Visual percepts modify iconic memory in humans.

Our visual system briefly retains a trace of a stimulus after it disappears. This phenomenon is known as iconic memory and its contents are thought to be temporally integrated with subsequent visual inputs to produce a single composite representation. However, there is little consensus on the temporal integration between iconic memory and subsequent visual inputs. Here, we show that iconic memory revises its contents depending upon the configuration of the newly produced single representation with particular temporal characteristics. The Poggendorff illusion, in which two collinear line segments are perceived as non-collinear by an intervening rectangle, was observed when the rectangle was presented during a period spanning from 50 ms before to 200 ms after the presentation of the line segments. The illusion was most prominent when the rectangle was presented approximately 100 to 150 ms after the line segments. Furthermore, the illusion was observed at the center of a moving object, but only when the line segments were presented before the rectangle. These results indicate that the contents of iconic memory are susceptible to the modulatory influence of subsequent visual inputs before being translated into conscious perception in a time-locked manner both in retinotopic and non-retinotopic, object-centered frames of reference.

Size-contrast illusion induced by unconscious context.

The present study examined whether the Ebbinghaus illusion can be induced by surrounding contexts that are suppressed from conscious perception. We employed continuous flash suppression to render the contextual stimuli invisible. The surrounding contexts were presented to one eye and the masking stimulus was presented to the other eye, followed by the presentation of the two center test stimuli to both eyes. The illusory size effect was observed even when the inducers were rendered invisible, although the effect was weak-approximately one third the strength of that induced by visible contexts. The effects induced by both visible and invisible contexts decayed with equal speed as the interstimulus interval between the inducer and test stimuli increased. Moreover, interocular transfer of illusory size effect did not occur when the inducers were suppressed from awareness. These results suggest that the size-contrast effect in the Ebbinghaus illusion is mediated in V1, and the monocular pathway in V1 is involved in the unconscious effect.

Neural mechanisms underlying sound-induced visual motion perception: An fMRI study.

Studies of crossmodal interactions in motion perception have reported activation in several brain areas, including those related to motion processing and/or sensory association, in response to multimodal (e.g., visual and auditory) stimuli that were both in motion. Recent studies have demonstrated that sounds can trigger illusory visual apparent motion to static visual stimuli (sound-induced visual motion: SIVM): A visual stimulus blinking at a fixed location is perceived to be moving laterally when an alternating left-right sound is also present. Here, we investigated brain activity related to the perception of SIVM using a 7T functional magnetic resonance imaging technique. Specifically, we focused on the patterns of neural activities in SIVM and visually induced visual apparent motion (VIVM). We observed shared activations in the middle occipital area (V5/hMT), which is thought to be involved in visual motion processing, for SIVM and VIVM. Moreover, as compared to VIVM, SIVM resulted in greater activation in the superior temporal area and dominant functional connectivity between the V5/hMT area and the areas related to auditory and crossmodal motion processing. These findings indicate that similar but partially different neural mechanisms could be involved in auditory-induced and visually-induced motion perception, and neural signals in auditory, visual, and, crossmodal motion processing areas closely and directly interact in the perception of SIVM.

The reference frame of the tilt aftereffect measured by differential Pavlovian conditioning.

We used a differential Pavlovian conditioning paradigm to measure tilt aftereffect (TAE) strength. Gabor patches, rotated clockwise and anticlockwise, were used as conditioned stimuli (CSs), one of which (CS+) was followed by the unconditioned stimulus (UCS), whereas the other (CS-) appeared alone. The UCS was an air puff delivered to the left eye. In addition to the CS+ and CS-, the vertical test patch was also presented for the clockwise and anticlockwise adapters. The vertical patch was not followed by the UCS. After participants acquired differential conditioning, eyeblink conditioned responses (CRs) were observed for the vertical patch when it appeared to be tilted in the same direction as the CS+ owing to the TAE. The effect was observed not only when the adapter and test stimuli were presented in the same retinotopic position but also when they were presented in the same spatiotopic position, although spatiotopic TAE was weak-it occurred approximately half as often as the full effect. Furthermore, spatiotopic TAE decayed as the time after saccades increased, but did not decay as the time before saccades increased. These results suggest that the time before the performance of saccadic eye movements is needed to compute the spatiotopic representation.

Surround-contingent motion aftereffect.

We investigated whether motion aftereffects (MAE) can be contingent on surroundings. Random dots moving leftward and rightward were presented in alternation. Moving dots were surrounded by an open circle or an open square. After prolonged exposure to these stimuli, MAE were found to be contingent upon the surrounding frames: dots moving in a random direction appeared moving leftward when surrounded by the frame that was presented in conjunction with rightward motion. The effect lasted for 24h and was observed when adapter and test stimuli were presented not only retinotopically, but also at the same spatiotopic position. Furthermore, the effect was observed even when the adapter and test stimuli were presented at different retinotopic and spatiotopic positions as long as they were presented in the same hemi-field. These results indicate that MAE would be influenced not only by the stimulus features, but also by their surroundings, and they suggest that the surround-contingent MAE might be mediated in the higher stage of the motion processing pathway.

Spatiotemporal Processing in Crossmodal Interactions for Perception of the External World: A Review.

Research regarding crossmodal interactions has garnered much interest in the last few decades. A variety of studies have demonstrated that multisensory information (vision, audition, tactile sensation, and so on) can perceptually interact with each other in the spatial and temporal domains. Findings regarding crossmodal interactions in the spatiotemporal domain (i.e., motion processing) have also been reported, with updates in the last few years. In this review, we summarize past and recent findings on spatiotemporal processing in crossmodal interactions regarding perception of the external world. A traditional view regarding crossmodal interactions holds that vision is superior to audition in spatial processing, but audition is dominant over vision in temporal processing. Similarly, vision is considered to have dominant effects over the other sensory modalities (i.e., visual capture) in spatiotemporal processing. However, recent findings demonstrate that sound could have a driving effect on visual motion perception. Moreover, studies regarding perceptual associative learning reported that, after association is established between a sound sequence without spatial information and visual motion information, the sound sequence could trigger visual motion perception. Other sensory information, such as motor action or smell, has also exhibited similar driving effects on visual motion perception. Additionally, recent brain imaging studies demonstrate that similar activation patterns could be observed in several brain areas, including the motion processing areas, between spatiotemporal information from different sensory modalities. Based on these findings, we suggest that multimodal information could mutually interact in spatiotemporal processing in the percept of the external world and that common perceptual and neural underlying mechanisms would exist for spatiotemporal processing.

Surround-contingent tilt aftereffect.

We investigated whether aftereffects can be contingent on surroundings. Gabor patches tilted clockwise and counterclockwise were presented in alternation. Each patch was surrounded by an open circle or an open square. After prolonged exposure to these stimuli, tilt aftereffects were found to be contingent upon the surrounding frames: Vertical test patches appeared tilted clockwise when surrounded by the frame that was presented in conjunction with the adaptation patch tilted counterclockwise. The effect lasted 24 hours and was observed only when adaptation and test stimuli were presented at the same retinotopic position, but not observed at the same spatiotopic position. These results indicate that the aftereffect would be influenced not only by stimulus features but also by their surroundings.

Vision contingent auditory pitch aftereffects.

Visual motion aftereffects can occur contingent on arbitrary sounds. Two circles, placed side by side, were alternately presented, and the onsets were accompanied by tone bursts of high and low frequencies, respectively. After a few minutes of exposure to the visual apparent motion with the tones, a circle blinking at a fixed location was perceived as a lateral motion in the same direction as the previously exposed apparent motion (Teramoto et al. in PLoS One 5:e12255, 2010). In the present study, we attempted to reverse this contingency (pitch aftereffects contingent on visual information). Results showed that after prolonged exposure to the audio-visual stimuli, the apparent visual motion systematically affected the perceived pitch of the auditory stimuli. When the leftward apparent visual motion was paired with the high-low-frequency sequence during the adaptation phase, a test tone sequence was more frequently perceived as a high-low-pitch sequence when the leftward apparent visual motion was presented and vice versa. Furthermore, the effect was specific for the exposed visual field and did not transfer to the other side, thus ruling out an explanation in terms of simple response bias. These results suggest that new audiovisual associations can be established within a short time, and visual information processing and auditory processing can mutually influence each other.

Neurotropic virus tracing suggests a membranous-coating-mediated mechanism for transsynaptic communication.

Swine hemagglutinating encephalomyelitis virus (HEV) has been shown to have a capability to propagate via neural circuits to the central nervous system after peripheral inoculation, resulting in acute deadly encephalomyelitis in natural host piglets as well as in experimental younger rodents. This study has systematically examined the assembly and dissemination of HEV 67N in the primary motor cortex of infected rats and provides additional evidence indicating that membranous-coating-mediated endo-/exocytosis can be used by HEV for its transsynaptic transfer. In addition, our results suggested that this transsynaptic pathway could adapted for larger granular materials, such as viruses. These findings should help in understanding the mechanisms underlying coronavirus infections as well as the intercellular exchanges occurring at the synaptic junctions.

Visuo-somatosensory reorganization in perceptual adaptation to reversed vision.

Humans can adapt to reversal of the visual field after long-term wear of reversing prism spectacles. Among various aspects of adaptation to reversed vision, adjustment of visually-guided behavior has been consistently found. On the other hand, there is relatively little quantitative evidence for 'perceptual adaptation', for example, restoration of perceptual harmony between the visual and tactile world. To elucidate perceptual adaptation to reversed vision, we conducted long-term experiments with continuous wear of reversing spectacles. Four human adult participants wore left-right reversing spectacles for 37 or 32days. Perceptual adaptation was examined by spatial left-right judgment tasks for visual, auditory, and somatosensory stimuli. In the visuo-motor (VM) and somato-visual (SV) tasks, correct responses disappeared completely at the beginning of prism wearing, but gradually restored, first in the VM task, and subsequently in the SV task. Moreover, the VM and SV tasks revealed aftereffects (incorrect responses) upon removal of the reversing prisms after the long adaptation period. In the auditory-motor (AM) task, responses were mostly correct irrespective of the reversed vision, but incorrect responses transiently appeared approximately when the adaptive change was first observed in the SV task. Moreover, starting from the period when these changes in the SV and AM tasks emerged, an adaptive sign of interhemispheric interaction was revealed by functional Magnetic Resonance Imaging. These results indicate that perceptual adaptation to reversed vision does occur, and that it proceeds to visuo-somatosensory reorganization, which seems to transiently accompany global cross-modal interactions.

Sound frequency and aural selectivity in sound-contingent visual motion aftereffect.

BACKGROUND: One possible strategy to evaluate whether signals in different modalities originate from a common external event or object is to form associations between inputs from different senses. This strategy would be quite effective because signals in different modalities from a common external event would then be aligned spatially and temporally. Indeed, it has been demonstrated that after adaptation to visual apparent motion paired with alternating auditory tones, the tones begin to trigger illusory motion perception to a static visual stimulus, where the perceived direction of visual lateral motion depends on the order in which the tones are replayed. The mechanisms underlying this phenomenon remain unclear. One important approach to understanding the mechanisms is to examine whether the effect has some selectivity in auditory processing. However, it has not yet been determined whether this aftereffect can be transferred across sound frequencies and between ears. METHODOLOGY/PRINCIPAL FINDINGS: Two circles placed side by side were presented in alternation, producing apparent motion perception, and each onset was accompanied by a tone burst of a specific and unique frequency. After exposure to this visual apparent motion with tones for a few minutes, the tones became drivers for illusory motion perception. However, the aftereffect was observed only when the adapter and test tones were presented at the same frequency and to the same ear. CONCLUSIONS/SIGNIFICANCE: These findings suggest that the auditory processing underlying the establishment of novel audiovisual associations is selective, potentially but not necessarily indicating that this processing occurs at an early stage.

Indiscriminable sounds determine the direction of visual motion.

On cross-modal interactions, top-down controls such as attention and explicit identification of cross-modal inputs were assumed to play crucial roles for the optimization. Here we show the establishment of cross-modal associations without such top-down controls. The onsets of two circles producing apparent motion perception were accompanied by indiscriminable sounds consisting of six identical and one unique sound frequencies. After adaptation to the visual apparent motion with the sounds, the sounds acquired a driving effect for illusory visual apparent motion perception. Moreover, the pure tones with each unique frequency of the sounds acquired the same effect after the adaptation, indicating that the difference in the indiscriminable sounds was implicitly coded. We further confrimed that the aftereffect didnot transfer between eyes. These results suggest that the brain establishes new neural representations between sound frequency and visual motion without clear identification of the specific relationship between cross-modal stimuli in early perceptual processing stages.

Sounds can alter the perceived direction of a moving visual object.

Auditory temporal or semantic information often modulates visual motion events. However, the effects of auditory spatial information on visual motion perception were reported to be absent or of smaller size at perceptual level. This could be caused by a superiority of vision over hearing in reliability of motion information. Here, we manipulated the retinal eccentricity of visual motion and challenged the previous findings. Visual apparent motion stimuli were presented in conjunction with a sound delivered alternately from two horizontally or vertically aligned loudspeakers; the direction of visual apparent motion was always perpendicular to the direction in which the sound alternated. We found that the perceived direction of visual motion could be consistent with the direction in which the sound alternated or lay between this direction and that of actual visual motion. The deviation of the perceived direction of motion from the actual direction was more likely to occur at larger retinal eccentricities. These findings suggest that the auditory and visual modalities can mutually influence one another in motion processing so that the brain obtains the best estimates of external events.

Introductory tests to in vivo evaluation: magnetic coupling influence in motor controller.

An implantable centrifugal blood pump has been developed with original features for a ventricle assist device (VAD). This pump is part of a multicenter and international study with objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations were performed followed by prototyping and in vitro tests. Also, previous blood tests for assessment of hemolysis showed mean normalized index of hemolysis (NIH) results of 0.0054 ± 2.46 × 10⁻³ mg/100 L (at 5 L/min and 100 mm Hg). To precede in vivo evaluation, measurements of magnetic coupling interference and enhancements of actuator control were necessary. Methodology was based on the study of two different work situations (1 and 2) studied with two different types of motors (A and B). Situation 1 is when the rotor of pump is closest to the motor and situation 2 its opposite. Torque and mechanical power were collected with a dynamometer (80 g/cm) and then plotted and compared for two situations and both motors. The results showed that motor A has better mechanical behavior and less influence of coupling. Results for situation 1 showed that it is more often under magnetic coupling influence than situation 2. The studies lead to the conclusion that motor A is the best option for in vivo studies as it has less influence of magnetic coupling in both situations.

Preliminary studies for the development of a second generation granulocytapheresis (G-CAP) column. Part II: in vitro and ex vivo studies.

Our previous studies concluded Egyptian cotton was the most appropriate material for making a second generation granulocytapheresis (G-CAP) column as structural dimensions of the cotton fibers are able to attract granulocytes. Unfortunately, it is considered to be blood incompatible as its fibers are of non-synthetic origins. In this study we examined the alteration of the removal rates of blood cells with different surface modifications of Egyptian cotton to enhance its blood compatibility. The surface-modified cotton fibers were compared after three kinds of combination treatments. There were no differences in the removal rates of white blood cells (WBCs) and particularly neutrophils with the use of three kinds of biolized cottons. Next, an ex vivo animal study with a healthy dog was performed with the prototype of the G-CAP column. The dog's blood pressure (BP) decreased to approximately 80% of the initial values of BP at 20 min after the start of the extracorporeal circulation. The decrease in BP gradually reverted to normal. WBCs and particularly neutrophils decreased significantly at 15 min after the start of the extracorporeal circulation and remained low during the extracorporeal circulation. The ability of this column to remove WBCs was maintained during extracorporeal circulation. Especially, neutrophils at the inlet of the column were thoroughly removed for 1 h. Based upon these results, a second generation G-CAP column could be fabricated with Egyptian cotton and applied for clinical use on the condition that the biocompatibility of the Egyptian cotton needs to be improved by the appropriate biolization method.

Sound-contingent visual motion aftereffect.

BACKGROUND: After a prolonged exposure to a paired presentation of different types of signals (e.g., color and motion), one of the signals (color) becomes a driver for the other signal (motion). This phenomenon, which is known as contingent motion aftereffect, indicates that the brain can establish new neural representations even in the adult's brain. However, contingent motion aftereffect has been reported only in visual or auditory domain. Here, we demonstrate that a visual motion aftereffect can be contingent on a specific sound. RESULTS: Dynamic random dots moving in an alternating right or left direction were presented to the participants. Each direction of motion was accompanied by an auditory tone of a unique and specific frequency. After a 3-minutes exposure, the tones began to exert marked influence on the visual motion perception, and the percentage of dots required to trigger motion perception systematically changed depending on the tones. Furthermore, this effect lasted for at least 2 days. CONCLUSIONS: These results indicate that a new neural representation can be rapidly established between auditory and visual modalities.

Auditory motion information drives visual motion perception.

BACKGROUND: Vision provides the most salient information with regard to the stimulus motion. However, it has recently been demonstrated that static visual stimuli are perceived as moving laterally by alternating left-right sound sources. The underlying mechanism of this phenomenon remains unclear; it has not yet been determined whether auditory motion signals, rather than auditory positional signals, can directly contribute to visual motion perception. METHODOLOGY/PRINCIPAL FINDINGS: Static visual flashes were presented at retinal locations outside the fovea together with a lateral auditory motion provided by a virtual stereo noise source smoothly shifting in the horizontal plane. The flash appeared to move by means of the auditory motion when the spatiotemporal position of the flashes was in the middle of the auditory motion trajectory. Furthermore, the lateral auditory motion altered visual motion perception in a global motion display where different localized motion signals of multiple visual stimuli were combined to produce a coherent visual motion perception. CONCLUSIONS/SIGNIFICANCE: These findings suggest there exist direct interactions between auditory and visual motion signals, and that there might be common neural substrates for auditory and visual motion processing.

The need to change our objective for artificial heart development: from totally implantable permanent ventricular assist devices to wearable therapeutic ventricular assist devices.

As a therapeutic VAD to be combined with drugs, apheresis, and cellular implants, it is advisable to develop a wearable VAD for less than 6 months of application. Such an example was shown by describing the therapeutic BCM Gyro centrifugal VAD.

Sounds move a static visual object.

BACKGROUND: Vision provides the most salient information with regard to stimulus motion, but audition can also provide important cues that affect visual motion perception. Here, we show that sounds containing no motion or positional cues can induce illusory visual motion perception for static visual objects. METHODOLOGY/PRINCIPAL FINDINGS: Two circles placed side by side were presented in alternation producing apparent motion perception and each onset was accompanied by a tone burst of a specific and unique frequency. After exposure to this visual apparent motion with tones for a few minutes, the tones became drivers for illusory motion perception. When the flash onset was synchronized to tones of alternating frequencies, a circle blinking at a fixed location was perceived as lateral motion in the same direction as the previously exposed apparent motion. Furthermore, the effect lasted at least for a few days. The effect was well observed at the retinal position that was previously exposed to apparent motion with tone bursts. CONCLUSIONS/SIGNIFICANCE: The present results indicate that strong association between sound sequence and visual motion is easily formed within a short period and that, after forming the association, sounds are able to trigger visual motion perception for a static visual object.

Evaluation of systemic external microwave hyperthermia for treatment of pleural metastasis in orthotopic lung cancer model.

External microwave (EMW) hyperthermia system (2.45 GHz wave frequency) was evaluated by in vitro studies and in vivo pleural metastasis animal model. Three different non-small-cell lung cancer cells and normal fibroblast cells (control) were treated once a day for 3 days with the prototype EMW system applying mild (39 degrees C), moderate (43 degrees C), and severe (47 degrees C) hyperthermia. On Day-4, tested cells were retrieved and examined by apoptosis assay kit and Western blot analysis. Cancer cells treated with moderate hyperthermia showed significant apoptosis; yet no major damage was observed to normal fibroblast cells. Western blot analysis indicated cleavage on caspase-3, -9 and PARP. Also in the cell cycle analysis, increase of sub G0-G1 population was identified. After optimization of the heating intensity for in vivo environment, we created pleural metastatic animal model in 24 immune deficiency mice (male nu/nu mice) to evaluate inhibitory effect of systemic EMW hyperthermia for disseminated tumor growth. Out of 24 mice, 8 received mild and 8 received moderate hyperthermia, and remaining 8 were the no treatment control. Whole chest area of the experimental animals was irradiated 3 times a week for 2 weeks (total of 6 time irradiations). No significant adverse event was observed including abnormal weight loss, skin burn, ulceration, and death. Metastasized tumors around the pleura and chest cavity were 75% reduced in size and weight compared to non-treated control group. Harvested tumors were stained and TUNEL assay demonstrated significant apoptosis in a moderate hyperthermia group. The EMW hyperthermia system may be possible alternative tool as a systemic hyperthermia therapy in severely advanced lung cancer patients. Further study is necessary to determine device safeness, efficacy, and synergistic effect to other possible combination therapies.