1. Cerebral Cortex RegionsOverview of the Cerebral Cortex Regions
The cerebral cortex, enveloping the surface of the mammalian brain, stands as the epicenter for a plethora of advanced neural functions. Primarily constituted of gray matter, its intricate neuronal architecture gives rise to distinct regions, each responsible for specialized functions. Within the frontal lobe lies the Motor Cortex, a region pivotal to the control of voluntary motor movements. The Primary Motor Cortex (M1), situated on the precentral gyrus, takes the lead in initiating voluntary motor activity, dispatching neural impulses to the spinal cord which, in turn, govern muscle contractions. Adjacent to the primary motor cortex is the Premotor Cortex, a realm that orchestrates the planning and coordination of motor tasks. Meanwhile, more complex movements and their planning are influenced by the Supplementary Motor Area (SMA). Additionally, the control of voluntary eye movements rests with the Frontal Eye Fields. Diving deeper into the auditory dimensions, the Auditory Association Area, located in the temporal lobe, processes auditory information. The Primary Auditory Cortex (A1) serves as the primary hub for decoding basic auditory signals, like pitch and volume, with its information directly channeled from the medial geniculate nucleus of the thalamus. Surrounding A1 are the Belt Regions, which refine this auditory data by interpreting the complex characteristics of sounds. Further advanced processing, particularly the interfacing of auditory stimuli with other sensory modalities and cognitive processes, is managed by the Parabelt Regions. The visual perception framework is anchored by the Visual Association Cortex, found in the occipital lobe. The Primary Visual Cortex (V1), often termed the striate cortex, acts as the gateway for visual inputs, decoding fundamental attributes such as orientation and color. Adjacent to V1, the Secondary Visual Cortex (V2) elevates this basic processing by adding depth to the visual representation. Progressively, the Visual Areas V3 to V5 cater to the intricate aspects of visual recognition, including object properties and motion detection. Shifting to the parietal lobe, the Somatosensory Association Cortex serves as the nexus for bodily sensations, including touch, temperature, and proprioception. The Primary Somatosensory Cortex (S1) remains directly accountable for the initial processing of these sensations. Augmenting this, the Secondary Somatosensory Cortex (S2) refines tactile data, aiding in the identification of object attributes. Beyond tactile recognition, the Posterior Parietal Cortex amalgamates sensory data from both visual and somatosensory realms, underpinning spatial awareness and movement guidance. Lastly, nestled within the depths of the cerebral hemispheres, the Insula or Insular Cortex unfolds its multifaceted functions. The Anterior Insula delves into the realms of emotion, risk perception, and decision-making, while the Posterior Insula predominantly attends to somatosensory processes, channeling tactile and temperature information directly from the thalamus. Bridging these two regions, the Central Insula mediates the functions, providing a seamless interplay of emotional and sensory experiences.
The cerebral cortex is involved in several functions of the body including:
Determining intelligence
Determining personality
Motor function
Planning and organization
Touch sensation
Processing sensory information
Language processing
The cerebral cortex contains:
1. Sensory areas: receive input from the thalamus and process information related to the senses. They include the visual cortex of the occipital lobe, the auditory cortex of the temporal lobe, the gustatory cortex, and the somatosensory cortex of the parietal lobe. Within the sensory areas are association areas that give meaning to sensations and associate sensations with specific stimuli.
2. Motor areas: including the primary motor cortex and the premotor cortex, regulate voluntary movement Source: Physiopedia: Brain function related to anatomy
1. Visual Association CortexVisual Association Cortex in the Occipital LobeSituated at the posterior end of the cerebral hemisphere, the occipital lobe primarily serves as the neural epicenter for visual processing. Dominating this domain is the Visual Association Cortex, a constellation of interconnected regions tasked with the intricate job of translating incoming light signals into meaningful visual perceptions. The Primary Visual Cortex (V1), also christened the striate cortex due to its striped appearance under certain staining techniques, stands at the forefront of visual processing. Acting as the brain's primary reception desk for visual signals, V1 is entrusted with decoding foundational visual elements: the orientation of lines, spatial frequencies, and color nuances. Immediately adjoining V1 is the Secondary Visual Cortex (V2), a realm where the basic visual data undergoes a more nuanced analysis. Here, the elemental visual cues from V1 are embellished with additional layers of detail, producing a richer visual tapestry. Further diversifying the visual processing are specialized areas like Visual Area V3—key in discerning object shapes, Visual Area V4—a hub for color processing and texture perception, and Visual Area V5 or MT, where the dynamic world comes to life as it deciphers motion cues. Beyond the macro structures, the microscopic neuronal canvas of the Visual Association Cortex reveals an assortment of cell types, each sculpting the visual experience in unique ways. Pyramidal Cells, the principal excitatory units, weave the narrative of the visual story and relay it to other brain locales. Assisting them are the inhibitory Interneurons, which, in their myriad forms—be it basket cells or chandelier cells—refine the visual signal, ensuring clarity and precision. Central to maintaining this precision are the GABAergic Interneurons, the custodians of neural balance, preventing hyperactivity and ensuring the visual narrative remains coherent. Delving deeper, the Spiny Stellate Cells in layer IV act as intermediaries, processing inputs from the thalamus. Lastly, the Martinotti Cells, with their inhibitory prowess, modulate the pyramidal cell activity, orchestrating a symphony of feedback loops, which is quintessential for adaptive and dynamic visual processing. In essence, the Visual Association Cortex in the occipital lobe is not just a passive receiver but a dynamic processor, translating the world's visual cacophony into meaningful, interpretable experiences.
Visual Association Cortex SubdivisionsPrimary Visual Cortex (V1): Often called the striate cortex, this is the main entry point for visual information coming into the brain. It is responsible for the basic processing of visual stimuli such as orientation, spatial frequency, and color.
Secondary Visual Cortex (V2): Directly adjacent to V1, V2 plays a role in further processing the visual information, adding complexity to the representation.
Visual Area V3: Contributes to processing the properties of objects such as their shape.
Visual Area V4: Associated with processing color information and the perception of visual texture.
Visual Area V5 (MT): Specialized for the processing of motion information.
Cell Types in Visual Association CortexPyramidal Cells: These excitatory neurons form the primary output cells of the visual cortex, processing and relaying visual information to other parts of the brain.
Interneurons: Inhibitory neurons that play a key role in processing visual information within the cortex. Subtypes include basket cells, chandelier cells, and double bouquet cells, each contributing to the intricate processing of visual information.
GABAergic Interneurons: A subset of interneurons that use GABA as their neurotransmitter, they play a role in inhibiting over-activity and in fine-tuning visual information.
Spiny Stellate Cells: Excitatory neurons found primarily in layer IV of the visual cortex. They play a role in processing thalamocortical inputs.
Martinotti Cells: These GABAergic interneurons influence the activity of pyramidal cells, contributing to feedback inhibition in visual processing.
2. Association AreaTemporal Lobe and Its Association AreasNestled along the sides of the cerebral hemisphere, beneath the lateral sulcus, the temporal lobe serves as a multifaceted center for a myriad of critical brain functions. While it is often heralded for its pivotal role in auditory processing, thanks to the auditory cortex, the temporal lobe's responsibilities are far more diverse and intricate. One of the key components of the temporal lobe is the auditory cortex, responsible for decoding and interpreting sounds. It meticulously processes various sound attributes, from frequency to amplitude, enabling us to discern a whisper from a shout or a violin from a trumpet. Adjacent to the auditory realms lies the Wernicke's area, a cornerstone for language comprehension. Damage to this area can lead to receptive aphasia, a condition where speech remains fluent but devoid of meaningful content due to an inability to comprehend language inputs. Moreover, the temporal lobe plays an indispensable role in memory. The hippocampus, buried deep within, is a linchpin for the formation of new memories. Acting as a scribe, it takes transient daily experiences and consolidates them into long-term memory storage. Beyond memory and auditory functions, the temporal lobe is also entwined with the processing of complex stimuli such as faces. The fusiform face area, specialized in facial recognition, allows us to identify familiar faces in a crowd, distinguishing friends from strangers. Furthermore, the anterior part of the temporal lobe, encompassing the amygdala, is the epicenter of emotional regulation. The amygdala, often termed the brain's emotional sentinel, appraises emotional content, be it joy, fear, or sorrow, and elicits appropriate physiological responses. Embedded within the vast territories of the temporal lobe are association areas that integrate information from diverse sensory modalities. They don't merely process raw sensory data but interlace them with past experiences, providing context and meaning. For instance, when we hear a familiar song, it's not just the auditory cortex at work. The association areas retrieve memories associated with the tune, evoking emotions or recalling specific past events. In a neuroanatomical tapestry as rich as the brain, the temporal lobe stands out as a hub of auditory processing, memory formation, emotional regulation, and multisensory integration. Its association areas ensure that we don't merely perceive the world around us but also relate to it in meaningful ways, making our experiences both coherent and contextually relevant.
Temporal Lobe SubdivisionsSuperior Temporal Gyrus: Positioned at the top of the temporal lobe, this region is instrumental in auditory processing and houses the primary auditory cortex. Additionally, it contains Wernicke's area, crucial for language comprehension.
Middle Temporal Gyrus: Located below the superior temporal gyrus, this section is involved in processing semantic memory, recognition of known faces, and some aspects of language comprehension.
Inferior Temporal Gyrus: Situated at the bottom part of the temporal lobe, it plays a role in visual processing, particularly the identification and recognition of complex objects like faces.
Parahippocampal Gyrus: This region is pivotal for memory encoding and retrieval, and it provides contextual information about the environment, aiding in spatial memory.
Fusiform Gyrus: Located on the ventral side of the temporal lobe, this area is essential for recognizing faces, words, and, to some extent, color processing.
Amygdala: Deeply embedded within the anterior portion of the temporal lobe, the amygdala is paramount for emotional processing and forming emotional memories.
Hippocampus: Positioned adjacent to the amygdala, the hippocampus is fundamental for the formation of new memories and spatial navigation.
Entorhinal Cortex: Serving as a gateway between the hippocampus and the rest of the brain, this region is involved in memory and navigation. It's also one of the earliest regions affected in Alzheimer's disease.
These subdivisions collectively underscore the multifaceted roles of the temporal lobe, encompassing auditory processing, memory, emotion, and multisensory integration.
Cell Types Shared Across Temporal Lobe Subdivisions:
The temporal lobe, like other parts of the cortex, has some common cell types across its regions. However, specific areas within the temporal lobe might have unique cellular structures or particular arrangements suited to their specialized functions.
Superior Temporal Gyrus Neuronal CellsPyramidal Cells:
- Principal excitatory output neurons.
- Characterized by a large apical dendrite projecting towards the cortical surface.
Interneurons:
- Generally inhibitory and crucial for modulating the activity of pyramidal cells and other neurons.
- Include several subtypes:
- Basket Cells: These cells have axons that form basket-like structures around the cell bodies of target neurons. They play a role in regulating the output of pyramidal cells.
- Chandelier Cells: Recognizable by their unique axonal cartridges that target the axon initial segment of pyramidal neurons.
- Martinotti Cells: Target the distal dendrites of pyramidal cells and are involved in feedback inhibition.
- Double Bouquet Cells: Feature axons that form two bundles, which spread out in opposite directions in a columnar manner.
Spiny Stellate Cells:
- Excitatory neurons found in certain layers.
- Feature spine-covered dendrites radiating from the cell body, resembling a star shape.
Glia:
- Non-neuronal cells that provide support and protection. While not neurons, they play a critical role in the brain's function.
- Astrocytes: Involved in nutrient supply to neurons and maintaining the blood-brain barrier.
- Oligodendrocytes: Produce the myelin sheath around axons in the central nervous system.
- Microglia: Act as the brain's immune cells, clearing out dead cells and other debris.
While this area mostly houses the standard cortical cell types, its unique function in auditory processing might involve specialized circuitry of these common cells.
Middle Temporal GyrusPyramidal Cells and Interneurons: While detailed subtypes specific to this gyrus are under research, these standard cell types are consistent across cortical areas. Specific cellular configurations supporting its role in semantic memory and language comprehension are still under research, but the general cell types are consistent with other cortical areas.
Inferior Temporal GyrusPyramidal Cells and Interneurons: As with the Middle Temporal Gyrus, standard cortical cells are present, arranged for complex visual processing. Standard cortical cells, but with arrangements supporting complex visual processing.
Parahippocampal Gyrus Specific Cells Though it contains typical cortical cells, there might be some specific configurations interfacing with the hippocampus. General cell types support their respective roles in memory encoding, retrieval, face, and word recognition.
Fusiform Gyrus Specific CellsCommon cortical cell types arranged in a way that supports its role in face and word recognition.
Amygdala Specific Cells Apart from the common types, the amygdala contains:
Spiny Projection Neurons: These are output neurons that help in relaying information from the amygdala to other brain regions.
Specialized interneurons cater to its emotional functions.
Hippocampus Specific Cells Distinct from other regions, the hippocampus has:
Granule Cells of the dentate gyrus.
Pyramidal neurons are specific to CA regions. CA regions refer to the distinct regions within the hippocampus, a critical brain structure involved in learning and memory. The term "CA" comes from the Latin "Cornu Ammonis," which means "Ammon's horn." This name was given due to the hippocampus's horn-like appearance in certain cross-sectional views. The hippocampus is divided into four main CA regions: CA1 CA2 CA3 CA4 Pyramidal neurons are the primary excitatory neurons found in these regions, and they play a crucial role in the synaptic plasticity that underlies learning and memory. The precise properties and functions of pyramidal neurons can vary between these CA regions.
Mossy Cells: These excitatory relay neurons are primarily found in the hilus of the dentate gyrus.
Entorhinal Cortex-Specific Cells Apart from the common types, the entorhinal cortex has:
Stellate Cells in layer II: These excitatory neurons are pivotal for the grid cell system involved in spatial navigation.
Thus, there are a total of six distinct cell types mentioned for the Temporal Lobe subdivisions. However, it's important to note that this is a simplification. The brain, particularly regions like the temporal lobe, contains a vast diversity of neuronal types with specialized properties, functions, and interconnections. Even within these broad categories, there can be further subtypes and nuances based on molecular markers, electrophysiological properties, and connectivity patterns.
3. Motor CortexThe Motor Cortex, a component of the cerebral cortex, plays a pivotal role in the planning, control, and execution of voluntary motor functions. Situated in the posterior portion of the frontal lobe, it is anatomically delineated into different areas, each having specific functions related to motor activity. The Primary Motor Cortex (M1), located along the precentral gyrus, serves as the main contributor to generating neural impulses that command voluntary muscle contractions. M1 neurons, through their long axons, form synapses with neurons in the spinal cord, which then relay the signals to muscles, instructing them to contract or relax. The organization of M1 is somatotopic, meaning different parts of the cortex control different parts of the body, an arrangement often referred to as the "motor homunculus." Adjacent to M1 lies the Premotor Cortex, which is involved in the preparation and guidance of movements. This region, by integrating sensory and motor information, facilitates movements in response to external stimuli. Another crucial segment of the motor cortex is the Supplementary Motor Area (SMA). Positioned on the medial surface of the hemisphere, anterior to M1, the SMA is implicated in the planning and initiation of movements, particularly those that are self-generated or sequential. The cell composition in the motor cortex is diverse, aiding its complex functions. The Pyramidal Cells stand out as the principal excitatory neurons, sending axons to distant cortical and subcortical areas. Conversely, a variety of Interneurons provides local inhibition, refining motor signals and preventing unwanted movements. Among these, the GABAergic Interneurons play a cardinal role in maintaining the balance of excitation and inhibition. The functionality of the motor cortex is not isolated; it communicates extensively with other brain areas like the parietal lobe for sensory integration, and the basal ganglia and cerebellum for motor coordination. This intricate neural network ensures the seamless execution of motor tasks, from simple limb movements to complex actions.
Motor Cortex SubdivisionsPrimary Motor Cortex (M1): This is the main contributor to generating neural impulses that pass down to the spinal cord and control the execution of movement.
Premotor Cortex: Located just anterior to the Primary Motor Cortex. It's responsible for some aspects of motor control, possibly including the preparation for movement, the sensory guidance of movement, or the direct control of some movements.
Supplementary Motor Area (SMA): It plays a role in the planning and coordination of complex movements.
Frontal Eye Fields (FEF): Controls voluntary eye movements.
Cell Types in Motor Cortex SubdivisionsPyramidal Cells: These are the primary excitation units in the mammalian prefrontal cortex and the corticospinal tract. Their axons are the main carriers of communication between the cortex and spinal cord.
Interneurons: These are inhibitory neurons that play key roles in the processing of information within the cortex. They can be further divided into several subtypes, such as basket cells and chandelier cells, based on their functions and morphologies.
GABAergic Interneurons: A subset of interneurons that use GABA (gamma-aminobutyric acid) as their neurotransmitter and play crucial roles in inhibiting neuronal activity.
Spiny Stellate Cells: These are excitatory neurons found primarily in layer IV of the cortex. They receive inputs from the thalamus and process sensory information.
Martinotti Cells: These are a type of GABAergic interneuron which influences the activity of pyramidal cells.
4. Broca's AreaThe Broca's Area, named after the 19th-century French physician Paul Broca, is a critical region in the brain associated with language processing, specifically implicated in speech production and grammatical processing. Located in the posterior part of the frontal lobe, typically in the left hemisphere, this region encompasses parts of Brodmann areas 44 and 45. Broca's Area's significance became apparent when patients with damage to this region exhibited specific linguistic deficits, a condition now termed Broca's aphasia. Individuals with Broca's aphasia can comprehend language relatively well but struggle with fluent speech production, often producing telegraphic speech devoid of complex grammar. Their speech, while meaningful, tends to be halting and laborious. Functional imaging studies, including fMRI, have illustrated that the Broca's Area activates during tasks demanding language production, whether spoken or signed. Moreover, it's engaged when processing complex sentence structures, suggesting its role in syntactical aspects of language. In addition to its classical role in speech production, recent research posits that Broca's Area is also involved in other cognitive tasks, such as action understanding and working memory, hinting at its broader role in cognition. Connections between the Broca's Area and other brain regions, notably the Wernicke's Area (involved in language comprehension), facilitate the intricate process of language production and comprehension. This connectivity ensures the coordination between understanding incoming linguistic information and producing coherent, meaningful speech. It's imperative to note that while Broca's Area is typically located in the left hemisphere for right-handed individuals, its position can vary. In some left-handed people, it might be found in the right hemisphere or be represented in both hemispheres, illustrating the brain's remarkable plasticity and individual variability in its functional architecture.
Broca's Area SubdivisionsBroca's Area, situated in the posterior part of the frontal lobe, primarily in the left hemisphere, plays a crucial role in language production and processing. This region encompasses two primary subdivisions:
Brodmann Area 44 (BA44): Also known as the pars opercularis, this area is located within the inferior frontal gyrus. BA44 is closely linked to syntactical processing in language, managing the structure and grammar of sentences.
Brodmann Area 45 (BA45): Referred to as the pars triangularis, BA45 lies adjacent to BA44. This subdivision plays a significant role in semantic processing, aiding in understanding word meaning and context.
These two areas, while distinct in their functions, collaborate intricately to facilitate complex linguistic processes. Their combined efforts allow for both the formation of grammatically correct sentences and the comprehension of nuanced linguistic information.
Cell Types in Broca's AreaPyramidal Cells: The primary excitatory neurons in the cerebral cortex, these cells play a key role in information processing and output. They feature a characteristic triangular-shaped soma and have long apical dendrites.
Interneurons: These are inhibitory neurons that modulate the activity of pyramidal cells and other neurons in the cortex. Their role is crucial in maintaining a balance between excitation and inhibition.
GABAergic Interneurons: A subset of interneurons that predominantly release the inhibitory neurotransmitter GABA (gamma-aminobutyric acid). These cells are instrumental in inhibiting over-excitation within the cortex.
Spiny Stellate Cells: Excitatory neurons, primarily found in layer IV of the cortex, that play a role in processing inputs from the thalamus.
Martinotti Cells: These are a subtype of GABAergic interneurons found throughout different layers of the cortex. They play a role in modulating the output of pyramidal cells.
The diverse interplay of these neuronal types ensures the nuanced and complex processing capabilities of Broca's area, particularly in linguistic functions.
5. Auditory Association AreaAuditory Association Area SubdivisionsPrimary Auditory Cortex (A1): This is the main region for the basic processing of auditory information in the brain. It receives direct projections from the medial geniculate nucleus of the thalamus and is responsible for the basic decoding of sounds such as pitch and volume.
Belt Regions: These are secondary auditory cortical areas surrounding A1. They process more complex properties of auditory stimuli, and they have more diverse and diffuse input sources compared to A1.
Parabelt Regions: Located lateral to the belt regions, they are involved in higher order processing of auditory information, interfacing with other sensory modalities and higher cognitive processes related to sound.
Cell Types in Auditory Association AreaPyramidal Cells: These neurons are excitatory in nature and form the main output cells of the auditory cortex. They process and relay auditory information to other parts of the brain.
Interneurons: These inhibitory neurons help in refining and processing auditory signals within the cortex. They can be further classified into subtypes such as basket cells, chandelier cells, and double bouquet cells based on their morphology and functions.
GABAergic Interneurons: A subset of interneurons that use GABA as their neurotransmitter. They play crucial roles in inhibiting over-excitation and maintaining a balance in auditory processing.
Stellate Cells: These are excitatory neurons found primarily in layer IV of the auditory cortex. They play a role in processing thalamocortical inputs.
Martinotti Cells: These GABAergic interneurons are found in all layers of the cortex and have long axons that extend vertically through the cortex, influencing pyramidal cells and playing a role in feedback inhibition.
Interneuron Subtypes in the Cortex:Parvalbumin-expressing (PV) Interneurons: These are fast-spiking interneurons and include cell types like basket and chandelier cells. They play a crucial role in regulating the output of pyramidal cells.
Somatostatin-expressing (SST) Interneurons: These interneurons typically have a slower firing rate and target the distal dendrites of pyramidal cells. They play roles in regulating dendritic computations.
VIP-expressing Interneurons: These are disinhibitory interneurons, meaning they often inhibit other inhibitory neurons. They play a role in balancing the overall levels of inhibition in cortical circuits.
Neuropeptide Y (NPY) Interneurons: While some SST and PV interneurons can also express NPY, there are certain interneurons for which NPY is the primary marker. They have diverse roles in modulating neural circuits.
Calretinin-expressing (CR) Interneurons: These interneurons are typically found in the superficial layers of the cortex and can have a range of firing patterns.
There are also other, less common types and subtypes of interneurons that can be identified based on a combination of molecular markers, electrophysiological properties, and anatomical characteristics. This rich diversity allows for the intricate and nuanced processing capabilities of the cortex.
6. Insular Cortex (Emotional Area)The insular cortex, commonly referred to as the insula, is a multifaceted region nested within the lateral sulcus, between the temporal and frontal lobes. Its intricate anatomy, characterized by short and long gyri, provides a foundation for a plethora of functions. A significant role of the insula is in the processing of emotions. The insula integrates sensory and affective information to form a subjective emotional experience. This subjective awareness not only extends to our own internal emotional states but also aids in empathetic understanding, allowing us to discern and resonate with the emotions of others. Beyond its emotional roles, the insula serves as a hub for interoceptive awareness. This refers to its capacity to sense and interpret stimuli originating from within the body. Such stimuli can range from heartbeats and respiratory rhythms to visceral sensations from the gut. By continually gauging this internal milieu, the insula provides an ongoing status report, integrating bodily states into conscious awareness and contributing to feelings such as hunger, pain, or even the flush of embarrassment. The insula's multifunctionality doesn't end there. It's actively engaged in tasks involving taste, vestibular information, and even certain cognitive functions, making it a salient region for the perception of the environment relative to oneself. One cannot discuss the insula without noting its relevance in clinical contexts. Malfunctions or alterations in insular activity have been associated with conditions such as anxiety disorders, addiction, and schizophrenia. Additionally, its role in pain processing makes it a focal point in chronic pain syndromes and related treatments. In the brain, the insular cortex emerges as a linchpin, weaving together internal sensations, emotions, and cognitive processes to shape our subjective experience of the world. By bridging our internal and external realities, it plays an indelible role in shaping how we perceive, interact with, and feel about the world around us.
Cell Types in the Insular CortexPyramidal Cells: The primary excitatory neurons of the insular cortex, these cells have a distinctive pyramid shape and play a pivotal role in information processing and transmission. They are principal output neurons, projecting to other regions of the brain.
Interneurons: These are predominantly inhibitory neurons responsible for modulating neural activity within the insular cortex. They come in a variety of subtypes, including:
Basket Cells: Characterized by their axons forming basket-like structures around the soma of target neurons, they play a role in regulating the output of pyramidal cells.
Chandelier Cells: Named for their unique morphology resembling a chandelier, they have a specific inhibitory role on the axon initial segment of pyramidal neurons.
GABAergic Interneurons: These are a subset of interneurons that use gamma-aminobutyric acid (GABA) as their primary neurotransmitter. They are fundamental in maintaining the balance of excitation and inhibition in neural circuits, thereby ensuring stable neural activity.
Spiny Stellate Cells: Primarily found in certain layers of the insular cortex, these excitatory neurons are essential for processing specific sensory inputs. They exhibit a star-shaped (stellate) morphology and are recognized for their spiny dendrites.
Martinotti Cells: These are GABAergic interneurons found throughout the insular cortex. They have long axons that project vertically through the cortical layers, modulating the activity of pyramidal cells and playing a crucial role in feedback mechanisms.
While these are some of the primary cell types present in the insular cortex, the intricate functioning of this region arises from a dynamic interplay among these cells, with each type having specialized roles that contribute to the cortex's overall function.
7. Sensory Association Area Somatosensory Association CortexSomatosensory Association Cortex SubdivisionsPrimary Somatosensory Cortex (S1): This region is directly responsible for processing somatic sensations, or sensations from the body, such as touch, temperature, pain, and proprioception (awareness of body position).
Secondary Somatosensory Cortex (S2): Adjacent to S1, it further processes the tactile information sent from S1, contributing to the recognition of objects' shapes, sizes, and textures.
Posterior Parietal Cortex: This region integrates sensory information from the visual and somatosensory systems, playing a role in spatial awareness and guidance of movements.
Cell Types in Somatosensory Association CortexPyramidal Cells: These are excitatory neurons that form the primary output cells of the somatosensory cortex, processing and relaying sensory information to other parts of the brain.
Interneurons: These inhibitory neurons play an essential role in processing information within the cortex. They can be further divided into several subtypes, such as basket cells and chandelier cells, based on their morphology and functions.
GABAergic Interneurons: A subset of interneurons that use GABA (gamma-aminobutyric acid) as their neurotransmitter and play crucial roles in inhibiting neuronal activity.
Spiny Stellate Cells: Excitatory neurons that play a role in processing sensory input. They are primarily found in layer IV of the cortex, receiving thalamocortical inputs.
Martinotti Cells: These GABAergic interneurons influence the activity of pyramidal cells, contributing to feedback mechanisms in sensory processing.
Insula (Insular Cortex)Insular Cortex SubdivisionsAnterior Insula: This part of the insula is involved in processes related to emotion, risk perception, and decision-making.
Posterior Insula: Primarily related to somatosensory processes. It receives direct inputs from the thalamus, which relays tactile and temperature information.
Central Insula: Acts as a transitional zone between the anterior and posterior regions. It has functions associated with both those zones.
Cell Types in Insular CortexPyramidal Cells: These are the principal output neurons in the insular cortex, responsible for transmitting information to other brain areas.
Interneurons: These are inhibitory neurons that modulate the activity of pyramidal cells and other cells within the cortex. Their diverse subtypes, such as basket cells and chandelier cells, allow for fine-tuning of neural networks.
GABAergic Interneurons: These interneurons utilize the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) to reduce neuronal activity within the insular cortex.
Spiny Stellate Cells: These excitatory neurons play a role in processing sensory and emotional inputs within the insula. They have spiny dendrites and a star-shaped morphology.
Martinotti Cells: As GABAergic interneurons, they modulate the activity of pyramidal cells and are essential for certain feedback mechanisms within cortical layers.
