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Behavioral Neuroscience Exam 2
Behavioral Neuroscience Exam 2
Undergraduate 4

Additional Psychology Flashcards




Parts of the eye
  • lens = adjust thickness to achieve focus & change magnification, gets stiffer as they get older
  • retina = image focused by lens upside down and backwards on back plate, transforms & analyzes incoming images
  • choroid = covers retina with black material (itself) to decrease light diffraction
  • iris = controls light level
  • photoreceptors = rods (high sensitivity, low acuity) and cones (low sensitivity, high acuity)
    • trade off size of receptor with sensitiity (large = more sensitive)
Signs of Computation for Vision (3)
  • 1)
    • burst of AP marks exact moment of onset of stimulus
    • continuation/steady train of AP marks intensity of stimulus (more frequent = more intense)
    • turning one form of energy to another
  • 2)
    • flicker fusion occurs at 30 Hz
    • light flashing faster than 30 Hz is seen as a continuous light because steady image more useful
    • visually as action potentials riding on receptor potentials
  • 3)
    • contrast enhancement where AP frequency of receptors A&B stimulated toether is less than when they are stimulated separately - axon collaterals inhibit neigbor by lateral inhibition
    • more relevant information in edges than there is an overall illumination level
    • so at high intensity next to the edge, axon fires more & at other edge of it fires even less than normal low intensity
Ganglion receptive field
  • retinas have annular antagonistic center-surround with lots of convergence - enhance contrast before sending info to CNS
  • more convergence in periphery than fovea
  • receptive field in fovea is smaller for high resolution
  • animals like frogs have retinal processing instead of cortical, "bug detectors" which allows it ot be fast and efficient but difficult to evolve a more complex system & not adaptable & processing done independently of sensesĀ 
Layers of Retina
  • Ganglionic
    • ganglion cells
    • fat somas because they support many axons
    • axons face away from amacrine cells
    • opportunity for convergence & divergence
    • final output stage to CNS
  • Inner Plexiform
    • amacrine cells - movement detection/sensitivity
    • synaptic junctions between bipolar and ganglion cells
    • lateral inhibition (center-surround antagonism) takes place hereĀ 
  • Bipolar/Inner Nuclear
    • another opportunity for convergence and divergence
    • integrate activity from a few (foveal) or many (extra-foveal) receptors
  • Outer Plexiform
    • horizontal cells
    • synaptic junctions between bipolar and photoreceptors
    • dense lateral inhibition here (much center-surround antagonism)
    • another opportunity for convergence and divergence
    • essentially set up receptive field of bipolar and ganglion cells
  • Photoreceptive
    • rods & cones buried in choroid plexus
      • high spatial resolution
      • high metabolism in photoreceptors
      • evolution theory - more layers added on top of receptors
    • transform light to electrical signal
  • Choroid
    • absorb ambient light
    • collection area for waste products to be dumped
Rods & Cones both...
  • have outer and inner segments
  • a synaptic terminal
  • outer segments contain stacked disks full of photopigments
  • disks eventually become detached from membrane
    • phagocytosis in epithelium (metabolism)
    • as many as 4 disks per hour
Rods only
  • more surface area = more sensitive = less spatial resolution
  • prevalent in extrafoveal/periphery
  • detect presence of object
  • sensitive to light intensity
  • night vision
  • larger receptive field
  • high convergence on bipolar & ganglion
  • produce rhodopsin
Cones only
  • shape = less surface ara = less sensitive to light = far more spatial resolution
  • in foveal region - foveate to figure out what an object is
  • sensitive to colors
  • day vision
  • smaller receptive field
  • low convergence on bipolar & ganglion
  • produces cone opsin
phototransduction at the receptor
  • retinal takes 2 configuations = 11-cis in dark and all trans in light
  • in dark, all-trans activated G-protein and that activates cGMP phosphodiesterase (second messenger breakdown)
  • less cGMP = Na channels closed, hyperpolarization
  • Na+ channels held open by cGMP
  • in dark, rods and cones tonically depolarized
  • light causes hyperpolarization
  • Calcium decreases cGMP and that decrases Na and that causes hyperpolarization
  • when light increases, calcium decreases, increase cGMP, increases Na = makes channels available for closing by more light (able to respond to small changes in light)
  • transmitter in rods & cones is glutamate
  • ultimately: when light comes on there is less glutamate released
Receptive Fields - Ganglion, Bipolar, Horizontal, & Photoreceptors
  • effect of neurotransmitter throughout the nervous system is determined by the response of the postsynaptic surface (dendrite, soma) not the type of transmitter
  • light hyperpolarizes photoreceptor, darkness depolarizes - when depolarized, photoreceptor releases glutamate
    • glutamate release is graded based on amount of light
  • next in line: bipolar cells. How a bipolar cell reacts depends on if it's on-center or off-center
    • on-center: less glutamate causes it to depolarize
    • off-center: less glutamate causes it to hyperpolarize
  • as goes the bipolar cell, so goes the ganglion cell
  • horizontal cells connect the photoreceptors and create the anagonistic surround
  • horizontal cell does opposite of light to other cell - targets presynaptic photoreceptor
Magnocellular Pathway
  • receptive fields in peripheral vision = rods = nightvision
  • cover 80% of retinal area
  • fat soma because large input processes = converge info from many bipolar cells
  • large receptive field = high sensitivity & low acuity
  • show particular sensitivity to movement
  • 20% of fibers in otpic tract are "M" fibers, corresponding to the magnocellular system
  • fat soma also because supports thick axon = fast conducting
  • subcortical projections to pretectum (pupillary reflexes) and superior colliculus (visual tracking) as well as LGN and cortex
  • the job of magnocellular system is to detect objects (particularly if they are moving) and bring foveal vision (parvocellular) on target for analysis
Parvocellular Pathway
  • receptive fields in fobeal (central) vision = cones = day vision
  • cover 20% of retinal area
  • small soma because small input processes = converge info from few bipolar cells
  • small receptive field = low sensitivity & high acuity
  • 80% of fibers in the optic tract are "P" fibers, corresponding to the parvocellular system
  • small soa also because supports thin axon = slow conducting
  • no subcortical projections
  • the job of parvocellular system is to provide detailed analysis of an object
Visual Pathway
  • retina -> LGN -> occipital lobe
  • left vision = right hemisphere & vice versa, nasal parts cross through optic chiasm
  • bottom halves (top of cortex) go to bottom half of visual cortex
  • but visually, retina is upside-down & inside out because projected through optical lens
  • fovea = posterior in visual cortex
  • extrafoveal = anterior in visual cortex
  • foveal representation in cortex takes up majority of area due to number of fibers it devotes to it in optic track
  • 6 layers, each layer has nearly complete retinotopic map
  • 20% of fibers to LGN from retina, most from cortex, rest from RAS (in between layers, Koniocellular)
  • 1, 2 = ventral, magnocellular (1 = contra, 2=ipsi)
  • 3, 4, 5, 6 = dorsal, parvocellular (3, 5 = ipsi, 4,6 = contra)
  • function
    • relays visual info to visual cortex
    • antagonistic center-surround fields = contrast
    • where cortex controls/interacts with its own input
    • sharpening of contrast
    • modulate efficacy of synaptic transmission throughput from optic nerveto visual cortex
Band of Billiard
  • thick layer 4 = named striate cortex
  • layer 4 = dark band= very dense
  • massive input from LGN
  • Vernon Benjamin Mountcastle
  • 3 functionally defined dimensions (also a 4th)
  • ocular dominance
  • orientation columns
    • strategic innervation of LGN cells to stellate cells in layer 4 that then strategically converge onto the dendrites of simple cells ot form preference for linear stimulation of retina
  • laminar dimension
  • also blobs/pegs where double opponent color cells are located in yet another distinct columnar system within a hypercolumn
External Auditory System's Processing Jobs
  • amplify sound waves in an adjustable fashion
  • decode the frequency of complex sounds (Fourier analysis)
  • transduce sound information to AP encoded signals
Purpose of connection to tensor tympani & stapedius
  • ossicles connected to tensor tympani and stapedius muscles that provide adjustable gain
  • used to:
    • protect inner ear from harm
    • increase "dynamic range" of exquisitely sensitive inner ear hair cells
    • preadjust volume evel before speaking
    • adjust for centripetal force produced by head rotation
Place Theory tricks
  • 1) basilar membrane is tuned like a piano such that place proximal to oval window like to resonate to high frequencie & places distal resonate at low frequencies
    • but this not precise for two-tone discrimination (discrimination by a single Hz)
  • 2) outer hair cells sympathetically pump the membrane at different places, amplifying effect of passive resonance
    • improves frequency discrimination, but still not enough
  • 3) stereocilia designed like selectively tuned tuning forks, being short & stiff in high frequency & log and floppy in low frequency places
    • improves frequency discrimination, but still not enough
  • 4) stereocilia electrically tuned to preferntially respond to different frequencies - the depolarization/repolarization cycle is faster or slower in fast or slow stereocilia
Auditory Pathway
  • cochlear nuclei
  • superior olives
    • lateral & medial
  • inferior colliculus
  • medial geniculate
  • cortex
cochlear nuclei
  • only area to receive monaural info
  • prevalence of inhibition produced in these cells
  • some enhancement center-surround antagonism in 2 tone experiment
  • exaggerate difference in tones
  • may enhance response to frequency change in particular direction (asymmetrical surround)
superior olives
  • sources of efferents to outer hair cells to effect mechanical lateral inhibition
  • need up to here for intensity discrimination
  • lateral
    • excited by intensity differences between ears
    • localization based on head shadowing
    • useful for frequencies above 1000Hz
  • medial
    • excited by timing differences between ears
    • localization based on phase
    • useful for frequencies below 1000Hz
inferior colliculus
  • receives input from both ears
  • concerned w/ changes in differences between ears
  • movement of sound localization
  • interacts w/ superior colliculi in tracking moving sound source
  • need up to here for frequency discrimination
medial geniculates
  • main way station to cerebral cortex (feedback from cortex)
  • maybe some sharpening center-surround antagonism
  • selective attention ?
  • polymodal responses
auditory cortex
  • localizing complex auditory stimuli in contralateral auditory space
  • organized as primary (pure auditory) and secondary (polymodal) cortex
  • lateral = low
  • medial = high
  • orthogonally, binaural interaction columns = auditory space
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