Editing Iconic memory (section)

== Components ==
The two main components of iconic memory are ''visible persistence'' and ''informational persistence''.  The first is a relatively brief (150 ms) pre-categorical visual representation of the physical image created by the sensory system.  This would be the "snapshot" of what the individual is looking at and perceiving. The second component is a longer-lasting memory store which represents a coded version of the visual image into post-categorical information. This would be the "raw data" that is taken in and processed by the brain. A third component may also be considered which is ''neural persistence'': the physical activity and recordings of the [[visual system]].<ref name = "Coltheart"/><ref>{{cite journal|last=Loftus|first=Geoffrey|author2=T. Bursey|author3=J. Senders|year=1992|title=On the time course of perceptual information that results from a brief visual presentation|url=http://faculty.washington.edu/gloftus/Downloads/LoftusDuncanGehrig.pdf|journal=Journal of Experimental Psychology|volume=18|issue=2|pages=535–554|doi=10.1037/0096-1523.18.2.530|pmid=1593234 }}<!--| access-date = 2011-03-11--></ref> Neural persistence is generally represented by neuroscientific techniques such as [[EEG]] and [[fMRI]].

===Visible persistence===
Visible persistence is the phenomenal impression that a visual image remains present after its physical offset.  This can be considered a by-product of neural persistence. Visible persistence is more sensitive to the physical parameters of the stimulus than informational persistence which is reflected in its two key properties.:<ref name="Coltheart">{{cite journal|last=Coltheart|first=Max|year=1980|title=Iconic memory and visible persistence|journal=Perception & Psychophysics|volume=27|issue=3|pages=183–228|doi=10.3758/BF03204258|pmid=6992093 |doi-access=free}}<!--| access-date = 2011-03-08 --></ref> 
#The duration of visible persistence is inversely related to stimulus duration.  This means that the longer the physical stimulus is presented for, the faster the visual image decays in memory.
#The duration of visible persistence is inversely related to stimulus [[luminance]]. When the luminance, or brightness of a stimulus is increased, the duration of visible persistence decreases.<ref name="Dick">{{cite journal|last=Dick|first=A. O.|year=1974|title=Iconic memory and its relation to perceptual processing and other memory mechanisms|journal=Perception & Psychophysics|volume=16|issue=3|pages=575–596|doi=10.3758/BF03198590|doi-access=free}}<!--| access-date = 2011-03-08 --></ref> Due to the involvement of the neural system, visible persistence is highly dependent on the physiology of the photoreceptors and activation of different cell types in the [[visual cortex]].  This visible representation is subject to masking effects whereby the presentation of interfering stimulus during, or immediately after stimulus offset interferes with one's ability to remember the stimulus.<ref name="Long">{{cite journal|last=Long|first=Gerald|year=1980|title=Iconic Memory: A Review and Critique of the Study of Short-Term Visual Storage|journal=Psychological Bulletin|volume=88|issue=3|pages=785–820|doi=10.1037/0033-2909.88.3.785|pmid=7003642}}<!--| access-date = 2011-03-08 --></ref>
Different techniques have been used to attempt to identify the duration of visible persistence.  The '''Duration of Stimulus Technique''' is one in which a probe stimulus (auditory "click") is presented simultaneously with the onset, and on a separate trial, with the offset of a visual display. The difference represents the duration of the visible store which was found to be approximately 100-200 ms.<ref name = "Long"/> Alternatively, the '''Phenomenal Continuity''' and '''Moving Slit Technique''' estimated visible persistence to be 300 ms.<ref>{{cite journal|last=Haber|first=R.|author2=L. Standing|year=1970|title=Direct measures of visual short-term visual storage|journal=Quarterly Journal of Experimental Psychology|volume=21|issue=1|pages=216–229|doi=10.1080/14640746908400193|pmid=5777982|s2cid=23042735 }}<!--| access-date = 2011-03-20 --></ref> In the first paradigm, an image is presented discontinuously with blank periods in between presentations.  If the duration is short enough, the participant will perceive a continuous image.  Similarly, the Moving Slit Technique is also based on the participant observing a continuous image.  Only instead of flashing the entire stimulus on and off, only a very narrow portion or "slit" of the image is displayed.  When the slit is oscillated at the correct speed, a complete image is viewed.

====Neural basis====
Underlying visible persistence is neural persistence of the visual sensory pathway. A prolonged visual representation begins with activation of photoreceptors in the [[retina]].  Although activation in both [[rod cell|rods]] and [[cone cell|cones]] has been found to persist beyond the physical offset of a stimulus, the rod system persists longer than cones.<ref name = "Book">{{cite book | last1 = Irwin | first1 = David | last2 = Thomas | first2 = Laura | title = Visual Memory | chapter = Neural Basis of Sensory Memory |editor1= Steven Luck |editor2=Andrew Hollingworth | publisher = Oxford University Press | year = 2008 | location = New York, New York | pages = 32–35 | isbn = 978-0-19-530548-7}}</ref> Other cells involved in a sustained visible image include M and P [[retinal ganglion cells]]. M cells (transient cells), are active only during stimulus onset and stimulus offset.  P cells (sustained cells), show continuous activity during stimulus onset, duration, and offset.<ref name = "Book"/><ref>{{cite journal | title = Responses of cat retinal ganglion cells to brief flashes of light | journal = Journal of Physiology | year = 1970 | first = W. | last = Levick |author2=J. Zacks | volume = 206 | pages = 677–700| pmid = 5498512 | issue = 3 | pmc = 1348672| doi = 10.1113/jphysiol.1970.sp009037 }}</ref> Cortical persistence of the visual image has been found in the primary visual cortex (V1) in the [[occipital lobe]] which is responsible for processing visual information.<ref name = "Book"/><ref name = "Nikolic">{{cite journal|last=Nikolić|first=Danko |author2=S. Häusler |author3=W. Singer |author4=W. Maass|title=Distributed fading memory for stimulus properties in the primary visual cortex|journal=PLOS Biology|year=2009|volume=7|doi=10.1371/journal.pbio.1000260|editor1-last=Victor|editor1-first=Jonathan D.|issue=12|pages=e1000260|pmid=20027205|pmc=2785877 |doi-access=free }}</ref>

===Informational persistence===
Information persistence represents the ''information'' about a stimulus that persists after its physical offset. It is ''[[wiktionary:visual|visual]]'' in nature, but not ''[[wiktionary:visible|visible]].''<ref name="Irwin">{{cite journal|last=Irwin|first=David|author2=James Yeomans|year=1986|title=Sensory Registration and Informational Persistence|journal=Journal of Experimental Psychology: Human Perception and Performance|volume=12|issue=3|pages=343–360|citeseerx=10.1.1.278.6648|doi=10.1037/0096-1523.12.3.343|pmid=2943863 }}<!--| access-date = 2011-03-08 --></ref> Sperling's experiments were a test of informational persistence.<ref name="Coltheart"/> Stimulus duration is the key contributing factor to the duration of informational persistence.  As stimulus duration increases, so does the duration of the visual code.<ref name="Greene">{{cite journal|last=Greene|first=Ernest|year=2007|title=Information persistence in the integration of partial cues for object recognition|journal=Perception & Psychophysics|volume=69|issue=5|pages=772–784|doi=10.3758/BF03193778|pmid=17929699 |doi-access=free}}<!--| access-date = 2011-03-11 --></ref> The non-visual components represented by informational persistence include the abstract characteristics of the image, as well as its spatial location. Due to the nature of informational persistence, unlike visible persistence, it is immune to masking effects.<ref name = "Long"/>  The characteristics of this component of iconic memory suggest that it plays the key role in representing a post-categorical memory store for which VSTM can access information for consolidation.<ref name = "Irwin"/> [[Image:Ventral-dorsal streams.svg|thumb|right|200px|The dorsal stream (green) and ventral stream (purple) are shown. They originate from a common source in visual cortex]]

====Neural basis====
Although less research exists regarding the neural representation of informational persistence compared to visible persistence, new electrophysiological techniques have begun to reveal cortical areas involved. Unlike visible persistence, informational persistence is thought to rely on higher-level visual areas beyond the visual cortex.  The anterior [[superior temporal sulcus]] (STS), a part of the [[ventral stream]], was found to be active in macaques during iconic memory tasks.{{Citation needed|date=November 2016}} This brain region is associated with [[object recognition]] and object identity. Iconic memory's role in change detection has been related to activation in the middle occipital gyrus (MOG).  MOG activation was found to persist for approximately 2000ms suggesting a possibility that iconic memory has a longer duration than what was currently thought. Iconic memory is also influenced by genetics and proteins produced in the brain. [[Brain-derived neurotrophic factor]] (BDNF) is a part of the [[neurotrophin]] family of nerve growth factors.  Individuals with mutations to the BDNF gene which codes for BDNF have been shown to have shortened, less stable informational persistence.<ref>{{cite journal|last=Beste|first=Christian|author2=Daniel Schneider|author3=Jörg Epplen|author4=Larissa Arning|date=Feb 2011|title=The functional BDNF Val66Met polymorphism affects functions of pre-attentive visual sensory memory processes|journal=Neuropharmacology|volume=60|issue=2–3|pages=467–471|doi=10.1016/j.neuropharm.2010.10.028|pmid=21056046|s2cid=14522722 }}<!--| access-date = 2011-03-19 --></ref>