Which brain region consists of small neural networks of gray matter with white matter tracts ascending to cortex and descending to spinal cord?

• A. Cerebellum
• B. Reticular formation
• C. Thalamus
• D. Hypothalamus

Answer: (B)

The brainstem’s reticular formation is a diffuse mesh of small gray matter clusters interwoven with white matter tracts that run through the brainstem. These pathways reach upward to the cortex and downward to the spinal cord, allowing this network to influence both cortical activity and spinal motor pathways. That arrangement—numerous tiny gray-matter networks with long tracts connecting to the cortex and to the spinal cord—best matches the description. This region underlies arousal, attention, and basic autonomic and motor functions. In contrast, the cerebellum mainly coordinates movement, the thalamus serves as a relay to the cortex, and the hypothalamus regulates autonomic and endocrine functions, none of which fit the specific diffuse brainstem network described.