The aim of this thesis was to investigate how visual information is organised in
perceptual short term memory, with special interest in colour, spatial frequency
and velocity. Previous studies of VSTM have indicated the existence of specific
memory mechanisms for visual attributes such as orientation, spatial frequency,
velocity, contrast and colour. The retention of information in visual short term
memory for these basic visual attributes can be disrupted by the presentation of
masking stimuli during inter-stimulus intervals (ISIs), which are outside the
range of traditional sensory masking. We exploited this memory masking effect
in order to examine the organisation of visual information in VSTM. Four groups
of experiments were conducted in which participants carried out a delayed
discrimination paradigm that employed a two-alternative forced choice (2-AFC)
procedure in conjunction with a method of constant stimuli. The fidelity of VSTM
was measured by performance markers such as discrimination thresholds and
point of subjective equalities. We have found selective memory masking effects,
which serve as further evidence in favour of the modular organisation in VSTM,
namely, that human visual perceptual memory is based upon multiple, tuned
channels in case of colour, spatial frequency and speed, similar to those found
in the earliest stages of visual processing for spatial frequency. Moreover, each
of these storage mechanisms are tuned to a relatively narrow range of stimulus
parameters that are closely linked to visual discrimination mechanisms. These
findings add further support to the view that low-level sensory processing
mechanisms form the basis for the retention of colour, spatial frequency and
velocity information in perceptual memory. We also found evidence for the
broad range of transfer of memory masking effects across spatial location,
which indicates more long range, long duration interactions between channels
that are likely to rely upon contributions from neural processes located in higher
visual areas. In conclusion, the experiments presented in this thesis provide
significant insight into the organization of visual information in perceptual short
term memory. / Federation of Ophthalmic and Dispensing Opticians
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/5695 |
| Date | January 2011 |
| Creators | Nemes, Vanda A. |
| Contributors | McKeefry, Declan J., Bloj, Marina |
| Publisher | University of Bradford, School of Optometry and Vision Science |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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