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Study was never officially approved by IRB and never open to enrollment. Submission withdrawn due to lack of funding.
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The purpose of this study is to investigate how visual orientation discrimination and metacognition (i.e., perceptual confidence) are affected by occipital stroke that causes hemianopia and quadrantanopia in adults. This research will provide insight as to how the residual visual system, which not directly damaged by the occipital stroke, processes orientation (assayed in terms of orientation discrimination) and metacognition (by measuring perceptual confidence for orientation discrimination). These measures will be used to refine computational models that attempt to explain how the brain copes with loss of primary visual cortex (V1) as a result of stroke. This knowledge is essential to devise more effective visual rehabilitation therapies for patients suffering from occipital strokes.
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| Measure | Description | Time Frame |
|---|---|---|
| Orientation discrimination threshold | Assessment of Static Orientation Discrimination. For each subject, the investigators will measure the ability to correctly identify the orientation of non-moving visual stimuli that vary in degree of angle tilt to the right or left of vertical. The investigators will measure the degree of angle tilt that can be reliably detected at a 72-75% correct level of performance. Tilt difference from vertical will vary between 80° (maximum) and 0.1° (minimum) based on subject performance and an adaptive staircase that will change tilt magnitude depending on subject performance, increasing the tilt (making the task easier) for each incorrect answers and decreasing tilt (making the task harder) after a number of correct answers in a row. | Baseline |
| Perceptual Confidence in Orientation Discrimination | Assessment of Metacognition (i.e., perceptual confidence) in Orientation Discrimination. For each subject, the investigators will measure their confidence in identifying an object's tilt to the right or left of vertical. A running tally of 'response points' will be collected during the orientation testing. Points will be awarded for each response on a scale, with the highest points awarded for "correct discrimination & high confidence", intermediate points awarded for "correct discrimination & low confidence", followed by "incorrect discrimination & low confidence" and with points subtracted for "incorrect discrimination & high confidence". Total points will be recorded for each test, with the patient asked to accumulate the highest number of points they can during the task. | Baseline |
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Inclusion Criteria:
Exclusion Criteria:
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Subjects will all be individuals who have sustained partial vision loss after an occipital lobe stroke.
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| ID | Term |
|---|---|
| D001766 | Blindness |
| D006423 | Hemianopsia |
| D000083242 | Ischemic Stroke |
| D019575 | Blindness, Cortical |
| D014786 | Vision Disorders |
| ID | Term |
|---|---|
| D012678 | Sensation Disorders |
| D009461 | Neurologic Manifestations |
| D009422 | Nervous System Diseases |
| D005128 | Eye Diseases |
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| D012816 |
| Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D020521 | Stroke |
| D002561 | Cerebrovascular Disorders |
| D001927 | Brain Diseases |
| D002493 | Central Nervous System Diseases |
| D014652 | Vascular Diseases |
| D002318 | Cardiovascular Diseases |