Section III: Synesthesia

Synesthesia

Experiencing sensory information that is not physically associated with a stimulus and that is consistently and automatically evoked by this stimulus.

What is the most common type of synesthesia?

Color-grapheme synesthesia

T/F: The stimuli can consist of letters, numbers, musical notes, words, categories, objects

True

T/F: Synesthesia is typically unidirectional

True

What are the two different comparison for two types of synesthesia?

Projectors vs. Associators and Lower vs. Higher

Projectors vs. Associators

“Out in space” (seeing letter and seeing colors) vs. “Minds eye” (feels colors but doesn’t physically see them)

Most research is done on (projectors/associators)

Projectors

Lower vs. Higher

Lower Perceptual Stage (actually perceiving color) vs. Higher Perceptual Stage (recognition and memory based associations)

Incongruent Stimuli for Color-Grapheme Synesthetes

When the physical color of a grapheme doesn’t match with the perceived color of the grapheme.

Name Photism

Naming the perceived color of a stimuli

T/F: Saying the color that is associated with a stimuli (naming photism) is an automatic process.

True

What region of the brain is related to color processing?

V4 region of the visual cortex

T/F: Color-grapheme synesthetes had similar associations from letter to color as did a control group.

True

Automatic Processes

Fast, involuntary, uncontrollable, high practiced, unconscious

What type of sensory metaphor is most common in literature? How does this relate to automatic learned associations?

Hearing » touch metaphors. This is not a very common type of synesthesia, so it doesn’t support the theory that synesthesia is actually due to automatically learned associations.

Cross-Activation/Cross-Wiring Hypothesis (Ramachandran)

• There are excess neural connections that resist neural pruning with age

• Prenatal connections have been found between inferior temporal regions (word processing( and V4(color processing)

• Color-grapheme synesthesia is common because visual word processing lies adjacent to the color processing area of the brain

Rather than synesthesia resulting from learned linguistic associations, it actually causes these linguistic associations.

Disinhibited Feedback Hypothesis

Results from feedback loops between high levels of visual processing and a brain region that combines multiple sources of sensory information, that now erroneously provides incorrect feedback to lower regions that were not activated by the relevant sensors and should have been inhibited from being activated.

Across-Modality Synesthesia

When synesthesia begins with one sense and relates to another: ex. noise » color (auditory » visual)

It was found that there’s increased connectivity between the inferior parietal cortex and the auditory cortex and between the inferior parietal cortex and the visual cortex for sound » color synesthetes. However, there’s no increased connectivity between primary auditory and visual sensory sites. Which hypothesis does this support?

Disinhibited Feedback Hypothesis

Which hypothesis is related to the idea that because two areas of the brain are close together, that can be a factor leading to synesthesia?

Cross-Wiring Hypothesis

Characteristics of Consciousness (4)

(i) Subjective (phenomenal) experience

(ii) Binding of multiple sources of information

(iii) Self-awareness

(iv) Volition (executive) intentions

T/F: Consciousness involves integrating information in the global workspace from several special-purpose processors (networks) working unconsciously and independently.

True

What four networks bring in information to the global neuronal workspace model?

Evaluative Systems (Values), Long-term Memory (Past), Attentional Systems (Focusing), Perceptual Systems (Present)

What comes out of the global neuronal workspace model?

Motor Systems (Future)

Conscious

High strength and high attention

Preconscious

High strength and no attention

Subliminal

Weak strength

Which explanation for synesthesia explains the altered consciousness resulting from synesthesia?

Disinhibited Feedback Explanation

Binocular Rivalry

Present two images, one to each eye, and flip images randomly

Global Workspace Model

Consciousness involves integrating information in the global workspace from several special purpose processors working unconsciously and independently

Subliminal

Just below conscious awareness, present stimulus and mask over top of it

Attention

Facilitates what’s in our focus and inhibits what’s in the background.

Photism

The perception of colors

T/F: All sensory inducers have been found to produce synesthesia

False; for example, temperature doesn’t induce synesthesia

Why are bistable figures used to study consciousness?

The viewer will automatically switch from one conscious percept to the other and back again. By signaling this transition to the researcher, this allows researchers to examine what happens in the brain during these different conscious representations.

Negative Priming

A phenomenon