Structural MRI Correlates of Episodic Memory Processes in Parkinson’s Disease Without Mild Cognitive Impairment

Abstract

Background Changes in episodic memory are common early in Parkinson’s disease (PD) and may be a risk factor for future cognitive decline. Although medial temporal lobe (MTL) memory and frontostriatal (FS) executive systems are thought to play different roles in distinct components of episodic memory impairment in PD, no study has investigated whether different aspects of memory functioning are differentially associated with MTL and FS volumes in nondemented patients without mild cognitive impairment (PD-woMCI). Objectives The present study investigated MRI markers of different facets of memory functioning in 48 PD-woMCI patients and 42 controls. Methods Regional volumes were measured in structures comprising the MTL and FS systems and then correlated with key indices of memory from the California Verbal Learning Test. Results In PD-woMCI patients, memory was impaired only for verbal learning, which was not associated with executive, attention/working memory, or visuospatial functioning. Despite an absence of cortical atrophy, smaller right MTL volumes in patients were associated with poorer verbal learning, long delayed free recall, long delayed cued recall, and recognition memory hits and false positives. Smaller right pars triangularis (inferior frontal) volumes were also associated with poorer long delayed cued recall and recognition memory hits. These relationships were not found in controls. Conclusions The findings indicate that MTL volumes are sensitive to subtle changes in almost all facets of memory in PD-woMCI, whereas FS volumes are sensitive only to memory performances in cued-testing formats.

Altered Functional Interactions of Inhibition Regions in Cognitively Normal Parkinson’s Disease

“…As for group differences in brain volume, only frontal lobe volume was significantly reduced in the PD group, contrary to other studies of PD without MCI ( Tessitore et al, 2012 ; Baggio et al, 2015 ; Pirogovsky-Turk et al, 2015 ; Harrington et al, 2017 ). Despite this finding, smaller parietal, temporal, and occipital volumes were associated with stronger right DLPFC-left middle/inferior temporal connectivity only in PD participants.…”

Spatial disorientation and executive dysfunction in elderly nondemented patients with Parkinson’s disease

“… 42 Results on RBMT novel task showed that PD patients perform poorer than controls, too. As commonly recognized, 43 PD patients demonstrate impaired free recall due to disruption of strategies for search and retrieve of information, presumably due to an executive dysfunction in this case. This finding is consistent with the fact that people with frontal lobe dysfunction report poor performances in recall tasks, especially in delayed ones after interfering activities.…”

Association of the serum microRNA-29 family with cognitive impairment in Parkinson's disease

“…In specific domains, we noted that the levels of the miR-29s family were all associated with the z-score of memory function. As PD-NC progresses to PDD, studies have shown that memory deficits become apparent, implicating a supervening dysfunction of temporal lobe storage mechanisms [ 18 ]. This association between miR-29s and memory function may result from the high expression of miR-29s in the central nervous system, particularly in neurons of the hippocampus [ 14 ].…”