Delusions of Control centre around an individual believing that their thoughts and/or actions are being controlled or influenced by outside forces. The ICD-10 has indicated that the common beliefs associated with delusions of control (thought broadcasting, thought insertion, and thought deletion) are individual symptoms of schizophrenia, but in this post I will be addressing the delusions as a single unit.
Those who experience these delusions may feel as though the people around them can hear what they think as they think it, that their movements are being controlled by an outside force, that an individual or organisation has put ideas into their head, or that they have removed thoughts. This can obviously become very distressing for the sufferer, who may not feel in control of their body or their mind, and is likely to isolate themselves from others in an attempt to lessen the effects of the delusion.
Researchers have identified a reduction of long-range connections between the frontal and posterior regions of the brain which may indicate a breakdown between areas processing sensory information and areas related to conscious awareness. This leads to an inability to consciously decide between action and inaction. The individual is then startled by their action, as they were not consciously aware of it, and therefore feel that the action was not their own (Frith, 2012).
The dissonance between knowing logically that the movement was intentional, while not experiencing that intention then leads to the belief that the individual is being controlled by an outside entity (Frith, 2005a), but given the same problem people without schizophrenia do not have the same belief. Similar experiences can be observed in people with lesions to their supplementary motor area, an area of the brain which has many functions one of which is controlling internally generated movements (Sala, 1998), but these individuals do not attribute their loss of agency to another being (Frith, 2005b).
Delusions of control, therefore, have two aspects to them: Firstly, individuals who experience them are not consciously aware of enacting specific movements or thoughts, and secondly they attribute these unconscious movements or thoughts to another entity. This assumption, that a malicious outside force is somehow interfering with the individual experiencing the delusion, is reminiscent of how some sufferers describe paranoid delusions. This may suggest that the two types of delusion are related in some way.
References
Frith, C. (2005a). The self in action: lessons from delusions of control.Consciousness and cognition, 14(4), 752-770.
Frith, C. (2005b). The neural basis of hallucinations and delusions. Comptes rendus biologies, 328(2), 169-175.
Frith, C. (2012). Explaining delusions of control: The comparator model 20 years on. Consciousness and Cognition, 21(1), 52-54.
Speculative Neuroscience 
Very interesting. My mom had paranoid schizophrenia and often talked about how someone was controlling her thoughts and even a few times driving the car when she was actually driving it.
I can’t imagine how frightening that must have been for her to go through, or how hard it must have been for you to witness. It’s not uncommon for people with schizophrenia to experience multiple kinds of delusions, but the similarities between delusions of control and paranoid delusions are really striking and can be very harmful. There still isn’t a lot of research into the causes of individual types of delusions, which is a terrible shame considering how many people are suffering.