Higher Visual Areas & The NCC Flashcards
What does the extrastriate cortex contain?
It contains at lease four separate visual areas
What has future research identified in the association cortex?
It’s physiological properties which are divided up into fields of common functionality
What is a connection between two cortical areas considered to be?
Ascending or forward if axons predominantly terminate in layer 4
What does a descending/feedback connection entail?
The axons avoid layer 4, targeting the upper layers instead and, on occasion, layer 6.
What is a key characteristic of the termination zone of axons?
Their function to feeding back information from a higher to a lower level is wider than that of forward projecting neurons, making excitatory synaptic contacts
What are lateral connections?
Where cortical areas are coupled at the same level in the hierarchy
How can the hierarchal organisation chart be described?
It holds dozens of levels that resemble a maze of steam pipes in an old industrial plant, highly intricate, with myriad bypass, shortcuts, and seemingly random additions
How many areas of the cortex have been reported so far?
1/3
What does the top of the hierarchal figure represent?
Either outside the cortex proper or onto regions in the frontal part of the brain and from there to the motor structures that execute the brain’s commands
What does every cortical area do?
Send it’s axon outputs out somewhere
What is research uncertain of in terms of the connections between inferior temporal, posterior parietal, and prefrontal cortical regions?
The uncertainty of whether forward and feedback cortico-cortical projections can be identified in the front of the brain
What is important to note about visual stimuli?
All areas at any one level are not simultaneously excited by visual stimuli
Where do temporal differences remain evident in regards to cellular stream flow into V1?
In the further processing stages, such that the frontal eye fields in the front of the brain receive visual information prior to areas V2 and V4 at the back
What is the net-wave?
The rapid increase in stimulus-triggered spiking propagates through the stations along the visual hierarchy without appreciably changing the steepness of the wave’s leading edge
What is the detection of a net-wave deep in the cortex?
It’s detected with a jitter of 10 msec or less
What is the argument surrounding forward travelling net-wave?
It can rapidly trigger quite complex, yet unconscious, behaviour, while consciousness depends on some sort of standing wave between the back and the front of the cortex
Where are all sensory modalities relayed through?
The thalamus on the way to the cortex
What is the structure of the thalamus?
It is subdivided into discrete nuclei, each with their own, separate input and output channels and unique functional correlates
What is the largest nucleus?
Pulvinar
What is the structure of the primate pulvinar?
It is partitioned into four divisions with at least three separate visual maps
What is an example of engaging the switching capacity of the thalamic region?
Staring intently at foliage because you might have seen somebody hiding there or scanning the road ahead of you
How do core cells operate?
They aggregate in clusters and target precisely delineated recipient zones in the intermediate layers of cortical regions
Where to matrix projection cells reach?
In a more diffuse manner into the superficial layers of several adjacent cortical areas
What is the role of the matrix?
Might help assemble the widespread neuronal coalitions that mediate the multi-faceted aspects of any conscious percept
How is the primary forward response modulated?
Through mediation of some of the observable nonclassical receptive field effect via feedback from the middle temporal cortex to V1
What are forward projections thought as?
Strong, driving connections
What does feedback modulate?
The response of recipient cells, setting the magnitude of the neuronal response
What is the rule for weaker, modulatory connections?
A thalamic input into layer 4 or the lower part of layer 3 is usually a strong connection
What is the key emerging conclusion when considering the connections in the brain as binary?
There appear to be no strong loops in the cortico-thalamic system meaning there are no thalamic or cortical areas that are directly or indirectly, recurrently connected via strong projections
What do strong reciprocal connections promote?
Uncontrollable oscillations such as epilepsy
What is an example of a key experiment in visual abilities?
The visual abilities of monkeys with inferotemporal lesions were compared against those with destruction of their posterior parietal cortex
What has the data from neurological patients with focal brain damage concluded?
That IT contains circuitry specialised for the discrimination and recognition of objects while PP is necessary for computing spatial relationships to guide the eyes or a limb to a target.
What is another name for the ventral and dorsal streams respectively?
Vision for perception AND vision for action pathways
Where do the cross linkages for the ventral and dorsal streams lie?
At the interface between the two pathways
What belongs to the frontal lobes?
Motor, pre-motor, prefrontal & anterior cingulate cortices