Visuomotor coordination and intermanual transfer for a proprioceptive reaching task

Two experiments were conducted to determine the role of head constraint, whether present or absent and arm exposure type (terminal or continuous) on the production of intermanual transfer to two types of visual distortion. Experiment 1 investigated intermanual transfer to binocular, lateral prism displacement where the prism base orientation for both eyes was in the same direction. Experiment 2 determined whether intermanual transfer could be produced to squint prism viewing where the prism base orientation for each eye was in an opposite direction (base-out prisms). In both experiments transfer was produced when either head movement during prism exposure was unconstrained or when a terminal arm exposure was employed. Maximal transfer was produced when both of these conditions were employed.     

Imagining the near and far future: The role of location familiarity

Plausible personal events envisioned as occurring in the near future tend to be reported as more vivid than those set in the far future. Why is this? The present set of three experiments identified one’s familiarity with the location in which the event is placed as critical in this regard. Specifically, Experiment 1 demonstrated that amongst a wide range of phenomenological characteristics, clarity of location appears to drive the overall difference in vividness between events imagined to take place in the near and the far future. Experiments 2 and 3 were designed to further elucidate this finding. Experiment 2 demonstrated that near future events are more likely than far future events to be imagined in familiar locations. Experiment 3 showed that future events set in familiar locations tend to be imagined with greater clarity than those set in unfamiliar locations. The results of all three experiments converge on the conclusion that the difference in vividness of events imagined as occurring in the near and far future is mediated by one’s familiarity with the location in which the event is imagined to occur.     

Independent reference frames in human spatial memory: Body-centered and environmentcentered coding in near and far space

Our apparently seamless experience of the spatial environment seems to be derived from information coded across a variety of spatial reference frameworks, each tied to the metric of a different sensory or motor system. A fundamental distinction is that between body-centered and environmentcentered reference frameworks. This study reports the first clear evidence of a behavioral dissociation between body-centered and environment-centered coding in human adults. Subjects, seated in a rotating chair with closed eyes, were required to point to remembered, auditorily presented target locations. The subjects were rotated between the presentation and recall of targets. Targets were held stationary with respect to either body-centered or environment-centered spatial coordinates. Prior to recall, subjects were required to point to a series of prelearned distractor locations, which also remained fixed with reference either to the subject’s body or to the stationary environment. Memory for the target locations was selectively impaired when distractor locations were specified within the same spatial reference frame as the target, regardless of whether target and distractor locations were near to or distant from the subjects. In contrast, distractor locations specified in a different reference frame from that of the target had either little or no effect on memory for target locations.     

Early declarative memory for location

The abilities of 7.5-month-old infants to recall the location of hidden objects after delays averaging 90 seconds were investigated in three experiments. Various kinds of events were introduced during the delays in order to examine the stability of early location memory. Recall, as shown by reaching towards the correct location, was most clearly found when the infants were allowed either to remain seated facing the hiding locations (Expt 1) or were turned around and immediately re-seated (Expt 2) during the delays. In both experiments, the infants’ attention was diverted from the hiding places, but during all or most of the delay the infants were facing the locations. Recall was dampened when infants were removed from the immediate location of the hiding and engaged in other activities such as looking at a picture during the delay (Expt 3). Further analyses indicated an effect for age that coincides with other research on location memory: evidence for recall was more clearly found for the older, but not the younger, 7-month-olds.     

Perceptual-attentional and motor-intentional bias in near and far space

Spatial bias demonstrated in tasks such as line-bisection may stem from perceptual-attentional (PA) "where" and motor-intentional (MI) "aiming" influences. We tested normal participants' line bisection performance in the presence of an asymmetric visual distracter with a video apparatus designed to dissociate PA from MI bias. An experimenter stood as a distractor to the left or right of a video monitor positioned in either near or far space, where participants viewed lines and a laser point they directed under (1) natural and (2) mirror-reversed conditions. Each trial started with the pointer positioned at either the top left or top right corner of the screen, and alternated thereafter. Data analysis indicated that participants made primarily PA leftward errors in near space, but not in far space. Furthermore, PA, but not MI, bias increased bilaterally in the direction of distraction. In contrast, MI, but not PA, bias was shifted bilaterally in the direction of startside. Results support the conclusion that a primarily PA left sided bias in near space is consistent with right hemisphere spatial attentional dominance. A bottom-up visual distractor specifically affected PA "where" spatial bias while top-down motor cuing influenced MI "aiming" bias.     

Distortions in location memory

Memory for the location of a briefly presented target is often distorted in systematic ways. When people remember dot locations within a circular space, they typically show memory biases that appear to reflect a categorical strategy. However, memory for a target location can also be biased toward visible markers or landmarks. In the present study, we investigated the interaction of categorical and landmark effects by providing sectioning lines in a circular space. In the absence of lines, response biases showed categorical effects, whereas in the presence of lines, response biases suggested that participants used a landmark-based scheme. Possible relations between the strategies are discussed.     

Shape effects on memory for location

The participants were 40 students who were briefly presented 32 dot locations, one at a time, and attempted to reproduce each location after a short delay. Half of the participants completed the task with the surrounding shapes being a circle, a horizontal ellipse, and a vertical ellipse; for the other half, the surrounding shapes were a square, a triangle, and a pentagon. Elongation of the task field along an axis led to exaggerated bias along that axis, but the pattern of bias was fairly constant across the shapes. The data were modeled by assuming that bias in estimation was due to the weighting of spatial category prototypes. Modeling indicated that shape affected spacing of prototypes, but there was no evidence that it affected the number of prototypes. These results were consistent with use of a viewer-based frame of reference, with prototypes reflecting four spatial quadrants generated by left—right and up—down distinctions from the viewer’s perspective.     

The role of target distinctiveness in infant perseverative reaching

From a dynamic systems perspective, perseverative errors in infancy arise from the interaction of the perceptual cues with the memory of previous actions. To evaluate this account, we tested 9-month-old infants in a task in which they reached for two targets. Experimenters repeatedly cued the first target, which always matched the background (A), and then cued the second target, which varied in its distinctiveness (B). We predicted that a sufficiently distinctive B target would lessen perseverative responding. Results showed that infants perseverated when reaching for two identical targets, but that they made nonperseverative responses when reaching in the presence of a highly distinctive B target. Reach direction on each trial was jointly determined by the distinctiveness of the target, the immediately preceding perceptual events, and the history of reaches in the task.     

Bisecting the mental number line in near and far space

Much evidence suggests that common posterior parietal mechanisms underlie the orientation of attention in physical space and along the mental number line. For example, the small leftward bias (pseudoneglect) found in paper-and-pencil line bisection is also found when participants “bisect” number pairs, estimating (without calculating) the number midway between two others. For bisection of physical lines, pseudoneglect has been found to shift rightward as lines are moved from near space (immediately surrounding the body) to far space. We investigated whether the presentation of stimuli in near or far space also modulated spatial attention for the mental number line. Participants bisected physical lines or number pairs presented at four distances (60, 120, 180, 240 cm). Clear rightward shifts in bias were observed for both tasks. Furthermore, the rate at which this shift occurred in the two tasks, as measured by least-squares regression slopes, was significantly correlated across participants, suggesting that the transition from near to far distances induced a common modulation of lateral attention in physical and numerical space. These results demonstrate a tight coupling between number and physical space, and show that even such prototypically abstract concepts as number are modulated by our on-line interactions with the world.     

Visuomotor rotations of varying size and direction compete for a single internal model in motor working memory

When participants adapt to equal and opposite visuomotor rotations in close temporal proximity, memory of the 1st is not consolidated. The authors investigated whether this retrograde interference depends on the use of equal and opposite rotations. On Day 1, different groups of participants adapted to a -30 degrees rotation followed 5 min later by rotations of +30 degrees, +60 degrees, or -60 degrees. On Day 2, all groups were retested on the -30 degrees rotation. Either retrograde interference (in groups who adapted to rotations of opposite sign on Day 1) or retrograde facilitation (in the remaining group) was observed. In all groups, learning of the 2nd rotation resulted in unlearning of the first, indicating that all visuomotor rotations compete for common working memory resources.     

The representation of time and location in memory for sentences

Two theoretical approaches to the representation of Time and Location Markers in Memory were contrasted. According to predictions derived from one approach, the amount of forgetting will be the same for two-proposition sentences and sentences with a single proposition and a Time or a Location marker. According to the other approach, the amount of forgetting will be the same for one-proposition sentences and sentences with a Time or a Location Marker. Propositional structure and the level of within-sentence associations were orthogonally varied to create eight within-subject experimental conditions. Ninety subjects studied 40 sentences and were required to recall then. Four dependent variables were used: number of sentences completely recalled, number of sentences partially recalled, number of sentences where information was lost from within the proposition, and number of sentences where a complete proposition was lost. The results suggest that Time and Location markers are represented in memory as arguments in a proposition rather than as separate propositions. Level of associations within the sentence seems to have a different effect when the sentence is composed of one or two propositions. The results also suggest that there may be differences between the representations of Time and Location markers.     

Travelling near and far: Placing children's mobile emotions

Dominant discourses of childhood and mobility lead to the social, spatial and temporal placing of children. Children are considered to transgress mobile space in a way that requires curtailment and restriction but is nevertheless considered a ‘right of passage’. In both playing out and challenging these discourses children exhibit an array of emotions that are contingent on mobile space. Mobility may be fleeting in both time and space, part of the everyday corporeal mobility of children, or it may be less so, a mobility that is experienced less frequently, is less everyday, and more immediately transformative. This article explores children's emotional experiences of travel, both nearer and further, drawing from the ‘mobilities turn’ in social science and conceptualizations of childhood that illustrate how children are situated in relation to adult-centred hierarchies of power, and children's contestation of these power differentials. It draws from two different aspects of children and young people's mobilities: an ethnographic study of everyday mobilities with children travelling relatively short distances on a daily basis, using self-directed video and film-elicitation interviews; and a project that explored children's mobile experiences of long distance travelling and particularly notions of belonging. Drawing from the intersections of these studies demonstrates how the emotional connection with space and place constructs childhoods and challenges notions of childhood, risk and spatial emotionalities.     

No evidence for accurate visuomotor memory: systematic and variable error in memory-guided reaching

The authors explored whether the motor system has access to highly accurate information about the aiming environment after visual occlusion. Participants (N = 14) reached to 1 of 3 midsagittal targets in 4 visual conditions (open-loop, brief-delay, 500-ms delay, and 2,000-ms delay). In all conditions, the aiming environment was first viewed for 2,000 ms. Movements were cued immediately after the initial viewing period in the open-loop and brief-delay conditions. Vision was not occluded until movement onset in the open-loop condition, whereas vision was occluded coincidentally with the movement cue in the brief-delay condition. In the 2 longer delay conditions, the movement was cued following a 500- or a 2,000-ms no-vision delay period. Participants overshot the target in the open-loop condition, but that tendency was significantly reduced in the 3 delay conditions. Moreover, endpoint variability was greater in the 3 delay conditions than in the open-loop condition. A speed-accuracy tradeoff account could not explain the differences between open-loop and delayed reaching. Those findings suggest that the motor system does not have access to highly accurate information about the aiming environment for any appreciable period of time following visual occlusion, consistent with the view that the visuomotor system operates in real time.     

Visuospatial processing in memory for word location in writing

Two experiments examined how visuospatial processing engaged during text composition intervenes in memory for word location. Experiment 1 showed that in contrast to participants who performed a spatial task concurrently with composing a text, participants who performed a concurrent visual task recalled fewer word locations after the composition. Consequently, it is hypothesized that writers process the written text in order to visually represent its physical layout, and that this representation is then used when locating words. Experiment 2 tested this hypothesis by comparing a standard composition condition (with the written trace) with a condition in which the written trace was suppressed during composition, and with a condition without written trace and with added visual noise. Memory for word location only decreased with visual noise, indicating that construction of the visual representation of the text does not rely on the written trace but involves visual working memory.     

Developmental aspects of memory for spatial location

The purpose was to show whether or not the encoding of location met criteria defining an automatic process (L. Hasher & R. T. Zacks, 1979, Journal of Experimental Psychology: General, 108, 356-388; 1984, American Psychologist, 39, 1372-1388). Among other criteria, automatic processes are not expected to show developmental changes beyond an early age, to be unrelated to intelligence level, and to be unaffected by instructions. In the first experiment preschool through sixth-grade children were compared on a 40-picturebook task following incidental (remember the names of pictures) or intentional (remember location) instruction. Subjects viewed and named pictures in sets of four, arranged in quadrants in the opened book, and then attempted to recall names of the objects pictured and to relocate pictures on blank pages. In the second experiment, second and sixth graders, college students, elderly persons, and mentally retarded persons were compared on a 60-picturebook task following either incidental or semantic incidental instructions (give the function of objects pictured). Memory for location was invariant across age groups and intelligence level. The only exception was that 3 and 4 year olds were more accurate following intentional instructions. Otherwise there were no differences between intentional and incidental instructions. Semantic instructions resulted in slightly more accurate locations. The results were interpreted as supportive of the Hasher and Zacks' automaticity hypothesis.     

New protocol for dissociating visuospatial working memory ability in reaching space and in navigational space

Several studies have demonstrated that the processing of visuospatial memory for locations in reaching space and in navigational space is supported by independent systems, and that the coding of visuospatial information depends on the modality of the presentation (i.e., sequential or simultaneous). However, these lines of evidence and the most common neuropsychological tests used by clinicians to investigate visuospatial memory have several limitations (e.g., they are unable to analyze all the subcomponents of this function and are not directly comparable). Therefore, we developed a new battery of tests that is able to investigate these subcomponents. We recruited 71 healthy subjects who underwent sequential and simultaneous navigational tests by using an innovative sensorized platform, as well as comparable paper tests to evaluate the same components in reaching space (Exp. 1). Consistent with the literature, the principal-component method of analysis used in this study demonstrated the presence of distinct memory for sequences in different portions of space, but no distinction was found for simultaneous presentation, suggesting that different modalities of eye gaze exploration are used when subjects have to perform different types of tasks. For this purpose, an infrared Tobii Eye-Tracking X50 system was used in both spatial conditions (Exp. 2), showing that a clear effect of the presentation modality was due to the specific strategy used by subjects to explore the stimuli in space. Given these findings, the neuropsychological battery established in the present study allows us to show basic differences in the normal coding of stimuli, which can explain the specific visuospatial deficits found in various neurological conditions.     

Conscious and unconscious influences of memory for object location

The process-dissociation procedure was used to investigate conscious and unconscious influences of memory for object location. In two experiments, subjects worked with drawings of household objects and rooms of a house depicted on a computer monitor to simulate placing objects in various locations. Memory for object locations was tested by having subjects search for those objects. A double dissociation was obtained between estimates of conscious and unconscious influences of memory computed from equations that assumed independence between these two influences: Age-related differences were found in the estimate of conscious influences, but not in the estimate of unconscious influences, whereas manipulation of habit strength affected the unconscious estimate, but not the conscious estimate. These results were closely fit by a multinomial model assuming independence between conscious and unconscious influences of memory.     

The representation of objects and their attributes in memory: Evidence concerning memory for location

The general principle is advanced that different attributes of objects (e.g. shape and colour) are more readily associated when they are attributes of the same object than when they are attributes of different objects. Previous studies provide support for the principle, for they have shown that a shape is more readily associated with its own colour than, for example, with the colour of its background. In the present experiments, the principle was applied to the attributes of shape and location. In four experiments it was shown that a shape was more readily associated with its own location than with the location of another object. Differences in contiguity between the presentation of the shape and the location with which the shape was to be associated were controlled for, as were other factors. The results were interpreted as providing support for the general principle stated above. It was suggested that the general principle could be explained by supposing that memory is propositional in format.     

Compatibility between stimulated eye, target location and response location

Responses to stimuli are faster when the stimulus location spatially corresponds to the required response (standard Simon effect). Recently, a similar effect has been observed with monocular stimuli. Responses were faster when the response location and the stimulated eye corresponded (monocular Simon effect). It has been suggested that distinct mechanisms may underlie these two Simon effects. Here, we attempted to study these two mechanisms simultaneously. For mean reaction time, a finding of perfect additivity was obtained. These behavioral data coupled with surface electrophysiological measures support the view that two different mechanisms contribute independently to the monocular and standard Simon effect.     

Representation of spatial structure in reaching to a visual target.

Reaches made without feedback to positions on an object's surface reflect the spatial form of the surface. In Experiment 1, the reaching pattern varied with the stimulus surface's spatial attributes, consistent with a point-by-point perceptual representation of the surface. In Experiment 2, systematic reaching errors were determined solely by target position regardless of surface structure, implying a highly consistent representation of location. In Experiment 3, illusory slant was imparted to a surface by an aniseikonic lens. Individual variations in directly judged slant were reflected in the reaching pattern, implying organization of local perceptual representation of location and global perception of spatial attributes of the stimulus into a coherent structure.