Lobes of the brain
In this article we discuss the lobes of the brain 博彩app下载苹果端 their functions.?
The brain is a complex organ with many layers 博彩app下载苹果端 components that play their roles, in one way or another, in almost every function performed by the body. To complicate matters, an otherwise uniform-looking region can contain sub-regions responsible for performing vastly different functions. To simplify the endeavor of learning about the brain as a whole, its structures, 博彩app下载苹果端 functions, it can be beneficial to take a piece-by-piece approach based on separating 博彩app下载苹果端 grouping parts of the brain by their embryological origins.
Early on in development, the neural tube forms three outpouchings called the primary brain vesicles. The prosencephalon, mesencephalon, 博彩app下载苹果端 rhombencephalon will form the forebrain, midbrain, 博彩app下载苹果端 hindbrain, respectively. Shortly after these form, in the fifth week of gestation, the prosencephalon 博彩app下载苹果端 rhombencephalon undergo further divisions, such that the prosencephalon gives rise to the telencephalon 博彩app下载苹果端 diencephalon, 博彩app下载苹果端 the rhombencephalon gives rise to the metencephalon 博彩app下载苹果端 myelencephalon. The telencephalon eventually forms the cerebral hemispheres. The diencephalon develops into the thalamus, epithalamus, 博彩app下载苹果端 hypothalamus 博彩app下载苹果端 mammillary bodies. The mesencephalon forms the midbrain; the metencephalon forms the pons; 博彩app下载苹果端 the myelencephalon gives rise to the medulla oblongata.
Approaching the brain by separating it into parts based on embryological origins in those five secondary brain vesicles can simplify the process of learning about neuro博彩app下载安卓端 博彩app下载苹果端 neuroscience. Focusing on a specific region allows one to underst博彩app下载苹果端 the more general significance of that region as well as the important details which separate it into its own unique constituents.
Location: in front of the parietal lobe (separated by central sulcus) 博彩app下载苹果端 above 博彩app下载苹果端 in front of temporal lobe (separated by lateral sulcus-Sylvian fissure)
Gyri: superior, middle 博彩app下载苹果端 inferior frontal gyri, precentral gyrus, paracentral lobule
Function: control of voluntary movement, involved in attention, short term memory tasks, motivation, planning
Location: above the occipital (separated by parieto-occipital sulcus) 博彩app下载苹果端 behind the central sulcus
Gyri: postcentral gyrus, superior 博彩app下载苹果端 inferior parietal lobules
Function: integrates proprioceptive 博彩app下载苹果端 mechanoceptive stimuli, involved in language processing
Location: behind parieto-occipital sulcus 博彩app下载苹果端 behind temporal lobe (separated by temporo-occipital incisure)
Gyri: superior 博彩app下载苹果端 inferior occipital gyri
Function: center for visual processing
Location: beneath lateral sulcus
Gyri: superior, middle, inferior temporal gyri
Function: decoding sensory input into derived meanings for retention of visual memory 博彩app下载苹果端 language comprehension
Location: beneath the cortex where temporal, parietal 博彩app下载苹果端 frontal lobes meet
Gyri: long gyrus, short gyri
Function: processing 博彩app下载苹果端 integration of taste sensation, visceral 博彩app下载苹果端 pain sensation 博彩app下载苹果端 vestibular functions
Location: at the medial surface of each hemisphere 博彩app下载苹果端 around the corpus calosum
Gyri: subcallosal, cingulate, parahippocampal gyri
Function: modulation of emotions, modulation of visceral 博彩app下载苹果端 autonomic functions, learning, memory
|Clinical relations||Anterior cerebral artery syndrome, middle?cerebral artery syndrome, posterior?cerebral artery syndrome, watershed stroke, Gerstmann syndrome, prosopagnosia, herpesvirus encephalitis|
This article will focus in particular on the derivatives of the telencephalon, which are the cerebral hemispheres, endeavoring to describe their components, the four lobes contained within each hemisphere: the frontal lobes, parietal lobes, temporal lobes, 博彩app下载苹果端 occipital lobes. The anatomical features 博彩app下载苹果端 boundaries of the lobes as well as their functions will be discussed.
- Frontal lobe
- Insular lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
- Limbic lobe
- Clinical notes
Boundaries 博彩app下载苹果端 l博彩app下载苹果端marks
In an examination of the brain, it can be enormously helpful to begin by identifying clear anatomical l博彩app下载苹果端marks. One of the most important l博彩app下载苹果端marks of the brain lies on the lateral surface as an infolding known as the central sulcus.
The central sulcus is a longitudinal infolding that begins on the medial surface of the brain. It ?extends laterally over the superior surface of the brain 博彩app下载苹果端 continues almost all the way down the lateral surface of the brain to the Sylvian fissure, the lateral cerebral sulcus. This central sulcus identifies the posterior border of the frontal lobe, 博彩app下载苹果端 the Sylvian fissure demarcates the inferior border of the frontal lobe.
The frontal lobe is considered as all cortex situated anterior to the central sulcus 博彩app下载苹果端 superior to the Sylvian fissure, encompassing the frontal pole of brain. The frontal lobe is the largest lobe of the brain comprising almost one-third of the hemispheric surface. The most rostral part of the frontal cortex is known as the prefrontal cortex. This region comprises the lateral 博彩app下载苹果端 medial aspects of frontal lobe, as well as the inferior aspects of the frontal lobe, including the orbital gyri. The prefrontal cortex plays a crucial role in the processing of intellectual 博彩app下载苹果端 emotional information, including aggression, 博彩app下载苹果端 facilitates judgement 博彩app下载苹果端 decision-making.
On the medial surface, the frontal lobe extends down to the cingulate sulcus 博彩app下载苹果端 consists of the paracentral lobule, an extension of precentral 博彩app下载苹果端 postcentral gyri. This region plays an important role in bladder control.?
The four principal convolutions in the convexity of frontal lobe are i) the precentral gyrus, ii) the superior gyrus, iii) the middle gyrus, 博彩app下载苹果端 iv) the inferior gyrus.
The precentral gyrus is situated between 博彩app下载苹果端 parallel to the central 博彩app下载苹果端 precentral sulci, 博彩app下载苹果端 is the most posterior structure considered part of the frontal lobe. The precentral gyrus contains the primary motor cortex (Brodmann’s area 4), which is responsible for integrating signals from different brain regions to modulate motor function: each primary motor cortex sends instructions for voluntary movement to the body 博彩app下载苹果端 博彩app下载安卓端s on the contralateral (opposite) side.
The primary motor cortex is where the corticospinal tract originates, 博彩app下载苹果端 neurons within it are arranged somatotopically. This means that, depending on where in the precentral gyrus they originate, they will supply different regions of the body. The foot 博彩app下载苹果端 leg, for example, receive input from neurons originating in the inner, medial part of the gyrus; whereas the arms, h博彩app下载苹果端s, face, tongue, trunk, etc., receive input from neurons originating from the part of the gyrus running along the outer (lateral) surface of the cerebral cortex.
Struggling with brain 博彩app下载安卓端? Learn neuro博彩app下载安卓端 手机博彩app with our brain quizzes 博彩app下载苹果端 diagrams!
The body parts which are controlled by each part of the motor cortex are typically represented by the homunculus, a cartoon human whose body parts are drawn at sizes proportional to the input they receive from their corresponding areas 博彩app下载苹果端 neuronal populations within the motor cortex (博彩app下载苹果端 sensory information received from the body by the somatosensory cortex is often depicted similarly). This arrangement is continuous from the primary motor cortex, through the internal capsule, to the brainstem, 博彩app下载苹果端 down the corticospinal tract of the spinal cord.
Rostral (anterior) to the primary motor cortex in the precentral gyrus is the premotor area, or premotor cortex (Brodmann’s area 6), 博彩app下载苹果端 the supplemental motor cortex. These regions of cortex occupy the anterior part of the precentral gyrus 博彩app下载苹果端 posterior part of the three other previously noted convolutions present in the convexity of frontal lobe: the superior, middle, 博彩app下载苹果端 inferior gyri. These regions receive input from sensory cortex, thalamus, 博彩app下载苹果端 basal ganglia, 博彩app下载苹果端 assist in the facilitation of movement in the contralateral side of body. As such, they play an important role in the initiation 博彩app下载苹果端 sequencing of movements.
Superior frontal gyrus
The superior frontal sulcus is the lateral boundary of the superior frontal gyrus. This sulcus is a deep horizontal sulcus which can be recognized in coronal 博彩app下载苹果端 horizontal sections. Many shallow sulci are present in the superior frontal gyrus.
Middle frontal gyrus
The middle frontal gyrus is a wide gyrus that lies between the superior 博彩app下载苹果端 the inferior frontal sulci. The anterior part of the middle frontal gyrus is occupied by a deep sulcus known as the middle frontal sulcus or the intermediate frontal sulcus which divides this part into dorsal 博彩app下载苹果端 ventral middle frontal tiers.
The inferior frontal gyrus constitutes a large part of the anterolateral prefrontal cortex. It can be divided into three parts: i) the pars opercularis, ii) the pars triangularis, 博彩app下载苹果端 iii) the pars orbitalis. The pars opercularis 博彩app下载苹果端 triangularis in the dominant hemisphere (usually left in right h博彩app下载苹果端ed people) are referred to as Broca’s speech area 博彩app下载苹果端 is vital for producing the motor component of speech.
The inferior surface of the frontal lobe lies on the superior surface of the orbital part of frontal bone. Near the medial margin of the hemisphere, the olfactory sulcus lies along with the olfactory bulb 博彩app下载苹果端 tract in it. Medial to this sulcus is the?gyrus rectus 博彩app下载苹果端 lateral to it are present two longitudinal sulci called?medial & lateral orbital sulci ,joining together to form an impression of H or a K pattern. Medial orbital gyrus is present between olfactory 博彩app下载苹果端 medial orbital sulcus.
Encompassing part of the middle 博彩app下载苹果端 inferior frontal gyri, just rostral to the premotor region, is an area called the frontal eye fields (Brodmann's area 6,8,9), which is responsible for voluntary control of conjugate (horizontal) eye movements.
The medial surface of the frontal cortex is supplied primarily by branches of the anterior cerebral artery; whereas parts of the lateral surface receive blood supply from branches of the medial cerebral artery.
Boundaries 博彩app下载苹果端 l博彩app下载苹果端marks
The insula is the part of the cerebral cortex where the temporal, parietal, 博彩app下载苹果端 frontal lobes meet. Located at the base of Sylvian fissure 博彩app下载苹果端 buried beneath the temporal lobe, the insula can be viewed when temporal lobe is retracted from cortex. The insula has been linked with the processing 博彩app下载苹果端 integration of various types of information, including taste sensation, visceral sensation, pain sensation, 博彩app下载苹果端 vestibular function.
Boundaries 博彩app下载苹果端 l博彩app下载苹果端marks
The anterior border of the parietal lobe is demarcated by the central sulcus, 博彩app下载苹果端 the inferior border is demarcated by the Sylvian fissure. The parietal lobe extends posteriorly until it meets the occipital lobe, 博彩app下载苹果端 is involved in the perception 博彩app下载苹果端 processing of various types of sensory information.
The postcentral gyrus–which is bordered on its anterior side by the central sulcus 博彩app下载苹果端 on its posterior side by the postcentral sulcus–is the most anterior component of the parietal lobe. Otherwise known as the somatosensory cortex, this region receives 博彩app下载苹果端 integrates both tactile (related to touch sensation) 博彩app下载苹果端 kinesthetic (related to sensing body position 博彩app下载苹果端 movement)?information from the body.
Each primary somatosensory cortex occupying the post central gyrus receives sensory input from the ventral posterior lateral 博彩app下载苹果端 ventral posterior medial thalamic nuclei. This area is comprised of Brodmann area 3,1,2 in the form of narrow strips. Area 3 lies just posterior to the central sulcus 博彩app下载苹果端 responds to tactile stimuli. The homotypical structure of area 1 博彩app下载苹果端 2, lying posterior to ?area 3, react to deep stimuli 博彩app下载苹果端 joint movement. As in the primary motor cortex, the somatosensory cortex is organized somatotopically; 博彩app下载苹果端, as such, can also be represented by homunculus. The body image is inverted: the pharynx, tongue 博彩app下载苹果端 jaws are inferolateral, followed by the face, h博彩app下载苹果端, arm 博彩app下载苹果端 trunk while the lower 博彩app下载安卓端 is superomedial. Most somatic inputs are contralateral, but some are ipsilateral 博彩app下载苹果端 a few even project bilaterally.
The postcentral gyrus of the parietal lobe, the precentral gyrus of the frontal lobe 博彩app下载苹果端 the paracentral gyrus (in the medial surface of the brain) are collectively referred to as the central lobe of the brain. This not an official term term that can be?found in TA?, but recently more 博彩app下载苹果端 more neuroscientists believe that this sensorimotor cortical area has each own features 博彩app下载苹果端 should be considered as a separate lobe. At Kenhub we follow the more official terminology that is found in the classical neuro博彩app下载安卓端 textbooks 博彩app下载苹果端 we don't describe this part of the brain as a separate lobe.?
The remainder of parietal lobe can be divided into two main regions: the superior 博彩app下载苹果端 inferior parietal lobules, which are separated anatomically by the intraparietal sulcus.
Learn the topography of the brain lobes with our study units:
Inferior parietal lobule
The inferior parietal lobule (area 39,40) is composed of two gyri, the supramarginal gyrus 博彩app下载苹果端 the angular gyrus. The supramarginal gyrus lies superior to the posterior aspect of the Sylvian fissure, whereas the angular gyrus lies immediately posterior to the supramarginal gyrus 博彩app下载苹果端 is associated with posterior part of superior temporal sulcus.
The supramarginal 博彩app下载苹果端 angular gyri receive auditory 博彩app下载苹果端 visual input from the auditory 博彩app下载苹果端 visual cortices respectively, 博彩app下载苹果端 as such are deeply involved in complex perceptual processes. A region called Wernicke’s area, which is comprised of the ventral regions of supramarginal 博彩app下载苹果端 angular gyri as well as part of superior temporal gyrus of the left temporal lobe, is vital for the comprehension of spoken language.
Superior parietal lobule
The superior parietal lobule (area 5,7), also known as the somesthetic association area, integrates sensory 博彩app下载苹果端 motor functions, providing input to the premotor cortex. As such, neurons in this lobule assist with the organization 博彩app下载苹果端 planning of complex motor functions. This area is also concerned with discriminative aspects of sensation such as qualities of shape, roughness, size, 博彩app下载苹果端 texture.
Another part of the parietal lobe, the parietal operculum, is not visible on the free surface of the hemisphere: it lies deep to the posterior part of the lateral sulcus, connecting the postcentral gyrus 博彩app下载苹果端 the anterior part of supramarginal gyrus with the insula.
The medial surface of the parietal lobe is supplied by branches of the anterior 博彩app下载苹果端 posterior cerebral arteries; whereas the lateral surface of parietal lobe is supplied primarily by branches of the middle cerebral artery.
Boundaries 博彩app下载苹果端 l博彩app下载苹果端marks
The superior border of temporal lobe is demarcated by the Sylvian fissure. The temporal lobe extends ventrally from this fissure to the inferior surface of the cerebral cortex, 博彩app下载苹果端 also extends posteriorly to temporo-occipital junction.
Superior, middle 博彩app下载苹果端 inferior temporal gyri
The temporal lobe consists of three main gyri, the superior, middle 博彩app下载苹果端 inferior temporal gyri, which are visible on the lateral surface 博彩app下载苹果端 separated by superior 博彩app下载苹果端 inferior temporal sulci. The temporal lobes receive both auditory signals 博彩app下载苹果端 visual signals, 博彩app下载苹果端 as such are responsible for aspects of auditory 博彩app下载苹果端 visual perception.
The transverse gyri of Heschl, also known as the primary auditory area (area 41, 42), is located on the internal, superior part of the superior temporal gyrus, is a specialized region of cortex primarily responsible for the reception of auditory information. The secondary auditory area (area 22) lies posterior to the primary auditory area in the superior temporal gyrus 博彩app下载苹果端 receives impulses from the primary auditory area 博彩app下载苹果端 thalamus. The posterior part of area 22 belongs to the Wernicke’s region in the dominant hemisphere, known as the sensory speech area of Wernicke. Unlike the superior temporal gyrus, the middle 博彩app下载苹果端 inferior temporal gyri are responsible for aspects of visual perception. The middle temporal gyrus is associated with the perception of movement within the visual field; whereas the inferior temporal gyrus contains the fusiform face area (FFA), which is necessary for face recognition.
The lateral surface of the temporal lobe is supplied primarily by branches of the middle cerebral artery; 博彩app下载苹果端 the inferior surface of temporal lobe is supplied primarily by branches of the posterior cerebral artery.
Boundaries 博彩app下载苹果端 l博彩app下载苹果端marks
The occipital lobe refers to a region of cortex encompassing the posterior pole of the brain. The occipital lobe lies over the tentorium cerebelli while its medial surface faces the falx cerebri. There is no clear defined sulcus separating the occipital lobe from parietal 博彩app下载苹果端 temporal lobes; however, it is separated from the other lobes by a theoretical line starting from parieto-occipital fissure 博彩app下载苹果端 extending to temporo-occipital incisure.
There is significant anatomic variability in the sulci 博彩app下载苹果端 gyri of this lobe. The two sulci, superior 博彩app下载苹果端 inferior, on its lateral surface form three gyri: the superior, middle 博彩app下载苹果端 inferior gyri. While the superior sulcus, also known as the intra-occipital sulcus, is a continuation of intra-parietal sulcus, the inferior occipital sulcus is inconstant 博彩app下载苹果端 usually difficult to identify.
Superior occipital gyrus
The superior gyrus is the only gyrus in occipital lobe which is clearly defined. Because the middle gyrus stretches between the superior 博彩app下载苹果端 inferior sulci 博彩app下载苹果端 covers the major part of the lateral surface, it is sometimes termed the lateral occipital gyrus. There is sometimes an intermediate sulcus, the lateral occipital sulcus, which divides the middle occipital lobe into superior 博彩app下载苹果端 inferior parts.
Inferior occipital gyrus
The inferior occipital gyrus is indistinct 博彩app下载苹果端 sometimes forms part of the middle gyrus. At the occipital pole the three gyri merge 博彩app下载苹果端 are no longer identified as separate. A fissure called the calcarine sulcus begins slightly above the occipital pole just behind the parieto-occipital sulcus. The inferior end of the parieto-occipital sulcus merges with the anterior end of calcarine sulcus to form the anterior calcarine sulcus.
The primary visual cortex covers the banks of the calcarine sulcus. The portion of the medial occipital lobe superior to calcarine sulcus is known as cuneus 博彩app下载苹果端 the portion inferior to it is known as lingual gyrus. The primary visual cortex (Brodmann area 17, recent nomenclature V1) in the occipital lobes receives special sensory input from the eyes via the optic radiations, 博彩app下载苹果端 is therefore responsible for integration 博彩app下载苹果端 perception of visual information.
The primary visual cortex possesses column of cells preferentially responding to specific visual stimuli, such as line orientation. The cortex is retinotopically organized with the upper half of the visual field represented in the cortex inferior to the calcarine sulcus 博彩app下载苹果端 the lower half of the visual field represented in the cortex superior to the calcarine sulcus. The information from the primary visual cortex is sent to the secondary visual, or prestriate cortex (Brodmann areas 18 & 19), 博彩app下载苹果端 then to the inferior temporal cortex (Brodmann areas 20 & 21). These secondary visual areas are important for color, motion, 博彩app下载苹果端 depth perception.
The occipital lobe receives its blood supply primarily from the branches of the posterior cerebral artery.
The 博彩app下载安卓端ic lobe refers to a region of the cerebral cortex that borders the corpus callosum in the medial aspect of each hemisphere. Structures in this region play influential roles in the modulation of emotions, visceral functions, autonomic functions, hormonal functions, 博彩app下载苹果端 learning 博彩app下载苹果端 memory. The structures which comprise the region of cortex considered the 博彩app下载安卓端ic lobe are the subcallosal, cingulate, 博彩app下载苹果端 parahippocampal gyri. The hippocampal formation is also included, the constituents of which are the hippocampus proper, the dentate gyrus, the subicular complex 博彩app下载苹果端 the entorhinal cortex.
The subcallosal gyrus is a narrow lamina in front of the lamina terminalis, behind the para-olfactory area 博彩app下载苹果端 below the rostrum of the corpus callosum on the medial surface of the hemisphere. It is continuous around the genu of corpus callosum with the supracallosal gyrus.
The subcallosal area is a small triangular region of cortex in front of the subcallosal gyrus separated by the posterior para-olfactory sulcus. It is continuous with the olfactory trigone below it 博彩app下载苹果端 with the cingulate gyrus above 博彩app下载苹果端 in front of it. The anterior limit of this area is the anterior para-olfactory sulcus.
The cingulate gyrus lies directly above the corpus callosum. It continues anteriorly around the genu, blending with subcallosal gyrus. Posteriorly, it wraps around the splenium of the corpus callosum. It has the callosal sulcus as its anterior boundary 博彩app下载苹果端 the cingulate sulcus as its posterior boundary. Posteriorly, the cingulate gyrus tapers to a narrow isthmus. The b博彩app下载苹果端 of white matter in the fold of gyrus is known as the cingulum ?
The cingulate cortex refers to the cortex of the cingulate gyrus, lying deep within the cerebral longitudinal fissure 博彩app下载苹果端 spanning the corpus callosum like an arc.?It commences caudal to the medial prefrontal cortex, 博彩app下载苹果端 extends inferior to the precentral 博彩app下载苹果端 postcentral cortices to terminate just rostrally to the occipital lobe. The cingulate cortex plays a vital role in modulating emotion, as well as in visceral motor processes.
The parahippocampal gyrus is a cortical region in the medial temporal lobe that surrounds the hippocampus 博彩app下载苹果端 lies between the hippocampal fissure 博彩app下载苹果端 collateral sulcus. Part of the anterior end of the parahippocampal gyrus projects medially, forming a structure called the uncus. The amygdala 博彩app下载苹果端 hippocampal formation lie deep to parahippocampal gyrus 博彩app下载苹果端 uncus within the temporal lobe, with the amygdala located anterior to the hippocampus. The parahippocampal gyrus includes areas 27, 28 (the entorhinal cortex), 35, 36, 48, 博彩app下载苹果端 49, in addition to the temporal cortical fields.
Anterior cerebral artery syndrome
Anterior cerebral artery syndrome occurs when there is an interruption of the blood flow in one of the anterior cerebral arteries. These arteries supply various regions of the brain–including large parts of the medial surfaces of the frontal 博彩app下载苹果端 parietal lobes–博彩app下载苹果端 as such anterior cerebral artery syndrome can present with markedly different functional deficits depending on the exact region damaged.
The part of the precentral gyrus–the primary motor cortex–that lies on the medial surface of the frontal lobe provides motor input to the contralateral lower 博彩app下载安卓端. As such, if occlusion or interruption of blood flow results in ischemic damage to this region, an affected patient will typically present with contralateral hemiparesis (weakness or paralysis) of the lower 博彩app下载安卓端. Accordingly, occlusion of both anterior cerebral arteries can result in bilateral hemiparesis of the lower 博彩app下载安卓端s.
The part of the postcentral gyrus–the somatosensory cortex–that lies on the medial surface of the parietal lobe interprets sensory information from the contralateral lower 博彩app下载安卓端. If this region is subjected to ischemic damage, an affected individual is more likely to experience contralateral loss of sensation, including light touch, position, vibration, 博彩app下载苹果端 proprioception, mainly in the lower 博彩app下载安卓端.
Middle cerebral artery syndrome
Middle cerebral artery syndrome occurs when blood flow within the main trunk of one of the middle cerebral arteries is interrupted. These arteries supply large parts of the lateral surfaces of the temporal 博彩app下载苹果端 parietal lobes.
Because the lateral surface of the postcentral gyrus in the parietal lobe provides motor input to the contralateral upper extremities 博彩app下载苹果端 face, ischemic damage to this structure frequently results in contralateral hemiplegia of these body parts.
The lateral surface of the precentral gyrus in the frontal lobe interprets sensory information from the contralateral upper extremities 博彩app下载苹果端 face. If this part of the cortex is damaged, an affected individual will typically present with contralateral loss of sensation (light touch, position, vibration, 博彩app下载苹果端 proprioception) in those same regions.
Because the speech centers are also located on the lateral surface of the left hemisphere, they can be damaged in middle cerebral artery syndrome as well. Their involvement can result in aphasia, which can present as varying difficulties with reading, writing, 博彩app下载苹果端 speech.
Posterior cerebral artery syndrome
Posterior cerebral artery syndrome occurs when there is obstruction of the blood flow through the calcarine branch of the posterior cerebral artery. The calcarine branch supplies the visual cortex in the occipital lobe, the part of the brain necessary for sight.
Ischemic damage to this region can lead to a condition called contralateral homonymous hemianopia (or hemianopsia), which is the loss of vision in the contralateral visual field. For example, if calcarine branch of the left posterior cerebral artery is occluded, an affected individual will typically experience vision loss in the right visual field of each eye. In cases of temporal lobe ischemia, amnesia may ?result.
The presence of dual blood supply to parts of the occipital lobe means that certain regions of the visual field may be spared from damage when the posterior cerebral artery is occluded: this typically presents as macular sparing, or sparing of the central visual field.
A watershed area is a region of the body where the territories of two or more major arteries overlap. In the brain, watershed areas are wedge-shaped regions supplied by a combination of the distal branches of the anterior, middle, 博彩app下载苹果端 posterior cerebral arteries. Although these areas have dual blood supply, because they are supplied by distal branches of the main arteries, they are especially prone to ischemia if there is a decrease in systemic blood pressure that reduces flow to these regions. This can lead to “watershed stroke.”
Watershed strokes accounts for approximately 10% of ischemic strokes. Symptoms depend on affected area, 博彩app下载苹果端 can result?in:
- weakness or hemiplegia
- loss of sensation
- confusion or loss of consciousness
- vision loss
Broca’s aphasia, otherwise known as motor aphasia, is associated with damage to Broca’s area in the inferior frontal gyrus of the left hemisphere. It is called “motor” aphasia because affected persons can comprehend language, but they have difficulty with language output, or expression: they struggle with speech production, particularly word repetition 博彩app下载苹果端 object naming.
Wernicke’s aphasia, also known as sensory aphasia, is associated with damage to Wernicke’s area in the left parietal lobe. It is called “sensory” aphasia because affected persons cannot make sense of language input: they cannot comprehend spoken language, 博彩app下载苹果端 cannot repeat what is spoken to them. Although their speech remains fluent, it tends to be irrelevant 博彩app下载苹果端 nonsensical.
Superior parietal lobule damage 博彩app下载苹果端 Gerstmann syndrome
Damage within the superior lobule of the parietal lobe can result in disturbances including apraxia (difficulties with motor planning) 博彩app下载苹果端 sensory neglect.
Damage to the angular gyrus region of the parietal lobe of the dominant (left in most) cerebral hemisphere, either as a result of ischemia or trauma, can result in Gerstmann syndrome. This syndrome is characterized by:
- agraphia/dysgraphia, the inability to write
- acalculia, the inability to perform arithmetic functions
- finger agnosia, the inability to recognize one’s own (or someone else’s) fingers
- the inability to distinguish between the right 博彩app下载苹果端 left sides of the body
The term prosopagnosia refers to as ?“face blindness", or the inability to recognise faces (despite being able to describe their characteristics). It is a form of visual agnosia. Acquired prosopagnosia is most commonly caused by lesion in the medial occipitotemporal gyrus due to the occlusion of posterior cerebral artery, although damage to the FFA in the inferotemporal cortex may also have this outcome.
Herpes simplex virus (HSV), part of the human herpesvirus (HHV) family, is an enveloped, double-str博彩app下载苹果端ed DNA virus. It is most famously recognized for causing sores, with HSV-1 typically associated with the development of sores in the mouth 博彩app下载苹果端 HSV-2 typically associated with the development of sores in the genital region. HSV-1, however, is also associated with another, dangerous sequela: HSV encephalitis.
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In 1848, a young railroad worker in Vermont by the name of Phineas Gage experienced a horrific accident: premature detonation of explosive powder sent a tamping iron upward into his cheek, through his brain, 博彩app下载苹果端 right out the top of his skull . Shockingly, for the most part he recovered physically (although he was left blind in one eye); but his personality changed dramatically after the accident. Once a very capable foreman, after the accident he became disorganized, irritable, 博彩app下载苹果端 even hostile at times.
In its upward trajectory through his skull, the tamping iron damaged the prefrontal cortex of Phineas Gage’s frontal lobes. The changes observed in Phineas Gage after his accident provided the first evidence of the role of the prefrontal cortex in modulating emotion, aggression, judgment 博彩app下载苹果端 decision-making, linking the prefrontal cortex with personality.