Sexual orientation-related differences in allocentric spatial memory tasks

Spatial memory in mammals, including humans, appears highly sexually dimorphic. The present investigation sought to examine if spatial learning and spatial memory in humans is also linked to sexual orientation. This was achieved by using virtual reality versions of two classic paradigms developed in animal models of hippocampal functioning, the Morris Water Maze (MWM) and Radial Arm Maze (RAM). Here, we show that in contrast to heterosexual men, and in congruence with heterosexual women, homosexual men displayed significantly greater search latencies (spatial learning) during a virtual Morris Water Maze. During a virtual 8-arm Radial Arm Maze, heterosexual males had significantly shorter search latency than heterosexual females, and did not differ from homosexual males. Statistical modeling revealed that variations in neurodevelopmental markers previously associated with human sexual orientation (2nd to 4th finger length ratios and older fraternal siblings) differentially predicted MWM probe trial performance and RAM search latencies only. These data may limit the number of possible neurodevelopmental pathways responsible for sexual variation in components of spatial learning and memory.