Chapter 3 - Striate Cortex (Part 1) - Neurobiology of Primary Visual Cortex Flashcards
What are simple cells?
A type of neuron in V1 that responds best to a stimulus with a particular orientation in the location of its receptive field
What is a preferred orientation?
The stimulus orientation that tends to produce the strongest response from an orientation-tuned neuron such as a simple cell
What is spike-triggered reverse correlation?
Show random images
- random chance can put image onto cell in preferred orientation, then average results
What is Hubel and Wiesel’s model of the receptive fields from the LGN to V1?
- a simple cell that responds to an oriented bar may receive input from multiple LGN neurons
- If you string a series of LGN cells together, they can form an oriented bar
- You can therefore create a cell tuned to any orientation by stringing together the appropriate cells from the LGN
What do individual simple cells receive input from?
Both ON and OFF LGN cells whose centres are aligned along the axis of each subregion
Is orientation tuning of a simple cell in V1 affected by contrast?
No
- response magnitude will increase
- width of the tuning curve (measured as a half width at half height) does not change
What is population coding?
- encode the pattern of relative responses of a population of differently tuned neurons
- increases sensitivity to stimulus levels beyond what physiology alone permits
What are complex cells?
Neurons in area V1 that respond best to a stimulus of a particular orientation (like simple cells)
How do complex cells differ from simple cells?
Complex cells differ in the variety and location of a stimulus that will generate a response
What are the properties of complex cells?
- non-linear: their output (response) is not proportional to the input (stimulus)
- motion-sensitivity: highly responsive to moving lines anywhere within their receptive field
- position intensity (phase sensitivity): complex cells are not sensitive to the position of a stimulus in their receptive field
- spatial extent: receptive field size of complex cells tends to be larger than that of simple cells
How does the response rate of a cell change as a bar of light moves across its receptive field?
- the response rate of a cell increases as the bar of light enters its receptive field
- the response rate of a cell decreases as the bar of light moves out of its receptive field
What do both layers of the LGN project to?
Layer 4C (beta and alpha) of V1
What do the other layers of V1 mostly contain?
Internal synapses
What is the functional organization of V1 characterized by?
Columns that run vertically through cortical layers
What are cortical columns?
A small volume of tissue that consists of neurons that respond to similar types of stimuli and overlapping receptive fields
