Surfing on a retrograde wave: how does Shiga toxin reach the endoplasmic reticulum?

The influence of eye movements on hand use and pervasive stereotypies in Rett syndrome was studied, to better understand the developmental abnormality in this disorder. Nine patients in the post-regression phase were offered objects. As expected, the girls looked at the objects but usually did not reach for them. Nor were their characteristic hand stereotypies altered by such looking. But the occurrence of stereotypies was promoted by overall shifts in gaze, ie, eye movements in any direction. This finding may be relevant to the late-infancy loss of voluntary hand use in Rett syndrome associated with onset of pervasive stereotypies. It suggests a stage-specific regression to a level characteristic of normal 3-month-old infants who do not reach and grasp, but whose hand clasping and mouthing may be triggered by the perceptual consequences of exploratory eye movements and shifts in gaze.     

Precursors to the development of intention at 6 months: Understanding people and their actions.

Under investigation was whether 6-month-old infants expect people to behave differently toward persons and inanimate objects. Infants were randomly assigned to experimental and control conditions. In the experimental conditions, infants were habituated to an actor who either talked to or reached for and swiped with something hidden behind an occluder. In the test events the actor was occluded, but the infants were shown either a person or an object. In the control condition, infants only saw the person or object stimulus. Results showed that infants who had been habituated to an actor who was talking looked longer at the object, and infants who had been habituated to an actor who was reaching and swiping looked longer at the person. No difference in looking at the stimuli was observed in the control condition. This suggests that infants expect people's actions to be related to objects in ways that are continuous with more mature, intentional understandings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Priming infants to use pattern information in an object individuation task: The role of comparison.

There is evidence that 4.5-month-olds do not always use surface pattern to individuate objects but that they can be primed to attend to pattern differences through select experiences. For example, if infants are first shown events in which the pattern of an object predicts its function (dotted containers pound and striped containers pour), they will attend to pattern differences in a subsequent individuation task. However, 4.5-month-olds must see multiple exemplars of the pound and pour events and view the dotted and striped containers together during the events. These results suggest that it is the formation of event categories, in which pattern is linked to object function, that supports pattern priming and that direct comparison of the exemplars facilitates the extraction of event categories. The present research investigated conditions that support the comparison process in 4.5-month-olds. The results revealed that the comparison process was initiated only when the dotted and striped containers were seen directly adjacent to each other; if the containers sat far apart, so that infants had to shift their gaze to compare them, event categories were not extracted. In addition, it was comparison of the two patterned containers, and not comparison of the two function events, that was critical to the formation of event categories. These results join a growing body of research indicating the importance of comparison to category formation in infants and reveal the impact of categorization and comparison processes on object individuation in infancy. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Object perception and object-directed reaching in infancy.

Conducted 5 experiments to investigate the effects of spatial and kinetic information on infants' perception of and reaching for objects. 65 20–23 wk old infants were presented with a small object, a larger object, and a background surface arranged in depth so that all were within reaching distance. Patterns of reaching for this display were observed, while spatial and kinetic properties of the display were varied. Results show that when the Ss reached for the display, they did not reach primarily for the surfaces that were nearer, smaller, or presented in motion. Ss reached, instead, for groups of surfaces that formed a unit that was spatially connected and/or that moved as a whole relative to its surroundings. Ss reached for the nearer of 2 objects as a distinct unit when the objects were separated in depth or when one object moved relative to the other. They reached for the 2 objects as a single unit when the objects were adjacent or when they moved together. The reaching patterns provide evidence that the Ss organized each display into the kind of units that adults call objects: manipulable units with internal coherence and external boundaries. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object perception in infancy: Interaction of spatial and kinetic information for object boundaries.

Infants' perception of object boundaries was studied using reaching and preferential looking methods. In 3 reaching studies, 5-month-old infants viewed 2 adjacent or separated objects that were stationary, moved together, or moved separately. Infants reached for the objects as distinct units when they moved separately or were separated in space and otherwise reached for the objects as 1 unit. In the looking study, 3-month-old infants were habituated to adjacent or separated objects alternately moving together and separately and were then tested with objects in the other spatial relationship. Patterns of dishabituation provided further evidence that separated or separately moving objects were perceived as distinct units. Infants appear to analyze surface arrangements and motions to form spatially connected bodies that move as wholes. This tendency may stem from an initial conception of the physical world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' use of attentional cues to identify the referent of another person's emotional expression

This study explored 14- and 18-month-old infants' ability to identify the target of an emotional display. In the visual task, infants were presented with 2 boxes. Each box contained an object that could be identified by opening the box lid and looking inside. In the tactile task, the objects had to be pulled out of the boxes before they could be seen. An experimenter expressed happiness as she looked or put her hand inside one box, and disgust as she repeated this action with the other box. Infants were then allowed to explore the boxes. Infants touched both boxes but preferred to search for the happy object. Thus, regardless of age or task, infants identified the target of each emotional display as something inside a box and not the box itself. Infants appeared to use the experimenter's attentional cues (gaze and action) to interpret her emotional signals and behaved as if they understood that she was communicating about the objects.     

Orienting gaze shifts during muscimol inactivation of caudal fastigial nucleus in the cat. I. Gaze dysmetria

The cerebellar control of orienting behavior toward visual targets was studied in the head-unrestrained cat by analyzing the deficits of saccadic gaze shifts after unilateral injection of muscimol in the caudal part of the fastigial nucleus (cFN). Gaze shifts are rendered strongly inaccurate by muscimol cFN inactivation. The characteristics of gaze dysmetria are specific to the direction of the movement with respect to the inactivated cFN. Gaze shifts directed toward the injected side are hypermetric. Irrespective of their starting position, all these ipsiversive gaze shifts overshoot the target by a constant horizontal error (or bias) to terminate at a "shifted goal" location. In particular, when gaze is directed initially at the future target's location, a response with an amplitude corresponding to the bias moves gaze away from the actual target. Additionally, when gaze is initially in between the target and this shifted goal location, the response again is directed toward the latter. This deficit of ipsiversive gaze shifts is characterized by a consistent increase in the y intercept of the relationship between horizontal gaze amplitude and horizontal retinal error. Slight increases in the slope sometimes are observed as well. Contraversive gaze shifts are markedly hypometric and, in contrast to ipsiversive responses, they do not converge onto a shifted goal but rather underestimate target eccentricity in a proportional way. This is reflected by a decrease in the slope of the relationship between horizontal gaze amplitude and horizontal retinal error, with, for some experiments, a moderate change in the y-intercept value. The same deficits are observed in a different setup, which permits the control of initial gaze position. Correction saccades rarely are observed when visual feedback is eliminated on initiation of the primary orienting response; instead, they occur frequently when the target remains visible. Like the primary contraversive saccades, they are hypometric and the ever-decreasing series of three to five correction saccades reduces the gaze fixation error but often does not completely eliminate it. We measured the position of gaze after the final correction saccade and found that fixation of a visible target is still shifted toward the inactivated cFN by 4.9 +/- 2.4 degrees. This fixation offset is correlated to, but on average 54% smaller than, the hypermetric bias of ipsiversive responses measured in the same experiments. In conclusion, the cFN contributes to the control of saccadic shifts of the visual axis toward a visual target. The hypometria of contraversive gaze shifts suggests a cFN role in adjusting a gain in the translation of retinal signals into gaze motor commands. On the basis of the convergence of ipsiversive gaze shifts onto a shifted goal, the straightness of gaze trajectory during these responses and the production of misdirected or inappropriately initiated responses toward this shifted goal, we propose that the cFN influences the processes that specify the goal of ipsiversive gaze shifts.     

Object and event representation in 6?-month-old infants.

Two experiments were conducted in which infants had to use remembered knowledge of auditory visual events to guide their reaching and grasping. The events involved a ball falling noisily through a tube and coming to rest at 1of 2 locations, with either resting site specified by distinctive auditory information. The events were presented initially in the light and then in the dark to determine whether infants would remember and use the auditory cues when they could no longer see where the ball fell. In both experiments, infants' reaching behavior was initiated and carried out after the sound ended, which ensured that search for the ball took place without support from ongoing visual or auditory cues. Accurate searching for the ball depended on infants' experience in the light. The authors conclude that 6 ?-month-olds can represent unseen objects and events and use this knowledge to guide their actions to achieve a goal. The success in this task was contrasted with the failures of infants this age in the Piagetian hidden object task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The early development of object knowledge: A study of infants’ visual anticipations during action observation.

This study examined the developing object knowledge of infants through their visual anticipation of action targets during action observation. Infants (6, 8, 12, 14, and 16 months) and adults watched short movies of a person using 3 different everyday objects. Participants were presented with objects being brought either to a correct or to an incorrect target location (e.g., cup to mouth, phone to ear vs. cup to ear, brush to mouth). When observing the action sequences, infants as well as adults showed anticipatory fixations to the target areas of the displayed actions. For all infant age-groups, there were differences in anticipation frequency between functional and nonfunctional object–target combinations. Adults exhibited no effect of object–target combination, possibly because they quickly learned and flexibly anticipated the target area of observed actions, even when they watched objects being brought to incorrect target areas. Infants, however, had difficulties anticipating to incorrect target locations for familiar objects. Together, these findings suggest that by 6 months of age, infants have acquired solid knowledge about objects and the actions associated with them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cellular distribution of calbindin D28K mRNAs in the adult mouse brain

Catching a moving object requires the ability to predict the future trajectory of the object. To test whether infants can use visual information predictively, reaching for a toy moving at different speeds was investigated in six infants around 11 months of age. The toy was occluded from view by a screen during the last part of its approach. Gaze arrived at the exit side of the screen and the hand started to move forward before the toy had disappeared behind the occluder; these actions were prospectively geared to certain times before the toy would reappear. In addition, hand-movement duration was found to be related to the time of reappearance of the toy--the information used to regulate duration of hand movement being picked up before the toy disappeared behind the occluder. In a longitudinal experiment, the development of predictive reaching was investigated in two infants between the ages of 20 and 48 weeks. At all ages studied, gaze anticipated the reappearance of the moving toy. However, anticipation with hand movement of the disappearance of the toy and the ability to gear actions prospectively to the time (instead of distance) the toy was away from certain points on the track developed relatively late and marked the transition to successfully catching faster-moving toys.     

Effects of gesture and target on 12- and 18-month-olds' joint visual attention to objects in front of or behind them.

Factors affecting joint visual attention in 12- and 18-month-olds were investigated. In Experiment 1 infants responded to 1 of 3 parental gestures: looking, looking and pointing, or looking, pointing, and verbalizing. Target objects were either identical to or distinctive from distractor objects. Targets were in front of or behind the infant to test G. E. Butterworth's (1991b) hypothesis that 12-month-olds do not follow gaze to objects behind them. Pointing elicited more episodes of joint visual attention than looking alone. Distinctive targets elicited more episodes of joint visual attention than identical targets. Although infants most reliably followed gestures to targets in front of them, even 12-month-olds followed gestures to targets behind them. In Experiment 2 parents were rotated so that the magnitude of their head turns to fixate front and back targets was equivalent. Infants looked more at front than at back targets, but there was also an effect of magnitude of head turn. Infants' relative neglect of back targets is partly due to the "size" of adult's gesture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of vision in the on-line correction of illusion effects on action.

Investigated the role of visual information during reaching by comparing conditions in which visual information was either available or unavailable during the movement. In this study, 24 participants reached out and picked up a bar placed on a background grating that induced an illusion in the perceived orientation of the bar. The illusion had a large effect on the orientation of the hand early in the reaches, but this effect decreased continuously as the hand approached the target. This pattern occurred whether or not participants were allowed vision of the hand and target while reaching. These results are consistent with a "planning/control" model of action, in which actions are planned using a context-dependent visual representation but monitored and corrected on-line using a context-independent visual representation. The hypothesized neural bases of these representations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multimodal perception in the control of infant reaching.

Six-month-old infants were presented with sounding objects under 3 conditions of illumination: in full vision, in the dark with target location specified by a glowing and sounding object, and in the dark with location specified by sound alone. Reaching behavior was videotaped with an infrared camera, and hand movement was measured by infrared-emitting diodes on the hand that were tracked by a motion analysis system. No differences were found in reaching behavior for objects in the light and glowing objects in the dark. Reaches for sounding objects in the dark had higher speeds, shorter durations, and more errors compared to the other 2 conditions. These findings indicate that vision of the hand did not appear to affect infants' reaching in this situation, whereas vision of the target did. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unwilling Versus Unable: Infants' Understanding of Intentional Action.

Infants experienced a female adult handing them toys. Sometimes, however, the transaction failed, either because the adult was in various ways unwilling to give the toy (e.g., she teased the child with it or played with it herself) or else because she was unable to give it (e.g., she accidentally dropped it). Infants at 9, 12, and 18 months of age reacted with more impatience (e.g., reaching, looking away) when the adult was unwilling to give them the toy than when she was simply unable to give it. Six-month-olds, in contrast, showed no evidence of this differentiation. Because infants' behavioral responses were appropriately adapted to different kinds of intentional actions, and because the adult's actions sometimes produced results that did not match her goal (when having accidents or failed attempts), these findings provide especially rich evidence that infants first begin to understand goal-directed action at around 9 months of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When observing gaze shifts of others enhances object desirability.

The present research explored when observing gaze shifts of another person, involving both the observer and a specific object, enhances desirability of the gazed-at object. Specifically, we offer an initial attempt to test the idea that a three-step sequence consisting of direct gaze at the observer, followed by object-directed gaze and then by direct gaze at the observer, cues the desirability of an object to the observer and hence increases the perceived desirability of the gazed-at object. We examined this hypothesis in three experiments by manipulating eye-gaze shifts and including a no-gaze control condition. In line with our prediction, results showed that the dynamic sequence of gaze shifts indeed increases perceived object desirability. These findings provide new evidence that a sequence of gaze behavior involving the observer and an object plays an important role in influencing affective evaluation of objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The combined effect of gaze direction and facial expression on cueing spatial attention.

Empirical evidence shows an effect of gaze direction on cueing spatial attention, regardless of the emotional expression shown by a face, whereas a combined effect of gaze direction and facial expression has been observed on individuals' evaluative judgments. In 2 experiments, the authors investigated whether gaze direction and facial expression affect spatial attention depending upon the presence of an evaluative goal. Disgusted, fearful, happy, or neutral faces gazing left or right were followed by positive or negative target words presented either at the spatial location looked at by the face or at the opposite spatial location. Participants responded to target words based on affective valence (i.e., positive/negative) in Experiment 1 and on letter case (lowercase/uppercase) in Experiment 2. Results showed that participants responded much faster to targets presented at the spatial location looked at by disgusted or fearful faces but only in Experiment 1, when an evaluative task was used. The present findings clearly show that negative facial expressions enhance the attentional shifts due to eye-gaze direction, provided that there was an explicit evaluative goal present. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' understanding of the link between visual perception and emotion: "If she can't see me doing it, she won't get angry."

Two experiments investigated 18-month-olds' understanding of the link between visual perception and emotion. Infants watched an adult perform actions on objects. An emoter then expressed neutral affect or anger toward the adult in response to the adult's actions. Subsequently, infants were given 20 s to interact with each object. In Experiment 1, the emoter faced infants with a neutral expression during each 20-s response period but looked at either a magazine or the infant. In Experiment 2, the emoter faced infants with a neutral expression, and her eyes were either open or closed. When the emoter visually monitored infants' actions, the infants regulated their object-directed behavior on the basis of their memory of the emoter's affect. However, if the previously angry emoter read a magazine (Experiment 1) or closed her eyes (Experiment 2), infants were not governed by her prior emotion. Infants behaved as if they expected the emoter to get angry only if she could see them performing the actions. These findings suggest that infants appreciate how people's visual experiences influence their emotions and use this information to regulate their own behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infant imitation after a 1-week delay: Long-term memory for novel acts and multiple stimuli.

Deferred imitation after a 1-week delay was examined in 14-month-old infants. Six actions, each using a different object, were demonstrated to each infant. One of the six actions was a novel behavior that had a zero probability of occurrence in spontaneous play. In the imitation condition, infants observed the demonstration but were not allowed to touch the objects, thus preventing any immediate imitation. After the 1-week delay, infants returned to the laboratory and their imitation of the adult's previous actions was scored. Infants in the imitation condition produced significantly more of the target actions than infants in control groups who were not exposed to the modeling; there was also strong evidence for the imitation of the novel act. From a cognitive perspective deferred imitation provides a means of assessing recall memory and representation in children. From a social-developmental viewpoint the findings illustrate that the behavioral repertoire of infants and their knowledge about objects can expand as a result of seeing the actions of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How 14- and 18-month-olds know what others have experienced.

Fourteen- and 18-month-old infants observed an adult experiencing each of 2 objects (experienced objects) and then leaving the room; the infant then played with a 3rd object while the adult was gone (unexperienced object). The adult interacted with the 2 experienced objects in 1 of 3 ways: by (a) sharing them with the infant in an episode of joint engagement, (b) actively manipulating and inspecting them on his or her own as the infant watched (individual engagement), or (c) looking at them from a distance as the infant played with them (onlooking). As evidenced in a selection task, infants of both ages knew which objects had been experienced by the adult in the joint engagement condition, only the 18-month-olds knew this in the individual engagement condition, and infants at neither age knew this in the onlooking condition. These results suggest that infants are 1st able to determine what adults know (have experienced) on the basis of their direct, triadic engagements with them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Developmental Roots of the Speed-Accuracy Trade-Off.

The speed of adult reaching movements is lawfully related to the distance of the reach and the size of the target. The authors had 7-, 9-, and 11-month-old infants reach for small and large targets to investigate a possible relation between the emergence of this speed-accuracy trade-off and the improvements in infants' ability to pick up tiny objects. By 7 months of age, infants slowed down their reaches for smaller objects. The authors concluded that it was not the ability to use a precision grip that facilitated the speed-accuracy trade-off but rather the other way around. The slowing down toward the end of the movement might set the conditions for the development of fine distal control of the hand. (PsycINFO Database Record (c) 2010 APA, all rights reserved)