Fronto-parietal contributions to episodic retrieval—evidence from neurodegenerative disorders

Abstract

Converging evidence suggests a critical role for the parietal cortices in episodic memory retrieval. Here, we examined episodic memory performance in Corticobasal Syndrome (CBS), a rare neurodegenerative disorder presenting with early parietal atrophy in the context of variable medial temporal lobe damage. Forty-four CBS patients were contrasted with 29 typical Alzheimer's disease (AD), 29 healthy Controls, and 20 progressive supranuclear palsy patients presenting with brainstem atrophy as a disease control group. Participants completed standardized assessments of verbal episodic memory (learning, delayed recall, and recognition), and underwent structural and diffusion-weighted MRI. Selective delayed recall deficits were evident in the CBS group relative to Controls, at an intermediate level to the stark amnesia displayed by AD, and Control-level performance noted in progressive supranuclear palsy. Considerable variability within the CBS group on delayed recall performance led to the identification of memory-spared (N = 19) and memory-impaired (N = 25) subgroups. Whereas CBS-Spared showed no significant memory deficits, the CBS-Impaired subgroup were indistinguishable from typical AD across all episodic memory measures. Whole-brain voxel-based morphometry analyses implicated fronto-parietal and medial temporal regions in delayed recall performance in both the CBS-Impaired and AD groups. Furthermore, diffusion tensor imaging analyses revealed correlations between delayed recall performance and altered structural connectivity between fronto-parietal and frontotemporal regions in the CBS-Impaired group. Our findings underscore the importance of a distributed brain network including frontal, medial temporal, and parietal brain regions in supporting the capacity for successful episodic memory retrieval.

Do Patients with Progressive Supranuclear Palsy Have Episodic Memory Impairment? A Systematic Review

“…Interestingly, only Hall et al 26 had a separate group of PD with dementia (PDD), whose ADAS‐cog delayed recall did not differ from PSP.Taken together, the results are conflicting, but suggest a trend for similar performance of PSP and PD patients regarding episodic memory. PSP versus other forms of atypical parkinsonismAtypical parkinsonism includes different disorders such as PSP, corticobasal syndrome (CBS, formerly known as corticobasal degeneration [CBD]), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and others.Ten studies 15,19,20,24,27,28,34,41,43,46 examined PSP and CBS/CBD patients. The PSP group obtained better scores than CBS/CBD in all studies considering the ACE/ACE‐R memory 15,28,34,43 . No significant disparities between PSP and CBS/CBD were encountered for other verbal memory tests 15,20,24,27,41 .…”

“…Conflicting results, nevertheless, were noted in the ADAS‐cog delayed recall and in the DRS memory subscore, for which two studies 7,27 pointed out better performances of MSA patients and two other 15,26 no significant differences. PSP versus Huntington's disease (HD)Two articles 33,35 compared the episodic memory of PSP and HD patients. No significant differences between groups were found. PSP versus Alzheimer's disease (AD)Twelve studies 11,15,19,20,23,24,33–35,39,41,46 included patients with AD. Compared to AD, PSP individuals had a significantly better performance in verbal memory 15,23,24,33–35,39,41 .…”

“…Five studies showed significantly poorer performance of PSP patients on the Alzheimer's Disease Assessment Scale—cognitive subscale (ADAS‐cog) delayed recall, 26,27 DRS memory, 15,35 and Edinburgh Cognitive and Behavioral Amyotrophic Lateral Sclerosis Screening (ECAS)‐memory 22 . In the ACE/Addenbrooke's Cognitive Examination‐Revised (ACE‐R) memory, PSP patients also had worse results than controls 15,28,34,36 19,32,33,37,39 but others 18,23,24,30,41 did not find differences between groups.…”

“…No significant differences between groups were found. PSP versus Alzheimer's disease (AD)Twelve studies 11,15,19,20,23,24,33–35,39,41,46 included patients with AD. Compared to AD, PSP individuals had a significantly better performance in verbal memory 15,23,24,33–35,39,41 . Regarding visual episodic memory, results are discordant, as some found no difference between groups, 33,41 while others reported better performance in PSP patients 24,39 .…”

Evidence for a pervasive autobiographical memory impairment in Logopenic Progressive Aphasia: clinical and neural correlates

“…In this regard, it would be interesting to compare memory profiles in LPA with Corticobasal Syndrome and Posterior Cortical Atrophy – two syndromes that present with early motor and visual complaints, respectively, amidst primary parietal cortex degeneration. Notably, recent work has revealed the presence of marked episodic memory difficulties attributable, in part, to posterior parietal dysfunction in both Corticobasal Syndrome (Ramanan et al ., 2019b) and Posterior Cortical Atrophy (Ahmed et al ., 2018). Teasing apart different aspects of memory dysfunction in these populations may provide important clues regarding the functional role of discrete regions of the posterior neocortex.…”