Cerebrum

The cerebrum is called the forebrain and is where higher order thinking and processing occurs. This is what makes us who we are and deals with higher order abstractions from sensory information, and planning conscious motor movements. It is the host of our consciousness and personality, as well as emotions and memory. It is divided into regions which have chief functions, which all work in a synergistic way to give rise to what we are as conscious beings.

The main areas of the system

• Frontal lobe
• Temporal lobe
• Parietal lobe
• Occipital lobe
• Insular lobe
• Limbic system
• Basal ganglia

Each of these are split into smaller components which have more specialised functions as you go deeper. There will be a section on each.

General organisation of the cerebrum

The cerebrum is the most caudal end of the CNS, with the inputs for processing feeding up through the brainstem (with some exceptions), where it passes through the thalamus and internal capsule to the corona radiata and to the the cerebrum. The outputs go much the same, just in reverse. There are many other pathways but we will learn that later.

The cerebrum is symmetrical and divided in 2 halves, each termed a hemisphere and each hemisphere is connected by the corpus callosum.

Frontal lobe

Anatomy

This is defined and the cortical area anterior to the central sulcus, and superior to the Sylvian fissure, or lateral gyrus.

Function

Temporal lobe

Anatomy

This is the lobe which is anteroinferior in the brain. It is separated from the frontal lobe by the lateral sulcus. the separation between this and the parietal/occipital lobes is more ill defined.

Function

Parietal lobe

Anatomy

this is the lateral superior lobe and is separated from the frontal lobe by the central sulcus, and from the occipital lobe by the parieto-occipital sulcus.

Function

Occipital lobe

Anatomy

This is the most posterior of the cortical lobes.

Function

Insular lobe

Anatomy

Function

Limbic system

Anatomy

Function

Basal ganglia

Anatomy

Function

What does this do

The basal ganglia exists to prohibit or allow programs to go ahead. This can be motor commands, action selection habits etc.

It does this through 2 pathways, the direct and indirect pathways.

The direct pathway is the Cerebral cortex excites the striatum, which inhibits the internal globus pallidus leading to decreased inhibition of the thalamus, which gets excited and says go for it to the cerebral cortex.

the indirect pathway is excitation of the substantia nigra inhibits the the external globus pallidus which disinhibits the subthalamic nucleus which leads to more stimulus of the internal globus pallidus which inhibits the thalamus and leads to a nogo signal.

The role of dopamine is to excite the go pathways and inhibit the nogo pathway. When it is lacking, there is overinhibition and reduced movement.

Forebrain features and functions of each lobe

The cerebrum has many different areas, with each having a specific area which it does well

• Brocas area, made of opercular and triangular gyri Deals with spoken speech
• Prefrontal cortex This deals with intellect complex learning, cognition, recall anbd personality. it is heavily dependant on social environment. damage can result in mental and personality disorders
• Supramarginal gyrus This deals with tactile sensory data and in involved with spacial perception and limb spacial awareness
• Primary visual cortex This is the gyri forming the walls of the the calcarine sulcus.
• Visual association area
• uncus
• Amygdala
• Wernickes area deals with listening to communications
• primary auditory cortex
• right hippo campus - spatial representation.
• Insular lobe Function is unknown. visceral sensation effected as well as general sensory and mtoro function. A case study apparently found the left insular lobe was involved in the normal emotional processing of music.
• pineal gland
• thalamus
• hypothalamus