Washington: A new study has shown that people with frontotemporal dementia, one of the most common forms of the condition, are more likely to lose the ability to recognise negative emotions, such as anger, fear and disgust, than positive emotions such as happiness.
"All patients continue to recognise happiness, at least in the initial stages of the disease, even when recognition of other emotions is heavily impaired. There is something about a happy face that is different from the way other emotions are expressed," said lead author Dr Olivier Piguet at Neuroscience Research Australia.
Along with various other symptoms affecting behaviour and language, all people with frontotemporal dementia experience difficulty in recognising emotions. Up until now, however, it was not known whether the three subtypes of FTD have the same emotion-recognition deficits, and whether certain techniques could help overcome these deficits.
Dr Piguet`s team tested the ability of 41 people with FTD to recognise six basic facial emotions (anger, disgust, fear, happiness, sadness and surprise).
The team also performed a second test, using faces with exaggerated emotions, to determine whether more intensely expressed emotions would help with recognition. Of the three FTD subtypes, the researchers found that those people with the semantic dementia subtype were the most impaired when it came to recognising emotions.
"Semantic dementia patients were impaired across the board. Even when we increased the intensity of the emotions, it didn`t make any difference to their ability to recognize them. These patients probably have a disturbance in their core emotion recognition pathways," Dr Piguet said.
Patients with the progressive non-fluent aphasia and behavioural-variant FTD subtypes also had emotion-recognition deficits, particularly for angry and sad faces, but tended to improve if the emotions were made more obvious.
"Problems with emotion recognition had not been observed in patients with progressive non-fluent aphasia before, so this is a new finding.
"In both these types of patients, part of the problem is probably due to a deficit in attention, so perhaps they are not paying attention to the right places when looking at faces," Dr Piguet said.
The study has been published in the `Social Neuroscience` journal.