A new view on visuomotor channels: the case of the disappearing dynamics

A considerable body of kinematic data supports the proposal that independent visuomotor channels are involved in the control of the transport and grip components of reach and grasp. These channels are seen as having separate perceptual inputs, outputs and internal processing and are thought by some to correspond to independent neuroanatomical pathways. The idea that different groups of muscles and biomechanical structures can be controlled independently is attractive, but this kinematically-inspired hypothesis fails to take into account the complexity of the dynamic relationships and their interactions within the neuromusculoskeletal system. Inertial, viscous, centrifugal, coriolis, gravitational and reflex cross couplings exist between efferent drives to muscles and resulting body movements. Rotation at even a single joint generates a complex set of dynamic reaction forces and requires coordinated activation of many muscles throughout the body to maintain posture and balance. In this theoretical paper we present a new view of independent visuomotor channels in the form of an adaptive neural controller that can compensate for the above interactions and decouple the relationships between efferent drives to muscles and resulting body movements. At the same time, the neural controller renders all the dynamics (linear and nonlinear), other than time delays, of the neuromusculoskeletal system, unobservable in the visuomotor relationships. Using the geometry of nonlinear dynamical systems we show that, providing certain constraints on the structure of time delays within the system are satisfied, there exists a neural controller that can render all the dynamics of the neuromusculoskeletal system (except for time delays) unobservable in the responses. The controller simultaneously decouples all the interactive dynamics so that each of the m independent inputs controls one and only one degree of freedom of the response. This means that each degree of freedom in a multi-joint response can be controlled by an independent component of the visual input, a behaviour that has long been observed in visual tracking experiments. The controller effectively establishes m independent visuomotor channels. However, rather than reflecting separate neuroanatomical pathways, the independent channels result from a neural controller with convergent and divergent connections to compensate for the interactive nonlinear dynamics within the neuromusculoskeletal system. This new view of visuomotor channels has implications for neural control processes involved in the acquisition and adaptability of skilled perceptual-motor behaviour in general, as well as for the design of robotic controllers.     

Enhanced occipital and anterior cingulate activation in men but not in women during exposure to angry and fearful male faces

Blood-oxygenation-level-dependent signal was measured with functional magnetic resonance imaging in 24 healthy young subjects (12 men and 12 women) during viewing of angry, fearful, and neutral male and female face pictures. Exposure to angry male as opposed to angry female faces activated the visual cortex and the anterior cingulate gyrus significantly more in men than in women. A similar sex-differential brain activation pattern was present during exposure to fearful but not neutral faces. Previous behavioral studies indicate enhanced physiological arousal in men but not in women during exposure to angry male as opposed to female faces, and brain imaging studies have shown that the occipital cortex and the anterior cingulate gyrus are influenced by activity in the autonomic nervous system as well as by visual attention. Hence, we suggest that the elevated occipital and anterior cingulate activation in men during confrontation with other angry and fearful males may reflect enhanced vigilance in a potentially dangerous situation.     

The influence of prior knowledge and repeated questioning on children's long-term retention of the details of a pediatric examination

Children's recall of the details of pediatric examinations was examined over the course of a 6-month interval. Although the 83 4- to 7-year-old participants reported a substantial amount of information at each assessment, performance declined over time, dropping sharply over the course of 3 months but then remaining constant out to the final interview at 6 months. As expected, older children provided more total information than younger children did and reported a greater proportion of the event components in response to general rather than specific questions. However, comparable patterns of remembering and forgetting over time were observed at each age level. In addition, no effects of repeated questioning--in the form of an interview at 3 months for half of the children--were observed on performance at the 6-month assessment. Moreover, children's prior knowledge about routine doctor visits was assessed before the checkup for half of the participants at each age and was associated with initial but not delayed recall. Although knowledge increased with age as expected, it nonetheless affected recall over and above the influence of age.     

Six-year follow-up of three treatment programs to personality disorder

Previous studies of long-term outcome for personality disorder (PD) were either retrospective in design or did not include a control condition. In this paper we report results for three PD cohorts (N = 111) treated in two different specialist psychosocial programs (step-down and long-term inpatient) and in general psychiatric treatment as usual (TAU), which were prospectively followed up for 72-months after intake. The three PD samples were compared on symptom severity, social adjustment, global functioning and other clinical indicators (self-mutilation, parasuicide and readmission rates) at intake, 6, 12, 24, and 72 months. Results indicated that a specialist step-down model showed significantly greater change than a purely inpatient model and TAU in most key dimensions of functioning, a difference maintained at 72-months follow-up. Improvement in the samples was not associated with amount of intercurrent treatment received in the year prior to the follow-up assessment. This study confirms that a step-down program retains significant improvement associated with a specialist psychosocial approach for PD. However, this conclusion should be qualified by design limitations. The samples were not randomly allocated to the three conditions and the naturalistic geographical allocation used in the study created a potential for a number of confounds. Whilst we used extensive statistical controls, the possibility that the differences found between the groups may be due to population differences cannot be discounted.     

Gender-deviant boys compared with normal and clinical control boys

The physical movement and social characteristics of effeminate behavior-problem, referred boys (N=13)were compared with those of normal boys (N=25)and boys (N=12)referred for nongender problems. Parent reports, observer ratings, and videotapes were collected in a series of structured tasks. As expected, mothers described gender-problem sons as much more feminine than the other two groups in interests, activities, and mannerisms. Gender-problem sons were also seen as relatively inactive and introverted. Further, they were non-significantly lower than the clinical control boys in perceived behavior problems, but both groups had marginally more problems than the normal boys. Gender-problem and clinical control boys both showed more body constriction than normal boys in ratings of a videotaped interview. They also both showed less ideal ball-throw form than normal boys on a set of variables scored with slow-motion video. However, in a set of behaviors directly rated in the various tasks, the gender-problem boys gave a uniquely general impression of uncoordination. The groups did not differ on seven additional variables.The research was supported in part by USPHS Grant MH17072. The authors are indebted to the more than two dozen research staff members who contributed many essential services at various stages of the project, to the families who generously participated, to the clinicians who referred their clients to our project, and to Marion Hee for computational assistance.