Language impairments in ALS/MND (Amyotrophic Lateral Sclerosis/Motor Neuron Disease)

Abstract

Paolo Bongioanni §, Giancarlo Buoiano C§, Marzia Magoni § § Neuroscience Dpt., Univ. Of Pisa, Italy c Corresponding author: Giancarlo Buoiano Via del Morello 8 Bargecchia I-55040 Corsanico (LU) email: giancarlo@neurolinguistics.0catch.com Language impairments in Amyotrophic Lateral Sclerosis/Motor Neuron Disease (ALS/MND) Abstract We review 6 papers on Motor Neuron Disease (MND) and language impairments. ALS/MND (Amyotrophic Lateral Sclerosis/MND) is an wide-ranging term used to cover several derangements of the motor neurons. ALS/MND brings to progressive degeneration of the motor neurons. The motor neurons control the muscles that consent us to move and act. Until some years ago, ALS/MND was thought not to affect language and higher-order cognitive functions, but at present it is acknowledged that about 3-5% of patients affected by ALS/MND show cognitive impairments. Up to date, it is not possible to establish whether this subgroup is affected by ALS/MND and Fronto-Temporal Dementia (FTD) or FTD/Aphasia syndrome or whether FTD/aphasia syndrome can be, in some cases, a consequence of ALS/MND. Furthermore, it is not clear whether MND/FTD syndrome brings to language breakdown or whether MND/Aphasia can be considered a self-standing syndrome. Lexical category-specific impairments affect more often than not verbs, while nouns appear to be by some means preserved. The verbs deficit is remarkable because it can place a new light on the link between actions, verbal and cognitive imagery, and ideomotor praxis. Language impairments detected in ALS/MND point largely to frontal and frontostriatal damages. Actually functional neuroimaging studies show reduced frontal activation. Alterations in Broca’s area, DorsoLateral PreFrontal Cortex (DLPFC) and fronto-striatal circuit have been all reported in ALS/MND: several functional studies link Broca’s area to syntactic processing and DLPFC to verbs production as well as language Short Term Memory (STM). A basic issue is the link between action and verbs and, as a result, between action syntax and speech syntax. This connection would be involved in the origin of language: it would be evolved passing from action to speech syntax. According to our point of view, verbs are pivotal in this system. In short, when actions are missing, verbs, ideomotor praxis and their neurocorrelates would deteriorate. A longitudinal study on the effect of massive motor derangement on the verb degeneration is at present carried out by our research group, so to date this is a working hypothesis waiting for further evidence. Keywords: ALS/MND, syntax, verbs, action, fronto-striatal circuit.