrontal cortex and temporal areas in verbal memory processes. The current study used event-related functional neuroimaging to compare encoding of subsequently recalled and not recalled words in high and low memory performers. Fifteen healthy volunteers were given lists of words to learn with immediate recall and to read as a control condition. High performers reported to have visualized the words whereas low performers used a rehearsal strategy. Compared to reading, unsuccessful encoding was associated with thalamic and left premotor area (BA 6) activity. Comparing successful with unsuccessful learning yielded widespread activity of the left prefrontal and posterior temporal gyrus as well as the left superior parietal lobe in the whole group. Low performers showed activation of the left premotor area throughout learning and additionally of the left middle temporal and parahippocampal gyrus during successful encoding. High performers showed increased activation in the extrastriate cortex throughout learning and additionally in the left parietal post- and paracentral areas as well as in the right precuneus during successful encoding. The results suggest that high verbal memory performance is the result of spatiovisual activation concomitant to imagery and low performance of hippocampal and motor activation, the latter being associated with rehearsal, with a common memory circuit subserving both groups.

Task-Specific Knowledge of the Law of Pendulum Motion in Children and Adults

The present experiment investigated children and adults’ knowledge of the pendulum law under different task conditions. The question asked was whether adults and fourth-graders knew that the period of a pendulum is a function of pendulum length but is independent of its mass. The task was to judge the period on a rating scale (judgment task), to imagine the swinging pendulum and indicate the corresponding time interval (imagery task), or to adjust the period of a dynamically presented pendulum (perception task). Normative consideration of pendulum length as the only relevant factor was primarily found in the perception task and, for adults, in the imagery task, whereas in the judgment task, children and adults frequently considered the irrelevant dimension of mass. Most children showed poor imagery performance. Preceding adjustment (perception task) and rating (judgment task) had no differential influence on subsequent imagery performance.

Accuracy assessment of QuickBird stereo imagery

AbstractThe Geographical Survey Institute of Japan has recently carried out an evaluation of the metric performance of QuickBird stereo satellite imagery. This paper describes the accuracy assessment of the sensor orientation and geopositioning phases of the study, the aim of which was twofold. First, it was desired to confirm the metric potential of QuickBird imagery for 1:25 000 scale topographic mapping. Second, a determination was to be made of the accuracy attainable from the Basic image product. The techniques of rational functions and affine bundle adjustment were employed, the former with bias compensation. The results obtained both reassert the high precision of the rational functions approach and cast doubt upon the applicability of the 3D affine model for accurate geopositioning from QuickBird imagery.

Fantasy proneness, mental imagery and reality monitoring

Individual differences in fantasy proneness and vividness of mental imagery have been suggested to be related to source memory confusions. To test this hypothesis, two groups scoring either high or low on a measure of fantasy proneness (selected from a group of 231 subjects) were compared on measures of self report vividness of mental imagery, objective imagery ability and reality monitoring performance. The two groups differed significantly on ratings of imagery vividness (p<0.01), but not on the imagery performance tasks, nor on reality monitoring performance. Our results indicate that, although fantasy proneness is associated with experiences of vivid mental imagery, it does not necessarily lead to reality monitoring errors.

The use of mental imagery in the simulated employment interview situation

In this study, interviewees in the training group were instructed to use mental imagery techniques in a simulated employment interview. Results indicated that the subjects who used mental imagery had higher performance in the interview and lower perceived stress than the subjects who did not use mental imagery. Mental imagery did not have a significant effect upon perceptions of self‐efficacy. Mental imagery ability had a positive effect on perceived usefulness of mental imagery while controllability and vividness did not. Subjects did indicate positive perceptions of the mental imagery intervention and a willingness to use mental imagery again in the future. The personality variable, “conscientiousness”, had a significant effect in the mental imagery performance relationship.

Functional properties of brain areas associated with motor execution and imagery.

Imagining motor acts is a cognitive task that engages parts of the executive motor system. While motor imagery has been intensively studied using neuroimaging techniques, most studies lack behavioral observations. Here, we used functional MRI to compare the functional neuroanatomy of motor execution and imagery using a task that objectively assesses imagery performance. With surface electromyographic monitoring within a scanner, 10 healthy subjects performed sequential finger-tapping movements according to visually presented number stimuli in either a movement or an imagery mode of performance. We also examined effects of varied and fixed stimulus types that differ in stimulus dependency of the task. Statistical parametric mapping revealed movement-predominant activity, imagery-predominant activity, and activity common to both movement and imagery modes of performance (movement-and-imagery activity). The movement-predominant activity included the primary sensory and motor areas, parietal operculum, and anterior cerebellum that had little imagery-related activity (-0.1 ~ 0.1%), and the caudal premotor areas and area 5 that had mild-to-moderate imagery-related activity (0.2 ~ 0.7%). Many frontoparietal areas and posterior cerebellum demonstrated movement-and-imagery activity. Imagery-predominant areas included the precentral sulcus at the level of middle frontal gyrus and the posterior superior parietal cortex/precuneus. Moreover, activity of the superior precentral sulcus and intraparietal sulcus areas, predominantly on the left, was associated with accuracy of the imagery task performance. Activity of the inferior precentral sulcus (area 6/44) showed stimulus-type effect particularly for the imagery mode. A time-course analysis of activity suggested a functional gradient, which was characterized by a more "executive" or more "imaginative" property in many areas related to movement and/or imagery. The results from the present study provide new insights into the functional neuroanatomy of motor imagery, including the effects of imagery performance and stimulus-dependency on brain activity.