Chapter 4 Flashcards
Retinotopic Map
- points on the retinal image to cause activity ( visual cortex in occipital lobe)
- fovea has greater representation in the cortex (cortical magnification)
Cortical Magnification
better representation in the cortex
- 0.01% retina —> 8-10% cortex
- fMRI
fMRI
- Functional magnetic resonance imaging
- brain imaging technique
- blood flow will increase activated brain areas
- Hemoglobin protein will carry O2 and contains iron which has magnetic properties
- detects changes in magnetic response of hemoglobin
Visual field when light is near the center
the illuminated will be small (near fovea)
- when interpreting the brain will see it magnified
Visual field when light is far from center
illuminated the large area (near peripheral retina)
Why does the illuminated occur??
- extra cortical space allotted provides extra neural processing
– tasks needing high visual acuity (sharp, focus)
– Ex: painting, driving, fishing, sports - closer to the dot = closer to the fovea
Organization of Neurons
- Functional Organization
- Pathways for information about what and where
Functional Orgzanization
- neurons are organized in terms of their functions
- serve similar functions tend to be connected together into pathways
- organized in a systematic way
Pathways for information about What and Where
- 2 pathways serving different functions
- information transmitted from striate cortex to other areas of brain
- monkeys used to understand organization of the brain
Object Discrimination Task
- monkey sampling, having a delay, then a food reinforcer if matching object correctly
- told to move shape away from the disc
- then to pick the correct shape they had originally seen
- overtime accuracy became worse based on the length of delay
Effects of Ablation of Performance
- Ablation is the damage/removal of the brain
- Temporal and Parietal Lobes are removed separately on different monkeys
Temporal Ablation
- performed worse on task and had a decline in performance reaching chance much faster
Parietal Ablation
- was nearly the same as original testing
The What Pathway
- determining an object’s identity (object determination task)
- visual cortex (striate cortex) –> temporal lobe
- Called ventral pathway (lower part of the brain)
Landmark Discrimination Task
- participant must move the block to indicate where the food is hidden under
Effect of Ablation on Performance (Landmark Task)
- Temporal removed = near close performance as the baseline
- Parietal removed = dramatic decrease in performance and needing to guess
The Where Pathway
- determining an object’s location (landmark task)
- visual cortex (striate cortex) –> Parietal lobe
- dorsal pathway (upper surface of the brain)
For BOTH What and Where Pathways
- origin in the retina (2 types of ganglion cells)
- Retina –> lateral geniculate nucleus (thalamus)
– ganglion cells transmits info to different layers of the thalamus - Serve various functions with interconnections
– need to know and coordinate what and where to function in life - Receive feedback from higher brain areas
– mechanism behind top-down processing (frontal lobe/prefrontal cortex)
Where (dorsal) pathway also is the How or Action pathway
- Neuropsychology: effects of brain damage on behavior in humans
- Patient DF: damage to ventral pathway after gas leak/CO poisoning
– could not judge orientation because of damage to what pathway
Perception vs action in people w/o brain damage
- looking at 2 lines with a background that makes us perceive that one line is longer than the other when in reality the other line is longer
- using length estimation sensors for measurement
- proces illusion in participants
- with grasping, illusion goes away
Different Mechanisms
- perception and action have different mechanisms
- people w/ brain damage
- people w/o brain damage
People with Brain Damage (mechanisms)
- ventral/what pathway damaged –> CANNOT judge orientation but can do an action (mailing letter)
- dorsal/where/how pathway damaged –> CAN judge orientation but cannot do coordinated action (mailing letter)
People without brain damage
- perception (length estimation) involves ventral/what pathway “what the lines are”
- action (grasping) involves dorsal/where/how
Modularity
- specific areas of the cortex that are specialized to respond and process specific types of stimuli
Temporal Cortex Modularity
- Fusiform Face Area (FFA)
- Parahippocampal Place Area (PPA)
- Extrastriate Ara (EBA)
Parahippocampal Place Area
- responds to scenes, indoor/outdoor
- key to this is the spacial layout!
Extrastriate Body Area
- stick figure, body/body parts
- DOESN’T count the face!!!
Distributed Representation
each type of stimulus causes activity in a number of areas
STUDY FOR DR stimuli
Mulitdimensional Stimuli
many different reactions associated with activity in many different places in the brain
Medial Temporal Lobe
Neurons in the hippocampus and other areas of the medial temporal love respond to concepts that stimuli represent
Patient H.M
- didn’t have a hippocampus but could recognize objects, but couldn’t remember them later
- neurons in the hippocampus and areas of the medial temporal lobe, aren’t responsible for seeing stimuli, rather remembering
Experience-Dependent Plasticity
- experience shapes neural firing
- Hypothesis: our proficiency in perceiving certain things can be explained by changes in the brain caused by long exposure, practice, or training
Greebles Study
