Physiological Psychology Lecture 7

PSY 3 - Lecture 7: Physiological Psychology

Overview of Lecture Topics

  • Sensation and perception

  • Sensory interactions

  • Auditory system

  • Soundwaves

  • Anatomy and function of the ear (outer, middle, inner)

  • Primary auditory pathway

  • Tonotopic organization of A1

  • Sound localization using interaural differences

  • Vestibular system

Sensation and Perception

  • Sensation:

    • Definition: The process by which sensory receptors and the nervous system receive and represent stimulus energies from our environment.

    • Functions of Sensory Receptors:

    • Specialized neurons respond to specific stimuli.

    • They detect stimulus energy and convert it into neural signals.

  • Perception:

    • Definition: The brain’s organizing and interpreting sensory information, transforming it into meaningful objects and events.

    • Note on Representation:

    • The representation received is modified by cognitive schemas, which may lead to perceptions that are minimally or drastically different from original stimuli.

Processing of Information

  • Bottom-up Processing (Sensation):

    • Definition: Stimulus and senses-driven processing that begins with sensory receptors and works its way up to the integration in the brain.

  • Top-down Processing (Perception):

    • Definition: Schema-driven processing, guided by higher-level cognition, unique to each individual, drawing on experiences and expectations.

Sensory Interactions

  • In real-life situations, information from various sensory systems interacts.

  • One sense can influence another (e.g., vision impacting audio perception).

    • Example:

    • Difficulties in conversations conducted over webinars (Zoom, FaceTime) due to lag time between audio and visual feed.

    • Observing someone's mouth can aid comprehension when sound is unclear, indicating the interdependence among sensory modalities.

Auditory System Overview

  • Hearing:

    • Stimulus is sound, produced by objects that vibrate and create pressure waves in the air.

    • Important Note:

    • Air molecules do not travel across a room; they oscillate back and forth.

Sound Production, Amplitude, and Frequency

  • Amplitude: Measures the intensity of a sound wave and is quantified in decibels (dB).

    • Larger amplitudes result in higher dB, perceived as louder sounds.

  • Frequency: Refers to the number of vibrations or cycles per second, measured in hertz (Hz).

    • Human hearing range is from 20 Hz to 20 kHz (20,000 Hz), with frequency perceived as pitch.

    • Types of Sounds:

    • Pure tones: Sounds with a single frequency (rare in nature)

    • Complex sounds: Sounds composed of multiple frequencies, perceived as timbre.

Age and Hearing

  • Ability to perceive high-frequency sounds decreases with age; hearing loss is currently non-preventable and caused primarily by damage from loud sounds.

  • Importance of preventing damage to hearing is underscored, but note that damage is preventable but not reversible.

Structure of the Ear

  • Division of the Ear

    • Outer ear

    • Middle ear

    • Inner ear (cochlea)

Outer Ear

  • Components:

    • Pinna:

    • Visible portion; collects sound waves.

    • Enhances some frequencies (2,000-5,000 Hz), relevant to speech perception.

    • Ear Canal (Auditory Canal)

    • Tympanic Membrane:

    • Also known as the eardrum, it separates the outer and middle ear.

Middle Ear

  • Functions like a tiny microphone.

  • Components:

    • Tympanic Membrane (inner layer)

    • Ossicles:

    • Includes malleus (hammer), incus (anvil), and stapes (stirrup).

    • Smallest bones in the human body; amplify and concentrate sound waves.

    • Muscles (Tensor Tympani and Stapedius):

    • Act as protective features against loud sounds, provide volume control.

Inner Ear (Cochlea)

  • Structure: Spiral-shaped and contains three parallel, long fluid-filled chambers: vestibular duct (perilymph), cochlear duct (endolymph), and tympanic duct (perilymph).

  • The Organ of Corti serves as the micro-organ of hearing, containing hair cells that transduce hydraulic energy into neural impulses.

Sound Wave Transformation

  • Sound waves create ripples in perilymph, causing vibrations of the tectorial and basilar membranes, resulting in neural activity.

  • Tonotopic Coding:

    • High frequencies are maximally moved at the base of the basilar membrane; low frequencies at its apex.

Cochlear Coding and Auditory Processing

  • Inner Hair Cells (IHCs):

    • Perform transduction of sound waves into neural impulses; damage results from exposure to loud sounds.

    • Mechanoreceptors open ion channels through mechanical energy, leading to depolarization and neurotransmitter release to auditory nerve cells.

Sound Localization

  • Interaural Cues:

    • Used to locate sound sources in the horizontal plane, processed by the superior olivary nuclei.

    • Interaural Intensity Differences (IIDs): Differences in loudness between ears.

    • Interaural Temporal Differences (ITDs): Differences in timing of sound arrival between ears.

Vestibular System

  • Located within the inner ear, composed of:

    • Semicircular canals (three fluid-filled tubes) oriented in three planes of head movement.

    • Utricle (horizontal) and Saccule (vertical) serve balance functions.

Chemical Senses: Gustation (Taste)

  • Taste receptors, typically modified skin cells within taste buds that regenerate every 10-14 days.

  • Types of Taste Receptors:

    • Sour, salty (ionotropic), and sweet, bitter, umami (metabotropic).

  • The perception of taste is influenced by multiple factors, including overall health, number of papillae, and history of exposure to specific tastes.

Chemical Sense: Olfaction (Smell)

  • Detection of chemicals critical for food selection and ecological interactions, linked with taste perception.

  • Olfactory Receptors located in the olfactory epithelium are characterized by their ability to regenerate and respond to specific odor molecules, bypassing the thalamus to project to the amygdala and primary olfactory cortex.

Pheromones

  • Chemicals affecting behavior within the same species, with some evidence in humans regarding their influence on social and sexual behavior.

Wider Implications

  • Discussion of the importance of sensory systems in survival, social interactions, and the unique perceptual experiences of individuals.

Concluding Thoughts

  • Sensory systems are vital for interacting with the environment, influencing behavior and decision-making in various contexts.

  • Understanding the structural and functional aspects of these systems enhances insight into human experience and behavior.