6.18 - Functional Localisation in Brains II: Hierarchical processing Flashcards
What is the where pathway?
The where (or the dorsal) pathway is concerned with the processing of information regarding location and motion.
What is the what pathway?
The what (or the ventral) pathway is concerned with processing the form and identity of visual stimuli.
What is hierarchical processing?
The idea that processing of information proceeds by starting from simple features and assembling more and more complex features.
The what pathway projects from the visual cortex to the _____
temporal lobe
The where pathway projects from the visual cortex to the _____
parietal cortex
Why do neuroscientists believe that functions in the brain are localized?
Because we can find activity correlates of specific functions in particular places in the brain.
What is the main problem the brain must solve?
The brain must somehow translate all the analog nature of the world into one language so that different sensory modalities can be handled together.
State some of the benefits of neural divergence.
(1) Force - amplification of a signal if a downstream neuron has to be activated strongly.
(2) Lateral inhibition - makes lateral inhibition possible by dividing the neural activation into excitatory and inhibitory projections.
(3) Efference copy - enables sending an efference copy - an internal copy of a motor command of its predicted movement.
Why is neural convergence beneficial?
Combining the information/input converging onto a neuron - there may be multiple reasons to move a muscle and all these pieces of information can converge onto a motor neuron to be able to activate the same target muscle.
How are efference copies helpful in motor control?
A motor command sends an efference copy to the predictor (forward model) as well as a signal to the motor effector.
The efference copy then allows for a comparison between the predicted and actual sensory feedback at the comparator. Motor control is adjusted in case of a discrepancy.
Which features are detected during the low-level processing of the visual scene?
(1) orientation of bars
(2) contrast
(3) color
(4) disparity
(5) movement direction
Feature split of the visual input begins at the ______
Lateral geniculate nucleus (LGN)
The two internal layers of the LGN are part of the _______ pathway, while the external four layers are part of the _______ pathway.
magnocellular…..parvocellular
What are the two types of categorizations of neurons in the LGN?
(1) Parvocellular vs Magnocellular
(2) Ipsilateral vs Contralateral projections
(a) Transient response
(b) Fast response
(c) High contrast gain
(d) Low spatial resolution
The above are characteristics of the ______ pathway.
magnocellular
What type of visual dysfunction would the lesion to the right optic nerve (1) cause?
(1) Loss of visual information from the right eye.
(2) Loss of binocular vision (depth perception)
What type of visual dysfunction would the lesion to the optic chiasm (2) cause?
Loss of contralateral projections (ipsilateral still intact)
