The dorsal attention network is consistently involved in verbal and visual working memory (WM) tasks and has been associated with task-related, top–down control of attention. At the same time, WM capacity has been shown to depend on the amount of information that can be encoded in the focus of attention independently of top–down strategic control. We examined the role of the dorsal attention network in encoding load and top–down memory control during WM by manipulating encoding load and memory control requirements during a short-term probe recognition task for sequences of auditory (digits, letters) or visual (lines, unfamiliar faces) stimuli. Encoding load was manipulated by presenting sequences with small or large sets of memoranda while maintaining the amount of sensory stimuli constant. Top–down control was manipulated by instructing participants to passively maintain all stimuli or to selectively maintain stimuli from a predefined category. By using ROI and searchlight multivariate analysis strategies, we observed that the dorsal attention network encoded information for both load and control conditions in verbal and visuospatial modalities. Decoding of load conditions was in addition observed in modality-specific sensory cortices. These results highlight the complexity of the role of the dorsal attention network in WM by showing that this network supports both quantitative and qualitative aspects of attention during WM encoding, and this is in a partially modality-specific manner.

Over 350 years ago, Descartes proposed that the neural basis of consciousness must be a brain region in which sensory inputs are combined. Using fMRI, we identified at least one such area for working memory, the limited information held in mind, described by William James as the trailing edge of consciousness. Specifically, a region in the left intraparietal sulcus was found to demonstrate load-dependent activity for either visual stimuli (colored squares) or a combination of visual and auditory stimuli (spoken letters). This result was replicated across two experiments with different participants and methods. The results suggest that this brain region, previously well known for working memory of visually presented materials, actually holds or refers to information from more than one modality.

The mismatch negativity (MMN) component of event-related brain potentials is elicited by infrequent changes in regular acoustic sequences even if the participant is not actively listening to the sound sequence. Therefore, the MMN is assumed to result from a preattentive process in which an incoming sound is checked against the automatically detected regularities of the auditory sequence and is found to violate them. For example, presenting a discriminably different (deviant) sound within the sequence of a repetitive (standard) sound elicits the MMN. In the present article, we tested whether the memory organization of the auditory sequence can affect the preattentive change detection indexed by the MMN. In Experiment 1, trains of six standard tones were presented with a short, 0.5-sec stimulus onset asynchrony (SOA) between tones in the train. This was followed by a variable SOA between the last standard and the deviant tone (the “irregular presentation” condition). Of 12 participants displaying an MMN at the 0.5-sec predeviant SOA, it was elicited by 11 with the 2-sec predeviant SOA, in 5 participants with the 7-sec SOA, and in none with the 10-sec SOA. In Experiment 2, we repeated the 7-sec irregular predeviant SOA condition, along with a “regular presentation” condition in which the SOA between any two tones was 7 sec. MMN was elicited in about half of the participants (9 out of 16) in the irregular presentation condition, whereas in the regular presentation condition, MMN was elicited in all participants. These results cannot be explained on the basis of memory-strength decay but can be interpreted in terms of automatic, auditory preperceptual grouping principles. In the irregular presentation condition, the close grouping of standards may cause them to become irrelevant to the mismatch process when the deviant tone is presented after a long silent break. Because the MMN indexes preattentive auditory processing, the present results provide evidence that large-scale preperceptual organization of auditory events occurs despite attention being directed away from the auditory stimuli.

Research with the mismatch negativity component of event-related potentials has uncovered a system that detects change in the acoustic environment on an automatic basis. The system is considered to compare incoming stimuli to representations of the past and to emit an MMN if change is detected. Previous investigations have shown that the relevant memory of the past can become dormant and then be reactivated by a reminder stimulus. It is unclear, however, whether what is reactivated is an holistic representation of stimuli or separate representations of features of stimuli. The present study provides data that supports the latter possibility but leaves open the former one.

The mismatch negativity (MMN) event-related potential (ERP) component is elicited by any discriminable change in series of repetitive auditory stimuli. MMN is generated by a process registering the deviation of the incoming stimulus from the trace of the previous repetitive stimulus. Using MMN as a probe into auditory sensory memory, the present study addressed the question of whether the sensory memory representation is formed strictly on the basis of an automatic feature analysis of incoming sensory stimuli or information from long-term memory is also incorporated. Trains of 6 tone bursts (standards with up to 1 deviant per train) separated by 9.5-sec intertrain intervals were presented to subjects performing a visual tracking task and disregarding the auditory stimuli. Trains were grouped into stimulus blocks of 20 trains with a 2-min rest period between blocks. In the Constant-Standard Condition, both standard and deviant stimuli remained fixed across the session, encouraging the formation of a long-term memory representation. To eliminate the carryover of sensory storage from one train to the next, the first 3.6 sec of the intertrain interval was filled with 6 tones of random frequencies. In the Roving-Standard Condition, the standard changed from train to train and the intervening tones were omitted. It was found that MMN was elicited by deviants presented in Position 2 of the trains in the Constant-Standard Condition revealing that a single reminder of the constant standard reactivated the standard-stimulus representation. The MMN amplitude increased across trials within each stimulus block in the Constant- but not in the Roving-Standard Condition, demonstrating long-term learning in that condition (i.e., the standard-stimulus trace indexed by the MMN amplitude benefitted from the presentations of the constant standard in the previous trains). The present results suggest that the transient auditory sensory memory representation underlying the MMN is facilitated by a longer-term representation of the corresponding stimulus.