Biomedical subjects

G Thut

Publications and source records attributed to G Thut.

22 records · Page 2Linked to original sources

PubMed1997

What is the role of the corpus callosum in intermanual transfer of motor skills? A study of three cases with callosal pathology.

Intermanual transfer for a skilled motor task was studied in two patients with total callosal agenesis, and one with an acquired partial callosal lesion and clinical evidence for disturbed transfer of motor signals. Patients had to draw meaningless figures with one upper extremity (original learning, OL) and to reproduce their mirror-reversals thereafter with the other side (transfer learning, TL). Both directions of intermanual transfer were tested in two conditions, that is, between either proximal or distal muscle groups. Transfer was evaluated by comparing OL and TL performance at the same effector. The main variable of interest was movement time during the first eight trials of OL and TL. All three patients displayed a significant benefit for transfer from the dominant to the non-dominant hand but not vice versa during proximal motor activity. When compared with the performance of healthy subjects tested in almost identical conditions in a previously reported study, the proximal transfer behavior was found to be similar for all patients and the normal group. Although patients exhibited no significant benefit for distal transfer, their non-dominant-to-dominant distal transfer was above the normal range. The similar transfer pattern of the patients and healthy subjects when using proximal musculature suggests that proximal transfer may be subserved by identical extracallosal pathways, most probably by the ipsilaterally descending motor systems. Since non-dominant-to-dominant distal transfer was found to be disadvantageous in healthy subjects, the patients' relative superiority in this condition may reflect missing callosal influences of an inhibitory nature.

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PubMed1997

Intermanual transfer of training: blood flow correlates in the human brain.

In a previous study, we found that relearning of a task with one hand might negatively be influenced by previous, opposite hand training of the analogue task, Thut G., et al., Exp. Brain Res., 108 (1996) 321-327. Drawing of a figure with the right hand, following left hand training, was slower than right hand drawing of an unknown figure. These conditions were termed right hand transfer learning (rTL) and right hand original learning (rOL). The present study aimed to identify the cerebral areas associated with these influences by measuring regional cerebral blood flow (rCBF) in 16 right-handed, healthy subjects during rTL and rOL. Positron emission tomography and statistical parametric mapping were used. Compared with rOL, rTL was associated with increased rCBF in the left medial prefrontal cortex and the right prefrontal convexity. Individual rCBF changes in the area homotopic to the right prefrontal convexity furthermore correlated with individual changes in rTL performance. While the smallest rCBF increases were found in subjects with weakest slowing of rTL relative to rOL, highest rCBF increases were present when rTL slowing dominated. Comparisons between rTL and rOL, however, revealed on average no performance differences. Our data suggest that relearning after previous opposite hand training activates neural mechanisms within the prefrontal convexity which might have an inhibitory function but that inhibition does not have to be the net final behavioral result.

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PubMed1996

Intermanual transfer of proximal and distal motor engrams in humans.

We studied intermanual motor transfer for right-to-left or left-to-right direction of transfer between either proximal or distal upper extremity muscle groups. The influence of previously acquired motor engrams (original learning, OL) on learning efficiency of the contralateral side (transfer learning, TL) was examined in 26 right-handed healthy subjects. The task consisted of the drawing of meaningless figures. During TL, OL figures had to be reproduced as vertical mirror reversals. Data revealed a benefit for right-to-left but not left-to-right direction of transfer for time to complete a figure as well as a left-to-right transfer benefit for spatial motor precision. Furthermore, a benefit for intermanual transfer of training between proximal but not distal muscle groups was found when movement time to complete a figure was evaluated. Of special interest was the observation of a disadvantage due to prior contralateral learning for performance at right distal effectors. The asymmetrical transfer benefits with respect to side are in line with previous findings and support the proficiency model and the cross-activation model. Results further showed that intermanual transfer of training might differ with respect to muscle group involvement and suggest that, although primarily facilitating, previous opposite hand training may lead to inhibitory influences on subsequent contralateral reproduction.

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PubMed1992

Twenty-four-hour monitoring of heart rate, motor activity and smoking behavior including comparisons between smokers and nonsmokers.

The present study was an attempt to monitor continuously and in parallel cigarette consumption, heart rate, and physical activity under field conditions. In a first experiment the test-retest reliability of the recording devices was evaluated with a small number of nonsmoking students on days with similar schedules. The intraday development of heart rate and activity revealed a remarkable intraindividual stability, and the test-retest reliability coefficients calculated between the totals of heart rate and activity revealed values of 0.73 and higher for heart rate and 0.47 and higher for activity on comparable days. The second experiment was done with housewives as subjects to see whether heart rate and/or activity might differentiate smokers from nonsmokers in subjects who are less strictly bound to a fixed daily work program. The smoker/nonsmoker comparisons revealed significantly higher heart rates for smokers but almost identical activity readings. In a third experiment it was tested whether partial smoking abstinence in the morning might differentiate the morning and afternoon heart rates in smokers. Heart rate but not activity was significantly decreased during the abstinence period. Taken together, the simultaneous monitoring of heart rate and activity might be a valuable instrument in smoking research, since it is sensitive enough to detect manipulations of the smoking behavior under natural conditions.

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