Relative or absolute? Implications and consequences of the measures adopted to investigate motor overflow

Motor overflow is involuntary overt movement or covert muscle activity that cooccurs with voluntary movement. Overflow is present in several pathological conditions, as well as in neurologically healthy children and older adults, and can be induced in healthy young adults under effortful conditions. This motor phenomenon may provide insight into the underlying mechanisms and kinetic characteristics of voluntary and involuntary motor control in various populations. Although often measured behaviorally using force transduction techniques, different methods of calculating and presenting such overflow data have resulted in seemingly contradictory findings, with limited discussion of the advantages and limitations of different approaches. In this article, the authors examined the relevant literature to highlight significant methodological considerations for authors and readers conducting or appraising this type of research. Issues regarding the interpretation and reporting of findings are also discussed. Researchers are encouraged to continue using behavioral measures to create well-defined variables that enable the study of the kinematic characteristics of overflow, as these may offer promising new ways forward in better characterizing and understanding this intriguing movement phenomenon.     

Body Integrity Identity Disorder: Deranged Body Processing,Right Fronto-Parietal Dysfunction,and Phenomenological Experience of Body Incongruity

Body integrity identity disorder (BIID) is characterised by profound experience of incongruity between the biological and desired body structure. The condition manifests in “non-belonging” of body parts, and the subsequent desire to amputate, paralyse or disable a limb. Little is known about BIID; however, a neuropsychological model implicating right fronto-parietal and insular networks is emerging, with potential disruption to body representation. We argue that, as there is scant systematic research on BIID published to date and much of the research is methodologically weak, it is premature to assume that the only process underlying bodily experience that is compromised is body representation. The present review systematically investigates which aspects of neurological processing of the body, and sense of self, may be compromised in BIID. We argue that the disorder most likely reflects dysregulation in multiple levels of body processing. That is, the disunity between self and the body could arguably come about through congenital and/or developmental disruption of body representations, which, together with altered multisensory integration, may preclude the experience of self-attribution and embodiment of affected body parts. Ulimately, there is a need for official diagnostic criteria to facilitate epidemiological characterisation of BIID, and for further research to systematically investigate which aspects of body representation and processing are truly compromised in the disorder.     

Relationship between contingency awareness and human performance on random ratio and random interval schedules

In three experiments, human participants pressed the space bar on a computer keyboard to earn points on random-ratio (RR) and random-interval (RI) schedules of reinforcement. Verbalized contingency awareness (CA) for each schedule was measured after the entire task (Experiments 1 and 2), or after each RR–RI trial (Experiment 3). In all three experiments, an ability to accurately verbalize the appropriate contingency for each schedule was associated with typical schedule responding. In addition, lagged correlational analysis of verbalized contingency awareness and schedule performance was undertaken in Experiment 3. Results of these correlations initially suggested that CA scores were better predictors of typical schedule performance on the following trial than typical schedule performance was of CA scores on the following trial; however, further analysis revealed no significant differences between the alternate lagged correlation types in each pair. Findings, therefore, suggest that operant performance on RR and RI schedules is associated with participant-derived rule governed behavior, and results are discussed in terms of the introduction of a new paradigm for measuring this association, and the potential for further research to manipulate these parameters further in order to investigate causality in this respect.     

Habituation and dishabituation during object play in kennel-housed dogs

Domestic dogs are reported to show intense but transient neophilia towards novel objects. Here, we examine habituation and dishabituation to manipulable objects by kennel-housed dogs. Labrador retrievers (N?=?16) were repeatedly presented with one toy for successive 30-s periods until interaction ceased. At this point (habituation), a different toy was presented that contrasted with the first in both colour and odour (since the dog’s saliva would have accumulated on the first), colour alone, or odour alone. No effect of the type of contrast was detected in the number of presentations to habituation, the difference in duration of interaction between the first presentation of the first toy and the presentation of the second toy (recovery), or the duration of interaction with the second toy (dishabituation). Varying the time interval between successive presentations of the first toy up to habituation between 10?s and 10?min had no effect on the number of presentations to habituation, nor did it alter the extent of dishabituation. Varying the delay from habituation to presentation of the second toy, between 10?s and 15?min, affected neither the recovery nor the dishabituation. Overall, the study indicates that loss of interest in the object during object-orientated play in this species is due to habituation to the overall stimulus properties of the toy rather than to any single sensory modality and is also atypical in its insensitivity to the interval between presentations.     

Attachment to God,Images of God,and Psychological Distress in a Nationwide Sample of Presbyterians

Drawing broadly on insights from attachment theory, the present study outlines a series of theoretical arguments linking styles of attachment to God, perceptions of the nature of God (i.e., God imagery), and stressful life events with psychological distress. Main effects and potential stress-moderator effects are then evaluated using data from a nationwide sample of elders and rank-and-file members of the Presbyterian Church (U.S.A.). Key findings indicate that secure attachment to God is inversely associated with distress, whereas both anxious attachment to God and stressful life events are positively related to distress. Once variations in patterns of attachment to God are controlled, there are no net effects of God imagery on levels of distress. There is only modest support for the hypothesis that God images moderate the effects of stressful life events on psychological distress, but no stress-moderator effects were found for attachment to God. Study limitations are identified, and findings are discussed in terms of their implications for religion-health research, as well as recent extensions of attachment theory.     

Early Predictors of Urban Adolescents’ Community Violence Exposure

This study examined the extent to which individual, peer, and family factors predicted the onset of community violence exposure in middle and high school, as well as the indirect effects of early factors. We were particularly interested in the timing of exposure to community violence during adolescence, and thus conducted survival analyses on data from 632 urban youth, followed from first grade through high school. Early aggressive behavior and poor academic readiness were associated with an earlier onset of community violence exposure in adolescence. The effects of early aggression on community violence exposure and victimization were accounted for, in part, by peer rejection and deviant peer affiliation; there was no evidence of moderation by gender or parental monitoring. Findings highlight potential targets for preventive interventions with youth at risk of community violence exposure.     

Inhibition of Return in children with Tourette's syndrome and comorbid forms: A Preliminary Study

Background: This study investigated the nature and functioning of the visual-spatial inhibition of return (IOR) phenomenon in children with “pure” Tourette's syndrome (TS), and those with comorbid forms of TS. Method: Children with TS-only and “TS + comorbid” (TS + ADHD +/- OCD) and matched controls performed the inhibition of return (IOR) task, which involved responding to left and right visual targets appearing on a computer screen that were preceded by congruent or incongruent exogenous visual cues. Results: The TS-only group performed similarly on the IOR task to the controls. When the TS-only group was subdivided into children with mild and severe TS symptoms, a post hoc comparison between the controls and severe TS symptom children revealed that these TS children had a reduced magnitude of IOR for targets appearing in the right visual field. The comparison between the TS + comorbid and controls revealed an atypical IOR pattern for the TS + comorbid group. They displayed a loss of normal facilitatory and inhibitory effects for right visual field targets. Conclusions: The findings suggest abnormalities in attentional “disengage” and “move” mechanisms in TS when directing attention to the right visual field, which may reflect left posterior parietal, superior colliculus, and midbrain pathology.     

Bimanual coordination in chronic schizophrenia

Anomalies of movement are observed both clinically and experimentally in schizophrenia. While the basal ganglia have been implicated in its pathogenesis, the nature of such involvement is equivocal. The basal ganglia may be involved in bimanual coordination through their input to the supplementary motor area (SMA). While a neglected area of study in schizophrenia, a bimanual movement task may provide a means of assessing the functional integrity of the motor circuit. Twelve patients with chronic schizophrenia and 12 matched control participants performed a bimanual movement task on a set of vertically mounted cranks at different speeds (1 and 2 Hz) and phase relationships. Participants performed in-phase movements (hands separated by 0 degrees ) and out-of-phase movements (hands separated by 180 degrees ) at both speeds with an external cue on or off. All participants performed the in-phase movements well, irrespective of speed or cueing conditions. Patients with schizophrenia were unable to perform the out-of-phase movements, particularly at the faster speed, reverting instead to the in-phase movement. There was no effect of external cueing on any of the movement conditions. These results suggest a specific problem of bimanual coordination indicative of SMA dysfunction per se and/or faulty callosal integration. A disturbance in the ability to switch attention during the out-of-phase task may also be involved.     

Unilateral hemispheric activation does not affect free-viewing perceptual asymmetries

Strong leftward perceptual biases have been reported for the selection of the darker of two left/right mirror-reversed luminance gradients under free-viewing conditions. This study investigated the effect of unilateral hemispheric activation on this leftward bias in two groups of dextrals (N = 52 and N = 24). In Experiment 1, activation was manipulated by asking participants to tap with their left or right fingers along their midline. In Experiment 2, participants clenched their left or right hands in their respective hemispaces. Participants selected the stimulus that was darker on the left-hand side 73% of the time. Despite manipulations of activation strength and hemispace, activation had no effect on the asymmetry. If activation was important, the leftward bias should have been enhanced when the left hand/right hemisphere was active and reduced (or reversed) when the right hand/left hemisphere was active. The contribution of left-to-right scanning biases to free-viewing perceptual asymmetries is discussed as an alternative.