Magnetic Resonance Imaging
Memories are made of this: the effects of time on stored visual knowledge in a case of visual agnosia. (1/133)We report the effects of the passage of time on the longterm visual knowledge for objects in a patient with visual agnosia (H.J.A.). The naming of real objects was found to have improved, although this was not associated with any change in H.J.A.'s basic perceptual abilities which were stable over a 16-year period. The improvement in object naming was attributed to better use of non-contour-based visual information (such as surface detail and depth cues). In addition, we demonstrate a deterioration in H.J.A.'s long-term memory for the visual properties of objects, and argue that this has occurred as a result of his having impaired perceptual input. The deterioration was only apparent in drawing from memory and in the verbal descriptions of items; with forced-choice testing, H.J.A. operated at ceiling; we propose that current tests of visual imagery may not be sufficiently sensitive to detect subtle impairments of visual memory. Our findings can be taken to indicate that perceptual and memorial processes are not functionally independent, but are linked in an interactive manner. (+info)
Topographical disorientation: a synthesis and taxonomy. (2/133)Over the last century, several dozen case reports have presented 'topographically disoriented' patients who, in some cases, appear to have selectively lost their ability to find their way within large-scale, locomotor environments. A review is offered here that has as its aim the creation of a taxonomy that accurately reflects the behavioural impairments and neuroanatomical findings of this literature. This effort is guided by an appreciation of the models of normative way-finding offered by environmental psychology and recent neuroscience research. It is proposed that several varieties of topographical disorientation exist, resulting from damage to distinct neuroanatomical areas. The particular pattern of impairments that patients evidence is argued to be consonant with the known functions of these cortical regions and with recent neuroimaging results. The conflicting claims of previous reviews of this area are also considered and addressed. (+info)
Unconscious letter discrimination is enhanced by association with conscious color perception in visual form agnosia. (3/133)Adaptive behavior guided by unconscious visual cues occurs in patients with various kinds of brain damage as well as in normal observers, all of whom can process visual information of which they are fully unaware        . Little is known on the possibility that unconscious vision is influenced by visual cues that have access to consciousness . Here we report a 'blind' letter discrimination induced through a semantic interaction with conscious color processing in a patient who is agnosic for visual shapes, but has normal color vision and visual imagery. In seeing the initial letters of color names printed in different colors, it is normally easier to name the print color when it is congruent with the initial letter of the color name than when it is not . The patient could discriminate the initial letters of the words 'red' and 'green' printed in the corresponding colors significantly above chance but without any conscious accompaniment, whereas he performed at chance with the reverse color-letter mapping as well as in standard tests of letter reading. We suggest that the consciously perceived colors activated a representation of the corresponding word names and their component letters, which in turn brought out a partially successful, unconscious processing of visual inputs corresponding to the activated letter representations. (+info)
Receptive amusia: evidence for cross-hemispheric neural networks underlying music processing strategies. (4/133)Perceptual musical functions were investigated in patients suffering from unilateral cerebrovascular cortical lesions. Using MIDI (Musical Instrument Digital Interface) technique, a standardized short test battery was established that covers local (analytical) as well as global perceptual mechanisms. These represent the principal cognitive strategies in melodic and temporal musical information processing (local, interval and rhythm; global, contour and metre). Of the participating brain-damaged patients, a total of 69% presented with post-lesional impairments in music perception. Left-hemisphere-damaged patients showed significant deficits in the discrimination of local as well as global structures in both melodic and temporal information processing. Right-hemisphere-damaged patients also revealed an overall impairment of music perception, reaching significance in the temporal conditions. Detailed analysis outlined a hierarchical organization, with an initial right-hemisphere recognition of contour and metre followed by identification of interval and rhythm via left-hemisphere subsystems. Patterns of dissociated and associated melodic and temporal deficits indicate autonomous, yet partially integrated neural subsystems underlying the processing of melodic and temporal stimuli. In conclusion, these data contradict a strong hemispheric specificity for music perception, but indicate cross-hemisphere, fragmented neural substrates underlying local and global musical information processing in the melodic and temporal dimensions. Due to the diverse profiles of neuropsychological deficits revealed in earlier investigations as well as in this study, individual aspects of musicality and musical behaviour very likely contribute to the definite formation of these widely distributed neural networks. (+info)
Illusory limb movements in anosognosia for hemiplegia. (5/133)To clarify the relation between anosognosia for hemiplegia and confabulation, 11 patients with acute right cerebral infarctions and left upper limb hemiparesis were assessed for anosognosia for hemiplegia, illusory limb movements (ILMs), hemispatial neglect, asomatognosia, and cognitive impairment. Five of 11 patients had unequivocal confabulation as evidenced by ILMs. The presence of ILMs was associated with the degree of anosognosia (p = 0.002), with hemispatial neglect (p<0.05), and with asomatognosia (p<0.01). The results confirm that a strong relation exists between anosognosia for hemiplegia and confabulations concerning the movement of the plegic limb. There is also a strong relation between ILMs and asomatognosia. (+info)
Hemianopic colour blindness. (6/133)A man developed cortical blindness after cerebral infarction in the distribution of both posterior cerebral arteries. When he recovered from this condition, he was found to be colour blind in the left visual field, but not in the right. This unusual situation resulted in apparently contradictory performances on hemifield and free-field tasks of colour discrimination, naming, and recognition. The contradictions may be explained by interhemispheric competition between a hemisphere which could discriminate colours and a hemisphere which was colour blind. (+info)
Patterns of music agnosia associated with middle cerebral artery infarcts. (7/133)The objective of the study is to evaluate if the rupture of an aneurysm located on the middle cerebral artery (MCA) results in disorders of music recognition. To this aim, 20 patients having undergone brain surgery for the clipping of a unilateral left (LBS), right (RBS) or bilateral (BBS) aneurysm(s) of the MCA and 20 neurologically intact control subjects (NC) were evaluated with a series of tests assessing most of the abilities involved in music recognition. In general, the study shows that a ruptured aneurysm on the MCA that is repaired by brain surgery is very likely to produce deficits in the auditory processing of music. The incidence of such a deficit was not only very high but also selective. The results show that the LBS group was more impaired than the NC group in all three tasks involving musical long-term memory. The study also uncovered two new cases of apperceptive agnosia for music. These two patients (N.R. and R.C.) were diagnosed as such because both exhibit a clear deficit in each of the three music memory tasks and both are impaired in all discrimination tests involving musical perception. Interestingly, the lesions overlap in the right superior temporal lobe and in the right insula, making the two new cases very similar to an earlier case report. Altogether, the results are also consistent with the view that apperceptive agnosia results from damage to right hemispheric structures while associative agnosia results from damage to the left hemisphere. (+info)
Time-dependent activation of parieto-frontal networks for directing attention to tactile space. A study with paired transcranial magnetic stimulation pulses in right-brain-damaged patients with extinction. (8/133)Tactile extinction has been interpreted as an attentional disorder, closely related to hemineglect, due to hyperactivation of the unaffected hemisphere, resulting in an ipsilesional attentional bias. Paired transcranial magnetic stimulation (TMS) techniques, with a subthreshold conditioning stimulus (CS) followed at various interstimulus intervals (ISIs) by a suprathreshold test stimulus (TS), are useful for investigating intracortical inhibition and facilitation in the human motor cortex. In the present work, we investigated the effects of paired TMS over the posterior parietal and frontal cortex of the unaffected hemisphere in a group of eight right-brain-damaged patients with tactile extinction who were carrying out a bimanual tactile discrimination task. The aim of the study was to verify if paired TMS could induce selective inhibition or facilitation of the unaffected hemisphere depending on the ISI, resulting, respectively, in an improvement and a worsening of contralesional extinction. In addition, we wanted to investigate if the effects of parietal and frontal TMS on contralesional extinction appeared at different intervals, suggesting time-dependent activation in the cortical network for the processing of tactile spatial information. Paired TMS stimuli with a CS and a TS, separated by two ISIs of 1 and 10 ms, were applied over the left parietal and frontal cortex after various intervals from the presentation of bimanual cutaneous stimuli. Single-test parietal TMS stimuli improved the patients' performance, whereas paired TMS had distinct effects depending on the ISI: at ISI = 1 ms the improvement in extinction was greater than that induced by single-pulse TMS; at ISI = 10 ms we observed worsening of extinction, with complete reversal of the effects of single-pulse TMS. Compared with TMS delivered over the frontal cortex, parietal TMS improved the extinction rate in a time window that began earlier. These findings shed further light on the mechanism of tactile extinction, suggesting relative hyperexcitability of the parieto-frontal network in the unaffected hemisphere, which is amenable to study and modulation by paired TMS pulses. In addition, the results show time-dependent processing of tactile spatial information in the parietal and frontal cortices, with a bimodal distribution of activity, at least in the attentional network of the unaffected hemisphere. (+info)
There are several subtypes of agnosia, each with distinct symptoms:
1. Visual agnosia: Difficulty recognizing objects, colors, or shapes.
2. Auditory agnosia: Inability to recognize familiar sounds or voices.
3. Tactile agnosia: Difficulty identifying objects by touch.
4. Olfactory agnosia: Loss of the ability to smell.
5. Gustatory agnosia: Inability to taste or identify different flavors.
6. Hyperagnosia: Excessive sensitivity to stimuli, leading to over-recognition of objects and excessive memory for details.
7. Hypoagnosia: Under-recognition of objects, leading to difficulty identifying familiar items.
Agnosia can be caused by various factors, such as stroke, traumatic brain injury, infections, neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease), and developmental disorders (e.g., autism spectrum disorder). Treatment options depend on the underlying cause of the agnosia and may include rehabilitation therapies, medications, or surgery.
In summary, agnosia is a neurological condition characterized by difficulty in recognizing objects, voices, or other sensory stimuli due to damage to specific areas of the brain. It can affect one or more senses and can be caused by various factors. Treatment options vary depending on the underlying cause of the disorder.
The symptoms of Gerstmann syndrome usually begin in adulthood and can vary in severity. Affected individuals may experience memory loss, confusion, difficulty with language, and problems with coordination and balance. As the disease progresses, they may also experience seizures, weakness, and paralysis.
Gerstmann syndrome is diagnosed through a combination of clinical evaluation, laboratory tests, and imaging studies. There is no cure for the disorder, but various treatments can help manage its symptoms. These may include medications to control seizures and muscle spasms, physical therapy to maintain mobility and strength, and speech and language therapy to improve communication skills.
The progression of Gerstmann syndrome is variable, with some individuals experiencing a rapid decline in cognitive and motor functions while others may remain relatively stable for several years. The mean age of death is in the mid-50s, but some individuals may live into their 70s or 80s.
The exact prevalence of Gerstmann syndrome is not known, but it is estimated to affect approximately one in a million people worldwide. It is considered a rare disorder and is often misdiagnosed as other neurodegenerative conditions such as Alzheimer's disease or Parkinson's disease.
Overall, Gerstmann syndrome is a rare and debilitating neurodegenerative disorder that affects cognitive and motor functions, and its diagnosis and management can be challenging for healthcare providers.
The main symptoms of Kluver-Bucy syndrome include:
1. Focal seizures, which may be simple or complex partial seizures.
2. Memory loss and difficulty with learning new information.
3. Difficulty with recognizing objects and faces.
4. Increased libido and sexual interest in inappropriate situations.
5. Hyperorality, meaning an excessive interest in food and eating.
6. Hypermetria, which is the increased size of handwriting or other motor skills.
7. Hemiparesis, which is weakness or paralysis of one side of the body.
8. Visual field defects, including blind spots.
9. Difficulty with speech and language processing.
10. Increased aggression and irritability.
Kluver-Bucy syndrome can be caused by various conditions that damage the brain, such as traumatic brain injury, stroke, cerebral vasculitis, or neurodegenerative diseases like Alzheimer's disease or Pick's disease. It is important to note that Kluver-Bucy syndrome is a relatively rare condition and should be differentiated from other neurological disorders that may present with similar symptoms, such as frontotemporal dementia or progressive supranuclear palsy.
There is no cure for Kluver-Bucy syndrome, but various treatments can help manage its symptoms, including anticonvulsants for seizures, physical therapy to improve motor function, and behavioral therapy to address aggression and other behavioral issues. The prognosis for individuals with Kluver-Bucy syndrome is generally poor, with a significant decline in cognitive and functional abilities over time. However, the condition can be challenging to diagnose, and some individuals may experience a relatively mild course of symptoms or even partial recovery with treatment.
The term "prosopagnosia" comes from the Greek words "prosopon," meaning "face," and "agnosia," meaning "not knowing." It is a rare condition, estimated to affect only about 2% of the population.
People with prosopagnosia may experience a range of symptoms, including:
* Difficulty recognizing familiar faces, both in person and in photographs
* Trouble distinguishing between different faces, especially when the faces are not well-lit or are seen from a distance
* Memory lapses for faces, making it difficult to remember past encounters with individuals
* Confusion between faces of people they know and those they do not know
* Difficulty recognizing their own face in a mirror or in photographs
The exact cause of prosopagnosia is not fully understood, but research suggests that it may be related to abnormalities in the brain's face-processing centers. Some studies suggest that the condition may be hereditary, while others point to possible causes such as stroke, head injury, or neurodegenerative diseases like Alzheimer's or Parkinson's.
There is currently no cure for prosopagnosia, but there are strategies and techniques that can help individuals with the condition manage their symptoms. These may include:
* Using alternative methods of identification, such as voice recognition or clothing style
* Creating associations between faces and other distinguishing features, such as hairstyle or body shape
* Developing a system for keeping track of names and faces, such as using mnemonic devices or keeping a face database
* Seeking support from family, friends, and mental health professionals to cope with the social and emotional challenges of living with prosopagnosia.
Overall, prosopagnosia is a complex and poorly understood condition that can significantly impact an individual's daily life and relationships. Research into its causes and effective treatments is ongoing, offering hope for those affected by the condition.
There are several types of aphasia, including:
1. Broca's aphasia: Characterized by difficulty speaking in complete sentences and using correct grammar.
2. Wernicke's aphasia: Characterized by difficulty understanding spoken language and speaking in complete sentences.
3. Global aphasia: Characterized by a severe impairment of all language abilities.
4. Primary progressive aphasia: A rare form of aphasia that is caused by neurodegeneration and worsens over time.
Treatment for aphasia typically involves speech and language therapy, which can help individuals with aphasia improve their communication skills and regain some of their language abilities. Other forms of therapy, such as cognitive training and physical therapy, may also be helpful.
It's important to note that while aphasia can significantly impact an individual's quality of life, it does not affect their intelligence or cognitive abilities. With appropriate treatment and support, individuals with aphasia can continue to lead fulfilling lives and communicate effectively with others.
Associative visual agnosia
Auditory verbal agnosia
Inferior longitudinal fasciculus
Jason Walter Brown
Visual object recognition (animal test)
Language processing in the brain
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- Epilepsy: syndrome of Landau-Kleffner giving an acquired verbal auditory agnosia. (dd-database.org)
- 1. Nonverbal auditory agnosia with lesion to Wernicke's area. (nih.gov)
- 6. Auditory agnosia and auditory spatial deficits following left hemispheric lesions: evidence for distinct processing pathways. (nih.gov)
- 8. The functional anatomy of recovery from auditory agnosia. (nih.gov)
- 14. Generalized auditory agnosia with spared music recognition in a left-hander. (nih.gov)
- 16. Auditory agnosia. (nih.gov)
- 18. Clinical and audiological findings in a case of auditory agnosia. (nih.gov)
- Research on the use of interventions for agnosias were difficult to come across in the literature, especially auditory and tactile agnosias. (weebly.com)
Treatment of agnosia2
- 1. We report measurements on a single patient, HJA, who has exhibited visual form agnosia since suffering a stroke. (ox.ac.uk)
- The form agnosia is the inability to discriminate against the basic geometric shapes, the integrative agnosia is the absence of coherent global integration of information. (dd-database.org)
- Few individuals with agnosia regain sensory functioning but most make gains within the first few months or year of diagnosis (Rogers, n.d. (weebly.com)
- Astereognosis (or tactile agnosia if only one hand is affected) is the inability to identify an object by active touch of the hands without other sensory input, such as visual or sensory information. (wikipedia.org)
- Tactile agnosia is characterized by an inability to perceive the shape and nature of an object by touch alone, despite unimpaired sensation to light touch, position, and other primary sensory modalities. (nih.gov)
- Consider participating in a clinical trial so clinicians and scientists can learn more about agnosia and related disorders. (nih.gov)
-  These symptoms suggest that a very specific part of the brain is responsible for making the connections between tactile stimuli and functions/relationships of those stimuli, which, along with the relatively low impact this disorder has on a person's quality of life, helps explain the rarity of reports and research of individuals with tactile agnosia. (wikipedia.org)
- d) infarction in the territory of right posterior cerebral artery causes pure agnosia for streets and defective route finding that do not accompany visual agnosia for other stimuli. (nii.ac.jp)
- Agnosia (also known as primary visual agnosia, monomodal visual amnesia, and visual amnesia) is a neurological disorder characterized by an inability to recognize and identify objects or persons using one or more of the senses. (nih.gov)
- There are, however, several case studies on visual forms of agnosias in the literature. (weebly.com)
- Visual Agnosia is rare, so rare that I found out last year when I was 58 that the visual impairment that I have had all of my life was due to visual agnosia . (themighty.com)
- My high functioning autism renders me light sensitive and with visual agnosia . (themighty.com)
- Visual agnosia has been well studied by anatomical, neuropsychological and neuroimaging studies. (elsevier.com)
- We carried out electrophysiological examinations on a 23-year-old man with associative visual agnosia, prosopagnosia and cerebral achromatopsia to evaluate the higher brain dysfunctions of visual recognition. (elsevier.com)
- Therefore, CS-VEPs and ERPs with color and motion discrimination tasks are useful methods for assessing the functional changes of visual recognition such as visual agnosia. (elsevier.com)
- What does visual agnosia tell us about perceptual organization and its relationship to object perception? (nih.gov)
- The conditioning of sexual behavior by visual agnosia. (nih.gov)
- 17. Pure word deafness with auditory object agnosia after bilateral lesion of the superior temporal sulcus. (nih.gov)
- The perception of the form associative agnosia is normal but the perception of the meaning of the object is reduced. (dd-database.org)
- While astereognosis is characterized by the lack of tactile recognition in both hands, it seems to be closely related to tactile agnosia (impairment connected to one hand). (wikipedia.org)
- Occupational therapy (OT) is often involved with providing strategies to help individuals with agnosia and his or her caregivers cope and adapt. (weebly.com)
- If agnosia is caused by an underlying disorder, treatment of that disorder may reduce symptoms and help prevent further brain damage. (nih.gov)
- La agnosia táctil se caracteriza por la incapacidad para percibir la forma y naturaleza de un objeto solo por el tacto, a pesar de no estar alterada la sensibilidad al tacto ligero, posición y otras modalidades sensitivas primarias. (bvsalud.org)
- The deficit of the perception of forms aperceptive agnosia. (dd-database.org)
- He nosologically assigned pain asymbolia to the group of agnosias and integrated it into the concept of body image, which was a central issue in his entire scientific work. (nih.gov)
-  As opposed to agnosia, when the object is observed visually, one should be able to successfully identify the object. (wikipedia.org)
- Individuals with tactile agnosia may be able to identify the name, purpose, or origin of an object with their left hand but not their right, or vice versa, or both hands. (wikipedia.org)
- The databases of PubMed, Google Scholar, and Western University library's Summon feature were utilized using keywords "agnosia" AND "rehabilitation" OR "intervention" OR "treatment" for this search. (weebly.com)
- Learn about clinical trials currently looking for people with agnosia at Clinicaltrials.gov . (nih.gov)
- 3. [Dysprosody associated with environmental auditory sound agnosia in right temporal lobe hypoperfusion--a case report]. (nih.gov)
- Interventions tend to focus on helping individuals with agnosia cope with their condition. (weebly.com)
- In addition, controlled treatment studies with individuals with agnosia are rare. (weebly.com)
- Tactile agnosia observations are rare and case-specific. (wikipedia.org)
- More research needs to be conducted on general interventions for agnosias. (weebly.com)
- Several case studies surrounding agnosias exists in the literature. (weebly.com)