The human brain is a communication machine, and research into the localisation of function in the brain reveals that certain brain regions are responsible for and specialise in performing particular functions over others. These brain areas oversee processes such as language production and comprehension, memory, and other behaviours and abilities. Using various investigative techniques, we can identify the structure and position of these regions in the brain. So, what exactly is the localisation of brain function?
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Jetzt kostenlos anmeldenThe human brain is a communication machine, and research into the localisation of function in the brain reveals that certain brain regions are responsible for and specialise in performing particular functions over others. These brain areas oversee processes such as language production and comprehension, memory, and other behaviours and abilities. Using various investigative techniques, we can identify the structure and position of these regions in the brain. So, what exactly is the localisation of brain function?
Fig. 1 - Localisation of function in the brain highlights the different regions of function in the brain.
Localisation of brain function is the idea that specific areas of the brain are responsible for a particular function; they have explicit locations within the brain. Examples include areas dedicated to memory and language, i.e., Broca's area. Evidence of localisation is seen through neuroimaging techniques and loss of function due to damage.
When a particular brain area is damaged, the associated area of function is likely to suffer, supporting the idea of localisation of function. To understand how the brain operates, however, we must first understand the structure of the brain and how it operates. The brain has two hemispheres, the left and right, operating contralaterally.
Contralaterally refers to the side of the body opposite to which a function is responsible. So, the right hemisphere is responsible for the left side of the body and vice versa.
The corpus callosum connects the two hemispheres, allowing them to communicate. Each hemisphere specialises in performing certain functions, which is called hemispheric lateralisation. By communicating, they can share, integrate, and process information excellently.
The brain is a highly complex organ that excels at processing information.
Particular areas are well-known for their relation to specific functions in the brain. Evidence for the localisation of function can be seen in multiple parts of the brain, including the prefrontal cortex, the motor and somatosensory cortex, the visual cortex, the auditor cortex, and Broca's and Wernicke's areas.
Fig. 2 - The different brain areas are associated with different functions.
The prefrontal cortex, the motor and somatosensory cortex, the visual cortex, the auditor cortex, and Broca's and Wernicke's areas all show properties of localisation of function. We can find evidence for the localisation of function by identifying the functional areas associated with the aforementioned brain structures.
The prefrontal cortex is responsible for various complex cognitive processes and higher-level functions. It is involved in:
Damage to the prefrontal cortex causes various issues, affecting behaviour and the ability to plan, and often results in personality changes.
The motor cortex is located at the back of the frontal lobe, anterior to the central sulcus, one of the more notable folds in the brain. The motor cortex is primarily responsible for voluntary muscle control.
The functions are carried out contralaterally.
If you were to move your left hand, neurones in the right motor cortex would activate.
More specifically, the motor cortex is responsible for:
Damage to these areas can result in the loss of the above functions. Paralysis may occur, as voluntary control over muscles may be lost. It is difficult to sequence movements or actions.
The somatosensory cortex is situated in the postcentral gyrus in the parietal lobe, and sits posterior to the central sulcus. The somatosensory cortex operates contralaterally.
The right sensory cortex activates if you feel something tickle your left hand.
We can see where the somatosensory cortex is located in the diagram. Note how the diagram illustrates the approximate location of sensations within the body.
Fig. 3 - The primary somatosensory cortex is involved in interpreting sensations.
The somatosensory cortex is responsible for:
Receiving and processing sensations, such as touch and temperature.
Damage to the somatosensory cortex causes a loss of sensation from the opposite side of the body. It can result in one area being completely ignored, or there may be a loss of ability to recognise an object by its feel, known as agnosia.
The visual cortex is located in the occipital lobe at the back of the brain. Light enters the eye, and retinal photoreceptors convert light into nerve impulses. The optic nerve transmits these impulses through the optic canal to the thalamus (the lateral geniculate nucleus), which then sends the information to the visual cortex.
The right hemisphere processes visual information of the left eye, and vice versa for the left hemisphere. It operates contralaterally.
It is responsible for:
We can see where the visual cortex is located in the localisation of function in the brain diagram. As discussed above, the primary visual cortex is in the occipital lobe.
Fig. 4 - The primary visual cortex is located in the occipital lobe, seen in the posterior view.
Damage to the visual cortex can result in partial or complete blindness, and this blindness can manifest in different forms.
The auditory cortex is located at the top of the temporal lobe, specifically the superior temporal gyrus. The primary auditory cortex receives auditory information from the thalamus, which receives sound impulses (sensations) from the cochlea.
The auditory cortex is responsible for:
Damage to this area can cause issues such as the inability to detect changes in a person's pitch or tone of voice, making conversing with someone and interpreting their intentions extremely difficult.
Broca's area is located in the left frontal lobe in the left hemisphere. It is responsible for:
Broca discovered the area when a patient could only produce the word 'tan'. The patient struggled with speech production. The only words Broca heard him say were 'God damn' in French due to his frustration over not speaking.
After the patient died, Broca performed an autopsy and found a large crater in the left frontal lobe.
Broca ascribed this lesion to the loss of speech production in the patient. He discovered eight more cases with similar evidence and speech production issues to confirm this. The original patient became the first to be described as suffering from Broca's aphasia (a loss of ability to produce speech due to brain damage).
We can see precisely where Broca's area is in the diagram. As we discussed above, it is located in the left hemisphere, specifically in the frontal lobe.
Fig. 5 - Broca's area is involved in speech production.
Wernicke's area is primarily said to be located in the upper temporal lobe. It resides in the left hemisphere. Wernicke's area is associated with speech comprehension.
The left hemisphere is becoming increasingly prominent in its dominance of language production functions.
Wernicke suggested damage in a specific part of the left hemisphere would result in fluent but meaningless speech.
Patients could speak with fluent sounds and inflexions (changes in pitch to give meaning), but when listened to, the sound made little sense. This disorder is known as Wernicke's Aphasia. People often also struggle to understand language with this disorder.
Wernicke proposed a model including his and Broca's area to state that Wernicke's area is responsible for meaningful speech, and Broca's area is responsible for making plans and generating speech (through moving the mouth and tongue).
Damaging Broca's and Wernicke's areas can result in global aphasia, where patients struggle to produce and understand speech.
We can see in the diagram where Wernicke's area is located. As we discussed above, it is found in the temporal lobe.
Fig. 6 - Wernicke's area is involved in speech comprehension.
There are strengths and weaknesses to the argument for the localisation of function within the brain.
Supporting arguments for the localisation of function include:
Opposing arguments that criticise the localisation of function in the brain include:
Localisation of function in the brain refers to the idea that specific areas of the brain are responsible for a particular function. Hemispheric lateralisation is where each brain hemisphere is specialised to perform certain functions, similar to the localisation of function. The brain operates contralaterally.
Evidence for localisation can be seen in the different areas of the brain. The motor cortex is responsible for motor control, and the somatosensory cortex is responsible for sensation processing.
The visual cortex is responsible for visual processing functions and perceiving information. Damage to the visual cortex can result in partial or complete blindness. The auditory cortex is responsible for sensing sound. Damage to this area can cause issues with understanding and processing sound.
Broca's and Wernicke's areas are in the left hemisphere specifically. Broca's area is responsible for speech production, and Wernicke's area is responsible for speech comprehension. The left hemisphere is dominant in language skills.
Both modern and old research supports localisation – fMRI shows activated areas, and damage to these areas disrupts associated functions. TMS can actively disrupt localised functions, and double dissociations support localised functions. Plasticity of the brain, however, opposes the idea of localisation, and inconsistencies have been found in research attempting to identify localised areas (Broca's).
Localisation of function in the brain is important because it helps researchers identify brain areas that could be responsible for specific functions. It aids massively in researching the complexity of the organ.
Functional localisation is the concept that some brain regions are responsible for particular functions.
Localisation is where a specific brain area is associated directly with a particular function. Lateralisation is where the brain has two hemispheres connected by the corpus callosum that are not entirely alike. Each hemisphere of the brain is specialised to perform certain functions or processes.
Many areas of the brain are associated with memory control. This includes the prefrontal cortex, the amygdala, the hippocampus, and the cerebellum.
The frontal lobe is responsible for a range of functions, including voluntary movement and higher-level executive functions, as seen in the prefrontal cortex.
What is the localisation of function in the brain?
Localisation is the concept that some brain regions are responsible for particular functions. They carry out and oversee the functions of behaviours and processes due to their structure and position.
How does localisation of function in the brain contrast with the holistic view of the brain?
The holistic view of the brain states that functions occur across the entirety of the brain. Localisation suggests that specific functions occur in certain parts of the brain, not the whole of the brain.
What is hemispheric lateralisation?
Hemispheric lateralisation is where each brain hemisphere is specialised to perform certain functions.
What does contralateral mean?
Contralaterally refers to the side of the body opposite to which a function is responsible. So, the right hemisphere is responsible for the left side of the body and vice versa.
What fold in the brain do the motor and somatosensory cortex run along?
The fold in the brain that the motor and somatosensory cortex run along is called the central sulcus.
What are the functions of the motor cortex?
The functions of the motor cortex are planning and executing voluntary movement, such as choosing to move a limb as well as spatial awareness and coordinating the two sides of the body.
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