LECTURE EIGHT Flashcards
REPRESENTATION
Internal model linked to external stimuli or information
2 POSSIBILITIES OF MENTAL REPRESENTATION
- Analog
- Propositional
ANALOG
Sensory
PROPOSITIONAL
Symbolic.
PROPOSITIONAL REPRESENTATION
- Abstract assertions that maintain relationship of referent
- Not tied to a particular sensory modality
- Symbolic representation
ANALOG REPRESENTATION
- Representation has same relationships as properties of referent
- Tied to sensory modality (in this case, visual)
- Non-symbolic representation
PROPOSITIONAL VS ANALOG
- Core idea here is either concepts are represented using symbolic propositional representations or coded in analog sensory modality
- How can we design experiments to tease these two possibilities apart?
STUDY NAVIGATE THE ISLAND
DO IT
MENTAL ROTATION
First scientific investigation into imagery
* Are the two objects in (a) identical or mirror
images? What about (b)
* Response time varies linearly as a function of
degree of rotation!
- Imaging data shows increased activation alongside
increased rotation (and note location – visual
cortex!)
(BASICALLY this showed that the amount of rotation applied to the object and the response time were linear, if rotation was more, participants took longer: They’re mentally rotating the image in their head)
IMAGERY VS REALITY
- Relative size and imagery
VISUALIZATION
- Using imagination to simulate a task
- “Visualize success”
- It actually works!
- Imagination can be highly reflective of reality
- We are very good at predicting outcomes of actions
- Adjust behavior based on prediction
MENTAL MUSCLE BUILDING
- Groups
- ABD – imagine finger abduction exercises (flexing pinky)
- ELB – imagine elbow flexion
- Control group
- Actual muscle movement groups for ABD
- Mental training groups improved strength over
control, but less than actual movement group (35% vs.
53%) - Imagery resulted in ERP increase in finger, stimulating muscle growth
MYTH OF IMAGELESS THOUGHT
Myth: Thought is separate from vision.
* Truth: Thought relies on the visual system and mental
imagery.
* Final example
* Eye movements during imagery tasks
* But there are still some important differences between imagery and perception
APHANTASIA
Lack (or extreme impoverishment) of willed visual imagery
BINOCULAR RIVALRY TASKS
- Have participants visualize one half of binocular rivalry
stimulus - Measure how frequently the imagined part is first seen /dominates visual perception when stimulus presented
- Those with aphantasia do not show priming effect of imagery
*Positive correlation found between strength of
fMRI signal in visual cortex and self-reported
vividness of mental image
PUPILLARY RESPONSE
Pupil constricts in response to brightness, dilates in response to darkness.
* Pupillary light response occurs when presented with visual stimuli, but also…
* When imagining concepts involving varying levels of
brightness
* However, same response is not seen amongst those with aphantasia!
* Aphantasics here recruited through self-selected convenience sample (posted recruitment flyer)
* Validated using binocular rivalry task
INNER SPEECH
- Speaking to yourself; talking to yourself
- Can be more or less “grammatical” and complete
- Some people report little, if any, inner speech
INNER MONOLOGUE
- Narration of own life and life events
- Associated with the default mode network in the brain
- Some people report little, if any, inner monologue
APHANTASIA FINDINGS
- Aphantasia can be congenital or acquired
- Mostly anecdotal at this point (reddit) with one clear case of aphantasia follow surgery
- This patient could do mental rotation – but RT not related to degree of rotation!
- Some reports of acquired aphantasia related to trauma
- Case studies suggest…
- Impaired verbal working memory when task is challenging, but no same impairment on pure imagery task
- Deficits in autobiographical (episodic) memory
- Sustained benefits to imagery after ingesting ayahuasca (DMT) in someone with acquired aphantasia
- No benefits to imagery (even during intoxication) after
ingesting DMT in someone with congenital aphantasia
HYPERPHANTASIA
Super vivid imagination that affects the senses and daily life
DANGERS OF INNNER MONOLOGUE AND SPEECH
- Dehumanization and extreme (justified) polarization
- The specific metaphor here has to do with video games and NPC characters – no agency
- If someone has no agency, no mind, no will, no soul…well I’ll let you connect the dots here on how this can be a problem
INNER MONOLOGUE/SPEECH ASSOCIATED WITH
- High “default mode network” activity
- Greater likelihood of auditory hallucinations
- Rumination, shame, and perfectionism
- Anxiety and depression
- Anecdotal reports that inner monologue becomes more noticeable (and negative) during depressive episodes
DEFAULT MODE NETWORK
- Strong connectivity between pre-frontal cortex,
posterior cingulate cortex, and angular gyrus - Active during “rest” in fMRI
- Associated with thought, autobiographical memory
analysis, reflection, and many tasks involving some sort
of introspection; basically, the “ego” - “Default” brain activity is that of mind-wandering,
introspection, prospective thinking, depressive rumination, insomnia… - Reduction in DMN activity and connectivity is associated with the opposite, “living in the
moment”, “being present”, “quieting the mind”
REDUCING DMN
Meditation is associated with reduction in DMN activity
* Meditation also associated with improvement in a whole host of negative mental outcomes (e.g., depression, anxiety…)
* Exercise is associated with reduction in DMN activity
* Obesity associated with INCREASE in DMN activity – exercise brings back to baseline
* Exercise also associated with improvement in negative mental health
* Psychedelic states are associated with increased
connectivity throughout the brain and corresponding
inhibition of DMN activity
* Psychedelic therapy being investigated (with very promising results) for treating same mental pathologies
* Subjective reports of “ego-death” and loss of self correlates with DMN inhibition
