From “Cinquante-Six” to “5quante-Six”: The origin of intrusion errors in a patient with probable alzheimer disease

The Impairment of Number Transcoding Abilities in Individuals with Amnestic Mild Cognitive Impairment and Alzheimer Disease: Associations With Attentional and Executive Functions

BACKGROUND

Studies have shown that number transcoding abilities (ie, translating numbers from one numerical code to another) are affected early in the development of Alzheimer disease (AD). However, no study has extensively explored how these abilities are affected in individuals with mild cognitive impairment (MCI).

OBJECTIVE

To determine the contribution that number transcoding tasks make to the identification of MCI, and to pinpoint the cognitive correlates of performance in these tasks.

METHODS

We compared the performance of 20 individuals with the amnestic subtype of MCI, eight individuals with AD, and 20 healthy controls on three number transcoding tasks.

RESULTS

The results confirmed the presence of number transcoding impairment in the individuals with AD. The individuals with MCI were found to be impaired in two of the transcoding tasks; these individuals produced perseverations of the input code-the most noteworthy error type in individuals with AD. In addition, the relationship between impairment in attentional and executive functions and impairment in number transcoding was supported by the correlational analyses.

CONCLUSIONS

This study confirmed that number transcoding abilities are impaired in individuals with MCI, although less severely than in individuals with AD. Our results provide evidence for the clinical value of including number transcoding tasks in the assessment of cognitive deficits associated with pathological aging.

The Progressive Acalculia Presentation of Parietal Variant Alzheimer's Disease

BACKGROUND

Many patients with early-onset Alzheimer's disease (EOAD; age of onset <65 years) have non-amnestic presentations involving language (logopenic primary progressive aphasia, lvPPA), visuospatial abilities (posterior cortical atrophy, PCA), and even asymmetric symptoms consistent with corticobasal syndrome (CBS). An inferior parietal lobule variant of EOAD commonly presents with progressive difficulty with calculations.

METHODS

We reviewed 276 EOAD patients for presentations with predominant acalculia. These patients were diagnosed with clinically probable Alzheimer's disease (AD) verified by positron emission tomography (PET) or cerebrospinal fluid amyloid-β or tau biomarkers.

RESULTS

We identified 18 (9M/9F) (6.5%) EOAD patients with progressive acalculia that did not meet most criteria for lvPPA, visual PCA, or CBS. Their ages of onset and presentation were 56.6 (5.0) and 59.4 (6.5), respectively. Their acalculia was consistent with a primary acalculia ("anarithmetia") not explained by language or visuospatial impairments. Many also had anomia (14/18), ideomotor apraxia (13/18), and the complete Gerstmann's syndrome (7/18). Visual analysis of their diverse magnetic resonance imaging disclosed biparietal atrophy, disproportionately worse on the left.

CONCLUSIONS

Primary acalculia may be the most common manifestation of an inferior parietal presentation of EOAD affecting the left intraparietal sulcus. This parietal variant also commonly involves progressive anomia, ideomotor apraxia, and other elements of Gerstmann's syndrome. The early recognition of patients with this variant, which is distinguishable from lvPPA, visual PCA, or CBS, would be facilitated by its recognition as a unique subtype of EOAD.

Numeracy skills in patients with degenerative disorders and focal brain lesions: a neuropsychological investigation

OBJECTIVE

To characterize the numerical profile of patients with acquired brain disorders.

METHOD

We investigated numeracy skills in 76 participants--40 healthy controls and 36 patients with neurodegenerative disorders (Alzheimer dementia, frontotemporal dementia, semantic dementia, progressive aphasia) and with focal brain lesions affecting parietal, frontal, and temporal areas as in herpes simplex encephalitis (HSE). All patients were tested with the same comprehensive battery of paper-and-pencil and computerized tasks assessing numerical abilities and calculation. Degenerative and HSE patients also performed nonnumerical semantic tasks.

RESULTS

Our results, based on nonparametric group statistics as well as on the analysis of individual patients, and all highly significant, show that: (a) all patients, including those with parietal lesions--a key brain area for numeracy processing--had intact processing of number quantity; (b) patients with impaired semantic knowledge had much better preserved numerical knowledge; and (c) most patients showed impaired calculation skills, with the exception of most semantic dementia and HSE patients.

CONCLUSION

Our results allow us, for the first time, to characterize the numeracy skills in patients with a variety of neurological conditions and to suggest that the pattern of numerical performance can vary considerably across different neurological populations. Moreover, the selective sparing of calculation skills in most semantic dementia and HSE suggest that numerical abilities are an independent component of the semantic system. Finally, our data suggest that, besides the parietal areas, other brain regions might be critical to the understanding and processing of numerical concepts.

Access to numerical information is dependent on the modality of stimulus presentation in mental addition: a combined ERP and behavioral study

We investigated whether the mental representation of numbers is abstract amodal or modality-dependent. Subjects verified simple additions. In an event-related potential (ERP) experiment, subjects added an Arabic digit (S2) to a preceding number (S1) offsetting 3 s before S2. S1 was either a visually shown Arabic digit, a written number word or an acoustically presented number word. In a behavioral experiment, we measured the speed of addition using a modified paradigm. In the ERPs to S2, the amplitude of the parietal N1, the fronto-central P2, and the late positivity between 320 and 460 ms were more positive and RTs were faster when S1 was a heard number word than when S1 was a written number word. ERP amplitudes and reaction times took intermediate positions between the other two conditions when S1 was an Arabic digit. Between the Arabic and heard number conditions, this so-called numeral modality effect (NME) was present at electrodes Pz, P4, P3 and Cz when number size was small, whereas it was significant over electrode C4 and P4 when number size was large. Our results suggest that numbers presented in different surface-formats have differential access to number representations. Conclusions for models of number processing are drawn and the possible role of parietal number representations is discussed. We replicated the N270 ERP component and elicited the ERP numerical distance effect in response to incongruent arithmetical results.