Microsaccades Track Location-Based Object Rehearsal in Visual Working Memory

Besides controlling eye movements, the brain's oculomotor system has been implicated in the control of covert spatial attention and the rehearsal of spatial information in working memory. We investigated whether the oculomotor system also contributes to rehearsing visual objects in working memory when object location is never asked about. To address this, we tracked the incidental use of locations for mnemonic rehearsal via directional biases in microsaccades while participants maintained two visual objects (colored oriented gratings) in working memory. By varying the stimulus configuration (horizontal, diagonal, and vertical) at encoding, we could quantify whether microsaccades were more aligned with the configurational axis of the memory contents, as opposed to the orthogonal axis. Experiment 1 revealed that microsaccades continued to be biased along the axis of the memory content several seconds into the working memory delay. In Experiment 2, we confirmed that this directional microsaccade bias was specific to memory demands, ruling out lingering effects from passive and attentive encoding of the same visual objects in the same configurations. Thus, by studying microsaccade directions, we uncover oculomotor-driven rehearsal of visual objects in working memory through their associated locations.

No obligatory trade-off between the use of space and time for working memory

Space and time can each act as scaffolds for the individuation and selection of visual objects in working memory. Here we ask whether there is a trade-off between the use of space and time for visual working memory: whether observers will rely less on space, when memoranda can additionally be individuated through time. We tracked the use of space through directional biases in microsaccades after attention was directed to memory contents that had been encoded simultaneously or sequentially to the left and right of fixation. We found that spatial gaze biases were preserved when participants could (Experiment 1) and even when they had to (Experiment 2) additionally rely on time for object individuation. Thus, space remains a profound organizing medium for working memory even when other organizing sources are available and utilized, with no evidence for an obligatory trade-off between the use of space and time.

Attentional Weighting in the Face Processing Network: A Magnetic Response Image-guided Magnetoencephalography Study Using Multiple Cyclic Entrainments

We recorded magnetoencephalography using a neural entrainment paradigm with compound face stimuli that allowed for entraining the processing of various parts of a face (eyes, mouth) as well as changes in facial identity. Our magnetic response image-guided magnetoencephalography analyses revealed that different subnodes of the human face processing network were entrained differentially according to their functional specialization. Whereas the occipital face area was most responsive to the rate at which face parts (e.g., the mouth) changed, and face patches in the STS were mostly entrained by rhythmic changes in the eye region, the fusiform face area was the only subregion that was strongly entrained by the rhythmic changes in facial identity. Furthermore, top-down attention to the mouth, eyes, or identity of the face selectively modulated the neural processing in the respective area (i.e., occipital face area, STS, or fusiform face area), resembling behavioral cue validity effects observed in the participants' RT and detection rate data. Our results show the attentional weighting of the visual processing of different aspects and dimensions of a single face object, at various stages of the involved visual processing hierarchy.

Cell surface labelling of mononuclear cells with antisera associated to turnip yellow mosaic virus of alphalpha mosaic virus particles. A freeze-etch study

Turnip yellow mosaic virus (TYMV) and alphalpha mosaic virus (AMV) were used as immuno-electron microscopical markers to detect cell surface receptors on mononuclear cells in freeze-etch replicas. TYMV particles were conjugated with vacuum-distilled glutaraldehyde to rabbit IgG anti-mouse immunoglobulins (TYMV-RAMIg conjugate) or to rabbit IgG anti-mouse theta antigen (TYMV-RAMTh conjugate). B-lymphocytes incubated with TYMV-RAMIg conjugate showed either randomly distributed particles or patches of virus particles on the etched surface of the cell membrane. Mouse thymocytes incubated with TYMV-RAMTh conjugate, however, showed only a random distribution of the virus particles. Human mononuclear cells incubated with rabbit IgG anti-AMV and AMV for the demonstration of the receptors for the Fc fragment of IgG showed the oblong shape of the AMV particles on the etched cell membrane, Fc receptors were either randomly distributed or aggregrated into patches. It is concluded that both types of virus particles are useful markers for the demonstration of membrane receptors in freeze-etch replicas of labelled cells.