In most of the body’s tissues, the brain relay on the right side of the brain governs organs and tissues on the left side of the body, and vice versa. This crossover begins at the cerebellum (old mesoderm germ layer) and continues through the cerebral medulla (new mesoderm) and cerebral cortex (ectoderm).

No Crossover in the Brainstem

Crossover does not apply to brainstem (endoderm) brain relays and tissues.

For brainstem-relayed programs, conflicts about “incoming” morsels relay on the right side of the brainstem and, for pairs of organs, also on the right side of the body (or the digestive tract above the duodenum). Conflicts about “outgoing” morsels relay on the left side of the brainstem and, for pairs of organs, also on the left side of the body (or the digestive tract from the duodenum down).

Because there’s no crossover in endoderm (brainstem-controlled) tissues, a special biological program involving endoderm tissue on the right side of the gullet (e.g. the right salivary glands or the right side of the thyroid gland) will be about “claiming” morsels, and a special biological program involving endoderm tissue on the left side of the gullet will be about “getting rid of” or “spitting out” an unwanted morsel.

“Double” Crossover

A small number of organs appear at first not to follow the crossover rule — most notably the retinas and the heart muscle (myocardium). In fact, these organs do cross over, but then cross over a second time, so that the right brain relay connects to the right-side organ and the left brain relay connects to the left-side organ. The net result looks like no crossover, but the underlying neurological principle is the same.

Crossover in the Temporal Lobes

In the temporal lobe relays of the cerebral cortex, crossover only applies to demarcation conflicts, in which a demarcation conflict on the right temporal lobe will relay to the left side of the urinary tract, and a demarcation conflict on the left temporal lobe will relay to the right side of the urinary tract.

A Note on Terminology

Crossover is one of the most commonly misrepresented concepts in GNM, particularly in AI-generated content, which frequently conflates laterality, hormone status, and the partner/mother-child distinction into a single undifferentiated idea. For example, a common AI error is to equate the left hemisphere with feminine hormone status and therefore with the mother-child side; however, these are entirely separate systems. Hormone status is determined by temporal lobe conflict activity and endocrine conditions; laterality is determined at conception and never changes; and partner/mother-child mapping is determined by how the individual subjectively perceives the relationship involved in the conflict.