Chapter 5 Sensation and Perception Flashcards
What is a percept?
Mental representation of the original stimulus. The stimulus has been processed and interpreted by the brain
Which 4 things are common across the senses?
1) Collect information from environment
2) Receptor cells transduce stimuli into neuronal signals
3) Have specific sensory nerve pathway
4) Travel through thalamus to primary sensory regions (except olfaction)
What is adaptation and acuity of senses?
Adaptation: adjustment of sensory sensitivity
Acuity: how well we can distinguish among stimuli within a sense
What are the neural pathways of olfaction?
1) Odorants enter nasal cavity
2) Odorants bind to receptors in olfactory epithelium
3) Bipolar neurons send signals to glomeruli in olfactory bulb
4) Axons from glomeruli form olfactory nerve
5) Olfactory nerve projects to primary olfactory cortex/pyriform cortex
6) Signal proceeds to orbitofrontal cortex and other regions
How are olfactory receptors activated? Discuss the two theories
Shape/docking theory = odor molecules bind to receptor that corresponds to shape of molecule
Vibrational theory = similar shaped molecules have different molecular vibrations
Name 3 reasons why olfaction is an unique sense
1) Doesn’t project to thalamus
2) Most axons olfactory nerve project to ipsilateral cortex
3) Connections to amygdala and therefore can affect emotions, autonomic behavior and memory
What are respectively the roles of the primary vs. the secondary olfactory cortex?
1: detecting odor changes
2: identifying odor
What is the neural pathway of gustation?
1) Papillae on tongue contain taste buds with receptor cells (more in back of tongue)
2) Molecule stimulates taste receptor and causes depolarization
3) Receptor cells synapse with bipolar neurons
4) Axons form chorda tympani nerve
5) Projection to gustatory nucleus in brainstem
6) Integration of information can produce rapid reaction if input from gastrointestinal tract is bad
7) Projection to VPM Thalamus
8) Projection to primary gustatory cortex in insula
9) Secondary processing in orbitofrontal cortex
Why are gustation and olfaction so related?
Both secondary processing units are in orbitofrontal cortex
What are the neural pathways for somatosensation?
1) Different types of receptors in skin/musculoskeletal junctions that respond to different types of touch
2) Dorsal root ganglia contain cell bodies
3) Sometimes reflexes, otherwise up in spinal cord
4) Crossing-over in medulla
5) Projection to VPN in thalamus
6) Projection S1, cerebellum and other subcortical structures
What is the difference between S1 and S2?
S1: Simple representation of body (sensory homunculus). Face and fingers have larger area, which corresponds to higher acuity
S2: Complex representations where information from both sides of the body are integrated
What is proprioception?
The sensation of the position of the limbs and head
What is the neural pathway of audition?
1) Sound collected by pina
2) Sound hits tympanic membrane
3) Tympanic membrane moves malleus, incus and stapes
4) Stapes move liquid in cochlea through oval window
5) Hair cells on basilar membrane depolarize when moving
6) Signals from haircells into auditory nerve
7) Projection to cochlear nucleus in Medulla
8) Cochlear nucleus projects to superior olivary nucleus
9) Projection to inferior colliculus, where the signals can trigger motor structures
10) Projection to MGN in thalamus
11) Projection to A1 in superior temporal lobe
Describe the topographic organization of the cochlea
Hair cells for high frequencies are located close to the oval window and lower frequencies are located toward the end of the cochlea
What is tonotopic organization?
The organization of the A1 is tonotopic. The rostral part responds to lower frequencies and the caudal part to higher frequencies.
How can we locate the sounds we hear? Name two ways.
1) interaural time difference: coincidence detectors in medial superior olive must receive input simultaneously to be activated
2) Interaural intensity difference = head causes acoustic shadow. Louder sound on left triggers more activity in left superior olive and only this signal will be processed
What are the neural pathways for vision?
1) Cornea/pupil/lens focus and filter light
2) Retina contains rods and cones photoreceptors that transform light into neuronal signals
3) Receptors to bipolar cells to ganglion cells
4) Ganglion cells form optic nerve in blind spot
5) Optic nerve half crosses in optic chiasm
6) Projection to LGN and pulvinar in thalamus
7) LGN projects to V1 (left visual field ends up on the right)
What is the difference between rods and cones photoreceptors?
Cones allow high intensity color view, highest amount in fovea
Rods allow low levels of light
Few cones per bipolar cell but many rods per bipolar cell
What do the following areas respond to: LGN-V1-V2-V4-V5/MT?
LGN: light
V1: simple forms, edges
V2: more complex forms
V4: color
V5: movement
What happens to the receptive fields when going up in the visual system?
Receptive fields become larger across visual systems
What is cortical magnification?
The size of each unit area is disproportionately represented in visual cortex, where the fovea has the largest area
What happens when you have damage in rods/cones?
Decreased sharpness in vision, increased sensitivity to light, impaired color vision, blind spots in visual field, partial loss of peripheral vision
What is hemianopia?
Lesion in optic chiasm that causes blindness of an entire side of the visual field
What happens when there is a lesion in V1?
It causes blindness in the part of the visual field that projects to damaged area. No entire blindness because of retinotopic mapping
What happens when there is a lesion in V4?
This leads to achromatopsia, where everything is seen in greyscale
What happens when there is a lesion in V5?
This leads to akinetopsia, where everything is seen as a series of pictures
What does the flicker fusion experiment point out?
Perception is not always reality. When presented with fast flickering of red and green, the circle is perceived to be yellow
What is multimodal perception and how does the McGurk effect relate to this?
Multimodal perception is the integration of information from all sensory modalities.
McGurk effect = perception of speech is severely influenced by what you see. Visual is the dominant sense
Where does multimodal perception take place?
Superior colliculus in midbrain combines visual+auditory input.
Superior temporal lobe (STS) is responsible for McGurk effect
What is synesthesia?
Abnormal activation and connectivity patterns where senses get mixed (smelling color)
What is cortical plasticity and what is cross-modal plasticity?
Cortical plasticity = functional reorganization due to experiences. Violin player has more cortical representation of left hand
Cross-modal plasticity = if sensory system is absent, inputs from other sensory systems expand their cortical recruitment. The other senses then get better at sensing
What happens if GABA level is low and what are the consequences for cortical plasticity if that is the case?
If GABA is low, neurons will respond to a wider range of stimuli
If that is the case, there can be more cortical plasticity
