Brain and Behavior

Motor Behavior and Intentional Action

What fixed action patterns do we see in humans?

In humans, we see reflexes at birth (rooting, swimming, grasping, and sucking). With development, however, these basal ganglia-mediated reflexes get suppressed by the frontal lobe. For the most part, thoughtful, intentional behavior replaces automatic stimulus-response chains. In adulthood, fixed action patterns can re-emerge if there is damage to the frontal lobe. Frontal release signs, which are associated with frontal lobe damage, include several reflexes that we normally see only in early infancy. Certain psychiatric conditions may also reflect pathological activation of fixed action patterns. For example, obsessive compulsive disorder (OCD) has been linked to basal ganglia-frontal lobe circuits. It is characterized by repetitive, stereotyped, and senseless behaviors, such as compulsive hand-washing, tapping, straightening, or organizing behavior.


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