[Concepts in Sensorimotor Research]
An Assignment on Speech and Language
The chapter on the Physiology of Speech and Language is frustratingly close to home for me as I am severely limited by both my expressive speech and almost very poor handwriting skills (along with other stuff). So I thought I would look at the concepts in this chapter in terms of a case-study of an impacted individual, namely me.
A Case Study in the Neural Basis of Communication Challenges
H is a young adult, who was diagnosed with Autism at age 3. His was a case of regressive Autism in which infants who seem to develop typically and meet developmental milestones, lose much of their language and other skills soon after the 18 month mark. H exhibits both speech and motor (writing) challenges. This report is an attempt to delineate H’s communication challenges along with the current scientific knowledge about their neural basis.
H’s consistent expressive speech ranges to a dozen or so few key phrases. His articulation may be hard to understand for people not familiar with him. He can repeat phrases and can sing, though his prosody and articulation are inconsistent. In receptive language skills, he is well above age cognitively. He was fortunate to learn typing on an AAC device as a mode of communication which has helped improve his quality of life. What is intriguing in this case is that the subject is very articulate when it comes to written communication, yet struggles with basic conversational speech. H’s communication challenges could broadly be placed under Apraxia of Speech diagnosis though there may be an overlap with other diagnoses related to communication. Since the loss of speech was at an early age, it is often referred to as Developmental Apraxia or Developmental Dyspraxia,.
Apraxia of Speech is an impaired ability to consistently produce and sequence the facial/oral muscles to produce the sounds and syllables required in spoken language. H has reported that he knows what he wants to say but he is not able to sequence that thought into actual speech at that particular moment. He also exhibits other oral-motor skill issues such as challenges in properly chewing food. Studies of brain lesions of patients with Apraxia of Speech provide evidence of impairment in the left precentral gyrus of the insular cortex. Other studies have confirmed the findings that “articulation activated the left insular insula.
Spontaneous talking requires information to flow from the sensory-motor association cortex into the posterior language area of Broca’s area. Then the act of talking itself requires some significant and rapid movement, sequencing and coordination of numerous facial and oral motor muscles (tongue, lips, jaw) along with the vocal chords. Broca’s area along with the inferior caudal left front lobe is implicated in, “memories of sequences of muscular movements used to articulate words,” (Carlson). In addition, Broca’s area is also directly connected to the part of the primary cortex that controls speech muscles. So Broca’s area seems to be a major player in H’s case.
H does not seem to exhibit significant challenges in the precursors to spoken language - such as perception of present and past events, memories (with some occasional deficits in short term memory), thoughts and the desire to communicate. Comprehension does not seem to be impacted, which seems to rule out Wernicke’s area as a source of concern. Wernicke’s area is however connected to Broca’s area through the arcuate fasciculus, also known as the Phonological Loop. This connection seems to play a role in the short term memory of speech sounds. H has exhibited difficulty in repeating back longer strings of words or forgetting the speech sounds of words he’d just read aloud.
There are elements of aphasia involved in that H exhibits anomia (groping for words) in addition to difficulty with articulation. H likens his word finding difficulty to a, “spotlight effect;” when placed in a situation where he is required to speak, adding to the “tongue-tied” result, which in his case is word-retrieval difficulty. If a beginning sound such as the sound “M” is given to him as a prompt, he may cycle through his mental dictionary of words starting with that sound. For example if therapist Michael (vs Michelle) is at the door, H may greet him as, “Hi Michelle,” and a few other names, before arriving at the correct, “Hi Michael.” The word retrieval difficulty ranges from mild to significant on any given day. H’s history has included EEG’s showing mild disturbances in the temporal lobe. Studies of brain lesions have linked the temporal lobe to the word-retrieval issues.
Studies have found parallels between spoken language and written language. For example H, exhibits difficulty in the prosody (rhythm, tone, emphasis) of spoken language which is believed to be controlled by neural connections in the right hemisphere. In his handwriting attempts too, there is disruption in the motor organization of the letters and spacing on the page, believed to be controlled by the dorsal parietal lobe and the premotor cortex. The act of handwriting activates the dorsal parietal lobe, the premotor cortex and the primary cortex. H exhibits poor motor memory of the motor sequences of space, size and spacing of letters that is required for handwriting. Both attempts at speech and attempts at handwriting therefore are labored and prone to errors. Communication via typing has somewhat simplified the motor aspects of forming letters for H as that requires keys to be pressed as compared to gripping a pen and drawing letters.
The overarching nature of the Autism Spectrum, with little knowledge of its physiological underpinnings means that there could be many other factors which play into the communication challenges. What is intriguing in H’s case (and frustrating for H himself) is the huge chasm between his motor ability (both speech and writing) and his comprehension and cognition skills. Basic communication, especially spontaneous speech, is however a critical aspect of daily human functioning and hence its lack greatly affects the individual’s quality of life. Our scientific understanding of neural workings, unfortunately have not yet reached a level where it translates into meaningful treatment manipulation.
Psych 22: Biological Psychology
