ABSTRACT
Motor function in humans is subserved by several distinct anatomical regions which are interconnected. The primary motor cortex is different from other regions of the cerebral cortex in that it is thicker but has a low cell density. The pyramidal neurons have extensive spiny dendritic trees which collect an enormous number of different synaptic, excitatory and inhibitory inputs. It needs to be kept in mind that the responses in a target muscle depend on the global excitability of the motor pathway including large pyramidal cells, cortical excitatory and inhibitory inter-neurons and spinal motor neurons, most of which are affected to some degree in Amyotrophic Lateral Sclerosis (ALS). Animal experiments using intracellular recordings can directly record the postsynaptic potentials in anterior horn cells while changes in firing frequency are simultaneously monitored. The most consistent abnormality of the primary peak is desynchronization and increased duration.
