How brain takes decisions

Washington, Nov 11: A new study has revealed that when faced with a choice, the brain retrieves specific traces of memories, rather than a generalized overview of past experiences, from its mental Rolodex.

The research led by Michael Mack from The University of Texas at Austin, is the first to combine computer simulations with brain-imaging data to compare two different types of decision-making models.

In one model- exemplar- a decision is framed around concrete traces of memories, while in the other model- prototype- the decision is based on a generalized overview of all memories lumped into a specific category.

Whether one model drives decisions more than the other has remained a matter of debate among scientists for more than three decades. But according to the findings, the exemplar model is more consistent with decision-making behaviour.

According to the findings, behavioural research alone cannot determine whether a subject uses the exemplar or prototype model to make decisions. With brain-imaging analysis, researchers found that the exemplar model accounted for the majority of participants’ decisions.

The results showed three different regions associated with the exemplar model were activated during the learning task: occipital (visual perception), parietal (sensory) and frontal cortex (attention).

While processing new information, the brain stores concrete traces of experiences, allowing it to make different kinds of decisions, such as categorization information (is that a dog?), identification (is that John’s dog?) and recall (when did I last see John’s dog?).

“We flexibly memorize our experiences, and this allows us to use these memories for different kinds of decisions. By storing concrete traces of our experiences, we can make decisions about different types of cars and even specific past experiences in our life with the same memories,” Mack said.

The study was published in journal Current Biology.