Tut 4 Completly done !!! Flashcards
Name the 4 steps of the Central visual pathway:
- The image in the retina is reversed from right to left compared to the visual field
- At the optic chiasm
- axons from the temporal (Outer eyeball) halfes of the retina continue in the optic trac on the same side
- axons from the nasal (inner nose) halves cross the optic trac on the opposite side - Most axon in the optic tract end in the lateral geniculate nucleus and a few in the superior colliculus (contolling eye movement)
- Trough out the optic radiations axons carry information between lateral geniculate and striate cortex
Name everything regarding the lateral geniculate Nucleus:
- We have 2 LGN one on each hemisphere
- ipsilateral eye receives imput from 2,3,5
- contralateral eye receives imput from 1,4,6
- LGN is located in the thalamus ( 6 layer structure )
- receives input and output of ganglion cells
- Layer 1-2 from magnocelluar
- Layer 3-6 from parvocellular ganglion cell
- koniocellular cells/layer Divide the LGN
What is the function of magnocellular cells?
- mostly input from M ganglion cell
- Respond to larger fast moving object
- But at the end they receive from both cell
- input from peripheral area
What is the function of parvocellular cells?
- mostly imput from P ganglion cell
- Responsible for processing details of not moving ojects
- But at the end they receive from both cells
- input from fovea
Name the properties of the receptive field:
- Selective responsiveness
- Orientation Tuning
What is selective responsiveness ?
- individual neuron respond more intensively to specific stimuli then others its receptive field
What is orientation Tuning ?
- tendency to respond optimally to certain orientations (horizontal/vertical) and less to others (schräg) oblique stimulis
What is the function of a simple cortical cells ?
- Have side by side receptive fields
- response depends on orientation tuning curve
- On /off center cell but presented as bars = elongated
- edge detectors Highly
have specific region for fireing (fields)
What is the function of a complex cell ?
- not clearly defined excitatory and inhibitory region (respond best to moving objects)
- move detectors
(light field just has to be moved and not hit a particular sport) - responds regardless of specific location of the stripe as long as it is in the receptive field
Define endstoped/hypercomplex cells:
Addition to complex cells or single complex cortical cells
- which add specification of length of a stimuli
- so the neruon fires best at a certain length of stimui if to long then activation stops.
Describe the visual ventral pathway:
- The ‘‘What’’ pathway
- responsible for determining object’s identity
- Goes from the p ganglion cells of the retina towards the LGN into the V1 (fourth layer) and then to the inferior temporal cortex.
Describe the visual dorsal pathway:
- where pathway
- responsible for determining object’s location
- Goes from M ganglion cells of the retina towards the LGN into the V1 (fourth layer) and then to the posterior parietal cortex.
Describe the correlation between both pathways:
- Humans need both to identify and locate objects
- They are conacted but work independently
- Bipolar exchange does not only go up but also down
- Dorsal and ventral streams each receive inputs from both magno and parvo pathways
What is the method called to identfy if to functions operate together:
Double dissociations
Explain double dissociations:
Definition: it helps to determine whether two functions operate independently from one another.
- First person damage in area A and area B is fine and second person virsa versa then compare them to see what is the difference in each.
Explain single dissociations:
is when a manipulation leaves one cognitive function (say, A) intact whils severing another (say, B). This indicates the functions A and B are at least partially independent.
What is visual agnosia ?
- Unable to recognize or describe common objects, faces, pictures
- Damage in occipital/temporal lobe
What is optic ataxia ?
- Damage to parietal lobe
- Unable to locate or grab objects
Name the two different collumns and define them:
cortex is organized in
1. Location columns: are vertical to the surface of the cortex
- All neuron inside the location column have their receptive field identical structured compared to the retina
where something is located
2. Orienation columns:
- Neighbouring columns have cells with slightly different preferred orientations
What is a Hypercolumn ?
- Structure of the cortex
A column that includes one set of all possible orientations columns (so 0-180 degree - And it contains ocular columns which means that a hypercolumn is divided in two half where on region gets input of one eye and the other from the other eye.
What is Retinotopy in the LGN ? (in general called Topographical mapping)
- Neighbouring locations in the visual field correspond to neighbouring cells in the retina, LGN and V1
- Nearby points on the cortex receive signals from nearby locations in the retina
What is the ice cube model regarding hypercollumn:
- Each hypercolumn:
1. Contains a single location column
2. Contains left and right ocular dominance columns
3. Contains a complete set of orientation columns that cover orientations from 0 to 180 degrees - They also contain
1. Blobs :Groups of neurons that are sensitive to colour (layer 2 and 3)
2. Interblobs: The area between blobs, sensitive to edge
What is cortical Magnification regarding the cortex:
In the cortex the area representing cones activity is much larger because it is way more accurate then rods.
What is selective rearing:
- Use it or lose it
- Neuorn which are more often used function better
- neuron which are less used get lost do to purning
What does selective adaption mean ?
- If neurons fire to long they eventualy become fatigued
- which means they fire less to same stimuli over time u get used to it
Name the function of the Fusiform face area:
- FFA
- specialized to respond to faces
- located below the inferior temporal cortex
- damage to prosopognosia
Name the function of extrastriate body area
- EBA
- activated by pictures of bodies and parts of bodies
- inferior temporal cortex
Name the function of Visual word form area :
- VWFA
- Activated when we read
