A series of simultaneous recordings from several striate cortex neurons were made in paralyzed, anesthetized cats. Recordings were obtained with one or two bundles of extra fine wires and originated from one and two cortical orientation columns. Standard PST histograms and, in some cases, response planes were used to analyse the neuronal receptive fields. Functional connectivity between neurons was assessed by cross-correlation of their spike trains. It was found that 61% of neuronal pairs found within a column shared the same input, either excitatory or inhibitory, Even if neurons in a pair belonged to two different columns separated by 1mm lateral distance, 40% of pairs still exhibited shared input coordination. This type of coordination could also encompass all combinations of simple and complex fields in the pair. Direct connections between neurons were found almost exclusively within columns: excitatory connections were found in 20% of cases and inhibitory in 8%. Direct connections were often accompanied by the other types of interactions. Only one example of excitatory and one of inhibitory direct connections were found between columns. In both cases preferred orientations were almost identical.

The recently developed qualitative method of diagnosis of dynamical systems-recurrence plots-has been applied to the analysis of dynamics of neuronal spike trains recorded from cerebellum and red nucleus of anesthetized cats. Recurrence plots revealed robust and common changes in the similarity structure of interspike interval sequences as well as significant deviations from randomness in serial ordering of intervals. Recurring episodes of alike, quasi-deterministic firing patterns suggest the spontaneous modulation of the dynamical complexity of the trajectories of observed neurons. These modulations are associated with changing dynamical properties of a neuronal spike-train-generating system. Their existence is compatible with the information processing paradigm of attractor neural networks.

Two series of experiments concerning the effects induced by unilateral cerebellar lesions on background activity and responses of red nucleus neurons contralateral to lesion sites are reported in this short review. The first series describes the effects of cerebellar cortex ablations, the second reports the results of hemicerebellectomy. The major source of input to the deep cerebellar nuclei, the Purkinje cells of the cerebellar cortex are known to be inhibitory. Removal of this influence by cerebellar cortex lesion results in an increase of the interpositus neurons background activity. This effect strengthens the interpositus excitatory influence upon rubral neurons by evoking exaggerated depolarization and enhancing sensitivity of these cells to somatosensory volleys. This causes a considerable increase in the background firing, eliminates the pauses in discharges occurring in responses generated by somatosensory stimuli, and augments the excitatory rebound. These changes destroy the content and timing of feedback information flowing through the spino-cerebello-rubro-spinal loop, and are, at least in part, responsible for motor deficits of cerebellar dysfunction. Hemicerebellectomy reduces drastically spontaneous firing of rubro-spinal neurons and simplifies response patterns. Due to direct spino-rubral pathways the latency of response is not changed.

Changes in the excitability of the liverwort Conocephalum conicum L. caused by inhibitors of ionic channels and phosphorylation uncouplers, were examined. Action potentials were triggered by electrical and light stimuli. Tetraethylammonium chloride, an inhibitor of K+ channels, completely blocked the ability to generate action potentials. Excitability also disappeared under the influence of MnCl2 and LaCl3, inhibitors of Ca2+ channels. The participation of Ca2+ and K+ in the electrogenesis of action potentials in C. conicum is discussed. Treatment with phosphorylation uncouplers induced a gradual disappearance of the metabolic component of the resting potential. It was accompanied by some series of excitations, numbering from several to over a dozen impulses characterized by decreasing amplitudes, after which the organism became totally unexcitable. Dicyclohexylcarbodiimide an inhibitor of H+‐ATPase, also caused depolarization of the transmembrane potential and disappearance of excitability. The results indicated the participation of a metabolic component in the generation of action potentials in C. conicum.