# The effect of levodopa on speech graphs in non-demented patients with multiple system atrophy and Parkinson’s disease

## TL;DR

This study uses speech graph analysis to compare brain network differences in multiple system atrophy and Parkinson’s disease, finding that levodopa affects speech patterns in MSA-P patients.

## Contribution

The study introduces graph theory to analyze speech patterns in neurodegenerative diseases and shows how levodopa affects speech topology in MSA-P patients.

## Key findings

- MSA-P patients had denser and smaller speech graphs compared to PD patients and healthy controls.
- Levodopa doses in MSA-P patients correlated with sparser and larger speech graphs.
- Speech graph analysis can help differentiate MSA-P from PD.

## Abstract

An objective topological analysis for any arbitrary network was provided by graph theory, which was implemented to reveal topological properties of brain networks in a wide range of neurodegenerative diseases.

To investigate the difference of the topology of speech graphs among parkinsonian-type multiple system atrophy patients (MSA-P), idiopathic Parkinson’s disease (PD) patients, and healthy controls (HC). To explore the effect of levodopa on the topology of speech graphs in MSA-P and PD patients.

We applied a graph analysis of topology of speech graphs in MSA-P patients (N = 39), idiopathic PD patients (N = 51), and HC (N = 51). All participants were assessed by a well-established semantic fluency test (animal). Participants’ verbal reactions were listed and represented as speech graphs with directionality.

MSA-P patients mentioned more about their memory and remaining time than PD patients (p < 0.001) and HC (p < 0.001). Moreover, MSA-P patients’ speech graphs exhibited fewer nodes (PD: p = 0.004; HC: p < 0.001), higher density (PD: p = 0.007; HC: p < 0.001), smaller diameter (PD: p = 0.004; HC: p < 0.001), and smaller average shortest path (PD: p = 0.002; HC: p < 0.001) than both PD patients and HC. Compared with PD patients and healthy adults, the MSA-P patients generated denser and smaller speech graphs. Importantly, in MSA-P, the positive correlations between levodopa equivalent daily dose and diameter (r = 0.39, p = 0.017) and average shortest path (r = 0.38, p = 0.017) were obtained, suggesting that higher levodopa doses were associated with producing sparser and larger speech graphs in MSA-P patients. However, there was no significant correlation between levodopa equivalent daily dose and graph indices in PD patients.

MSA-P patients’ speech graphs were denser and smaller than both PD patients and healthy adults. The graph analysis of semantic fluency can differentiate MSA-P from PD to some extent. Importantly, in MSA-P patients, the impaired speech topology can be partially restored by levodopa.