The neural basis of precise visual short-term memory for complex recognisable objects

Abstract

Recent evidence suggests that visual short-term memory (VSTM) capacity estimated using simple objects, such as colours and oriented bars, may not generalise well to more naturalistic stimuli. More visual detail can be stored in VSTM when complex, recognisable objects are maintained compared to simple objects. It is not yet known if it is recognisability that enhances memory precision, nor whether maintenance of recognisable objects is achieved with the same network of brain regions supporting maintenance of simple objects.We used a novel stimulus generation method to parametrically warp photographic images along a continuum, allowing separate estimation of the precision of memory representations and the number of items retained. The stimulus generation method was also designed to create unrecognisable, though perceptually matched, stimuli, to investigate the impact of recognisability on VSTM. We adapted the widely-used change detection and continuous report paradigms for use with complex, photographic images.Across three functional magnetic resonance imaging (fMRI) experiments, we demonstrated greater precision for recognisable objects in VSTM compared to unrecognisable objects. This clear behavioural advantage was not the result of recruitment of additional brain regions, or of stronger mean activity within the core network.Representational similarity analysis revealed greater variability across item repetitions in the representations of recognisable, compared to unrecognisable complex objects. We therefore propose that a richer range of neural representations support VSTM for complex recognisable objects.

Aging and feature-binding in visual working memory: The role of verbal rehearsal.

“…Similar perceptual 'overwriting' processes have been observed in other studies (Enns & Di Lollo, 2000;Lakha & Wright, 2004, see also Logie, 1995;Phillips & Christie, 1977;Wilson, Scott, & Power, 1987). Furthermore, complex recognizable items were associated both with better memory precision and appeared supported by a richer range of neural representations than unrecognizable objects, suggesting that recognizable objects evoked richer and more variable contextual associations (Veldsman, Mitchell, & Cusack, 2017).…”

The role of meaning in visual working memory: Real-world objects, but not simple features, benefit from deeper processing.

“…Critically, by asking participants whether they perceived the stimuli as a face or not, that study also showed that enhancements in active maintenance of items in visual working memory are due to the subjective perception of the stimulus as meaningful, and are not driven by physical properties of the stimulus. Evidence from fMRI is also consistent with these results: for example, Veldsman et al (2017) found evidence of richer representations in critical working memory regions in parietal cortex for meaningful rather than perceptuallymatched non-meaningful stimuli; and Stojanoski et al (2019) found evidence that meaningful stimuli were processed in more high-level ventral regions in preparation for visual working memory storage than perceptually-matched non-meaningful stimuli.…”

“…For example, in other recent work, we have shown that a major reason not all studies have found object benefits at long encoding times (e.g., Quirk et al 2020;Li et al 2020) is that they chose foils unfairly, in a way that disadvantages objects relative to colors (Brady & Störmer, 2020). Once this is accounted for, significant benefits for memory performance with real-world objects emerge reliably compared to both colors (Brady & Störmer, 2020) and perceptually-matched meaningless stimuli (e.g., Brady & Störmer, 2020;Stojanoski et al 2019;Veldsman et al 2017;Sahar et al 2020). In addition, verbal re-encoding is always a potential concern with long encoding times, and studies have differed in how they have prevented this (e.g., Quirk et al 2020, Li et al 2020Brady et al 2016).…”

Loss of Adaptive Myelination Contributes to Methotrexate Chemotherapy-Related Cognitive Impairment

“…The neural substrate of attentional and short-term (<5-min) memory function is diffusely distributed (Cohen and Maunsell, 2011;Zhou and Desimone 2011;Zhang et al, 2011;Luo and Maunsell, 2015;Veldsman et al, 2017). While both attentional and short-term memory function involve the prefrontal cortex, including premotor cortex (Rizzolatti et al, 1987;Bichot et al, 2015;Chen et al, 2017;Barthas and Kwan 2017;Moore 2006), there is no clearly defined fiber bundle to specifically examine the axons relevant to these cognitive behavioral functions.…”