Abstract
Face recognition deficits are frequently reported in Alzheimer's disease (AD) and often attributed to memory impairment. However, it has been hypothesized that failure in identifying familiar people could also be due to deficits in higher-level perceptual processes, since there is evidence showing a reduced inversion effect for faces but not for cars in AD. To address the involvement of these higher processes, we investigated event-related potential (ERP) neural correlates of faces in a patient with AD showing a face recognition deficit. Eight healthy participants were tested as a control group. Participants performed different tasks following the stimulus presentation. In experiment 1, they should indicate whether the stimulus was either a face or a house or a scrambled image. In experiments 2 and 3, they should discriminate between upright and inverted faces (in experiment 2, stimuli were faces with neutral or fearful expressions, while in experiment 3, stimuli were famous or unfamiliar faces). Electrophysiological results reveal that the typical face-specific modulation of the N170 component, which is thought to reflect the structural encoding of faces, was not present in patient MCG, despite being affected by the emotional content of the face implicitly processed by MCG. Conversely, the N400 component, which is thought to reflect the recruitment of the memory trace of the face identity, was found to be implicitly modulated in MCG. These results may identify a possible role for gnosic processes in face recognition deficits in AD and suggest the importance of adopting an integrated approach to the AD diagnosis while considering electrophysiological markers.
Highlights
Alzheimer’s disease (AD) is a chronic neurodegenerative disease characterized at a neural level by neuronal atrophy and the presence of amyloid-β plaques and neurofibrillary tangles (Duyckaerts et al, 2009; Jack et al, 2018)
The high level of accuracy across conditions indicates that both controls and, more importantly, patient MCG could discriminate the category of the stimuli, being able to distinguish between meaningful and meaningless objects
The modulation of different event-related potentials (ERPs) components has been found to correlate with different aspects of face processing
Summary
Alzheimer’s disease (AD) is a chronic neurodegenerative disease characterized at a neural level by neuronal atrophy and the presence of amyloid-β plaques and neurofibrillary tangles (Duyckaerts et al, 2009; Jack et al, 2018). Problems with recognizing familiar faces have typically been attributed to memory problems, as the progression of the disease worsens (e.g., Becker et al, 1995; Hodges, 2006), impacting on more consolidated memories, such as the memory of familiar people. This is a logical conclusion as recognition implies preserved memory traces. The performance of patients with AD was impaired with inverted faces and with upright faces, and they suggested that there might be a specific impairment at building a coherent perceptual representation of individual faces in AD
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