MU

Chapter 1-7 Neuroanatomy and Language — Key Terms

Orientation, imaging orientation, and planes

  • Rationale for good grasp of orientation: everyone will have access to imaging that identifies where a pathology is in the brain. Imaging is essential for understanding patient pathology (e.g., traumatic brain injury) in clinical settings.
  • Key planes to know:
    • Transverse (axial) plane – horizontal slice.
    • Sagittal plane – vertical slice from left to right.
    • Midsagittal plane – a sagittal plane exactly down the midline.
  • Nursing/OT/PT alignment with orientation terms: terms like lateral are meaningful only relative to a reference (e.g., relative to the brain). Always specify the reference point in the brain when using orientation terms.
  • Takeaway: become comfortable viewing images in these planes so you can localize pathology with brain anatomy.

Review of brain localization and clinical relevance

  • Part of the semester is a review of lobes and functions to anchor pathology understanding.
  • Localization matters for different disorders:
    • Traumatic brain injury (TBI) – localization of injury helps predict deficits.
    • Huntington's disease – more subcortical involvement.
  • The goal of this section: be able to map observed deficits to damaged brain regions and anticipate clinical manifestations.

Memory and language processing: real-world examples

  • Grace vignette: multimodal memory issues observed during a cognitive task (writing a phone number from a magazine). She could write most digits but not all; memory was fragmented and difficult to recall consistently.
    • Illustrates that memory can appear discrete and fragmented rather than as a single continuous store, and that memory affects day-to-day tasks differently for each person.
  • This leads into the language output discussion: expressive vs receptive language.

Expressive vs receptive language: localization and implications

  • Expressive language (language output) – where it is typically disrupted when language is produced.
    • Example: trouble finding the right word; can use gestures or pointing to convey meaning even when words fail.
    • If the language-dominant area sustaining expression is damaged (e.g., Broca’s area via stroke), speech production is effortful and word finding is impaired.
  • Receptive language (language comprehension) – listening/reading understanding.
    • Example: Wernicke’s area dysfunction leads to fluent speech with poor comprehension and word meaning; interpretation can be impaired even though speech sounds normal.
  • The two areas communicate with each other; language becomes a network problem, not a single isolated “box.”
  • Clinical note: many language disorders are chronic; full restoration to pre-morbidity levels is uncommon. Intervention often focuses on compensatory strategies and alternative communication.

Case examples illustrating aphasia types and consequences

  • Byron: Wernicke’s aphasia (receptive language impairment) with preserved fluency and prosody but impaired comprehension.
    • He can speak fluently with good prosody, but patients often misunderstand him due to impaired semantic processing.
    • Prosody and intonation may remain intact even when word meaning is disrupted.
  • Grace: expressive language challenges with some preserved comprehension; difficulty retrieving words and assembling them into coherent speech.
  • Sign language considerations: three studies on aphasia and sign language (last study cited was 1982). Current neuroanatomical theory suggests sign language aphasia presents similarly to spoken-language aphasia if the lesion is in analogous language areas (e.g., Broca’s vs Wernicke’s). This has implications for sign language users who experience stroke, and underscores the need to tailor assessments and therapy to modality of communication.
  • Takeaway: aphasia is not purely about “language,” but about the brain’s language network, which can involve speech, sign language, gesture, and multimodal communication.

Speech-language pathology and audiology: roles and collaboration

  • Speech pathologists focus on locating where language processes are disrupted and how to support language expression or comprehension.
  • Audiologists focus on auditory comprehension and the integrity of hearing, especially after stroke when language impairment complicates assessment.
  • Key audiology challenges:
    • If language output is impaired, determining what the patient understands can be difficult.
    • Full audiologic assessment may require multimodal communication (visuals, gestures, simplified instructions).
  • Practical approach: combine auditory tests with visual supports to ensure valid assessments of comprehension and hearing.
  • Interprofessional practice: emphasize collaboration across speech pathology, audiology, neuropsychology, and rehabilitation services to optimize patient outcomes.

Real-world interprofessional and patient communication

  • Inpatient rehab and interprofessional education: a well-known coma video illustrates how misattribution of a patient’s deficits can occur if teams don’t communicate effectively.
  • The video underscores the importance of understanding different professional roles and the language each uses when assessing patients.

Brain anatomy basics: neurons, glia, and neurocommunication

  • Cortical vs subcortical distinction:
    • Cortex (cerebral cortex) – outer layer of the brain involved in higher-level processing (planning, perception, language, conscious thought).
    • Cortex is part of the mammalian brain; brainstem and autonomic functions are more associated with the reptilian brain components.
  • Neurons – core signaling cells of the CNS; they communicate via electrical and chemical signals.
    • Core parts of a neuron include:
    • Dendrites: receive signals from other neurons.
    • Soma (cell body): processes incoming signals, integrates information, and decides whether to propagate a signal.
    • Axon: conducts the electrical signal away from the cell body toward the axon terminals.
    • Axon terminals: release neurotransmitters to the next neuron's dendrites.
    • The synapse is the contact point where the axon terminal communicates with the next neuron's dendrite.
  • Glial cells – the helper cells of the CNS; provide structure, support, and cleanup (e.g., clearing excess neurotransmitters and fluids).
    • Glial cells outnumber neurons by roughly a 9:1 ratio in the CNS, i.e., approximately 9:1.
  • Myelin – a fatty substance that wraps some axons to speed up electrical conduction. Myelinated fibers conduct faster than unmyelinated ones.
    • A helpful analogy used in class: myelin is like the airport moving walkways that speed signal transmission; nodes along the myelin sheath serve as fast-conduction points.
  • Gray matter vs white matter:
    • Gray matter contains neuron cell bodies and is the site of information processing.
    • White matter contains myelinated axons and serves as the communication highways between different gray matter regions.
  • Action potentials – the electrical process by which neurons transmit signals:
    • Dendrites receive input, signals travel to the soma, down the axon, and reach the axon terminals where neurotransmitters are released and picked up by the next neuron’s dendrites.
    • This process is electrical in movement and chemical at the synapse.
  • Dysfunctions and disorders tied to these cellular components:
    • Cell body destruction and related disorders (e.g., dysarthria, dysphagia, aphasia) often relate to cortical or subcortical processing deficits.
    • Systemic autoimmune processes, multi-system disorders, or widespread pathology can affect glial function, myelin integrity, and overall neural signaling.

Cytoarchitecture and Brodmann areas

  • Cytoarchitecture refers to the organization of cells in the cerebral cortex and how that organization relates to function.
  • The cortex is mapped by Broadmann areas, which are numbered regions that correspond to distinct cytoarchitectural patterns and functional roles.
  • In class, Broadmann areas are highlighted on brain images as a practical reference for exam questions about localization.
  • The goal is to be able to use this map to link structures to function and to potential pathologies.
  • The cerebrum is composed of lobes, each with characteristic functions.
  • Critical regions and landmarks to know (and why they matter clinically):
    • Primary motor cortex: initiates voluntary motor control.
    • Premotor cortex: involved in planning movements.
    • Supplementary motor cortex: involved in sequencing and planning of movements.
    • Broca’s area: associated with expressive language (speech production) and nearby motor pathways; damage can cause Broca’s aphasia with impaired speech production.
    • Wernicke’s area: associated with language comprehension; damage can cause Wernicke’s aphasia with fluent but often nonsensical speech and poor comprehension.
    • Primary auditory cortex (Heschl’s gyrus): initial processing of auditory information.
  • The relationship between language deficits and brain regions:
    • Broca’s aphasia tends to involve impaired language output and is often adjacent to motor speech areas.
    • Wernicke’s aphasia affects language comprehension and semantic processing, potentially with preserved fluency and prosody.
  • Practical implication for clinical assessment:
    • Understanding where language and motor functions localize helps explain why patients have certain deficits and how therapy might be tailored to address those deficits.

Practical exam-focused takeaways

  • By the end of this section you should be able to:
    • Identify the major lobes of the brain and their general functions.
    • Explain how lesions in different areas lead to distinct clinical symptoms (e.g., language production vs comprehension deficits).
    • Distinguish cortical vs subcortical involvement and relate this to disorders like TBI and Huntington’s disease.
    • Describe the basic structure and function of neurons, glial cells, myelin, gray vs white matter, and action potentials.
    • Recognize the relevance of Brodmann areas in neuroanatomy labeling and exams.
    • Communicate about brain injuries and deficits in a way that is accessible to patients and multidisciplinary teams.

Quick recap and next steps

  • The upcoming quiz will cover chapter material relevant to these topics.
  • Prepare by being able to label primary areas of the cortex, identify Brodmann areas on images, and discuss how disruptions in expressive vs receptive language manifest clinically.
  • Remember the value of interprofessional collaboration in assessment and rehabilitation for brain injury and language disorders.

Notable terminology and recurring concepts

  • Cortical, cortex, cerebral cortex – outer layer of the brain; associated with higher-level functions.
  • Neuron – the primary signaling cell of the CNS; coordinates electrical and chemical signaling.
  • Dendrites – input receivers.
  • Soma (cell body) – integrates information and coordinates response.
  • Axon – conduction pathway from soma to terminals.
  • Axon terminals and synapse – sites of chemical signaling to the next neuron.
  • Glial cells – supportive, cleanup, structural roles; outnumber neurons roughly 9:1 in the CNS.
  • Myelin – insulating sheath around axons that speeds conduction; facilitates rapid communication.
  • Gray matter – neuron cell bodies; site of processing.
  • White matter – myelinated axons; pathways for communication.
  • Broadmann areas – cytoarchitecturally defined cortical regions used to map function.
  • Heschel’s gyrus (Heschl’s gyrus) – primary auditory cortex.
  • Broca’s area – expressive language.
  • Wernicke’s area – receptive language.
  • Expressive vs receptive language – two complementary but distinct language functions.
  • Interprofessional practice – essential for accurate assessment and effective rehabilitation across disciplines.