Class 7,8,9,10 Flashcards
Olfactory receptor neurons are __
bipolar: one dendrite out to the nasal cavity
Each dendrite has ~____ cilia in __
10-15 tips (cilia) in a layer of mucus
Cilia have __
have places for chemicals to bind onto
Olfactory receptors synapse onto
mitral cells in glomeruli (sing. glomerulus)
Olfactory receptors of the same type synapse onto the same
glomerulus
Ascending olfactory pathway
(Side notes - • Olfactory information does not pass through the thalamus • Unique to olfaction • Largely ipsilateral projections)
Axial Slice
Horizontal slice that is angled
Sniffing vs. Smelling
- Differential involvement of cortical regions based on stage of olfaction
- Sniffing rate can affect the rate of smell detection and clearance
olfactory system is able to pick up on molecules released from __ which can modulate __
tears, arousal
(men did not find picture of women as attractive if they were smelling tears)
What is the role of olfaction?
rotten food
detection of danger
some form of communication/social bonds modulated by olfactory system
The five basic tastes that we recognize
• Sweet • Sour • Salty • Bitter • Umami (orig: うま味 pleasant taste)
Taste buds are on __ are __
papillae, are groups of taste receptors
Different sizes of __ on the tongue in ___
papillae, different regions
Taste buds contain a combination of __ cells
recptor
Receptors are activated differently depending on the receptor type
Cranial nerves VII and IX carry information from ___ to the (____) brainstem
information then reaches ___
taste receptors
(nucleus of solitary tract)
thalamus in ventral posterior nucleus
than to the Primary gustatory cortex
Primary gustatory cortex is ___
insula and operculum
One goal of olfaction is to help with __
finding food and determining whether it is good to eat
Disorders of olfaction have been associated with
reduced food intake and enjoyment
- General reduction in quality of life can be seen in some patients
- This effect appears to lessen with prolonged duration of the disorder
Somatosensation
(& the three systems)
Sensations from the body: Greek soma (the body) + sensation
Three systems involved:
- Exteroceptive (external stimuli)
- Proprioceptive (position of body)
- Interoceptive (condition within the body)
Types of sensations:
- Mechanical stimuli (touch)
- Thermal stimuli (temperature)
- Nociceptive stimuli (pain)
Types of cutaneous (___) receptors
(skin)
Merkel cells, Meissner’s corpuscles, Pacinian corpuscle, Ruffini corpuscle, Free nerve endings
Merkel cells
(Merkel’s discs)
• Sustained touch, slow to adapt
Meissner’s corpuscles
Light touch, fast to adapt
Pacinian corpuscle
Sudden deep pressure, fast to adapt
Ruffini corpuscle
Stretching of skin, slow to adapt
Free nerve endings
- Thermoreceptors
- Nociceptors
Fast vs Slow Adapting receptors
Receptive Fields
Sizes of receptive fields vary depending on the type of receptor and location on body
- Larger receptive fields = detecting change over wider area, less precise
- Smaller receptive fields = detecting change over small area, very precise
Cell bodies of touch receptors
Reflex Circuits
Actions that are completed without neural control directly from the brain
- Sensory information carried to spinal cord via afferent fiber
- Usually (but not always) at least one interneuron within spinal cord connects sensory neuron to motor
- Efferent fiber (motor neuron) sends signal to muscle to respond
Dorsal-column medial-lemniscus system
Fine touch, vibration, two-point discrimination, proprioception
(Ascending somatosensory pathway)
Anterolateral system
Temperature, pain
(Ascending somatosensory pathway)
Primary Somatosensory Cortex
S1
- Mapped based on part of body that receives tactile input (touch, temperature, pain, etc.)
- Representation of body parts proportional to density of touch receptors
- This mapping is also upside-down in cortex
Bimodal Neurons
Receive somatosensory and visual information
• After learning to use a tool, the corresponding visual receptive field expands to include the too
The rubber hand illusion
Processing of both visual and touch information during the RHI involves several brain regions implicated in visuotactile integration
Deffinition of Pain
“an unpleasant sensory and emotional experience associated with actual and potential tissue damage, or described in terms of tissue damage, or both”
Three Part process of pain
Sensory-discriminative (e.g. S1)
Affective-motivational (e.g. amygdala)
Cognitive-evaluative (e.g. insula)
Pain pathways are coded by __ and ascends by__
Descending pathways can modulate___ by the ___ which includes/is contributed by __
free nerve endings, Ascends via anterolateral tracts
the ascending input, PAG
- Cognitive contributions to pain modulation
- Opioids (e.g. morphine) act on this descending pathway
Role of the Ossicles
to Amplification of sound pressure onto oval window
Ossicles act like levers to increase pressure onto smaller space (Oval window is much smaller than tympanic membrane)
The Ossicles
MIS (Mallleus, Incus, Stapies)
The cochlea chambers
scala vestibuli, scala media, scala tympani.
Scala vestibuli and scala tympani are continuous
Hair cells arranged into__ inner hair cells and ___ outer hair cells
single row of inner hair cells and 3 rows of outer hair cells
hair cells total
18000-23000
hair cells synapse onto
spiral ganglion cells
• Cell bodies make up spiral ganglion • Axons form auditory nerve
Movement of basilar membrane due to __ results in ___
sound results in the bending of stereocilia
Changes in the membrane potential of the hair cell are the result of __ which results in __
the opening of K+ channels located at the tip of the stereocilia
K+ influx into the cell from the surrounding endolymph results in depolarization, the opening of Ca2+ channels and the release of neurotransmitter onto spiral ganglion neurites
Most spiral ganglion cells receive input from
a single inner hair cell at a particular location on the basilar membrane
Spiral ganglion cells generate __ in response to __
action potentials in response to the sound of a specific frequency: the neuron’s characteristic frequency
Location of Spiral Ganglion
Two main properties determine how the basilar membrane responds to sound
Width and stiffness
The basilar membrane is organized according to a place code for frequency – a tonotopic map
Place code
the location of the response along the basilar membrane codes the frequency of a tone
Temporal code
the frequency of action potentials matches the frequency of a tone
Volly
accomplished by groups of neurons
(Volley theory states that groups of neurons of the auditory system respond to a sound by firing action potentials slightly out of phase with one another so that when combined, a greater frequency of sound can be encoded and sent to the brain to be analyzed.)
Each ear projects to
both hemispheres
Coincidence detectors
Cells in brainstem respond to small timing differences
help determine location of sound
medial superior olive (MSO) is where
the first stage of comparison is made
Inferior colliculus in audition
Relays information up to the thalamus
Also aids in processing info of aversive stimuli (startle response)
Auditory cortex in audition
Medial geniculate nucleus projects to primary auditory cortex (A1) • Brodmann Area 41
- A1 cortical neurons are sharply frequency tuned
- Form tonotopic map
- Frequency-defined receptive field
Auditory Pathway
Core of Auditory Cortex
(A1, rostral, rostro-temporal regions):
simple sound features
• Input from MGN
Belt and parabelt of Auditory Cortex
increasing levels of complexity in sounds
Rostral to Caudal in auditory cortex
What to Where
- *Rostral** regions more responsive to sound identity
- *Caudal** regions responsive to sound location
Moving outward from A1 involves
more and more complex percepts
- Selectivity for voices
- Sensitivity to pitch
Retna cell Layers
M cells
motion detection
Rods
have pigment __
sensitive to ___
detets __
Located__
rhodopsin
- Sensitive to small amounts of light
- Saturated when there is a lot of bright light
- Detects black and white
- Located in the periphery of retina
- Many rods connect to one ganglion cell
Cones
have pigment __
sensitive to ___
detets __
Located__
photopsin
- Sensitive to large amounts of light
- Detects colour
• Three different kinds (Blue, green red)
Located in the fovea (center) of retina
Few cones connect to one ganglion cell
Blue cones
Short wavelengths
Green Cones
Medium wavelength
Red Cones
Long wavelength
Ganglion Cells
Innervate the ___
Types __
- Innervate the lateral geniculate nucleus (LGN)
- Many different kinds of ganglion cells (ex. M and P cells)
M cells
Ganglion Cells
(Parasol):
• Coarse detection, motion, B&W, large
receptive fields
P cells
Ganglion Cells
(Midget):
• Details, colour, small receptive fields
Receptive Field is __
• Area of visual space where a neuron maximally fires
Ganglion cells have ___ receptive fields which are good for ___
center-surround structure
- Well suited for detecting contrasts, like edges or borders
- On-center, off-surround vs. off-center, onsurround
Retna to brain pathway
• Contralateral organization of visual pathways
• Information from right visual field is directed to the primary visual cortex of the left hemisphere, and vice versa
(Not the right eye!)
Tectopulvinar pathway __
senitive to __
imput from __
Orientation of ___
Retina -> superior colliculus -> pulvinar nuclei -> visual cortex
- Sensitive to motion and novelty
- Receives input from M cells
- 10 % of optic fibers
- Orientation of peripheral stimuli
- Eye movement
Geniculostriate pathway
senitive to __
imput from __
Retina -> Lateral Geniculate Nucleus -> V1
• 90% of optic nerves
- Sensitive to colour and fine-grained detail
- Receives input from P and M cells
LGN
layers __
The Lateral Geniculate Nucleus
has six layers: receives inputs from both eyes
(but from the same visual field)
- Ipsilateral eye projects to layers 2, 3, 5
- Contralateral eye projects to layers 1, 4, 6
Ipsilateral eye projects to layers
2 3 5
Contralateral eye projects to layers
1 4 6
Layers 1 and 2 of LGN
Magnocellular layers
- Receive inputs from M ganglion cells in retina
- Primarily input from rods
- Large cells (magno = big)
Layers 3-6 og LGN
Parvocellular layers
Receive inputs from P ganglion cells in retina
- Primarily input from cones
- Small cells (parvo = small)
Retinotopic Map
Spatial layout of information from the retina is preserved along the geniculostriate pathway
Two paths within LGN
Magnocellular Pathway and Parvocellular Pathway
Magnocellular Pathway
- Colour-insensitive
- Large receptive fields
- Fast, transient
- More sensitive at low contrast/ low spatial frequency
MOTION
Parvocellular Pathway
- Colour-sensitive
- Small receptive fields
- Slow, sustained
• More sensitive at high contrast/ high spatial frequency
OBJECT RECONITION
Primary Visual Cortex ( ) Computes __
__ stop
__ intergration
(V1)
Computes simple features such as (Orientation • Ocular dominance • Spatial location • Colour • Spatial frequency)
- First stop in cortex
- Binocular integration
Representations in V1
Receptive Fields are __
_ detect location and orientation
_detect orientation
_ detect orientation and length
RFs are not just spots of light, but now bars in different orientations
• Simple cells detect location and orientation
• Complex cells detect orientation (no on/off
regions)
• Hyper-complex cells detect orientation and
length
Simple cells detect
Location and Orenration
Complex Cells organize
orientation (no on/off regions)
Hyper complex cells detect
orientation and length
Organization of V1
Hypercollums and Subcollums
Hypercolumns
groups of cells tuned to respond to stimulation at a certain spatial location
Subcolumns for
specific orientations and input from different eyes
higher up you go in (visual) processing __
Neuronal preferences grow increasingly more complex
Receptive fields increase in size
Subcolumns (in V1)
for specific orientations and input from different eyes
Contextual modulation
Activity of a neuron in visual cortex for a certain stimulus can be modulated based on what surrounds the stimulus
Figure/ground segregation
a cell will respond more strongly to its preferred stimulus when it is part of the figure than the background
Blindsight is __
due to__
- Variant of cortical blindness • Due to extensive damage to V1
- Some patients show preservation of visual discernment • However, they are not aware they can ‘see’
V1 Nessaey For
conscious visual awareness
Ventral visual stream
The WHAT path
- Processing of complex objects
- Selective responses for certain objects
Must solve problems of Ventral stream
- Scale invariance
- Orientation
- Brightness (light/dark)
Must solve problems of Doral stream
• Spatial relations • Motion perception
Dorsal visual stream
WHERE
• Tracks objects as they move • Spatial perception and action
Testing invariance of recognition
Reconsize as same thing dsipire varing formats
- Form-cue invariance
- Adaptation: reduction of activity due to repetition
Adaptation
reduction of activity due to repetition
Role of LOC in invariance
(Lateral occipital cortex) -reconizes shape of object but not depth
seems to reconize invarance is a certine type of way
identical - lower pattern of activity
Damage to parietal lobe impairs
spatial tasks
Damage to temporal lobe impairs
object discrimination
Double dissociation
weather functions are independent
Lessioning studies and Landmark discrimination task & Object discrimination task
Damage to the ventral stream causes
Visual agnosia
Apperceptive agnosia
• Problem forming percepts
• Can perceive parts but not meaningful whole
• Cannot see integrated object (integrative visual
agnosia)
- Varying degrees of perceptual problems (depending on extent of lesion)
- Deficit in copying forms • Trouble integrating parts into a whole • Problems with perceptual constancy
Damage to the ventral stream
Associative agnosia
Associative agnosia
• Can perceive meaningful whole but not link to knowledge
- Problem accessing semantic information
- Can see integrated object but don’t know what it is
Can copy complex objects but cannot identify them
• Perceptual grouping intact
Can copy objects but cannot recall from memory
differences in activity for spatial task
inferior parietal
differences in activity for object change
lateral occipital areas
Apperceptive agnosia damage
Diffuse damage across occipital regions
Associative agnosia damage
Damage at border of occipital and temporal regions
Optic ataxia
lack of coordination between visual input and hand movements
(Damage to the dorsal stream)
- Recognition of objects but cannot use that info to guide actions
- Can see objects, but cannot reach for them
Paitent DF and card slot
lateral ocipital lesion
Extrastriate areas include
- Extrastriate body area (EBA)
- Parahippocampal place area (PPA)
- Visual word form area (VWFA)
- Lateral occipital cortex (LOC)
- Fusiform face area (FFA)
Prosopagnosia is __
intact __
result of __
- Inability to perceive individual faces
- Can perceive other objects
- Intact semantic information
- Can process holistically aside from faces
- Can be result of damage to fusiform face area (FFA) • Either right or bilateral
Is the FFA only for faces?
No
FFA shows sensitivity to objects that one has expertise with
• Greebles!
• Parts of greebles have fixed spatial
relationships
