Imagery - 2

imagery seems like

a weaker form of perception

Second debate is

Does brain processes involved in mental imagery similar to the brain process involved in perception?

EX: can you scan mental images with your attention, just

like you would scan real image (perception), if so, does it scan both in a similar way?

Stephen Kosslyn did an experiment to

answer the question above

stephen kosslyn is

mental imagery researcher

The boat pic experiment

Ask participants to focus on the anchor in a boat picture both mentally (memories image) and physically (real image) then answer questions about motor (far away from the anchor)

Kosslyn suggests that answering

questions about motor takes you longer bc it’s far away from where your focus is (the anchor), you have to move your spatial attention over a long distance. (both in mental pic and real pic)

Results

the farther away the object of interest is, the longer it takes to answer questions about it for both mental image and real image

Kosslyn concluded

You can scan mental image with your attention, just like you scan a real image (perception) [in a similar way]

This suggest that imagery and perception

may have similar brain mechanism

Third big question is “Does imagery make use of the ‘neural machinery’ that’s

normally used for real image?”

EX: do you imagine images with your

visual cortex using visual neurons

2 types of experiments will help us reveal the answer

Don’t directly measure the brain activity and directly measure

Don’t directly measure the brain activity: Salmon Sticker did an experiment based on

introspection

Salmon Sticker experiment relies on the principle that

if 2 cognitive functions both use overlapping brain processes, then these phenomena often interfere with each other

Salmon Sticker experiment asked

2 questions

do imagined movement and actual movements engage in

overlapping brain process?

If so, making actual movements should interfere with

making imagined movements

2 condition of the experiment; 1st is to

imagine a movement (ex: making ‘F’ sound)

2 condition of the experiment; 2nd is to

imagine that movement again (making ‘F’ sound), while making an actual movement (shape your mouth like pronouncing ‘O’ sound)

Result:

2nd condition is harder so concluded that imaging and doing an action seem to involve in overlapping brain processes

Don’t directly measure the brain activity: neglect patient

can’t pay attention to the left side of the scene (when the right side of parietal lobe is affected)

The question for this experiment is: does attention to mental images involved

brain areas that overlap with those involved in attention to real visual space?

if the question above is correct → then neglect patient should have trouble

paying attention to the left side of their mental images as well as the real visual space

The experiment in the plaza found that

When the Neglect patients are imaging the scene of a plaza, they can only report out the right side of the scene (like what they see in real life)

So brain processes involved in mental imagery

overlap with those involved in actual vision

Directly measure the brain activity:

Visual cortex

recall the topographic of visual cortex: different parts of visual space (eyes, nose, mouth on face) are

represented at different anatomical locations in the visual cortex

Back of the visual cortex represents

the center of your visual field (nose, eye)

Front of the visual cortex represents

the periphery of your visual field (neck, chin)

Stephen Kosslyn did another experiment using the topographic idea

Asked participant to imagine visual field (small, medium, large), while using FMRI to measure activity in their visual cortex

Results: small mental image get signal only in

the back of visual cortex cuz involve only the center visual field

Results: medium mental image

intermediate

Results: large mental image get signal only in

the front of visual cortex cuz involve only the periphery visual field

Kosslyn conclude that

mental image does seem to involve visual cortex with similar topographic organization like perception

All the example so far emphasizes: in the brain, imagining thing is

similar to real perception