On average humans have a 1:45 ratio between brain to body. This implies that there is a correlation between intelligence and brain to body ratio. However, there are exceptions to this implied correlation. In fact, intelligence is better gauged by the complexity of brain structures.
Primitive vertebrates like sharks, only have structures for basic survival functions – breathing, resting, and feeding. Lower mammals such as dogs are slightly more complex with a brain allowing for emotion and memory. Humans have structures that enable all basic functions, memory, emotion but also structures for information processing and foresight.
The brainstem is the oldest part of the brain as well as central core of it. It begins where the spinal cord swells as it entres the skull; the brainstem is vital for basic automatic survival functions.
- The medulla is the base of the brainstem: controlling heart rate and breathing.
- The brainstem-crosser over point is where the nerves from the opposite sides of the body meet.
- The reticular formation is the nerve network in the brainstem that extends up to the thalamus. It plays an important role in controlling arousal (control of consciousness), specifically our sleep cycle. Other vital roles of the reticular formation includes motor contro, visceral control (instinctual), and sensory control.
- The pons or “bridge” connects the medulla with the cerebral cortex. In addition, the pons helps connect the right and left hemisphere as well controlling autonomic functions such as arousal.
- The thalamus is the brain’s “sensory switchboard,” located on top of the brainstem. It directs messages to the sensory receptive areas in the cerebral cortex and transmits responses from the sensory areas to the cerebellum and medulla.
The cerebellum or the “little brain” is attached to the rear of the brainstem and helps coordinate voluntary movement and balance. The cerebellum of kind of nonverbal memory and learning. It also manages sustaining functions with the spinal cord.
The limbic system is at the border of the brainstem and the cerebral hemisphere and is associated with emotions and drives.
- The amygdala consists of two almond shaped clusters that influence aggression and fear.
- The hypothalamus sits below the thalamus and directs maintenance activities such as appetite, thirst and body temperature. Furthermore, it helps govern the endocrine system via the pituitary gland.
Neuroscientists and neuropsychologists can stimulate the pleasure centres in our brain to calm patients. It is also understood that addictive drugs trigger our pleasure system.