Notes: Other Senses

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Hearing

Sound

a wave of air pressure

amplitude of the wave - ______________

frequency of the wave - ______________ (with some caveats)

complexity (how many frequencies) - ______________

natural sounds are made up of many different frequencies

Ear

tympanic membrane (ear drum) - ___________________ cochlea - ________________ semicircular canals (vestibular system)    contain fluid and hair cells to detect movement    direction & intensity of head movements

Source: http://www.oup.co.uk/oxed/children/oise/pictures/light/earhaircells/ cross section of inside of cochlea two different membranes have hair stretched     between them sound vibrations cause shearing force on hairs mechanical disruption from shearing force allows     ions to flow through membrane increased firing in auditory nerve

tonotopic organization - by ________________

Auditory pathways

cochlea -> auditory nerve -> hindbrain ->     cochlear nuclear - input from only one ear (From here on input from one/both ears)     superior olives - sound localization thalamus     medial geniculate nucleus primary auditory cortex

Auditory Cortex

primary auditory cortex - inside (medial) temporal lobe
    functional columns organized by frequency
    stimulation leads to perception of ____________________________

secondary auditory cortex - outside (lateral) temporal lobe
    stimulation leads to perception of ____________________________

pathways leaving the auditory cortex
    anterior auditory pathway - towards prefrontal cortex - ________ a sound is

    posterior auditory pathway - towards parietal lobe - __________ a sound is

posterior parietal cortex
    neurons in monkeys that respond to both vision and sound
    integrating vision and hearing

Audition is not as extensively mapped out as vision

Damage

Lesions to auditory cortex = only temporary deafness
    Long term problems with sound localization and pitch differentiation

damage to cochlea or auditory nerve = ______________ deafness
    loss of hair receptors
    characteristic of age-related hearing loss

perception of ringing ("ringing in the ears") = ______________
    cutting auditory nerve from ringing ear doesn't eliminate ringing
    may originate in the central nervous system

Somatosensory system

somatosensory - sensations of the body

stereognosis - identifying objects by touch

Cutaneous Receptors

principle
    fast versus slow adaptation
    fast are necessary for quick responses but, without adaptation, would be overwhelmed by continuous stimuli
    slow are necessary for background information about continuous stimuli

Mechanoreceptors Perceive pressure, vibration (texture), stretch Thermoreceptors detect changes in ______________ typically free nerve endings (not specialized structures) different receptors for detecting heat and coolness Nociceptors noci = ______________ detect stimuli that could be damaging to tissue receptors for: extreme temperature, skin deformation, skin incision, chemicals (capsaicin) fast & slow conducting channels - immediate and chronic pain

Somatosensory Pathways

dermatomes
    nerves from cutaneous receptors enter the dorsal route of the spinal cord
    areas of the body that carry information to the same segment of the spinal cord are called dermatomes

1. dorsal-column medial-lemniscus system

   information about  ____________________
    spinal cord -> ventral posterior nucleus (thalamus) ->
        primary/secondary somatosensory cortex or posterior parietal cortex
    3 neurons from toe to cortex

2. anterolateral system

    information about ____________________
    3 different tracts to different areas of the brain

    lesions of spinothalamic tract reduce sensitivity to __________
       
    lesions of spinoreticular tract relieves ______________

Somatosensory Cortex

Source: http://www.mcgill.ca/about/history/more-history/firsts/1950

Source: http://www.isis-robotics.com/en/references.html

1937 - Dr. Wilder Penfield electrically stimulates the cortex of patients
    finds an area that produces sensations through out the body
    somatosensory cortex

______________ organization
    areas of the body that are close together are represented close together in the brain
    like retinotopic and tonotopic

    somatosensory _______________
        a "little man", or representation of the body in the somatosensory cortex
        larger areas of cortex dedicated to areas of the body with greater sensitivity
   

Source: http://brainmind.com/BrainLecture8.html

Source: http://daphne.palomar.edu/ rmorrissette/physio/studentwebpages/ 2006spring/phantom%20pain/ web%20page.htm

contralateral input to primary somatosensory cortex
   
    the _______ side of the brain receives input from only the _____ side of the body (and vice versa)

secondary somatosensory cortex
    just ventral to primary somatosensory cortex
    receives input from both sides of the body

receptive fields
    excited by stimulus to a given area on the body
    inhibited by stimulus to the surrounding areas

cortical organization
    columns (moving down from the surface) - all neurons tend to respond to same area of body
    strips (moving across the surface) - different stimulus types: touch, temperature, pain

posterior parietal cortex
    receives information from both primary and secondary cortex
    we already learned: also receives input from visual and auditory cortex
   
    contains __________ neurons that response to two senses, like vision/touch   
    for a given neuron, the visual field "moves" to stay with corresponding part of the body
    case study: W.M. - using your hand to improve visual attention

    this area of the brain __________ information for different senses

Chemical sense

the "oldest sense"
    even single cell bacteria can sense chemicals in their environment

____________ - smell, detecting chemicals in the air

_________ - taste, detecting chemicals in the oral cavity

___________ - the combination of smell and taste

____________ - chemical signals to other members of the species

Olfactory System

chemicals are detected by receptors on the membrane    of dendrites in the nose humans have _________ distinct receptor proteins     neurons typically have a single receptor type     odors activate multiple receptors olfactory pathway     receptors ->     olfactory bulb ->        inputs are grouped by similar receptor type     piriform cortex / amygdala ->        ~primary olfactory cortex retinotopic, tonotopic, somatotopic -> smellotopic?     no known principle for how odors are organized across     olfactory bulbs (no such thing as "smellotopic") ______________ - the birth of new neurons     olfactory receptors are replaced every few weeks     grow axons to the correct place in olfactory bulb     one of the few brain areas with noticeable neurogenesis

Gustatory System

___________ - clusters of approximately 50 taste receptors taste receptors     do not have axons     many taste receptors pool to an output neuron     33 receptor proteins identified conventional tastes    1.  sweet - ______________, 2 known receptors     2. sour - _____________, influence ion channels directly     3. bitter - 30 known receptors         4. salty - __________, influence ion channels directly         5. unami - ____________, 1 known receptor pathway     leave tongue along 4 different nerves ->     (thalamus) ventral posterior nucleus ->     primary gustatory cortex (near somatosensory cortex) &     secondary gustatory cortex (inside lateral fissure)