Chapter 10 Visual Imagery

What evidence is there that visual imagery and perception us the same areas of the brain( include ERP, fMRI, and neuropsychological data)? What evidence is there that they don't?what could be the explanation for the contradictory data?

-ERPs (event-related potentials) data Electrical response to the stimulus of many thousands of neurons -Results of Farah, et al. (1988) experiment -Greatest activity when making mental images is in same area when seeing (i.e., V1 area of occipital lobe) -Conclusion: imagery is created by same visual system structures responsible for perception. -fMRI data shows that imagery and perception are very close and similar. -Neuropsychological data Patients who have lost the ability to see color through damage to occipital lobe also can't create color through visual imagery. Patients with unilateral neglect ignored same areas in both perception and visual imagery. They not the same area of the brain as well: Double Dissociation -Patient R.M. recognizes objects and can draw them, but unable to draw objects from memory (loss of visual imagery). -Patient C.K. can't recognize objects (visual agnosia) but can draw objects from memory That is because perception is a bottom-up processing and imagery is a top-down processing, They share some but not all things in the brain. R.M. has it damage before the perception so it don't have it store in it's memory. and CK can have damage to its in perception so it doesn't know what it is when it is in front of him but he know it from memory so he can image it in his head what it look like.

What are some differences between visual imagery and perception?

-Perception is more vivid than mental imagery. -Perception occurs automatically, but imagery needs effort. -Perception is stable. Mental imagery is more fragile & can vanish without continued effort. -There is more brain activity in perception than with mental images.

What are the results from Shepard & Metzler's mental rotation experiment, and what does it tell us about visual imagery?

-RT increased with increase in degree of rotation which implies we mentally rotate the objects. -Led researchers to believe we think about mental images much like we think about real images. -Demonstrates parallel between perception & imagery Visual imagery are the same about seeing something in real life.

What evidence is there that visual imagery shares the same mechanisms as perception? (Kosslyn's experiments)

Kosslyn's mental scanning experiments -Map scanning -Mentally travel at same speed as would if eyes scanning map -Evidence for the similarity between imagery & perception -Size in visual field -See details better if imagined object is closer to you -Again suggests that mental imagery works a lot like perception -Mental-walk task -Participants had to move closer to smaller animals than larger animals. -Mental objects fill visual field at same distance a real object would Kosslyn's results suggest that imagery & perception use the same kind of mental processes.

What is it necessary to use the subtraction method when analyzing mental imaging data?

image condition-abstract baseline=brain's response to generating imagery electrical activity when reading & making mental image - electrical activity when reading =electrical activity when making mental image

What is visual imagery?

is "seeing" in the absence of visual input. Applies to other senses too