Fig. 7

Trout head direction cells. a Representative trajectory (gray line) with positions showing neuron-generated spikes (red dots) as recorded from the telencephalon of trout swimming in a water tank (scale bar = 10 cm). Remarkable visible objects (pipe for water supply [black filled rectangle], hole for water sink [black filled circle], and radio transceiver [blue filled rectangle]), and compass bearing (bottom, left) are illustrated. b Polar plots of firing rate as a function of head direction, using examples from two representative neurons. The mean vector length (Mv) and peak firing rate (P) are indicated in the images. Visible objects are illustrated as in a. c–d Distribution of mean vector length for randomly shuffled data (c) and for the entire suite of neurons observed in our test trout dorsal palliums (d). The red line and the number indicate the 95th percentile for the shuffled data. e Circular distribution of the number of cells on the head orientation for seven individual head direction cells identified from trout G and #2. Head direction cells exist in the brains of trout G (red) and #2 (blue). In contrast, trout B had no head direction cells. Visible objects are illustrated as in a