Measuring the postsynaptic strength of a single spine using glutamate uncaging.

A, A spine from a neuron filled with Alexa 594 dye with ROI for uncaging shown in green; scale, 1micrometer.
B, The map of uncaging locations within the ROI indicated in A. Three examples of uEPSCs are from locations

indicated by arrows. Calibration: 5pA, 5 ms. Different uncaging locations yielded uEPSCs ranging from negligible
to 25 pA. C, The same map but smoothed by interpolation.

D, The spatial distribution of fluorescence along the dotted line in A (red) showing that the spine diameter as
estimated by full width at half maximum (FWHM) is 0.5 mm. Blue line, The distribution of the uncaging response,
which is slightly narrower (FWHM, 0.4 mm) than the diameter of the spine.