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Biomedical subjects

U Tan

Publications and source records attributed to U Tan.

At least 91 records · Page 5Linked to original sources
PubMed1990

Lithium and imipramin effects on paw preference in cats.

The effect of lithium and imipramin on paw preference was studied in cats. Paw preference was assessed by the food-reaching test. It was found that lithium decreased, and imipramin increased the asymmetry of paw use. The lithium effect was antagonized by imipramin. It was concluded that paw preference may reflect a biochemical asymmetry in the brain. These effects of these psychoactive drugs may be of importance for the origin and treatment of affective disorders.

Animals↗
PubMed1990

There is a close relationship between hand skill and the excitability of motor neurons innervating the postural soleus muscle in left-handed subjects.

The claim that there is not a consistent inhibition of the H-reflex from the dominant leg was examined and rejected. It was re-established that there is an inverse relationship between hand skill and the excitability of motoneurons innervating the postural soleus muscle in left-handed subjects. In left-handers with significantly better left-hand skill, the height of the H-reflex recovery curve was significantly higher on the right leg (nondominant) than the left leg (dominant). There was a positive linear correlation between the asymmetries of hand skill greater than zero (better left-hand skill) and the H-reflex recovery curves from the right and left legs greater than zero (right dominance in reflex excitability). In left-handers with no significant difference between the right- and left-hand skills, there was no significant difference between the mean recovery curves from the right and left legs for the interstimulus intervals from 40 to 100 ms; the height of the left recovery curve was found to be significantly higher than the height of the right recovery curve for the interstimulus intervals from 150 to 1000 ms. It was concluded that there is close relationship between hand skill and motoneuronal excitability from right and left soleus muscle with regard to support and operative functions of legs in left-handers.

Adult↗
PubMed1990

Relation of hand performance and preference in male and female left-handers to familial sinistrality and writing hand.

The relations of hand performance to the degree of left-hand preference, and left- minus right-hand performance were studied in left-handed male and female subjects considering familial sinistrality and writing hand. Hand performance was assessed by a dot-filling test; hand preference was assessed by the Edinburgh Handedness Inventory. It was established that there were fundamental differences in relationships between performance and preference measures to sex, familial sinistrality, and writing hand, which also created different patterns in the relationships between hand performance and the difference in performance between hands.

Adult↗
PubMed1989

Nonverbal intelligence, familial sinistrality and left-handedness.

The interrelations among Geschwind scores, familial sinistrality, and nonverbal intelligence were studies in left-handed males and females. Nonverbal intelligence (spatial reasoning) was assessed by Cattle's Culture Fair Intelligence Test. Hand preference was assessed by the Edinburgh Handedness Inventory, and a laterality score (Geschwind score) was calculated for each subject. The mental ability for spatial reasoning was found to be related to the degree of the left-hand preference in conjunction with familial sinistrality. Moderate left-handedness was found to be advantageous for nonverbal intelligence. It was concluded that cognitive and motor functions are interrelated systems; the efficiency of the spatial reasoning would depend on the degree and developmental level of cerebral lateralization.

Adult↗
PubMed1989

Manual proficiency in Cattle's Intelligence Test in left-handed male and female subjects.

The relationship between nonverbal intelligence (spatial reasoning) and manual proficiency was studied in male and female left-handers. Manual proficiency was assessed by measuring the speed and accuracy in performing the dot-filling test. Nonverbal intelligence was assessed by Cattle's Culture Fair Intelligence Test. Females were found to be better than males in left-hand performance, and were more lateralized than males in manual proficiency. No significant sex difference could be established in right-hand performance. The right-hand skill was positively correlated to test intelligence (p less than 0.001). There was a negative correlation between the left- minus right-hand skill difference and the scores for nonverbal intelligence (p less than 0.001). The left-hand skill did not show any correlation with nonverbal IQ. It was concluded that the left-hemisphere is of utmost importance even for nonverbal intelligence; strong cerebral lateralization is disadvantageous for spatial reasoning.

Adult↗
PubMed1989

Right and left hand skill in left-handers: distribution, learning, and relation to nonverbal intelligence.

The relation of hand skill to nonverbal intelligence (spatial reasoning) tested by Cattle's Culture Fair Intelligence Test was studied in left-handed subjects. Hand skill was assessed by the peg moving test, which revealed that some of the left-handers (Geschwind scores and self-reports) were ambidexters. The distribution for right hand skill fitted to Gaussian data better than that for left hand skill. The R-L difference between the hands in peg moving times could also be described by normal distributions in the total sample, ambidexters, and left-handers. The right and left hands of ambidexters were as fast as the left-handers. In left-handers, the right hand was significantly slower than the left hand. In males, right-hand skill fitted to Gaussian data better than left-hand skill. In males and females, right and left-hand skill fitted to Gaussian data. Left-hand skill fitted to Gaussian data better in females than males. The difference between right- and left-hand peg-moving times was found to be larger in females than males. There was no significant difference between the right- and left-hand peg moving times of the male and female left-handers. The mean peg moving times for the right and left hands linearly decreased at each successive trial (N = 10). This motor learning was found to be better in left-handers with high IQs than those with low IQs. The right hand of left-handers with high IQs was faster than that with low IQs. The motor learning of the left hand was not different in left-handers with high and low IQs. The regression line for ambidexters exhibited less learning than that for left-handers. It was suggested that right hand skill is associated with nonverbal intelligence in left-handers, indicating the importance of left hemispheric processing in this kind of cognitive performance.

Adult↗
PubMed1989

The Hoffmann reflex from the flexor pollicis longus of the thumb in left-handed subjects: spinal motor asymmetry and supraspinal facilitation to Cattell's intelligence test.

The spinal motor asymmetry was studied in left-handers. Hand preference was assessed by Geschwind scores (GS), and hand skill by peg moving task, the reflex responses were recorded from the long flexor muscle of the thumb. The H-reflex could be elicited by averaging during cortico-spinal facilitation (voluntary isometric force). The Cattell's Culture Fair Intelligence Test was used to assess the individual differences in mental abilities. H-reflexes were found to be significantly larger on the left than the right side. The amplitude of H-reflex increased linearly with force applied to transducer by the thumb. This facilitation was more pronounced for the left than the right reflexes. Removal of the visual visual input caused facilitation in H-reflex (supraspinal disinhibition). Post-activation potentiation was also observed in H-reflex. There was a positive linear correlation between the degree of left-hand preference (-GSs) and left-hand skill. The correlation for the right-hand skill was not significant. There was a linear correlation between the degree of left-hand preference and the right minus left hand skill. There was an inverse correlation between left-hand skill and H-reflex from left. The correlation for the right side did not reach the 5% significance level. The force-reflex relation did not show any significant change to IQ for the right H-reflex. The left H-reflexes were significantly larger in subjects with high IQ than those with low IQ. The regression line and its slope for the force-reflex relation on the left was found to be higher in subjects with high IQ than those with low IQs. There was a positive linear relationship between IQ and H reflex from left. The correlation for the right side was not as pronounced as that for the left side. The left minus right H reflex was also positive linearly correlated with IQ. These results provide further evidence for the psycho-motor hypothesis (Tan. 1988b) as well as the spinal motor asymmetry to handedness. It was suggested that lateralization of cognitive and motor functions would be essential to create subjects with high psychomotor capacity.

Adolescent↗
PubMed1989

The H-reflex recovery curve from the wrist flexors: lateralization of motoneuronal excitability in relation to handedness in normal subjects.

Spinal motor asymmetry was studied in relation to handedness. Hand preference was assessed by Oldfield's Questionnaire and Geschwind scores. hand skill was evaluated by a peg moving task. The motoneuronal excitability was assessed by the size and recovery curve of the H-reflex elicited by stimulation of the right and left median nerves. H-reflex was recorded by cup electrodes placed over the wrist flexors. The mean reflex latencies from the right and left sides were 23.4 and 23.2 ms, respectively. The mean amplitude of the maximum H reflex was significantly higher on the right side than the left side in right-handers without familial sinistrality (FS). There were no significant side differences in the amplitudes of H-reflexes of the right-handers with FS. A genetic factor was suggested to involve this left shift of spinal motor lateralization in right-handers with FS. The recovery curve studies showed that the motoneuronal excitability was higher on the right than the left in right-handers without FS. There was no excitability difference between the right and left sides of the right-handers with FS. In left-handers, the motoneuronal excitability was significantly higher on the left than the right side. Voluntary flexions of the wrist increased the H-reflex especially on the right side of the right-handers. There was no relationship between this corticospinal facilitation and baseline EMG activity. The H-reflex amplitude was found to be inversely correlated with hand skill in right-handers. It was concluded that motoneuronal excitability is associated with handedness and also depends on FS. It was suggested that small reflexes are especially suitable in fine motor control of rapid aimed-movements, as the well-established relation between the size of motor units and fine motor control.

Adult↗
PubMed1989

Cerebral somatosensory potentials evoked by posterior tibial nerve stimulation: lateralization and relation to handedness in left-handed normal subjects.

Somatosensory potentials evoked by stimulation of the right and left posterior tibial nerves were studied in left-handed normal subjects. Hand preference was assessed by the Edinburgh Handedness Inventory; a laterality score (Geschwind score) was calculated for each subject. Hand skill was assessed by the peg moving task. The mean amplitude of the N1 wave from the right cerebral cortex was found to be significantly larger than that from the left cerebral cortex. In the subjects without familial sinistrality, there was no statistically significant difference between the evoked potentials from the right and left sides. In the subjects with familial sinistrality, the mean amplitude of the N1 wave from the right cerebral cortex was found to be significantly larger than that from the left cerebral cortex. There was an inverse relationship between the lateralization quotient (LQ) for the N1 wave and left-hand preference. The amplitudes of the P1, N1, and P2 waves from the right cerebral cortex were positively linearly correlated with left-hand preference. There was an inverse relationship between LQ for the P1 and N1 waves and the right-hand skill. The left-hand skill was not correlated with LQ for the evoked potential. The LQs for the P1 and N1 waves were negatively linearly correlated with the difference between the right and left hand skills (right minus left peg moving times). The amplitudes of the P1 and N1 waves from the left cerebral cortex were found to be inversely related to the right hand skill. There was no relationship between the evoked potential amplitudes from the right cerebral cortex and left hand skill in the total sample. It was concluded that the stronger sensory feedback for the somatomotor foot area within the right cerebral cortex would contribute to left-footedness in left-handers; the asymmetric organization of the somatosensory potentials evoked by stimulation of the right and left PTNs correlates with hand preference and skill, but in an unexpected manner.

Adult↗
PubMed1988

The distribution of hand preference in normal men and women.

The distributions of the hand preferences (Geschwind scores) were studied in men and women. The incidences of the right-, mixed-, and left-handers were 66.1, 30.5, and 3.4%, respectively. The left- and right-handers (LHs, RHs) were represented by two bars located at the opposite ends of a J-shaped histogram for the total sample, men, and women. The distributions for the total RHs, and male RHs were not J-shaped, but negatively skewed, the mode being close to the mean. The frequencies for the females increased linearly. The distributions for the LHs did not significantly deviate from normality. Except for the LHs, the percentage distributions of the Geschwind scores were J-shaped. The LHs were evenly distributed by chance to be expected in a random sample from a rectangular population. The incidence of weak right-handedness was significantly higher in men than women. The total RHs were more lateralized than the total LHs who showed a tendency toward weak left-handedness. In males, the incidence for weak left-handedness was significantly higher than that for strong left-handedness. The opposite was established for females. The probability of the consistent right-handedness was significantly higher in women than men. The LHs were less lateralized, and more widely dispersed than the RHs. The statistical analysis of the distributions indicated that females tended to be more lateralized, i.e., more right-handed, and more left-handed, than males.

Adult↗
PubMed1988

The distribution of the Geschwind scores to familial left-handedness.

The principal objective of this work was to study the influence of the familial sinistrality (FS) on the distribution of the hand preference in males and females. The hand preference was assessed by the Oldfield's questionaire. The distributions of the Geschwind scores were compared in the subjects without and with FS. The strong right-handedness was reduced; the strong left-handedness was accentuated under the influence of FS. This left shift in the hand preference presumably inherited by a left shift factor was more pronounced in males than females. It was tentatively suggested that the subjects with FS might be better in mathematics than the subjects with no FS.

Adult↗
PubMed1988

The relationship between nonverbal intelligence, familial sinistrality and Geschwind scores in right-handed female subjects.

I proposed that there might be a strong relationship between the psychological and motor systems, and argued that hand preference could be related to intelligence; higher IQs are to be expected in right-handers with familial sinistrality (FS) than without FS (Tan, in press). This hypothesis was tested in this work. Cattle's Culture Fair Intelligence Test was used to assess the ability of spatial reasoning in right-handed females. Hand preference was assessed by the Edinburgh Handedness Questionnaire; a laterality score (Geschwind score) was calculated for each subject. The sample from the Nursery High-school had a significantly lower mean IQ than that from the Medical Faculty. The incidence for the consistent right-handers was significantly higher in the sample with lower mean IQ than that with higher mean IQ. The incidence for the weak right-handers was significantly higher in the sample with higher mean IQ than that with lower mean IQ. The incidence for familial sinistrality was significantly higher in the sample with higher mean IQ than that with lower mean IQ. It was concluded that handedness, familial sinistrality, and intelligence are interrelated traits; an attenuation in cerebral asymmetry as a result of an increase in the right hemisphere's mental abilities, reflecting itself in weak right-handedness in conjunction with FS, could be a prerequisite for well-developed nonverbal intelligence.

Adult↗
PubMed1988

The relationship between nonverbal intelligence and Geschwind scores in left-handed subjects.

Under psycho motor hypothesis, the relationship between left-handedness and nonverbal intelligence was studied in left-handed male and female subjects. Handedness was assessed by the Edinburgh Handedness Questionnaire; Geschwind scores (GS) were calculated for each subject. A GS of - 100 indicated consistent left-handedness. Spatial reasoning (nonverbal intelligence) was assessed by the Cattle's Culture Fair Intelligence Test. In the male and female subjects, the IQs increased for GSs from weak up to moderate left-handedness (GSs: -5 to -60), and decreased from moderate up to strong left-handedness (GSs: -60 to -100) linearly; the regression coefficient were found to be statistically significant. Weak-, and strong left-handedness both were associated with lowest scores; the highest scores were found in the subjects with moderate left-handedness (GSs: -55 to -65). It was concluded that the prerequisite for well-developed spatial reasoning should be two-sided development of the brain instead of one-sided dominance, and well functioning parallel processing between two cerebral hemispheres.

Adult↗
PubMed1988

Modulation of the somatosensory evoked potentials by the input information originating from the gastrocnemius and sural nerves in the dog.

Input-output characteristics of the somatosensory system were studied in the dog. Somatosensory evoked potentials were recorded from the scalp at stimulations of the sural and gastrocnemius nerves. There was a sigmoid relationship between the stimulus strength and the amplitude of the sural nerve action potential, which was best described by a logistic equation. The early waves (P1, N1) increased especially at low threshold stimulations of the sural nerve; then they remained either unchanged or decreased at high threshold stimulations within the Group II and III ranges. The late waves (P2, N2) especially increased at high threshold Group II stimulations of the sural nerve, and increased further at strong stimuli. Similar changes were observed at stimulations of the gastrocnemius nerves. The attenuation of the early waves was explained by "gating" mechanisms acting from the sensorimotor cortex onto the sensory relay nuclei. The increase of the late waves at especially high threshold Group II and III stimulations was accounted for by the multisynaptic diffuse projection from the reticular formation and/or the nonspecific thalamic nuclei to the somatosensory cortex. In a three weeks old pup, stimulation of the gastrocnemius nerves evoked somatosensory responses with similar morphology observed in adult dogs, but the latencies of the evoked potential components were relatively long, presumably as a result of the uncompleted myelination in the somatosensory afferent system.

Animals↗
PubMed1987

Allometry and asymmetry in the dog brain: the right hemisphere is heavier regardless of paw preference.

The allometric relationship between brain and body size and asymmetry in the weight of the cerebral hemispheres were studied in dogs. A regression analysis of the brain versus body weight revealed an allometric relationship according to the power function Y = kXa. The right cerebral hemisphere was found to be significantly heavier than the left. This finding was not associated with paw preference. In accordance with previous studies, it was concluded that the right-biased asymmetry in the weight of the cerebral hemispheres may be a common feature of the mammalian brain. Functional implications of the results were discussed with regard to the right hemisphere specializations.

Animals↗