The effect of pharmacological intervention on contrast sensitivity deficits in phenylketonuria
Bibliographic record
Abstract
Patients with the autosomal recessive disorder phenylketonuria (PKU) have elevated phenylalanine levels that impede production of tyrosine, a precursor to dopamine. Lowered dopamine levels lead to a number of deficits, including lowered visual contrast sensitivity (Diamond & Herzberg, 1996; Gramer et al, 2013; Stemerdink et al, 1999). In the present study we measured contrast sensitivity and blood phenylalanine and tyrosine levels on multiple visits in 10 PKU patients, 5 of whom began a course of sapropterin dihydrochloride (Kuvan®), which reduces phenylalanine levels (in some patients). The expectation was that initial contrast sensitivity would correlate with phenylalanine and tyrosine levels, and that in patients who responded well to sapropterin dihydrochloride, reduced phenylalanine levels would correspond to increased contrast sensitivity. Contrast thresholds for each PKU patient and age-matched controls were determined using a four-alternative forced-choice grating discrimination task with an adaptive staircase (the Freiburg Visual Acuity Test, Bach, 1996; 2007) at five spatial frequencies, on multiple visits (1-4 per patient). On Visit 1, prior to sapropterin dihydrochloride treatment, contrast thresholds were an average of 67% higher in PKU patients than in their age-matched controls, but no correlation between performance and phenylalanine or tyrosine levels was detectable. During sapropterin dihydrochloride treatment, however, phenylalanine levels dropped by half, and contrast sensitivity deficits disappeared entirely. Practice also played a role in improvement: threshold elevations were 10% lower on Visit 2 among those patients who had not begun treatment. Control participants displayed a similar degree of improvement on their second visit. Results during treatment suggest that sapropterin hydrochloride may be effective in reducing both phenylalanine levels and corresponding perceptual deficits in PKU patients. The practice effect, however, raises the possibility that only some of the contrast sensitivity deficit in PKU patients is the result of dopamine-related impairments in the retina or visual cortex. Meeting abstract presented at VSS 2015
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".