How Does Impaired Brain Activity Affect Cognitive Functions in Parkinson’s Patients?

New Delhi, May 5 (NationPress) A recent study conducted by researchers at the Indian Institute of Technology (IIT) Bombay has revealed how disrupted brain activity influences cognitive functions in individuals suffering from Parkinson’s disease.

The research specifically examined how altered reward processing in Parkinson’s patients contributes to their lack of motivation and impaired decision-making abilities.

Parkinson’s disease is a progressive neurodegenerative disorder characterized primarily by symptoms such as shaky limbs, muscle stiffness, and reduced movement speed. Additionally, some patients experience a diminished capacity for motivation or an inability to experience pleasure, which is linked to a deficiency in the dopamine hormone.

Dopamine, often referred to as the ‘feel-good’ hormone, is typically released during enjoyable activities or when receiving rewards.

The deficiency of dopamine in Parkinson’s patients alters brain activity and disrupts reward processing, which is the brain's mechanism for recognizing and responding to rewarding stimuli.

To explore reward processing in these individuals, the research team employed brain signal analysis.

The findings indicated that reward positivity was significantly diminished in Parkinson’s patients, suggesting their brains struggle to process rewards effectively. Reward positivity plays a vital role in cognitive functions such as attention, learning, and emotional responses.

Moreover, the administration of dopamine medication did not restore the reward positivity levels.

“Typically, the brain emits dopamine in brief bursts following a reward, but in Parkinson’s, these bursts are notably weaker. While dopamine medication can replenish dopamine levels, it does not replicate the natural burst-like signals. This could explain why motor symptoms improve, yet cognitive functions such as reward processing remain unaffected,” explained Prof. Nivethida Thirugnanasambandam, who led the study at the Human Motor Neurophysiology and Neuromodulation Lab in the Department of Biosciences and Bioengineering.

“Thus, additional treatment strategies may be necessary to address cognitive impairments in Parkinson’s,” she added.

The research team analyzed electroencephalography (EEG) data from 28 Parkinson’s patients and 28 healthy control subjects while performing a reward-based learning task.

EEG was recorded from the Parkinson’s patients before and after receiving dopamine medication (ON condition). Comparing these two states enabled researchers to assess the impact of dopamine medication on reward processing.

Additionally, the analysis revealed that Parkinson’s patients exhibited decreased theta-gamma synchronisation, which hampers communication between brain areas involved in reward processing and the execution of goal-directed behavior. This may explain the observed lack of motivation and decision-making difficulties among Parkinson’s patients, according to the researchers.

Theta-gamma coupling or synchronisation is essential for cognitive functions such as reward processing and goal-oriented behavior.

While dopamine medication could partially restore theta-gamma synchronisation, the researchers emphasized that this could serve as a potential biomarker for identifying reward mechanism impairments in individuals with Parkinson’s.