Many of our work and leisure activities are accomplished by multitasking. For instance, answering email at your computer while talking to someone by phone, or talking by cell phone while riding a bike or walking the dog. How about standing at the stove sautéing vegetables while on the phone…reading a cookbook?
I often feel inadequate at multitasking. My strength has always been more depth rather than breadth of focus.
But a recently published study byA.I. Jack et al. in Neuroimage may bring redemption to those with more singular neural abilities. Jack’s paper entitled “fMRI reveals reciprocal inhibition between social and physical cognitive domains” describes competing neural networks, and provides convincing evidence that use of one of the networks not only precludes activation of the other, but actually suppresses the competing network.
First a bit about the networks involved. They are identified as the task positive network (TPN) and the default mode network (DMN). Many neuroscience researchers characterize the TPN as that used for external attention, and DMN as that used for internal attention (that directed toward self or internal states). Examples of internal attention are said to include episodic memory and future thinking. The DMN is also referred to as the task negative network.
When studying cognitive abilities via fMRI, researchers see that attention-requiring cognitive tasks activate brain regions in the TPN and at the same time, deactivate regions in the DMN. Furthermore, these two networks have been shown functionally to have a negative or anti-correlation when the brain is at rest. (More accurately, what is seen at rest is cycling between the two networks.) Thus evidence exists for a reciprocal inhibitory relationship between the TPN and DMN.
In their research, Jack et al. hypothesize that the reciprocal inhibitory relationship reflects two incompatible cognitive networks. They further believe that rather than the DMN being internally focused as previously believed, both networks or modes are directed towards understanding external, albeit different elements.
Jack et al. set about testing their hypothesis
“by identifying two types of problem-solving task which, on the basis of prior work, have been consistently associated with the task positive and task negative regions”.
These tasks were presented to the study subjects as questions : 1) requiring social cognition (reasoning about someone else’s mental state, for instance) and 2) requiring thought on the mechanical properties of inanimate objects. (Two such types of tasks are shown at the end of this article.)
The social and mechanical reasoning tasks were presented using both text and video clips. fMRI study sessions were kept at a consistent time, with subjects allowed a certain amount of time to read or see the task, and a consistent time length to provide a yes or no answer. Rest periods were worked into each study session as well, providing mental breaks between tasks.
The authors saw that the presentation modality did not affect outcomes. Whether tasks were presented as video or text, fMRI showed respondents with clear evidence of reciprocal cognitive suppression. The social tasks deactivated brain regions associated with mechanical reasoning, while the mechanical tasks deactivated the brain regions associated with social tasks.
The authors do not dispute a competition between internal and external attention, but note that each of the tasks used in this study were externally focused; each task involved perceptual attention and involved people and objects unknown to the study subjects.
The authors sought to use tasks that neatly recruited processes from just one neural domain. For instance they used social tasks that minimized any sort of analytical reasoning or controlled attention, to activate the DMN and not the TPN.
The mechanism of suppression of TPN over DMN and vice versa remains to be determined. Anatomical studies show no direct inhibitory links, but it is possible that the suppression is directed by another brain region.
Here is an example of the study tasks used:
A physics story:
A snowmobile is cruising over plains of white, hard packed snow. The driver steers the snowmobile in a straight line while at the same time pointing a flare gun straight into the air. The driver pulls the trigger, firing a bright flare into the air. Then, the driver immediately slams on his brakes. The flare flies through the air and then lands in the snow. Will the flare land in front of the snowmobile?
A social story:
Shannon spent all weekend studying for an exam, even though Saturday was her father’s birthday. Shannon decided that she must study, because if she did well she could get into medical school. The test went well, but Shannon feels guilty that she didn’t spend more time with her father. When Shannon gets her test back, she sees a ‘D’ written at the top of the paper, and in embarrassment quickly puts it in her bag. She didn’t notice that it is actually Jack’s test. Her real score is an ‘A’. Does Shannon think that she received an A on the exam?
Did you look at the image? What did you see first?
Jack, A., Dawson, A., Begany, K., Leckie, R., Barry, K., Ciccia, A., & Snyder, A. (2012). fMRI reveals reciprocal inhibition between social and physical cognitive domains NeuroImage DOI: 10.1016/j.neuroimage.2012.10.061
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