An inability to correctly identify face-like objects and fewer brain signals associated with facial recognition were found in people with Huntington’s disease who had yet to show symptoms, suggesting these tests can be a marker of early disease progression, a study reports.
The study, “Impaired face-like object recognition in premanifest Huntington’s disease,” was published in the journal Cortex.
In Huntington’s disease (HD), the degeneration of nerve cells in the brain typically occurs in the basal ganglia, a region responsible for movement coordination, and in the cortex, which controls thought, behavior, and memory.
Recent studies have found additional nerve cell damage — early in Huntington’s progression — in the back of the brain, in areas responsible for vision, particularly an area called the fusiform gyrus, which is responsible for recognizing objects and faces.
Given that subtle changes in speech were recently identified in people with no obvious symptoms of Huntington’s — pre-symptomatic or premanifest disease — problems with facial recognition may also affect those in very early disease stages.
Identifying problems with facial recognition in pre-symptomatic patients may be a useful marker for early disease progression, providing valuable information to support diagnosis, clinical trials, and treatment.
Researchers based in Barcelona recorded the responses of pre-symptomatic Huntington’s patients after being presented with a series of pictures showing faces, face-like objects, and simple objects, and compared them to responses given by people without Huntington’s.
An electroencephalogram (EEG) was also used to record brain signals originating in the fusiform gyrus associated with object and face recognition. This neurophysiological signature related to face processing is known as the N170.
Their study recruited 32 people, 16 who were presymptomatic and carrying the huntingtin gene mutation, called preHD, and 16 who were relatives without the mutation, matched for age, gender and education. Tj
Participants first underwent a series of cognitive and behavioral assessments, including the Unified Huntington’s Disease Rating Scale (UHDRS), Problem Behaviors Assessment Scale for HD (PBA-s), and the Starkstein Apathy Scale (as apathy is a characteristic feature of HD).
Facial recognition involved looking at a series of 105 pictures on a computer screen, of which 35 were either faces, face-like objects, or simple objects. The pictures were shown at intervals of less than a second, and participants made one of two selections — “looks like a face” or “does not look like a face” — as fast and as accurately as possible.
Rates of correct and incorrect responses and reaction time were measured, in addition to the N170 brain signal, registered via electrodes placed about the head.
Analysis revealed that, among healthy relatives, responses to face-like objects were significantly slower than responses to faces alone. “Face-like object recognition is more demanding than simple object and face processing,” the researchers noted.
In contrast, those in the preHD group were significantly slower in responding to pictures with either objects or face-like objects compared to only faces.
No differences in the number of correct or incorrect responses for objects and faces was recorded between the two groups, but the ability to correctly identify face-like objects was significantly worse in preHD patients. Up to 30% of the face-like images were classified as objects by these people.
This represented “a dramatic increase in the number and rate of error responses,” the team wrote.
A statistical analysis also found a strong link between the total number of errors in face-like objects and the severity of apathy as determined by the Starkstein Apathy Scale.
The EEG analysis found those in the preHD group had a significant reduction in the N170 signal when shown faces or face-like objects compared to the group of relatives. A decrease in the N170 signal was also significantly linked to the severity of apathy and overall cognitive abilities.
“In conclusion, premanifest [pre-symptomatic] HD participants have a specific [visual perception] deficit that selectively disrupts the perception of face-like objects as early as 15 years before estimated time to diagnosis,” the researchers wrote. “This deficit can be measured as an increased number of errors in the recognition of face-like object stimulus and as an abolition of the N170 component elicited by face-like objects.”
They added: “The occurrence of selective impairment in face-like object processing in the clinical group emphasizes the need to develop specific instruments to capture early changes in premanifest HD.”
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