Figure 1: Intracellular measures of resolution in light adapted honey bee photoreceptors.
From: Visual acuity of the honey bee retina and the limits for feature detection
(a) Example responses to red, green or blue bars swept through the receptive field (width: 4°, length 90°, velocity 80°/s) against a black background (responses are normalized to maximum response, i.e. to the white bar). All photoreceptors included in further analysis displayed similar spectral sensitivity with maximal response to green features. (i.e. green-sensitive or long-wavelength photoreceptor type). The raw 2-dimensional receptive field of a frontal photoreceptor was obtained by scanning its receptive field horizontally with a black square target (3 deg2) at a velocity of 32°/s across a vertical series of scan lines 0.13° apart. Colours show deflection in membrane potential in mV. (b) Estimates of individual photoreceptor receptive fields across the eye (N = 18). Ellipses denote relative sizes of angular sensitivity. Arrows denote frontal and lateral body axes (F: 0° azimuth, 0° elevation, L: 90° azimuth, 0° elevation) and the dorsal pole. The grey shading indicates lateral and frontal subsets of photoreceptors. Coloured plots show example 2D Gaussian kernel fits that account for the individual receptive fields from one frontal and one lateral photoreceptor, together with the vertical (dotted line) and horizontal (unbroken line) components of the angular half-width, Δρ. (c) Horizontal (⦁) and vertical (⚬) estimates of angular sensitivity (Δρ) in photoreceptors recorded across the eye as in (b). Least-square regression lines are reported for horizontal (unbroken line) and vertical (dotted line) components. Both Δρh and Δρv increase with increasing eccentricity, calculated as Euclidean distance from the frontal body axis (0° azimuth and 0° elevation).
