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Prepulse inhibition of acoustic startle response in mild cognitive impairment and mild dementia of Alzheimer type
Author(s) -
UEKI AKINORI,
GOTO KYOKO,
SATO NORIKO,
ISO HIROYUKI,
MORITA YOSHIO
Publication year - 2006
Publication title -
psychiatry and clinical neurosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.609
H-Index - 74
eISSN - 1440-1819
pISSN - 1323-1316
DOI - 10.1111/j.1440-1819.2006.01460.x
Subject(s) - prepulse inhibition , moro reflex , psychology , acoustic startle reflex , dementia , startle response , entorhinal cortex , neuroscience , audiology , reflex , gating , medicine , hippocampus , psychiatry , schizophrenia (object oriented programming) , disease
Amnestic mild cognitive impairment (MCI) describes the condition of memory‐impaired individuals who otherwise function well and do not meet the clinical criteria for dementia. Such individuals are considered to represent a transitional stage between normal aging and dementia of Alzheimer type (DAT). Neurobiologic changes in amnestic MCI, and their significance for psychophysiologic function, are poorly understood. In this study, the authors compared acoustic prepulse inhibition (PPI) between subjects with amnestic MCI and mild DAT to characterize sensorimotor gating. The acoustic startle reflex, which the authors measured using an accelerometer and electromyogram, involves whole‐body movement and eye blink in response to a sudden loud noise (115 dB). PPI is inhibition of this reflex by a softer noise (prepulse; 85 dB) preceding the startle stimulus by 30 ms. PPI was examined in 30 controls, 20 subjects with amnestic MCI, and 20 subjects with mild DAT. Neither amnestic MCI nor mild DAT affected startle movement amplitude. Subjects with amnestic MCI showed significantly enhanced PPI (gating facilitation), while subjects with mild DAT exhibited significantly less PPI than controls (gating deficit). This pattern of PPI changes suggests that neuropathologic changes in the limbic cortex, mainly the entorhinal cortex, at the earliest stage of DAT might be responsible for PPI abnormalities via disturbed regulation of the limbic cortico‐striato‐pallido‐pontine circuitry. Startle PPI changes could be used as a biologic marker for amnestic MCI and mild DAT.