Parkinson’s disease (PD) is more than a disorder of movement and motor function. Cognitive decline is also a component of PD for many people. Cognition is the umbrella term for thinking, knowing, remembering, problem-solving, and executive function. Memory is therefore a critical part of cognition, and memory problems are generally what people think of when they hear about cognitive decline. Research has shown that people with PD often experience memory problems. These memory problems can cause great distress for those with PD and their caregivers. Let’s take a closer look at the relationship between memory and PD.
Memory is the process of storing and remembering a wide variety of information. The hippocampus is believed to be the brain region responsible for memory processes. The hippocampal region is a small curved structure that lies deep within the brain’s temporal lobes (the parts of the brain on either side of the head, behind the ears). Over the years, research has shown that the hippocampus plays an important role in the three main stages of memory: formation, consolidation, and retrieval.
Memory formation is the process of learning new information. In other words, it is when someone “acquires” new information. New information first enters into a person’s short-term memory. Short-term memories then need to be “consolidated” before they can enter into long-term memory.
Memory consolidation is the process of turning short-term memories into long-term memories. The hippocampus plays a critical role in memory consolidation. Research shows that rehearsing (repeating information) helps to begin the consolidation processes, with sleep also playing an important role.
Memory is thought to exist across a network of regions in the brain called the neocortex. The hippocampus is needed to retrieve (or recall) many forms of memory across this network, particularly episodic memory. (Episodic memories are those a person has about specific events in their past. This is different from semantic memory, which is general facts a person knows about the world.) Once a memory is retrieved, it enters into an active state in which the person remembers the information. This is why damage to the hippocampus can potentially impair memory.
Research shows that PD causes problems with memory retrieval, and a comprehensive review describes problems with episodic memory in particular. The hippocampus often shrinks (a process called atrophy) in cases of PD. Because the hippocampus is particularly important for episodic memory, PD affects memory retrieval of episodic memories.
But the hippocampus is not the whole story in memory and PD. The brain’s cortex (particularly the frontal cortex) also plays a role in memory, and this structure is also affected in PD. The basal ganglia, a dopamine-rich center of the brain, is also important for memory and affected by PD. Dopamine, in general, is important for learning processes. Dopamine production is affected by PD since the main disease process in PD is the death of dopamine cells. Even beyond the hippocampus, changes in memory function and PD go hand in hand.
Some people with PD develop mild cognitive impairment (MCI) during the course of their disease. MCI is the state between normal cognitive aging and the more serious state of decline commonly known as dementia. Eventually, MCI can progress to Alzheimer’s disease. When PD-related MCI progresses to dementia, it is known as Parkinson’s disease dementia (PDD). PDD is sometimes confused with a similar condition called dementia with Lewy bodies, although some researchers believe that they are the same disease.
In one study, 21 percent of individuals with PD met criteria for MCI, while an additional 17 percent had dementia. It is because of this strong link between PD and cognitive impairment that some researchers call PD a “complex brain disease” rather than a motor disorder.
A class of medication called anticholinergics is occasionally used in early PD to reduce symptoms like tremors and bladder spasms. These drugs, however, are not recommended for use in older adults (people over 70) due to their many side effects, including adverse effects on memory.
Interestingly, the medication of choice for PD, levodopa, has been scientifically shown to actually increase memory encoding processes by increasing dopamine release.
Many members of MyParkinsonsTeam experience “brain fog,” a common and frustrating symptom of PD. “Ah! The memory thing!” exclaimed one member. “When I tell a story, in mid-sentence my head and my mouth stop working. I just freeze.” Another member agreed: “I have similar symptoms. It can be annoying and embarrassing, but I just try to get on with it!”
Older members question whether their memory loss is related to PD or aging itself. “You don’t have to have PD to have memory problems,” said one older member. “Many of us who are getting on in age have senior moments.”
Memory tips and tricks are popular topics in the community. Many members have partners who help fill their word gaps. Others use dictionary and thesaurus apps. Getting support from others with PD is a great way to learn strategies for managing memory function. “Don’t be embarrassed to let people know you have a memory problem, or let it stop you from socializing,” said one member. “Be honest and upfront about the new you — most people will understand.”
MyParkinsonsTeam is the social network for people with Parkinson’s disease and their loved ones. On MyParkinsonsTeam, members come together to ask questions, give advice, and share their stories with others who understand life with Parkinson’s disease.
Are you living with Parkinson’s disease? Have you experienced cognitive decline? Share your experience in the comments below, or start a conversation by posting on MyParkinsonsTeam.