触觉时序知觉手臂交叉效应的性别差异

本研究探讨触觉时序知觉的手臂交叉效应是否存在性别差异。通过两个实验在较短和较长的SOA条件下考察男性和女性被试在基于体觉和基于外部空间的触觉时序判断任务中的表现。结果表明,男性与女性被试在基于体觉和基于外部空间的触觉时序判断任务中均存在手臂交叉效应,SOA较短时男性被试的手臂交叉效应显著小于女性被试,但在SOA较长的条件下手臂交叉效应没有明显的性别差异。触觉时序知觉手臂交叉效应的性别差异可能与空间知觉能力和生理解剖学因素有关。     

When left feels right: asymmetry in the affordance effect

Previous research has demonstrated the existence of the so-called affordance effect (faster response when the visual affordance of a graspable object (e.g., a pan) corresponds to the response location). It has been argued that the effect is due to abstract spatial coding of the position of the handle relative to the object instead of the grasping affordance. Our experiment tested the hypothesis that the affordance effect is not caused solely by abstract spatial coding but also by specific motor activation in response to the visual affordance. We assumed that, in the case of abstract spatial codes, response location and not hand distinction would be the critical factor for producing an affordance effect. In our experiment, bi-manual crossed/uncrossed responses to left/right symbols superimposed on a picture of a pan were used. The task was to attend to the symbol and to press a corresponding left/right button. Affordances of the pan were manipulated. A three-way interaction between side of affordance (left/right), mode of response (crossed/uncrossed hands), and response-affordance correspondence (corresponding/non-corresponding) showed a correspondence effect in the right affordance condition with hands uncrossed and no correspondence effect with hands crossed. The correspondence effect was obtained in the left affordance condition across hand positions that differed only by their magnitude. Overall, the results suggest that both mechanisms (grasping affordance and spatial codes) differentially contribute to the processing of an object with a graspable handle, depending on the affordance side and response hand.     

Validity and boundary conditions of automatic response activation in the Simon task.

Three experiments were conducted to determine whether spatial stimulus-response compatibility effects are caused by automatic response activation by stimulus properties or by interference between codes during translation of stimulus into response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, responses are faster at the response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli.     

水平空间与情绪效价联结效应的产生机制

采用词汇效价判断任务,考察水平空间与情绪效价联合效应的产生机制。实验1在被试双手正常放置条件下考察了词汇效价与水平空间联结效应的存在;实验2则要求被试双手交叉放置,以考察当反应手和反应键的空间信息冲突时水平空间与情感效价的关联现象;实验3则进一步考排除反应手的参与,以考察口头报告的反应方式是否对两者的联结效应产生影响。结果表明,不同反应方式下均存在空间情感效价的联结,且此联结更多是反应选择极性编码的结果。     

Mapping of extracorporeal space by vibrotactile reaction times: a far-left-side disadvantage

Vibrotactile reaction times in normal dextrals were measured for the two hands separately when either hand was located at each of seven possible positions: 90 degrees, 45 degrees, and 15 degrees to the left and right of the chest midline, and at the midline itself (0 degrees). Reaction times for the two hands did not differ and there was no Hand by Position interaction. At 90 degrees left, reaction times were significantly slower than at any other position except 45 degrees right. However, none of the other positions, including 45 degrees right, differed from each other. Performance in this task, therefore, was relatively uniform from 90 degrees right to 45 degrees left, but markedly slower at 90 degrees left. This far-left-side disadvantage may reflect a difficulty (for dextrals) in focussing covert attention in the far-left part of space for a block of trials. Since vibrotactile reaction times are sensitive to attentional factors in normal subjects, the paradigm should allow quantification of the clinical symptoms of the hemineglect syndrome; some preliminary observations of this syndrome with another vibrotactile design are reported.     

Change of reference frame for tactile localization during child development

Temporal order judgements (TOJ) for two tactile stimuli, one presented to the left and one to the right hand, are less precise when the hands are crossed over the midline than when the hands are uncrossed. This ‘crossed hand’ effect has been considered as evidence for a remapping of tactile input into an external reference frame. Since late, but not early, blind individuals show such remapping, it has been hypothesized that the use of an external reference frame develops during childhood. Five‐ to 10‐year‐old children were therefore tested with the tactile TOJ task, both with uncrossed and crossed hands. Overall performance in the TOJ task improved with age. While children older than 5½ years displayed a crossed hand effect, younger children did not. Therefore the use of an external reference frame for tactile, and possibly multisensory, localization seems to be acquired at age 5.     

An effect of spatial-temporal association of response codes: understanding the cognitive representations of time

The present study addresses the question of how such an abstract concept as time is represented by our cognitive system. Specifically, the aim was to assess whether temporal information is cognitively represented through left-to-right spatial coordinates, as already shown for other ordered sequences (e.g., numbers). In Experiment 1, the task-relevant information was the temporal duration of a cross. RTs were shorter when short and long durations had to be responded to with left and right hands, respectively, than with the opposite stimulus-response mapping. The possible explanation that the foreperiod effect (i.e., shorter RTs for longer durations) is greater with right than with left hand responses is discarded by results of Experiment 2, in which right and left hand responses alternated block-wise in a variable foreperiod paradigm. Other explanations concerning manual or hemispheric asymmetries may be excluded based on the results of control experiments, which show that the compatibility effect between response side and cross duration occurs for accuracy when responses are given with crossed hands (Experiment 3), and for RTs when responses are given within one hand (Experiment 4). This pattern suggests that elapsing time, similarly to other ordered information, is represented in some circumstances through an internal spatial reference frame, in a way that may influence motor performance. Finally, in Experiment 5, the temporal duration was parametrically varied using different values for each response category (i.e., 3 short and 3 long durations). The compatibility effect between hand and duration was replicated, but followed a rectangular function of the duration. The shape of this function is discussed in relation to the specific task demands.     

Inter-hemispheric remapping between arm proprioception and vision of the hand is disrupted by single pulse TMS on the left parietal cortex

Parietal cortical areas are involved in sensori-motor transformations for their respective contralateral hemifield/body. When arms of the subjects are crossed while their gaze is fixed straight ahead, vision of the hand is processed by the hemisphere ipsilateral to the arm position and proprioception of the arm by the contralateral hemisphere. It induces interhemispheric transfer and remapping. Our objective was to investigate whether a single pulse TMS applied to the left parietal cortical area would disturb interhemispheric remapping in a similar case, and would increase a simple reaction time (RT) with respect to a control single pulse TMS applied to the frontal cortical area. Two LED were superimposed and located in front of the subjects on the saggital axis. Subjects were asked to carefully fixate on these LED during each trial. The lighting of the red LED was used as a warning signal. Following the green one was illuminated after a variable delay and served as a go-signal. The hand for the response was determined before the start of each trial. TMS was applied to the left parietal, the left frontal cortical areas, or not applied to the subject. Results revealed that: (1) Irrespective of its location, single pulse TMS induced a non-specific effect similar to a startle reflex and reduced RT substantially (15 ms on average) with respect to a control condition without TMS (mean value = 153 ms). (2) Irrespective of TMS, RT were shorter when the right or the left hand was positioned in the right visual hemi-field (i.e. normal and crossed positions respectively). (3) Finally, RT increased when single pulse TMS was applied to the left parietal area and when hands were crossed irrespective of which hand was used. We concluded that interhemispheric sensori-motor remapping was disrupted by a single pulse TMS that was applied to the left parietal cortex. This effect was also combined with some visual attention directed towards the hand located on the right visual hemi-field.     

S-R correspondence effects of irrelevant visual affordance: Time course and specificity of response activation

It has been suggested that representations for action, elicited by an object's visual affordance, serve to potentiate motor components (such as a specific hand) to respond to the most afforded action. In three experiments, participants performed speeded left-right button press responses to an imperative target superimposed onto a prime image of an object suggesting a visual affordance oriented to left or right visual space. The time course of response activation was measured by varying the onset time between the prime and target. Long-lasting and gradually developing correspondence effects were found between the suggested affordance of the prime and the side of response, with little effect of response modality (hands uncrossed, hands crossed, or foot response). We conclude that visual affordances can evoke an abstract spatial response code, potentiating a wide variety of lateralized responses corresponding with the affordance.     

S-R compatibility between response position and destination of apparent motion: evidence of the detection of affordances

In choice reaction time, stimuli and responses in some combinations (e.g., based on spatial arrangement) are faster than in other combinations. To test whether motion toward a position yields faster responses at that position, a computer-generated square in front of one hand appeared to move either toward that hand or toward the other hand. Compatible responses (e.g., motion toward left hand/left response) were faster than incompatible responses, even when that opposed traditional positional compatibility. In Experiment 2, subjects responded to the same stimuli but with both hands left, right, or on the body midline. Medial responses were the fastest, showing that destination, rather than mere relative position, was a critical variable. It was suggested that spatial compatibility effects are not unique to position but apply to a variety of task situations, describable by J.J. Gibson's theory of affordances, in which he claims that one perceives the actions (e.g., catching) permitted in a situation.     

Head and body hemispace to left and right III: Vibrotactile stimulation and sensory and motor components

Response latencies were measured to vibrotactile stimulation delivered to the forefingers of the left or right hands which were positioned ipsilaterally or contralaterally (across the midline) in left or right hemispace. While the two hands did not differ in speed of response, either hand performed better when located in right hemispace (experiment 1). This effect was greatly reduced, though not eliminated, with 90 degrees lateral head turn, when performance was better with stimulation and responding in right-of-head hemispace, but not right-of-body hemispace (experiment 2). When different hands received stimulation and initiated responses, and were located in either the same or opposite hemispace, right-hemispace superiority was found to be motor rather than sensory (experiment 3). These findings are discussed in the context of the true and the phenomenological midline and the clinical syndrome of hemineglect.     

Effects of Expectancy and Attention in Vibrotactile Choice Reaction Time Tasks

The orienting of attention in space has not been considered in the tactile domain. This issue is examined using a modified version of a visual paradigm initially adopted by Posner, Snyder, and Davidson (1980), which manipulates the probability of a stimulus occurring at different spatial locations. Slower RTs at an unexpected stimulus location are thought to reflect the time required to shift attention from the expected to the unexpected location. In two experiments involving vibrotactile choice RT between left and right hands, the two hands were either crossed or uncrossed, and the hands were held both on the left side of the body, both on the right, or one on either side of the midline. There was no evidence to suggest that spatial location (left or right) affected the orienting of attention in the tactual modality. As predicted, RTs were slower when the arms were crossed compared with uncrossed, though this effect was smaller for the expected trials. A coding conflict hypothesis may explain both these findings, but the smaller effect in the expected trials may also reflect attentional factors. Both the relative and absolute location of the hands affected the magnitude of the crossed-arm effect and indicated that attention may play a role in the perceptual division of space into left and right sides. Possible reasons for hand or hemispace asymmetries in different simple and choice RT paradigms were discussed.     

Prism adaptation changes the subjective proprioceptive localization of the hands

Prism adaptation involves a proprioceptive, a visual and a motor component. As the existing paradigms are not able to distinguish between these three components, the contribution of the proprioceptive component remains unclear. In the current study, a proprioceptive judgement task, in the absence of motor responses, was used to investigate how prism adaptation would specifically influences the felt position of the hands in healthy participants. The task was administered before and after adaptation to left and right displacing prisms using either the left or the right hand during the adaptation procedure. The results appeared to suggest that the prisms induced a drift in the felt position of the hands, although the after‐effect depended on the combination of the pointing hand and the visual deviation induced by prisms. The results are interpreted as in line with the hypothesis of an asymmetrical neural architecture of somatosensory processing. Moreover, the passive proprioception of the hand position revealed different effects of proprioceptive re‐alignment compared to active pointing straight ahead: different mechanisms about how visuo‐proprioceptive discrepancy is resolved were hypothesized.     

Motor processes in children's imagery: the case of mental rotation of hands

In a mental rotation task, children 5 and 6 years of age and adults had to decide as quickly as possible if a photograph of a hand showed a left or a right limb. The visually presented hands were left and right hands in palm or in back view, presented in four different angles of rotation. Participants had to give their responses with their own hands either in a regular, palms-down posture or in an inverted, palms-up posture. For both children and adults, variation of the posture of their own hand had a significant effect. Reaction times were longer the more awkward it was to bring their own hand into the position shown in the stimulus photograph. These results, together with other converging evidence, strongly suggest that young children's kinetic imagery is guided by motor processes, even more so than adults'.     

Proprioception and Stimulus-Response Compatibility

Sixteen subjects pressed a left or right key in response to lateralized visual stimuli, in uncrossed (left index finger on left key, right finger on right key) and crossed conditions (left finger on right key and vice versa), with varying finger separations. Visual, tactile, or 'efference copy' cues about relative finger positions were unavailable. Subjects had to press the key on the same side as (compatible group) or opposite side to the stimulus (incompatible group). Separate proprioceptive judgements of the relative finger positions were obtained. Findings of an overall reaction time (RT) advantage for compatible instructions and for uncrossed hands were replicated. With decreasing finger separation the RT advantage for compatible instructions decreased, and the probability of responding with either hand increased. The compatibility effect disappeared completely at the 6-cm crossed position, not at the position that was hardest to judge proprioceptively. This suggests that two forms of neural activation are summed: automatic activation of the anatomically same-side limb, and an integrated, rule-based activation. The results further demonstrate that independent proprioceptive cues from each limb, unassociated with skin contact between the limbs, can mediate the determination of relative position for response selection in stimulus-response compatibility tasks.     

Influences of response position and hand posture on the orthogonal Simon effect

When lateralized responses are made to the locations of vertically arrayed stimuli, two types of mapping effect have been reported: an overall up–right/down–left advantage and mapping preferences that vary with response position. According to Cho and Proctor's (2003) multiple asymmetric codes account, these orthogonal stimulus–response compatibility effects are due to the correspondence of stimulus polarity and response polarity, as determined by the positions relative to multiple frames of reference. The present study examined these two types of orthogonal compatibility for situations in which participants made left–right responses to the colours of a vertically arrayed stimulus set, and stimulus location was irrelevant. Although a significant orthogonal Simon effect was not evident when responding at a centred, neutral response position, the effect was modulated by response eccentricity (Experiment 2) and hand posture (Experiment 3). These effects are qualitatively similar to those obtained when stimulus location is task relevant. The results imply that, as Proctor and Cho's (2006) polarity correspondence principle suggests, the stimulus polarity code activates the response code of corresponding polarity even when stimulus location is irrelevant to the task.     

Effects of posture on tactile localization by 4 years of age are modulated by sight of the hands: evidence for an early acquired external spatial frame of reference for touch

Adults show a deficit in their ability to localize tactile stimuli to their hands when their arms are in the less familiar, crossed posture. It is thought that this ‘crossed‐hands deficit’ arises due to a conflict between the anatomical and external spatial frames of reference within which touches can be encoded. The ability to localize a single tactile stimulus applied to one of the two hands across uncrossed‐hands and crossed‐hands postures was investigated in typically developing children (aged 4 to 6 years). The effect of posture was also compared across conditions in which children did, or did not, have visual information about current hand posture. All children, including the 4‐year‐olds, demonstrated the crossed‐hands deficit when they did not have sight of hand posture, suggesting that touch is located in an external reference frame by this age. In this youngest age group, when visual information about current hand posture was available, tactile localization performance was impaired specifically when the children's hands were uncrossed. We propose that this may be due to an early difficulty with integrating visual representations of the hand within the body schema.     

Integration of hand and finger location in external spatial coordinates for tactile localization

Tactile stimulus location is automatically transformed from somatotopic into external spatial coordinates, rendering information about the location of touch in three-dimensional space. This process is referred to as tactile remapping. Whereas remapping seems to occur automatically for the hands and feet, the fingers may constitute an exception in that some studies have implied purely somatotopic coding of touch to the fingers. When participants judge the order of two tactile stimuli, they often err when the stimulated body parts (usually the two hands) are crossed, presumably because somatotopic and external coordinates are in conflict in crossed postures. Using this task, we investigated, first, whether the fingers are unlike other limbs with regard to spatial coding, by testing whether crossing effects, indicative of external coding, were observable when stimulating two fingers, either on the same or on different hands. Second, we investigated the interaction of hand and finger posture in tactile localization of finger stimuli. Crossing effects emerged when fingers and hands were crossed, suggesting external coding for all body parts. Crossing effects were larger when both hand and finger were located in the hemifield opposite to their body side, and smaller when only hand or finger lay in the opposite hemifield. We suggest that tactile location is estimated by integrating the external location of all relevant body parts, here of a finger and its belonging hand, and that such integrative coding may represent a general principle for body part processing as well as for tool use.     

Anisotropic tracking: evidence for automatic synergy formation in a bimanual task

Investigation of interlimb synergy has become synonymous with the study of coordination dynamics and is largely confined to periodic movement. Based on a computational approach this paper demonstrates a method of investigating the formation of a novel synergy in the context of stochastic, spatially asymmetric movements. Nine right-handed participants performed a two degrees of freedom (2D) "etch-a-sketch" tracking task where the right hand controlled the horizontal position of the response cursor on the display while the left hand controlled the vertical position. In a pre-practice 2D tracking task, measures of phase lag between the irregularly moving target and the response showed that participants controlled left and right hands independently, performance of the right hand being slightly superior to the left. Participants then undertook 4 h 16 min distributed practice of a one degree of freedom etch-a-sketch task where the target was constrained to move irregularly in only the 45 degrees direction on the display. To track such a target accurately participants had to make in-phase coupled stochastic movements of the hands. In a post-practice 2D task, measures of phase lag showed anisotropic improvement in performance, the amount of improvement depending on the direction of motion on the display. Improvement was greatest in the practised 45 degrees and least in the orthogonal 135 degrees direction. Best and worst performances were no longer in the directions associated with right and left hands independently, but in directions requiring coupled movements of the two hands. These data support the proposal that the nervous system can establish a model of novel coupling between the hands and thereby form a task-dependent bimanual synergy for controlling the stochastic coupled movements as an entity.     

Is handedness recognition automatic? A study using a Simon-like paradigm

The authors used a modified Simon task (J. R. Simon, 1969) to assess the automatic recognition of handedness. Participants responded to the color of a circle in the center of the photograph of a right or a left hand, displayed in the center of the computer screen. A regular Simon effect was found for back views, whereas a reverse Simon effect was found for palm views. This pattern of results was found when the forearm was present (Experiment 2), when 1 finger at a time was rendered invisible (Experiment 3), and when the hands were connected to a body image (Experiment 4). When the hands were cut at the wrist, no effect emerged (Experiment 1). These findings suggest an automatic encoding of the relative position of the hand in relation to the body (imaginary or real) rather than the automatic encoding of handedness.