How the Brain Works Impressions
How the Brain Works
The Brain’s Filtering System
The brain is constantly subjected to impressions and impulses from sight, hearing, taste, smell, and touch. If all this information were processed, the brain’s energy would not suffice. To manage the inflow of information, there are various built-in filters that determine what information reaches the cerebral cortex and consciousness and what is stopped along the way.
A collection of nerve cells in the brainstem, when activated, keeps the cortex alert and “awake” for impressions. Another filtering function is found in the thalamus, which consists of nerve cells deep inside each cerebral hemisphere where sensory information passes to advance to the cerebral cortex. The basal ganglia, a control system for movements and mental functions, also have filter functions. Dopamine is an important signal substance in these filter functions.
When the nervous system is damaged, the filter systems become less efficient, allowing more information to reach higher brain areas, causing increased sensitivity to sound and light.