Lecture. 23

Question 1

What is the function of the superficial layers of the superior colliculus?

Answer 1

The superficial layers of the superior colliculus receive information from retinal ganglion cells and form a retinotopically coded map of the visual field.

Question 2

What are the response characteristics of neurons in deeper layers of the superior colliculus?

Answer 2

Neurons in deeper layers of the superior colliculus have movement fields, and they are involved in controlling eye movements.

Question 3

What type of cells were recorded from in the experiment involving monkeys and electromyography (EMG)?

Answer 3

Neurons in deeper layers of the superior colliculus were recorded from.

Question 4

What does the activity of cells in deeper layers of the superior colliculus indicate about eye movements?

Answer 4

The activity of these cells occurs before and/or during eye movements, even in total darkness, suggesting their involvement in eye movement control.

Question 5

Do neurons in deeper layers of the superior colliculus have visual receptive fields?

Answer 5

No, these neurons do not have visual receptive fields.

Question 6

What capabilities do neurons in deeper layers of the superior colliculus exhibit in response to visual stimulation?

Answer 6

Neurons in deeper layers can have visuomotor or pure motor capabilities in response to visual stimulation.

Question 7

How is the superior colliculus anatomically organized?

Answer 7

The superior colliculus has a layered anatomical organization, with superficial layers containing retinotopic maps and deeper layers containing a motor map.

Question 8

What did the single case study involving a patient with unilateral SC damage reveal about saccades?

Answer 8

The latencies of reflexive saccades were asymmetrical, with contralesional saccades (leftward) being delayed, suggesting the importance of the superior colliculus in generating rapid eye movements.

Question 9

What are reflexive eye movements, and what triggers them?

Answer 9

Reflexive eye movements are rapid eye movements triggered by sudden visual changes in the periphery.

Question 10

What pathway is involved in triggering reflexive eye movements?

Answer 10

Visual information projects through the retinotectal pathway to the superior colliculus, which then initiates eye movements to foveate the visual change.

Question 11

What is the role of cells in deeper layers of the superior colliculus during saccades?

Answer 11

These cells discharge during saccades, and the organization of these cells represents the amplitude of eye movements.

Question 12

What are fixation cells, and where are they located in the superior colliculus?

Answer 12

Fixation cells are located in the rostral portion of the superior colliculus and are activated when a stimulus is present at fixation.

Question 13

What is the fixation reflex, and what triggers it?

Answer 13

The fixation reflex is triggered by an external visual stimulus projecting onto central vision, and it involves the activation of fixation cells in the superior colliculus.

Question 14

How do eye movements and fixation relate to each other behaviorally?

Answer 14

Behaviorally, eye movements (saccades) and fixation are opponent processes.

Question 15

What happens to the activity of fixation cells when a stimulus is present at fixation?

Answer 15

The presence of a stimulus at fixation activates fixation cells and inhibits the activity of saccade cells.

Question 16

In the Fixation Offset Effect Paradigm, what is the independent variable being manipulated?

Answer 16

The independent variable is whether the fixation stimulus remains present (fixation overlap) or disappears (fixation offset) when the target appears.

Question 17

How does mutual inhibition between fixation and saccade cells in the superior colliculus relate to the Fixation Offset Effect?

Answer 17

Mutual inhibition between fixation and saccade cells results in different reaction times (RTs) for eye movements in fixation overlap and fixation offset conditions, with the FOE measuring the responsiveness of the fixation reflex.

Question 18

What does a large Fixation Offset Effect (FOE) indicate, and what does it suggest about the fixation reflex?

Answer 18

A large FOE indicates a strong fixation reflex, suggesting that the superior colliculus plays a significant role in the responsiveness of the fixation reflex.