LECTURE 1

Question 1

Describe the response properties of magno- and parvocellular LGN neurons.

Answer 1

Magnocellular Neurons:
Highly sensitive to high-speed motion
Low spatial resolution
High contrast sensitivity: up until 50% contrast
colorblind
Transient response pattern

Parvocellular Neurons:
Higher spatial resolution
Color-sensitive: Red-Green
Lower contrast sensitivity: more monotonic increase of response signal can detect small differences even for high contrast lights.
Sustained response pattern

Question 2

What are the behavioral effects of inactivations of the parvo- and magnocellular layers of the LGN in the macaque?

Answer 2

Parvocellular Layer Inactivation:
Impaired color vision
Fine spatial processing deficits: reduced spatial acuity.
Spatial frequency problem

Magnocellular Layer Inactivation:
Motion perception deficits: Impairments in perceiving and tracking moving stimuli.
Temporal frequency problem

Question 3

What is a retinotopic map?

Answer 3

Retinotopy is the mapping of visual input from the retina to neurons, particularly those neurons within the visual stream.

Question 4

Discuss the functional organization of primate V1 and V2.

Answer 4

V1 (Primary Visual Cortex):

Orientation selectivity:

Columnar organization: V1 exhibits a columnar structure, with vertical columns of neurons that share similar functional properties, such as receptive field properties and orientation preference.

V2 (Secondary Visual Cortex):
Higher-level feature processing:

Contour integration

Columnar organization: Like V1, V2 also exhibits a columnar organization, with columns that process different visual features.

Question 5

Discuss the response selectivity’s of single neurons along the different areas of the macaque ventral visual stream

Answer 5

V1 (Primary Visual Cortex):
Orientation selectivity:
Spatial frequency selectivity
Act like spatial Gabor filters

V2 (Secondary Visual Cortex):
Selectivity for complex form features: V2 neurons exhibit preferences for complex form features such as curves, angles, and junctions, allowing for the detection and discrimination of object boundaries.
Size and position selectivity:

V4:
Local shape sensitivity: cells are doing Local shape feature analysis like: 2 dimension degree of curvature and orientation of segment
Bigger receptive field v1, v2

inferior Temporal Cortex (IT):
Object selectivity: IT neurons are highly selective for complex visual objects, responding to specific shapes, objects, or object categories.
Face selectivity: A subset of IT neurons responds selectively to faces, aiding in face perception and recognition.

Question 6

Discuss the representation of objects by inferior temporal cortical neurons.

Answer 6

We still don’t know exactly what they represent but. Cell responds to feature that is less complex than complete object but more complex than features in V2 or V1. (Moderately complex feature). Single object is coded by combined activity of several neurons. A single neuron contributes to the coding of many objects.