Biomedical subjects

U Tan

Publications and source records attributed to U Tan.

144 records · Page 8Linked to original sources

PubMedDate not supplied

Hoffmann reflex from foreleg flexor nerves in cats: lateralization, picrotoxin, strychnine, crossed flexor reflex.

Hoffmann (H) reflexes from foreleg flexor nerves were studied in cats. The right and left flexor nerves were stimulated and H reflexes were recorded from the same nerves. Paw preference was assessed by a food reaching test. Stimulation of the right median nerve elicited mono- and polysynaptic reflexes from the left ulnar nerve (crossed flexor nerve). Picrotoxin depressed, and strychnine increased H reflexes from both sides without affecting the spinal motor asymmetry. H reflexes were found to be larger on the left than the right side in right-preferent cats and vice versa in left-preferent cats. The right H-reflex recovery curve was higher than left in right-preferent cats. The inhibitory period of the recovery cycle disappeared after picrotoxin and changed to facilitation for the nonpreferred side. Strychinine caused bilateral, nearly-synchronous motoneuronal discharges from the right and left flexor nerves; the discharges originating from the left side preceded those from the right side in a right-preferent cat. These results indicate that spinal motor activity predominates on the nonpreferred side, which would be a prerequisite for postural adjustments during paw use in cats. This asymmetric motor organization in the forelegs of cats having quadrpedal locomotion seems to be similar to asymmetric motor organization in legs in humans.

Animals↗

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The effects of testosterone on paw preference in adult cats.

The effects of testosterone on paw preference assessed by a food reaching test was studied in adult cats. It was found that tetosterone propionate injected intramuscularly reduced the degree of the right-paw preference in right-preferent female cats. The paw preference of the male cats and left-preferent female cats was not affected by this male sex hormone. It was concluded that testosterone may especially suppress the left brain to induce ambilaterality in right-paw preference in adult female cats.

Animals↗

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Asymmetrical relationships between the right and left heights of the sylvian end points in right- and left-pawed male and female cats: similarities with planum temporale asymmetries in human brain.

Asymmetry in the height of the right (R) and left (L) Sylvian end points was studied in right- (RH) and left-pawed (LH) male and female cats. Sylvian height was described relatively to brain weight. An asymmetry coefficient (AC) was estimated (R - L/.5*R + L). There was no significant relationship between R + L Sylvian height and AC, in the total sample and in AC- (leftward asymmetry) brains. In AC+ brains (rightward asymmetry), R + L Sylvian height showed an inverse correlation with AC in RH cats, and a direct correlation in LH cats. There was an inverse correlation between left Sylvian height and AC in RH cats, but no correlation in LH cats. There was a direct correlation between right and left Sylvian height and AC. In AC- brains, left Sylvian height had no relation to AC, but there was a direct correlation between right Sylvian height and AC. In AC+ brains, left Sylvian height showed an inverse correlation with AC in RH males and females; a direct correlation only in LH male cats. Right Sylvian height showed a direct relation to AC+ values in RH and LH males and LH females (no correlation in RH females). The results supported the generalization that a brain symmetrical in a given region has more combined cortex than a brain that is asymmetrical for this region, only for RH cats, however (Galaburda et al., 1987).

Animals↗

PubMedDate not supplied

Inverse correlation between right-paw use and body weight in right-pawed male cats and left-pawed female cats.

The association between paw preference and body weight was studied in cats. In right-pawed males, the right minus left (R-L) paw use significantly decreased as the body weight increased. There was no significant correlation between these parameters in left-pawed males as well as in right-pawed females. In left-pawed females, the frequency of the left-paw use increased as the body weight increased. These results partly supported those in humans (Tan, in press). It was suggested that hormonal factors affecting body weight may also influence cerebral lateralization and consequently paw preference. The best possibility for these hormones appears to be testosterone.

Animals↗

PubMedDate not supplied

Relation of nonverbal intelligence assessed by Cattell's Culture Fair Intelligence Test to latencies of the somatosensory evoked potentials elicited by stimulation of the posterior tibial nerves in right-handed male and female subjects.

The association of nonverbal intelligence (NVI) with latencies of the somatosensory evoked potentials from the right and left posterior tibial nerves (PTNs) was studied in right-handed male and female subjects without familial sinistrality (FS-). There was a significant negative linear correlation between N49-P39 interpeak latencies from the right and left PTNs in females and a significant positive linear correlation between these parameters in males. There was no significant correlation between P58-N49 interpeak latencies and NVI in females, but a significant negative linear correlation in males. The N76-P58 interpeak latencies were found to be positively linearly related to NVI only in females; there was no correlation between these parameters in males. There was no significant correlation between IQ and side differences in SEP latencies in females. The right minus left P39 latencies from the right and left PTN were found to be negatively linearly related to IQ in males. In females with nearly equal heights, latencies of N49 waves were found to be negatively linearly related to IQ. In males with nearly equal heights, only P39 and P58 waves from the right PTN were found to be negatively linearly related to IQ. These results did not support the hypothesis of speed of information processing by the brain in behavioral intelligence. An asymmetrical organization of the male brain seems to be disadvantageous for nonverbal intelligence; the female brain appeared to be independent of the degree of asymmetrical organization of the brain in this respect.

Adult↗

PubMedDate not supplied

Right and left hand skill in relation to cerebral lateralization in right-handed male and female subjects: the prominent role of the right brain in right-handedness.

The associations between right and left hand skills to cerebral motor lateralization were studied in right-handed subjects with (FS+) and without (FS-) familial sinistrality. Hand preference was assessed by Oldfield questionnaire and hand skill by the peg moving task. The mean peg moving times (PMTs) and their standard deviations (SDs) were calculated for each hand. There was a significant positive linear correlation between the mean right and left hand PMTs. In males, the mean difference between the left and right PMTs (L-R) showed a significant negative linear correlation with the mean right hand PMTs. There was no significant correlation between these parameters in females. The mean L-R PMTs were found to be positively linearly correlated with the mean left hand PMT in FS- males, FS- and FS+ females (no correlation in FS+ males). The results indicated the contribution of the mean left hand PMTs to L-R hand skill is much higher than that of the mean right hand PMTs. In males, there was no significant correlation between SDs of the mean right and left hand PMTs. In females, SD of the mean right hand PMT was found to be positively linearly related to SD of the left hand PMT. In males, L-R SDs were found to be negatively linearly related to SDs of the mean right hand PMTs and positively linearly related to the SDs of the mean left hand PMTs. In females, only the mean left hand PMT positively linearly correlated with L-R SDs. Here again, the left hand prominently influenced the L-R SDs. In males, SD for the mean right hand PMT showed no relation to right hand PMT. There was, however, a negative linear correlation between SD of the mean right hand PMT and the left hand PMT (no correlations in female). It was concluded that the left hand (right brain) would be of higher significance than the right hand (left brain) in determining the degree of the right-bias in hand skill and its stability in right-handers.

Adult↗

PubMedDate not supplied

There is a direct relationship between nonverbal intelligence and serum testosterone level in young men.

It was confirmed that there is a direct relationship between serum testosterone level and nonverbal intelligence (Cattel's Culture Fair Intelligence Test) only in right-handed male subjects without familial sinistrality (FS-), with right eye preference. There was no significant correlation between these variables in young women and young men with mixed eye preference. It was concluded that testosterone would be an important factor which affects cognitive development in men.

Adolescent↗

PubMedDate not supplied

The relation of hand preference to hand performance in left-handers: importance of the left brain.

The associations among hand preference, hand skill (peg moving time, PMT) and hand performance (dot filling/20 s) were analyzed in left-handed subjects. In the total sample, the degree of left-hand preference linearly decreased from -100 to zero (Geschwind scores, GSs) as the number of dots placed by the right hand increased (direct correlation); the left hand did not show any significant relation to GSs. The right-hand PMT linearly decreased as the GSs decreased (negative linear correlation); the left hand skill did not exhibit any significant correlation with GSs. There was a negative linear correlation between right-hand PMT and dot-filling with right hand; the left-hand PMT was not related to dot-filling with left hand. In males, the right-hand PMT showed a negative linear correlation with GSs; no significant correlation between PMT and GSs was found for the left hand. There was a negative linear correlation between right minus left (R - L) PMT and GSs. Dot-filling with right hand was found to be positively linearly correlated with GSs (no correlation for the left hand). The L - R dot-filling showed a negative linear correlation with GSs. PMT for the right hand exhibited a significant negative linear relation to dot-filling only with right hand. Sex and familial sinistrality caused minor changes in these relationships. It was concluded that the left brain would constitute the main factor determining the degree of left-handedness.

Adult↗

PubMedDate not supplied

Contributions of the right and left brains to manual asymmetry in hand skill in right-handed normal subjects.

The relation of intermanual difference in hand skill to cerebral lateralization was studied in right-handed male and female subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. Hand skill was measured by the peg moving task. In subjects with familial sinistrality (FS+), the mean right hand peg moving times (PMTs) were found to be significantly and negatively linearly correlated with the mean left minus right (L - R) hand PMTs in females (no correlation in males). Contrarily, there was a direct relationship between the mean L - R hand PMTs and the mean left hand PMTs in FS+ males (no correlation in FS+ females). Similar results were obtained with the FS- subjects. The correlations were modified by eye and foot preferences. The overall results suggested that generally the right brain in males and the left brain in females are of importance in determining the intermanual difference in hand skill; an insufficient right brain (a slower left hand) in males and a sufficient left brain (a faster right hand) in females would create a more asymmetrical organization in skill between hands.

Adult↗

PubMedDate not supplied

Dependence of intermanual difference in hand skill on right or left cerebral motor control in right-handed male and female subjects.

The relations of the mean differences in right and left hand skills (L-R) to the mean right and left hand skills were studied in right-handed male and female subjects with and without familial sinistrality (FS+, FS-). Hand skill was measured by the peg moving task. In FS+ males, there was a significant negative linear correlation between L-R and right hand peg moving times (PMTs). In FS+ females, there was a significant positive linear correlation between L-R and left hand PMTs. There were no significant correlations between L-R and left hand PMTs in FS+ males, and right hand PMTs in FS+ females. FS- subjects could be described as follows. In males and females with right eye and right foot preference, L-R PMTs were found to be positively linearly correlated with left hand PMTs (no correlation between L-R and right hand PMTs). In subjects with left eye and right foot preference, the correlations were found to be similar to those for FS+ subjects. In subjects with mixed eye and right foot preference, there was a negative linear correlation between L-R and right hand PMTs in females; a positive linear correlation between L-R and left hand PMTs in males. There were no significant correlations between L-R and right hand PMTs in males, and left hand PMTs in females. These results indicated that left brain in FS+ males, and right brain in FS+ females would produce the L-R difference between hands in PMTs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Motor stability in visuomotor control of repetitive hand movements and its differential cerebral control in right-handed subjects.

The stability of asymmetric motor control was studied in right-handed subjects. Hand skill was assessed by a peg moving task in ten trials. The mean peg moving time (PMT) and its standard deviation (SD) were calculated for each hand. Standard deviation was taken as an index of the stability of visuomotor control. The mean rate of a repetitive movement (mean PMT) did not always show an association with its stability (SDs). This depended upon familial sinistrality, sex, and cerebral lateralization such as eye and foot preferences of the subjects. The left-right differences in movement stabilities also showed different contributions of the right and left brains of the subjects depending upon these factors. It was suggested that these factors should be taken into consideration in studies concerning the hemispheric control of especially corrective components of skilled movements of hands.

Adult↗

PubMedDate not supplied

Relationships among nonverbal intelligence, hand speed, and serum testosterone level in left-handed male subjects.

The relationships among nonverbal intelligence, hand speed, and serum testosterone level were studied in male left-handers ranging in age from 17 to 19 years. Hand speed was measured by a peg moving task. To assess the differences between nonverbal IQs. Cattell's Culture Fair Intelligence Test was used. There was a direct correlation between IQ and testosterone. IQ increased linearly with right-hand speed, which was directly related to testosterone. There was no significant correlation between IQ and left-hand speed, which was not significantly correlated with testosterone. IQ decreased with left- minus right-hand speed, which also decreased with testosterone. It was suggested that nonverbal spatial reasoning ability may be directly associated with the efficiency of left brain, which is favored by testosterone in male left-handers. It was also concluded that the left to right asymmetry in hand speed may depend on efficiency of the right brain in left-handed males.

Adolescent↗

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Inverse relationship between nonverbal intelligence and the parameters of pattern reversal visual evoked potentials in left-handed male subjects: importance of right brain and testosterone.

The relationships between latencies of visual evoked potentials (VEPs) and nonverbal intelligence test scores (IQs from Cattell's Culture Fair Intelligence Test) and correlations between serum testosterone level and VEP latencies were studied to examine the neural speed hypothesis of intelligence and its hormonal mechanisms in left-handed male subjects (Geschwind Scores). In accordance with the speed theory of intelligence, N1 and P1 latencies (and amplitudes) were found to be inversely related to IQ. However, this was true only for the right brain; the left brain did not contribute to this relationship. There was an inverse relationship between serum testosterone level and P1 latency; left minus right N1 latency, depending on N1 latency from right brain, linearly increased with testosterone. It was concluded that nonverbal intelligence largely depends on speed of information processing only by the right brain, not by the left brain in left-handed male subjects. This may have been created by testosterone in these subjects. Inconsistencies in the IQ literature concerning the speed hypothesis of intelligence may be explained by differences in cerebral lateralization.

Adolescent↗

PubMedDate not supplied

The relationships between paw preference and the right- and left-brain weights in male and female adult cats: ipsilateral and contralateral motor control with regard to asymmetric postural and manipulative actions.

Paw preference (food reaching) with regard to relative right-and left-brain weights was studied in adult cats. In the right-pawed (RH) male and female cats, the right-paw use increased and the left-paw use decreased with increasing asymmetry coefficient (AC) for the right- and left brain-weight. The right-paw use increased with increasing the right-brain weight in RH males, and decreased with increasing the left-brain weight in RH females. There was no significant correlation between paw use and AC in left-pawed (LH) males; the right-paw use decreased and the left paw use increased with increasing AC in LH females. The right-paw use decreased with increasing left brain weight (no correlation with right brain) in LH males. In LH females, the right-paw use decreased with the right-brain weight, and increased with the left-brain weight. The left-paw use increased with the left-brain weight in LH males (no correlation with the right-brain weight). The left-paw use increased with the right-brain weight and decreased with the left-brain weight in LH females. These results were explained by supraspinal and spinal reciprocal interactions between the postural and manipulative systems with regard to contralaterality and ipsilaterality of motor control in cerebral and manual lateralization.

Animals↗

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Relationships among weights of right and left cerebral hemispheres, and right minus left brain weight in right- and left-pawed male and female cats: importance of body weight.

Interrelationships among the right- (R), left- (L) brain weights, R-L brain weight, and R + L brain weight were studied in adult cats. The raw brain weights and the brain weights relative to body weight (brain weight: body weight) were studied separately. The raw R-L brain weight showed no significant correlation with the raw R+L brain weight. The relative R-L brain weight was found to be positively linearly correlated with the R + L brain weight only in the right-pawed (RH) males. So, the asymmetry in relative brain weight increased with the relative total brain weight only in RH males, suggesting a common factor favoring an asymmetrical brain and an increased body weight (testosterone). The relative R- and L-brain weights were found to be inversely related to the relative R-L brain weight only in the RH female cats with R-L brain weight smaller than zero (testosterone in males, estrogen in females). It was concluded that hormonal factors influencing the body weight may also influence the asymmetrical brain development in cats.

Animals↗

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Tremor-bursts induced by a combined application of chlorpromazine and pentobarbital in guinea pigs are asymmetrically influenced by right- and left-brain lesions.

The effect of right- and left-brain lesions on pentobarbitone-chlorpromazine induced tremor-bursts was studied in guinea pigs. The left-brain transections did not affect these tremor bursts except post-thalamic sections, which caused a complete disappearance of extensor jerks with coinciding tremors at four legs. These tremor bursts simultaneously occurring at four legs completely disappeared after a right-forebrain transection at the level of the rostral striatum. Extensor jerks without tremors continued to occur, however. It is concluded that the postural system is asymmetrically controlled and the rostral right brain is responsible for the tonic postural activity in guinea pigs.

Animals↗

PubMedDate not supplied

Grasp-reflex strength from right and left hands in relation to serum cortisol level and fetal position in human neonates.

The grasp-reflex strengths from right (R) and left (L) hands were studied in human neonates in relation to serum cortisol levels and fetal position. In males with right-ear out, there was no correlation between grasp-reflex strength from right hand and cortisol. The grasp-reflex strength from left hand significantly decreased as cortisol increased linearly in these subjects. In males with left-ear out, the grasp-reflex strengths from right and left hands were found to be negatively linearly correlated with serum cortisol level. In females with right-ear out, the grasp-reflex strength from right hand was not significantly correlated with cortisol, but grasp reflex from left hand linearly decreased as cortisol increased. In females with left-ear out, only the grasp reflex from right hand linearly increased with cortisol. Only in males with right-ear out, the R-L grasp-reflex strength linearly increased from left dominance toward right dominance. It was concluded that the stress hormone cortisol may be disadvantageous and/or advantageous for the prenatal development of the right and left brain according to fetal position; cortisol may also affect the emergence of cerebral lateralization.

Embryonic and Fetal Development↗

PubMedDate not supplied

Human growth hormone may differentially influence the grasp reflex in human neonates on the basis of genetically predetermined neural pattern of brain organization in utero.

The relations of the grasp-reflex strengths from right (R) and left (L) hands to human growth hormone (hGH) levels were studied in human neonates within the first day after birth. In right-handed (RH) males without familial sinistrality (-FS), grasp reflex from right and left hands directly correlated with hGH. In RH, -FS females, grasp reflex from right and left hands inversely correlated with hGH. In -FS, LH males, grasp reflex from right and left inversely correlated with hGH (no significant correlations in LH, -FS females). The R-L grasp reflex decreased linearly with hGH, only in RH, -FS males. These results indicated that hGH may affect cerebral development according to genetically predetermined neural patterns in utero.

Brain↗