Thinking Flexibility Impaired in Friedreich’s Ataxia Patients, Study Suggests

Thinking flexibility is impaired in people with Friedreich’s ataxia (FA), including the ability to predict and suppress a verbal response, according to new research. 

The study, “Measuring Inhibition and Cognitive Flexibility in Friedreich Ataxia,” was published in the journal The Cerebellum.

Interestingly, these impairments do not seem to be associated with the clinical characteristics of the disease such as age of onset, duration, genetic characteristics, and the scores that patients obtained in the Friedreich Ataxia Rating Scale, which measures disease severity.

These observations suggest that abnormalities in thinking flexibility may not be related to the disease in a straightforward way.

Previous work has shown that FA has a subtle impact on patients’ thinking ability. However, a clinically relevant tool to measure the changes in cognition in patients with Friedreich’s ataxia is still lacking. Such a tool would be invaluable in measuring patients’ response to drugs or other interventions in clinical trials.

Researchers led by Prof. Martin Delatycki at Murdoch Children’s Research Institute in Australia examined thinking flexibility and the ability to suppress a predictable response in 43 people with Friedreich’s ataxia and 42 healthy controls using three different tests. These were the Hayling Sentence Completion Test (HSCT),  the Trail Making Test (TMT), and the Stroop Test (ST). 

The HSCT is made of two parts, which assess verbal response initiation and response suppression. For both parts the researchers read 15 sentences out loud and asked the participants to either compete the sentence with a logical word (part A) or with the word that does not fit with the rest of the sentence (part B).

In the TMT, the participants were asked to draw a sequential line from numbers 1 to 25, and between sequential numbers and letters as quickly as possible.

The ST assesses a person’s ability to separate reading a color word from naming the actual color. Color names were written using wrong-colored letters. Participants were asked to name the color of the letters instead of reading the words.

Although there were no significant differences in the TMT and ST between people with Friedreich’s ataxia and healthy controls, the HSCT showed that the ability of FA patients to predict and suppress a response was significantly impaired.

The researchers concluded that HSCT may be a sensitive method of measuring thinking problems in FA patients and a useful test in clinical trials.

“Indicators of response suppression ability or cognitive flexibility were not significantly related to clinical characteristics of [Friedreich’s ataxia], suggesting that although significant, the impairment does not relate to the disease process in a simple way,” the authors concluded.