Mind Language Disturbances and PET-Signs of Depression vs Alzheimer's Disease: Are There Any Common Patterns Identified?

ABSTRACT

BACKGROUND: There is a broad appreciation that a diagnosis of depression (D) in the elderly is a strong risk factor for incident dementia, particularly Alzheimer's disease (AD). Indeed, the two disorders might constitute a dyad, although their causal relationship is uncertain, given the likely bidirectional and compounding effects of social withdrawal and loss of previous activities, and the manifestation of language disturbances, cognitive dysfunction, and social disruption that are typical of both conditions. We argue that language declines in D and AD share common patterns and biological underpinnings, and that D/AD patients might benefit from intensive language remediation training aiming to improve the functioning of neural networks that are linked to similar cognitive impairments. METHODS: A literature search in PubMed database included topics of language disturbances, cognitive impairments, and molecular brain imaging by positron emission tomography (PET) to identify common patterns in D and AD regarding language decline and its neurobiological underpinnings. RESULTS: Language disturbances show a particular commonality in the two disorders, manifesting in simplified language and particular speech markers (e.g., lexical and semantic repetitions, arguably due to ruminations in D and memory deficits in AD). PET can reveal abnormal protein deposits that are practically diagnostic of AD, but cerebrometabolic deficits to PET with the glucose tracer FDG show a certain commonality in D and AD. Typical findings of hypometabolism in the frontal lobes doubtless underlie the executive function deficits, where frontal hypometabolism in prodromal D increases with AD progression. This may reflect overlapping changes in noradrenaline and other neurotransmitter (e.g. serotonin) changes. Cerebrometabolic deficits associated with language dysfunction may inform targeted language remediation treatments in the D/AD progression. CONCLUSIONS: Language remediation techniques targeting specific language disturbances might present an important complimentary treatment strategy along with an adjusted pharmacotherapy approach and standard psychosocial rehabilitation interventions. We see a need for investigations of language remediation informed by the overlapping pathologies and language disturbances in D and AD.