#Human brain mapping sci journal full#

In particular, the larger the brain of a species, the greater the fraction taken up by the cortex. When the mammalian brain increases in size, not all parts increase at the same rate. The encephalization quotient for humans is approximately 4.6.

A standard formula for assessing an animal's brain size compared to what would be expected from its body size is known as the encephalization quotient.

Predators tend to have relatively larger brains than the animals they prey on placental mammals (the great majority) have relatively larger brains than marsupials such as the opossum. Primates, for a given body size, have brains 5 to 10 times as large as the formula predicts. This power law formula applies to the 'average' brain of mammals taken as a whole, but each family (cats, rodents, primates, etc.) departs from it to some degree, in a way that generally reflects the overall 'sophistication' of behavior. The explanation for an exponent of 0.75 is not obvious however, it is worth noting that several physiological variables appear to be related to body size by approximately the same exponent - for example, the basal metabolic rate. There are good reasons to expect a power law: for example, the body-size to body-length relationship follows a power law with an exponent of 0.33, and the body-size to surface-area relationship a power law with an exponent of 0.67. Averaging brain weight across all orders of mammals, it follows a power law, with an exponent of about 0.75. The relationship is not proportional, though: the brain-to-body mass ratio varies. An elephant's brain weighs just over Template:Convert/LoffAonDbSoff Template:Convert/test/Aon, a bottlenose dolphin's Template:Convert/to Template:Convert/test/Aon, whereas a human brain is around Template:Convert/to Template:Convert/test/Aon.Д«rain size tends to vary according to body size. The largest brains are those of sperm whales, weighing about Template:Convert/LoffAonDbSoff Template:Convert/test/Aon. The results suggested that cellular phones may reversibly influence the human brain, inducing abnormal slow waves in EEG of awake persons.See also: Cetacean intelligence#Brain size We observed similar changes in children, but the slow-waves with higher amplitude appeared earlier in children (10-20 s) than adults, and their frequency was lower (1.0-2.5 Hz) with longer duration and shorter intervals. After turning off the mobile phone, slow-wave activity progressively disappeared local changes such as increased median frequency decreased and disappeared after 15-20 min. These slow waves lasting for about one second repeated every 15-20 s at the same recording electrodes. Using a telemetric electroencephalograph (ExpertTM) in awake subjects, all the noise was eliminated, and EEG showed interesting changes: after a period of 10-15 s there was no visible change, the spectrum median frequency increased in areas close to antenna after 20-40 s, a slow-wave activity (2.5-6.0 Hz) appeared in the contralateral frontal and temporal areas.

#Human brain mapping sci journal full#

Traditional EEG was full of noises during operation of a cellular phone. Spatial distribution of EMF was especially concentrated around the ipsilateral eye adjacent to the basal surface of the brain. We used a 16-channel telemetric electroencephalograph (ExpertTM), to record EEG changes during exposure of human skull to EMF emitted by a mobile phone. Cell phones emitting pulsed high-frequency electromagnetic fields (EMF) may affect the human brain, but there are inconsistent results concerning their effects on electroencephalogram (EEG).