
Given the following passage

"The SCN projects to a set of areas in the hypothalamus, brainstem, and midbrain that are involved in implementing sleep-wake cycles. An important component of the system is the reticular formation, a group of neuron-clusters scattered diffusely through the core of the lower brain. Reticular neurons send signals to the thalamus, which in turn sends activity-level-controlling signals to every part of the cortex. Damage to the reticular formation can produce a permanent state of coma.",

answer the following question. Note that the answer is present within the text.

Question: What part of the brain has the important group of neuron-clusters involved in implementing sleep-wake cycles? 

the core of the lower brain
