Evidence Of Lateralization Research Articles

Regional distribution of [ 3H]MK-801 binding sites in the human brain

Specific [ 3H]MK-801 binding was measured under equilibrium conditions in 8 brain regions (frontal cortex, area entorhinalis, hippocampus, amygdala, putamen, thalamus, substantia nigra and nucleus dentatus) in the right hemisphere of the human brain ( n = 4). In addition, binding was assessed in 3 of these regions (frontal cortex, area entorhinalis and putamen) in the left hemisphere. High [ 3H]MK-801 binding levels occurred in the area entorhinalis, frontal cortex, hippocampus and amygdala, medium levels were observed in the putamen and thalamus and low levels were found in the substantia nigra and nucleus dentatus. No evidence for laterality of [ 3H]MK-801 binding sites was observed in the 3 regions which were investigated on both sides of the brain.

Hemispheric asymmetry and emotion: Effects of nonverbal affective stimuli

The purpose of the present study was to investigate the cerebral processing of affect by measuring the electroencephalographic activity of the frontal lobes and electrodermal activity in response to a series of nonverbal affective stimuli. Cognitive and sensorimotor processes were minimized by employing a design that did not require subjects to perform any task other than attending to the stimuli. Summated frontal alpha activity was determined during nonemotional, positive, and negative stimuli. Changes in bilateral skin conductance were also measured during the presentation of the stimuli. Results demonstrated that there was bilateral activation of the frontal lobes in response to the positive affective stimuli. The level of activation of the frontal lobes was the same in response to both negative and nonemotional stimuli. There was no evidence of hemispheric asymmetry or gender-related differences in patterns of activation. Furthermore, there was no evidence of lateralization in the skin conductance response magnitude.

Evidence of Laterality in the Lowland Gorilla

The description of hand preference in the primates is at present sadly incomplete. In the lowland gorilla the consistency of the dextral preference across all tests is amazing and comparable to the human data. Similar analysis of the behavior of the orang-utan and a reexamination of the chimpanzee might present a coherent picture of homologous behaviours for the hominoidea.

The use of an angiotensin II antagonist (saralasin) as an adjunct during renal vein catheterization.

Renal vein catheterization was performed in fifteen hypertensive patients with unilateral renal disease. Samples for measurement of plasma renin concentration were obtained from each of the two renal veins and from the femoral artery (or the inferior caval vein)-before and during saralasin infusion. Saralasin infusion induced a significant decrease in blood pressure. In ten patients with lateralization of renin secretion before infusion, saralasin induced a 2-fold increase of the renin gradient across the diseased kidney, whereas there was no significant renin gradient across the contralateral kidney neither before nor after saralasin infusion. Thus, the renal venous renin ratio (diseased/contralateral) increased from a mean value of 2.10 to 4.13. In five patients without lateralization of renin secretion prior to infusion, saralasin induced a significant increase of renin gradient across both kidneys. In consequence, evidence for lateralization did not emerge and the renal vein renin ratio remained unchanged at 1.10. In cases with lateralization of renin secretion, the use of saralasin provides confirmatory evidence for strictly unilateral renin secretion with suppression of renin output from the contralateral kidney. In patients without obvious lateralization of renin secretion before saralasin, the administration of this angiotensin II inhibitor can serve to demonstrate a potential renin for renin secretion, shared by both kidneys.

Opposite visual hemifield superiorities in face recognition as a function of cognitive style

Twenty-four women, classified as field dependent or field independent on the Rod-and Frame Test, memorized sets of upright and inverted faces and were then tested for recognition in a tachistoscopic visual hemifield paradigm using upright and inverted faces as probes. A significant triple interaction of probe orientation, visual hemifield and cognitive style was found. For upright probes, field independent subjects responded faster and more accurately when probes were in the left visual field; in contrast, field dependent subjects showed a right visual field advantage. For inverted probes, there was little evidence of lateralization. The findings are interpreted as reflecting a difference in the strategies used by these subjects for tachistoscopic face discrimination; however, this interpretation rests upona particular model of laterality effects.

OPPOSITE VISUAL HEMIFIELD SUPERIORITIES IN FACE RECOGNITION AS A FUNCTION OF COGNITIVE STYLE*

ABSTRACTTwenty‐four women, classified as field dependent or field independent on the Rod‐and‐Frame Test, memorized sets of upright and inverted faces and were then tested for recognition in a tachistoscopic visual hemifield paradigm using upright and inverted faces as probes. A significant triple interaction of probe orientation, visual hemifield and cognitive style was found. For upright probes, field independent subjects responded faster and more accurately when probes were in the left visual field; in contrast, field dependent subjects showed a right visual field advantage. For inverted probes, there was little evidence of lateralization. The findings are interpreted as reflecting different strategies used by these subjects for tachistoscopic face discrimination; however, this interpretation rests upon a particular model of laterality effects.

Lack of limb motor asymmetry in the neonate.

Neonates were examined for evidence of lateralization of motor function. The stepping test was done and the foot that moved first was recorded. The reaction of both arms to avoid an obstacle was also tested. No evidence for lateralization was found. Previous studies in the neonate have shown asymmetry of anatomical structures subserving language, and functional asymmetry of auditory functions and head position. However, the development of limb handedness occurs only at a later age.

Infantile stimulation induces brain lateralization in rats.

The hypothesis tested was that the effects of early experiences are asymmetrically distributed in the two brain hemispheres. Litters were either handled or not handled between birth and weaning, and the weanlings were reared in either laboratory cages or enriched environments between 21 and 50 days. When approximately 135 days old, animals within each of the four treatment groups had a right neocortical ablation, a left neocortical ablation, a sham operation, or no surgery. About 1 month later, all animals were given the open-field test for emotionality and exploratory behavior. Ablating either the right or left neocortex increased the activity scores of nonhandled controls, but there was no evidence of lateralization. However, the groups handled in infancy did show lateralization. Ablating the left brain did not significantly increase activity, but ablating the right brain caused extreme scores: handled rats without enrichment experience were the most active, and handled rats also placed into the enriched environment had near-zero scores in the open field.