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In addition to Alzheimer's disease (AD), the hippocampus is now known to be affected in variants of frontotemporal degeneration (FTD). In semantic variant primary progressive aphasia (svPPA), characterized by language impairments, hippocampal atrophy is greater in the left hemisphere. Nonverbal impairments (e.g., visual object recognition) are prominent in the right temporal variant of FTD (rtvFTD), and hippocampal atrophy may be greater in the right hemisphere. In this study we examined the hypothesis that leftward hippocampal asymmetry (predicted in svPPA) would be associated with selective verbal memory impairments (with relative preservation of visual memory), while rightward asymmetry (predicted in rtvFTD) would be associated with the opposite pattern (greater visual memory impairment). In contrast, we predicted that controls and individuals in the amnestic mild cognitive impairment stage of AD (aMCI), both of whom were expected to show symmetrical hippocampal volumes, would show roughly equivalent scores in verbal and visual memory. Participants completed delayed recall tests with words and geometric shapes, and hippocampal volumes were assessed with MRI. The aMCI sample showed symmetrical hippocampal atrophy, and similar degree of verbal and visual memory impairment. The svPPA sample showed greater left hippocampal atrophy and verbal memory impairment, while rtvFTD showed greater right hippocampal atrophy and visual memory impairment. Greater asymmetry in hippocampal volumes was associated with larger differences between verbal and visual memory in the FTD samples. Unlike AD, asymmetry is a core feature of brain-memory relationships in temporal variants of FTD. [ABSTRACT FROM AUTHOR]

In 2022, Bruce Willis' family released a statement saying that he had been diagnosed with aphasia (an acquired language impairment) and would no longer be acting. Ten months later, the Willis family released another statement indicating that he received a more specific diagnosis of frontotemporal degeneration (FTD). This resulted in an explosion of media coverage, as prominent news outlets scrambled to produce stories describing FTD to a public largely unfamiliar with the disease. The quality of these stories varied widely, and in many cases the relationship between aphasia and FTD was misrepresented, as were basic descriptions and facts about FTD. FTD refers to a class of protein-misfolding diseases that are a common cause of aphasias due to neurodegeneration, or primary progressive aphasias (PPA). Rather than describing how FTD was discovered to be the underlying source of Mr. Willis' aphasia, many reports described his aphasia as "progressing into" FTD, implying they are two different disorders. Furthermore, these reports used the terminology of frontotemporal "dementia" rather than "degeneration", a term that invokes many stereotypes in the public imagination and may have contributed to misrepresentations in coverage. Instead of focusing on the language symptoms of PPA, reports often emphasized the personality and behavioral changes more closely associated with other variants of FTD. The substance of various facts, such as how common FTD is and how it can be treated, varied widely across reports. In sum, the media coverage of Mr. Willis' diagnosis reveals the extent to which the media and general public are uninformed about FTD and PPA. The remedy for this problem is to promote greater awareness of FTD, in both the public and the medical provider class. The Willis family's disclosure was a courageous act that helped bring much-needed attention to this disease. [ABSTRACT FROM AUTHOR]

Primary progressive aphasia (PPA) is a neurodegenerative syndrome that causes a gradual atrophy of the left hemisphere language network, leading to impairments of object naming (anomia) and word comprehension. In 33 human subjects with PPA, object naming and word comprehension were explored with N400 potentials elicited by picture-word or picture-picture matching tasks. Two mechanisms of impairment were identified. In one group of patients, where the object name could be recognized but not retrieved during verbal naming, N400s in picture-word trials were also abnormal, revealing an associative basis for retrieval anomia. In these patients, a putative prephonological signal (i.e., lemma) evoked by the object picture appears to have become too weak to elicit retrieval, but not necessarily too weak to support the informationally less taxing process of recognition. A second group of PPA patients showed more severe naming deficits--the object name was neither verbalized nor recognized. Furthermore, nouns of the same category (but not those of other object categories) could not be identified as mismatches. This blurring of intracategory but not intercategory differentiation of word meaning was correlated with anterior temporal atrophy, predominantly in the left hemisphere, especially along the superior temporal gyrus. Although not part of the classic language network, this area appears critical for proceeding from generic to specific levels of word comprehension and object naming. N400 abnormalities emerged for lexical (picture-word) but not nonverbal (picture-picture) associations, supporting a dual-route rather than amodal organization of object concepts. [ABSTRACT FROM AUTHOR]

Odors are surprisingly difficult to name, but the mechanism underlying this phenomenon is poorly understood. In experiments using event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), we investigated the physiological basis of odor naming with a paradigm where olfactory and visual object cues were followed by target words that either matched or mismatched the cue. We hypothesized that word processing would not only be affected by its semantic congruency with the preceding cue, but would also depend on the cue modality (olfactory or visual). Performance was slower and less precise when linking a word to its corresponding odor than to its picture. The ERP index of semantic incongruity (N400), reflected in the comparison of nonmatching versus matching target words, was more constrained to posterior electrode sites and lasted longer on odor-cue (vs picture-cue) trials. In parallel, fMRI cross-adaptation in the right orbitofrontal cortex (OFC) and the left anterior temporal lobe (ATL) was observed in response to words when preceded by matching olfactory cues, but not by matching visual cues. Time-series plots demonstrated increased fMRI activity in OFC and ATL at the onset of the odor cue itself, followed by response habituation after processing of a matching (vs nonmatching) target word, suggesting that predictive perceptual representations in these regions are already established before delivery and deliberation of the target word. Together, our findings underscore the modality-specific anatomy and physiology of object identification in the human brain., (Copyright © 2014 the authors 0270-6474/14/3414864-10$15.00/0.)