Toward a neurobiology of internal selective attention

Memory and attention: A double dissociation between memory encoding and memory retrieval

Research has found substantial negative effects of divided attention (DA) during encoding but less substantial effects when attention is divided during retrieval, an asymmetry which has been interpreted as indicating that different control processes or forms of attention are involved in encoding and retrieval (e.g., Chun & Johnson, 2011; Craik, Govoni, Naveh-Benjamin, & Anderson, 1996; Long, Kuhl, & Chun, 2018). The extant evidence, however, is not strong support for qualitative differences and might simply indicate differential sensitivity. The present experiments document a stronger, double dissociation by focusing on the Attentional Boost Effect (ABE) - a phenomenon in which the detection of targets in a secondary task enhances encoding of co-occurring stimuli. The dual-task interaction account proposes that the classical negative effects produced by dual-task interference are offset by a transient increase in externally-directed attention brought about by target detection. Since externally-directed attention is less valuable for retrieval processes, the ABE should result in a net negative effect when applied in the test phase because the dual-task interference would no longer be offset by the externally-directed boost occurring during target trials. Experiments 1, 2 and 4 confirmed the predictions by showing that test words paired with target stimuli were recognized significantly worse than test words paired with distractor stimuli. In contrast, Experiments 3 and 4 replicated the usual positive effects of the ABE with respect to encoding. We discuss these findings in light of recent theoretical proposals suggesting that encoding and retrieval processes are subserved by different forms of attention (external [perceptual] vs. internal [reflective]). Implications for the Transfer-Appropriate-Processing view of memory are also illustrated.

A rapid theta network mechanism for flexible information encoding

Flexible behavior requires gating mechanisms that encode only task-relevant information in working memory. Extant literature supports a theoretical division of labor whereby lateral frontoparietal interactions underlie information maintenance and the striatum enacts the gate. Here, we reveal neocortical gating mechanisms in intracranial EEG patients by identifying rapid, within-trial changes in regional and inter-regional activities that predict subsequent behavioral outputs. Results first demonstrate information accumulation mechanisms that extend prior fMRI (i.e., regional high-frequency activity) and EEG evidence (inter-regional theta synchrony) of distributed neocortical networks in working memory. Second, results demonstrate that rapid changes in theta synchrony, reflected in changing patterns of default mode network connectivity, support filtering. Graph theoretical analyses further linked filtering in task-relevant information and filtering out irrelevant information to dorsal and ventral attention networks, respectively. Results establish a rapid neocortical theta network mechanism for flexible information encoding, a role previously attributed to the striatum.

Turning Attention Inside Out: How Working Memory Serves Behavior

Flexible behavior requires guidance not only by sensations that are available immediately but also by relevant mental contents carried forward through working memory. Therefore, selective-attention functions that modulate the contents of working memory to guide behavior (inside-out) are just as important as those operating on sensory signals to generate internal contents (outside-in). We review the burgeoning literature on selective attention in the inside-out direction and underscore its functional, flexible, and future-focused nature. We discuss in turn the purpose (why), targets (what), sources (when), and mechanisms (how) of selective attention inside working memory, using visual working memory as a model. We show how the study of internal selective attention brings new insights concerning the core cognitive processes of attention and working memory and how considering selective attention and working memory together paves the way for a rich and integrated understanding of how mind serves behavior.

Opening Questions in Visual Working Memory

In this reflective piece on visual working memory, I depart from the laboriously honed skills of writing a review. Instead of integrating approaches, synthesizing evidence, and building a cohesive perspective, I scratch my head and share niggles and puzzlements. I expose where my scholarship and understanding are stumped by findings and standard views in the literature.

Pattern reinstatement and attentional control overlap during episodic long-term memory retrieval

Episodic long-term memory (eLTM) retrieval involves the reinstatement of neural patterns from the encoding phase. However, recent evidence suggests that comparable cortical activity patterns can also be linked to attentional control processes on the level of memory representations. The current investigation assesses these two processes independently based on alpha-beta-band activity in the electroencephalogram (EEG). During encoding, subjects were presented with an object on a certain position on the screen and had to imagine it on a new position. In each trial, either the task-irrelevant presentation position or the task-relevant imagination position was lateralized. In the retrieval phase, subjects first made an old/new judgement based on centrally presented objects and then reported the imagination position. Pattern reinstatement should be reflected in similar lateralized alpha-beta activity during encoding and retrieval. Conversely, the influence of attentional control processes during retrieval would be associated with the suppression of alpha-beta power contralateral to the to-be-reported imagination position and with the increase of activity contralateral to the irrelevant presentation position. Our results support this latter pattern. This shows that an experimental differentiation between selective attention and pattern reinstatement processes is necessary when studying the neural basis of eLTM retrieval.

Functional but not obligatory link between microsaccades and neural modulation by covert spatial attention

Covert spatial attention is associated with spatial modulation of neural activity as well as with directional biases in fixational eye movements known as microsaccades. We studied how these two ‘fingerprints’ of attention are interrelated in humans. We investigated spatial modulation of 8-12 Hz EEG alpha activity and microsaccades when attention is directed internally within the spatial layout of visual working memory. Consistent with a common origin, spatial modulations of alpha activity and microsaccades co-vary: alpha lateralisation is stronger in trials with microsaccades toward versus away from the memorised location of the to-be-attended item and occurs earlier in trials with earlier microsaccades toward this item. Critically, however, trials without attention-driven microsaccades nevertheless show clear spatial modulation of alpha activity – comparable to trials with attention-driven microsaccades. Thus, directional biases in microsaccades correlate with neural signatures of spatial attention, but they are not necessary for neural modulation by spatial attention to be manifest.

Covert visual spatial attention modulates neural activity and biases the direction of small eye movements, known as microsaccades. Here, the authors show that these two markers co-vary, but that microsaccades are not necessary for neural modulation by attention to occur.

Emotional faces interfere with saccadic inhibition and attention re-orientation: An fMRI study

Modulation of reflex responses is crucial to adapt our behavior and cognition, and this is especially difficult when biological relevant stimuli are present such as emotional faces. The aim of this study was to identify the effect of peripherally presented happy and angry facial expressions in reflexive saccades and saccadic inhibition/re-orientation of attention. Behavior through eye-tracking technique and fMRI event-related BOLD signals activations were evaluated in adult males during the performance of an antisaccade task. fMRI signals obtained during task performance were compared to a baseline. Results showed that antisaccades had a lower percentage of correct responses and higher latency onsets than prosaccades. At the activation brain level, differences between both emotions and the baseline were found during stimuli presentation. Prosaccades for happy and angry faces recruited larger clusters with higher Z values mainly in occipito-parietal and temporal regions related to visual basic and integration processing, as well as regions of the oculomotor network. Meanwhile, when compared to the baseline, antisaccades recruited similar areas but a lower number of clusters with lower Z values as expected for peripheral processing of faces. At antisaccades, happy faces recruited parieto-occipital, temporal and cerebellar regions, while the angry faces added activation of orbital and ventrolateral prefrontal cortex related to emotional regulation. These results suggest that emotional facial expressions are being processed outside of the focus of attention. Particularly, angry expressions recruit a wider brain network in order to inhibit automatic behavior and re-orientate voluntary attention efficiently that may be due to its biological relevance.