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Edward K. Vogel, Andrew W. McCollough, Jason A. Fair, Geoffrey F. Woodman; Maintaining visual short-term memory representations across new object onsets. Journal of Vision 2005;5(8):1066. doi: 10.1167/5.8.1066.
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© ARVO (1962-2015); The Authors (2016-present)
The storage capacity of visual short term memory (VSTM) for simple objects is known to be very small (around 3–4 items). This severe capacity limitation necessitates control mechanisms that restrict access to it. These control mechanisms may work to select new relevant items for storage in VSTM, as well as to protect representations currently being maintained in memory from being disrupted by new object onsets. Here, using a sustained event-related potential (ERP) measure of the number of items currently held in VSTM (contralateral delay activity), we examined how new object onsets impacted the maintenance of existing representations in memory. In the first experiment, task-irrelevant probes were briefly presented during the retention interval of a VSTM task. The presence of the probe temporarily disrupted the sustained activity related to maintaining the memory items. This delay activity returned 40 ms later with a loss in amplitude of approximately 20%. These results suggest that under these conditions, orienting attention to a new irrelevant stimulus may temporarily disrupt existing memory representations, but these memories may be quickly regained with some loss in fidelity. In a second experiment, task-relevant memory items were presented during the retention period of a VSTM task and subjects were asked to add or “append” these two new items into memory along with the original two memory items. The amplitude of the contralateral delay activity initially reflected the original memory items (2 items), but 200 ms following the onset of the second set of items the amplitude rose to that equivalent to that of four items presented simultaneously. These results suggest that new objects that are task-relevant may be added to VSTM without causing significant disruption of existing memory representations.
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