Talk:Saccade

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Changed rotational velocity based on http://www.cns.nyu.edu/~glimcher/PUBLICATIONS/abstracts/mitecs.html

Right now, article (and that ref above) suggests max velocity 1000 degrees/second. Brazis suggests that the maximal angular velocity achieved in long saccades is 700 degrees per second (see PPRF for complete reference). Does anyone know which is correct? I lean towards Brazis in most cases. -Ikkyu2 22:04, 28 January 2006 (UTC)

[edit] repetition error

"The duration of a saccade depends on its amplitude. The amplitude of a saccade is the angular distance that the eye needs to travel during the movement. For amplitudes up to about 60 degrees, the duration of a saccade linearly depends on the amplitude. In that range, the peak velocity of a saccade linearly depends on the amplitude." revphil 69.30.67.169 17:29, 25 July 2006 (UTC)

[edit] doesn't make sense

"The duration of a saccade depends on its amplitude. The amplitude of a saccade is the angular distance that the eye needs to travel during the movement. For amplitudes up to about 60 degrees, the duration of a saccade linearly depends on the amplitude. In that range, the peak velocity of a saccade linearly depends on the amplitude. In saccades larger than 60 degrees, the peak velocity remains constant at the maximum velocity attainable by the eye. Thus, the duration of these large saccades is no longer linearly dependent on the amplitude.

I'm confused about this section. If the peak velocity depends on the amplitude, then how is it that the duration of the saccade scales linearly with amplitude? For constant acceleration, one expects the duration to scale like the root of the amplitude. Also, if the peak velocity is constant (as it is for large amplitude excursions), one expects duration to scale linearly with amplitude. —The preceding unsigned comment was added by 205.175.123.22 (talk) 20:04, 10 April 2007 (UTC).

[edit] Police use of saccades for roadside sobriety tests

(I hope someone will "wikify" this comment for me!) I wonder if anyone knows more about this than I do - I once read that the "follow the light with your eyes" test performed (at least in the US) in roadside sobriety tests is actually to observe the changes brought about in saccade increments (ie, how many degrees in each jump) by the drying of bodily tissues due to alcohol consumption? If they do, it would be a great addition to this article, I think. human 23:32, 10 October 2005 (UTC)

They're looking for ocular dysmetria and nystagmus, effects of alcohol on the flocconodular lobe of the cerebellum. Ocular dysmetria is obviously saccade-related. -Ikkyu2 22:04, 28 January 2006 (UTC)

[edit] Maybe we should add some...

I don't know anything about wikifying the subject or anything about saccade, but I noticed in the first paragraph they say that saccades can be in the eyes, head, or other part of the body or of device, but in the article they only talk about a saccade of the eye. It is all very interesting, but needs some more about the other kinds.

[edit] Merge Saccadic movement into this article?

Since the article Saccade specifically mentions saccadic eye movements I think that article Saccadic movement should be merged into this, with a redirect for Saccadic movement. Shenme 20:41, 30 December 2005 (UTC)

This is the entire text of Saccadic movement. I'd've merged it, but I'm not sure how best to incorporate it, or if it's necessary. I'm just redirecting it now.
Saccadic movement is the act of quickly placing an object within view on the fovea, the central part of the retina.
NickelShoe 18:34, 10 January 2006 (UTC)

[edit] Comparative physiology

I thought I'd add a note on the following, which made the front cover of Nature 15 years ago: Nature. 1990 Jan 25;343(6256):362-3. Needs formatting.

Saccadic oscillations facilitate ocular perfusion from the avian pecten.

Pettigrew JD, Wallman J, Wildsoet CF.

THE evolution of the eye is constrained by two conflicting requirements--good vascular perfusion of the retina, and an optical path through the retina that is unobstructed by blood vessels. Birds are interesting in that they have higher metabolic rates and thicker retinas than mammals, but have no retinal blood vessels. Nutrients and oxygen must thus reach the neurons of the inner retina either from the choroid through 300 micron of metabolically very active retina, or from the pecten, a pleated vascular structure protruding from the head of the optic nerve into the vitreous chamber, and more than a centimetre away from some retinal neurons. Despite the diffusional distance involved, several lines of evidence indicate that the pecten is the primary source of nutrients for the inner retina: the presence of an oxygen gradient from pecten to retina, the large surface area produced by macroscopic folds and by microscopic infoldings of the luminal and external surfaces of the capillary endothelium, extrusion of circulating fluorescein, high content of carbonic anhydrase and alkaline phosphatase, and retinal impairments after pecten ablation. Another peculiarity of birds, their saccadic oscillations, occur with a large cyclotor-sional component during every saccadic eye movement. In different species, saccades, which occur at intervals of 0.5-40 s, have up to 13 oscillations with frequencies of 15-30 Hz and amplia-tudes of about 10 degrees. Therefore, as much as 12% of some birds' total viewing time may be subject to the image instability caused by the oscillations. Using fluorescein angiography, we show here that during every saccade, the pecten acts as an agitator which propels perfusate towards the central retina much more effectively than is observed during intersaccadic intervals. Jellytussle 03:49, 5 January 2006 (UTC)

[edit] Shift in frequency definition

I've never heard, nor have a handful of dictionaries, of saccade meaning a shift in frequency -- could it be sourced? -- Metahacker 18:10, 11 July 2006 (UTC)

[edit] Purpose of microsaccades?

This article mentions microsaccades (and links to the microsaccades article). This article states that without microsaccades, the image would fade quickly. However, the microsaccade article says that their purpose is still "highly debated", and the article presents a couple of different possibilities. Should the wording in this article be toned down? - netjeff 00:23, 9 September 2006 (UTC)


Functions of fixational saccades, also called microsaccades, are indeed under intense investigation and highly debated. However, I believe that "microsaccades" mentioned in this article are in fact referring to ocular microtremor (see Ocular_microtremor) and thus have to be renamed accordingly.

- Mucioh 02:24, 9 July 2007 (UTC)

[edit] How to relate to the average Wikipedian?

I agree that this is an interesting article that deserves more explanation. I'm wondering what happens / how long it takes for my eye to "jump" from the last word of one line to the first word on the following line, and if someone can quantify this in everyday terms that we average mortals can understand. This could make the Saccadasiacal experience easier for the average person to relate to. --Torchpratt 16:13, 10 April 2007 (UTC)

[edit] Express Saccades

I've struck upon the mentioning of "express saccades", but couldn't understand them yet. Are they too belong to the "Saccade" article? If yes, please include the description and explanation. Best regards, CopperKettle 16:29, 21 April 2007 (UTC) PubMed has 154 articles on express saccades, many are of recent dates; see also free fulltext 1993 article: Fischer, B. & Weber, H. (1993). Express saccades and visual attention. Behavioral and Brain Sciences 16 (3): 553-610. CopperKettle 16:58, 21 April 2007 (UTC)

[edit] Microsaccade amplitudes

The Wikipedia entry on "Microsaccade" claims that "Microsaccade amplitudes vary from 2 to 120 arcminutes". This is very different from "... microsaccades are tiny movements, roughly 20 arcseconds in excursion ..." presented in this entry. What are the correct values? JL1971 20:23, 20 August 2007 (UTC)

[edit] Inaccuracies deleted

It was claimed that only the fovea

...has a high concentration of color sensitive photoreceptor cells called cone cells."

This is true, but is a partial truth. The fovea has a high concentration of M and L cones in particular, which is key for resolving objects. The foveola, consisting of the central area in the eye, contains half of all M and L cones--and no S cones (and no rods). S cones only appear outside the foveola, and increase in frequency the further away you go (there's a very good reason for this, having to do with the sensitivity curves, and how it relates to chromatic abberation).

"The rest of the retina is mainly made up of monochrome photoreceptor cells called rod cells,"

Since there are about 100 million rods in the eye, but only 6 million cones, this is technically true. However, for the same reason, it's highly misleading. Again, the S cones, which play a key role in the blue-yellow opponent process for color vision, appear mainly in these areas of the eye.

"which are especially good for motion detection."

...and this is just a plane mistake. Rods play no role in vision in any moderately lighted scene. Rods are easily saturated, and once saturated, they are completely useless. So unless you are in low light conditions, they play no role in vision.

The rest was snipped just to make the edit read a bit better.

[edit] Animation/Video

Would it be informative to find a video or animation of saccadic eye movement? Would anyone be able to find such a resource? Ged3000 (talk) 19:06, 19 May 2008 (UTC)