Visual short-term memory: Activity supporting encoding and maintenance in retinotopic visual cortex

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• 作者：Markus H. Sneve ; Dag Aln?s ; Tor Endestad ; Mark W. Greenlee ; Svein Magnussen
• 关键词：fMRI ; Low-level vision ; Multi-voxel pattern analysis ; Sensory recruitment ; Working memory
• 刊名：NeuroImage
• 出版年：2012
• 出版时间：15 October, 2012
• 年：2012
• 卷：63
• 期：1
• 页码：166-178
• 全文大小：964 K

文摘

Recent studies have demonstrated that retinotopic cortex maintains information about visual stimuli during retention intervals. However, the process by which transient stimulus-evoked sensory responses are transformed into enduring memory representations is unknown. Here, using fMRI and short-term visual memory tasks optimized for univariate and multivariate analysis approaches, we report differential involvement of human retinotopic areas during memory encoding of the low-level visual feature orientation. All visual areas show weaker responses when memory encoding processes are interrupted, possibly due to effects in orientation-sensitive primary visual cortex (V1) propagating across extrastriate areas. Furthermore, intermediate areas in both dorsal (V3a/b) and ventral (LO1/2) streams are significantly more active during memory encoding compared with non-memory (active and passive) processing of the same stimulus material. These effects in intermediate visual cortex are also observed during memory encoding of a different stimulus feature (spatial frequency), suggesting that these areas are involved in encoding processes on a higher level of representation. Using pattern-classification techniques to probe the representational content in visual cortex during delay periods, we further demonstrate that simply initiating memory encoding is not sufficient to produce long-lasting memory traces. Rather, active maintenance appears to underlie the observed memory-specific patterns of information in retinotopic cortex.