Bootstrapping conceptual deduction using physical connection: rethinking frontal cortex

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The age at which infants can demonstrate the ability to deduce abstract rules can be reduced by more than half, from 21 months to 9 months. The key is to introduce a physical connection between the items to be conceptually related. I argue here that making the same change in how items are presented might also help some preschoolers with learning delays, especially some children with autism. I also suggest that the roles of premotor and ventrolateral prefrontal cortices in deducing abstract rules might have been misinterpreted behaviorally and anatomically. The crucial brain region may be the periarcuate, which partially overlaps both premotor and lateral prefrontal cortex. The cognitive ability made possible by this region might be something far more elementary than previously considered: the ability to perceive conceptual connections in the absence of physical connection.

Introduction

Elegant evidence suggests a crucial role for premotor cortex and inferior (ventrolateral) prefrontal cortex in encoding abstract rules 1, 2, 3, 4. The research community has been captivated by evidence that within anterior premotor cortex and perhaps the rear portion of inferior prefrontal cortex there are ‘mirror neurons’ – neurons that fire when the subject performs a particular action or observes someone else performing that action; 5, 6, 7, 8, 9. I propose that a focus on premotor or ventrolateral (inferior) prefrontal cortex misses the mark, as does a focus on rule learning or even mirror neurons – I propose: (i) that we recognize a coherent region that spans anterior premotor cortex and posterior lateral prefrontal cortex: the periarcuate region (see Box 1), and (ii) that although there is evidence that this region is crucial for deducing abstract rules and that it may contain mirror neurons, the reason it is crucial for those functions is because it subserves a more elementary and basic function – that of being able to grasp how physically separate things might be related (i.e. conceptually connected despite their physical independence).

In this article, I propose that infants in the first year of life, and some preschoolers with developmental delays, can deduce abstract, relational rules long thought beyond their ability. They have appeared unable to do this because behavioral methods have not allowed them to demonstrate this ability. I suggest that instead of having problems deducing abstract concepts, they have a more elementary problem – perceiving conceptual connections between physically unconnected things. If items that infants are meant to relate conceptually are presented physically connected, infants of only 9–12 months can grasp abstract, conceptual relations. I predict that this would also be true for some children with developmental disorders, especially some children with autism.

Section snippets

Evidence that infants can deduce abstract relations

Children cannot deduce the abstract rule that underlies the ‘delayed nonmatching to sample’ (DNMS) task until they are almost 2 years old 1, 2, 3, 4, irrespective of whether they are tested only once [1] or daily from 12 months onwards [2]. On each trial a sample object is presented and the child picks it up to reveal a small reward underneath. After a delay, the sample and a novel object are presented. The reward is now under the novel object. No stimulus is used on more than one trial and the

A role for physical connection in helping monkeys and children understand conceptual connections

Physical connection has been shown to make a huge difference to non-human primates in their learning of abstract relations. Fifty years ago, Jarvik [18] asked why it takes chimpanzees hundreds of trials to learn a simple color discrimination (e.g. where a blue plaque always covers one foodwell and a red plaque another, the position of the plaques varies randomly over trials, but food is always only under the red plaque). Jarvik tried a variation: he attached the peanut reward to the underside

Role of the periarcuate region: grasping conceptual connections without physical connection

Monkeys with lesions of ventrolateral prefrontal cortex, if and only if the lesions invade the periarcuate region, show similar performance on DNMS to human infants. They have great difficulty deducing the nonmatching rule even with no delay at all, but once they have grasped the rule they perform well even at long delays 12, 13, 14, 15. They take over 10 times as long to pass the DNMS test post-operatively as they did pre-operatively, but show no evidence of a delay-dependent deficit once they

How should we parcellate the frontal lobe?

In the 1970s and 1980s several behavioral neuroscientists investigated which cognitive functions required the periarcuate region in monkeys (e.g. 28, 29, 30, 31, 32, 33). This line of research lost favor, however, because it was considered more elegant to focus on a defined neural region than on tissue partly in one anatomically defined region and partly in another. However, I suggest that function might not necessarily respect regional borders assigned on the basis of common neuroanatomy, or

Rule learning: learning conditional associations or abstract rules

Research in the 1970s and 1980s 28, 29, 30, 31, 32, 33 documented in many replications and permutations that lesions of the periarcuate, but not of dorsolateral prefrontal cortex, produce deficits in learning conditional associations (in the presence of one cue, Response X is correct but in the presence of another cue, Response Y is correct). The presence of a delay is not necessary to elicit a deficit after lesions invading the periarcuate. Petrides demonstrated similar deficits in learning

Conclusion

The hypothesis advanced here is that infants of less than one year of age, and some preschoolers with developmental delays, especially such children with autism, would be able to grasp abstract relations and conditional associations if the objects to be conceptually connected are presented physically connected. Most behavioral training with children with developmental delays has not considered whether physical connection matters. Making such a simple change in training methods could enable

Acknowledgements

The writing of this paper was aided by a grant from NIDA (R01 #DA19685). The author would like to thank Rebecca Landa for helping to educate her about autism, and Marcel Brass, Uta Frith, Jerry Kagan, and especially Mike Petrides for very helpful comments on an earlier draft of this manuscript.

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