Notes: Other Senses

History:
10/26/12 - Changed formatting (no content changes)
10/21/12 - Original posted version

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) - ___________________ ossicles - small bones cochlea - ________________ organ of Corti - ______________________                              organ of Corti:ear as _____________:eye semicircular canals    vestibular system    direction & intensity of head movements

Source: http://www.oup.co.uk/oxed/children/oise/pictures/light/earhaircells/ basilar membrane - hair cells mounted here tectorial membrane - rests on hair cells shearing force on hairs cause    increased firing in auditory nerve

higher frequencies closer to the oval window (beginning)

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

Localization of sound

Source: http://www.audiosonica.com/en/wikipedia/Sound_localization

(you don't need to memorize the anatomy, but you do need to understand the principle)

medial superior olives - responds to differences in ________________ of sound  arrival

lateral superior olives - responds to difference in ________________ of sound arrival

these differences can be used to triangulate the source of the sound relative to the observer

superior colliculus (SC)

    deep layers - contain a "map" of the external world
        include auditory inputs

    electrical stimulation to SC can produce attention shifts, saccades, arm reaches, head turns, body turns (rats/fish/birds),
        tongue strikes (frogs), fang-strikes (snakes)

Auditory Cortex

primary auditory cortex - inside (medial) temporal lobe
    functional columns organized by frequency

secondary auditory cortex - outside (lateral) temporal lobe

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 well understood as vision

Damage

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

damage to ossicles = ______________ deafness

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

cochlear implant
    useful if cochlear hair cells are damaged
    electrodes implanted into cochlea
    online videos: http://www.youtube.com/results?search_query=cochlear+implant+hearing+for+the+first+time

Source: http://www.daviddarling.info/childrens_encyclopedia/Health_Revolution_Chapter5.html

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 1. free nerve endings     neurons with no specialized structures 2. Pacinian corpuscles     largest and deepest     adapt rapidly     respond to vibration (surface texture), sudden skin indentation     do not respond to constant pressure     large receptive fields 3. Merkel's disks     adapt slowly     respond to fine skin indentations     small receptive fields 4. Ruffini endings     adapt very little     respond to skin stretch and joint displacement (gripping) (you don't need to memorize which is which, but understand the kinds of stimuli, adaption rates, and differences in receptive fields)

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

Damage / Pathologies

astereognosia
    the inability to recognize objects by touch

asomatognosia
    failure to recognize part of one's body
    usually from damage to right posterior parietal lobe, affecting left side of body

Pain

a protective adaptation of the body
no single stimulus for pain
"no obvious cortical representation"

anterior cingulate cortex (ACC)
    may be associated with the emotional reaction to pain
    ACC responds to many non-pain situations, such as error detection and conflict

periaqueductal gray (PAG)
    electrical stimulation causes pain blocking effects
    contain receptors for opiods (morphine)

 endogenous ___________ (pain killers)
    endorphins & enkaphalins

__________ pain
    originating in the central nervous system
    no obvious cause
    cutting the nerves from source does not help
    reported "source" may even be an amputated limb - phantom limb pain

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

   

Interesting Findings

"Women who correctly picked out their roommate’s scent scored higher on tests of emotional sensitivity" (Chen, Psych Science)

Women can detect genetic differences by smell
    Men (the "stimuli") were profiled for their genetic similarity to the women in the study (the subjects)
    If men were:    highly similar - not as attractive
                            somewhat different - attractive
                            highly different - not as attractive
    Might be selecting for an adaptive or "healthy" difference in genes

"When a person looks at a photograph of a rose while smelling rose oil, for example, she rates the aroma as both more intense and more pleasant than she does if she smells rose oil while looking at a picture of a peanut." (Lundstrom)

"When she wore a perfume of floral and spice notes, the men judged her to weigh about 4 pounds less, on average" (Hirsch)

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)