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Converging evidence suggests that dysfunctional inhibitory control might be at the roots of overeating and binge eating disorder (BED). The majority of these results stems from studies on obese populations, however we hypothesized that potential prodromes might be evident also in non-clinical conditions, when binge eating episodes are present (without a diagnosis of BED) and a normal Body Mass Index is preserved. To explore this issue, brain activity of 42 normal weight individuals with and without binge eating episodes (21 binge eaters and 21 non-binge eaters, BE and non-BE respectively) was assessed by means of functional magnetic resonance imaging (fMRI) during response inhibition tasks. We adopted a food-modified version of a go/no-go (GNG) and stop signal task (SST): these tasks investigate different aspects of inhibitory control (action restraint and cancellation) that have been rarely studied in the same individuals but that are known to involve different neural networks. In addition, impulsivity traits were assessed with self-report instruments. Despite similar behavioral performances, the two groups differed in trait impulsivity and brain activity. The fMRI results revealed differential engagement of fronto-striatal regions between the groups during the tasks. The BE group, compared to non-BE, showed lower activation of the right middle frontal gyrus (MFG) and Putamen during the GNG task, and higher activation of the left MFG during the SST. These findings provide evidence of a dissociation of the neural underpinnings of action restraint and cancellation in impulsive individuals. Moreover, they add support to the hypothesis that impulsivity may be a possible hallmark of binge eating behavior (in the absence of weight or full-blown eating disorders) and yield new insights on the role of regions typically involved in response inhibition and selection as possible substrates of impulsive eating.

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This study investigated working memory (WM) in children with Attention-Deficit/Hyperactivity Disorder (ADHD) using a task switching paradigm with Stroop color-word stimuli which required participants to switch from color-naming to word-reading. High and low WM load conditions were compared by manipulation of task reminders as a tempo cue. The sample comprised 83 children with ADHD and 29 normal children comparable in age (aged 7 to 13). Within the ADHD group, participants were divided according to the presence or absence of Learning Disability (LD). Results indicated that children with ADHD had slower response times and less accurate responses in general, however, the ADHD groups were not consistently slower in the high WM load condition. Instead, an impairment in adjusting response speed to cope with higher task demands (i.e., high WM load condition) was found. These results do not support the previously documented association between ADHD and a primary deficit in WM for task switching. However, children with ADHD do demonstrate a specific difficulty in slowing down for a demanding task. Present findings suggest that earlier proposals of under-arousal and poor state regulation in ADHD deserve renewed attention.

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BACKGROUND: In hemispatial neglect, space can be dissociated on the basis of "near" peripersonal vs "far" extrapersonal space. The clinical manifestations of neglect can be modified by having patients use a tool to explore "far" extrapersonal space. An explanation for this is that the use of a stick produced an extension of body space resulting in a remapping of "far" space as "near" space. OBJECTIVE: S: To determine whether the remapping of space can be generalized to the amelioration of the "affected" vs the "nonaffected" space, rather than being confined to the selective amelioration of "far" vs "near" neglect; and to determine whether tool use is a necessary condition for the remapping of space. METHODS: Using virtual reality, the authors asked six hemispatial neglect patients to reach and grasp a real object while simultaneously observing the grasping of a virtual object located within a virtual environment by a virtual hand. The virtual hand was commanded in real time by their real hand. RESULTS: After a period of adaptation, hemispatial neglect patients coded the visual stimuli within the neglected space in an identical fashion as those presented within the preserved portions of space. CONCLUSIONS: It is possible to re-create links between the affected and the nonaffected space. Wielding a tool is not a necessary condition in reopening neglected space.

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OBJECTIVE: To assess the effects of left parietal injury on covert visual attention during a detection task and a pointing task. METHODS: The Posner's paradigm was given to a patient who was found at the age of 74 to have spent all his life without the left parietal lobe as a result of a congenital perinatal insult and to a control subject. In one session subjects were required to provide an arbitrary response at stimulus appearance (key press). In another session subjects were required to point to the stimulus. RESULTS: The patient was able to disengage covert attention from a cued position when the task was to provide an arbitrary key press response in a similar fashion to a control subject with no neurological deficits. By contrast, he was impaired in disengaging attention from a cued position when the task was to reprogramme an overt pointing action. CONCLUSIONS: Response to cued information is differentially available depending on task. It is suggested that mechanisms concerned with the attention for action systems are located within the left parietal lobe.

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A single case study is presented of an unusual dissociation between the sensory perception of an object and the grasping action towards the same object. The patient IW was found at age 74 to have spent all his life without the left parietal lobe, as a result of a congenital peri-natal insult. IW does not show any signs of sensory dysfunction, but he has a persistent motor bias that arises during movement towards objects. When IW was required to reach and grasp stationary and rotating objects, he consistently grasped the objects to the left side. Thus, it appears that information that is available at a sensory level can nevertheless be unavailable at a motor level. Our findings not only help to clarify the functions of the parietal lobe, but also show that lesions in this area are linked specifically to a process of response performance, which is fundamental for our understanding of visuomotor control.

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This article includes two experiments aimed at investigating how two-dimensional (2-D) and three-dimensional (3-D) distractors affect the kinematics of prehension and aiming movements in order to understand the attentional processes involved in visuomotor control. In Experiment 1, subjects grasped large targets in the presence of both large and small 3-D distractors and their corresponding 2-D photographs. The distractors appeared for either 10 sec or appeared simultaneously with the target presentation. It was found that reach and grasp kinematics were influenced primarily by the small, suddenly appearing 3-D distractors. In Experiment 2, the purpose was to examine the conclusion that competition between objects (target and distractor) is related to the behavioral goal of the task. Experiment 2 is a replication of Experiment 1, with the exception that pointing movements were made instead of grasping movements. Results show that both 3-D and 2-D distractors interfered with pointing kinematics, supporting the hypothesis that attentional mechanisms are related to the goal of the task.

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The aim of the present study was to examine the contribution of the thumb and index finger during the task of reaching to grasp a cylinder positioned at different orientations. To this end an axis was defined between a marker positioned on the subjects' wrist and the target. For each frame the perpendicular distances of the thumb and index finger from this axis were determined. The perpendicular distance was greater for the index finger than the thumb, confirming a relative stability of the thumb during natural prehension and supporting the notion of the thumb as a guide for the transport component of reaching. Further, index finger perpendicular distance was varied according to object orientation. When the object was positioned at an angle that requires hand pronation, the perpendicular distance for the index finger was the greatest. It is concluded that changes in the index finger distance are necessary to allow the thumb to maintain stability in order to provide appropriate movement guidance.

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The aim of the present experiment was to investigate attentional processing of colour and location cues using a detection task. Subjects were required to respond to cued corners of a line drawing of a three-dimensional cube. Both cue and target were highlighted in red or green in one corner of the cube. Cues could be valid or invalid with respect to both the colour and location of subsequent targets. Results indicated a significant main effect of location validity, but no main effect of colour validity. Results also indicated that significant colour cueing effects were evident when location cues were invalid. These data also suggested different time courses for the processing of location and colour information. Location validity effects were largest at the shortest interstimulus interval (ISI) and decreased slightly with increasing ISI. In contrast, colour validity effects were absent at the shortest ISI, but thereafter increased with increasing ISI. The results of this experiment indicate that colour cues can be effective even in an inherently spatial task, provided there is sufficient time for the processing of colour information.

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Using synthetic objects, I investigate whether recognition performance is sensitive to different features of cast and attached shadows. Participants were required to recognise familiar objects presented to central vision while the presence, position and shape of cast and attached shadows were systematically manipulated. Costs in response time were found for naming objects in incongruent lighting and shadow conditions, that is, when the object was presented with a cast shadow that originated from a different object and when it was also non-congruently illuminated (e.g. attached shadow indicating that the source of light was from the left, and cast shadow indicating that the source of light was from the right).

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In the two experiments of this study, we assessed the influence of target size and semantic category on the expression of reach-to-grasp kinematic parameters. Moreover, we investigated the influence of size and semantic category of distractors on reaches to the target. The experimental objects represented living and non-living categories and wide and narrow grasp sizes. Participants reached for and picked up mid-sagittally placed targets, which were either alone or flanked by distractors congruent or incongruent to semantic category and size of the target. In experiment 1, movement duration was faster to living objects. We could not replicate this, however, in experiment 2. Conversely, significant and reliable Category x Size interactions for grasp were obtained in experiment 1 and replicated in experiment 2. The pattern of the means in these interactions coincided with the absolute volumetric properties of the stimuli, indicating that the size of the stimuli was the main determinant of the expression of kinematic parameters. We conclude that volumetric properties such as size, rather than semantic category, are the crucial features in the programming and execution of movement to targets. As regards the category and size of the distractor, interference effects were evident: both category and size exerted a comparable influence on reaches to the target. The direction of interference, however, was not systematic. The interference effects are discussed in the context of visual search models of attention.

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The aim of the present study was to assess the effects of dopaminergic medication on the selection-for-action mechanisms in Parkinson's disease (PD). PD subjects were tested after not having taken medication for at least 12 h ("Off' state) and then retested 1-2 h after medication ("On" state). A three-dimensional kinematic system (ELITE, BTS, Italy) was used to record reach-to-grasp movements to a target object placed at a reaching distance of 30 cm. The target was presented alone or in the presence of distractor objects, which could be of either the same size (compatible distractor) or a different size (incompatible distractor). PD subjects in the Off state were significantly more affected by the presence of the incompatible distractor than in the On state. These results indicate that dopaminergic medication is of benefit in reducing interference effects when distractor objects evoke motor programs that differ from the motor program elicited by the target. Results are discussed in light of the role played by the striatal and mesocortical dopaminergic systems for response selection in basal ganglia disorders.

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Descriptions of interference effects from non-relevant stimuli are extensive in visual target detection and identification paradigms. To explore the influence of features of non-relevant objects on reach-to-grasp movements, we instructed healthy normal controls to reach for and pick up a cylinder (target) placed midsagittally 30 cm from the starting position of the hand. In Experiment 1, the target was presented alone, or accompanied by a narrower, wider, or same-size distractor positioned to the left or right of the target. In Experiment 2, the target was presented alone or accompanied by a distractor, which was slanted at a different orientation to the target. Reflective markers were placed on the wrist, thumb, and index finger of the right hand, and infra-red light-detecting cameras recorded their displacement through a calibrated 3-dimensional working space. Kinematic parameters were derived and analysed. Consistent changes in the expression of peak velocity, acceleration, and deceleration were evident when the distractor was narrower or wider than the target. The impact of the orientation of the distractor, conversely, was not marked. We discuss the results in the context of physiological findings and models of selective attention.

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The aim of the present study was to assess the effects of dopaminergic medication on the organisation of the reach-to-grasp movement in Parkinson's disease. A three-dimensional kinematic system (ELITE, B/T/S Italy) was used to record reach-to-grasp movements to objects of either small (0.7 cm) or large (8 cm) diameter placed at a reaching distance of either 20 or 30 cm. Vision of the reaching limb and target was also manipulated. Parkinson's disease participants (N = 14) were assessed in 'OFF' (12 h without medication) and 'ON' (1-2 h post-administration of medication) states. In the 'ON' state, movement duration and the time spent in arm deceleration were significantly less than in the 'OFF' state. The amplitudes of peak reaching velocity, acceleration and deceleration were all higher in the 'ON' than in the 'OFF' state. Further, in the 'ON' state, the acceleration profile no longer exhibited small irregular adjustments, the number of significant correlations between parameters measured from the transport and manipulation components was greater, and the movement was more direct in both the mediolateral horizontal and vertical planes. These results indicate that dopaminergic medication is of benefit in reducing bradykinesia and in fine-tuning kinematic parameterisation of a selected reach-to-grasp action.

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In solving the selection-for-action problem, it is believed that attentional mechanisms enable dominance of target over non-target objects. However, under some conditions, information from non-target objects "interferes" with the action to a relevant target. We investigated the possibility that this interference may result when the irrelevant object activates a specific subset of visuomotor pathways. Participants reached to grasp three-dimensional stimuli while actively attending to a nearby flanker object. The means by which the flanker was presented was manipulated. This relevant object was illuminated either abruptly or gradually. The parvocellular pathway in early visual processing is equally activated in both conditions. The magnocellular pathway is strongly activated by abrupt presentation and weakly activated with gradual presentation of the flanker object. Kinematics of the reach-to-grasp action to the target showed signs of interference only in the sudden illumination condition. This suggests a dissociation between dorsal and ventral cortical streams in terms of relevance for action. Our data suggests that this effect is not due to early visual-pathway differences, but instead reveals a property of a transient object-based visual attention mechanism.

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In the present study the kinematics of the reach-to-grasp movement towards a target object in the presence of distractors was investigated. Three experiments were conducted. In the first experiment, there were three conditions, (a) the target alone, (b) the target presented with a distractor object that was semantically similar to the target and (c) the target presented with a distractor object that was semantically different from the target. The same conditions were repeated for the second experiment but the size of the distractors were also manipulated. For the third experiment the target was presented with a distractor object that was semantically different from the target but similar in shape. In the first experiment interference effects were observed in kinematic parameters of the grasp, but not for the reach component when the target and the distractor were semantically different. In the second and the third experiment, similar results were found. Results are discussed in terms of conflicting processing between objects pertaining to different semantic categories.

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Most attention research has viewed selection as essentially a perceptual problem, with attentional mechanisms required to protect the senses from overload. Although this might indeed be one of several functions that attention serves, the need for selection also arises when one considers the requirement of actions rather than perception. This review examines recent attempts to determine the role played by selective mechanisms in the control of action. Recent studies looking at reach-to-grasp responses to target objects in the presence of distracting objects within a three-dimensional space are discussed. The manner in which motor aspects of the reach-to-grasp response might be influenced by distractors is also highlighted, rather than merely addressing the perceptual consequences of distractors. The studies reviewed here emphasize several factors highlighting the importance of studying selective processes within three-dimensional environments from which attention and action have evolved.

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Unilateral neglect is a disorder involving difficulty in attending to the side of space contralesional to brain injury. Two recent experiments have shown that task-irrelevant background motion reduces neglect on line bisection tasks; however, task-relevant motion has not been assessed. We investigated the effect of task-relevant object motion on left neglect using a moving cube presented on a computer screen. Subjects responded to cued corners of the cube as it moved across the screen. Direction of cube motion had a significant impact on the magnitude of neglect. Responses to left hemispace targets appearing on a leftward moving cube were equal to patients' fastest responses. In contrast, responses to left hemispace targets appearing on a rightward moving cube were the slowest of all responses. These results demonstrate that contralesional object motion is capable of normalising neglect patients' detection of contralesional targets.

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This study assessed the adaptive response of the reach-to-grasp movement of 12 Parkinson's disease (PD) and 12 control subjects to a simultaneous perturbation of target object location and size. The main aim was to test further the reported dysfunction of PD subjects in the simultaneous activation of movement components. Participants were required to reach 30 cm to grasp a central illuminated cylinder of either small (0.7 cm) or large (8 cm) diameter. For a small percentage of trials (20/100) a visual perturbation was introduced unexpectedly at the onset of the reaching action. This consisted of a shift of illumination from the central cylinder to a cylinder of differing diameter, which was positioned 20 degrees to the left (n = 10) or to the right (n = 10). The subject was required to grasp the newly illuminated cylinder. For the Parkinson's disease subject group, the earliest response to this 'double' perturbation was in the parameter of peak reaching acceleration, which was on average 50 ms earlier for 'double' perturbed than for non-perturbed trials. The grasp component response followed more than 500 ms after the earliest transport response. For the control subjects initial signs of a response to the 'double' perturbation were seen almost simultaneously in the transport parameter of peak arm deceleration, and in the manipulation parameter of maximum grip aperture, but these changes were not evident until more than 400 ms after movement onset. These results indicate that the basal ganglia can be identified as part of a circuit which is involved in the integration of parallel neutral pathways, and which exercise flexibility in the degree to which these components are 'coupled' functionally. With basal ganglia dysfunction the activation of integration centres that at first gate the flow of information to the parallel channels of reach and grasp seems inefficient.

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Performance on the covert visuo-spatial attentional functions of orienting and focusing by a group of ADHD children (n = 20) was compared to that of age and sex-matched control children. In Experiment 1, responses were given to cued targets at valid and invalid locations. In Experiment 2, responses were given to targets presented in small, medium-sized or large visual field locations. For both experiments, the hypotheses that reaction times of ADHD children would be greater than those of control children and that performance would be asymmetrical, were supported. For Experiment 1, ADHD children showed bilaterally greater 'benefits' from having directed attention to the cued location and greater 'costs' in having to relocate the attentional focus than controls. In Experiment 2, the hypothesis that the function of focusing attention by ADHD children may show breakdown in the usual pattern of an increase in reaction time with focus area was partly supported by the finding of similar reaction times to targets presented in medium-sized and large regions of the left visual hemifield. These results have been interpreted as reflecting a stronger anchorage of attention by ADHD children upon a cued location and an inability to shift covert attention easily to an alternative location. The breakdown of the focusing function suggests adoption of similar time response sets across focus area size by the more compromised right hemisphere.

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