Session 8 - Lecture 1 - Higher Cortical Function Flashcards
2 - Contents
- The cerebral cortex
• Fine structure
• Functions of various lobes – what we can learn from lesions
• Functions of the cortex as a whole - Lateralisation of cortical structure and function
• Dominant and non-dominant hemispheres
• Language – aphasias - Commissural connections
• Corpus callosum and split brain patients
- Memory • Types of memory • Encoding and consolidation of memories – the hippocampus • Long term potentiation • Amnesia
{1. detail of CC not a major topic in this unit but will talk about input and output – don’t really understand how it works tbh.
1b. did in H&N but also add more functions on.
1c. and in dementia.
2. So far in the nervous system we have seen the CNS as being symmetrical, but as we get higher up the cortical (neuronal) axis we get higher up the hemispheres, we see more asymmetry. Knowing about asymmetry tells us where certain lesions are.
2b. asymmetry when it comes to language – ultimate expression of cerebral asymmetry.
3a. the big one is corpus callosum connecting the two halves.
4. how it works
4b. how to be a good memoriser of stuff.}
3 - Fine structure of the cortex
Fine structure of the cortex
Most INPUTS are from thalamus and other cortical areas
Most OUTPUTS are from pyramidal cells and project to widespread areas
Information is processed in the complex synaptic
network found between input and outputs
{Cerebral cortex - H&N - We talked about the basic concept of the CNS as a neural network; a network composed of gazillions of interconnections between individual neurones, and by altering the strengths of those individual connections we can get it do interesting things and amazing things E.g. has the power to recognise faces.
Bottom right image – computer image depicting brain but the brain isn’t this neat.
Middle image – drawing of a photo micrograph of the brain – Spanish neuroanatomist Santiago Cajal - first person to really study the nervous system. Whathe saw when he used a particular staining method was a complex web within cerebral cortex. The staining method he used only stained less than 1 in 10 neurons – so you look at that image in the middle, think man that’s complicated – but in reality it’s 10x more complex than what you see! And no wonder is it how our behaviours arise from interrelations of neurones in the nervous system.
Left IMG: Only in the last 100 years do we really know about the functional layers of the cortex. What we now know is the human cerebral cortex has 6 distinct histological layers within the cortex, major output cells of CC are pyramidal neurones, (cell body pyramid shaped). So in red, we have the pyramidal neurones. They exist in many layers, and what is not appreciated from this diagram is they have extensive dendritic trees – so most of what you can see in the histological image (middle) are dendrites you’re looking at – where inputs are coming in to pyramidal cells. If you look vey closely at the middle image, you can see the little spines – knobbly outgrowths on the dendrites – each of these spines represents a single synapse. So one pyramidal neurone can have 100s of 1000s of synapses converging on it. These neurones on their own are tremendously complex computational devices. They are constantly summating the excitatory and inhibitory inputs coming in. Pyramidal cells are UMN, so UMN cell bodies are themselves pyramidal neurones.
Major source of input to the cerebral cortex is 2-fold; in fact the most prominent input to the cortex is itself; it has a lot of recurrent projections; inputs coming back onto itself. You know that from your own introspection - because you can close your eyes and without any sensory input you can create your own thoughts in your head – bc own cerebral cortex can provide its own inputs – it’s a living thing. Also, major input is the thalamus – the blue & green represents ascending inputs – major input to cortex are 3rd order neurons coming from the sensory system by the thalamus.
As a system as a whole, we can reduce everything we do to 3 components: sensory input from the thalamus gets processed somehow within the cortex and output from pyramidal cells leading to our behaviour. That is all that we are.}
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