Some data on postnatal maturation of the cerebral cortex in cat

This paper describes the neurons in different cortical areas and traces their postnatal changes. Rapid Golgi and Golgi--Kopsch impregnation were carried out in 1-day-old and 9-day-old kittens. The maturation of the pyramidal neurons can be observed mainly on their basal dendritic orientation and on development of the dendritic spines. The differentiation of the interneurons (non-pyramidal) also proceeds on the first postnatal days. These, though slightly less mature than the associated pyramidal neurons, are identifiable already on the first postnatal day. It is concluded that there are significant differences in the maturation of the neurons in the various cortical areas.     

Oxidative metabolism of the cerebral cortex in young animals

Intensity of glucose, leucine and palmitate oxidation in the cortex of pigs increases during the first days after their birth. Fasting of pigs during 24 hours after birth intensifies glucose catabolism in the cortex through the pentose phosphate way. Intensity of palmitate and leucine oxidation in the cortex of fasting pigs is at the low level. Ketonic bodies participate in the power supply of cortex functions of satisfied one-day pigs but their contribution to the nerve tissue power of fasting one-and five-day pigs is insignificant.     

Some data on the occurrence of Salmonella in animals in Surinam

Summary During an investigation in Surinam 18Salmonella types were isolated from material obtained from cattle, pigs, dogs, rats, awaris, fowl and toads.     

Some Golgi data on visual cortex of the rhesus monkey.

The rhesus monkey's visual cortex was studied on Golgi material. The terminal arborization of the geniculate fibres and non-specific vertical fibres have been analysed. The interneurons (intrinsic neurons) of the area described in detail and classified on the basis of their axonal and dendrite arborizations. The stellate neurons in layer IV are discussed.     

Some chemical and electrophysiological effects of glutamate in cerebral cortex

The efflux of ⁴⁵Ca²⁺ and ³H-GABA from cat cerebral cortex has been measured in vivo by a superfusion technique. Under control conditions, the efflux of both these isotopes is sensitive to increments in the calcium concentration of the superfusion medium but insensitive to the addition of 25 mM GABA. After 40 min of contact with medium containing 25 mM glutamate, however, neither ⁴⁵Ca²⁺ nor ³H-GABA efflux is affected by added Ca²⁺ but ³H-GABA efflux becomes considerably enhanced by 25 mM GABA. The mean membrane potentials at this time were found to be less than controls. Depolarization generally continued past this time, recovery beginning 150 min after superfusion with glutamate. Peaks in ⁴⁵Ca²⁺ efflux were also correlated with seizure activity which was sometimes elicited by topical glutamate. It is suggested that the transport systems for Ca²⁺ and GABA may be sensitive to states of neural activity, such as spreading depression.     

Phase relationships of cerebral cortex potentials in the rabbit during the execution of motor responses

EEG waves phase relations in the sensorimotor and visual cortical areas were studied in 12 rabbits before and during a motor reaction in response to light stimulation. Phase relations in the background activity were characterized by a considerable dispersion (from 26 to 45 degrees). Light stimulation increased the quantity of synphasic EEG oscillations in adjacent cortical points and stabilized the phase shift between EEG waves in the sensorimotor and visual cortical areas. Motor reactions of rabbits to light occurred when theta-rhythm with the most constant phase shift was observed in the EEG of these areas.     

Thoughts on the cerebral cortex

The cortex is often described as a network processing information in the direction from sensory to motor areas. However, the structure of the cortex is asymmetrical only in the vertical direction, suggesting an input-output transformation between layers rather than between areas. This operation must be a very generally applicable one, since the plan of the cortex is basically the same everywhere. In an attempt to understand it, a skeleton cortex of only pyramidal cells is considered. They are characterized by a double dendritic expansion, an apical one in the first layer, which is considered as the input layer, and a basal one which receives excitation from the axon collaterals of other pyramidal cells. If pyramidal cells learn (perhaps by growing dendritic spines) to respond to frequent constellations of activity in their afferents, each will learn a property of the input (through its apical dendrites) provided that it was preceded by other properties sensed by neighbouring pyramidal cells (which influences it through its basal dendrites). Thus the pyramidal cells will code the input in terms of properties which have a tendency to follow each other. This will be a coding which reflects the causal structure of the world. Various uses of a network embodying the conditional probabilities of events in the input are described, including recognition of familiar sequences and prediction. The local variation of fiber patterns in the cerebral cortex of man, described as myeloarchitectonics, is interpreted as a macroscopical expression of the different statistics of the set of conditional probabilities linking the events represented by individual pyramidal cells in different areas (in different functional contexts).