Biomedical subjects

Markus Hausmann

Publications and source records attributed to Markus Hausmann.

8 recordsLinked to original sources

PubMed2004

Influence of task complexity on manual asymmetries.

The degree of manual asymmetry is generally assumed to vary with task complexity. However, task complexity as a factor in manual asymmetries has rarely been examined directly. Further, the results of psychophysical studies indicate that manual asymmetry increases with task complexity, while physiological studies consistently report a reduction of manual asymmetries in more complex tasks. The use of different tasks (rather than different complexity levels within a given task) in many psychophysical studies might result in this inconsistency. This study investigated the influence of task complexity on manual asymmetries in 70 right-handed subjects. We used three complexity levels within a finger-tapping paradigm. A strong advantage of the preferred hand was particularly pronounced in the simple finger-tapping task. When the task was more complex, the advantage of the preferred hand, and thus, the manual asymmetry significantly decreased or disappeared. These results support previous suggestions that simple motor tasks involve localised neural networks confined to one cerebral hemisphere, while complex motor tasks are controlled by more widely distributed neuronal assemblies that involve both hemispheres. However, the influence of task complexity on manual asymmetry seems not to be monotonic.

Analysis of Variance↗

PubMed2003

Line bisection following hemispherectomy.

Two left- and right-hemispherectomized patients with contralateral hemianopia and 20 normal controls were administered a line bisection task. All hemispherectomized patients showed a strong bisection bias towards their blind visual field. This contralateral bias persisted when patients were forced to start scanning within their blind hemifield, supporting the idea of a strategic adaptation of attention towards the blind visual field. In all patients the hemispherectomy was performed as a result of cortical abnormality (congenital or acquired) and therefore early changes in functional cerebral organization may have occurred in these patients. The absence of a neglect-like ipsilateral bias and the presence of a hemianopic-like contralateral bias in line may represent a functional deficit or suggest that plastic changes following hemispherectomy induced an adaptive functional re-organization of spatial attention in both left- and right-hemispherectomized patients.

Adaptation, Physiological↗

PubMed2003

Line bisection in the split brain.

The authors examined line bisection in 4 patients with resection of the corpus callosum and in 22 control participants. The control participants showed a leftward bias, especially with the left hand, implying right-hemispheric dominance in spatial attention. Two patients with anterior callosotomy showed similar biases, suggesting that the anterior callosum plays only a small role. A patient with complete callosotomy showed a strong right bias, regardless of hand use. A patient with posterior callosotomy showed the opposite pattern: a strong left bias, regardless of hand use. These data suggest that the posterior corpus callosum normally plays a role in line bisection and that the resection of the posterior corpus callosum produces consistent bias. The direction of the bias depends on which hemisphere assumes control.

Adult↗

PubMed2003

Age-related changes in hemispheric asymmetry depend on sex.

A total of 92 participants, 50 younger (mean age 26.3 years) and 42 older (mean age 63.8 years), were tested for visual-field asymmetries. On a word-matching task, a right-visual-field (RVF) advantage increased with age, consistent with the theory that right-hemispheric function shows relatively greater decline with age than left-hemispheric function. On a figural-comparison task, a left-visual-field (LVF) advantage was marginally decreased with age in the men, but significantly increased in the women, probably because age-related changes in hormonal levels are more pronounced in women. This increase in LVF advantage is contrary to both the HAROLD theory that hemispheric asymmetry declines with age, and the theory of relative right-hemispheric decline.

Journal Article↗

PubMed2003

Developmental changes in line bisection: a result of callosal maturation?

Normal adults tend to bisect horizontal lines to the left of the objective middle, especially when using the left hand. This bias has been attributed to the dominance of the right hemisphere in spatial attention. The authors investigated the effect of hand use and line position in visual line bisection in right-handed children and adults, classified into 4 different age groups: 10-12, 13-15, 18-21, and 24-53 years (N = 98). All 4 groups showed the characteristic leftward bias when using the left hand. When using the right hand, the youngest group showed a rightward bias, whereas the other 3 groups all showed a leftward bias. This suggests a shift from contralateral to right-hemispheric control during puberty and may reflect maturation of the corpus callosum.

Adolescent↗

PubMed2002

Migraine and cognitive function: a life-course study.

OBJECTIVE: To investigate the association between migraine and cognitive ability among members of a longitudinal birth cohort study. METHODS: Headache status was determined at age 26 (migraine, tension-type headache [TTH], headache-free control subjects) according to International Headache Society criteria, and data relating to cognitive and academic performance from ages 3 to 26 years were analyzed. RESULTS: Study members diagnosed with migraine were subtly but significantly impaired, compared with those with TTH and headache-free control subjects, on tests of verbal ability (especially language reception) from ages 3 to 13, independent of headache history. Performance on other tasks, including reading, arithmetic, motor, and spatial ability, was normal. The association between migraine and verbal functioning also appeared to impact on later academic success. CONCLUSION: Findings suggest that the poorer verbal performance was unlikely to have resulted from cumulative attacks and may be due to developmental factors beginning in utero.

Adult↗

PubMed2002

Sex differences in line bisection as a function of hand.

If subjects are asked to indicate the midpoint of a horizontal line, they tend to bisect it left of the center, a phenomenon called 'pseudoneglect'. Assuming that this task evokes visuospatial processes, the left bias is generally considered to arise from a right-hemispheric activation. Numerous factors affect pseudoneglect. Although, only few studies have examined the influence of sex in visual line bisection, most of theses studies reported no significant main effect of sex. Possible interactions between sex and other performance factors that are linked to the motor component of this task, e.g. hand use, are rarely examined. We studied the interaction of these two variables using right-handed females and males in a line bisection task. The results clearly indicate that hand use and sex interact, with females showing the left bias to a similar extent with both hands while males show the bias predominantly with the left hand. Moreover, the position of the lines (left, middle and right) significantly affect left bias in visual line bisection and interact with hand use. It is hypothesized that the larger cross-section of the posterior corpus callosum in females enables a stronger interhemispheric connectivity of visuospatial cortical areas resulting in a strong left-sided bias in hand motor cortical areas of both hemispheres. In males, motor cortical activation would accordingly be mainly restricted to the right hemisphere.

Adult↗

PubMed2002

Functional cerebral asymmetries during the menstrual cycle: a cross-sectional and longitudinal analysis.

This study aims at answering two basic questions regarding the mechanisms with which hormones modulate functional cerebral asymmetries. Which steroids or gonadotropins fluctuating during the menstrual cycle affect perceptual asymmetries? Can these effects be demonstrated in a cross-sectional (follicular and midluteal cycle phases analyzed) and a longitudinal design, in which the continuous hormone and asymmetry fluctuations were measured over a time course of 6 weeks? To answer these questions, 12 spontaneously cycling right-handed women participated in an experiment in which their levels of progesterone, estradiol, testosterone, LH, and FSH were assessed every 3 days by blood-sample based radioimmunoassays (RIAs). At the same points in time their asymmetries were analyzed with visual half-field (VHF) techniques using a lexical decision, a figure recognition, and a face discrimination task. Both cross-sectional and longitudinal analyzes showed that an increase of progesterone is related to a reduction in asymmetries in a figure recognition task by increasing the performance of the left-hemisphere which is less specialized for this task. Cross-sectionally, estradiol was shown to have significant relationships to the accuracy and the response speed of both hemispheres. However, since these effects were in the same direction, asymmetry was not affected. This was not the case in the longitudinal design, where estradiol affected the asymmetry in the lexical decision and the figural comparison task. Overall, these data show that hormonal fluctuations within the menstrual cycle have important impacts on functional cerebral asymmetries. The effect of progesterone was highly reliable and could be shown in both analysis schemes. By contrast, estradiol mainly, but not exclusively, affected both hemispheres in the same direction.

Adult↗