| Summary: | 博士 === 國立陽明大學 === 腦科學研究所 === 101 === Neuropsychological and neuroimaging research has proposed several theories/interpretations to account for the cognitive aging. However, these data were usually contaminated by behavioral artifacts or lack of motivation and concentration in the aged participants. To obtain a more genuine perceptual processing, we essentially examined the neuromagnetic activation to auditory and somatosensory sensory inputs in the pre-attentive state, which is independent of subjects' overt responses. More specifically, two major domains of aging-related neural representation were investigated: (1) repetition suppression (RS), reflecting a protective mechanism against flooding of the higher order centers with unnecessary information, and (2) magnetic mismatch negativity (MMNm), which is considered as a useful biomarker to study the auditory sensory memory and involuntary deviance detection. Up to date, the effects of aging on these two cortical operations remain inconclusive. Here, we used a whole-head 306-channel magnetoencephalography (MEG) to carefully examine the RS in auditory and somatosensory system, and MMNm to speech and non-speech sound discrimination in young and elderly adults, as well as patients with Alzheimer's disease (AD) in one study. Our results showed an aging-related deficiency in cortical inhibition to repetitive sensory inputs. Furthermore, the elderly demonstrated the shorter lifetime of sensory memory and less sensitivity to deviance detection. By recruiting AD patients, we also found a possible link between early-phase cortical inhibition and later-phase automatic novelty detection. In conclusion, our findings suggest a perceptual dysfunction in physiological and pathological aging.
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