As the Wikipedia article says,
High levels of the neurotransmitter dopamine (or its agonists) in the ventral tegmental area of the brain have been shown to decrease latent inhibition. Certain dysfunctions of the neurotransmitters glutamate, serotonin and acetylcholine have also been implicated.
Is it possible to decrease latent inhibition outside the laboratory using widely available products (such as certain foods or drugs) or regimens?
Matt has the right direction but it's not the whole answer. As he explains, taking a metabolic precursor to dopamine will increase the amount of dopamine available to the brain. L-Dopa, tyrosine and tyrosine's precursor phenylalanine are possibilities.
Even if taking any of these precursors may raise the amount of dopamine available to the brain, it doesn't mean that significantly higher than baseline levels of dopamine will be released into synapses for an extended period. There's a few studies on the subject.
Although supplements alone won't necessarily decrease latent inhibition, other drugs can potentiate their effect.
The line you quoted from Wikipedia cites its source as a study which actually answers your question. In the study, administration of amphetamine disrupted visual latent inhibition in study subjects. Amphetamine is known as a reuptake inhibitor, and inhibits the re-uptake, or recycling process of various neurotransmitters, including dopamine, causing them to continually activate receptors.
Phenylalanine, tyrosine, and caffeine: caffeine is a stimulant and has been shown to increase dopamine release, supplementation of dopamine precursors ensures that there's extra dopamine to go around. Check your 5 hour energy ingredient label, they use this technique.
Another brain system to research would be the endocannabinoid system. The effect of the stimulant drugs which we just covered are actually blocked when cannabinoid receptors are blocked, suggesting the dopamine system is not the only variable in low latent inhibition. THC is a chemical that you've probably heard about, which activates cannabinoid receptors in the brain. THC can increase an individual's ability to link disparate ideas and concepts, and its use has shown to correlate with a slight increased risk for schizophrenia, a form of psychosis which some believe is related to too little latent inhibition.
I don't know of a study that directly links cannabinoids and latent inhibition.
springerlink.com is broken. I'm not able to find any copy saved on the Wayback Machine, either.
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According to your snippet, increasing dopamine in the brain will decrease latent inhibition.
Dopamine is produced in the body from the chemical L-dopa.
Wikpedia states that dopamine will not cross the blood-brain barrier, so to increase dopamine levels in the brain L-dopa must be used.
Wikipedia also says that there is a herbal extract containing L-dopa called velvet bean. Wikipedia provides another solution, which uses the amino acid Tyrosine which is the precursor to L-dopa, as well as dopamine, adrenaline and noradrenaline. So, be aware that use of this amino acid won't just increase your L-dopa levels.
A red herring I found were melanocytes, which produce L-dopa as part of the melanin synthetic cascade, however the amount produced is negligible.
Aside from chemical alteration, what lowering latent inhibition entails is ignoring fewer things. Making cognitive filters less strict. Essentially this becomes a problem of attention - how to attended to things that haven't helped (haven't been reinforced) in similar situations.
It just so happens that there is a psychological phenomenon called latent learning. The classic experiment is one where some rats are allowed to roam freely in a maze with no objective, while the rest aren't. Later, when each rat is put into the maze to find food, the ones that have previously been in the maze find food more quickly. The rats learnt about the maze without reinforcement.
I would therefore suggest that to decrease latent inhibition you must deliberately pay more attention to your surroundings.
It isn't humanly possible to pay more attention to your surroundings to level like someone who has LLI can. I have LLI and saying that people can make a conscious decision to absorb more in their surroundings is like telling someone they can breath more oxygen than their lungs normally can by thinking really hard about it. It isn't possible to induce LLI and it can only be something you are born with. You can train yourself to be more aware of your surroundings, but your body will naturally block out the stimuli after it reaches its natural max. People with LLI can't block out incoming stimuli which is why sometimes it can lead to severe mental illness.
I wouldn't recommend anyone purposefully attempting to induce low latent inhibition as if they haven't lived with it their entire lives, it will be extremely overwhelming for their brain as it basically wont at all be used to handling the sheer volume of stimuli. That is often why those who smoke marijuana can experience paranoia, they have lowered their latent inhibition by taking marijuana due to the dopamine and THC, and their brain then starts to pick up on forms of stimuli it doesn't usually - for example the person may notice sounds that they haven't previously noticed and will usually assume those sounds are to do with them as an individual (hence bringing about paranoia). Someone who's lived with LLI in the same circumstance as the one mentioned above would however have been noticing those sounds their entire life and would be able to objectively categorize them rather than experiencing the sort of "What are these sounds to do with me and why are they now here" effect. The sounds have always been there, they just haven't noticed them without having low latent inhibition.
That is what life is like for those with low latent inhibition - they notice things all around them that the majority of others simply do not.
