Jung believed a main function of dreams was compensation, which is the expression of thoughts or emotions opposite of those we have when conscious. In addition to Freud's and Jung's theories, other theories as to the function of dreams have been advanced and this topic is still debated. The activation-synthesis theory suggests that dreams are the response of the cortex to pulsed signals from the brain stem. This means that dreams are a physiological function with little psychological purpose. Francis Crick and Graeme Mitchinson have suggested that, during dreams, the brain is filtering data taken in during the day and stored in the cortex, in order to eliminate redundant or unimportant information.
Dreams then are simple a result of all the released data.
Rosalind Cartwright and others have advanced theories to suggest that dreams are extensions of our conscious thought processes and may serve the function of creative problem solving. TM uses the concentration method to achieve the relaxed state, which involves deep focus on a mantra, which is a special word uniquely assigned to each individual. Though the effects of meditation are debated, studies show physiological signs of relaxation and dedicated meditators insist that there are many psychological benefits, as well. Repeated use of these drugs can lead to tolerance, physical dependence, and psychological dependence. Tolerance is when the intensity of the drug's effects decrease, such that larger doses of the drug are required to produce the desired effects.