W7 - Eye movement and Navigation

Question 1

Why are eye movements important?

Answer 1

They allow fixation and tracking of objects, reading and exploring the environment, and maintaining a stable image on the retina.

Question 2

What are three functions eye movements help with?

Answer 2

Fixating/tracking objects, visual exploration, and stabilising images on the retina.

Question 3

What is diplopia and what causes it?

Answer 3

Diplopia is double vision caused by misalignment of the eyes.

Question 4

What is drift in eye movement?

Answer 4

Drift is a slow, unintended movement of the eyes, as seen in conditions like nystagmus.

Question 5

How can poor saccadic control affect reading?

Answer 5

It may contribute to reading difficulties like dyslexia.

Question 6

Why are eye movements a useful model in neuroscience?

Answer 6

They are mechanically simple, unaffected by gravity, and show principles of sensory maps and cortical-subcortical interactions.

Question 7

Why do we move our eyes? (3 reasons)

Answer 7

To explore visual scenes, to converge the eyes for different distances, and to stabilise images on the retina.

Question 8

What are reafferent signals?

Answer 8

Signals generated from eye movements.

Question 9

What are exafferent signals?

Answer 9

Signals from external/environmental movement.

Question 10

What is gaze stabilisation?

Answer 10

The process of maintaining steady fixation on an object during movement.

Question 11

What are gaze paths in reading?

Answer 11

They represent the spatial pattern of eye movement across text.

Question 12

What do circles on gaze path diagrams show?

Answer 12

Where the gaze was fixated; larger circles mean longer fixation times.

Question 13

How do eyes move when reading?

Answer 13

In saccades—quick jumps between fixation points.

Question 14

Do readers fixate on every word?

Answer 14

No; common words like “and” or “the” are often skipped.

Question 15

What controls eye movements during reading?

Answer 15

Both automatic and context-dependent processes controlled by the CNS.

Question 16

What are the two key reflexes involved in gaze stabilisation?

Answer 16

Optokinetic Reflex (OKR) and Vestibular-Ocular Reflex (VOR).

Question 17

What is the OKR and what does it do?

Answer 17

The Optokinetic Reflex is a slow, vision-based reflex that helps stabilise gaze.

Question 18

What is the VOR and what does it do?

Answer 18

The Vestibular-Ocular Reflex is fast and compensates for head movement.

Question 19

What did Yarbus (1967) show about gaze behaviour?

Answer 19

Eye movements change depending on the question asked, showing gaze is context-driven and volitional.

Question 20

What does Yarbus’ study suggest about eye movement control?

Answer 20

It is both automatic and selectively directed by cognitive processes.

Question 21

What do intra-ocular muscles control?

Answer 21

Pupil diameter (adjust to brightness).

Question 22

What do extra-ocular muscles control?

Answer 22

Movement of the eyeball within the socket.

Question 23

What directions do the extra-ocular muscles move the eye?

Answer 23

Superior–Inferior (up/down), Medial–Lateral (side to side).

Question 24

How are extra-ocular muscles controlled?

Answer 24

By specific cranial nerves.

Question 25

How does the eye behave mechanically?

Answer 25

Like a spring—it naturally returns to the central position.

Question 26

What is the purpose of gaze stabilisation mechanisms?

Answer 26

To keep images stable on the retina, especially during motion.

Question 27

What drives the Optokinetic Reflex (OKR)?

Answer 27

Whole-field motion across the retina, assuming the world is stationary.

Question 28

What does the OKR minimise?

Answer 28

Retinal slip – movement of the image across the retina.

Question 29

What brain areas control OKR?

Answer 29

LGN (visual input), V1 (primary visual cortex), V5/MT (motion processing).

Question 30

What is Optokinetic Nystagmus (OKN)?

Answer 30

Repeated slow drifts and fast saccades in response to moving visual scenes, like watching from a train window.

Question 31

What does an abnormal OKN indicate?

Answer 31

Lesions or vestibular dysfunction.

Question 32

Why is the OKR considered slow?

Answer 32

Because it integrates visual information with brainstem compensation.

Question 33

What is the Vestibular-Ocular Reflex (VOR)?

Answer 33

A fast reflex that stabilises gaze during head movements, driven by vestibular input, not vision.

Question 34

How fast is the VOR?

Answer 34

Approximately 14 milliseconds.

Question 35

How many neurons are involved in the VOR circuit?

Answer 35

Three.

Question 36

What detects head motion in the VOR?

Answer 36

The semicircular canals of the vestibular system.

Question 37

Where do head movement signals go next in the VOR pathway?

Answer 37

The vestibular nucleus.

Question 38

What do oculomotor neurons do in the VOR?

Answer 38

Drive the extra-ocular muscles to adjust eye position.

Question 39

What is the VOR pathway’s key feature?

Answer 39

It crosses the midline and contracts the opposite eye muscles.

Question 40

What is the function of PPH neurons in the VOR?

Answer 40

Maintain eye muscle activation during fixation and relay vestibular input to oculomotor neurons.

Question 41

What type of gaze control are vergence movements responsible for?

Answer 41

Adjusting eye position for near or far objects using opposite-direction movement of both eyes.

Question 42

What are smooth pursuit movements?

Answer 42

Slow, simultaneous movement of both eyes in the same direction to track moving objects.

Question 43

What is an example of smooth pursuit?

Answer 43

Watching a plane in the sky.

Question 44

What controls smooth pursuit?

Answer 44

MT and MST areas using slow visual feedback.

Question 45

What must be suppressed during smooth pursuit?

Answer 45

The OKR.

Question 46

What are saccades?

Answer 46

Rapid eye movements between fixation points, up to 600°/sec.

Question 47

What structure controls the burst of movement in saccades?

Answer 47

Paramedian Pontine Reticular Formation (PPRF).

Question 48

What brain region directs where saccades go?

Answer 48

The Superior Colliculus.

Question 49

Are saccades voluntary or involuntary?

Answer 49

Often involuntary (reflexive).

Question 50

What is the function of the retinotopic map in the superior colliculus?

Answer 50

It represents the visual scene as perceived from the retina.

Question 51

How does the superior colliculus perform sensory-motor transformation?

Answer 51

By integrating visual and auditory inputs into motor commands.

Question 52

What role does the superior colliculus play in orientation?

Answer 52

Directs head and eye movements toward visual or auditory stimuli.

Question 53

How can the superior colliculus generate reflexive eye movements?

Answer 53

Without direct cortical involvement, via LGN input.

Question 54

What do omnipause neurons do?

Answer 54

Inhibit saccades until deactivated to allow new movements.

Question 55

What does turning off omnipause neurons allow?

Answer 55

The PPRF to initiate new eye movements.

Question 56

What is the afferent pathway in eye movement?

Answer 56

Retina → LGN → Superior Colliculus → V1/V5.

Question 57

What is the efferent pathway in eye movement?

Answer 57

Superior Colliculus → Brainstem → Oculomotor Neurons.

Question 58

What do these afferent and efferent pathways achieve?

Answer 58

Direct control over eye position and movement.

Question 59

What are the two key eye movement systems?

Answer 59

Gaze stabilisation (OKR, VOR) and gaze shifting (vergence, smooth pursuit, saccades).

Question 60

What is the role of the superior colliculus overall?

Answer 60

Key brainstem structure for reflexive eye movement and integrating sensory inputs.

Question 61

How are visual and vestibular inputs used together?

Answer 61

To maintain gaze stability during movement.

Question 62

What are the two systems involved in spatial cognition?

Answer 62

Allocentric system and egocentric system.

Question 63

What does the allocentric system code?

Answer 63

Object-to-object relationships (world-centered).

Question 64

What does the egocentric system code?

Answer 64

Self-to-object relationships (body-centered).

Question 65

What brain region supports allocentric navigation?

Answer 65

Hippocampus.

Question 66

What brain region supports egocentric navigation?

Answer 66

Posterior parietal cortex (PPC).

Question 67

What is allocentric representation?

Answer 67

Coding object positions relative to each other, independent of the observer.

Question 68

What brain area encodes allocentric maps?

Answer 68

Hippocampus.

Question 69

What do allocentric maps form the basis for?

Answer 69

Cognitive maps.

Question 70

What happens to hippocampal activity with navigation experience?

Answer 70

It increases.

Question 71

What study showed hippocampal activation in taxi drivers?

Answer 71

Maguire et al. (1997).

Question 72

Which hippocampal region had increased volume in experienced taxi drivers?

Answer 72

Posterior hippocampus.

Question 73

What does hippocampal neurogenesis support?

Answer 73

Learning and memory consolidation.

Question 74

What study showed neurogenesis in adult humans?

Answer 74

Spalding et al. (2013).

Question 75

Where are place cells found?

Answer 75

Dorsal (posterior) hippocampus, especially CA1.

Question 76

What do place cells do?

Answer 76

Fire when the animal is in a specific location.

Question 77

What is a place field?

Answer 77

A region of space that triggers a specific place cell to fire.

Question 78

What do place fields provide?

Answer 78

An internal representation of space (cognitive map).

Question 79

What did Layton (2013) observe in rats?

Answer 79

Reverse replay of place cell activity when rats stopped.

Question 80

What does reverse replay suggest?

Answer 80

A role in learning and memory consolidation.

Question 81

Who provided evidence for spatial tuning in place cells?

Answer 81

Jankowski & Mara (2015).

Question 82

Can place fields change with context?

Answer 82

Yes, they can remap depending on the task or environment.

Question 83

Who showed context-dependent remapping of place fields?

Answer 83

Rennó-Costa & Tort (2017).

Question 84

What does place field remapping demonstrate?

Answer 84

Dynamic adjustment to environmental and task demands.

Question 85

Can place cells form distinct maps for different contexts?

Answer 85

Yes.

Question 86

What brain region provides input to place cells?

Answer 86

Entorhinal cortex.

Question 87

What cells in the entorhinal cortex support spatial coding?

Answer 87

Grid cells.

Question 88

How do grid cells fire?

Answer 88

In a regular, grid-like pattern across space.

Question 89

What do grid cells provide to the brain’s spatial system?

Answer 89

A coordinate framework for cognitive maps.

Question 90

What do grid cells of different scales do?

Answer 90

Combine to help place cells code unique locations.

Question 91

Where do grid cells receive high-level spatial info from?

Answer 91

Neocortex.

Question 92

What studies found grid-like activity in humans?

Answer 92

Jacobs et al. (2013); Doeller et al. (2010).

Question 93

What does Raslau et al. (2014) relate to?

Answer 93

Grid cell contribution to spatial representation.

Question 94

What does the PPC encode in spatial maps?

Answer 94

Position of objects relative to the body.

Question 95

What type of spatial representation is egocentric?

Answer 95

Body-centered.

Question 96

Which brain region supports egocentric coding?

Answer 96

Posterior parietal cortex (PPC).

Question 97

What visual stream is associated with the PPC?

Answer 97

Dorsal stream ("where" pathway).

Question 98

What does the dorsal stream support?

Answer 98

Visual processing for action.

Question 99

What visual stream is associated with object recognition?

Answer 99

Ventral stream ("what" pathway).

Question 100

What does the PPC encode?

Answer 100

Egocentric position of objects for spatial awareness and coordination.

Question 101

What study proposed dorsal/ventral stream distinction?

Answer 101

Mishkin et al. (1983).

Question 102

What does LIP in the PPC encode?

Answer 102

Intended eye movements.

Question 103

What does MIP in the PPC encode?

Answer 103

Reaching and pointing.

Question 104

What does AIP in the PPC encode?

Answer 104

Grasping and tool use.

Question 105

What does VIP in the PPC encode?

Answer 105

Multimodal space and motion around the head.

Question 106

What does the PPC transform sensory signals into?

Answer 106

Motor signals.

Question 107

What does the PPC update during movement?

Answer 107

Egocentric body schema.

Question 108

What is neglect?

Answer 108

Inability to perceive the left side of space, often after right PPC damage.

Question 109

Which PPC hemisphere codes for both left and right space?

Answer 109

Right PPC.

Question 110

Which PPC hemisphere codes only for right space?

Answer 110

Left PPC.

Question 111

What study showed preserved allocentric memory in neglect?

Answer 111

Bisiach (1978), Piazza del Duomo study.

Question 112

What is apraxia?

Answer 112

Difficulty coordinating complex movements.

Question 113

What PPC lesion causes apraxia?

Answer 113

Left PPC damage.

Question 114

What is ideomotor apraxia?

Answer 114

Impaired tool use.

Question 115

What is constructional apraxia?

Answer 115

Inability to arrange objects in space.

Question 116

What is prospective coding?

Answer 116

Coding for future goal locations instead of current position.

Question 117

Where is prospective coding found?

Answer 117

Hippocampus.

Question 118

What did Gauthier et al. (2018) show in rodents?

Answer 118

Place cells tuned to goal location, not current location.

Question 119

Is rodent goal tuning affected by start point or heading direction?

Answer 119

No, it’s independent.

Question 120

What shifts with reward location in hippocampal maps?

Answer 120

Spatial tuning of reward-encoding cells.

Question 121

What study tested prospective coding in humans using VR?

Answer 121

Brown et al. (2016).

Question 122

What did human prospective coding correlate with?

Answer 122

Prefrontal cortex activity.

Question 123

What does this suggest about navigation planning?

Answer 123

Involves top-down control from PFC.

Question 124

What did Muhle-Karbe et al. (2023) show about place cell activity?

Answer 124

It differs with task rule via rate and global remapping.

Question 125

What does hippocampal–PFC interaction support?

Answer 125

Prospective coding and future goal prediction.

Question 126

What is sequential activity in prospective coding?

Answer 126

Place cells fire in a sequence toward a goal.

Question 127

What is parallel coding?

Answer 127

Simultaneous representation of multiple future routes.

Question 128

What is temporal separation in spatial coding?

Answer 128

Current and future locations encoded separately.

Question 129

What does the allocentric system do?

Answer 129

Encodes external space using place and grid cells.

Question 130

What does the egocentric system do?

Answer 130

Encodes space relative to the body in the PPC.

Question 131

What do lesion studies show about spatial coding?

Answer 131

A dissociation between allocentric and egocentric systems.

Question 132

What does the hippocampus do in prospective coding?

Answer 132

Encodes and predicts future goal locations.