Biology subjects

Brady, T. F.

Publications and source records attributed to Brady, T. F..

3 recordsLinked to original sources

bioRxiv2018

Episodic Memory Can Replace Active Storage in Visual Working Memory

Humans have remarkable visual long-term memory abilities, capable of storing thousands of objects with significant detail. However, it remains unknown how such memory is utilized during the short-term maintenance of information. Specifically, if people have a previously encoded memory for an item, how does this affect subsequent working memory for that same item? Here, we demonstrate people can quickly and accurately make use of visual long-term memories and therefore maintain less perceptual information actively in working memory. We assessed how much perceptual information is actively maintained in working memory by measuring neural activity during the delay period of a working memory task using electroencephalography. We find that despite maintaining less perceptual information in working memory when long-term memory representations are available, there is no decrement in memory performance. This suggests under certain circumstances people can dynamically disengage working memory maintenance and instead use long-term memories when available. However, this does not mean participants always utilize long-term memory. In a follow-up experiment, we introduced additional perceptual interference into working memory and found participants actively maintained items in working memory even when they had existing long-term memories available. These results clarify the kinds of conditions under which long-term and working memory operate. Specifically, working memory is engaged when new information is encountered or perceptual interference is high. Visual long-term memory may otherwise be rapidly accessed and utilized in lieu of active perceptual maintenance. These data demonstrate the interactions between working memory and long-term memory are more dynamic and fluid than previously thought.

neuroscience↗

bioRxiv2018

The role of meaning in visual memory: Face-selective brain activity predicts memory for ambiguous face stimuli

How people process images is known to affect memory for those images, but these effects have typically been studied using explicit task instructions to vary encoding. Here, we investigate the effects of intrinsic variation in processing on subsequent memory, testing whether recognizing an ambiguous stimulus as meaningful (as a face vs. as shape blobs) predicts subsequent visual memory even when matching the perceptual features and the encoding strategy between subsequently remembered and subsequently forgotten items. We show that single trial EEG activity can predict whether participants will subsequently remember an ambiguous Mooney face image (e.g., an image that will sometimes be seen as a face and sometimes not be seen as a face). In addition, we show that a classifier trained only to discriminate between whether participants perceive a face vs. non-face can generalize to predict whether an ambiguous image is subsequently remembered. Furthermore, when we examine the N170, an ERP index of face processing, we find that images that elicit larger N170s are more likely to be remembered than those that elicit smaller N170s, even when the exact same image elicited larger or smaller N170s across participants. Thus, images processed as meaningful - in this case as a face-during encoding are better remembered than identical images that are not processed as a face. This provides strong evidence that understanding the meaning of a stimulus during encoding plays a critical role in visual memory.\n\nSignificance StatementIs visual memory inherently visual or does meaning and other conceptual information necessarily play a role even in memory for detailed visual information? Here we show that its easier to remember an image when its processed in a meaningful way -- as indexed by the amount of category-specific brain activity it elicits. In particular, we use single-trial EEG activity to predict whether an image will be subsequently remembered, and show that the main driver of this prediction ability is whether or not an image is seen as meaningful or non-meaningful. This shows that the extent to which an image is processed as meaningful can be used to predict subsequent memory even when controlling for perceptual factors and encoding strategies that typically differ across images.

neuroscience↗

bioRxiv2018

Psychological Scaling Reveals a Single Parameter Framework For Visual Working Memory

Almost all models of visual memory implicitly assume that errors in mnemonic representations are linearly related to distance in stimulus space. Here, we show that neither memory nor perception are appropriately scaled in stimulus space; instead, they are based on a transformed similarity representation that is non-linearly related to stimulus space. This result calls into question a foundational assumption of extant models of visual working memory. Once psychophysical similarity is taken into account, aspects of memory that have been thought to demonstrate a fixed working memory capacity of ~3-4 items and to require fundamentally different representations -- across different stimuli, tasks, and types of memory -- can be parsimoniously explained with a unitary signal detection framework. These results have significant implications for the study of visual memory and lead to a substantial reinterpretation of the relationship between perception, working memory and long-term memory.

neuroscience↗