Cortical Thickness and Semantic Fluency in Alzheimer’s Disease and Mild Cognitive Impairment

Abstract

The hallmark of Alzheimer's disease (AD) is declarative memory loss, but deficits in semantic fluency are also observed. We assessed how semantic fluency relates to cortical atrophy to identify specific regions that play a role in the loss of access to semantic information. Whole-brain structural magnetic resonance imaging (MRI) data were analyzed from 9 Normal Control (NC)(M=76.7, SD=5.6), 40 Mild Cognitive Impairment (MCI) (M=74.4, SD=8.6), and 10 probable AD (M=72.4, SD=8.0) subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI). They all were administered the Category Fluency (CF) animals and vegetables tests. Poorer semantic fluency was associated with bilateral cortical atrophy of the inferior parietal lobule (Brodman areas (BA) 39 and 40) and BA 6, 8, and 9 in the frontal lobe, as well as BA 22 in the temporal lobe. More diffuse frontal associations were seen in the left hemisphere involving BA 9, 10, 32, 44, 45, and 46. Additional cortical atrophy was seen in the temporoparietal (BA 37) and the right parastriate (BA 19, 18) cortices. Associations were more diffuse for performance on vegetable fluency than animal fluency. The permutation-corrected map-wise significance for CF animals was pcorrected=0.01 for the left hemisphere, and pcorrected=0.06 for the right hemisphere. The permutation-corrected map-wise significance for CF vegetables was pcorrected=0.009 for the left hemisphere, and pcorrected=0.03 for the right hemisphere. These results demonstrate the profound effect of cortical atrophy on semantic fluency. Specifically, tapping into semantic knowledge involves the frontal lobe in addition to the language cortices of the temporoparietal region.

Altered Frontal Lateralization Underlies the Category Fluency Deficits in Older Adults with Mild Cognitive Impairment: A Near-Infrared Spectroscopy Study

“…Specifically, some MRI studies have reported a cortical atrophy in the (left) prefrontal cortices in individuals with amnestic or non-amnestic MCI (Pa et al, 2009 ; Wang et al, 2009 ; Chang et al, 2010 ; Ahn et al, 2011 ; Zhao et al, 2015 ). In addition, a link between poor semantic fluency performance and cortical atrophy of the lateral prefrontal regions (especially in the left hemisphere) has also been reported in these individuals (Ahn et al, 2011 ; Eastman et al, 2013 ; Clark et al, 2014 ). Furthermore, some fMRI studies have shown that these individuals exhibit abnormal frontal activations while performing various cognitive tasks, including episodic memory retrieval (Heun et al, 2007 ), semantic memory (Woodard et al, 2009 ), divided attention (Dannhauser et al, 2005 ), interference control (Kaufmann et al, 2008 ; Van Dam et al, 2013 ), and working memory (Alichniewicz et al, 2012 ; Papma et al, 2013 ; see Li et al, 2015 , for a recent meta-analysis of fMRI studies in MCI).…”

Multimodal Imaging of Brain Connectivity Using the MIBCA Toolbox: Preliminary Application to Alzheimer’s Disease

“…Interestingly, the GMV observed to be decreased bilaterally for the pars orbitalis may be related to known deficits in semantic fluency [39], [40].…”

Relationship between cognitive and sociodemographic aspects and verbal fluency of active elderly

“…The Verbal Fluency Test (VFT) 14 , widely used in Brazilian studies for the early identification of cognitive decline 15 , seeks to verify language, semantic memory and executive functions, evaluating the ability to search and retrieve data established in long-term memory. The VFT, which is based on categories, shows great sensitivity 16 in distinguishing individuals without cognitive alterations from those in early stages of AD 17 .…”