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Stephen Emrich, Susanne Ferber; Evidence for the role of visual short-term memory in conscious object recognition. Journal of Vision 2009;9(8):581. doi: 10.1167/9.8.581.
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© ARVO (1962-2015); The Authors (2016-present)
What happens to a visual stimulus when it reaches the severe bottlenecks inherent to the human information processing system and what are the cognitive resources and neural substrates that limit the amount of information that can be consciously perceived?
Previous research has demonstrated that when visual short-term memory (VSTM) resources are fully occupied, there is a decrease in activity in the right temporo-parietal junction (rTPJ), which can result in inattentional blindness to suddenly presented stimuli. As the rTPJ has been implicated in visual neglect, we have previously demonstrated that a high VSTM load leads to impaired recognition performance for objects presented in the left visual field, mimicking the processing deficits of neglect patients.
In the present study, we used fMRI to examine the neural architecture subserving this effect. In other words, how does VSTM load affect areas that support memory, perception, and attention? Under a low (1 item) or high (3 item) VSTM load, pictures of objects were briefly presented to the left and/or right of fixation during the delay period. Under a low memory load, areas that support the maintenance of items in VSTM (superior IPS, inferior IPS, and ventral occipital areas) showed increased activity to bilaterally presented objects, relative to a single object, indicating that these areas had resources available to process additional information. Under a high memory load, however, activity in these memory regions did not continue to increase, as memory capacity had already been exceeded. Interestingly, when VSTM resources reached capacity, object recognition performance suffered. Strikingly, activity in areas that support VSTM maintenance was a better predictor of object identification performance than activity in the object-sensitive lateral occipital complex (LOC). These behavioral and neuroimaging results demonstrate that the availability of visual short-term memory resources may be critical to the conscious identification of object stimuli.
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