The lobes of the brain represent the four primary identifiable regions of the human cerebral cortex, collectively constituting the surface of each cerebral hemisphere. These two hemispheres exhibit approximate structural symmetry and are interconnected by the corpus callosum. While some classifications incorporate the insula and limbic lobe, the latter integrates components from other cortical regions. These lobes are extensive areas that are both anatomically distinguishable and functionally distinct. Each cerebral lobe features numerous gyri (ridges) and sulci (furrows), which form further subdivisions of the cortex. Typically, the term "lobes of the brain" specifically denotes those of the cerebrum, excluding the distinct cerebellar regions.
Frontal Lobe
The frontal lobe is situated in the anterior portion of each cerebral hemisphere, positioned anterior to the parietal lobe and superior-anterior to the temporal lobe. It is delineated from the parietal lobe by the central sulcus and from the temporal lobe by the deep lateral sulcus, also known as the Sylvian fissure. The precentral gyrus, which forms the posterior boundary of the frontal lobe, houses the primary motor cortex (Brodmann area 4), governing voluntary movements of specific somatic regions. Additionally, the precentral region encompasses the premotor cortex (Brodmann area 6).
The frontal lobe contains the majority of dopamine-sensitive neurons within the cerebral cortex. The dopaminergic system is implicated in reward processing, attention, short-term memory tasks, planning, and motivation. Dopamine modulates the selection and transmission of sensory information from the thalamus to the forebrain. Research from the National Institute of Mental Health indicates that a specific gene variant, which diminishes dopamine activity in the prefrontal cortex, correlates with reduced performance and impaired functioning of this brain region during working memory tasks, and is associated with a marginally elevated risk for schizophrenia.
The frontal lobe encompasses the prefrontal cortex, situated in its most anterior region. This area is crucial for working memory and executive control, facilitating the organization of goals and complex tasks.
The prefrontal cortex is subdivided into orbital, medial, and lateral regions. The lateral prefrontal cortex further comprises two distinct subdivisions: the dorsolateral and ventrolateral prefrontal cortex. Positioned superior to the ventrolateral prefrontal cortex, the dorsolateral prefrontal cortex primarily mediates executive control and the manipulation of episodically retrieved memories. Conversely, the ventrolateral prefrontal cortex plays a significant role in regulating meaningful stimuli encountered throughout an individual's life, including images, letters, and names.
Damage to the prefrontal cortex can result in deficits in both long-term and short-term memory, as well as induce alterations in behavior and impair planning and organizational capacities.
Damage may arise from surgically resected lesions or tumors, or from traumatic brain injuries (TBI) resulting from severe head trauma that induces cerebral swelling. Frequently, TBIs occur during childhood, often due to competitive sports or accidental impacts during typical play. Experiencing a TBI can elevate the risk of developing neuropsychiatric disorders, and substance abuse, particularly cannabis, is recognized as a risk factor for exacerbating schizophrenia-related symptoms. One study observed that schizophrenia symptoms (e.g., auditory hallucinations, delusions) intensified following cannabis use, suggesting that a childhood TBI may potentiate the development of psychosis through alterations in frontal-temporal white matter.
Parietal Lobe
The parietal lobe is situated superior to the occipital lobe and posterior to both the frontal lobe and the central sulcus.
The parietal lobe integrates diverse sensory information, encompassing spatial awareness and navigation (proprioception), the primary somatosensory cortex (located in the postcentral gyrus posterior to the central sulcus, which serves as the principal receptive area for mechanoreception or touch), and contributions to the dorsal stream of the visual system. Significant sensory inputs originating from the skin, including touch, temperature, and pain receptors, are relayed via the thalamus to the parietal lobe.
Multiple regions within the parietal lobe play crucial roles in language processing. The somatosensory cortex is often represented by a distorted anatomical map, known as the homunculus (from Latin, 'little man'), where body parts are proportioned based on the cortical area dedicated to their sensory representation. Both the superior and inferior parietal lobules are fundamental for body and spatial awareness. Damage, particularly to the right superior or inferior parietal lobule, frequently results in hemineglect.
Occipital lobe
The occipital lobe functions as the primary visual processing center in the mammalian brain, housing the majority of the visual cortex. Designated as Brodmann area 17, the primary visual cortex is frequently referred to as V1. In humans, V1 is situated on the medial aspect of the occipital lobe, specifically within the calcarine sulcus, often extending to the posterior pole of the lobe. V1 is also known as the striate cortex due to the prominent myelin stripe, the Stria of Gennari, which characterizes its histological appearance. Cortical areas involved in visual processing beyond V1 are collectively termed the extrastriate cortex. Numerous extrastriate regions exist, each specialized for distinct visual functions, including visuospatial processing, color discrimination, and motion detection.
Temporal lobe
The temporal lobe is situated inferior to the lateral fissure within both cerebral hemispheres of the mammalian brain.
The temporal lobe participates in transforming sensory input into meaningful interpretations, facilitating the retention of visual memories, language comprehension, and the association of emotions.
Within the temporal lobe resides the hippocampus, a brain region critically involved in the formation of new memories and learning processes. Historically, the hippocampus has been extensively investigated due to its correlation with epilepsy, often exhibiting damage in affected individuals. While establishing the precise relationship between the temporal lobe and epilepsy has proven challenging, Chauvière (2020) proposes a positive correlation between neuronal circuitry reorganization within the temporal lobe structure and its impact on rhythmic activities essential for cognition.
Limbic lobe
The limbic lobe constitutes an arc-shaped cortical region located on the medial surface of each cerebral hemisphere in the mammalian brain, comprising portions of the frontal, parietal, and temporal lobes. The nomenclature for this region is ambiguous; some researchers incorporate structures such as the paraterminal gyrus, subcallosal area, cingulate gyrus, parahippocampal gyrus, dentate gyrus, hippocampus, and subiculum. Conversely, the Terminologia Anatomica defines the limbic lobe to include the cingulate sulcus, cingulate gyrus, isthmus of cingulate gyrus, fasciolar gyrus, parahippocampal gyrus, parahippocampal sulcus, dentate gyrus, fimbrodentate sulcus, fimbria of hippocampus, collateral sulcus, and rhinal sulcus, notably excluding the hippocampus.
Insular cortex
The insular cortex represents a segment of the cerebral cortex deeply folded within the lateral sulcus, which demarcates the temporal lobe from the parietal and frontal lobes. This cortical region plays a significant role in projecting axons to the amygdala and in processing auditory tones and somatosensory stimuli.
Berret et al. (2019) investigated fear responses in mice, specifically those associated with perceived threats derived from memories of prior foot shocks. Their research revealed adverse reflex responses to noxious stimulation when the insular cortex was silenced. This evidence suggests that the insular cortex transmits information to distinct amygdala subdivisions, thereby contributing to various components of fear-related behaviors.
The insula is hypothesized to contribute to consciousness and is implicated in various functions typically associated with emotional processing and the maintenance of bodily homeostasis. These functions encompass perception, motor control, self-awareness, cognitive operations, and interpersonal interactions. Furthermore, its involvement extends to the domain of psychopathology.
The insular cortex comprises two distinct regions: the more substantial anterior insula and the comparatively smaller posterior insula, within which over a dozen specialized field areas have been delineated. The cortical region situated superior to the insula, extending towards the brain's lateral surface, is termed the operculum (derived from the Latin for lid). These opercula are constituted by segments of the surrounding frontal, temporal, and parietal lobes.
Illustrative Models
Cerebral Hemisphere Poles
- Poles of cerebral hemispheres
- Regions of the Human Brain
- Neuroanatomy
References
- Berger, Justus; Oltmanns, Frank; Holtkamp, Martin; Bengner, Thomas (2017). "Sex Differences in Verbal and Nonverbal Learning Before and After Temporal Lobe Epilepsy Surgery." Epilepsy & Behavior, 66, 57–63. doi:10.1016/j.yebeh.2016.11.037.Berret, Kintscher; Palchaudhuri, Tang; Osypenko, Kochubey; Schneggenburge (2019). "Insular Cortex Processes Aversive Somatosensory Information and Is Crucial for Threat Learning." Science, 364 (6443), 1–11.Chauvière (2020). "Potential Causes of Cognitive Alterations in Temporal Lobe Epilepsy." Behavioural Brain Research, 378, 112310. doi:10.1016/j.bbr.2019.112310.Jain; Srivastava (2017). "Frontal Lobe Abnormality and Psychosis in Traumatic Brain Injury and Cannabis Abuse." ASEAN Journal of Psychiatry, 18 (1).
- Lobes of the Brain detailed guide for medical college students and medical professionals.