5.10 Dreams rarely make sense because they are usually more emotional  (Page 4/5)

Dreaming and the brain

"Although the details of human hopes are surely beyond the imagination of other creatures," writes Jaak Panksepp in Affective Neuroscience: The Foundations of Human and Animal Emotions (1998), "the evidence now clearly indicates that certain intrinsic aspirations of all mammalian minds, those of mice as well as men, are driven by the same ancient neurochemistries."

Panksepp describes the SEEKING system as follows:

• This emotional system is a coherently operating neuronal network that promotes a certain class of survival abilities. This system makes animals intensely interested in exploring their world and leads them to become excited when they are about to get what they desire. It eventually allows animals to find and eagerly anticipate the things they need for survival, including, of course, food, water, warmth, and their ultimate evolutionary survival need, sex. In other words, when fully aroused, it helps fill the mind with interest and motivates organisms to move their bodies effortlessly in search of the things they need, crave, and desire. In humans, this may be one of the main brain systems that generate and sustain curiosity, even for intellectual pursuits. This system is obviously quite efficient at facilitating learning, especially mastering information about where material resources are situated and the best way to obtain them. It also helps assure that our bodies will work in smoothly patterned and effective ways in such quests.

When the mesolimbic pathway from the dopamine-producing VTA to the nucleus accumbens is stimulated, SEEKING behavior ensues. Panksepp writes: "For instance, stimulated rats move about excitedly, sniffing vigorously, pausing at times to investigate various nooks and crannies of their environment. If one presents the animal with a manipulandum, a lever that controls the onset of brain stimulation, it will readily learn to press the lever and will eagerly continue to 'self-stimulate' for extended periods, until physical exhaustion and collapse set in. The outward behavior of the animal commonly appears as if it is trying to get something behind the lever."

The mesolimbic pathway is activated trans-synaptically by normal rewards (food, water, copulation) but it can also be activated directly by the induced rewards of intravenous drugs or electrical or chemical brain stimulation (Wise). Wise RA. "Brain Reward Circuitry: Insights from Unsensed Incentives." Neuron. 2002; 36:229-340 The mesolimbic pathway is one of the dopaminergic pathways in the brain that modulates behavioral responses to rewarding stimuli. It originates in the VTA and connects to the limbic system via the nucleus accumbens, the amygdala, and the medial prefrontal cortex. A number of drugs are rewarding when they are injected into the nucleus accumbens and act as mesolimbic dopamine terminals, Lassen et al. "Brain Stimulation Reward is Integrated by a Network of Electrically Coupled GABA Neurons." Brain Research. 2007 ; 46-58. and the axons of the mesolimbic dopamine system have high thresholds for stimulation (Wise).