User:Rebekah Hamrick/Sandbox

Akinetopsia, also known as motion blindness, is a disorder in visual perception in which the subject can not perceive motion in his/her visual field, despite being able to see stationary objects without issue. Most of what is known about akinetopsia was learned through LM, a highly studied case in akinetopsia.

Characteristics
Akinetopsia is the inability to perceive motion, despite normal vision otherwise. In akinetopsia, color vision remains intact.

Examples LM described (pouring tea, crossing the street)

Brain Lesions
As in the case of LM, the brain lesion was bilateral and symmetrical on the posterior side of the visual cortex, and at the same time small enough not to affect other visual functions. Some unilateral lesions have been reported to impair motion perception as well.

Transcranial Magnetic Stimulation
Akinetopsia can be been selectively and temporarily induced using transcranial magnetic stimulation (TMS) of the V5 in healthy subjects. 1 cm in diameter of the cortex corresponding in position to human area V5 using TMS.

Timing of visual perception
According to the Two Streams hypothesis...

V5
Also known as visual area MT (middle temporal) Located laterally and ventrally in the occipital lobe, near to the intersection of the ascending limb of the inferior temporal sulcus and the lateral occipital sulcus.

V1
V1 is also known as the primary visual cortex, located in Brodmann area 17

Preprocessing, limits motion vision but does not stop it completely. Some signals reach V5 without passing through V1

Inactivating V1

Inactivating V1 and V5

Case Study: LM
Case Study: LM Most of what we know about akinetopsia, we learned from LM. 43 years old Lesions bilateral and symmetrical, posterior of the visual cortex Maintained minimal motion vision preserved by as function of V1 (explained in the first published paper), as function of "higher" order visual cortical areas which can deal at least to some extent with the processing of motion stimuli, or as functional sparing of V5, i.e. the lesion has not affect the entire V5 in both hemispheres.

Thresholds of motion perception

Following her finger:

Degrees per second:

Rotational: There was no effective treatment, so LM learned to avoid conditions with multiple visual motion stimuli, i.e. by not looking at or fixating them. She developed very efficient coping strategies to do this and nevertheless lived her life.

Case Study: Riddoch's patients (1917)
Riddoch studied multiple soldiers who had been blinded by gunshot wounds during WWI. "I can...confirm his statements that the presence of a moving object may be recognized in which it is not perceived when stationaryand in which its shape cannot be appreciated" First positive evidence for a dissociation of visual perception Knowledge gained

In research
Macaque monkeys have been used in research. In monkeys v5 and v1 are highly connected to each other. 1 cm in diameter of the cortex corresponding in position to human area V5 using TMS

Unanswered questions: (e.g. spared biological motion perception, visually guided motor actions for moving stimuli etc)

Behaviors studied related to motion perception
Speechreading:

Catching objects:

In pop culture
Akinetopsia was mentioned in the TV show House in season 7, episode 3, entitled “Son of a Coma Guy”. When a young man walks into the hospital room, House begins to flash the room lights on and off to induce a seizure. He then throws a bag of potato chips into the young man's face who made no attempt to avoid or catch it. House asks if he wants to see something cool. He then proceeds to stand up, disappear, and does not reappear until he stops moving in front of the man's face. House tells the man he cannot see motion, a condition called akinetopsia, that precedes his seizures.