Space-time wiring specificity supports direction selectivity in the retina.

How does the mammalian retina detect motion? This classic problem in visual neuroscience has remained unsolved for 50 years. In search of clues, here we reconstruct Off-type starburst amacrine cells (SACs) and bipolar cells (BCs) in serial electron microscopic images with help from EyeWire, an online community of 'citizen neuroscientists'. On the basis of quantitative analyses of contact area and branch depth in the retina, we find evidence that one BC type prefers to wire with a SAC dendrite near the SAC soma, whereas another BC type prefers to wire far from the soma. The near type is known to lag the far type in time of visual response. A mathematical model shows how such 'space-time wiring specificity' could endow SAC dendrites with receptive fields that are oriented in space-time and therefore respond selectively to stimuli that move in the outward direction from the soma.

Effects of intranasal methamphetamine on metacognition of agency.

BACKGROUND: Although methamphetamine abuse has been associated with cognitive deficits, few studies have investigated the acute effects of the drug on complex cognitive performance. This study evaluated the acute effects of intranasal methamphetamine on a computerized task measuring metacognition of agency. PROCEDURE: Ten nontreatment seeking methamphetamine abusers (2F, 8M) completed this four-session, within-participant, double-blind laboratory study; during each session, participants received one of four doses (0, 12, 25, or 50 mg/70 kg) and completed the metacognition of agency task. In this task, participants were instructed to "catch" falling targets with a mouse and then provide metacognitive judgments about their feelings of control. RESULTS: Following placebo, judgments of agency were greater under optimal task conditions compared with less than optimal task conditions. Relative to placebo, the 12-mg dose improved task performance, increased judgments of agency under the optimal condition, and decreased judgments of agency under the less than optimal condition. By contrast, the larger doses (25 and 50 mg) increased judgments of agency only under the optimal condition but disrupted performance under the less than optimal condition. CONCLUSION: These data show that a low intranasal methamphetamine dose enhanced judgments of agency and performance, while larger doses produced limited effects.

Analogous Convergence of Sustained and Transient Inputs in Parallel On and Off Pathways for Retinal Motion Computation.

Visual motion information is computed by parallel On and Off pathways in the retina, which lead to On and Off types of starburst amacrine cells (SACs). The approximate mirror symmetry between this pair of cell types suggests that On and Off pathways might compute motion using analogous mechanisms. To test this idea, we reconstructed On SACs and On bipolar cells (BCs) from serial electron microscopic images of a mouse retina. We defined a new On BC type in the course of classifying On BCs. Through quantitative contact analysis, we found evidence that sustained and transient On BC types are wired to On SAC dendrites at different distances from the SAC soma, mirroring our previous wiring diagram for the Off BC-SAC circuit. Our finding is consistent with the hypothesis that On and Off pathways contain parallel correlation-type motion detectors.