Brain and Behaviour

• Hue


  Specific or dominant wavelength
• Brightness


  Intensity of light
• Saturation


  Purity of light, richness of colour
• Activation of photoreceptors in the retina transmitted to the lateral geniculate nucleus in LGN in the thalamus


  1. Photoreceptors form synapses with bipolar cells

  2. Bipolar cells form synapses with ganglion cells (optic disc)

  3. Ganglion cell axons travel through optic nerves

  4. Optic chiasm

  5. Optic tract

  6. Synapse in lateral geniculate nucleus (LGN)

  7. Synapse in primary visual cortex
• Types of photoreceptors in the human eye

  • Rods
  • Cones
• Rods


  • One type
  • Provide black and white vision (scotopic vision)
  • Night time vision
  • More sensitive to light
  • Lack fovea (central) vision
• Cones


  • 3 types
  • Provide colour vision (phototopic vision)
  • Responsible for day time vision
  • Provide most of visual info
  • Fovea which mediates our most acute vision only contains cones
• Type 1 cones


  Peak of response is to 560 nm wavelength
• Type 2 cones


  Responds most to 530nm wavelength
• Type 3 cones


  Responds most to 420nm wavelengths
• Colour blindness


  Lack of perception of one colour due to missing opsin type in one or more types of cones
• Protanopia


  Loss of red opsin, red and green looks yellowish
• Deuteranopia


  Loss of green opsin
• Tritanopia


  Loss of blue opsin, blue looks green
• Light from the both left and right visual fields


  Enters both our left and right eye, but when the light reaches the LGN and occipital lobes, the RH processes info from the left visual field and LH processes info from the right visual field
• Axons coming from the medial (towards the middle) part of the retina

  Crosses to the opposite hemisphere at optic chiasm
• Axons coming from the peripheral part of the retina

  Do not cross
• Primary visual cortex (V1)

  • Sensitive to orientation of light/dark regions
  • Spatial frequency or amount of fine/coarse detail
  • Retinal disparity
  • Color
  • Movement
• Orientation


  More neuron firing when light/dark boundary or edge is oriented at a specific angle
• Spatial frequency


  Changes in brightness (number of times an area of visual info shifts from light to dark to light to dark) - high frequency info= lots of small details or for large objects that have clear edges and contours - low frequency info= characteristics of visual scenes with large objects; blurry, not much detail
• Retinal disparity


  Difference in location between eyes - binocular cells become very active when image of an object appears on slightly different areas of left and right retinas - allows to see in 3-D depth - crossed disparity= objects that are close to us, uncrossed disparity= objects that are far away from us
• Color-sensitive cells in V1

  Regions that contains lots of cytochrome oxidase (CO) which is contained in mitochondria
• Ventral visual pathway


  "What" pathways, allows for object recognition, processes colour, texture, detail
• Dorsal visual pathway


  "Where/how" pathway, allows for locating objects in space, perceiving motion relative to other objects, making actions in relation to objects
• Visual agnosia


  Impaired visual object recognition, caused by damage to ventral pathway
• Motion blindness


  Caused by damage to dorsal pathway
• Research methods


  • Lesioning brain tissue (ablation, electrolytic, excitotoxic, temporary)
  • Imaging or recording the activity of live brain tissue (light microscopy, electron microscopy, scanning electron microscopy, CAT/CT, MRI, DTI, PET, fMRI, microdialysis)
  • Manipulating the activity of live brain tissue (lateral hypothalamic stimulation, transcranial magnetic stimulation, transcranial direct current stimulation, deep brain stimulation, optogenetics)
• Observational techniques


  Imaging or recording the activity of live brain tissue
• Experimental techniques


  Lesioning brain tissue, manipulating the activity of live brain tissue
• Sound wave


  Produced by objects that vibrate and set molecules of air into motion, frequency measured in Hertz (Hz) determines pitch
• Pitch


  Determined by place coding (high frequencies move only part of basilar membrane closer to oval window) and rate coding (hair cells fire at same rate as sound frequency)
• Loudness/volume


  Reflects how big the sound waves are
• Timbre


  Complexity of the sound wave, makes different sounds like guitar vs piano
• Sound wave activation of sensory receptors in the ear

  1. Outer ear funnels sound waves into auditory canal, tympanic membrane (eardrum)

  2. Middle ear: ossicles (hammer, anvil, stirrup) push on oval window membrane

  3. Inner ear: fluid movement in cochlea creates traveling wave

  4. Organ of Corti: hair cells attached to basilar membrane, movement of cilia opens ion channels, generates receptor potential
• Auditory pathway from ear to primary auditory cortex

  1. Auditory nerve to cochlear nucleus in medulla

  2. To inferior colliculus in midbrain

  3. To thalamus

  4. To primary auditory cortex in temporal lobe
• Conduction deafness


  No conduction of sound
• Sensorineural deafness


  Problem with structure that change vibrations into neural activity
• Central deafness


  Brain damage
• Cochlear implants


  Treat deafness due to hair cell loss, electrical currents stimulate the auditory nerve
• Anterior/what/ventral auditory pathway


  Helps recognize what sounds are, judge if familiar/unfamiliar