MODULES 4-6

Module 4 Introduction

  • Overview

    • Neural imaging has transformed the study of the brain.

    • Facilitates investigation into localization of brain function without invasive surgery..

Module 4 Structural Imaging

  • Definition

    • Structural imaging involves techniques to visualize the brain's anatomy, generating static images similar to photographs capturing a moment in time.

  • Structural imaging techniques are primarily utilized for anatomical investigations.

  • Common Techniques

    • Examples include:

    • X-ray

    • CT Scan (Computed Tomography)

    • MRI (Magnetic Resonance Imaging)

    • Each technique has varying pros and cons.

Module 4 Functional Imaging

  • Definition

    • Functional imaging measures brain activity during rest or specific tasks.

  • Utility

    • These techniques are essential not just for diagnostic purposes but also for researching functional brain localization: which regions are responsible for which functions.

  • Common Techniques

    • Well-known methods include:

    • fMRI (Functional MRI)

    • EEG (Electroencephalography)

    • Techniques vary in:

    • Spatial resolution (accuracy in location)

    • Temporal resolution (accuracy in timing)

    • Few techniques achieve both high spatial and temporal precision and some are costly.

Module 4 Neurostimulation

  • Definition

    • Neurostimulation methods traditionally serve as interventions for various medical conditions but are increasingly used in research to influence and test neuronal populations.

  • Types of Techniques

    • Invasive Techniques:

    • Deep Brain Stimulation (DBS)

    • Cervical Vagus Nerve Stimulation (CVNS)

    • Non-invasive Techniques:

    • Transcranial Direct Current Stimulation (tDCS)

    • Transcranial Magnetic Stimulation (TMS)

    • Transcutaneous Auricular Vagus Nerve Stimulation (taVNS)

Module 5 Introduction

  • Overview

    • Sensory systems are fundamental for animal survival, serving as the connection between the brain and the external environment.

    • Emphasis on sensory systems' conservation across species, particularly in primary processing areas.

Module 5 Vision

  • Human Sensory Reliance

    • Humans primarily depend on vision, unlike many animals that rely more heavily on hearing.

  • Light as Stimulus

    • The eye processes light as stimuli.

    • Visible light exists within a narrow electromagnetic spectrum, from 400-700 nm.

    • Components of the spectrum:

    • Beyond visible light are X-rays, radar, and broadcast radio waves.

  • Anatomy of the Eye

    • Key structures:

    • Cornea

      • Maintains eye shape and allows light entry.

    • Iris

      • Controls pupil size for light regulation.

    • Lens

      • Focuses light onto the retina, adjustments for focus occur.

    • Vitreous Humor

      • Fills the eye and modifies light trajectory.

    • Retina

      • Contains light receptors and a region called the fovea for detailed image processing.

    • Optic Nerve

      • Carries sensory information back to the brain.

  • Processing Pathways

    • Discussed as contralateral, with the left world processed by the right hemisphere and vice versa.

    • Important note: Each eye processes information from both visual fields, and the image is flipped by the lens.

  • Visual Pathway Complexity

    • Visual pathways need consolidation as each eye contributes to both hemispheres.

Module 5 Transduction of Sound

  • Cochlea and Hair Cells

    • Sound transduction occurs through hair cells in the cochlea, able to respond to specific sound frequencies.

    • Mechanism

    • Sound vibrations cause the tectorial membrane to oscillate, affecting stereocilia on hair cells, leading to action potential generation.

  • Visual vs Auditory Processing

    • Auditory system decomposes sound components similar to how visual neurons respond to orientation.

    • Cells tuned by frequency location:

    • High-frequency cells are at the cochlea's base, low-frequency cells towards the apex.

  • Basilar Membrane Functions

    • High-frequency and low-frequency sound produces distinct wave motions along the basilar membrane, demonstrating place coding for frequency.

Module 5 Sound and the Ear

  • Anatomy of the Ear

    • The outer ear, named the pinna, funnels sounds into the auditory canal, amplifying certain frequencies.

    • Sound waves reach the tympanic membrane, causing it to vibrate.

    • The movement is transmitted and amplified by three ossicles: malleus, incus, and stapes, which contact the oval window leading to the cochlea.

Module 5 Somatosensory Receptors

  • Functionality of Touch

    • The somatosensory system processes texture, temperature, pain, and aids in movement coordination.

Receptor Types

  • Categorized by their adaptive response to stimuli:

  • Nociception:

    • Free nerve endings for pain and temperature (slow: sharp and dull pain).

  • Hapsis:

    • Includes rapidly adapting receptors (like Meissner's and Pacinian corpuscles).

  • Proprioception:

    • Receptors informed on body position (muscle spindles, Golgi tendon organs).

Module 6 Introduction

  • Overview of Movement

    • Movement is essential for finding food, seeking happiness, and avoiding predators, differing widely among species.

  • Frontal Lobe Functions

    • Adding significance to movement, the frontal lobe governs executive functions such as decision-making, impulse control, and social awareness.

Module 6 Frontal Lobe Organization and Development

  • Boundaries of the Frontal Lobe

    • Central sulcus separates it from the parietal lobe; the sylvian fissure from the temporal lobe.

    • Comprises around 20% of cortical tissue.

  • Unique Characteristics

    • Only motor system represented; primary motor cortex is situated on the precentral gyrus, while Broca's area is part of the premotor cortex.

  • Development Aspects

    • The prefrontal cortex evolves into early adulthood; implications for teenage behavior.

Module 6 Motor and Premotor Cortex

  • Cortical Organization

    • Motor cortex (M1) sends commands, while the premotor cortex is responsible for movement planning.

    • Neurons in motor cortex fire based on motion direction.

  • Experimental Evidence

    • Example shows motor cortex neuron activity correlating to movement direction.

  • Planning vs Execution

    • M1 facilitates action, while the premotor cortex plans and sequences muscle actions for intended movements.

Module 6 Movement Control

  • Interaction of Cortical and Subcortical Systems

    • The planning and execution of movements involve both cortical and several important subcortical structures:

    • Basal Ganglia

    • Inferior Olive

    • Cerebellum

    • Role of these structures is to calibrate muscular tension and monitor movements for any errors.

  • Multisensory Integration

    • Execution of actions relies upon sensory integration to formulate precise motor commands.