Decisions without frontal lobe activity


A paper by Tosoni, Galati, Romani, and Corbetta is reported in Science Daily (here). The research shows that once a task is learnt, the frontal lobes are not involved in decision making.

 

“In Nature Neuroscience, scientists report that a simple decision-making task does not involve the frontal lobes, where many of the higher aspects of human cognition, including self-awareness, are thought to originate. Instead, the regions that decide are the same brain regions that receive stimuli relevant to the decision and control the body’s response to it.

Other researchers had already demonstrated the same principle in primates. But many still assumed that the more complex human brain would have a more general decision-making module that involved the frontal lobe independently of the neural systems for perception and action.

…Maurizio Corbetta, M.D., the Norman J. Stupp Professor of Neurology. “We like to think of our decisions as willful acts, but that may be an illusion. Many decisions may be much more directly and automatically driven by what our brain is sensing.”

… trained volunteers to perform a task that involved discriminating between an image of a face and an image of a building. Varying degrees of noise obscured the image during the brief time it was visible. Volunteers were asked to indicate which type of image they believed they had seen by either moving their eyes in a particular direction if they had seen a face or pointing their hand in the same direction if they had seen a building.

“This decision is not automatic,” Corbetta says. “It requires both attention to the stimuli and control of the response.”

Researchers took functional magnetic resonance imaging scans of subjects’ brains as they performed the task… To help distinguish between the influx of sensory information and the decision to move the eye or hand, subjects had to wait for 10 seconds after seeing the image before indicating which type it was.

“This suggests that these regions in the parietal lobe processed all the sensory, decision and motor signals necessary to make and act on the decision,” Tosoni says. “In contrast, no area in the frontal lobe, thought to be involved in decision-making, significantly increased its activity at the time of decision.”

The training period that preceded the scans could have involved the frontal lobes, Corbetta notes. Those areas may have delegated responsibility for the decision to premotor brain regions as the volunteers learned the task. But once the task was learned, the frontal lobes were silent.

“Even for arbitrary and somehow complex visual decisions, it seems to be purely a matter of the amount of sensory information pushing the brain toward one choice or another ” he says.”

 

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