Working memory in posterior cortical atrophy

Cognitive rehabilitation in posterior cortical atrophy

Posterior cortical atrophy is an uncommon type of dementia often caused by Alzheimer's disease and characterised by progressive loss of visuospatial and perceptual abilities. Although there is no curative treatment, patients may benefit from a range of symptom-based techniques and strategies to address visuospatial deficits and apraxia, and to reduce disability. Specific techniques based on visual and tactile cues, adapted and assistive equipment, environmental modifications and skill training may help people with posterior cortical atrophy continue to carry on activities that are important to them. We share vignettes from patients treated in our clinics to illustrate the practical delivery and potential impact of these therapies.

Preserved musical working memory and absolute pitch in posterior cortical atrophy

Working memory for nonverbal auditory information is essential for everyday functioning but its cognitive organisation is not well understood. Here we addressed this issue in a musician, YA, with absolute pitch (AP, the uncommon ability to categorise and label individual musical pitches without an external reference) who developed posterior cortical atrophy. We assessed YA's AP ability and her working memory for pitch and rhythmic patterns using procedures modelled on a standard test of auditory verbal working memory (digit span), referenced to age-matched, cognitively-normal AP and non-AP possessing musicians. YA had retained AP and performed comparably to healthy older AP and non-AP musicians on all musical working memory tasks, despite impaired auditory verbal working memory. These findings suggest that the cognitive mechanisms for auditory verbal working memory, nonverbal (pitch and rhythm) working memory and AP are at least partly dissociable, and both musical working memory and AP can be spared despite posterior parietal degeneration.

Social cognition and behavioral changes in patients with posterior cortical atrophy

Posterior cortical atrophy (PCA) is a rare neurodegenerative condition characterized by progressive visual and visuospatial dysfunction. The consensus criteria state that patients should present "relatively spared behavior and personality" in early stages. However, limited research has focused on these symptoms in PCA. This study compared 157 patients with PCA in early stages of the disease with 352 healthy controls (HC), 202 typical AD (tAD), and 177 logopenic variant primary progressive aphasia (lvPPA) patients from the National Alzheimer's Coordinating Center (NACC) dataset. They were compared using clinician ratings of behavioral symptoms, informant- and clinician-filled questionnaires and patient-facing tests of behavior and social cognition. Results showed that PCA individuals exhibited many behavioral symptoms, the more frequently reported being anxiety, depression, apathy, and irritability. During cognitive testing, clinicians observed disorganized and reactive behaviors, but no insensitive behaviors. Informant reports indicated that PCA patients exhibited higher levels of inhibition and anxiety in response to stimuli associated with non-reward, novelty, and punishment. Social norms knowledge and empathy were overall preserved, although slight decreases in perspective-taking and socioemotional sensitivity were observed on informant-rated questionnaires. Except for more elevated neuropsychiatric symptoms in tAD, the three AD variants had similar profiles. Our findings provide insights into the social cognition and behavioral profiles of PCA, highlighting patterns of preservations and mild impairments, even in the early stages of the disease. These results contribute to a more complete understanding of non-visual symptoms in PCA and have implications for diagnostic and intervention strategies.

Primary and Secondary Progressive Aphasia in Posterior Cortical Atrophy

Background: Posterior cortical atrophy (PCA) is a clinico-radiological syndrome characterized by a progressive decline in visuospatial/visuoperceptual processing. PCA is accompanied by the impairment of other cognitive functions, including language abilities. Methods: The present study focused on three patients presenting with language complaints and a clinical profile that was compatible with PCA. In addition to neurological and neuroimaging examinations, they were assessed with comprehensive batteries of neuropsychological and neurolinguistic tests. Results: The general medical profile of the three patients is consistent with PCA, although they presented with confounding factors, making diagnosis less clear. The cognitive profile of the three patients was marked by Balint and Gerstmann’s syndromes as well as impairments affecting executive functions, short-term and working memory, visuospatial and visuoperceptual abilities, and sensorimotor execution abilities. Their language ability was characterized by word-finding difficulties and impairments of sentence comprehension, sentence repetition, verbal fluency, narrative speech, reading, and writing. Conclusions: This study confirmed that PCA is marked by visuospatial and visuoperceptual deficits and reported evidence of primary and secondary language impairments in the three patients. The similarities of some of their language impairments with those found in the logopenic variant of primary progressive aphasia is discussed from neurolinguistic and neuroanatomical points of view.

What's "up"? Impaired Spatial Preposition Processing in Posterior Cortical Atrophy

This study seeks to confirm whether lesions in posterior regions of the brain involved in visuo-spatial processing are of functional relevance to the processing of words with spatial meaning. We investigated whether patients with Posterior Cortical Atrophy (PCA), an atypical form of Alzheimer’s Disease which predominantly affects parieto-occipital brain regions, is associated with deficits in working memory for spatial prepositions. Case series of patients with PCA and matched healthy controls performed tests of immediate and delayed serial recall on words from three lexico-semantic word categories: number words (twelve), spatial prepositions (behind) and function words (e.g., shall). The three word categories were closely matched for a number of psycholinguistic and semantic variables including length, bi-/tri-gram frequency, word frequency, valence and arousal. Relative to controls, memory performance of PCA patients on short word lists was significantly impaired on spatial prepositions in the delayed serial recall task. These results suggest that lesions in posterior parieto-occipital regions specifically impair the processing of spatial prepositions. Our findings point to a pertinent role of posterior cortical regions in the semantic processing of words with spatial meaning and provide strong support for modality-specific semantic theories that recognize the necessary contributions of sensorimotor regions to conceptual semantic processing.

Neuropsychological deficits in Posterior Cortical Atrophy and typical Alzheimer's disease: A meta-analytic review

AIMS

To identify cognitive tests that best differentiate between Posterior Cortical Atrophy (PCA) and typical Alzheimer's Disease (tAD), as well as PCA and healthy control (HC) participants.

METHOD

Medline, PsycInfo and Web of Science were systematically searched using terms related to PCA, tAD, and cognitive testing. Seventeen studies were identified, including 441 PCA, 391 tAD, and 284 HC participants. Standardised effect sizes of mean scores were calculated to measure performance differences on cognitive tests for PCA versus tAD and PCA versus HC groups. Meta-analyses used a random effects model.

RESULTS

The most discriminating cognitive tests for PCA and tAD presentations were measures of visuospatial function and verbal memory. Large, significant effect sizes were produced for all measures of visuospatial function, most notably for Rey-Osterrieth Copy (Hedges' g = -2.79), VOSP Fragmented letters (Hedges' g = -1.73), VOSP Dot Counting (Hedges' g = -1.74), and VOSP Cube Analysis (Hedges' g = -1.98). For measures of verbal memory, the RAVLT delay and Digit Span Backwards produced significant medium effects (Hedges' g = .62 and -.56, respectively).

CONCLUSION

Establishing a common framework for testing individuals with PCA has important implications for diagnosis and treatment, and forms a practical objective for future research. Findings from this meta-analysis suggest that measures of visuospatial function and verbal memory would form an important part of this framework.

Impaired visual search in posterior cortical atrophy vs. typical Alzheimer's disease

BACKGROUND

Posterior cortical atrophy (PCA) is a neurocognitive disorder characterized by difficulty localizing in space. Recognizing PCA is important because it is usually missed early in its course and may result from a number of neurological disorders other than Alzheimer's disease (AD).

OBJECTIVE

This study aimed to clarify whether impaired visual search tasks of spatial localization distinguished patients with PCA from those with other more typical dementias as well as from healthy control (HC) subjects.

METHODS

Twelve patients meeting neuroimaging-supported Consensus Criteria for PCA, 12 comparably advanced patients with amnestic-predominant typical AD (tAD), and 24 HC participants were compared on tests of untimed and timed visual search, spatial neglect, mental rotation, environmental orientation, visuospatial construction, and face recognition.

RESULTS

Only abnormalities in untimed and timed visual search and environmental orientation distinguished the PCA patients from both the tAD group and the HC group without also distinguishing the tAD patients from HC's. The PCA patients also had a tendency to greater difficulty scanning left hemispace compared to HC's. Visuospatial constructions, although worse in PCA, and face recognition were impaired in both dementia groups.

CONCLUSIONS

These findings support the concept of PCA as a disorder of spatial processing and localization, indicating that visual search tasks are particularly sensitive and specific for detecting PCA and distinguishing it from more typical dementia syndromes.

Visuospatial working memory dysfunction from tapping span test as a diagnostic tool for patients with mild posterior cortical atrophy

Posterior cortical atrophy is a rare degenerative condition with prominent visuospatial dysfunction which commonly occurs between ages 50 and 65. A diagnosis of mild posterior cortical atrophy sometimes challenging and can be delayed because there are currently no established neuropsychological examination methods that can easily be used in clinical settings. In this study, we examined whether the tapping span test is a potential diagnostic tool for posterior cortical atrophy and what impairment the tapping span test is indicative of in this condition. Eight patients with mild posterior cortical atrophy were recruited. Age- and severity-matched individuals with amnesic Alzheimer's disease (n = 9) were also recruited as a control group. The participants were subjected to the tapping span test and several visuospatial working memory tests. The results of the tapping span and visuospatial working memory tests were worse for the posterior cortical atrophy group when compared with the control group. The results from the tapping span tests were strongly correlated with those from the visuospatial working memory tests. The tapping span test is a simple and potentially useful diagnostic tool for patients with mild posterior cortical atrophy, as it reflects visuospatial working memory function.

Benson's Disease or Posterior Cortical Atrophy, Revisited

BACKGROUND

D. Frank Benson and colleagues first described the clinical and neuropathological features of posterior cortical atrophy (PCA) from patients in the UCLA Neurobehavior Program.

OBJECTIVE

We reviewed the Program's subsequent clinical experience with PCA, and its potential for clarifying this relatively rare syndrome in comparison to the accumulated literature on PCA.

METHODS

Using the original criteria derived from this clinic, 65 patients with neuroimaging-supported PCA were diagnosed between 1995 and 2020.

RESULTS

On presentation, most had visual localization complaints and related visuospatial symptoms, but nearly half had memory complaints followed by symptoms of depression. Neurobehavioral testing showed predominant difficulty with visuospatial constructions, Gerstmann's syndrome, and Balint's syndrome, but also impaired memory and naming. On retrospective application of the current Consensus Criteria for PCA, 59 (91%) met PCA criteria with a modification allowing for "significantly greater visuospatial over memory and naming deficits." There were 37 deaths (56.9%) with the median overall survival of 10.3 years (95% CI: 9.6-13.6 years), consistent with a slow neurodegenerative disorder in most patients.

CONCLUSION

Together, these findings recommend modifying the PCA criteria for "relatively spared" memory, language, and behavior to include secondary memory and naming difficulty and depression, with increased emphasis on the presence of Gerstmann's and Balint's syndromes.

Establishing two principal dimensions of cognitive variation in logopenic progressive aphasia

Logopenic progressive aphasia is a neurodegenerative syndrome characterized by sentence repetition and naming difficulties arising from left-lateralized temporoparietal atrophy. Clinical descriptions of logopenic progressive aphasia largely concentrate on profiling language deficits, however, accumulating evidence points to the presence of cognitive deficits even on tasks with minimal language demands. Although non-linguistic cognitive deficits in logopenic progressive aphasia are thought to scale with disease severity, patients at discrete stages of language dysfunction display overlapping cognitive profiles, suggesting individual-level variation in cognitive performance, independent of primary language dysfunction. To address this issue, we used principal component analysis to decompose the individual-level variation in cognitive performance in 43 well-characterized logopenic progressive aphasia patients who underwent multi-domain neuropsychological assessments and structural neuroimaging. The principal component analysis solution revealed the presence of two, statistically independent factors, providing stable and clinically intuitive explanations for the majority of variance in cognitive performance in the syndrome. Factor 1 reflected 'speech production and verbal memory' deficits which typify logopenic progressive aphasia. Systematic variations were also confirmed on a second, orthogonal factor mainly comprising visuospatial and executive processes. Adopting a case-comparison approach, we further demonstrate that pairs of patients with comparable Factor 1 scores, regardless of their severity, diverge considerably on visuo-executive test performance, underscoring the inter-individual variability in cognitive profiles in comparably 'logopenic' patients. Whole-brain voxel-based morphometry analyses revealed that speech production and verbal memory factor scores correlated with left middle frontal gyrus, while visuospatial and executive factor scores were associated with grey matter intensity of right-lateralized temporoparietal, middle frontal regions and their underlying white matter connectivity. Importantly, logopenic progressive aphasia patients with poorer visuospatial and executive factor scores demonstrated greater right-lateralized temporoparietal and frontal atrophy. Our findings demonstrate the inherent variation in cognitive performance at an individual- and group-level in logopenic progressive aphasia, suggesting the presence of a genuine co-occurring cognitive impairment that is statistically independent of language function and disease severity.

Impairments of auditory scene analysis in posterior cortical atrophy

Although posterior cortical atrophy is often regarded as the canonical 'visual dementia', auditory symptoms may also be salient in this disorder. Patients often report particular difficulty hearing in busy environments; however, the core cognitive process-parsing of the auditory environment ('auditory scene analysis')-has been poorly characterized. In this cross-sectional study, we used customized perceptual tasks to assess two generic cognitive operations underpinning auditory scene analysis-sound source segregation and sound event grouping-in a cohort of 21 patients with posterior cortical atrophy, referenced to 15 healthy age-matched individuals and 21 patients with typical Alzheimer's disease. After adjusting for peripheral hearing function and performance on control tasks assessing perceptual and executive response demands, patients with posterior cortical atrophy performed significantly worse on both auditory scene analysis tasks relative to healthy controls and patients with typical Alzheimer's disease (all P < 0.05). Our findings provide further evidence of central auditory dysfunction in posterior cortical atrophy, with implications for our pathophysiological understanding of Alzheimer syndromes as well as clinical diagnosis and management.

The impact of white matter hyperintensities on speech perception

BACKGROUND

The presence of white matter hyperintensities (WMHs) can impact on normal brain function by altering normal signal transmission and determining different symptoms.

AIM

To evaluate the relationship between the presence of brain WMHs and the scores of speech perception test (SPT) in a sample of normal-hearing patients under 70 years of age.

MATERIAL AND METHOD

Prospective study. One hundred eleven patients underwent audiological screening with pure tone audiometry (PTA), tympanometry, speech perception testing (SPT), and brain magnetic resonance imaging (MRI). T2 sequences were analyzed to identify the presence of WMH that, if identified, were scored using the Fazekas score. Statistical multiple regression analysis was performed to understand the relationship between PTA and SPT score; the Pearson's and Spearman's tests were used to evaluate the correlation between Fazekas scores and SPT. Chi-square test was used to analyze the difference between gender.

RESULTS

The results of PTA were not predictive of the SPT score. A negative statistically significant correlation (Spearman's, p = 0.0001; Pearson's, p < 0.001) was identified between the Fazekas score and the results of SPT. No statistically significant differences were identified in the correlation of WMH and SPT between males and females.

CONCLUSION

Multiple WMHs in the brain can worsen word recognition in patients with normal auditory threshold; this may be related to the impact that these lesions have on the memory ability. Spread of lesions into the brain might reduce the brain capacity to remember words, despite the sound is correctly perceived by the ear.