The amount of information transmitted about contrast by neurones in the cat's visual cortex

The responses of neurones in the cat's visual cortex are very variable in amplitude. Thus, although the average response amplitude of a single neurone depends closely upon the contrast of a sinusoidal grating, the instantaneous amplitude of the response can convey little information about the grating's contrast. This paper shows that a typical cortical neurone can convey less than one bit of information about contrast in 0.5 s. The amount of information that a neurone can convey is closely correlated with the neurone's responsivity.

Higher order structure in a short repeat length chromatin.

Polynucleosomes from calf brain cortical neurone nuclei have an average repeat length of less than 168 base pairs. The ability of this material to adopt higher order structure has been assessed by various physical techniques. Although containing on average less DNA per nucleosome than is required to form a chromatosome, this short repeat length chromatin folded in an H1 dependent manner to a structure with properties similar to those observed for longer repeat length chromatins such as that of chicken erythrocyte (McGhee, J.D., D.C. Rau, E. Charney, and G. Felsenfeld, 1980, Cell, 22:87-96). These observations are discussed in the context of H1 location in the higher order chromatin fiber.

Interactions between p-tyramine, m-tyramine, or β-phenylethylamine and dopamine on single neurones in the cortex and caudate nucleus of the rat

p-Tyramine, applied to cortical and caudate neurones with weak iontophoretic currents (0–10 nA), did not usually cause any alteration of base-line firing rate. However, neuronal responses to dopamine (DA) during such weak applications of p-tyramine were greatly enhanced. Cortical neurone responses to noradrenaline (NA) were similarly potentiated, but both cortical and caudate neurone responses to α-aminobutyric acid were unaffected by p-tyramine. In addition, weak background applications of DA which did not affect cell firing rate were also without effect on the neuronal responses to the standard application of DA. The responses of cortical neurones to DA were also potentiated by m-tyramine and β-phenylethylamine applied with weak cationic currents. The results may suggest that trace amines can enhance NA and DA transmission in the central nervous system.