NEUR1020 W7

• Why did Wundt develop a method called introspection?


  He knew that we see with our minds, and that we don't see all the images that reach our eyes
• What is the difference between sensation and perception?

  Sensation is the ability to detect sensory input.

  Perception is the subjective experiences of sensory input.
• How does our brain visually perceive things?

  To see, the visual system must detect electromagnetic radiation and convert it into neural events
• What does our ability to hear rely on?

  Transformation of sound waves that propagate through a medium.
• What are sound waves generated by?

  Vibrations that alternate in exerting increased and decreased force on air molecules
• How do you describe a 'wave' in sound waves?

  The alternations in air pressure that carry sounds to the ears
• What are the 2 important characteristics of waves?

  Frequency and amplitude
• What is frequency and what does it control?

  Frequency is how often air pressure is increased then decreased over time. It controls the pitch of the sound, where high-pitch are rapid fluctuations and low-pitch are slow fluctuations.
• What is amplitude and what does it control?

  Amplitude is the magnitude of changes in air pressure. It controls the intensity or loudness of sound (big changes make loud sounds).
• How is sound transformed and transduced into signals that sends to the brain?

  Stereocilia (bundles of hair in the cochlea of inner ear) bends when liquid is vibrated by sound waves. When it bends, ions rush to the top of the hair cell and release chemicals at the base. These chemicals bind to auditory nerve cells, creating electrical signal to propagate along auditory nerve to the brain
• What is transduction?

  The conversion of electromagnetic radiation into neural events, which involves visual pigments
• Where are visual pigments contained?

  In outer segments of photoreceptors that form the retina
• How do our eyes transduce light into signals that sends to the brain?

  Photoreceptors contain pigments which absorb photons of light. It begins a process that changes the membrane conductance of the photoreceptor, causing a wave of depolarisation and action potential. Ganglion cells gather signals from the back of photoreceptors, meeting to form the optic nerve
• What is an important characteristic of photoreceptors?

  The pigments are contained in outer segments which are positioned at the back of our retinae, away from the light. This limits the eye as light must pass through a number of cellular layers, which refract light and blur the image before it can reach our photoreceptors
• What is the optic nerve and how is it formed?

  Optic nerve carries signals out o the retinae to the brain. It is formed by the combination of the output of retinal ganglion cells
• What must the optic nerve pass through in order to reach the brain?

  Retinae
• What is the optic disc?

  The point where the optic nerve leaves the eye
• What is the blindspot?

  There are no photoreceptors at the optic disc, so you are blind to images that project to that position on the retinae
• What is the perceptual filling-in process?

  Human visual system assume that what is on either side of the blind spot also within the blind spot
• What does perceptual filling-in and neon colour spreading demonstrate about the human vision?

  It is a construction of what your brain infers and probably present based on available evidence
• What is the naive realism notion?

  We see the world as it really is through our senses
• What are coloured aftereffects?

  Situation where the brain causes you to see things that are not present on the retinae
• What is the Opponent Process theory?

  After a long time viewing of certain colours, you can see oppositely coloured afterimages. This infers that the human visual system contains competitive mechanisms tuned to opposite colours
• What did coloured aftereffects help reveal before technology to study photoreceptors?

  Helped reveal what wavelengths of light cones are maximally sensitive to
• What does the gender face aftereffect show?

  Even our experiences of well known complex forms are subject to change, shaped by visual adaptation
• What is colour constancy?

  In different conditions the colour of the same wavelength of light can look very different. This colour constancy is facilitated by subtracting the influence/impact of light from the impression of object colours
• How are wavelengths shifted?

  A range of wavelengths are reflected from any given surface, and this range is shifted by the light source
• What can the brain's tendency to estimate the prevailing light do?

  Reverse apparent colour and contrast polarity (brightness)
• How many types of photoreceptors do humans usually use and what do they do?

  3 types, which catch photons carried by different wavelengths of light, and then are turned into signals that are sent to the brain
• What are the 3 different cones humans have and their approximate wavelength?

  Short - 430nm

  Medium - 530nm

  Long - 570nm
• How do we experience grey, black and white colours?

  Grey --> when our 3 cones are equally activated

  Black --> when our 3 cones are all minimally activated

  White --> when our 3 cones are all maximally activated
• What is our basis of colour vision dependent on?

  Our ability to detect a ratio of activation across different classes of photoreceptor
• Do dichromats see less or more colours than trichromats?

  Less, because they lack a third class of cone, which would have helped distinguish between colours that equally activate the other 2 classes of cone
• What do you call organisms that rely on 3 types of cones in bright daylight?

  Trichromats
• What does having an extra class of day time photoreceptor have an effect on the human girl?

  They are able to distinguish many more colours than others
• What can visual experiences be a product of, other than retinal images?

  Inferential processes in the brain
• What colours do wavelengths approximately 400nm and 700nm associate with in humans?

  400nm - blue.

  700nm - red.