How do higher parts of the brain influence lower parts?

Answer 1

The above answer is a little more philosophical, not necesarily hard science.

The frontal cortex, the "top" of the brain, is the house of executive function. This means that it organizes and coordinates the specific functions of the various regions of the lower brain. It also, like the above author noted, inhibits impules, and allows us to control what we say and do.

In short, it allows us to be coherent, organized, discriminating organisms.

Answer 2

Neurologically the brain is a cognized engine the immeasurable entirety of which is yet to be fathomed by any.

Psychologically the higher brain aspires to a greater humanity, the lower towards those basal instincts that lie latent in the lower nature of man.

Success in life is not entirely how much or how successful we are deemed or feel to be, but the path we trod, and the ways the aforesaid was achieved. Some take the lower route as a short cut, the nobler, refuse to compromise themselves in any way but the righteous.