Biomedical subjects

Jos J Adam

Publications and source records attributed to Jos J Adam.

9 recordsLinked to original sources

PubMed2003

Selective attention deficits during human pregnancy.

Using a longitudinal design we provide evidence that selective attention - a key component of cognition concerned with selection and preparation - is compromised during pregnancy. Selective attention was operationalized by means of the finger precuing technique, which selectively prepares two of four finger responses. The precuing benefit was taken as a measure of selective attention. Pregnant women showed a significant smaller precuing benefit at week 36 of pregnancy than did the control women, indicating loss of selective attention. Thirty-two weeks after childbirth this performance decrement had vanished, reflecting a functional recovery.

Adult↗

PubMed2003

Preparing for perception and action (I): the role of grouping in the response-cuing paradigm.

Human skilled behavior requires preparatory processes that selectively make sensory and motor systems more efficient for perceiving the upcoming stimulus and performing the correct action. We review the literature concerning these preparatory processes as studied by response-cuing paradigm, and propose a model that accounts for the major findings. According to the Grouping Model, advance or precue information directs a dynamic process of subgroup making-that is, a process of stimulus- and response-set reconfiguration-whereby the internal representation of the task is simplified. The Grouping Model assigns a critical role to the unit of selection, with Gestalt factors and interresponse dependencies mediating the formation and strength of stimulus and response subgroups. In a series of five experiments, we manipulated perceptual and motoric grouping factors, and studied their independent and interactive effects on the pattern of precuing benefits. Generally, the results were consistent with the Grouping Model's account of response-cuing effects.

Adult↗

PubMed2003

The control of sequential aiming movements: the influence of practice and manual asymmetries on the one-target advantage.

The present experiment was conducted to explore the effect of practice on the one-target advantage in manual aiming, as well as asymmetries in intermanual transfer of training. Reaction and movement times for the first movement were longer in the 2-target than in the 1-target task, regardless of the amount of practice, hand preference and practice hand. When two movements were required, peak velocity was lower and, proportionally, more time was spent after peak velocity. Our kinematic results suggest that the one-target advantage is related to both predefined strategies as well as movement implementation processes during execution. Therefore, an integration of advance planning and on-line explanations for the one-target advantage is suggested. Regarding manual asymmetries, right-handers showed more transfer of training from the left to the right hand than vice versa. Left-handers exhibited a reversed pattern of asymmetric transfer of training to right-handers, but they were more disadvantaged using their non-dominant hand. These latter two findings have implications for models of manual asymmetry and upper limb control.

Adult↗

PubMed2003

Rapid visuomotor preparation in the human brain: a functional MRI study.

An important feature of human motor behaviour is anticipation and preparation. We report a functional magnetic resonance imaging study of the neuronal activation patterns in the human brain that are associated with the rapid visuomotor preparation of discrete finger responses. Our imaging results reveal a large-scale distributed network of neural areas involved in fast visuomotor preparation, including specific areas in the frontal cortex (middle frontal gyrus, premotor and supplementary motor cortex), the parietal cortex (intra-parietal sulcus, inferior and superior parietal lobe) and the basal ganglia. Our reaction time results demonstrate that it is easier to prepare two fingers on one hand than on two hands. This hand-advantage phenomenon was associated with relatively enhanced levels of activity in the basal ganglia and relatively reduced levels of activity in the parietal cortex. These findings provide direct evidence for differential activity in a distributed brain system associated with specific neuro-computational operations subserving fast visuomotor preparation.

Adult↗

PubMed2003

Distractor interference in selective reaching: dissociating distance and grouping effects.

In the present experiment, the authors sought to differentiate between a distance and a grouping explanation for the symmetric versus asymmetric patterns of distractor interference in selective reaching. Participants (N = 16) pointed to a green target that appeared either with or without a red distractor. Target-distractor separation was manipulated within an array of 5 closely grouped stimulus boxes, and distractor interference (difference in performance between trials with and trials without a distractor) was measured in reaction time, movement time, percentage errors, and movement endpoints. Small distances (5 mm) between target and distractor yielded a symmetric pattern of interference, whereas large distances (20 mm) yielded an asymmetric pattern, with more interference from near than from far distractors. Those findings support the distance account of distractor interference and refute the grouping account.

Adult↗

PubMed2003

Diminished performance on response-selection tasks in Type 2 diabetes.

Comparisons of visual perception, response-selection, and response-execution performance were made between Type 2 diabetes mellitus patients and a matched nondiabetic control group. 10 well-controlled male patients with Type 2 diabetes without diabetic complications (M age 58 yr.) and an age and IQ-matched non-diabetic control group consisting of 13 male healthy volunteers (M age 57 yr.) were included. Significant differences were found only between the two groups on response-selection performance, which concerns the selection and preparation of an appropriate motor action.

Aged↗

PubMed2002

The one-target advantage: advanced preparation or online processing?

The one-target advantage refers to a shorter movement time for one- target aiming movements, in comparison to aiming attempts followed by a second movement. Theoretical explanations of the one-target advantage vary in the extent to which they attribute this phenomenon to prior planning or to online control mechanisms. In this research, we attempted to gain insight into the control of sequential aiming movements by manipulating the availability of online feedback during this first or second movement component. When the participants vision was occluded during the first movement (Experiment 1) or during the second movement (Experiment 2), their performance was affected, showing that vision was important for online control of the movement sequence. A one-target advantage was found when the second movement was in the same direction as the first, but not when it was reversed with respect to the home button. Both prior planning and online control processes contribute to the one-target advantage. The degree to which these processes are important for limb control depends on the specific task demands

Adult↗

PubMed2002

Effects of distractor load and temporal target-distractor separation on numerical comparison performance: a stimulus-competition approach.

Effects of distractor load and temporal separation between target and distractor onset were studied in a selective attention task. Two experiments required 128 participants to decide as quickly and accurately as possible which of two spatially separated one-digit numerals was larger. Targets were either preceded or succeeded by distractors with intervals of 0, 33, 83, 133, 183, and 233 msec. In Exp. 1, the target digits could appear with 0, 1, 2, or 3 one-digit distractors numerals, representing four levels of distractor load. In Exp. 2, three asterisks were used as distractors. Interference effects of digit distractors varied with distractor load and temporal separation between target and distractor onsets. Moreover, the effects of distractors preceding the target differed from distractors succeeding the target. The pattern of results provided evidence that distractor-interference effects originated from stimulus competition for selection in visual short-term memory. The results were interpreted in terms of attentional engagement theory of Duncan and Humphreys.

Adolescent↗

PubMed2002

Selective reaching: evidence for multiple frames of reference.

Students participated in 3 experiments investigating the use of environment- and action-centered reference frames in selective reaching. They pointed to a green target appearing either with or without a red distractor. Target-distractor distance was manipulated, and distractor interference (difference between distractor trials and no-distractor trials) was measured in reaction time, movement time, and movement endpoint. Target-distractor distance determined the dominant frame of reference. Small distances evoked an environment-centered framework that encoded targets within an external context. Large distances evoked an action-centered framework that encoded targets relative to the start position of the hand. Results support the hypothesis that the brain represents spatial information in multiple frames of reference, with the dominant frame of reference being dependent on the task demands.

Adolescent↗