The contrast dependence of the cortical fMRI deficit in amblyopia; a selective loss at higher contrasts
Bibliographic record
Abstract
Although there is general agreement that the fMRI cortical response is reduced in humans with amblyopia, the deficit is subtle and has little correlation with threshold-based psychophysics. From a purely contrast sensitivity perspective, one would expect fMRI responses to be selectively reduced for stimuli of low contrasts. However, to date, all fMRI stimuli used in studies of amblyopia have been of high contrast. Furthermore, if the deficit is selective for low contrasts, one would expect it to reflect a selective M-cell loss, because M-cells have much higher contrast gain than P-cells and make a larger contribution to the threshold detection of stimuli of low spatial and medium temporal frequencies. To test these two predictions, we compared % BOLD response between the eyes of normals and amblyopes for low- and high-contrast stimuli using a phase-encoded design. The results suggest that the fMRI deficit in amblyopia depends upon stimulus contrast and that it is greater at high contrasts. This is consistent with a selective P-cell contrast deficit at a precortical or early cortical site.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".