Abstract
Background: An inability to recall recent conversations often indicates impaired episodic memory retrieval. It may also reflect a failure of attentive registration of spoken sentences which leads to unsuccessful memory encoding. The hypothesis was that patients complaining of impaired memory would demonstrate impaired function of “multiple demand” (MD) brain regions, whose activation profile generalizes across cognitive domains, during speech registration in naturalistic listening conditions.Methods: Using functional MRI, brain activity was measured in 22 normal participants and 31 patients complaining of memory impairment, 21 of whom had possible or probable Alzheimer’s disease (AD). Participants heard a target speaker, either speaking alone or in the presence of distracting background speech, followed by a question to determine if the target speech had been registered.Results: Patients performed poorly at registering verbal information, which correlated with their scores on a screening test of cognitive impairment. Speech registration was associated with widely distributed activity in both auditory cortex and in MD cortex. Additional regions were most active when the target speech had to be separated from background speech. Activity in midline and lateral frontal MD cortex was reduced in the patients. A central cholinesterase inhibitor to increase brain acetylcholine levels in half the patients was not observed to alter brain activity or improve task performance at a second fMRI scan performed 6–11 weeks later. However, individual performances spontaneously fluctuated between the two scanning sessions, and these performance differences correlated with activity within a right hemisphere fronto-temporal system previously associated with sustained auditory attention.Conclusions: Midline and lateralized frontal regions that are engaged in task-dependent attention to, and registration of, verbal information are potential targets for transcranial brain stimulation to improve speech registration in neurodegenerative conditions.
Highlights
Impaired memory for recent conversations is a common symptom at the onset of Alzheimer’s disease (AD) but may accompany other neurological or psychiatric conditions
Patients complaining of memory impairment will often say that they find it more difficult to participate in conversations at social functions, in contrast to when they converse in a quiet environment. ‘‘Topdown’’ processes, which include selective attention and working memory, are necessary for segregating attended from unattended background speech (Bregman, 1990; Alain and Arnott, 2000; Darwin and Hukin, 2000a,b; Feng and Ratnam, 2000; Brungart, 2001; Conway et al, 2001; Carlyon, 2004; Cusack et al, 2004; Snyder and Alain, 2007; Darwin, 2008; Kerlin et al, 2010; Ding and Simon, 2012; Zion Golumbic et al, 2013; Zhang et al, 2016)
Prior to each session patients were classified based on the following clinical features; the Addenbrooke’s Cognitive Examination-Revised (ACE-R; Mioshi et al, 2006; Larner, 2007); the CANTAB Alzheimer’s Battery1, which includes Paired Associate Learning (PAL), a test sensitive to the presence of early dementia (Blackwell et al, 2004; Egerházi et al, 2007); the Geriatric Depression Rating Scale (GDRS; Yesavage et al, 1982); digit span; and the Test for Reception of Grammar (TROG-22) to assess spoken language comprehension
Summary
Impaired memory for recent conversations is a common symptom at the onset of Alzheimer’s disease (AD) but may accompany other neurological or psychiatric conditions. An initial impairment of episodic memory is soon followed by other cognitive deficits, affecting attention and executive functions (Perry and Hodges, 1999). Understanding how domain-general brain systems are impaired in patient populations during verbal registration could inform therapeutic strategies aimed at improving memory. An inability to recall recent conversations often indicates impaired episodic memory retrieval. It may reflect a failure of attentive registration of spoken sentences which leads to unsuccessful memory encoding. The hypothesis was that patients complaining of impaired memory would demonstrate impaired function of “multiple demand” (MD) brain regions, whose activation profile generalizes across cognitive domains, during speech registration in naturalistic listening conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
