Response properties of a CPU1 columnar neuron.A, Intracellular recording, showing tonic excitation (at 120°, 90°) or inhibition (at 30°, 0°, 180°) to dorsal polarized light. Note pronounced rebound reactions after lights off. Weak inhibitory responses also occur to illumination from frontal (front) and from the left (le) but not to light from dorsal and from the right (dors, ri). Calibration: 20 mV, 2 sec. B, Frontal reconstruction of the neuron. It innervates column L6 in the lateral hemisphere of the protocerebral bridge (PB), the innermost contralateral column in layer 1 of the upper division of the central body (CBU), and large areas in the contralateral accessory lobe (LAL). Scale bar, 100 μm.C, e-vector response plot (means ± SD; n = 2). Solid line, Background activity. Sin2-fitting (stippled line) reveals a Φmax of 102.2°.D, Distribution of Φmax from six columnar neurons of the central complex.