Working memory can compare two visual items without accessing visual consciousness.

Recent studies argued that unconscious visual information could access the working memory, however, it is still unclear whether the central executive could be activated unconsciously. We investigated, using a delayed match-to-sample task, whether the central executive is an unconscious process. In the experiment of the present study, participants were asked to compare the locations of two given visual targets. Both targets (or one of the two targets, depending on the experimental condition) were masked by a visual masking paradigm. The results showed an above-chance-level performance even in the condition that participants compared two unconscious targets. However, when the trials with the non-visual conscious experience of the target were removed from the analysis, the performance was no longer significantly different from chance level. Our results suggest that the central executive could be activated unconsciously by some level of stimulus signal, that is still below the threshold for a subjective report.

Spatial-numerical associations in first-graders: evidence from a manual-pointing task.

The current study investigated whether children's mental representations of numbers are organized spatially at the onset of formal schooling using a manual-pointing task. First-graders (N = 77) saw four numbers (1, 3, 7, 9) presented randomly in four spatial positions (extreme left, left, right, extreme right) on a touch screen. In a Go/No-Go task, children were asked to press the appearing numbers as fast and accurately as possible, but only when the numbers were "smaller" (or "larger" in a different block) than 5. Results indicated that response times were significantly affected by the spatial position in which the different numbers were presented. Response times for small numbers (1 and 3) increased and response times for large numbers (7 and 9) decreased, the more they were presented towards the right side of the screen. These findings suggested that first-graders spontaneously employed a spatial number representation that was oriented from left to right. Furthermore, this left-to-right organization could not be easily changed by priming a different direction. Our findings indicate that even young children map numbers continuously onto space.

Self-estimation of physical ability in stepping over an obstacle is not mediated by visual height perception: a comparison between young and older adults.

Older adults tend to overestimate their step-over ability. However, it is unclear as to whether this is caused by inaccurate self-estimation of physical ability or inaccurate perception of height. We, therefore, measured both visual height perception ability and self-estimation of step-over ability among young and older adults. Forty-seven older and 16 young adults performed a height perception test (HPT) and a step-over test (SOT). Participants visually judged the height of vertical bars from distances of 7 and 1 m away in the HPT, then self-estimated and, subsequently, actually performed a step-over action in the SOT. The results showed no significant difference between young and older adults in visual height perception. In the SOT, young adults tended to underestimate their step-over ability, whereas older adults either overestimated their abilities or underestimated them to a lesser extent than did the young adults. Moreover, visual height perception was not correlated with the self-estimation of step-over ability in both young and older adults. These results suggest that the self-overestimation of step-over ability which appeared in some healthy older adults may not be caused by the nature of visual height perception, but by other factor(s), such as the likely age-related nature of self-estimation of physical ability, per se.

Age-related self-overestimation of step-over ability in healthy older adults and its relationship to fall risk.

BACKGROUND: Older adults could not safely step over an obstacle unless they correctly estimated their physical ability to be capable of a successful step over action. Thus, incorrect estimation (overestimation) of ability to step over an obstacle could result in severe accident such as falls in older adults. We investigated whether older adults tended to overestimate step-over ability compared with young adults and whether such overestimation in stepping over obstacles was associated with falls. METHODS: Three groups of adults, young-old (age, 60-74 years; n, 343), old-old (age, >74 years; n, 151), and young (age, 18-35 years; n, 71), performed our original step-over test (SOT). In the SOT, participants observed a horizontal bar at a 7-m distance and estimated the maximum height (EH) that they could step over. After estimation, they performed real SOT trials to measure the actual maximum height (AH). We also identified participants who had experienced falls in the 1 year period before the study. RESULTS: Thirty-nine young-old adults (11.4%) and 49 old-old adults (32.5%) failed to step over the bar at EH (overestimation), whereas all young adults succeeded (underestimation). There was a significant negative correlation between actual performance (AH) and self-estimation error (difference between EH and AH) in the older adults, indicating that older adults with lower AH (SOT ability) tended to overestimate actual ability (EH > AH) and vice versa. Furthermore, the percentage of participants who overestimated SOT ability in the fallers (28%) was almost double larger than that in the non-fallers (16%), with the fallers showing significantly lower SOT ability than the non-fallers. CONCLUSIONS: Older adults appear unaware of age-related physical decline and tended to overestimate step-over ability. Both age-related decline in step-over ability, and more importantly, overestimation or decreased underestimation of this ability may raise potential risk of falls.

The effect of visual and tactile information in motor preparation of climbing.

In rock climbing, an appropriate motor preparation to a given climbing hold(s) is crucial for a fluent climbing. We investigated the influence of visual-tactile information in motor preparation of climbing, particularly the effect of the number of the holds and the tactile input of an actual hold was examined. Reaction times (RTs) under the priming paradigm were compared for climbers and non-climbers. Participants were asked to respond to a visual target (left or right arrow) after the presentation of a picture of a single climbing hold (Single-Prime condition: SP) or two holds (Double-Prime condition: DP). Before commencing each trial block, the participants were also asked to touch or watch an actual hold (touch /no-touch condition). The response based on the congruity between the orientation of the hold and that of the arrow was categorised as either congruent or incongruent. An ANOVA performed on the RTs showed the congruency effect, but this was observed only in the non-climbers. An additional analysis revealed a marginally significant climbing experience-related interaction. In the high-experienced climbers, the RTs in the touch condition were slower than those in the no-touch condition but this was only in the SP condition. In the no-touch condition, the RTs of DP were slower than those of SP. These results therefore suggest that the motor preparation is mediated by visual and tactile inputs of a given hold. The time needed for motor preparation, particularly in highly experienced climbers, may be modulated by the representational complexity of climbing movements through tactile information.Highlight The number of the holds visually presented affected the motor preparation.The tactile input of the climbing hold modulated the motor preparation only in the highly experienced climbers.Our findings imply that climbing-specific context (i.e. combination of the given holds) and experience (i.e. action competency) are involved in the motor preparation of climbing.

The Effect of Simulating Climbing Movements on Rock Memory and Exploratory Movement in Rock Climbing.

Simulating climbing movements on a given route is important for fluent rock climbing. We investigated the effect of simulated action during rock climbing route finding on memory and exploratory movement. Participants were 12 climbers and 12 non-climbers who completed three experimental tasks: (a) a questionnaire, the Vividness of Movement Imagery Questionnaire-2 (VMIQ-2) for measuring vividness of motor imagery, (b) a memory task requiring recognition of rock climbing holds on the route, and (c) a traversing task requiring participants to climb a given route and count the number of exploratory movements made during climbing. During route finding in the memory/traversing task, we experimentally manipulated the simulative body action with motor imagery. Results showed that the simulative action affected exploratory movement during climbing, but it did not affect memorization of the holds. In the traversing task, climbers showed more exploratory movement when the simulative action was present during route finding, while the non-climbers showed an opposite trend. Moreover, for non-climbers, the effect of the simulative action was modulated by the vividness of kinesthetic imagery. We concluded that simulative body action during route finding facilitated motor imagery and spatial information processing for subsequent climbing involving exploratory movement.

Hard and fast rules about the body: contributions of the action stream to judging body space.

Analogously to the visual system, somatosensory processing may be segregated into two streams, with the body constituting either part of the action system or a perceptual object. Experimental studies with participants free from neurological disease which test this hypothesis are rare, however. The present study explored the contributions of the two putative streams to a task that requires participants to estimate the spatial properties of their own body. Two manipulations from the visuospatial literature were included. First, participants were required to point either backward towards pre-defined landmarks on their own body (egocentric reference frame) or to a forward projection of their own body (allocentric representation). Second, a manipulation of movement mode was included, requiring participants to perform pointing movements either immediately, or after a fixed delay, following instruction. Results show that accessing an allocentric representation of one's own body results in performance changes. Specifically, the spatial bias shown to exist for body space when pointing backward at one's own body disappears when participants are requested to mentally project their body to a pre-defined location in front space. Conversely, delayed execution of pointing movements does not result in performance changes. Altogether, these findings provide support for a constrained dual stream hypothesis of somatosensory processing and are the first to show similarities in the processing of body space and peripersonal space.

Touch perception reveals the dominance of spatial over digital representation of numbers.

We learn counting on our fingers, and the digital representation of numbers we develop is still present in adulthood [Andres M, et al. (2007) J Cognit Neurosci 19:563-576]. Such an anatomy-magnitude association establishes tight functional correspondences between fingers and numbers [Di Luca S, et al. (2006) Q J Exp Psychol 59:1648-1663]. However, it has long been known that small-to-large magnitude information is arranged left-to-right along a mental number line [Dehaene S, et al. (1993) J Exp Psychol Genet 122:371-396]. Here, we investigated touch perception to disambiguate whether number representation is embodied on the hand ("1" = thumb; "5" = little finger) or disembodied in the extrapersonal space ("1" = left; "5" = right). We directly contrasted these number representations in two experiments using a single centrally located effector (the foot) and a simple postural manipulation of the hand (palm-up vs. palm-down). We show that visual presentation of a number ("1" or "5") shifts attention cross-modally, modulating the detection of tactile stimuli delivered on the little finger or thumb. With the hand resting palm-down, subjects perform better when reporting tactile stimuli delivered to the little finger after presentation of number "5" than number "1." Crucially, this pattern reverses (better performance after number "1" than "5") when the hand is in a palm-up posture, in which the position of the fingers in external space, but not their relative anatomical position, is reversed. The human brain can thus use either space- or body-based representation of numbers, but in case of competition, the former dominates the latter, showing the stronger role played by the mental number line organization.

Effects of feedback from active and passive body parts on spatial and temporal parameters in sensorimotor synchronization.

Previous research on sensorimotor synchronization has manipulated the somatosensory information received from the tapping finger to investigate how feedback from an active effector affects temporal coordination. The current study explored the role of feedback from passive body parts in the regulation of spatiotemporal motor control parameters by employing a task that required finger tapping on one's own skin at anatomical locations of varying tactile sensitivity. A motion capture system recorded participants' movements as they synchronized with an auditory pacing signal by tapping with the right index finger on either their left index fingertip (Finger/Finger) or forearm (Finger/Forearm). Results indicated that tap timing was more variable, and movement amplitude was larger and more variable, when tapping on the finger than when tapping on the less sensitive forearm. Finger/Finger tapping may be impaired relative to Finger/Forearm tapping due to ambiguity arising through overlap in neural activity associated with tactile feedback from the active and the passive limb in the former. To compensate, the control system may strengthen the assignment of tap-related feedback to the active finger by generating correlated noise in movement kinematics and tap dynamics.

Postural sway in the moving room scenario: New evidence for functional dissociation between self-motion perception and postural control.

Postural control in quiet standing is often explained by a reflexive response to optical flow, the apparent motion of environmental objects in a visual scene. However, moving room experiments show that even small-amplitude body sway can evoke odd sensations or motion sickness, indicating that a consciousness factor may also be involved. Studies targeting perception of self-motion, vection, typically use rapid visual stimuli moving in a single direction to maintain a constant feeling of vection, and there are few studies of vection using low-speed sinusoidal visual stimuli similar to human pendular movement. In the present study we searched for changes in postural control during periods of vection during quiet standing. Participants (N = 19, age = 20.4 ±1.1 years) were shown dynamic visual stimuli in the form of sinusoidally expanding and contracting random dots, and the stimuli speed and visual field were manipulated. Posture was continually evaluated using Center of Pressure (CoP) measurements. Participants were also asked to report feelings of vection, both by pressing a button during the trial and through an overall rating at the end of each trial. Using repeated-measures ANOVA, we assessed changes in the CoP and vection variables between experimental conditions, as well as possible interactions between the variables. The results show that postural reaction and vection were both affected by the visual stimuli and varied with speed. The peripheral visual field was found to couple to stronger feeling of vection and better quality of postural control. However, no significant relationship between postural control and vection, nor evidence of vection interaction to the relationship between optical flow and postural control, was found. Based on our results we conclude that for postural stability during quiet standing, visual cues dominate over any potential consciousness factor arising due to vection.

Shared Representations in Athletes: Segmenting Action Sequences From Taekwondo Reveals Implicit Agreement.

How do athletes represent actions from their sport? How are these representations structured and which knowledge is shared among experts in the same discipline? To address these questions, the event segmentation task was used. Experts in Taekwondo and novices indicated how they would subjectively split videos of Taekwondo form sequences into meaningful units. In previous research, this procedure was shown to unveil the structure of internal action representations and to be affected by sensorimotor knowledge. Without specific instructions on the grain size of segmentation, experts tended to integrate over longer episodes which resulted in a lower number of single units. Moreover, in accordance with studies in figure-skating and basketball, we expected higher agreement among experts on where to place segmentation marks, i.e., boundaries. In line with this hypothesis, significantly more overlap of boundaries was found within the expert group as compared to the control group. This was observed even though the interindividual differences in the selected grain size were huge and expertise had no systematic influence here. The absence of obvious goals or objects to structure Taekwondo forms underlines the importance of shared expert knowledge. Further, experts might have benefited from sensorimotor skills which allowed to simulate the observed actions more precisely. Both aspects may explain stronger agreement among experts even in unfamiliar Taekwondo forms. These interpretations are descriptively supported by the participants' statements about features which guided segmentation and by an overlap of the group's agreed boundaries with those of an experienced referee. The study shows that action segmentation can be used to provide insights into structure and content of action representations specific to experts. The mechanisms underlying shared knowledge among Taekwondoists and among experts in general are discussed on the background of current theoretic frameworks.

Horizontal spatial representations of time: evidence for the STEARC effect.

It is well known that stimuli such as numerals (small vs large) and auditory pitches (low vs high) have spatial characteristics, and that responses to such stimuli are biased by the mental representation of their magnitude. Walsh (2003) has argued that any spatially and action-coded magnitude will yield a relationship between magnitude and space. Here we investigated the spatial representation of 'time' using speeded responses to the onset timing (early vs late) of a probe stimulus following periodic auditory clicks. Participants pressed one of the two response keys depending on whether the timing of a given probe was earlier or later than expected based on the preceding clicks. The results showed that left-side responses to early onset timing were faster than those to late onset timing, whereas right-side responses to late onsets were faster than those to early onsets when the response keys were aligned horizontally. Such a time-response congruity effect was not observed with the vertical alignment of responses. These results suggest that time is represented from left to right along the horizontal axis in space. The existence of a 'mental time line' in space and the spatial-temporal association of response codes (STEARC) effect are discussed.

Differences in the Magnitude of Representational Momentum Between School-Aged Children and Adults as a Function of Experimental Task.

Representational momentum (RM) is the phenomenon that occurs when an object moves and then disappears, and the recalled final position of the object shifts in the direction of its motion. Some previous findings indicate that the magnitude of RM in early childhood is comparable to that in adulthood, whereas other findings suggest that the magnitude of RM is significantly greater in childhood than in adulthood. We examined whether the inconsistencies between previous studies could be explained by differences in the experimental tasks used in these studies. Futterweit and Beilin used a same-different judgment between the position where a moving stimulus disappeared and where a comparison stimulus reappeared (judging task), whereas Hubbard et al. used a task wherein a computer mouse cursor pointed to the position where the moving stimulus disappeared (pointing task). Three age groups (M = 7.4, 10.7, and 22.1 years, respectively) participated in both the judging and pointing tasks in the current study. A multivariate analysis of variance with the magnitudes of RM in each task as dependent variables revealed a significant main effect for age. A one-way analysis of variance performed for each of the judging and pointing tasks also indicated a significant main effect of age. However, post hoc multiple comparisons detected a significant age effect only for the pointing task. The inconsistency between the judging and pointing tasks was discussed related to the distinct effect size of the age difference in the magnitude of RM between the two tasks.

The essential role of optical flow in the peripheral visual field for stable quiet standing: Evidence from the use of a head-mounted display.

It has long been thought that vision is the most essential factor in maintaining stable quiet standing compared to other sources (i.e., vestibular and somatosensory inputs) of information. Specifically, several vision studies on postural control have shown evidence for the importance of the visual system, particularly peripheral vision rather than central vision, and optical flow. Nevertheless, to date, no study has manipulated both visual field and optical flow concurrently. In the present study, we experimentally manipulated both the visual field (the central and peripheral visual fields) and the occurrence of optical flow during quiet standing, examining the effects of the visual field and optical flow on postural sway measured in terms of the center of pressure (CoP). Stationary random dot stimuli were presented exclusively in either the central or peripheral visual field, while the occurrence of optical flow was manipulated using a desktop (DTD) or a head-mounted (HMD) display. The optical flow that occurred while using the DTD was a function of the postural sway during quiet standing, while for the HMD, no optical flow occurred even when the body/head swayed during quiet standing. Our results show that the extent of postural sway (e.g., CoP area) was smaller when visual stimuli were presented in the peripheral visual field than that in the central visual field; this was the case while using the DTD alone, with no effects of the peripheral vision on the extent of postural sway while using the HMD. It is therefore suggested that the optical flow occurring in the peripheral visual field is essential for stable quiet standing.

Interaction between space and number representations during motor preparation in manual aiming.

The existence of a spatial component in the representation of number magnitude has been repeatedly supported by the demonstration that the left hand responds faster to smaller numbers, whereas the right hand responds faster to larger numbers. These results support the view that the 'mental number line' is oriented such that smaller numbers are associated with the left side of space while larger numbers are associated with the right side. We investigated whether the link between spatial and number processing arises from a continuous or categorical mapping between space and number representations. The investigation was designed to study all aspects of the motor act, including both planning and execution phases. For this purpose we measured reaction times (RTs), movement times (MTs), spatial accuracy, and endpoint pressure of manual aiming, while subjects reached with the right hand towards the location of a visual digit target. Five different digits were equiprobably presented at five positions along the horizontal axis. A GO/NO-GO choice task paradigm was used to ensure that digit parity (i.e., odd/even) was being processed. Analyses of MT, accuracy, and pressure data showed no digit effects. However, two number-related effects were observed on RTs. First, shorter RTs were obtained for smaller digits independent of target location, despite the use of the right hand. Second, an interaction was observed between target location and number magnitude whereby relative RTs were shortest when there was a congruity between target magnitude and location. These results imply that motor preparation is contaminated both by the direct activation of number magnitude and by the congruity between the spatial location of a target number and its magnitude. We conclude that continuous mapping intervenes between mental number representation and physical space.

The functional role of central and peripheral vision in the control of posture.

Three experiments were conducted to investigate the role of central and peripheral vision (CV and PV) in postural control. In Experiment 1, either the central or peripheral visual field were selectively stimulated using a circular random dot pattern that was either static or alternated at 5 Hz. Center of foot pressure (CoP) was used to examine postural sway during quiet standing under both CV and PV conditions. The results showed that, when the visual stimulus was presented in the periphery, the CoP area decreased and more so in the anterior-posterior (AP) than in the medio-lateral (ML) direction, indicating a characteristic directional specificity. There was no significant difference between the static and dynamic (alternating) conditions. Experiment 2 investigated the directional specificity of body sway found in Experiment 1 by having the trunk either be faced toward the stimulus display or perpendicularly to it, with the head always facing the display. The results showed that the stabilizing effect of peripheral vision was present in the direction of stimulus observation (i.e., the head/gaze direction), irrespective of trunk orientation. This suggested that head/gaze direction toward the stimulus presentation, rather than a biomechanical factor like greater mobility of the ankle joint in AP direction than in ML direction, was essential to postural stability. Experiment 3 further examined whether the stabilizing effect of peripheral vision found in Experiments 1 and 2 was caused because more dots (500) were presented as visual cues to the peripheral visual field than to the central visual field (20 dots) by presenting the same number of dots (20) in both conditions. It was found that, in spite of the equal number of dots, the postural sway amplitudes were larger for the central vision conditions than for the peripheral vision conditions. In conclusion, the present study showed that peripheral rather than central vision contributes to maintaining a stable standing posture, with postural sway being influenced more in the direction of stimulus observation, or head/gaze direction, than in the direction of trunk orientation, which suggests that peripheral vision operates primarily in a viewer-centered frame of reference characterized by the head/gaze direction rather than in a body-centered frame of reference characterized by the anatomical planes of the body.

Up-down asymmetry in vertical induced motion and optokinetic nystagmus.

We investigated the effects of pursuit effort against the optokinetic nystagmus (OKN) on induced motion (IM) by measuring vertical IM and eye movements. Participants viewed an inducing stimulus (a random dot pattern) moving either upward or downward at the velocity of 10 or 40 °/s. A horizontally moving target (a single dot) was then presented within the inducing stimulus. Participants were asked to pursue the target and report the perceived slant of the target motion path by using a joystick. The results showed that IM magnitude was larger with an upward stimulation than with a downward stimulation. IM magnitude was also larger at 40 °/s than at 10 °/s. The results of eye movements prior to the target presentation showed that OKN was elicited more effectively with an upward stimulation than with a downward stimulation and at 40 °/s than at 10 °/s. OKN was markedly reduced when the target was presented within the inducing stimulus. These results support the oculomotor theory that IM magnitude reflects pursuit effort against OKN in response to an inducing stimulus.

Gastric cancer recognized by metastasis to the ureter.

Although ureteral obstruction is rarely noted in patients with gastric cancer at an advanced stage or at autopsy, the condition caused by authentic ureteral metastasis of gastric cancer is extremely rare. We experienced a case of gastric cancer in a 51-year-old woman who showed bilateral ureteral metastasis. The patient initially complained of right flank pain, caused by right ureteral obstruction, and was referred to our hospital, where she underwent a right nephroureterectomy, with suspicion of primary ureteral neoplasm. Histopathological examination of the resected specimen showed that metastatic growth of adenocarcinoma in the ureteral wall had caused the obstruction, and the subsequent extensive search for the primary lesion revealed asymptomatic gastric cancer. Soon after the nephroureterectomy, the patient developed left hydronephrosis, possibly caused by left ureteral metastasis, and a left percutaneous nephrostomy was performed. She then received chemotherapeutic reagents. However, she finally developed peritoneal carcinomatosis, and died of the disease about 1 year after the onset of the disease. In this report, we also review true ureteral metastasis from the stomach, and discuss the clinicopathologic features.

D2-lymphadenectomy improves the survival of patients with peritoneal cytology-positive gastric cancer.

BACKGROUND: According to the current Japanese Classification of Gastric Cancer, patients with peritoneal cytology-positive (CY1) gastric cancer are classified as stage IV and the curative potential of resection for these patients is regarded as non-curative. MATERIALS AND METHODS: We compared the clinical outcome of CY1 patients (n=55) with those of patients with other non-curative factors (n=87), to clarify the optimal surgical strategy for CY1 patients. RESULTS: The 5-year survival rate of CY1 patients was 10.8%, which was significantly better than that observed in the patients with the other non-curative factors. Among CY1 cases, survival outcome of the patients with lymph node metastasis limited to within group 2 was significantly better than the patients with group 3 lymph node metastasis. CONCLUSION: These results suggested that gastrectomy combined with extended lymphadenectomy should be recommended for patients with gastric cancer who have positive peritoneal cytology as the only non-curative factor.

Lateralized effects of target location on reaction times when preparing for manual aiming at a visual target.

To elucidate the temporal characteristics of information processing for motor action differing in complexity in relation to both perceptual and cognitive information processing, we investigated whether the reaction times (RTs) to a visual target would be affected by task complexity (finger lifting or manual aiming), pre-cueing (with a pre-cue or without a pre-cue), or target location (five horizontal positions). Using the right hand, seven right-handed subjects performed two tasks, finger lifting and manual aiming at a target, with or without a pre-cue. The pre-cue announced the location of the target to be presented. An ANOVA showed significant interactions between task and location and between pre-cue and location with no significant interaction between task and pre-cue, indicating that the task-location interaction does not depend on whether or not a pre-cue is given. The manual-aiming RTs were longer than the finger-lifting RTs, and the effects of the target location on the RTs differed for finger lifting and manual aiming. It can be assumed that the longer RTs of manual aiming reflect the time for information processing that is needed when preparing for the aiming action per se, which is an extra movement performed in addition to the simple initiation of finger lifting. Differential RTs (DRTs) calculated by subtracting the finger-lifting RTs from the aiming RTs were therefore examined. The DRTs significantly differed for target locations (i.e., a lateralized effect), with the DRTs for an ipsilateral target appearing to be significantly shorter than those for contralateral and central targets. The lateralized effect appearing on the DRTs may be mediated by the processing of visual-spatial information about visual targets as motor preparations are made for manual aiming.