Claviceps purpurea, cause of the crop disease known as wild ergot (or Jack-in-the-Rye), is a natural source of the hallucenogen LSD. Some sholars speculate that an outbreak of wild ergot may have been responsible for the hallucinations associated with the Great Awakening in 17th century America. The parasite causes the production of a long, dark purple spur (hence the species name "purpurea") which contains the dormant fungus. During this doimrant phase the fungus produces several defense chemicals known as alkaloids, as well as lysegric acid and related compounds. These latter compounds can cause the reported psychotrophic effects.
Got this from
here.
I think I read somewhere this is the basis for the myth about the werewolf. Bread made from rye that is infected can wreak from havoc on the mind.
Perhaps in your characters food stores there is rye bread that is infected? In today's world, there is a decent chance of this popping up, IMHO, what with the "organic" and "free range" food sources becoming popular.
Maybe a crew menber picked up a real, home made rye bread loaf to take along as a treat, it was put in cold storage. While having a meal from foil packets and freeze dried ice cream, said crew member whips out the loaf as some "real" back home earth food.
Just a thought.
There are also quite a lot of fungi that can cause hallucinations. Perhaps a a prankster put magic mushrooms into food processed for the space voyage?
Also, I found this about serotonin and night terrors (I have experienced night terrors all my life, trust me, they seem real when they are happening!)
According to NASA, about 2/3 of the astronauts experience it shortly after entry to the orbit because of the loss of gravitational field (2). Within the Earth's gravitational field, vestibular system in the inner ear senses the direction of the force and uses the information, along with the visual and other inputs, to interpret the head and body position (2), (3). However in a zero-gravitational field, vestibular system cannot feel the gravity and sends the brain different signals from visual and other sensory inputs (2), (3). This set of different sensory inputs does not match with any of the previously stored neural patterns, and the brain interprets this mistracking as the effects of neurotoxins (2), (4). Consequently, the brain triggers vomiting as a defense mechanism to expel the poisons from the stomach, into which the toxins have possibly entered with food (4), (6).
Hallucination and motion sickness seem very different, but a neurotransmitter serotonin links them together. Serotonin affects various conditions in one's body, such as emotions, sleep cycles, pituitary hormone secretion, appetite control, and pain perception (6), (7), (8), (9). The most important function for motion sickness is appetite control. After each meal, individual's glucose concentration in blood increases, and high blood sugar level stimulates the release of insulin, which then increases the brain level of the amino acid tryptophan, a serotonin precursor (6), (7). High serotonin concentration decreases one's desire to eat because sugar consumption is unnecessary when the glucose level is high (6), (7). Nausea and vomiting usually occurs when one overeats, hence when the blood sugar and serotonin concentrations are extremely high. Similarly, even without overeating, nausea and vomiting in motion sickness may result from abnormally high serotonin level. When the mismatch happens in the brain, the alarmed brain misunderstands that some poisonous agents have entered the stomach, and it probably signals to release more serotonin to induce vomiting so that the toxin will exit the body. As well as in vomiting, the release of serotonin is necessary in inducing hallucination during sleep paralysis. In addition to the functions described the previous paragraph, serotonin causes the smooth muscles of blood vessels to constrict and raises the blood pressure (8), (10). When the blood pressure increases in the brain, the membrane potential in the optic/auditory cortex change, and triggers hallucination. In the last paper, my main hypothesis has focused on fear as the major hallucination-stimulating factor, for it stimulates fight-or-flight response and release of serotonin (1). And yet, because the brain's confused state in motion sickness establishes high serotonin level in the body, the increased serotonin concentration in hallucination during sleep paralysis may also follow the mismatch between internal expectation and sensory input.
My hypothesis suggests that hallucination during sleep paralysis and motion sickness both involve in confusion in the brain and consequently, an increase in serotonin level; however the outcome differs in these cases. The lack of vomiting in a sleep paralysis episode may be due to the neural inhibitors, which prevents the major muscle movements from acting out a dream.
This came from
here.
Hope this was helpful.
