20-22 Association Cortices, Memory and Emotion Flashcards
Define Association Cortices
everything in the cortex that isn’t primary motor, sensory or visual cortices.
It’s associated with higher cognitive functions than simply processing sensory info and motor output
describe the structure of the cortex
a 6 layered laminal structures with outputs/inputs to/from other cortical layers at the more superficial layers and subcortical at deeper layers
Discuss Brodmann’s work
Brodmann stained the cell bodies of the cortex and found that different cortical areas had different laminal architecture e.g. some layers thicker than others. From these findings, he mapped each region based on it’s cytoarchitectonic (cytoarchitecture) each with its own number- these are brodmann’s areas. It turned out that a lot of these structural subdivisions also marked functional subdivision e.g. brodmann’s area 17 is what we know as the primary visual cortex etc.
what are 2 key uses of Brodmann’s area?
- in comparative neuroscience- comparing brains of species by looking at their Brodmann’s areas gives insight in to how structure and function have developed.
- also useful in discovering unknowns e.g. certain Brodmann’s areas are yet to be functionally mapped and if we can see an area being preferentially activated by a task it furthers our insight
draw a diagram of the connectivity of the association cortex with other regions
look in notes/lecture slides
what is the primary function of parietal association cortex
understanding where things are in space- visuospatial
what is the primary function of the temporal association cortex
object recognition
what is a key symptom of parietal lesion?
visuospatial neglect
describe visuospatial neglect
when a person is unable to attend to one half of the visual field e.g. if asked to draw a house they would draw one half or if asked to draw a clock they’d put all the numbers on one side
they are not aware they are neglecting an area of visual world
describe left and right parietal visuospatial processing
the right parietal lobe is dominant hence does most of the visuospatial processing and this is bilateral, across both left and right visual field. The left is non-dominant so generally just processes the right visual field
what happens if there is a right parietal lesion?
the person will likely suffer visuospatial neglect, mostly on their left visuospatial attendance
what happens if there’s a left parietal lesion?
the person is unlikely to suffer from visuospatial neglect as the right parietal lobe is dominant and can compensate for the loss of left
how using PET scans has parietal laterality been evidenced
PET scans have shown increased activity in both sides of parietal lobe when person is attending to their right visual image, whereas only increased activity in right when attending to left visual space
describe the temporal association cortices role in object identification
fMRI scans have indicated an increase in activity of different regions of temporal cortex depending on the type of object they are identifying, for example the fusiform face area (FFA) has been found to be active when looking at faces
what can happen when FFA is lesioned
this can result in propagnosia or even autopropagnosia. Propagnosia is an inability to recognise faces, but can often be compesated for using other cues. Autopropagnosia is the inability to recognise your own face e.g. in a mirror.
describe macaque’s facial recognition regions
macaques have a region called middle face patch which is homologous with the FFA in humans
describe what the case of Phineas Gage tells us about frontal lobe association cortex function
Phineas Gage was a railroad worker involved in an accident where an iron bar travelled through his skull, lesioning a large amount of his frontal cortex. Despite surviving, a change in behaviour was indicated afterwards including social problems, impulsivity and aggression, which hadn’t been reported before the accident.
This indicates that social rules and control of behaviour may be among the roles of the frontal cortex.
Describe the Wisconsin Card Sorting Test
A set of cards with varying colours, shapes and numbers of shapes on. The participant is given the cards and asked to sort them, they are not told how but are told whether they sorted them correctly (e.g. if the hidden rule is by colour and they sort them like this). The hidden rule is then changed and the participant must adapt their sorting to try and work it out and so on
how have frontal cortex lesion patients performed on the Wisconsin Card test?
some patients are unable to learn the rule in the first place. Others may learn the initial rule, however they may show preservation where they cannot adapt to the new rule and continue to follow the original rule
describe electrophysiology in non-human primate parietal cortex
monkeys have an electrode inserted and are asked to tap a bar upon the appearance of certain visual targets on the screen and are rewarded with juice.
They found that different neurons are preferentially responding to different regions in the visuospatial world. They also found an increase in firing rate if the reward is bigger.
This indicates the role in visuospatial processing and how it can vary with attention.
describe electrophysiology in non-human primate temporal cortex
when electrodes are placed in monkey’s inferior temporal cortex, where the face area is, they found neurons that respond to a variety of faces at varying orientations and features etc. They also figured out which parts of the face were required for it to be perceived as a face, e.g. still perceived with mouth blanked out but when eyes were moved down, response reduced.
This led to the idea that there is topography of object representation across the parietal area e.g. different bands of activity depending on face orientation.
describe electrophysiology in humans looking at temporal cortex
recordings were done on humans shown a high frequency selection of image stimuli and seeing when and which neurons found. Researchers found a neuron that fired for the celebrity Jennifer Anniston preferentially. This led to the question of the grandmother neuron- whether we have a specific neuron for specific people, although this is unlikely, more likely that neurons may fire at different patterns/amounts/ locations for associated faces.
describe electrophysiology in non-human primate frontal cortex
electrode placed in monkey dorsolateral prefrontal cortex. Monkeys performing delayed response tasks- where they have a number of bowls in front of them and a food morsel is placed in one, a screen goes down so the monkey can’t see for a delay and all bowls are covered. The monkey gets one chance to select the correct bowl. This was 90% accurate it healthy monkeys. they saw a neuron which increased in firing during the delay when there was the presence of a food morsel, no when there was not. This exhibits the role of PFC in planning.
Which brain region has long been associated with LTP?
the hippocampus
