Integrative agnosia

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Integrative agnosia
Cerebrum - occipital lobe - animation.gif
The highlighted region of the brain indicates the extrastriate cortex, which, when damaged, may lead to integrative agnosia.

Integrative agnosia is a sub-disease of agnosia, meaning the lack of integrating perceptual wholes within knowledge. Integrative agnosia can be assessed by several experimental tests such as the Efron shape test, which determines the specificity of the disease being Integrative. This disease is often caused by brain trauma, producing medial ventral lesions to the extrastriate cortex. [1] Affecting this region of the brain produces learning impairments: the inability to integrate parts such as spatial distances or producing visual images from short or long-term memory. [2]

Contents

Symptoms and signs

Symptoms generally include memory or learning impairments, with the inability to integrate parts coherently. There is a big range to the severity of this disease and often the symptoms that are shown in each patient vary as well. As ambiguous as the general symptoms may be, patients are often treated of their respective symptoms as they appear and how critical the conditions are. [2]

Causes

Some of the causes of integrative agnosia include stroke, traumatic brain injury, Alzheimer's disease, an anoxic episode following myocardial infarction, and progressive multifocal leukoencephalopathy. [1]

Diagnosis

Cases with integrative agnosia appear to have medial ventral lesions in the extrastriate cortex. Those who have integrative agnosia are better able to identify inanimate than animate items, which indicates processes that lead to accurate perceptual organization of visual information can be impaired. This is attributed to the importance of perceptual updating of stored visual knowledge, which is particularly important for classes of stimuli that have many perceptual neighbors and/or stimuli for which perceptual features are central to their stored representations. Patients also show a tendency to process visual stimuli initially at a global rather than local level. [1] Although the grouping of local elements into perceptual wholes can be impaired, patients can remain sensitive to holistic visual representations. [2]

When determining whether a patient has form agnosia or integrative agnosia, an Efron shape test can be performed. A poor score on the Efron shape test will indicate form agnosia, as opposed to integrative agnosia. A good score on the Efron shape test, but a poor score on a figure-ground segmentation test and an overlapping figures test will indicate integrative agnosia. A patient with integrative agnosia will find it hard to group and segment shapes, especially if there are overlapping animate items or they can over segment objects with high internal detail. However, the patient should have and understand basic coding of shape. [1]

Treatment

One treatment thought to be effective is the repeated exposure to a particular face or object, where impaired perception may be reorganized in memory, leading to improvement on tests of imagery relative to tests of perception. The key factor for this type of treatment to be successful is a regular and consistent exposure, which will lead to improvements in the long run. Results may not be seen right away, but are eventually possible. [2]

Research

Case study 1

A case study on a patient named H.J.A. is discussed and analyzed by M. Jane Riddoch and Glyn W Humphreys. Because this case study is done specifically on the symptoms of one person diagnosed with integrative agnosia, generalizations cannot be made directly from the results and conclusions about the disease as a whole about those who are also diagnosed with this disease. [3]

Like many people who are diagnosed with integrative agnosia, H.J.A. was diagnosed with this disease after suffering a stroke during a surgical procedure in an operating room. The patient underwent several experiments to verify the specific type of agnosia. H.J.A. showed top half visual deficits of the entire visual field in both right and left eyes. Lower visual fields showed normal patterns to the stimulus. [3]

Through the first experiment, the patient showed that tactile presentation of an object helped H.J.A. significantly in identifying an object. When the object was presented only visually, the patient struggled and showed difficulty. Objects used were common everyday objects. The patient always used descriptive terminology to identify an object instead of a single word or term. However, H.J.A. showed an ability to copy objects and match two objects, both pictures and physical objects. [3]

The second experiment showed that H.J.A. was able to identify figures better when presented the silhouette. Other patients with integrative agnosia also tend to show this symptom. The patient lacks local information of the figures to support the global information, which explains the lack of confidence in naming the object. H.J.A. also shows trouble discriminating figures that are significant and others that are meaningless stimuli. This, in turn, can explain why the patient cannot distinguish overlapping figures. [3]

The third experiment showed that the patient was able to give important information about an object, even though, previously, could not identify the object visually. The memory of the patient is intact despite visual deficits. In the fourth and final section of experiments, the patient shows a lack of visual color knowledge, but structures of a given specific object is not impaired, as H.J.A. uses the technique of drawing from memories. This shows that the patient's visual perceptions and memories containing prior knowledge are not altered by integrative agnosia following the stroke. [3]

Case study 2

In a second case study also performed by the M. Jane Riddoch and Glyn W. Humphreys, H.J.A was the subject in this case study to determine the effects integrative agnosia has on visual and spatial short-term memory.

In the first group of experiments, Riddoch and Humphreys tested the patient's visual, spatial, and perceptual capabilities. They first asked him draw his bedroom using his visual capabilities, comparing it to his drawing from memory, rather than visual, at a specific date. They repeated this test again one year later. His results showed that patients with integrative agnosia have problems in accurately recalling spatial information from long-term memory. In addition, H.J.A was asked to assess spatial locations of cities he was familiar with before his stroke. The evidence of his inability to assess the spatial distances supported the correct diagnosis of integrative agnosia. [2]

When H.J.A was asked to compare images of human faces, he was able to point out specific facial features. However, when asked to make side-by-side comparisons of several celebrities' faces, he was unable to make the same comparisons a person without Integrative Agnosia are able to by integrating features into a perceptual representation. On the other hand, the patient did well when asked to determine the angle degrees of the hands of a clock. But because the patient had to simply make a global judgment based on the hands of the clock, there were not any judgments made based on the perception of local parts, such as the comparison of features of a face for example. [2]

In the second group of experiments, the patient, H.J.A, was tested on his ability to manipulate images, assess information using his spatial memory, and complete pattern tasks.
The patient performed a series of tasks such as the Moscovitch Letter Manipulation Task, the Brooks Matrix Task, and a Compass Directions Task. The patient proved able to receive the spatial material well with short-term memory when manipulating materials without a reference frame. The patient was still able to make global processes, identify shapes, single lines, and letters, but lacked the ability to process configurations in perceptual representations, in the respective tasks. When visually holding an image for 10 seconds, the patient was able to process a spatial pattern and transfer that image onto paper accurately. The tasks that H.J.A were given showed where the parts specifically failed to integrate: the patent's perception on spatial elements without a point of reference. With a reference point, H.J.A is able to integrate the parts. [2]

In the last set of experiments, H.J.A is being tested on his ability to reproduce a visual stimuli and reproduce possible and impossible figures. Evidence suggested that the patient had an ability again maintain the global information in order to draw items, and reiterated his difficulty in maintaining local elements and spatial relations. The last experiment (Experiment 11) was the most difficult for H.J.A visually. He was significantly impaired in drawing the impossible figures provided and spent a significant amount of time more than the control, the elderly population, used in this experiment, processing the information to be able to transform them onto paper. The patient demonstrated a lack of representation of all local parts when reproducing the image. [2]

It was concluded that the tasks performed well by H.J.A included the tasks involving ranges of imagery-based tasks, accurately make judgments about global representations such as the angles of a clock, maintained visual patterns over inter-stimulus intervals, mentally rotating letters, manipulating two elements of an image. In contrast, impairment was gauged to be the lack of the ability in recalling spatial layouts, judging spatial directions, judging relative positions of objects, The Brooks Matrix Test, Compass Direction Task, reproducing abstract patterns, and reproducing both possible and impossible figures. Due to the impairment, it was identified that the patient did not have intact imagery and visual short-term memory, made apparent by the spatial relations test. Due to Integrative Agnosia, the patients take information from a top-down manner, using stored knowledge to retrieve an objects perceptual properties. It is much more difficult for patients to use a bottom-up method, or perceiving through a visual stimulus, because of the inability to accurately code the patterns in the visual short-term memory. [2]

Related Research Articles

Agnosia Medical condition

Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.

Astereognosis is the inability to identify an object by active touch of the hands without other sensory input, such as visual or sensory information. An individual with astereognosis is unable to identify objects by handling them, despite intact elementary tactile, proprioceptive, and thermal sensation. With the absence of vision, an individual with astereognosis is unable to identify what is placed in their hand based on cues such as texture, size, spatial properties, and temperature. As opposed to agnosia, when the object is observed visually, one should be able to successfully identify the object.

Visual memory Ability to process visual and spatial information

Visual memory describes the relationship between perceptual processing and the encoding, storage and retrieval of the resulting neural representations. Visual memory occurs over a broad time range spanning from eye movements to years in order to visually navigate to a previously visited location. Visual memory is a form of memory which preserves some characteristics of our senses pertaining to visual experience. We are able to place in memory visual information which resembles objects, places, animals or people in a mental image. The experience of visual memory is also referred to as the mind's eye through which we can retrieve from our memory a mental image of original objects, places, animals or people. Visual memory is one of several cognitive systems, which are all interconnected parts that combine to form the human memory. Types of palinopsia, the persistence or recurrence of a visual image after the stimulus has been removed, is a dysfunction of visual memory.

Simultanagnosia is a rare neurological disorder characterized by the inability of an individual to perceive more than a single object at a time. This type of visual attention problem is one of three major components of Bálint's syndrome, an uncommon and incompletely understood variety of severe neuropsychological impairments involving space representation. The term "simultanagnosia" was first coined in 1924 by Wolpert to describe a condition where the affected individual could see individual details of a complex scene but failed to grasp the overall meaning of the image.

Inattentional blindness or perceptual blindness occurs when an individual fails to perceive an unexpected stimulus in plain sight, purely as a result of a lack of attention rather than any vision defects or deficits. When it becomes impossible to attend to all the stimuli in a given situation, a temporary “blindness” effect can occur, as individuals fail to see unexpected but often salient objects or stimuli.

Associative visual agnosia Medical condition

Associative visual agnosia is a form of visual agnosia. It is an impairment in recognition or assigning meaning to a stimulus that is accurately perceived and not associated with a generalized deficit in intelligence, memory, language or attention. The disorder appears to be very uncommon in a "pure" or uncomplicated form and is usually accompanied by other complex neuropsychological problems due to the nature of the etiology. Afflicted individuals can accurately distinguish the object, as demonstrated by the ability to draw a picture of it or categorize accurately, yet they are unable to identify the object, its features or its functions.

Visual extinction

Visual extinction is a neurological disorder which occurs following damage to the parietal lobe of the brain. It is similar to, but distinct from, hemispatial neglect. Visual extinction has the characteristic symptom of difficulty to perceive contralesional stimuli when presented simultaneously with an ipsilesional stimulus, but the ability to correctly identify them when not presented simultaneously. Under simultaneous presentation, the contralesional stimulus is apparently ignored by the patient, or extinguished. This deficiency may lead to difficulty on behalf of the patient with processing the stimuli’s 3D position.

Visual agnosia is an impairment in recognition of visually presented objects. It is not due to a deficit in vision, language, memory, or intellect. While cortical blindness results from lesions to primary visual cortex, visual agnosia is often due to damage to more anterior cortex such as the posterior occipital and/or temporal lobe(s) in the brain.[2] There are two types of visual agnosia: apperceptive agnosia and associative agnosia.

Autotopagnosia from the Greek a and gnosis, meaning "without knowledge", topos meaning "place", and auto meaning "oneself", autotopagnosia virtually translates to the "lack of knowledge about one's own space," and is clinically described as such.

Apperceptive agnosia is a failure in recognition that is due to a failure of perception. In contrast, associative agnosia is a type of agnosia where perception occurs but recognition still does not occur. When referring to apperceptive agnosia, visual and object agnosia are most commonly discussed; this occurs because apperceptive agnosia is most likely to present visual impairments. However, in addition to visual apperceptive agnosia there are also cases of apperceptive agnosia in other sensory areas.

Elizabeth Kerr Warrington FRS is a British neuropsychologist specialised in the study of dementia. She holds a PhD in Psychology visual processing and is now an emeritus professor of clinical neuropsychology at the University College London. She formerly worked as the Head of the Department of Neuropsychology at the National Hospital for Neurology and Neurosurgery where she is also a member of the Dementia Research Centre. She was made a Fellow of the Royal Society in 1986.

Prosopamnesia

Prosopamnesia is a selective neurological impairment in the ability to learn new faces. There is a special neural circuit for the processing of faces as opposed to other non-face objects. Prosopamnesia is a deficit in the part of this circuit responsible for encoding perceptions as memories.

The Gollin figures test is a psychological test used to assess someone's visual perception. Subjects are shown pictures of common objects: namely five consecutive incomplete line drawings for each picture, from least to most complete, that the subjects need to mentally complete to identify the object drawn. On a retention test sometime later, however, subjects identify the image sooner than they did on the first test, indicating some form of memory for the image. Amnesiac subjects also show improvement on this test, even though they do not recall taking the test before.

Visual object recognition refers to the ability to identify the objects in view based on visual input. One important signature of visual object recognition is "object invariance", or the ability to identify objects across changes in the detailed context in which objects are viewed, including changes in illumination, object pose, and background context.

Amorphosynthesis, also called a hemi-sensory deficit, is a neuropsychological condition in which a patient experiences unilateral inattention to sensory input. This phenomenon is frequently associated with damage to the right cerebral hemisphere resulting in severe sensory deficits that are observed on the contralesional (left) side of the body. A right-sided deficit is less commonly observed and the effects are reported to be temporary and minor. Evidence suggests that the right cerebral hemisphere has a dominant role in attention and awareness to somatic sensations through ipsilateral and contralateral stimulation. In contrast, the left cerebral hemisphere is activated only by contralateral stimuli. Thus, the left and right cerebral hemispheres exhibit redundant processing to the right-side of the body and a lesion to the left cerebral hemisphere can be compensated by the ipsiversive processes of the right cerebral hemisphere. For this reason, right-sided amorphosynthesis is less often observed and is generally associated with bilateral lesions.

Constructional apraxia is characterized by an inability or difficulty to build, assemble, or draw objects. Apraxia is a neurological disorder in which people are unable to perform tasks or movements even though they understand the task, are willing to complete it, and have the physical ability to perform the movements. Constructional apraxia may be caused by lesions in the parietal lobe following stroke or it may serve as an indicator for Alzheimer's disease.

Topographical disorientation is the inability to orient oneself in one's surroundings, sometimes as a result of focal brain damage. This disability may result from the inability to make use of selective spatial information or to orient by means of specific cognitive strategies such as the ability to form a mental representation of the environment, also known as a cognitive map. It may be part of a syndrome known as visuospatial dysgnosia.

Form perception is the recognition of visual elements of objects, specifically those to do with shapes, patterns and previously identified important characteristics. An object is perceived by the retina as a two-dimensional image,[1] but the image can vary for the same object in terms of the context with which it is viewed, the apparent size of the object, the angle from which it is viewed, how illuminated it is, as well as where it resides in the field of vision.[2] Despite the fact that each instance of observing an object leads to a unique retinal response pattern, the visual processing in the brain is capable of recognizing these experiences as analogous, allowing invariant object recognition. recognition|object recognition]]. Visual processing occurs in a hierarchy with the lowest levels recognizing lines and contours, and slightly higher levels performing tasks such as completing boundaries and recognizing contour combinations. The highest levels integrate the perceived information to recognize an entire object. Essentially object recognition is the ability to assign labels to objects in order to categorize and identify them, thus distinguishing one object from another. During visual processing information is not created, but rather reformatted in a way that draws out the most detailed information of the stimulus.

Visuospatial dysgnosia is a loss of the sense of "whereness" in the relation of oneself to one's environment and in the relation of objects to each other. Visuospatial dysgnosia is often linked with topographical disorientation.

Visual selective attention is a brain function that controls the processing of retinal input based on whether it is relevant or important. It selects particular representations to enter perceptual awareness and therefore guide behaviour. Through this process, less relevant information is suppressed.

References

  1. 1 2 3 4 Riddoch, M.; Humphreys, G. W.; Akhtar, N; Allen, H; Bracewell, R.; Schofield, A. J. (2008). "A tale of two agnosias: Distinctions between form and integrative agnosia". Cognitive Neuropsychology. 25 (1): 56–92. doi:10.1080/02643290701848901. PMID   18340604.
  2. 1 2 3 4 5 6 7 8 9 Riddoch, M. Jane; Glyn W. Humphreys; William Blott; and Esther Hardy; Alistair D. Smith (Oct 2003). "Visual and Spatial Short-term Memory in Integrative Agnosia". Cognitive Neuropsychology. 20 (7): 641–671. doi:10.1080/02643290342000078. PMID   20957588.
  3. 1 2 3 4 5 Riddoch, M.; Humphreys, G. W. (1987). "A case of integrative visual agnosia". Brain. 110 (6): 1431–62. doi:10.1093/brain/110.6.1431. PMID   3427396.
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