Mental representation of space: insights from an oblique distribution of hallucinations.

Hallucinations experienced during sleep paralysis—both sensory and motor—tend to be projected toward the lower-left and especially the upper-right region of external space, a pattern that exceeds what would be expected from simply adding separate left-right and up-down biases. This oblique bias suggests a systematic link between hemispheric brain organization and ventral/dorsal cerebral pathways, adding to evidence that spatial preferences are multidimensional and not merely additive. The findings come from analyzing the three-dimensional distribution of hypnagogic and hypnopompic hallucinations, offering a window into internal spatial representation free from typical task-related influences.

Study at a glance

Abstract

Three-dimensional spatial distributions of hypnagogic and hypnopompic hallucinations associated with sleep paralysis were used to investigate the internal representation of space. Left-right asymmetries in human preferences and abilities are well established. Parallel effects are also observed as lower-upper asymmetries. These parallels could reflect common underlying mechanisms or additive effects of independently evolved horizontal and vertical asymmetries. This study adds to the growing literature on multidimensional spatial biases in a context free from the influence of task-related factors. We present evidence of an oblique bias in the projection of both sensory and motor hallucinations toward lower-left and especially upper-right external space exceeding that accounted for by an additive model of separate horizontal and vertical biases. These observations are consistent with theories regarding a systematic functional relation of hemispheric with ventral and dorsal cerebral organization.