How Does Dementia Affect The Brain’s Frontal Lobes
The frontal lobes are like the command center of your brain. They control who you are as a person – your personality, your ability to make decisions, your ability to control your impulses, and your ability to speak and communicate with others. When dementia attacks the frontal lobes, it doesn’t just damage brain tissue. It fundamentally changes the person you are.
Understanding how dementia affects the frontal lobes requires us to look at what these lobes actually do and then see what happens when they start to deteriorate. The frontal lobes sit right behind your forehead and extend back toward the middle of your brain. They are responsible for executive function, which means planning, decision-making, impulse control, and personality expression. They also control speech production and social behavior. When dementia damages these areas, the results can be devastating and often misunderstood.
What Makes Frontal Lobe Dementia Different
Frontotemporal dementia, or FTD, is a specific type of dementia that primarily affects the frontal and temporal lobes of the brain [2]. This is fundamentally different from Alzheimer’s disease, which typically starts with memory loss. With FTD, memory often stays relatively intact in the early stages, but personality and behavior change dramatically [5]. This is why FTD is often missed or misdiagnosed for a long time. Doctors and family members are looking for memory problems, but instead they see a person acting like someone they don’t recognize.
The behavioral variant of FTD, often called bvFTD, is particularly striking in how it changes a person. Patients may suddenly become disinhibited, meaning they lose their social filter. They might make rude comments to strangers or engage in socially inappropriate behavior. They might steal things or act impulsively in ways that are completely out of character. This happens because the parts of the frontal lobe that normally keep our impulses in check are being destroyed [2].
How The Frontal Lobes Degenerate In FTD
The degeneration in behavioral variant FTD follows a somewhat predictable pattern. It typically begins in the orbitofrontal cortex and the ventromedial prefrontal cortex, which are areas deep within the frontal lobe that are crucial for decision-making and social behavior [2]. In the early stages, this is where you see the most dramatic changes in personality and behavior. As the disease progresses, the degeneration gradually expands to include the dorsolateral prefrontal cortex and eventually spreads to the temporal lobe [2].
Research using advanced brain imaging has shown that the damage in FTD is bilateral, meaning it affects both sides of the brain [3]. The atrophy, or shrinking of brain tissue, is particularly pronounced in the orbitofrontal cortex, the inferior frontal regions, and the dorsomedial and superior frontal areas [3]. What is particularly interesting is that microstructural changes in the brain tissue continue to progress even when the overall volume of the brain regions remains relatively stable [3]. This means that the damage is happening at a microscopic level, affecting the actual structure of the brain cells themselves, even when standard measurements might not show obvious shrinkage.
The Connection Between Brain Damage And Behavioral Changes
When the frontal lobes are damaged by dementia, the behavioral changes are not something the person is choosing to do. They are a direct result of brain tissue being destroyed. The ventromedial prefrontal cortex, which is one of the first areas affected in bvFTD, is a major center for social cognition and what researchers call “theory of mind” [2]. This is your ability to understand what other people are thinking and feeling and to adjust your behavior accordingly. When this area is damaged, people lose the ability to read social cues and control their behavior appropriately.
The executive dysfunction that comes with frontal lobe damage means that patients struggle with planning, organizing, and making decisions. They may become apathetic, meaning they lose motivation and drive. They may become compulsive, engaging in repetitive behaviors that they cannot control [7]. They may have difficulty with working memory, which is the ability to hold information in your mind temporarily while you work with it. All of these changes stem from the progressive destruction of frontal lobe tissue.
Language Problems From Frontal Lobe Damage
One of the most visible ways that frontal lobe dementia affects people is through language problems. Primary progressive aphasia, or PPA, is a language disorder that can occur with FTD [2]. There are different types of PPA, and they affect language in different ways depending on which parts of the frontal and temporal lobes are damaged.
Progressive nonfluent aphasia is one type where people know what they want to say, but they cannot get the words out smoothly. The connection between the thinking part of the brain and the speech production areas is broken. People might put words in the wrong order or speak very slowly and with great effort. They might eventually stop speaking altogether because it becomes too exhausting [5].
Semantic dementia is another language variant where people lose the meaning of words. They might not understand what words mean or might use words incorrectly. This happens when the temporal lobe areas that store word meanings are damaged.
The Physical Symptoms Of Frontal Lobe Dementia
Many people think of dementia as purely a thinking problem, but frontal lobe dementia often comes with physical symptoms as well. This is because the frontal lobes also control movement and motor function. Some patients with FTD develop movement disorders like progressive supranuclear palsy or corticobasal syndrome [5]. These conditions cause problems with eye movements, walking, balance, and muscle stiffness. Patients might have unexplained falls or difficulty with coordination.
The overlap between FTD and motor neuron disease is significant. Some patients with FTD develop symptoms of motor neuron disease, which affects the nerves that control muscles. This can lead to weakness, muscle wasting, and eventually difficulty with basic functions like swallowing and breathing.
Brain Imaging Findings In Frontal Lobe Dementia
When doctors use MRI scans to look at the brains of people with FTD, they see clear evidence of atrophy in the frontal and temporal lobes [6]. The amount of atrophy is related to how severe the symptoms are. Patients with the most severe clinical impairment show the most pronounced atrophy, particularly in the frontal lobe [1].
Beyond just looking at the size of brain regions, researchers are now using more sophisticated imaging techniques to detect changes at the microstructural level. These techniques can identify abnormalities in the texture and structure of brain tissue even before obvious shrinkage becomes visible [3]. This is important
