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Results for “Goal-directed control”

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PubMed1987

The properties of goal-directed eye movements evoked by microstimulation of the cerebellar vermis in the cat.

The properties of eye movements evoked by microstimulation of the cerebellar vermis, lobules V VII, were investigated in encéphale isolé cats. The evoked eye movements tended to reach the same final goal in the orbit irrespective of initial eye position. The goal position depended on stimulus intensity. In contrast with the monkey, the goal of the eye movement lay within the oculomotor range. The goal position of the eye movements evoked by simultaneous stimuli delivered to two sites corresponded with the point which was obtained by the vectorial addition of the two eye movements evoked by the stimulation of each site. These findings suggest that the cat vermal lobules V VII play an important role in the control of horizontal and vertical eye position in the orbit.

Animals↗

PubMed2026

The effects of visuomotor training and tDCS stimulation on visuomotor integration and visual processing: an electrophysiological approach.

BACKGROUND: Visuomotor integration coordinates visual and motor cortical activity to produce goal-directed responses and can be indexed by Rolandic Mu-rhythm suppression and visual evoked potential (VEP) P100 parameters. Perceptual-motor training improves visuomotor performance, and transcranial direct current stimulation (tDCS) over primary motor cortex (M1) has been reported to enhance motor learning when paired with training. This study examined whether anodal M1 tDCS augments the effects of Senaptec visuomotor training in healthy adults. METHODS: Sixty participants were randomized to active anodal tDCS (five 10-minute sessions, 1 mA; n = 31) or sham (n = 29) over M1 immediately before each Senaptec training session; 53 completed all sessions and post-testing. Outcomes were Mu-suppression ratios, VEP P100 latency and amplitude, and Senaptec measures of visual sensitivity and visuomotor control. RESULTS: Active tDCS produced no augmentation of any outcome, with no significant group × time interaction for any measure, consistent across composite and task-level analyses. Training alone produced no change in Mu suppression or visuomotor control. By contrast, both groups showed significant training-related gains in visual sensitivity, including near-far quickness and stereopsis, accompanied by shorter P100 latencies and larger amplitudes, indicating more efficient early visual processing. CONCLUSIONS: A clear dissociation emerged: training produced robust improvements in early visual processing, whereas neither tDCS nor training altered sensorimotor (Mu) or visuomotor-control measures. The tDCS results should be interpreted cautiously given the modest dose and limited power to detect small effects, rather than as evidence of inefficacy. Tablet-based perceptual training enhanced visual processing independent of neuromodulation.

Humans↗

PubMed1996

Opposite asymmetries in blind locomotor orientation of patients with panic agoraphobia compared to those with generalized anxiety.

Panic agoraphobic subjects constantly struggle with the accurate registration of everyday space-time dimension. They are hindered in the exploration of their surroundings by constant self-directed attention. In our investigations we examined whether during experimental goal-directed locomotion orientation insecurity would appear. The accuracy of target-directed motion, i.e. the degree of lateral deviation, was recorded in three diagnostic groups, panic agoraphobics (15 subjects), generalized anxiety patients (15 subjects), and normal controls (15 subjects), and normal controls (15 subjects). According to our results the approach vector of the panic agoraphobics deviated to the right, while in the case of generalized anxiety patients it deviated to the left, while normal controls did not deviate significantly from the middle line. Results are compatible with previous literature which associated panic with an overactivity of left-sided functions, and generalised anxiety with an overactivity of right-sided functions.

Adult↗

PubMed2000

Pointing to a target from an upright position in human: tuning of postural responses when there is target uncertainty.

Human subjects performed, from a standing position, rapid hand pointings to visual targets located within or beyond the prehension space. To examine the interaction between posture and the goal-directed movement we introduced a visual double-step perturbation requiring a reprogramming of the hand movement. Trials directed towards the same spatial goal but differentiated only by the likeliness of a visual double-step were compared. The hand kinematics was not affected by the uncertainty of the visual perturbation; an increased trunk bending, however, was observed. This suggests that uncertainty constraints are integrated in a predictive manner for the optimal coordination of the hand and postural control systems.

Adult↗

PubMed1999

Influence of attentional capture on oculomotor control.

Previous research has shown that when searching for a color singleton, top-down control cannot prevent attentional capture by an abrupt visual onset. The present research addressed whether a task-irrelevant abrupt onset would affect eye movement behavior when searching for a color singleton. Results show that in many instances the eye moved in the direction of the task-irrelevant abrupt onset. There was evidence that top-down control could neither entirely prevent attentional capture by visual onsets nor prevent the eye from starting to move in the direction of the onset. Results suggest parallel programming of 2 saccades: 1 voluntary goal-directed eye movement toward the color singleton target and 1 stimulus-driven eye movement reflexively elicited by the abrupt onset. A neurophysiologically plausible model that can account for the current findings is discussed.

Adolescent↗

PubMed1999

Medial prefrontal cortex lesions cause deficits in a variable-goal location task but not in object exploration.

The role of the medial prefrontal cortex (PFC) in goal-directed behavior was examined in rats with aspiration lesions. In Experiment 1, PFC lesions resulted in an impaired ability to relearn the location of a behaviorally defined goal arm of a plus-maze after it was moved from an initially fixed position. Lesioned rats also exhibited a significantly greater degree of perseveration compared with control animals. Experiment 2 was an object exploration task in which rats had to respond to a change in the layout of the environment. PFC-lesioned rats performed identically to controls, therefore demonstrating that the deficits observed in Experiment 1 did not result from a deficit in the ability to explore the environment. The results are discussed in terms of several competing, but not mutually exclusive explanations of the role of the PFC in navigation and spatial representation.

Animals↗

PubMed1997

Changes in initiation of orienting gaze shifts after muscimol inactivation of the caudal fastigial nucleus in the cat.

1. The production of a goal-directed saccadic gaze shift involves the specification of movement amplitude and direction, and the decision to trigger the movement. Behavioural and neurophysiological data suggest that these two functions involve separate processes which may interact. 2. The medio-posterior cerebellar areas are classically assigned a major contribution to the control of saccade metrics, and previous cerebellar lesion studies have revealed marked dysmetria of visually triggered gaze shifts. In contrast, these studies did not provide evidence for a cerebellar role in saccadic initiation. 3. In the present study, we investigated in the head-unrestrained cat the deficits in both the initiation and the metrics control of saccadic gaze shifts following pharmacological inactivation of the caudal part of the fastigial nucleus (cFN). 4. After cFN inactivation, latencies for contraversive gaze shifts increased to about 137 +/- 28% of normal, and latencies for ipsiversive gaze shifts decreased to about 84 +/- 8% of normal. Similar changes in head movement latency were observed, such that the temporal coupling between eye and head components remained largely unaffected. 5. Contraversive gaze shifts were more hypometric as their latency increased. In contrast, the degree of hypermetria in ipsiversive gaze shifts was unrelated to latency. 6. These results suggest a functional role of the medio-posterior cerebellum in gaze shift initiation and in storing information about the target location and/or the desired gaze shift amplitude.

Animals↗

PubMed1981

Different effects involved in the interaction of saccades and the vestibulo-ocular reflex.

The accuracy of human goal-directed saccades during passive sinusoidal whole-body rotation is the same as that of normal saccades with the head still. Two mechanisms contribute to this accuracy: 1. There is an incomplete summation (70% on the average) of saccade and VOR velocities. 2. The duration of saccades during head rotation is lengthened if VOR and saccade velocities have the same direction, and is shortened if their direction is opposite. The latter finding supports the hypothesis that saccades are controlled by local feedback.

Eye Movements↗

PubMed1994

Pictorial support for discourse comprehension.

Discourse comprehension often involves the construction of a mental model of a situation and its updating as the discourse progresses. Theory suggests that a picture which depicts the initial physical situation in a story could help young children construct a functional mental model which they might maintain as the story progresses, thereby supporting comprehension. This was tested with young children, 4 to 6 years of age. The ability of those who saw the picture to model the final story event was enhanced and, even though the picture did not depict the main character's goal directly, recall of the goal was increased. This could be explained in terms of the creation of a functional mental model and the increased opportunity that it provides for linking goal-directed events with the goal as the model is updated. Mental representation theory was found useful here for predicting how to support comprehension in ways which could translate readily into practice in the classroom. Some potential applications of the findings in teaching young children are described.

Child Development↗

PubMed2000

Dopamine-mediated stabilization of delay-period activity in a network model of prefrontal cortex.

The prefrontal cortex (PFC) is critically involved in working memory, which underlies memory-guided, goal-directed behavior. During working-memory tasks, PFC neurons exhibit sustained elevated activity, which may reflect the active holding of goal-related information or the preparation of forthcoming actions. Dopamine via the D1 receptor strongly modulates both this sustained (delay-period) activity and behavioral performance in working-memory tasks. However, the function of dopamine during delay-period activity and the underlying neural mechanisms are only poorly understood. Recently we proposed that dopamine might stabilize active neural representations in PFC circuits during tasks involving working memory and render them robust against interfering stimuli and noise. To further test this idea and to examine the dopamine-modulated ionic currents that could give rise to increased stability of neural representations, we developed a network model of the PFC consisting of multicompartment neurons equipped with Hodgkin-Huxley-like channel kinetics that could reproduce in vitro whole cell and in vivo recordings from PFC neurons. Dopaminergic effects on intrinsic ionic and synaptic conductances were implemented in the model based on in vitro data. Simulated dopamine strongly enhanced high, delay-type activity but not low, spontaneous activity in the model network. Furthermore the strength of an afferent stimulation needed to disrupt delay-type activity increased with the magnitude of the dopamine-induced shifts in network parameters, making the currently active representation much more stable. Stability could be increased by dopamine-induced enhancements of the persistent Na(+) and N-methyl-D-aspartate (NMDA) conductances. Stability also was enhanced by a reduction in AMPA conductances. The increase in GABA(A) conductances that occurs after stimulation of dopaminergic D1 receptors was necessary in this context to prevent uncontrolled, spontaneous switches into high-activity states (i.e., spontaneous activation of task-irrelevant representations). In conclusion, the dopamine-induced changes in the biophysical properties of intrinsic ionic and synaptic conductances conjointly acted to highly increase stability of activated representations in PFC networks and at the same time retain control over network behavior and thus preserve its ability to adequately respond to task-related stimuli. Predictions of the model can be tested in vivo by locally applying specific D1 receptor, NMDA, or GABA(A) antagonists while recording from PFC neurons in delayed reaction-type tasks with interfering stimuli.

Animals↗

PubMed1993

Control of goal-oriented, rapid arm movements by individuals with diabetes mellitus.

Diabetic subjects completed a series of rapid, goal-directed arm movements under two conditions of unexpected external loading. Evaluation of electromyographic (EMG) patterns revealed that cocontraction and triphasic activity were predominantly associated with inertial and spring loading, respectively. During inertial load responses some EMG patterns indicated a modified cocontraction pattern. Response accuracy was unaffected by type of load but movement time was greater for the inertial load condition.

Arm↗

PubMed1994

Correlates of temporal perspective.

The present study examined both dispositional and behavioral indices of future and present temporal perspective as measured by the 1985 Gonzalez and Zimbardo scale. To examine the behavioral consequences of individual temporal perspective, the 1988 Robinson method of time diaries was used. Four dispositional indices and their association with individual temporal perspective were examined, need for achievement, work ethic orientation, self-monitoring, and evaluation anxiety. Individuals with a future time perspective placed a strong emphasis on success via goal-directed behavior, paid attention to environmental cues, and engaged in a large number of activities to achieve these goals. Implications for research are discussed.

Activities of Daily Living↗

PubMed1992

Goal-directed care: caring for aggressive nursing home residents with dementia.

1. Aggressive behavior in elders with dementia occurs most often during personal care. It is often a response to invasion of private space and may be prevented or reduced by interpersonal approaches that reflect a set of individualized goals for the resident. 2. Five resident goals for preventing or reducing aggressive behavior are to feel safe, to feel physically comfortable, to experience a sense of control, to experience optimal stress, and to experience pleasure. 3. These goals provide a framework for humane care that respects the personhood of the individual and minimizes the need for psychotropic medications and physical restraints.

Aged↗

PubMed1991

The effects of task preference on performance during purposeful and nonpurposeful activities.

This study examined the number of repetitions, increase in heart rate, increase in blood pressure, and rating of perceived exertion of subjects performing the most-preferred and least-preferred tasks from a predetermined list under purposeful and nonpurposeful conditions. Twenty healthy women completed the four experimental tests in random order for a period of 10 min each. The results indicated that there was no significant interaction (p greater than .05) between task choice and condition, thus implying that the subjects' performance was not influenced by task preference regardless of whether the activity was purposeful or nonpurposeful. Comparisons between the purposeful and nonpurposeful conditions revealed that the increase in heart rate and rating of perceived exertion were significantly higher (p less than .05) during nonpurposeful activity for both the most-preferred and the least-preferred tasks. On the basis of these results, it is recommended that therapists use purposeful, or goal-directed, activities in their practice, even if they are unable to provide their patients with a choice of therapeutic tasks.

Adult↗

PubMedDate not supplied

Effect of rehabilitation tasks on organization of movement after stroke.

OBJECTIVE: The purpose of this study was to examine the effect of presence or absence of an object (goal-directed action vs. rote exercise) and the effect of functional specificity of the object on the organization of reaching movements of persons who have had a stroke. METHOD: A repeated-measure counterbalanced design was used in each of two experiments. Eighteen persons who had been hospitalized after stroke were recruited from the roster of a rehabilitation hospital and through stroke clubs and volunteered to participate. Fourteen of these became the data-producing sample. In Experiment 1, the OPTO-TRAK/3020 motion analysis system was used to record movement when the participants reached for preferred food (goal-directed action) or to a spatial location (rote exercise). In Experiment 2, the system recorded movement when participants reached to pick up the receiver of an active telephone (natural context), a detached receiver (partial context), and a stick (simulated context). The organization of the reach movement was described kinematically as the number of zero crossings of the acceleration profile (smoothness), movement time (speed), displacement, peak velocity (an indication of force), and location of peak velocity in the velocity profile (planning strategy). RESULTS: Goal-directed action produced significantly smoother, faster, more forceful, and more preplanned movement than did the rote exercise condition. Functional specificity of the context did not significantly affect organization of the reach. CONCLUSION: Goal-directed reach enabled persons with stroke to display characteristics typical of reach to a target by persons who have not had a stroke better than reaching out in space. These findings support the occupational therapy practice of using objects in a functional context to improve coordinated movement. However, the nature of the objects to be used requires further study.

Activities of Daily Living↗

PubMed1999

Orbitofrontal cortex and representation of incentive value in associative learning.

Clinical evidence indicates that damage to ventromedial prefrontal cortex disrupts goal-directed actions that are guided by motivational and emotional factors. As a consequence, patients with such damage characteristically engage in maladaptive behaviors. Other research has shown that neurons in the corresponding orbital region of prefrontal cortex in laboratory animals encode information regarding the incentive properties of goals or expected events. The present study investigates the effect of neurotoxic orbitofrontal cortex (OFC) lesions in the rat on responses that are normally influenced by associations between a conditioned stimulus (CS) and the incentive value of reinforcement. Rats were first trained to associate a visual CS with delivery of food pellets to a food cup. As a consequence of learning, rats approached the food cup during the CS in anticipation of reinforcement. In a second training phase, injection of LiCl followed consumption of the food unconditioned stimulus (US) in the home cage, a procedure used to alter the incentive value of the US. Subsequently, rats were returned to the conditioning chamber, and their responding to the CS in the absence of the food US was tested. Lesions of OFC did not affect either the initial acquisition of a conditioned response to the light CS in the first training phase or taste aversion learning in the second training phase. In the test for devaluation, however, OFC rats exhibited no change in conditioned responding to the visual CS. This outcome contrasts with the behavior of control rats; after devaluation of the US a significant decrease occurred in approach to the food cup during presentation of the CS. The results reveal an inability of a cue to access representational information about the incentive value of associated reinforcement after OFC damage.

Animals↗

PubMed1991

Compensatory muscle activity for sitting posture during upper extremity task performance in paraplegic persons.

Compensation for the loss of postural activity of the erector spinae (ES) muscle in spinal cord injured (SCI) subjects was investigated. All SCI subjects had clinically complete lesions below the T3 level. Body disbalance was invoked by requiring sitting subjects to execute reaching movements over individually predetermined distances in a horizontal plane. Myoelectric activity of the latissimus dorsi (LD) muscle and the trapezius pars ascendens (TPA) muscle both in the SCI subjects and in controls was recorded. The body disbalance was measured in terms of changes in the position of the body centre of gravity. The effects of anticipation for body displacement were examined by cuing the direction of the reaching movement. Our results indicate that paraplegic subjects use both LD and TPA to stabilize their sitting posture, in contrast to non-disabled persons. Secondly, the movement anticipation is in general slower in persons with paraplegia. Furthermore, the paraplegic subjects showed considerable impairments concerning the processing of precued information prior to a goal-directed upper extremity movement.

Adolescent↗

PubMed1986

Adaptive gain control of saccadic eye movements.

Properties of gain adaptivity in the saccadic system were studied. Subjects had to track a target which moved in single or double steps. The first target step which elicited the primary saccade had an amplitude in the range of 8-16 deg. The primary saccade triggered a further target displacement of 4 deg either in the same or--in different experimental sessions--in the opposite direction of the first target step. These consistent intrasaccadic target displacements lead to adaptive changes of saccadic amplitudes. The experimental data show that the saccadic system adapts to the stimulus sequence in a simple, parametric manner, namely by changing its gain. Consequently, it is assumed that a single gain element determines saccade sizes for all target eccentricities. Further, it is shown that adaptation has different time courses for gain increase and decrease, and its performance is close to completeness. The results are discussed with respect to the undershooting behaviour of goal-directed saccades and the functional demands to the saccadic system.

Adaptation, Ocular↗