Will Spijkers

The effect of low arousal on visuo-spatial attention

Clinical and experimental evidence suggests a special role of the right hemisphere for alerting and orienting. However, it is not clear whether these attentional aspects should be taken to be independent or interacting. At least on the functional neuroanatomical level there seems to be an overlap in right parietal and frontal cortical structures. In this sleep deprivation study we examined the effect of different levels of arousal on covert orienting of attention repeatedly over a period of 28 h in 11 healthy subjects. The main finding is a disproportionate and significant slowing of responses to stimuli presented to the left visual hemifield that could only be observed in a state of maximally reduced arousal at 5:00 a.m. Furthermore, a facilitation of attentional shifts to the right could be observed in invalid trials when attention had to be reoriented. These results suggest an interaction of arousal and orienting, at least in situations of maximally reduced activation when attentional asymmetries could be provoked even in healthy subjects. The findings are compatible with a right hemisphere dominance for alerting and orienting, and they are discussed in the light of theoretical accounts of visual orienting.

Different left brain regions are essential for grasping a tool compared with its subsequent use

Tool use engages a left hemispheric network including frontal, temporal and parietal regions. Patients with left brain lesions (LBD patients) exhibit deficits when demonstrating use of a single tool (apraxia). When attempting to use a tool, some apraxic patients show errors in the preceding grasping movement. Forty-two LBD patients and 18 healthy controls grasped individual tools and demonstrated their typical use. For patients with a tool use impairment (22), lesion analysis revealed a large area of overlap in the left hemisphere, mainly in the supramarginal gyrus (SMG). For patients with erroneous grasping (12), the lesion overlay showed overlaps in the left frontal and parietal cortices, especially in the inferior frontal gyrus (IFG) and the angular gyrus (ANG). However, contrasting lesions associated with impaired grasping versus tool use impairments reveal little overlap, limited to the inferior parietal cortex. Presumably the left IFG is involved in selection processes in the context of tool use, such as choosing a functional or non-functional grasping movement depending on the task and the online information about the tools structure and orientation. The ANG might provide this grasp related information, which is relevant for the specific action. The contribution of the SMG to tool use involves more general principals, such as integrating online and learned tool use information into the action plan for the use movement.

From pantomime to actual use: How affordances can facilitate actual tool-use

The main goal of the study was to investigate whether the presence of affordances, such as physical properties of given objects and resulting movement constraints, induce a performance increase in actual tool-use compared to demonstrating it with only the tool or pantomiming it without the tool and recipient object. In the present study the perception of affordances was manipulated by omission or supply of contextual information. The three execution modes - pantomiming, demonstration and actual use, - were investigated concerning the actions hammering and scooping in 25 patients with left unilateral brain damage and 10 healthy controls. The content of the movement, the grip formation, the direction and the location of the movement were evaluated with video-analysis. The results show that the pantomime condition is most prone to errors. The information given by the tool and the recipient object in the actual use task seems to facilitate especially scooping - the more complex tool-use action. A factor analysis and the high correlation between performance-scores show that the three execution modes of both actions have a major common factor. One possible joint commonality of the execution modes could be the nature of an action related working memory component, which is responsible for the recall and the integration of semantic information into a movement-plan. Additional analyses with a smaller group revealed a second factor, that might depict the online processing of spatial relationships of the hand, the tool and the recipient objects. The results indicate that performance improvement can be achieved by providing perceptual cues and reducing the degrees of freedom for the required action. It is concluded that manipulating affordances in a tool use context should be taken into consideration for future investigation of therapeutic approaches.

Management of attentional resources in within‐modal and cross‐modal divided attention tasks: An fMRI study

In the present study, we were interested in distinguishing the cortical representations of within‐modal and cross‐modal divided attention tasks by using functional magnetic resonance imaging. Sixteen healthy male subjects aged between 21 and 30 years underwent two within‐modal (auditory/auditory, visual/visual) and one cross‐modal (auditory/visual) divided attention task, as well as related selective attention control conditions. After subtraction of the corresponding control task the three divided attention tasks, irrespective of sensory modality, revealed significant activation in a predominantly right hemisphere network involving the prefrontal cortex, the inferior parietal cortex, and the claustrum. Under the cross‐modal condition, however, the frontal and parietal activation was more extended and more bilateral and there also was stronger right hemisphere activation of the anterior cingulate cortex and the thalamus. In comparison to the within‐modal conditions additional bilateral frontal and left inferior parietal activation was found for the cross‐modal condition. The supplementary fronto‐parietal, anterior cingulate cortex, and thalamus activation in the auditory/visual condition could be argued to reflect an additional demand for coordination of two ongoing cross‐modal cognitive processes. Hum Brain Mapp, 2007.

Bimanual coupling during the specification of isometric forces.

Abstractu2002The present study investigated the generalizability of the hypothesis of transient coupling during the preparation of bimanual movements (Spijkers and Heuer 1995) to the specification of isometric forces. In the first experiment we used the timed response paradigm (TRP) to examine the time course of the specification process. Subjects had to generate bimanual isometric force pulses while preparation time was controlled by the TRP. Target forces were weak (20% of maximal voluntary force, MVF) or strong (40% MVF) and assigned randomly to each hand. The first experiment revealed the predicted pattern of correlations between the peak forces but, because the subjects tended to delay responding when time for preparation was very brief, the time course of the specification process did not fully match expectations. In the second experiment we improved force–trajectory feedback and presented two initial cues that were expected to induce better preparation of the default force (30% MVF). Both changes were successful and the results further corroborate the transient-coupling hypothesis.

The relation between response-specificity, S-R compatibility, foreperiod duration and muscle-tension in a target aiming task

Three experiments are reported aiming at a further understanding of the effect of response-specificity, operationalized as the degree of commonality of direction of movements. In a previous study, Spijkers (1987) has claimed that response-specificity affects the readiness of the motor system and is not related to response-selection processes. These suppositions were generally confirmed in experiments 1 and 2 respectively. Common to both experiments were the variables average movement velocity and response-specificity. In experiment 1 the effect of the additional variable foreperiod duration was found to interact with that of response-specificity, hereby confirming its expected relation to the muscular system. The effect of response-specificity did not interact with that of spatial S-R compatibility in the second experiment, but also failed to show a main effect. The third experiment examined the supposed relation of response-specificity more directly through manipulation of the muscle-tension of the responding limb. The predicted form of the interaction between the effect of response-specificity and muscle-tension was confirmed which provided additional evidence for the interpretation of response-specificity effects in terms of differential muscular activation.

Fractioned reaction time as a function of response force

The relationship between fractionated reaction time components and response force was studied in a simple reaction time task. Subjects squeezed a force transducer between the right thumb and index finger. Three conditions with 5, 25, and 50% of the maximum voluntary isometric force were investigated in a counterbalanced order. The results showed that premotor reaction time was negatively related to peak force amplitude, while motor reaction time remained constant across force conditions. An interpretation of the effect on premotor reaction time in terms of a shift in the speed-accuracy trade-off function was refuted. Although the data were consistent with a two-stage programming model, it was concluded that differences in motor nerve fiber conduction velocity as a function of response force could explain the results obtained.

Parametric coupling and generalized decoupling revealed by concurrent and successive isometric contractions of distal muscles.

In two experiments we examined the hypothesis of transient parametric coupling during the specification of peak forces of isometric contractions produced by the left and right hand. In the first experiment participants had to produce bimanual contractions with same and different target forces as rapidly as possible in response to an auditory signal; target forces were cued visually with variable cueing intervals. At short cueing intervals reaction times were longer when different peak forces had to be specified than when same peak forces were cued, and this reaction-time difference declined as the cueing interval was increased. Independent of the cueing interval intermanual correlations of peak forces, rise times, and reaction times were smaller in conditions with different peak forces than in those with same peak forces. In the second experiment imperative signals for left-hand and right-hand contractions were separated in time. Target forces for the first response were cued with variable cueing intervals, while for the second response the cues were presented simultaneously with the second imperative signal. Reaction time of the second response was longer when target forces for the two successive responses were different rather than same, and this reaction-time difference declined when the delay of the second signal was increased as well as when the cueing interval for the first response became longer. These results are consistent with the hypothesis of a transient cross-talk between concurrent processes of peak-force specifications; in addition they indicate generalization of the decoupling required to specify different peak forces concurrently to the specification of temporal response characteristics and to processes of response initiation.

Development of neuropsychological functions of attention in two cultures: A cross-cultural study of attentional performances of Syrian and German children of pre-school and school age

We tested the development of attentional functions within Syrian and German children of pre-school and school age (n = 562, 5–12 years), using the Test of Attentional Performance for Children (KITAP). After controlling the intelligence (IQ) and socioeconomic status (SES), age-related improvements were found in all the attentional functions, with rapid improvements between 8 and 10 years. Gender differences were also found in some attention performances. More importantly, cultural differences were also evident. The performance in the activation functions “Alertness” and “Vigilance” were independent from cultural background, whereas performances in Sustained Attention, in functions of visuospatial orienting (Visual Scanning) and executive systems (Divided Attention, Flexibility and Distractibility) revealed cultural differences. In general, the Syrian children showed slower performances, higher variability of responses and more errors compared with German children. The overall results of the study supports the universal development of attention functions during school age, and show that attention performances could be influenced by characteristics of the cultural background (Arabic-Syrian: collectivistic–dependent; and Western German: individualistic–independent).

Development of attention functions in 5- to 11-year-old Arab children as measured by the German Test Battery of Attention Performance (KITAP): A pilot study from Syria

We administered the German Test-battery of Attention Performance (KITAP) to Arab children living in Syria (Nu2009=u2009143, 5–11 years) in order to assess the influence of age and gender on different dimensions of attention. The results demonstrate the validity of cross-cultural application of KITAP with Syrian school-aged children. The influence of age was more evident on speed of performance than on quality of performance, with rapid, general improvement until the age of 9 years. Some attention functions like alertness and inhibitory control seemed to be developed earlier than other functions like, flexibility, distractibility, and divided attention. Gender-related differences were observed in some subtests: Boys had faster reaction times but made more errors than girls. Interestingly, Arab-Syrian children showed better performance on some attention tests compared with German norms. The present study provides support for the use of cross-cultural studies for better understanding of the development of attention in school-aged children.