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The cerebral cortex is the outermost layer of thebrain, composed of folded gray matter. It plays a crucial role in various complex cognitive processes including thought, perception, language, memory, attention, consciousness, and advanced motor functions.
The cerebral cortex is constructed primarily ofgrey matter, containing between 14 and 16 billionneurons.
Its wrinkled appearance, consisting ofbulges (gyri) and deep furrows (sulci), allows for a wider surface area and increased number of neurons, enabling large amounts of information to be processed.
The cerebral cortex controls a vast array of functions through the use of the lobes, which are divided based on the location ofgyri and sulci. These lobes are called thefrontal lobes,temporal lobes,parietal lobes, andoccipital lobes.
Lobes and their Functions
The cerebral cortex, which is the outer surface of the brain, is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory.
Each cerebral hemisphere can be subdivided into four lobes, each associated with different functions.
Together, the lobes serve many conscious and unconscious functions, such as being responsible for movement,processing sensory informationfrom the senses, processing language,intelligence, and personality.
Frontal Lobes
Located at the front of the brain, the frontal lobes are often described as our “control panel.” They play a crucial role in executive functions and higher-order cognitive processes.
The prefrontal cortex, a large part of the frontal lobes, is particularly important for these functions and is also key in shaping our personality and social behavior.
Key functions of the frontal lobes include:
Damage to the frontal lobes can result in a wide range of symptoms, from changes in personality and impaired social judgment to difficulties with motor control and speech production.
For instance, individuals with frontal lobe damage might struggle with impulse control or have difficulty organizing tasks.
Parietal Lobes
Situated at the top and back of the head, the parietal lobes are instrumental in processing sensory information and spatial awareness.
The primary somatosensory cortex, located in the parietal lobes, receives and interprets touch sensations from all over the body.
Key functions of the parietal lobes include:
Interestingly, the left and right parietal lobes often have slightly different functions.
Damage to the right parietal lobe can result in neglect syndrome, where a person may ignore or be unaware of the left side of their body or environment, such as only eating food from the right side of a plate.
Temporal Lobes
The temporal lobes, found on the sides of the brain near the ears, are involved in a diverse array of functions.
They play a crucial role in auditory processing, language comprehension, memory, and emotional processing.
Key functions of the temporal lobes include:
The temporal lobes house structures critical for memory formation and storage, such as thehippocampus, and emotional processing through theamygdala.
Damage to the temporal lobes can result in difficulties with language comprehension, memory formation, or emotional regulation.
For instance, bilateral temporal lobe damage can lead to profound amnesia, where a person struggles to form new memories.
Occipital Lobes
Located at the back of the brain, the occipital lobes are primarily dedicated to visual processing.
The primary visual cortex (also known as V1) receives raw visual information from the eyes and begins the process of interpreting it.
Key functions of the occipital lobes include:
While the occipital lobes might seem straightforward in their function, they’re actually involved in complex processes like visual memory and visual associations.
Damage to the occipital lobes can result in various forms of visual impairment. For example, damage to specific areas can lead to color blindness, difficulties with motion perception, or even rare conditions like visual agnosia, where a person can see objects but can’t recognize what they are.
Functional Areas
The cerebral cortex can be divided into three main types of functional areas: sensory, motor, and association areas.
These divisions serve different purposes but work together to process information, control behavior, and enable complex cognitive functions.
While these areas are distributed across the different lobes, their specific functions contribute to the overall capabilities of the cerebral cortex.
Sensory Areas
Sensory areas receive and process information from various senses.
Key regions:
Motor Areas
Motor areas regulate and initiate voluntary movement, primarily found within in the frontal lobes.
Primary components:
Association Areas
Association areas are regions of the cerebral cortex not directly involved in primary sensory processing or motor control.
These are found within all four lobes, make up a large portion of the cerebral cortex and are interspersed among primary, sensory, and motor areas.
Key roles:
StructureThe cerebral cortex has a layered structure, with 6 layers numbered from the outer surface (Layer 1) to the innermost layer (Layer 6).Layer 1is the molecular layer, containing few neuronal cell bodies but many dendrites and axons.Layer 2is the external granular layer, containing small pyramidal neurons and numerous small granule cells.Layer 3is the external pyramidal layer, with predominantly small and medium pyramidal neurons.Layer 4is the internal granular layer, with mainly stellate and pyramidal neurons.Layer 5is the internal pyramidal layer, containing large pyramidal neurons that give rise to major output pathways.Layer 6is the multiform layer, with few large pyramidal neurons among many smaller types.The cerebral cortex can be divided into 3 main regions:Neocortex:The evolutionarily newest part, with 6 layers. Makes up about 90% of the human cerebral cortex. Responsible for higher cognitive functions like sensory perception, generation of motor commands, spatial reasoning, language, and conscious thought.Allocortex:The older part with fewer than 6 layers. Includes the olfactory cortex and hippocampus. Plays a role in olfaction and memory.Archicortex:The oldest part with only 3 cortical layers. Forms the hippocampus. Involved in memory and spatial navigation.The cortex also contains many different types of neurons and neuroglial cells that support cortical function:Pyramidal cells:The primary projection neurons shaped like pyramids. Located in layers 3, 5, and 6. Transmit signals from one region of the cortex to another.Stellate cells:Found in layer 4. Receive and integrate inputs from the thalamus.Basket cells:Inhibitory interneurons found in layers 2-6. Help regulate cortical excitability.Astrocytes:Star-shaped glial cells that provide structural and metabolic support to neurons. Help regulate neurotransmitter levels.Oligodendrocytes:Produce myelin to insulate neuron axons, speeding up signal transmission.Microglia:Act as the immune cells of the brain, responding to pathogens and brain injuries.
Structure
The cerebral cortex has a layered structure, with 6 layers numbered from the outer surface (Layer 1) to the innermost layer (Layer 6).
The cerebral cortex can be divided into 3 main regions:
The cortex also contains many different types of neurons and neuroglial cells that support cortical function:
Brodmann Areas
Brodmann Areas,named after German neurologist Korbinian Brodmann, are a system for mapping and categorizing regions of the human cerebral cortex based on their distinct cellular architecture and functions.
These numbered areas, which range from 1 to 52, provide a structural framework for understanding different brain functions, such as sensory processing, motor control, and higher cognitive processes, contributing to our knowledge of brain organization and function.
References
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Further Information
Saul McLeod, PhD
BSc (Hons) Psychology, MRes, PhD, University of Manchester
Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.
Olivia Guy-Evans, MSc
BSc (Hons) Psychology, MSc Psychology of Education
Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.
