Masking of spatial frequency in visual memory depends on distal, not retinal, frequency

Spatial frequency discrimination thresholds measured in a two-interval forced choice paradigm are virtually constant across inter-stimulus intervals ranging from 400 to 30,000 msec, demonstrating that an accurate representation of spatial frequency is maintained in short-term memory. This representation can be degraded by briefly flashing a grating during the retention interval, Moreover, this memory masking effect varies with the spatial frequency of tile mask, suggesting that the mechanisms used to store spatial frequency in memory are similar to low-level visual filters, In this paper we replicate those previous findings and extend them by showing (1) that accurate memory for spatial frequency lasts as long as 1 min; (2) that memory masking is based on distal (c/cm), not retinal (c/deg), spatial frequency.