Table 1.

Place unit metrics

Metrics	Mean	SD	Maximum	Minimum
Spatial information	1.01	0.66	4.56	0.13
Coherence	0.83	0.15	0.98	0.06
Selectivity	8.79	7.36	57.09	2.07

Values are calculated by combining the results of the 687 CA1 units across four subjects that had either journey-dependent or -independent place fields. Spatial information, given in bits, is derived by considering a cell as a communication channel whose input is the device's location. Coherence is a nearest-neighbor 2D autocorrelation that measures the smoothness of firing. Selectivity is an arbitrary measure equal to the spatial maximum firing rate divided by the mean firing rate of the neuronal unit. The place units from Darwin XI's CA1 possess fields that have metrics comparable to rodent hippocampus (22, 23).