Article title: Functional Areas of the Cerebral Cortex
Author: Yazan Ibrahim
Editor: Odette El Ghawi, Shaden Tashtoush, Ihdaa bani Khalaf.
Reviewer: Ethar Hazaimeh.
Keywords: Functional Areas, Cerebral Cortex, Brodmann’s Areas, Neuroanatomy
Overview
The cerebral cortex is the outer part of the brain. It’s made of gray matter formed by neuronal cell bodies. The surface of the cerebral cortex has bumps referred to as gyri and grooves referred to as sulci. Sulci anatomically divides the cortex into lobes [1]. Brodmann’s book divided The brain into 47 functional areas [2].
Functional areas of the cerebral cortex
Temporal lobe
Located in the middle cranial fossa, the temporal lobe is anterior to the occipital lobe, posterior to the frontal lobe, and inferior to the Sylvian fissure. The amygdala and hippocampus are both located within the temporal lobe. Moreover, eight cognitive domains have been identified via functional imaging [9]: the posterior superior temporal gyrus, medial structures, dorsal structures, ventral temporal lobe, and temporo-occipital junction.
The posterior part of the left superior temporal gyrus, the angular gyrus (Brodmann’s area 39), and the supramarginal gyrus (Brodmann’s area 40) represent Wernicke’s sensory speech areas [10]. Wernicke’s areas receive impulses from the auditory and visual areas and interpret them. Lesions in these structures may lead to alexia, agraphia, acalculia, and anomia [10].
The secondary auditory area (Brodmann area 42) is located on the lateral surface of the superior temporal gyrus, just posterior to the primary auditory area [10]. Lesions in this area may result in word deafness, a condition in which the patient cannot interpret and identify heard sounds [1, 10].
Parietal lobe
The parietal lobe houses the primary somatosensory cortex, which lies just posterior to the central sulcus [16]. This region plays a vital role in processing sensory information from various parts of the body, contributing to the perception of touch, temperature, and pain.
The dominant parietal lobe is typically the left hemisphere. Damage to this area can lead to a condition known as Gerstmann’s syndrome, characterized by difficulties in writing (agraphia), challenges with mathematics, and finger agnosia [16]. These deficits highlight the importance of the dominant parietal lobe in language and numerical processing.
In contrast, the non-dominant parietal lobe is usually located in the right hemisphere. Damage to this area may result in agnosia of the contralateral side, a condition referred to as hemispatial neglect syndrome. Individuals with this syndrome may fail to attend to stimuli or respond to events occurring on the side opposite the damage [16].
The posterior parietal lobe plays a critical role in spatial awareness and orientation. Focal electrical stimulation of this area can lead to experiences often described as “out of body” sensations [17]. This underscores the importance of the posterior parietal lobe in integrating sensory information and contributing to our understanding of body position in space.
Occipital Lobe
The occipital lobe contains Brodmann’s areas 17, 18, and 19, which are responsible for various visual functions.
Brodmann’s area 17, also known as the primary visual area, receives optical fibers from the ipsilateral temporal retina and the contralateral nasal retina. It also receives input from the superior and inferior retinal quadrants. Lesions in this area can lead to contralateral homonymous hemianopia [10].
Brodmann areas 18 and 19 are known as the secondary visual areas. They receive input from the primary visual area (Brodmann area 17) and assist in recognizing objects based on past experiences [10]. Stimulation of these areas can produce deviations of the eyes to the opposite side.
Hippocampus
The hippocampus is located deep within the medial temporal lobe and is functionally divided into ventral, intermediate, and dorsal parts. It primarily functions in creating memories that can be consciously recalled, known as declarative memory, which can be episodic or semantic [9]. Patients who suffer hippocampal damage can recall memories of events that occurred before the damage [11].
Amygdala
The amygdala, an almond-shaped structure located deep within the temporal lobe, is associated with the function of fear [9]. It also plays a role in reward processing, learning motivation, and drug addiction. The primary role of the amygdala is to facilitate the adaptation of one’s emotions to their environment [12]. Negative emotions are associated with increased amygdala activity, while positive emotions decrease its activity [13].
Additionally, the amygdala has a significant role in the fight-or-flight response in vertebrates [14]. Kluver-Bucy syndrome is a rare disorder characterized by bilateral temporal lesions, particularly in the amygdala [15]. Patients with Kluver-Bucy syndrome exhibit hyperorality, hypersexuality, and bulimia [15].
Precentral Gyrus
Located in the precentral gyrus is the primary motor cortex (Brodmann area 4), which is responsible for performing voluntary movements [3]. It lies anterior to the central sulcus [1]. Anterior to the primary motor cortex is the premotor cortex (Brodmann area 6), which prepares proximal musculature for movement [4].
Superior, Middle, and Inferior Frontal Gyri
Divided by the inferior and frontal sulci, these gyri remain a topic of ongoing investigation [1]. Recent research has shown that the left (dominant) superior frontal gyrus is involved in memory and spatial processing [5], while the right (non-dominant) superior frontal gyrus is more involved in impulse control [6].
The left middle frontal gyrus is associated with literacy, while the right middle frontal gyrus is involved in numerical processing [7]. Furthermore, a study found that the middle gyri also plays a role in contingency awareness during conditioning [8].
Broca’s Motor Area
Broca’s motor area is located in Brodmann area 44 at the pars triangularis and Brodmann area 45 at the pars opercularis in the inferior frontal gyrus of the dominant hemisphere. These areas control the expression of words, and lesions in these regions can lead to motor aphasia.
Table 1 summarizes the mentioned areas above, and their main function in the brain.
| Area | Function |
| Primary motor cortex | Voluntary movements |
| Premotor cortex | Preparation of voluntary movements |
| Left superior frontal gyrus | Memory and spatial processing |
| Right superior frontal gyrus | Impulse control |
| Left middle frontal gyrus | Literacy |
| Right middle frontal gyrus | Numericals |
| Broca’s area (inferior frontal gyrus) | Speech production and expression |
| Wernicke’s area | Speech comprehension |
| Lateral surface of superior temporal gyrus | Identify heard sounds |
| Hippocampus | Declarative memory |
| Amygdala | Emotional adaptation to the environment |
| Dominant parietal lobe | Damage leads to acalculia and agraphia |
| Non-dominant parietal lobe (right) | Damage leads to contralateral hemineglect |
| Primary visual areas | Vision |
| Secondary visual areas | Recognition of visualized objects |
Table 1: main functional areas of the brain.
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