Apraxia, dyspraxia, oral-motor apraxia, Aphasia

[Concepts in Sensorimotor Research]

Pretty much every SLP I've been to over the years, has mentioned these terms. So what exactly are they. 

Apraxia, dyspraxia, and oral-motor apraxia are all related to deficits in motor planning and execution, but they differ in their specific manifestations and underlying neural mechanisms.

Apraxia

Apraxia is a motor planning challenges that results in difficulty carrying out intentional movements, despite intact strength and coordination. Individuals with apraxia may have difficulty with fine motor movements, such as buttoning a shirt or tying shoelaces, and gross motor movements, such as walking or jumping. They may also struggle with activities that require coordination of multiple body parts, such as playing sports or dancing.

The neural mechanisms of apraxia are complex and involve multiple brain regions, including the frontal, parietal, and temporal lobes, as well as subcortical structures such as the basal ganglia and cerebellum. Damage to these regions can disrupt the neural circuits involved in motor planning and execution, leading to apraxia. Molecular mechanisms involved in apraxia are still being studied, but some research has suggested that mutations in genes involved in synaptic function, such as the SHANK3 gene, may contribute to motor deficits in autism.

Dyspraxia

Dyspraxia is a broader term that refers to difficulty with motor planning and execution, and can include deficits in fine motor skills, gross motor skills, and oral-motor skills. This can lead to difficulties with activities such as handwriting, dressing, and sports.

Like apraxia, the neural mechanisms of dyspraxia involve multiple brain regions and pathways, including the cerebellum, basal ganglia, and motor cortex. Research has suggested that dyspraxia may be associated with reduced connectivity between these regions, as well as atypical patterns in the motor cortex and cerebellum.

Oral Motor Apraxia

Oral-motor apraxia specifically refers to difficulty planning and coordinating movements of the muscles in the mouth and throat, such as those involved in speech and swallowing which can result in difficulty with speaking and eating.

The neural mechanisms of oral-motor apraxia are thought to involve the same brain regions and pathways as apraxia and dyspraxia more generally, but with a focus on the motor control of the mouth and throat. Molecular mechanisms underlying oral-motor apraxia are not well understood, but research has suggested that genetic mutations associated with synaptic function and neuronal migration may play a role.

In the context of autism, these motor difficulties can contribute to challenges with social communication and interaction. For example, individuals with apraxia or dyspraxia may struggle with making eye contact, using gestures appropriately, or engaging in turn-taking during conversations. These difficulties may also affect self-care and activities of daily living.

Aphasia

Aphasia is a language disorder that can result from brain damage, typically to the left hemisphere. There are different types of aphasia, including expressive (Broca's) aphasia, receptive (Wernicke's) aphasia, and global aphasia, which involves both expressive and receptive deficits.

Behavioral phenotypes of aphasia can vary depending on the type and severity of the condition. Individuals with expressive aphasia may have difficulty producing speech or forming sentences, while those with receptive aphasia may struggle to understand spoken or written language. Individuals with global aphasia may experience both difficulties.

Neural mechanisms underlying aphasia involve damage to language-related areas in the brain, including the Broca's and Wernicke's areas, which are involved in language production and comprehension, respectively. Damage to the arcuate fasciculus, a bundle of fibers connecting these areas, can also contribute to language deficits.

Autistics can experience language difficulties, although these may not necessarily be classified as aphasia. Some studies have suggested that differences in brain connectivity and activation patterns may contribute to language impairments in autism (Geschwind and Levitt, 2007; Just et al., 2004).

References

• Mostofsky, S. H., Powell, S. K., Simmonds, D. J., Goldberg, M. C., Caffo, B., & Pekar, J. J. (2009). Decreased connectivity and cerebellar activity in autism during motor task performance. Brain, 132(9), 2413-2425.
• Roider, H. L., Pelphrey, K. A., & McDougle, C. J. (2013). Motor abnormalities in autism. In Handbook of autism and pervasive developmental disorders (pp. 791-811). Wiley.
• Tavano, A., Grasso, R., Gagliardi, C., Triulzi, F., Bresolin, N., & Fabbro, F. (2007). Disorders of cognitive and affective development in cerebellar malformations. Brain, 130(10), 2646-2660.
• Sztainberg, Y., Zoghbi, H. Y., & Pickrell, W. O. (2018). Motor impairment in Rett syndrome: Can we use it to inform treatment?. Developmental medicine and child neurology, 60(2), 132-138.
• Geschwind, D. H., & Levitt, P. (2007). Autism spectrum disorders: developmental disconnection syndromes. Current opinion in neurobiology, 17(1), 103-111.
• Just, M. A., Cherkassky, V. L., Keller, T. A., & Minshew, N. J. (2004). Cortical activation and synchronization during sentence comprehension in high-functioning autism: evidence of underconnectivity. Brain, 127(8), 1811-1821.