Structure and Functional Areas of the Cerebral Cortex

Cerebral Hemispheres

Overview of the Cerebrum

The cerebrum is the largest part of the human brain and is divided into two cerebral hemispheres. Each hemisphere is responsible for a variety of complex functions and controls the opposite side of the body.

• Consists of 2 cerebral hemispheres: The left and right hemispheres make up the superior portion of the brain.

• Lateralization: Each hemisphere is specialized for certain functions.

• Cerebral Dominance: One hemisphere is typically dominant for specific functions, such as language.

• Contralateral Control: Each hemisphere controls the opposite side of the body.

Functional Specialization

Hemisphere	Main Functions
Left	Language, Intellect, Logical thinking
Right	Visual-spatial skills, Emotion, Artistic/musical skills

Example: Aphasia, a language disorder, is typically associated with damage to the left hemisphere, while singing ability may be preserved due to right hemisphere function.

Important Features of the Cerebrum

Surface Anatomy

The surface of the cerebrum is characterized by grooves and ridges, which increase its surface area and cognitive capacity.

• Gyrus (plural: gyri): Elevated ridge of tissue on the surface of the brain.

• Sulcus (plural: sulci): Shallow groove that separates gyri.

• Fissure: Deep groove that separates larger regions of the brain.

Main Sulci and Gyri

Feature	Description
Central Sulcus	Separates the frontal and parietal lobes
Precentral Gyrus	Primary motor cortex location
Postcentral Gyrus	Primary somatosensory cortex location
Longitudinal Fissure	Divides the two cerebral hemispheres

Key Point: The surface gyri and sulci are composed of gray matter, which contains neuron cell bodies.

Lobes of the Cerebrum

Major Lobes and Their Functions

The cerebrum is divided into four main lobes, each named after the cranial bone above it and associated with specific functions.

Lobe	Main Functions
Frontal	Voluntary movement, Planning, Decision-making, Consciousness, Personality
Parietal	Sensation, Temperature, Pain, Touch, Spatial perception
Temporal	Hearing, Smell, Memory
Occipital	Vision, Visual association

Example: The parietal lobe allows you to sense pain, the frontal lobe initiates movement, the occipital lobe helps you see, and the temporal lobe helps you remember events.

Functional Areas of the Cerebral Cortex

Types of Functional Areas

The cerebral cortex is the outer layer of the brain and contains three main types of functional areas:

• Motor Areas: Responsible for voluntary movement.

• Sensory Areas: Process sensory signals (e.g., touch, vision, hearing).

• Association Areas: Integrate information for complex processing, such as memory and reasoning.

Key Point: Motor and sensory areas are chiefly concerned with functions on the opposite side of the body.

Primary Motor Cortex & Primary Somatosensory Cortex

Location and Function

The primary motor cortex and primary somatosensory cortex are located in specific gyri and are responsible for movement and sensation, respectively.

• Primary Motor Cortex: Located in the precentral gyrus; initiates voluntary movement.

• Primary Somatosensory Cortex: Located in the postcentral gyrus; receives incoming signals from sensory receptors.

• Homunculus: A visual representation showing the size of body parts in relation to the number of neural connections. The size is proportional to the number of connections.

Motor vs. Sensory Homunculus

Homunculus Type	Represents	Example
Motor	Brain area for voluntary movement	Larger area for hands and face (fine motor control)
Sensory	Brain area for sensation	Larger area for lips and fingertips (high sensitivity)

Key Point: Body parts with more sensory connections have larger areas on the sensory homunculus than on the motor homunculus.

Summary Table: Key Features of the Cerebral Cortex

Feature	Description
Hemispheres	Left (language, logic), Right (spatial, emotion)
Lobes	Frontal, Parietal, Temporal, Occipital
Gyri/Sulci	Increase surface area, separate functional regions
Functional Areas	Motor, Sensory, Association
Homunculus	Proportional representation of body parts

Key Equations & Concepts

• Homunculus Proportionality: $\text{Area on homunculus} \propto \text{Number of neural connections}$

• Contralateral Control: $\text{Left hemisphere} \rightarrow \text{Right side of body}$ $\text{Right hemisphere} \rightarrow \text{Left side of body}$

Practice & Application

• Aphasia is typically associated with damage to the left hemisphere.

• Spinal reflexes are rapid, involuntary responses and may be affected by motor area injury.

• Motor and sensory homunculi illustrate the relationship between brain area and body part sensitivity/control.

Additional info: The notes include practice questions and examples to reinforce understanding of cerebral cortex structure and function.