Semantic profiles in mild cognitive impairment associated with Alzheimer?s and Parkinson?s diseases

Abstract

SummaryThe temporal and the prefrontal cortices have different roles in semantic information processing: the temporal lobe is where knowledge is stored (Graham and Hodges, 1997), whereas the prefrontal cortex is more specifically involved in executive aspects of semantic processing. Relatively little is known about the semantic profiles of mild cognitive impairment (MCI) in Alzheimer's disease (AD) and Parkinson's disease (PD). This observational study investigated naming and semantic questionnaire performances in three groups of subjects: 10 patients with the amnestic-type MCI prodrome of AD (aMCI), 10 patients with early-stage executive-type MCI in PD (MCI-PD), and 10 normal subjects. The MCI-PD subjects demonstrated inferior performances on a semantic questionnaire, whereas the aMCI group displayed modest difficulties in a naming task. These differences may be explained by topographical differences in pathological involvement. Since the frontal areas are more functionally impaired in PD, we hypothesize that the semantic deficit may be a consequence of a deficiency in control of semantic processing. On the other hand, the semantic deficit in aMCI may be related to a lexical-semantic storage dysfunction resulting from pathological involvement of the temporal lobe.

The Role of the Ventromedial Prefrontal Cortex and Basal Forebrain in Relational Memory and Inference

“…Likewise, data from a group of individuals diagnosed with aMCI also showed similar deficits in accuracy for the previously studied trials in the test phase of the pairwise condition compared to the setwise condition (Ryan et al, 2020). Although typically associated with episodic memory deficits, aMCI can also produce subtle disruptions on semantic tasks (Guidi, Paciaroni, Paolini, Scarpino, & Burn, 2015;Adlam, Bozeat, Arnold, Watson, & Hodges, 2006), which may be the result of atrophy of regions like the hippocampus and MTL cortex (Chang, Chiu, Chen, Cheng, & Hua, 2015;Barbeau et al, 2012). The parallel between the current mPFC cases and the aMCI group illustrates how diverse causes of impaired semantic processing may hinder the ability to parse preexperimental knowledge in a shifting versus stable context.…”

Functional Characterization of Atrophy Patterns Related to Cognitive Impairment

“…The left temporal seed on the other hand had a stronger functional connectivity with a fronto-temporal network, and behavioral decoding of the left temporal seed supported an emphasis on speech, semantic and syntax. Semantic deficiencies have been reported in MCI-patients (47) and can be observed in neurodegenerative dementias. In particular, the convergent co-activation with the left inferior frontal gyrus, both in taskdependent and task-independent analysis, suggests susceptibility in pathways playing a role in speech generation, and accords with observed vulnerability to atrophy of the inferior frontal gyrus in patients with Alzheimer's disease (48).…”

Semantic fluency deficits and associated brain activity in Parkinson’s disease with mild cognitive impairment

“…The involvement of the temporal lobe in semantic fluency may reflect its role in the storage of semantic memories, while the prefrontal cortex plays a role in the executive control of semantic processing, such as the retrieval and control of information (Noppeney et al, 2004 ). Therefore, semantic fluency impairment in PD can be attributed to deficits in semantic memory (Guidi et al, 2015 ), cognitive set-shifting (Henry & Crawford, 2004 ), and additional retrieval mechanisms (Obeso et al, 2012 ). Although it is suggested that posterior cortical and temporal lobe dysfunction are associated with semantic fluency deficits in PD (Williams-Gray et al, 2009 ), to date, there are no studies investigating specific brain regions constituting this link.…”