Decision time: what makes a brain "tick"?

Looking at the light path left on a photo you can see that a driver chose at the very last moment to change its car direction. What is behind such a decision? Credit: Stanford University

(A) Illustration of task setup. Two targets were presented along with four virtual barriers and a frame. The monkey performed the task with a cursor projected above his fingertip. Targets were rewarded equally. The cursor left a white trail on the screen. (B) Task timeline. (C and D) The two families of mazes used: ‘T-maze’ (C) and ‘S-maze’ (D). Key barriers could take one of three positions, making each target easy, difficult, or blocked (shown here as shades of gray). Reaches for trials with ≥300 ms delay shown. Faded colors: reach trajectories on forced choice trials; saturated colors: reach trajectories on free choice trials. (E and F). Overt changes of mind on free-choice trials with no barrier changes. Credit: Matthew T Kaufman et al./eLife

Philosophers have been debating about the decision process of our "minds" for as long as we have historical records. Do we have free will or not? What is the physiological underpinning to our decisions?

In the last centuries a better understanding of the role of the brain in the decision process has emerged but the fog remains. It is not clear at all what are the processes that lead the brain to make up its mind!

Now scientists have the tools to move from philosophical speculation to scientific proof. Thanks to new technologies they can look inside a brain as it takes decision.  This involves placing sensors, electrodes, to pick up the firing of neurones and reconstructing the signalling that manifest itself as a decision.  
Because of the invasiveness of the technology required so far experiments have involved animals but the underlying assumption is that a brain is a bran, doesn't matter if it is a human brain or a different animal brain.

Recently, researchers at Stanford have experimented with monkeys that in a way reacts to external stimuli is very similar ways we are reacting to them, hence making the experiment and its conclusions easier to interpret.

A monkey is being shown with a maze on a screen and it is motivated to solve it by moving an object through corridors, around obstacles, till it reaches the arrival point. The monkey has to solve the maze finding the right path, and hence has to decide which way to push the object on the screen to find the path free of obstacles.  
This can be made as complex as needed, and it can require several decision points.

Researchers placed 192 electrodes on the motor and pre-motor cortex of the monkey and pick up the firing of neurones. First they start with very simple situations where there are basically two paths, and the decision is a on-off, left or right... Then they can make the maze harder to solve requiring more sequential decisions.

Experiments show that the decision process is organised in steps, with first a virtual representation (having no impact on actions) of what could happen if, and only after that the decision is taken to activate certain muscles that will turn the decision into an action.

Interestingly, it may take some time from the "thinking" of the scenario to the decision point and therefore the execution.

This is also giving new fuel, new perspectives, to the debate on free will. Apparently in a subconscious way, we model a spectrum of situations and then we decide to suppress most of them leaving only one to act upon.

Philosophical debate is not ending, of course, but science can provide a much better defined field onto which philosophy can play.

The experiments at Stanford are not aiming at helping the philosophical debate but at finding better way to interface prosthetics with thinking, to let disabled people control their prosthetic hand, as an example, in a seamless way, as we are doing with our real hand, just thinking about being thirsty and "deciding" to grab a glass and turn the faucet.

Author - Roberto Saracco


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