Does cross‐frequency phase coupling of oscillatory brain activity contribute to a better understanding of visual working memory?

Abstract

Nesting of fast rhythmical brain activity (gamma) into slower brain waves (theta) has frequently been suggested as a core mechanism of multi-item working memory (WM) retention. It provides a better understanding of WM capacity limitations, and, as we discuss in this review article, it can lead to applications for modulating memory capacity. However, could cross-frequency coupling of brain oscillations also constructively contribute to a better understanding of the neuronal signatures of working memory compatible with theoretical approaches that assume flexible capacity limits? Could a theta-gamma code also be considered as a neural mechanism of flexible sharing of cognitive resources between memory representations in multi-item WM? Here, we propose potential variants of theta-gamma coupling that could explain WM retention beyond a fixed memory capacity limit of a few visual items. Moreover, we suggest how to empirically test these predictions in the future.

Oscillatory Control over Representational States in Working Memory

“…In contrast, theta-gamma coupling during working memory is mostly observed in frontal regions ( [122,129]; though see [39]) and mainly during nonvisual or sequential working memory involving multiple representations [79,130]. This segmentation function seems similar to the function of delta-alpha coupling discussed here.…”

No evidence for spontaneous cross‐frequency phase–phase coupling in the human hippocampus

“…Our findings do not exclude instances of PPC in event‐related data recorded during cognitive paradigms (for overviews, see for instance, Palva & Palva, ; Sauseng et al, ). Moreover, it is possible that PPC is related to the occurrence of grapho‐elements during sleep (e.g.…”

“…Theta‐gamma PPC, for instance, may support the representation of items in working memory and the transfer of these representations to long‐term memory (e.g. Jensen & Lisman, ; Lisman & Idiart, ; Sauseng, Peylo, Biel, Friedrich, & Romberg‐Taylor, ). Compared to phase‐amplitude coupling, the higher temporal precision of PPC may be necessary for a non‐interfering representation of multiple items (Fell & Axmacher, ).…”

Flexible representations in visual working memory and interactions with long‐term learning: Commentary on the special issue

“…The past 20–30 years have seen a surge of interest in visual working memory (VWM), and it has become a lively field with many, often overlapping, topics of investigation (and debate) concerning: whether VWM is limited by the number of items that can be held (Adam, Vogel, & Awh, ; Cowan, ; Luck & Vogel, ) or by the distribution of a flexible resource (Bays, Catalao, & Husain, ; van den Berg, Shin, Chou, George, & Ma, ); whether representation in VWM is object‐based and how features are retained bound in VWM (see Schneegans & Bays, this issue, for a review); how structure and redundancy in to‐be‐remembered material influences performance (Brady & Alvarez, ; Liesefeld, Liesefeld, & Müller, this issue; Morey, this issue); to what extent storage of visual material occurs separately from storage of other material (Berggren & Eimer, this issue; Logie, ; Morey, ); what role VWM plays in real‐world looking behaviour and visual search (Annac, Zang, Müller, & Geyer, this issue; Berggren & Eimer, this issue; Pollmann, this issue); and questions about the neurobiology underlying VWM (for a review of oscillatory underpinnings, see Sauseng, Peylo, Biel, Friedrich, & Romberg‐Taylor, this issue) and what factors influence its capacity, such as the emotional valence of items (Curby, Smith, Moerel, & Dyson, this issue) or exercise (Dodwell, Müller, & Töllner, this issue).…”