Neuromagnetic evidence of abnormal automatic inhibitory function in subjective memory complaint

Area of Science:

• Neuroscience
• Cognitive Science
• Neurology

Background:

• Subjective memory complaint (SMC) is a self-reported memory decline in individuals with normal objective cognitive performance.
• SMC is a potential risk factor for Alzheimer's disease (AD).
• Deficient sensory gating (SG), an inability to inhibit neural responses to repeated stimuli, is observed in AD but its presence in SMC is unknown.

Purpose of the Study:

• To investigate sensory gating (SG) function in cognitively normal elderly individuals with subjective memory complaints (SMC).
• To compare SG alterations in SMC subjects versus healthy controls (HC).
• To determine if SG deficits correlate with cognitive function or can distinguish SMC from HC.

Main Methods:

• Magnetoencephalography (MEG) recorded neural responses to an auditory paired-stimulus paradigm in 19 HC and 16 SMC subjects.
• Distributed source imaging (minimum norm estimate) analyzed SG using the M50 and M100 component amplitude ratios.
• Cortical SG ratios were measured to assess automatic inhibitory function.

Main Results:

• SMC subjects exhibited significantly increased M50 sensory gating (SG) ratios in the inferior parietal lobule (IPL) compared to HC.
• M50 SG ratios in the right IPL demonstrated discriminative ability between SMC and HC.
• No significant association was found between SG ratios and cognitive inhibitory control in either group.

Conclusions:

• Cognitively normal individuals with SMC show neurophysiological evidence of impaired automatic inhibitory function (SG) prior to objective cognitive decline.
• Altered brain function, detectable via neurophysiological recordings, occurs in SMC and may indicate early changes related to Alzheimer's disease risk.
• SG deficits in the IPL are a potential biomarker for identifying individuals with SMC and increased Alzheimer's disease risk.