Parietal regions specialized for saccades and reach in the human: a rTMS study
Bibliographic record
Abstract
Primate neurophysiology and human brain imaging studies have identified effector-related regions in the posterior parietal cortex (PPC). However, this specialization is less clear in human fMRI studies. Here we used fMRI-derived regions of interest to navigate transcranial magnetic stimulation (TMS) and causally determine saccade and reach specificity in three PPC regions. In experiment 1, six subjects performed memory-guided saccades and reaches with their dominant, right-hand to remembered peripheral targets in complete darkness. During the interval between viewing the target and the saccadic eye- or reach-movement, we applied trains of repetitive TMS to anatomically defined regions of interest from individual subjects - 1) superior parieto-occipital cortex (SPOC); 2) the more anterior-lateral medial intraparietal sulcus (mIPS); and 3) a yet more anterior dorsal-lateral PPC region near the angular gyrus (cIPS) - in both hemispheres. Stimulation to left mIPS and cIPS regions increased reach endpoint variability to rightward (contralateral) targets, whereas stimulation of SPOC deviated reach endpoints towards visual fixation. Only rTMS to right mIPS and cIPS disrupted contraversive saccades. We then repeated experiment 1 with the nondominant left-hand to investigate whether rTMS-induced errors remain spatially fixed or reverse (experiment 2). Here we found that stimulation of right mIPS and cIPS caused a significant increase in endpoint variability to leftward (contralateral) targets. In our final third experiment, we investigated reaching with or without visual feedback from the moving hand to determine whether rTMS disrupted the reach goal or the internal estimate of initial hand position needed to calculate the reach vector. In both mIPS and cIPS visual feedback negated rTMS-induced reach errors, whereas rTMS-induced, directional reach biases in SPOC remained. Collectively, these results show that a more medial region centered on parieto-occipital junction is involved only in planning of reach (encodes goal representation), and more lateral regions in human PPC have multiple overlapping maps for saccade and reach planning (encodes reach vector information).
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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) | 0.002 | 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".