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Parietal _ Occipital Lobe.ppt

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Parietal _ Occipital Lobe.ppt

  1. 1. Name of Institution 1 Amity Institute of Psychology & Allied Sciences MA, Clinical Psychology Semester 3 Subject-Basics of Neuropsychology Faculty- Dr. Anganabha Baruah
  2. 2. Name of Institution The Parietal Lobe
  3. 3. Name of Institution Somatosensory Cortex 3
  4. 4. Name of Institution Somatosensory Association 4
  5. 5. Name of Institution Posterior Association Area 5
  6. 6. Name of Institution 6
  7. 7. Name of Institution BOUNDARIES OF PARIETAL LOBE –Anterior border - Central Fissure –Ventral border - Sylvan Fissure –Posterior border - Parieto-occipital sulcus
  8. 8. Name of Institution Subdivisions of the Parietal Lobes
  9. 9. Name of Institution Structures in Parietal Lobe • Postcentral gyrus: This region is the brain's primary somatosensory cortex, and maps sensory information onto what is known as a sensory homonculus. Some researchers also refer to this region as Brodmann area 3. • Posterior parietal (Association) cortex: This region is thought to play a vital role in coordinating movement and spatial reasoning. It also plays a role in attention, particularly attention driven by new stimuli, such as when an animal jumps into the road while you are driving.
  10. 10. Name of Institution • Superior parietal lobule: This region helps you determine your own orientation in space, as well as the orientation of other objects. It also receives significant input from the hand, suggesting that it helps coordinate fine motor skills and sensory input from the hands. • Inferior parietal lobule: Sometimes called Gerschwind's territory, this region aids in assessing facial expressions for emotional content. Some research suggests it plays a role in other functions, including language processing, basic mathematical operations, and even body image. It contains a number of sub-regions, including the angular and supramarginal gyrus.
  11. 11. Name of Institution SUPERIOR PARIETAL LOBULE The superior parietal lobule forms the association cortex of the parietal lobe, and plays an important role in planned movements, spatial reasoning and attention. The intraparietal sulcus can be further divided into a lateral, medial, ventral and anterior area. The lateral area is responsible for our eye movements in response to a stimulus in space. The medial area helps us to determine how far and where we need to reach in relation to our nose. The ventral area is an area that receives a number of sensory modalities; these include auditory, visual, vestibular and somatosensory information. Finally, the anterior area enables us to interpret the size, shape and position of objects we are about to grasp. The anterior and ventral areas work together to enable visual motor coordination
  12. 12. Name of Institution Inferior Parietal Lobule • Most neuroscientists also include regions of the inferior parietal lobule, particularly the supramarginal gyrus (Brodmann area 40) and the angular gyrus (Brodmann area 39) in Wernicke’s area. The supramarginal gyrus forms the auditory area of speech, while the angular gyrus, the visual area of speech. 12
  13. 13. Name of Institution • The Parietal lobes control calculation and language on the dominant side, and the sensory visuospatial processing on the non- dominant hemisphere side. 13
  14. 14. Name of Institution Functions of Parietal Lobes • Distinguishing between two points, even without visual input. • Localizing touch: When you touch any object with any part of your body, your parietal lobe enables you to feel the sensation at the site of the touch and not, say, in your brain or all over your body. • Integrating sensory information from most regions of the body. • Visuospatial navigation and reasoning: When you read a map, follow directions, or prevent yourself from tripping over an unexpected obstacle, your parietal lobe is involved. The parietal lobe is also vital for proprioception—the ability to determine where your body is in space, including in relationship to itself. For instance, touching your finger to your nose without the assistance of a mirror is a function of the parietal lobe.
  15. 15. Name of Institution • Some visual functions, in conjunction with the occipital lobe. • Assessing numerical relationships, including the number of objects you see. • Assessing size, shape, and orientation in space of both visible stimuli and objects you remember encountering. • Mapping the visual world: a number of recent studies suggest that specific regions in the parietal lobe serve as maps to the visual world. • Coordinating hand, arm, and eye motions. • Processing language. • Coordinating attention.
  16. 16. Name of Institution Damage • Difficulty with drawing objects • Difficulty in distinguishing left from right • Spatial disorientation and navigation difficulties • Problems with reading (Alexia) • Inability to locate the words for writing (Agraphia) • Difficulty with doing mathematics (Dyscalculia) • Lack of awareness of certain body parts and/or surrounding space (Neglect) • Inability to focus visual attention • Difficulty with motor planning and complex movements(Apraxia) 16
  17. 17. Name of Institution Anatomy Of Occipital Lobes 17 OCCIPITAL LOBE
  18. 18. Name of Institution • Boundaries Parieto-Occipital Sulcus Preoccipital Notch 18
  19. 19. Name of Institution Primary Visual Cortex 19
  20. 20. Name of Institution Visual Association Cortex 20
  21. 21. Name of Institution The occipital lobe • is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. • The primary visual cortex is Brodmann area 17, commonly called V1 (visual one). • Human V1 is located on the medial side of the occipital lobe within the calcarine sulcus; • the full extent of V1 often continues onto the posterior pole of the occipital lobe. V1 is often also called striate cortex because it can be identified by a large stripe of myelin, the Stria of Gennari.
  22. 22. Name of Institution Extrastriate regions • Visually driven regions outside V1 are called extrastriate cortex. • There are many extrastriate regions, and these are specialized for different visual tasks, such as visuospatial processing, color discrimination, and motion perception.
  23. 23. Name of Institution Primary Visual Cortex (V1) • The primary visual cortex also known as V1, Brodmann area 17, or the striate cortex, is located on either side of the calcarine sulcus on the medial surface of the occipital lobe and extends into both the cuneus and the lingual gyrus. It functions to receive special sensory input from the eyes via the optic radiations, and is, therefore, responsible for integration and perception of visual information. 23
  24. 24. Name of Institution • Visual association cortex • The visual association cortex constitutes the remaining regions of the occipital lobe and is also known as the extrastriate visual cortex. This region functions to interpret visual images.Located within the visual association cortex of the occipital lobe are the second, third and fourth visual areas. 24
  25. 25. Name of Institution • Second visual area • The second visual area, also known as the secondary visual cortex, V2, or the prestriate cortex, occupies much of Brodmann area 18 and in some cases 19. The secondary visual cortex surrounds the primary visual cortex and receives information from it. The information from the primary visual cortex is sent to the secondary visual cortex , before being passed to the third and fourth visual areas to finally reach the inferior temporal cortex. The secondary visual area is important for color, motion, and depth perception. 25
  26. 26. Name of Institution • Third visual area • The third visual area, or V3, lies adjacent to the anterior aspect of V2 and is also located within Brodmann area 18. This visual area communicates directly with the secondary visual cortex and is functionally important in the visual processing of motion. • Fourth visual area • Visual area four, V4, is located anterior to V3 within Brodmann area 19. It communicates and receives information from the secondary visual cortex. The function of visual area four is to interpret colors, orientation, form and movement. 26
  27. 27. Name of Institution Connections of the Visual Cortex Connections -Primary Visual Cortex (V1) -Input from LGN -Output to all other levels -Secondary Visual Cortex (V2) Output to all other levels -After V2 •Output to the parietal lobe - Dorsal Stream •Output to the inferior temporal lobe - Ventral Stream •Output to the superior temporal sulcus (STS) - STS Stream • DorsalStream – Visual Guidance of Movements • Ventral Stream – Object Perception • STS – Visuospatial functions (bio movement
  28. 28. Name of Institution Functions • A significant functional aspect of the occipital lobe is that it contains the primary visual cortex. • Retinal sensors convey stimuli through the optic tracts to the lateral geniculate bodies, where optic radiations continue to the visual cortex. • Each visual cortex receives raw sensory information from the outside half of the retina on the same side of the head and from the inside half of the retina on the other side of the head.
  29. 29. Name of Institution Function V1 - function like mailboxes: segregating info to other areas., receives primary visual impressions Color/Form/Motion/Size and illumination. V2, V3, V3A, V4, V5- Visual association areas- Recognition and identification of objects, storage of visual memories, it functions in more complex visual recognition and perception, revisualization, visual association and spatial orientation.
  30. 30. Name of Institution •Contour analysis and binocular vision are two functions of the visual cortex, and such processing is a function of both its horizontal and its vertical organization. •The cells within the striate cortex are activated only by input from the LGN, although other cortical areas have input into the striate cortex. •The striate cortex communicates with the superior colliculus and the frontal eye fields.
  31. 31. Name of Institution Clinical Effects of Occipital Lobe Lesions • Visual Field Defects • Cortical blindness • Visual Anosognosia • Visual Illusions • Visual hallucinations • Visual Agnosias
  32. 32. Name of Institution Visual field defects • The most familiar clinical abnormality resulting from a lesion of one occipital lobe, is a contralateral homonymous hemianopia,. • Extensive destruction abolishes all vision in the corresponding half of each visual field. • With a neoplastic lesion that eventually involves the entire striate region, the field defect may extend from the periphery toward the center, and loss of color vision (hemiachromatopsia) often precedes loss of black and white. • Destruction of only part of the striate cortex on one side yields characteristic field defects that accurately indicate the loci of the lesion.
  33. 33. Name of Institution Cortical Blindness • With bilateral lesions of the occipital lobes (destruction of area 17 of both hemispheres), there is a loss of sight that can be conceptualized as bilateral hemianopia. • The degree of blindness may be equivalent to that which follows severing of the optic nerves. • The pupillary light reflexes are preserved because they depend upon visual fibers that terminate in the midbrain, but reflex closure of the eyelids to threat or bright light may be preserved
  34. 34. Name of Institution • No changes are detectable in the retinas. • The eyes are still able to move through a full range and, if there is macular sparing as there usually is with vascular lesions, optokinetic nystagmus can be elicited • Visual imagination and visual imagery in dreams are preserved. • With rare exceptions, no cortical potentials can be evoked in the occipital lobes by light flashes or pattern changes (visual evoked response), and the alpha rhythm is lost in the electroencephalogram
  35. 35. Name of Institution The usual cause of cortical blindness • is occlusion of the posterior cerebral arteries (most often embolic) or the equivalent, occlusion of the distal basilar artery. • Macular sparing may leave the patient with an island of barely serviceable central vision. • The infarct may also involve the mediotemporal regions or thalami, which share the posterior cerebral artery supply, with a resulting Korsakoff amnesic defect and a variety of other neurologic deficits referable to the high midbrain and diencephalon (drowsiness, akinetic mutism etc… )
  36. 36. Name of Institution Visual Anosognosia (Anton Syndrome ) • The main characteristic of this disorder is the denial of blindness by a patient who obviously cannot see. • The patient acts as though he could see, and in attempting to walk, collides with objects, even to the point of injury. • The lesions in cases of negation of blindness extend beyond the striate cortex to involve the visual association areas.
  37. 37. Name of Institution Visual Illusions (Metamorphopsias) • These may present as distortions of form, size, movement, or color like deformation of the image, change in size, illusion of movement, or a combination of all three. • Illusions of these types have been reported with lesions confined to the occipital lobes but are more frequently caused by shared occipitoparietal or occipitotemporal lesions; • The right hemisphere appears to be involved more often than the left.
  38. 38. Name of Institution Visual Hallucinations • These phenomena may be elementary or complex, and both types have sensory as well as cognitive aspects. • Elementary (or unformed) hallucinations include flashes of light, colors, luminous points, stars, multiple lights (like candles), and geometric forms (circles, squares, and hexagons). • They may be stationary or moving (zigzag, oscillations, vibrations, or pulsations). •Complex hallucinations include objects, persons, or animals and infrequently, more complete scenes that are indicative of lesions in the visual association areas or their connections with the temporal lobes.
  39. 39. Name of Institution Color vision defects • Two types of color vision deficit are associated with occipital lesions. • First, a complete loss of color vision, or achromatopsia, may occur either ipsilaterally or in one visual hemifield with lesions that involve portions of the visual association cortex (Brodmann areas 18 and 19). • Second, patients with pure alexia and lesions of the left occipital lobe fail to name colors, although their color matching and other aspects of color perception are normal.
  40. 40. Name of Institution • Patients often confabulate an incorrect color name when asked what color an object is. • This deficit can be called color agnosia, in the sense that a normally perceived color cannot be properly recognized. • Although this deficit has been termed color anomia, these patients can usually name the colors of familiar objects such as a school bus or the inside of a watermelon.
  41. 41. Name of Institution Visual Object Agnosia • Visual object agnosia is the quintessential visual agnosia: the patient fails to recognize objects by sight, with preserved ability to recognize them through touch or hearing in the absence of impaired primary visual perception or dementia • In 1890, Lissauer distinguished two subtypes of visual object agnosia: apperceptive visual object agnosia, referring to the synthesis of elementary perceptual elements into a unified image, and associative visual object agnosia, in which the meaning of a perceived stimulus is appreciated by recall of previous visual experiences.
  42. 42. Name of Institution Apperceptive Visual Agnosia • The first type, apperceptive visual agnosia, is difficult to separate from impaired perception or partial cortical blindness. • Any failure of object recognition in which relatively basic visual functions (acuity, color, motion) are preserved is apperceptive. • Patients with apperceptive visual agnosia can pick out features of an object correctly (e.g., lines, angles, colors, movement), but they fail to appreciate the whole object • Warrington and Rudge (1995) pointed to the right parietoccipital cortex for its importance in visual processing of objects, and they found this area critical to apperceptive visual agnosia.
  43. 43. Name of Institution •Apperceptive visual agnosia related to bilateral occipital lesions a “pseudoagnosic syndrome” associated with visual processing defects, as compared to true visual agnosias, in which the right parietal cortex is deficient in identifying and recognizing visual objects. •Recent evidence of the functions of specific cortical areas has included the specialization of the medial occipital cortex for appreciation of color and texture,whereas the lateral occipital cortex is more involved with shape perception. •Deficits in these specific visual functions can be seen in patients with visual object agnosia
  44. 44. Name of Institution • apperceptive visual agnosia usually occurs in patients with bilateral occipital lesions. • It may represent a stage in recovery from complete cortical blindness. • Deficits in recognition of visual objects may be especially apparent with recognition of degraded images, such as drawings rather than actual objects. • Apperceptive visual agnosia can also be part of dementing syndromes
  45. 45. Name of Institution Associative visual agnosia • It is defect in the association of the object with past experience and memory . The inability to recognize an object despite an apparent perception of the object is associative agnosia. • Some patients can copy or match drawings of objects they cannot name, thus excluding a primary defect of visual perception. • Aphasia is excluded because the patient can identify the same object presented in the tactile or auditory modality • occurs with bilateral occopitotemoral junction lessions.
  46. 46. Name of Institution prosopagnosia • Patients with facial agnosia cannot recognize any previously known faces, including their own as seen in a mirror or photograph. • First, patients who cannot match pictures of faces must have defective face processing,or apperceptive prosopagnosia, whereas those who can match faces but simply fail to recognize familiar examples(either friends and relatives or famous personages) have associative prosopagnosia
  47. 47. Name of Institution Benton Face Recognition • History: “facial agnosia”/ prosopagnosia • Purpose: Measures visualoperceptual discrimination of unfamiliar faces (not recognition/memory) • Associated with right hemisphere: parietal, occipitoparietal and occipitotemporal • 3 parts: – Match identical front view – Match front view with ¾ view – Match front view with various lighting conditions
  48. 48. Name of Institution In clinical studies • prosopagnosia may occur either as an isolated deficit or as part of a more general visual agnosia for objects and colors. Faces are likely the most complex and individualized visual displays to recognize, but some patients with visual object agnosia can recognize faces, suggesting that there may be a specific brain area devoted to facial recognition.
  49. 49. Name of Institution Optic Aphasia • The syndrome of optic aphasia, or optic anomia, is intermediate • between agnosias and aphasias. • The patient with optic aphasia cannot name objects presented visually but can demonstrate recognition of the objects by pantomiming or describing their use. • The preserved recognition of the objects distinguishes optic aphasia from associative visual agnosia. • Like visual agnosics, patients with optic aphasia can name objects presented in the auditory or tactile modalities, distinguishingthem from anomic aphasics.
  50. 50. Name of Institution In optic aphasia • information about the object must reach parts of the cortex involved in recognition, perhaps in the right hemisphere, but the information is not available to the language cortex for naming. • Patients with optic aphasia may confabulate incorrect names when asked to name an object they clearly recognize,just as the patient with color agnosia confabulates incorrect color names.
  51. 51. Name of Institution Visuospatial Agnosia •Among this variety of disorders of spatial perception and orientation, one disruptive form is topographical disorientation—the inability to find one’s way around familiar environments such as one’s neighborhood. •People with this deficit seem unable to recognize landmarks that would indicate the appropriate direction in which to travel •Most people with topographical disorientation have other visual deficits, especially defects in facial recognition. • Critical area for this disorder lies in the right medial occipitotemporal region, including the fusiform and lingual gyri.
  52. 52. Name of Institution Epilepsy and occipital lobes • Occipital lobe seizures are triggered by a flash, or a visual image that contains multiple colors. These are called flicker stimulation (usually through TV) these seizures are referred to as photo-sensitivity seizures. Patients having experienced occipital seizures described their seizure as seeing bright colors, and having severe blurred vision (vomiting was also apparent in some patients).
  53. 53. Name of Institution Occipital seizures • are triggered mainly during the day, through television, video games or any flicker stimulatory system. • Occipital seizures originate from an epileptic focus confined within the occipital lobes. They may be spontaneous or triggered by external visual stimuli. Occipital lobe epilepsies are etiologically idiopathic, symptomatic, or cryptogenic. • Symptomatic occipital seizures can start at any age, as well as any stage after or during the course of the underlying causative disorder. • Idiopathic occipital epilepsy usually starts in childhood. • Occipital epilepsies account for approximately 5% to 10% of all epilepsies.
  55. 55. Name of Institution • Receptive aphasia • Wernicke’s area (Brodmann area 22) lies in the superior temporal gyrus and overlaps the parieto-temporal junction. This region is responsible for our understanding of speech. Damage to this region will result in a receptive aphasia, which is a fluent form of aphasia. The patient will present with ‘word salad’ i.e. they will be able to form words, but the words will not be in any comprehensible order or syntax. The homologous area of the right cortex, is responsible for our interpretation of body language, and making sense of ambiguous words. Damage to Wernicke’s area may not always result in a receptive aphasia. If the surrounding cortex is intact, and the right corresponding area is intact, there symptoms may be minimal. 55
  56. 56. Name of Institution • Bálint’s syndrome • This syndrome is usually associated with large bilateral lesions, resulting in deficits in visual attention, as well as motor function. Symptoms include: • simultanagnosia (the patient isn’t able to interpret to see the whole visual field) • optic ataxia (the patient isn’t able to move their hands in relation to their visual input) • optic apraxia (an inability to fixate the eyes). • As Bálint’s syndrome is a rare disease. Sudden severe hypotension, which impacts the watershed areas between the parietal and occipital lobes, is most common cause of the bilateral ischaemia. Due to the range of symptoms and manifestations, the condition is often mistaken for blindness related to other disorders. 56
  57. 57. Name of Institution • Parietal lobe stroke • Ischaemic strokes are commonly the result of atheroschlerotic emboli. The middle cerebral artery is the largest branch of the internal carotid artery, and a direct continuation of the artery. It is therefore the commonest location of ischaemic strokes. The middle cerebral artery supplies the lateral surface of the parietal lobe (as well as the superior temporal lobe), which is the location of the upper limb and face on the primary somatosensory cortex. Therefore, strokes impacting the middle cerebral artery result in sensory loss of these areas, with sparing of the lower limbs. Motor function of the same areas may also result, as the primary motor cortex is just anterior to the primary somatosensory cortex, and is also supplied in part by the middle cerebral artery. 57
  58. 58. Name of Institution • Hemi spatial neglect is a phenomenon that usually follows damage to the non-dominant parietal lobes (usually the right), usually following a stroke. The patient is still able to see both sides of their visual fields in both eyes, but is not able to interpret the sensory information sent to the brain from one half of the visual field. If a stroke occurs in the right parietal lobe, the patient will ignore the left visual field. If a stroke occurs in the left parietal lobe, the ability of the patient to solve mathematical problems, as well as reading and writing would be impaired. • The symptom of optic ataxia results in issues with the patient reaching for objects in the contralateral visual field to the affected parietal lobe. Amorphosynthesis is a condition where the patient is unaware of somatic sensations from one side of the body, and is a possible result of parietal lobe stroke. 58
  59. 59. Name of Institution • If the left lobe is affected, agnosia (a loss of general perception) results. A lesion of the right parietal lobe causes issues with the person’s interpretation of the left side of their visual field, as well as their personal space. • Apraxia is a disorder of motor control, that usually results from damage to the left parietal lobe. • Damage to Baum’s loop results in a contralateral lower quadrantanopia, or a ‘pie in the floor’ visual deficit. A lesion of Meyer’s loop results in a contralateral upper quadrantanopia, or ‘pie in the sky’ visual deficit. 59
  60. 60. Name of Institution • Gerstmann’s syndrome • This syndrome is related to damage to the inferior parietal lobule in the dominant hemisphere of the brain (usually the left), and is associated with right-left confusion and presents characteristic symptoms, including: • agraphia (difficulty in writing) • acalculia (difficulty with math) • aphasia (language disorders) • agnosia (difficulty to perceive objects • These symptoms vary in severity between patients. When the supramarginal and/or angular gyri (parts of the inferior parietal lobule) are impacted, the patient’s ability to interpret written or oral language may be impacted. 60
  61. 61. Name of Institution Tests for calculations Components – Rote tables (add, multiply, etc) Recognition of signs (+ , - , * ) Basic arithmetic(carrying, borrowing) Spatial alignment of written calculations • Verbal rote examples : what is 4 plus 6 ? • Verbal complex examples : what is 21 * 5 ?
  62. 62. Name of Institution Tests for right – left confusion  Identification on self ex : show your left foot.  Crossed commands on self ex : with your right hand touch your left ear  Identification on examiner ex : point my right elbow  Crossed commands on examiner ex : with your left hand point my right foot.
  63. 63. Name of Institution Tests for finger agnosia • Inability to name , point or recognize fingers on oneself or others. 1.Non verbal finger recognition : with pt eyes closed, touch one of his fingers. Ask him to touch the same finger of examiner, with eyes open. 2.Identifying named fingers on examiner’s hand : examiner places hand in some irregular position and asks pt – “ point to my middle finger”
  64. 64. Name of Institution IDEOMOTOR APRAXIA (“how to do”) •Most common type of apraxia i.Buccofacial apraxia ( blowing a match ) ii.Limb apraxia ( flip a coin , comb hair ) iii.Whole body apraxia ( stand like boxer ) •Commands to be alternated b/w right and left limbs
  65. 65. Name of Institution IDEATIONAL APRAXIA(“what to do”) • Disturbance of complex motor planning of a higher order . • Pt able to do individual tasks, but cannot integrate them as a whole. • ‘Conceptual apraxia’ – there is apparent inability to recognise the use of objects (object agnosia). ex: pt attempts to light a candle by striking it on matchbox
  66. 66. Name of Institution Praxis testing (done in an order) 1. Observe the actions – shaving ,dressing,eating. 2. Carry out familiar acts – blow a kiss, wave gudbye. 3. Imitate the examiner (‘do this after me’) 4. How to use objects (pantomime) simple acts – hammer nail, comb hair . complex acts – light and smoke cigar; open soda bottle, pour in glass and drink. 5. Demonstrate use of actual items (both limbs and orofacial commands to be asked)
  67. 67. Name of Institution Drawings to command : 1. draw a clock with 10:20 time 2. draw a 2D figure - daisy in a pot 3. draw a house – in way you can see two sides and the roof. Block designs  Lt. sided lesions – simplification of complex diagrams  Rt. sided lesions – rotation of diagrams .
  68. 68. Name of Institution DRESSING APRAXIA •Not a true apraxia. •Combination of spatial disorientation and visuospatial inattention.
  69. 69. Name of Institution Tests for visual disorders • Visual field testing • Visual neglect : - casual observation of pt’s behaviour. - drawings made by the pt.
  70. 70. Name of Institution Tests for geographic disorientation • Geographic orientation is function of parietal lobe and its multimodal association area. • Combination of processes – spatial orientation, right-left orientation ,visual perception and its memory. 1.History from relatives : Does he become lost in work? Does he have difficulty in orienting to new environment?
  71. 71. Name of Institution 2. Localizing places in maps : Adequate literacy level and historical knowledge is necessary. ex : to locate cities or states on maps. 3. Ability to orient self in hospital : By observing the pt’s capacity to find their bed, ward and bathroom.

Editor's Notes

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