Dr Thomas Bak

Human Cognitive Neuroscience


Impairments of speech production are relatively common in Motor Neuron Disease (MND), often leading to difficulties in communication and causing significant distress to the patients and their carers. Until recently they tended to be attributed almost exclusively to dysarthria: a difficulty in producing the sounds of speech, caused by the weakness of muscles responsible for articulation. This assumption has been challenged by recent studies suggesting that the speech production deficit in MND can be caused by a variety of different factors, often co-occurring in the same patient, such as a difficulty planning the sequence of movements necessary for articulation (apraxia of speech), impairment in selection and perception of speech sounds (phonological deficits), generalised disorder of language functions (aphasia) or profound behavioural changes and loss of initiation (executive dysfunction) resulting in a loss of motivation to communicate.

The study examines in detail the relative contribution of these factors to speech production deficits in MND patients.  Its aim is, therefore, not only to document the frequency, severity and rate of progression of speech production deficits but to understand their exact nature. The study will examine patients in whom an initial cognitive screening test detected the presence of speech, language or communication deficits. Spontaneous speech will be recorded and will undergo a detailed analysis, including hitherto neglected aspects of speech such as prosody and intonation. The perception of sounds will be examined to elucidate whether the encountered difficulties are confined to speech production or extend into the domain of sound perception. Written language will be assessed in order to determine whether similar type of errors can also be detected in writing.

Finally, the impact of speech production deficits on patients and their carers will be assessed through questionnaires and structured interviews. The project will constitute the largest and most thorough study of this type ever conducted in MND patients.


A better understanding of the nature of speech production deficits in MND is obviously of paramount importance for acurate diagnosis, insightful counseling, effective support and developement and evaluation of potential treatments. It might help bridge the gap between the scientific research on the cognitive aspect of MND and the practical assessment of everyday functions in clinical setting.