Speech-Language Pathology Comprehensive Review

Observing Specific Populations

• Pediatric Clients:
  • Sessions targeting articulation (phonological processes) or language development (e.g., late talkers, ASD interventions).
  • Observe how play-based therapy engages children.
• Adults:
  • Therapy for aphasia, dysarthria, or cognitive communication issues.
  • In medical settings, focus on dysphagia management and rehabilitation techniques.

Disorders to Review

• Speech: Apraxia, dysarthria, articulation/phonological disorders.
• Language: Developmental delays, aphasia, specific language impairment.
• Hearing: Auditory processing disorder, cochlear implant rehabilitation.
• Swallowing: Dysphagia in stroke or head and neck cancer patients.

Phonetic Alphabet and Sound Examples

• Consonants:
  • Plosives (stop): /p/ (pat), /b/ (bat), /t/ (tap), /d/ (dog), /k/ (cat), /g/ (go)
  • Fricatives: (a consonant produced by forcing air through a narrow channel made by placing two articulators close together): /f/ (fan), /v/ (van), /s/ (sip), /z/ (zip), /ʃ/ (shoe), /ʒ/ (measure)
  • Affricates: (a phoneme which combines a plosive with an immediately following fricative or spirant sharing the same place of articulation): /ʧ/ (church), /ʤ/ (judge)
  • Nasals: (occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose.): /m/ (man), /n/ (net), /ŋ/ (sing)
  • Liquids: (that are made by partially closing the mouth with the tongue, creating a resonant sound that's similar to a vowel): /l/ (lamp), /r/ (run)
  • Glides: (form the transition between vowels and consonants): /j/ (yellow), /w/ (wet)
• Vowels: Where the tip of the tongue is placed when the vowel is produced
  • Front Vowels: /i/ (see), /ɪ/ (sit), /e/ (bet), /ɛ/ (head), /æ/ (cat)
  • Central Vowels: /ʌ/ (cup), /ə/ (sofa), /ɚ/ (her)
  • Back Vowels: /u/ (food), /ʊ/ (foot), /o/ (go), /ɔ/ (law), /ɑ/ (father)
  • Diphthongs: (combination of two vowels in a single syllable, in which the sound begins as one vowel and moves toward another) /aɪ/ (my), /aʊ/ (how), /ɔɪ/ (boy)

Cranial Nerves

• (SLP mainly needs to know 5,7,9,10,12)
• Gag Reflex: Involves cranial nerves IX and X, triggered by stimulation of the back of the throat
• I. Olfactory
  • Function: Smell.
  • Damage: Anosmia (loss of smell).
• II. Optic
  • Function: Vision.
  • Damage: Blindness, visual field loss.
• III. Oculomotor
  • Function: Eye movement (pupillary constriction).
  • Damage: Ptosis (drooping eyelid), double vision.
• IV. Trochlear
  • Function: Eye movement (superior oblique muscle).
  • Damage: Vertical diplopia (double vision).
• V. Trigeminal
  • Function: Sensation to the face, mastication.
  • Damage: Loss of sensation in the face, difficulty chewing.
• VI. Abducens
  • Function: Lateral eye movement.
  • Damage: Medial strabismus (inability to move eye laterally).
• VII. Facial
  • Function: Facial expression, taste (anterior 2/3 of tongue), salivation.
  • Damage: Facial paralysis, loss of taste in anterior tongue.
• VIII. Vestibulocochlear
  • Function: Hearing, balance.
  • Damage: Hearing loss, vertigo, balance issues.
• IX. Glossopharyngeal
  • Function: Taste (posterior 1/3 of tongue), salivation, swallowing.
  • Damage: Loss of taste, difficulty swallowing, dry mouth.
• X. Vagus
  • Function: Speech, swallowing, heart rate, digestion.
  • Damage: Hoarseness, difficulty swallowing, reduced gag reflex.
• XI. Accessory
  • Function: Shoulder shrug, head-turning.
  • Damage: Weakness in shoulder and neck muscles.
• XII. Hypoglossal
  • Function: Tongue movement.
  • Damage: Tongue weakness, atrophy, difficulty with speech and swallowing.

Motor Pathways

• (Origin, Course, Destination, Decussation, Function, Damage)
• Lateral Corticospinal Tract:
  • Pathway Origin: Motor Cortex
  • Course and Designation: Descends through the brainstem, decussates at the medullary pyramids, travels down the lateral spinal cord, and synapses in the spinal cord's ventral horn.
  • Decussation: At the medullary pyramids.
  • Function: Controls fine motor movements, especially in limbs.
  • Damage Affects: Loss of fine motor skills and voluntary movement in distal muscles, particularly the limbs.
  • Speech/Language Relevance: The motor cortex plays a critical role in the motor planning for speech, including controlling articulation and the movements of the vocal cords, mouth, and tongue.
• Anterior Corticospinal Tract:
  • Pathway Origin: Motor Cortex
  • Course and Designation: Travels down the spinal cord without crossing, then may decussate at spinal levels before synapsing in the ventral horn.
  • Decussation: Some crossing in the spinal cord. No decussation through pyramids.
  • Function: Controls trunk and proximal limb movements.
  • Damage Affects: Impaired control of axial (trunk) and proximal limb muscles.
  • Speech/Language Relevance: Impaired control of the trunk and upper limbs can affect breathing patterns for speech production.
• Corticobulbar Tract:
  • Pathway Origin: Motor Cortex
  • Course and Designation: Descends to various cranial nerve nuclei in the brainstem (midbrain, pons, medulla) without decussating, with bilateral innervation and some contralateral components.
  • Decussation: Mixed, mostly bilateral.
  • Function: Controls muscles of the face, head, and neck.
  • Damage Affects: Weakness or paralysis in facial, head, and neck muscles, which can vary depending on the cranial nerves affected.
  • Speech/Language Relevance: This tract is crucial for the innervation of the muscles involved in speech, including facial muscles for articulation, lip movement, and the muscles of the pharynx and larynx for swallowing and vocalization.
• Rubrospinal Tract:
  • Pathway Origin: Red nucleus (midbrain)
  • Course and Designation: Decussates immediately in the midbrain, then descends through the lateral spinal cord to cervical levels.
  • Decussation: Midbrain.
  • Function: Assists in limb flexion and modulates muscle tone.
  • Damage Affects: Impaired fine control and reduced muscle tone in the upper limbs.
  • Speech/Language Relevance: Although not directly linked to speech, this tract's modulation of muscle tone and limb movement could indirectly impact posture and vocalization efforts.
• Reticulospinal Tract:
  • Pathway Origin: Reticular formation (pons and medulla)
  • Course and Designation: Descends ipsilaterally and bilaterally to various spinal cord levels.
  • Decussation: Depends on exit or level.
  • Function: Regulates posture, locomotion, and reflex modulation.
  • Damage Affects: Disruption in posture control, locomotion, and some reflex activities, leading to balance and coordination issues.
  • Speech/Language Relevance: This tract helps with the postural control necessary for effective speech production, as well as coordinating respiratory rhythms needed for vocalization.
• Vestibulospinal Tract:
  • Pathway Origin: Vestibular nuclei (medulla and pons)
  • Course and Designation: Descends ipsilaterally in the spinal cord; lateral tract goes to lumbar, medial tract to cervical.
  • Decussation: Depends on exit and level.
  • Function: Maintains balance, posture, and head stabilization.
  • Damage Affects: Balance and posture instability, impaired head and neck stabilization.
  • Speech/Language Relevance: Maintaining head stabilization is critical for clear speech production, especially during oral communication where physical posture affects vocalization and resonance.
• Tectospinal Tract:
  • Pathway Origin: Superior colliculus (midbrain)
  • Course and Designation: Decussates in the midbrain and descends to cervical spinal levels.
  • Decussation: Midbrain.
  • Function: Coordinates head and eye movements in response to visual stimuli.
  • Damage Affects: Difficulty orienting head and neck to visual stimuli, reduced ability for visual tracking.
  • Speech/Language Relevance: Helps orient the head and eyes during speech, especially when responding to visual cues during communication.

Somatosensory Pathways

• (Origin, Course, Destination, Decussation, Function, Damage)
• Dorsal Column-Medial Lemniscal Pathway (DCML):
  • Origin: Sensory receptors (touch, proprioception).
  • Course: Axons travel up the spinal cord to the medulla.
  • Decussation: Decussates in the medulla (internal arcuate fibers).
  • Destination: Somatosensory cortex (postcentral gyrus).
  • Function: Fine touch, proprioception (sense of body position).
  • Damage: Loss of fine touch, and proprioception (e.g., loss of ability to sense where limbs are in space).
• Anterolateral Pathway (Spinothalamic Tract):
  • Origin: Sensory receptors (pain, temperature, crude touch).
  • Course: Axons enter the spinal cord and ascend to the thalamus.
  • Decussation: Decussates at the level of entry into the spinal cord.
  • Destination: Somatosensory cortex.
  • Function: Pain, temperature, crude touch sensation.
  • Damage: Loss of pain and temperature sensation (contralateral to injury site).
• Spinocerebellar Tracts:
  • Origin: Proprioceptors in muscles and joints.
  • Course: Axons travel through the spinal cord to the cerebellum.
  • Decussation: No decussation (uncrossed for some tracts).
  • Destination: Cerebellum (coordinates motor control).
  • Function: Proprioception for coordination and balance.
  • Damage: Ataxia, lack of coordination.

Speech Production and Coarticulation

• Coarticulation refers to the influence of surrounding sounds on speech production. This can be anticipatory (forward) or carryover (backward) coarticulation. Articulators do not move at the same speed, creating variations in speech sounds.
• Speech happens at around 14 phonemes per second, with lip rounding due to the different speeds of articulators.
• Consonants are classified by:
  • Place (where in the vocal tract the sound is produced),
  • Voicing (whether the vocal cords vibrate),
  • Manner (the degree of constriction in the vocal tract). Stops and affricates block airflow completely, while continuants like fricatives, nasals, and liquids allow airflow to continue.
  • Stop consonants (e.g., /p, b/, /t, d/) stop airflow, while fricatives (e.g., \"thin,\" \"fin\") are produced with turbulence.
  • Approximants like glides (/j/, /w/) and liquids (/r/, /l/) are less constricted.
  • Affricates combine a stop and fricative sound (e.g., \"ch, j\").
• Voice Onset Time (VOT) measures the delay between the release of a stop and the onset of voicing. This is important for distinguishing between voiced and voiceless consonants.
• Categorical perception means we hear certain speech sounds in fixed categories (e.g., \"b\" vs. \"p\") rather than perceiving gradual changes.
• Frication noise in fricatives is produced by turbulent airflow, while nasals (e.g., /m/, /n/) have energy loss due to damping in the nasal passages.

Acoustic Cues and Perception

• Perceptual normalization helps us make sense of speech despite variability due to differences in speakers (e.g., age, gender, accent). Our brain filters out unnecessary noise or variability and understands speech within context.
• Segmentation: The challenge of identifying boundaries between sounds in continuous speech. This is crucial for understanding how we process speech without clear breaks between words.
• Fricatives and Stops: Acoustic cues for these sounds help in perceiving consonants accurately. In stop consonants, VOT indicates when voicing begins in relation to airflow. For example, \"Dean\" starts voicing immediately (VOT = 0 ms), while \"Teen\" has no voicing until after the release.
• Perceptual Challenges: The Segmentation Problem and the Problem of Invariance explain how different speakers can say the same word with subtle acoustic differences, yet we perceive them as the same. In speech, sounds like /haɪ/ or /hɔɪ/ may sound different but are recognized as the same word because of these adjustments.
• McGurk Effect: When visual and auditory information conflict, the brain combines them into a unique perception (e.g., seeing a speaker say "ga" but hearing "ba" results in perceiving "da").

Prosody and Speech Patterns

• Prosody is essential for conveying emotion and meaning through speech. Right hemisphere damage can impair the ability to produce and understand prosodic features, leading to monotone speech.
• Speech patterns can be segmented into levels of control. At the executive level, apraxia (motor planning disorder) can affect the production of speech sounds, while effector- level issues like dysarthria (motor execution disorder) are caused by damage to the motor muscles involved in speech.
• Speech Segmentation: The challenge of segmenting an acoustic waveform into meaningful units. We use perceptual clues, such as the beginning and end of words, to identify sounds within speech.

Instruments for analyzing speech include

• Oscilloscopes, spectrograms, and audiometers for visualizing and measuring sound waves.
• Microphones (handheld, lavalier, head-worn) capture sound, with different types (omnidirectional, cardioid) providing varying directional sensitivity.
• Pneumotachographs measure airflow, and electromyography (EMG) records muscle activity (useful in speech production and swallowing).
• Spirometers and manometers measure respiratory airflow and pressure, which are important in assessing speech production and breath support.
• Signal-to-Noise Ratio (SNR) is vital for clear speech capture, especially when measuring children’s speech or speech in noisy environments. Instruments must be calibrated to ensure accurate, reliable data.

Motor Theory of Speech

• Motor theory posits that we perceive speech by recognizing the vocal tract gestures used to produce sounds rather than by analyzing the sounds themselves. This theory highlights the importance of motor planning in speech perception.

Anatomy and Physiology of Speech Production

• Respiratory System:
  • The lungs are the power source for speech. They provide air that is necessary for producing sound.
  • Diaphragm: A dome-shaped muscle that separates the chest and abdominal cavities. It plays a key role in breathing and controlling airflow.
  • Rib Cage and Intercostal Muscles: Help with expanding and contracting the chest to control airflow.
  • Trachea: The windpipe that carries air from the lungs to the larynx and vice versa.
  • Larynx (Voice Box): Houses the vocal cords (or vocal folds). The larynx is responsible for producing sound through vibration of the vocal cords as air passes through them.
  • Vocal Folds: Vibrating structures within the larynx, which modulate airflow to create sound. When vocal cords are together and air passes through, sound is produced. Tension and length of the cords affect pitch, while the force of air influences loudness.
• Phonatory System:
  • The larynx is crucial in modulating the pitch, volume, and quality of speech. It controls the vocal cords and regulates airflow.
  • The vocal cords move in such a way that they vibrate as air passes through, which creates sound waves. These vibrations are modified by the vocal tract to produce different speech sounds.
• Articulatory System:
  • The oral cavity: Includes the tongue, teeth, lips, hard palate, and soft palate (velum). These structures help shape sounds into recognizable speech.
  • Tongue: It is crucial in articulating sounds, with different parts of the tongue (tip, body, root) responsible for producing different consonants and vowels.
  • Teeth: Used in the production of some consonants, such as /f/, /v/, and dental sounds.
  • Lips: Essential for labial sounds like /p/, /b/, /m/, and rounded vowels.
  • Velum (Soft Palate): Elevates to close the passage to the nasal cavity during the production of non-nasal sounds. For nasal sounds, the velum lowers to allow air to flow through the nose.
• Resonatory System:
  • Pharynx: The throat area that serves as a resonating chamber, amplifying sounds produced by the vocal cords.
  • Oral and Nasal Cavities: Both act as resonating spaces. The oral cavity is important for shaping the sound produced by the vocal cords, while the nasal cavity is involved in nasal sounds.
• Nervous System:
  • Central Nervous System (CNS): The brain plays an essential role in controlling the complex processes of speech production. The motor cortex sends signals to the muscles involved in articulation.
  • Cranial Nerves: Several cranial nerves, including the vagus nerve (X), trigeminal nerve (V), and facial nerve (VII), control the muscles of speech production. These nerves send motor signals to the lips, tongue, soft palate, and larynx.

Anatomy and Physiology of Hearing

• Outer Ear:
  • Pinna: The external part of the ear that captures sound waves and funnels them into the ear canal.
  • Ear Canal (External Auditory Meatus): Carries sound waves toward the eardrum (tympanic membrane).
• Middle Ear:
  • Tympanic Membrane (Ear Drum): Vibrates in response to sound waves and transmits these vibrations to the middle ear ossicles.
  • Ossicles: Three tiny bones (malleus, incus, and stapes) in the middle ear that transmit sound vibrations from the eardrum to the inner ear. The stapes (stirrup) transmits vibrations to the oval window, which leads to the cochlea.
  • Eustachian Tube: Equalizes air pressure in the middle ear, ensuring that the tympanic membrane vibrates freely.
• Inner Ear:
  • Cochlea: A spiral-shaped organ that converts sound vibrations into electrical signals that the brain can interpret. It contains the basilar membrane, which vibrates in response to sound, and the hair cells, which are sensory receptors that detect these vibrations.
  • Semicircular Canals: Part of the vestibular system, they help with balance but are not directly involved in hearing.
  • Auditory Nerve: The electrical signals from the cochlea are sent via the auditory nerve to the brain for processing.
• Auditory Pathway:
  • The auditory nerve transmits signals from the cochlea to the brainstem, which processes sound information. From the brainstem, the signals are sent to the auditory cortex in the temporal lobe, where the sound is interpreted as meaningful information.

Central Auditory Processing

• Auditory Cortex: Located in the temporal lobe, this region is responsible for processing sound. It helps the brain understand pitch, loudness, and other features of sound, and is essential for speech comprehension.
• Speech and Hearing Integration:
  • Speech Perception: The brain integrates auditory input with motor plans for speech. This allows for the recognition of spoken language and coordination of speech production. The auditory system provides feedback, allowing us to adjust speech sounds in real time based on what we hear.
  • Neuroplasticity: Both speech production and hearing involve significant neuroplasticity, meaning the brain can adapt to changes and injuries. For instance, in cases of hearing loss, the brain may rely more heavily on visual or tactile feedback to produce or understand speech.
• Key Disorders:
  • Speech Disorders: These can result from issues with the respiratory system (e.g., weakness in the diaphragm), laryngeal dysfunction (e.g., vocal fold paralysis), or articulatory problems (e.g., cleft palate).
  • Hearing Disorders: Can be caused by damage to the outer, middle, or inner ear, or auditory nerve. Conditions like sensorineural hearing loss (damage to the cochlea or auditory nerve) and conductive hearing loss (blockage or damage in the outer or middle ear) are common.

Basic Neural Structure and Function

• Neurons: The fundamental units of the nervous system, neurons transmit electrical impulses (action potentials) that allow communication within the brain and throughout the body. They have three main parts:
  • Cell Body (Soma): Contains the nucleus and most of the organelles.
  • Dendrites: Branch-like structures that receive signals from other neurons.
  • Axon: A long projection that transmits electrical impulses to other neurons or muscles.
• Synapses: Junctions between neurons where communication occurs through the release of neurotransmitters. The synapse consists of:
  • Presynaptic Neuron: The neuron sending the signal.
  • Postsynaptic Neuron: The neuron receiving the signal.
• Neurotransmitters: Chemical substances (e.g., dopamine, serotonin, glutamate) that carry the signal across the synapse.
• Glial Cells: Support cells that assist in maintaining homeostasis, forming myelin, and providing support and protection for neurons. Examples include astrocytes, oligodendrocytes, and microglia.
• Brain Structure and Function:
  • Cerebrum:
    • The largest part of the brain, responsible for higher-order functions like reasoning, decision-making, and voluntary movements.
    • Divided into two hemispheres (left and right), each controlling the opposite side of the body.
    • Divided into four lobes:
      • Frontal Lobe: Involved in motor control, problem-solving, and planning. Contains the motor cortex, which controls voluntary muscle movements.
      • Parietal Lobe: Processes sensory information, such as touch, temperature, and pain.
      • Temporal Lobe: Processes auditory information and is involved in memory and language comprehension.
      • Occipital Lobe: Primarily responsible for visual processing.
  • Cerebellum:
    • Located at the back of the brain, it is involved in coordinating movement and maintaining balance. It receives information from the sensory systems and helps fine-tune voluntary movements.
  • Brainstem:
    • Includes the midbrain, pons, and medulla oblongata, which regulate essential functions such as heart rate, respiration, and sleep. It also serves as a relay station between the spinal cord and the brain.

Neuroanatomy of Speech and Hearing

• Broca’s Area:
  • Location: In the left frontal lobe, usually in the inferior frontal gyrus.
  • Function: Critical for speech production and language comprehension. It is involved in planning and coordinating the muscles involved in speech, including the mouth, lips, and vocal cords.
  • Damage Effects: Damage to Broca's area can result in Broca’s aphasia, characterized by non-fluent speech, difficulty with articulation, and agrammatism (difficulty with sentence structure).
• Wernicke’s Area:
  • Location: In the left temporal lobe, typically in the posterior part of the superior temporal gyrus.
  • Function: Responsible for the comprehension of speech and the formation of meaningful speech. It helps decode the meaning of words.
  • Damage Effects: Damage to Wernicke’s area can lead to Wernicke’s aphasia, which is characterized by fluent but nonsensical speech and impaired comprehension.
• Arcuate Fasciculus:
  • Location: A bundle of nerve fibers that connects Broca’s area and Wernicke’s area.
  • Function: Plays a key role in repetition of speech and language processing between comprehension and production areas.
  • Damage Effects: Damage can lead to conduction aphasia, characterized by impaired repetition of words or sentences despite fluent speech production and comprehension.
• Primary Motor Cortex: Located in the frontal lobe, it controls voluntary movements of the muscles involved in speech production (lips, tongue, vocal cords).
• Auditory Processing:
  • Primary Auditory Cortex: Located in the temporal lobe, it is responsible for processing auditory information from the ears. The auditory pathway begins at the ear and proceeds to the brainstem, then to the thalamus, and finally to the primary auditory cortex.
• Association Areas:
  • Angular Gyrus: An association area in the parietal lobe that helps process written language and is involved in reading and writing. Damage can result in alexia (difficulty reading) or agraphia (difficulty writing).
  • Arcuate Fasciculus: A bundle of nerve fibers connecting Broca’s area and Wernicke’s area, enabling the integration of language production and comprehension.
• Neuroplasticity:
  • The brain has the ability to reorganize itself by forming new neural connections, especially in response to learning, experience, or injury. This phenomenon is called neuroplasticity. In the context of speech and hearing, neuroplasticity plays a crucial role in language recovery after a stroke or other brain injury, as undamaged parts of the brain may take over the functions of damaged regions.
• The Role of Neurotransmitters:
  • Neurotransmitters are chemicals that help transmit signals across synapses. Some important neurotransmitters in speech and hearing include:
    • Glutamate: The primary excitatory neurotransmitter, involved in many brain functions, including memory and learning.
    • GABA: The primary inhibitory neurotransmitter, regulating excitability in the brain.
    • Dopamine: Involved in reward and motivation, as well as motor control.
    • Serotonin: Plays a role in mood regulation and sensory perception.

Neuroscience of Sensory Perception

• Somatosensory System:
  • The somatosensory cortex in the parietal lobe processes sensory information from the skin, muscles, and joints. This is important for the perception of touch, temperature, and proprioception (body position).
• Visual and Auditory Pathways:
  • Visual Pathway: Information from the retina is sent via the optic nerve to the occipital lobe for processing. The brain's visual centers decode color, motion, and form.
  • Auditory Pathway: Sound information travels from the ear to the brainstem, through the thalamus, and ultimately to the auditory cortex in the temporal lobe.
• Key Disorders:
  • Stroke: A disruption in blood flow to the brain that can result in aphasia (language disorders), motor deficits, and sensory disturbances. The location of the stroke determines the specific deficits.
  • Parkinson’s Disease: A neurodegenerative disorder that affects the basal ganglia and is characterized by tremors, rigidity, and speech difficulties due to impaired motor control.
  • Multiple Sclerosis: An autoimmune disease that damages the myelin sheath in the CNS, leading to motor, sensory, and cognitive impairments.
  • Tinnitus: The perception of ringing in the ears, often resulting from damage to the auditory system.