Changes in the cerebellar cortex in rats after portocaval anastomosis

After portocaval anastomosis, rats develop focal vacuolation, with apparent homogenization and loss of Purkinje cells and accompanying gliosis, in the depths of the cerebellar folia. The vacuolation represents focal swelling of astrocyte processes. This appears from the 5th week and continues to occur up to 38 weeks after operation. The severity of the cerebellar changes appear to be directly related to the plasma NH₄-N level. It is argued that these changes are closely similar to those found in human patients with acquired hepatic encephalopathy, and that they are part of a general metabolic stress induced by the persistently high plasma ammonia level on the astrocyte cellular compartment.     

Effects of60Co radiation on the cellular responses in degenerating dorsal columns in the rat spinal cord

Summary Rats were irradiated with doses of 1 000–3 000 rads to the cervical spinal cord and subsequently given a paralytic dose of p-Bromophenylacetylurea. The nuclear populations in the degenerating dorsal columns were determined and it was found that a significant suppression of cell proliferation occurred after all three dose levels. The cell populations in the shielded parts of the tracts rostral to the irradiated zone were not affected.     

The other handicap: brightness.

Because of changing attitudes to the measurement of mental abilities, only the slow child is assessed and receives special educational help. By contrast, the bright child may remain undetected because unassessed. For these children there are few special provisions, and they may present as behaviourally disturbed or educationally retarded. We describe four such children, and we feel that more facilities should be devoted to helping bright children, both at home and in school.     

The motion-induced position shift depends on the perceived direction of bistable quartet motion

Motion can influence the perceived position of nearby stationary objects (Nature Neuroscience 3 (2000) 954). To investigate the influence of high-level motion processes on the position shift while controlling for low-level motion signals, we measured the position shift as a function of the motion seen in a bistable quartet. In this stimulus, motion can be seen along either one or the other of two possible paths. An illusory position shift was observed only when the flashes were adjacent to the path where motion was perceived. If the flash was adjacent to the other path, where no motion was perceived, there was no illusory displacement. Thus for the same physical stimulus, a change in the perceived motion path determined the location where illusory position shifts would be seen. This result indicates that high-level motion processes alone are sufficient to produce the position shift of stationary objects. The effect of the timing of the test flash between the onset and offset of the motion was also examined. The position shifts were greatest at the onset of motion, then decreasing gradually, disappearing at the offset of motion. We propose an attentional repulsion explanation for the shift effect.