📗 -> 04/23/25: NPB163-L8
✒️ -> Scratch Notes
Motion Processing: MT/MST
MT neurons initially (Early) encode a local direction (1 specific neuron favors one specific direction).
The stained (time averaged) response will have the same global motion direction regardless of local directio.
- This could be either caused by feedback from a ‘higher’ area or a local circuit
Response in V2
At this level, even if things are outside of its receptive fields, it still picks up on larger contexts (contours, and can be tricked with illusory contours). We see a trend towards trying to continue edges/forms (Gestalt continuation at a small scale)
- cool research by Peterhans & von der Heydt (1989)
“It has a receptive field, but it is somehow modulated by everything else”
- Either a very large receptive field, or modulation by object context from other neurons
- Seemingly the later
Border Ownership:
Most vigorous firing when “border belongs to an object that is on the same side of the RF”.
- Review?
- Seemingly, fire more when outside the border than inside. I dont know if the above agrees
Not only curious about what’s inside the RF (receptive field) but what’s outside the RF too
V4
Color Constancy
Cells in early parts of the visual system tend to respond to the spectral composition of the incident light (relative darkness/lightness in your environment).
Cells in V4 are different, relatively insensitive (give rise to blue/gold dress debate)
- Shown experimentally with Kusonki et al. (2006). Monkey experiment where decision about cue color influenced by relative environment color
- IE, perception of color is relative at this level. Depends heavily on color context and environment
IT
Inferior Temporal (IT) Cortex
- One of the higher processing areas
- “Towards object recognition”
Shape selective IT monkey neuron: - This neuron fires to specific shapes regardless of size.
- Largely identical activation even if outside of RF
Specific neurons can even be viewing angle-independent (rotate the objects ie)
Fusiform Face Area (FFA) is in the IT cortex.
This area can also be identified in monkey and single unit recordings confirm the selectivity of individual neurons to face stimuli
Discussion
The sensory brain area has a retinotopic map, with a place code to transmit the origin of important stimulus
Negative responses not transmitted:
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the negative portion of edges not transmitted. Cant tell if there is a thin stim or a uniform edge apart
- Off center would transmit (negative on ‘on’ would be positive on ‘off’).
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Answer:
- Neurons use a place code, highest value signal most important. If there is a large negative signal (a dark spot), we would not pick it up.
- We need off-center cells to transmit this
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