Topographic Contribution of Early Visual Cortex to Short-Term Memory Consolidation: A Transcranial Magnetic Stimulation Study

Abstract

The neural correlates for retention of visual information in visual short-term memory are considered separate from those of sensory encoding. However, recent findings suggest that sensory areas may play a role also in short-term memory. We investigated the functional relevance, spatial specificity, and temporal characteristics of human early visual cortex in the consolidation of capacity-limited topographic visual memory using transcranial magnetic stimulation (TMS). Topographically specific TMS pulses were delivered over lateralized occipital cortex at 100, 200, or 400 ms into the retention phase of a modified change detection task with low or high memory loads. For the high but not the low memory load, we found decreased memory performance for memory trials in the visual field contralateral, but not ipsilateral to the side of TMS, when pulses were delivered at 200 ms into the retention interval. A behavioral version of the TMS experiment, in which a distractor stimulus (memory mask) replaced the TMS pulses, further corroborated these findings. Our findings suggest that retinotopic visual cortex contributes to the short-term consolidation of topographic visual memory during early stages of the retention of visual information. Further, TMS-induced interference decreased the strength (amplitude) of the memory representation, which most strongly affected the high memory load trials.

Neural correlates of spatial working memory manipulation in a sequential Vernier discrimination task

“…Previous findings have shown the contribution of early visual areas to visual memory related to priming [21], short-term memory [22], and working memory [15]. However, in the context of the sequential Vernier, the current findings suggest a more active participation that could be more related to mental imagery, involving a memory re-enactment of the position of the stimuli to verify its alignment [4,[23][24][25].…”

Neural mechanisms of information storage in visual short-term memory

“…Thus, this finding again supports overlap in the mechanisms that support visual perception and visual STM (Silvanto & Cattaneo, 2010). Similarly, TMS over the region of occipital cortex that encodes an array of sample stimuli disrupts encoding and storage in STM, particularly when memory load is high (van de Ven, Jacobs, & Sack, 2012). When combined with other psychophysical and neuroimaging evidence, these data lend causal support for theories that emphasize a common role of early visual areas in supporting perception and in maintaining content-specific information during STM.…”

Working Memory: Maintenance, Updating, and the Realization of Intentions

“…In particular, analyses of fMRI data by means of multivariate "pattern analysis" techniques have revealed that modality-specific regions retain sensory-specific working-memory representations during the delay period (see Sreenivasan et al 2014). Also, if TMS is applied to visual cortex during maintenance of visual information, there is a reduction in the performance of working memory (van de Ven et al 2012). Collectively, these and related studies converge to suggest that the maintenance of working memory does not rely on any specialized storage "buffers," but instead shares the same representational zones as retrieval from longterm memory.…”