Answer is A (Anterior Horn cells): Motor neuron disease is associated with degeneration of anterior horn cells in the spinal cord. Peripheral nerves, spinothalatnic tract and spinocerebellar tract are not involved in motor neuron diseases. Motor Neuron Disease encompasses disorders that predominantly or exclusively affect the upper motor neurons (Neurons that lie in the cerebral coex and project through the coicospinal / coicobulbar tract) or lower motor neurons (Neurons that lie in the anterior horn cell of the spinal cord or motor cranial nuclei that lie in the brainstem) or both.