Functional MRI (fMRI) technology has recently enabled researchers to identify the pathways of two interrelated decision making processes involving a number of structures in the brain. The main pathway is complex and nuanced but slower. An alternative pathway, primarily involved in emergency decisions, trades subtlety for a nearly instant response. The two pathways and their interrelationship are outlined as follows:
The Thalamus screens incoming sensory data, continuously forwarding segregated data streams to specialized regions of the Sensory Cortex for processing while tagging any sudden aberrations in a data stream for immediate processing by the Amygdala.
The Sensory Cortex processes individual data streams received from the Thalamus to identify patterns, which are then reported to the Associative Cortex. Specialized regions of the Sensory Cortex process information on spatial awareness, touch, taste, smell, hearing, and vision.
The Unimodal Associative Cortex processes patterns as sensory experience. The Polymodal Associative Cortex processes patterns as concepts. Sub-regions of the Sensory Cortex filter data streams for words, shapes, faces, etc. The Associative Cortex creates a library of previously recognized patterns by sensitizing or suppressing neural relays. These stored patterns speed identification of previously encountered phenomena, but they can also impede the identification of unusual phenomena by tagging awkward information for deletion from Sensory Memory. The Associative Cortex sometimes also creates hallucinations and dreams by editing or transposing associations.
Sensory Memory—which has a capacity of up to 2 seconds—allows us to perceive discrete bits of information as a fluid stream by holding recent information in consciousness while receiving updates. Information deleted from Sensory Memory never reaches consciousness or becomes part of Long-term Memory.
The Hippocampus receives multiple data streams from the Associative Cortex, which it processes as clusters of patterns. These clusters of patterns are indexes used to identify or reconstruct previously encountered contexts or events and their associated emotional content. The Hippocampus can reconstitute previously established associations as memory (complete with sensory experience) based on a single recognized stimulus. The Hippocampus sometimes also creates false memories by editing or transposing associations.
The Prefrontal Cortex reconciles input from the Hippocampus and dictates a response. The initial response is invariably to focus attention on something significant or unusual for further evaluation. The Prefrontal Cortex then elicits additional related information from the Hippocampus and Associative Cortexes while suppressing information unrelated to an object of focus. The Prefrontal Cortex subsequently engages in a kind of modeling (related to dreaming) that compares the possible outcome of various scenarios suggested by experience—true dreams evidently have a ‘brainstorming’ function, generating novel scenarios that may prove useful later. Recent evidence suggests that the Prefrontal Cortex uses built-in algorithms such as the Nash equilibrium to select a course of action that reconciles often conflicting emotional charges associated with a given situation. The Prefrontal Cortex ultimately orchestrates a response by stimulating various organs of the Brain and, through these, the Body.
Working Memory—which has a capacity of up to 30 seconds or approximately 5-9 blocks of information—enables the Prefrontal Cortex to ‘juggle’ incoming information long enough to determine its relevance before either ignoring it or initiating the creation of Long-term Memory.
Long-term Memory—which takes up to three years to completely solidify—begins as a heightened sensitivity of neural synapses following stimulation. The neurons will begin to grow together if repeatedly stimulated as a result of recurring experiences, whether real or as elements of dreams. Sufficient stimulation causes the neurons to eventually fuse, and memory becomes hard-wired. Further repeated stimulation results in the suppression, or even elimination, of any neural relay that interferes with the efficiency of the fused synapse. As a result, highly intelligent people have fewer—but more highly integrated—neural networks. Moreover, continued stimulation prompts these neural networks to grow additional relays, thereby increasing their capacity over time.
Repeated stimulation cuases neurons to fuse together.
An alternative decision making process (involving only the Thalamus, the Amygdala, and the Hippocampus) trades subtlety for a nearly instant response. The alternative pathway leads directly from the Thalamus to the Amygdala, which monitors risk indicators stored in the nearby Hippocampus. If aberrant data from the Thalamus contains one of these risk indicators, the Amygdala prompts the Adrenal Gland to flood the body with adrenaline, initiating a ‘fight or flight’ response. Adrenaline has the additional effect of heightening attention to (and memory of) specific bits of information associated with risk.
A feedback loop is generated following any response (by either decision making process) as the Prefrontal Cortex evaluates the outcome of the previous cycle. Positive evaluations result in the release of dopamine from the Medial Forebrain Bundle, and negative evaluations result in the release of acetylcholine from the Periventricular System. Feelings of pleasure or anxiety result from the respective activation of these two pathways, and the Hippocampus establishes an association of this emotional content with a given context for future reference.
In addition to the functions outlined above, the Anterior Cingulate and the Nucleus Accumbens respectively monitor successive cycles for repeating or alternating patterns. A single repetition is sufficient to trigger a predictive impulse, and the adverse reaction to any broken pattern is directly proportional to the perceived stability of that pattern—just as a friend’s betrayal is more disturbing than the actions of a stranger.
