Centrifugal effects in the avian retina

Electrical stimulation of the centrifugal fibers to the avian retina can disturb the balance between the excitatory and inhibitory system within the receptive fields of individual retinal ganglion cells. Although the mechanisms may vary from one unit to another, the effect is always to make them fire more readily and to a wider range of visual inputs.

Pyramidal and Non-Pyramidal Pathways in Monkeys: Anatomical and Functional Correlation

In monkeys, corticospinal fibers terminate on motoneurons and interneurons. Brainstem fibers, which may be grouped into medial and lateral pathways, terminate on the same interneurons. Observations following bilateral pyramidotomy indicate that motility can be adequately directed by the brainstem systems while cortical connections add speed and the capacity for further fractionating movements. Further experiments suggest that the medial and lateral brainstem pathways primarily direct proximal and distal movements, respectively.

PACEMAKER NEURONS: EFFECTS OF REGULARLY SPACED SYNAPTIC INPUT

The consequences of inhibitory or excitatory synaptic input between pacemaker neurons were predicted mathematically and through digital-computer simulations, and the predicted behavior was found to occur in abdominal ganglia of Aplysia and in stretch receptors of Procambarus. Discharge patterns under conditions that do not involve interneuronal feedback are characteristic and self-stabilizing. Paradoxically, increased arrival rates of inhibitory input can increase firing rates, and increased excitatory input rates can decrease firing rates.

Descending Projections to Spinal Motor and Sesory Cell Groups in the Monkey: Cortex versus Subcortex

In rhesus monkeys, corticospinal fibers have been found to terminate in motor, sensory, and internuncial cell groups. The present study reveals that the subcorticospinal fibers terminate primarily on internuncial neurons. Possible mechanisms involved in transmission of cortical and subcortical influences on motor and sensory cell groups are discussed.