How Do We Sense, Perceive & See The World? {Exam 2 2/4}

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Side ASide B
What are sensory receptors?
- specialized cells that transduce (convert) sensory energy into neural activity
What are the parts of the sensory systems:
- Light: where light energy is converted to chemical {producing action potentials} - Auditory: air pressure that is converted to mechanical energy - Somatosensory: mechanical energy -...
What is a receptive Field?
- region of the visual world that stimulates a receptor cell/neuron
What is optic flow?
- a stream of visual stimuli that accompanies an observer's forward movement through space
What is auditory flow?
- changes in sound heard as a person moves past a sound source or vice versa
What do both the auditory and optic flow tell us?
- it tells us how fast we are going - the direction in which we are going - and whether or not the object is moving {or if its us}
What is receptor density?
- it is important in determining the sensitivity of a sensory system - our sensory systems use different receptors to enhance sensitivity under different conditions - differences...
What is the neural relay
- this is where all receptors connect to the cortex through 3-4 intervening neurons - most have 3, auditory has 4. - they allow sensory systems to interact - located in the spinal...
How do sensory signals encode the features of particular sensations?
- the presence of a stimulus can be encoded as an increase/decrease in a neuron's firing rate - the amount of increase or decrease can encode the stimulus intensity
what are sensory signals coded as?
- as incoming sequences of action potentials to the CNS
How do action potentials code the different kinds of sensations? (ex. vision vs. touch)
- different sensations are processed in different cortical areas - learn to distinguish senses through experience - each system has a distinct wiring set up at all levels of the neural...
What is syntesthesia?
- mixing of the senses - Ex. when you can "feel" sounds - Ex. like nails on a chalkboard
What is the Topographic Map?
- spatially organized neural representations of the external world. - how most mammals represent the sensory field of each modality in the neo/cerebral cortex
What is sensation?
- the registration of physical stimuli from the environment by the sensory organs
What is perception?
- subjective interpretation of sensations by the brain - how we interpret what we see
What is the retina?
- the light-sensitive surface -- backing of your eye - it consists of neurons and photoreceptors - it translates light into action potentials
How does the eye work?
- as light enters, it bends by the cornea, travels through the pupil, and bends again by the lens
What is the opening where the blood vessels enter in the eye
- the optic disk {aka. blind spot}
What are the 2 types of optical errors of refraction?
- it's when the lens doesn't bend as much as it's supposed to, and the light just ends up being focused before/after the retina
What is myopia?
- nearsightedness - the inability to see things far away - light is undershot and doesn't reach the retina
What is hyperopia
- farsightedness - inability to focus on near objects - light is overshot so it goes past the retina - more common in old people, not as elastic as before.
What is the Fovea?
- the region at the center of the retina that specializes in fine detail - this is also where cones are concentrated (color vision) - there are no rods in this area
What is the blind spot?
- region of the retina (optic disk) where axons form into the optic nerve and leave the eye - no photoreceptors
What are 2 conditions of the blind spot?
- Papilloedema: swelling of the disk caused by cranial pressure - optic neuritis: inflamation of the optic nerve
The difference between rods & cones?
Rods - more in numbers - sensitive to light -- good for night vision - black & white Cones - color vision - specialize in fine detail and only located in the fovea -...
What happens when light hits the photoreceptors?
- it triggers a chemical reaction that leads to the change in membrane potential - the change leads to a change in the release of neurotransmitters
What are the 4 types of retinal-neurons?
- bipolar cell: receives input from photoreceptors - horizontal cell: links photoreceptors & bipolar cells - amacrine cell: links bipolar cells & ganglion cells -...
What are the 2 types of retinal ganglion cells?
- magnocellular cell (M cell) - parvocellular cell (P cell)
What is the magnocellular cell?
- receives input mainly from rods - sensitive to light and moving stimuli {not color though} - found mainly throughout the eye, but not at the fovea - bigger than P-cells
What are parvocellular cells?
- Receive input from cones - sensitive to color differences and form - found ONLY in the retina - small-cells.
What is the Optic Chiasm?
- junction of the optic nerves from each eye
Explain the crossing over & visual pathways
- axons from the nasal retina cross over to the OPPOSITE side - axons from the temporal retina remain on the same side. - just before the optic nerves enter the brain, the optic...
What is the dorsal visual stream?
- pathway that originates in the striate cortex and projects to the PARIETAL lobe. - the HOW pathway {how it moves in the environment}
what is the ventral visual stream?
- The pathway that originates in striate cortex and projects to the TEMPORAL lobe - the WHAT pathway
How many layers does the striate cortex have>
six. {I to V}
what do each of the 6 layers of the LGN do?
- layer 2, 3, 5: receive fibers from the ipsilateral eye (eye on the same side) - layer 1, 4, 6: receve fibers from the contralateral eye (eye on the opposite side) - this lets us combine...
Which layers do P cells go to?
- layers 3-6 because they are responsive to color and fine detail
Which layers do M cells go to?
- layers 1-2 because it controls info processing about movement.
What is the tectopulvinar Pathway
M cells -> Superior colliculus -> pulvinar
What are the 2 major divisions of the pulvinar
- medial pulvinar: which sends connections to the parietal lobe - lateral pulvinar: which sends connections to the temporal lobe.
what is the primary visual cortex?
- receives input from the LGN
what is the extrastriate cortex?
- the visual cortical areas outside the striate cortex
Explain the heterogeneity of V1
- blobs: region in striate cortex that contains color-sensitive neurons - interblob: regions that separate blobs --> peception of form and motion
explain the heterogeneity of V2
- thick stripes: receive information from movement sensitive neurons - thin stripes: receives information from color-sensitive neurons - pale zone: receives information from form-sensitive...
explain the left and right visual lobe
region of the visual world that is seen by your eyes - left visual lobe: right hemisphere - right visual lobe: left hemisphere
What is the on-center cell?
- when light falls onto the central circle
What is the off-center cell?
- where the lights fall on the periphery of the central circle.
What is the luminance contrast
-the amount of light reflected by an object relative to its surroundings.
What is stimulus equivalence
recognizing that an object is the same across different viewing orientations - so even if you're looking at it through tinted glasses, you can still tell that your mac is black.

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