To get dressed requires a series of complex functions. You need to be aware of your situation, and that it will change, requiring you to put on clothes. You need to have the judgment to choose the correct clothes, and the initiative to want to put the clothes on. You also need to be able to make the right sequence of movements, including the five motor movements involved in buttoning and zipping.

A part from the judgment, awareness and initiative features, all parts of executive function Executive function
Includes the behaviors associated with judgment, agitation and social behavior - not memory. These behaviors are affected in all dementias, but especially in frontotemporal dementia., the recognition and coordination of movement is known as praxis, and its loss is called apraxia Apraxia
Apraxia is defined as the inability to carry out a previously learned motor activity, despite normal function of all the component parts (muscles, nerves, joints, etc.).  For example, experiencing difficulty dressing or using a knife and fork, are often clues that apraxia is present.. Apraxia is common in Alzheimer's disease Alzheimer's disease
A neurological disease that affects memory and behaviour. It is characterized by beta-amyloid plaques and neurofibrillary tangles in the brain. There is no known cause but genetics and lifestyle are thought to play a role., and reflects the disruption of the brain chemicals Brain chemicals
Chemicals released by the neurons in the brain in order to communicate. that make up motor sequences. The inability to get dressed is one form of apraxia.

Remember that dementia exists when cognitive impairment Cognitive impairment
Difficulty with mental abilities such as judgment, memory, learning, comprehension and reasoning. (e.g. problems with thinking, memory Memory
The ability to process information that requires attention, storage, and retrieval., judgment) is severe enough to interfere with function. Function can relate to complex activities, such as driving or complex hobbies, which are impaired first, but also to more basic activities, such as personal care, that become impaired later.

The capacity for function does not exist in one part of the brain, but rather requires the integration of several brain activities. Functions like dressing are basic and over learned, so that by the time they become affected, many brain areas are involved. Still, we have some hints based on patterns. For example, the fact that a person can still get dressed when prompted to do so suggests that the problem in that case is one of initiation, which is characteristically a frontal lobe Frontal lobe
The front part of the brain. It is important for the control of voluntary movement or activity, cognition and feelings. function. Later, as the disease is more widespread, the inability to carry out a motor function because the thinking parts of the brain are affected is known as apraxia. Characteristically, the brain's parietal lobes are also involved then.