People can solve problems in more than one way. Two general strategies involve (A) methodical, conscious, search of problem-state transformations, and (B) sudden insight, with abrupt emergence of the solution into consciousness. This study elucidated the influence of initial resting brain-state on subjects' subsequent strategy choices. High-density electroencephalograms (EEGs) were recorded from subjects at rest who were subsequently directed to solve a series of anagrams. Subjects were divided into two groups based on the proportion of anagram solutions derived with self-reported insight versus search. Reaction-time and accuracy results were consistent with different cognitive problem-solving strategies used for solving anagrams with versus without insight. Spectral analyses yielded group differences in resting-state EEG supporting hypotheses concerning insight-related attentional diffusion and right-lateralized hemispheric asymmetry. These results reveal a relationship between resting-state brain activity and problem-solving strategy, and, more generally, a dependence of event-related neural computations on the preceding resting-state. KeywordsAttention; Creativity; Hemispheric Asymmetry; Insight; Problem Solving; Resting State Systematic, relatively stable, patterns of resting-state brain activity are associated with aspects of personality, intelligence, psychopathology, and neurological disorder (Davidson, 2003;John et al., 1988;Kumari et al., 2004;Thatcher et al., 2005), perhaps reflecting subtle differences in neuroanatomy or neurotransmitter levels (John et al., 1988). The existence of such associations suggests the possibility that resting-state neural activity may also be correlated with individual differences in the event-related, goal-oriented, cognitive processes that people use to negotiate the world around them, such as those used in problem solving.The present study examined the hypothesis that resting-state neural activity influences the cognitive strategies people use to solve problems, in particular, the general strategies which result in problem solutions derived either by methodical search or by sudden insight. Determining whether the tendency to solve problems by search versus insight is influenced by Send editorial correspondence to John Kounios,

Combining high-density scalp EEG recordings with a sensitive analog measure of short-term memory’s fidelity, we characterized the temporal dynamics of intentional ignoring, and related those dynamics to the intrusion of task-irrelevant information. On each trial of the task, two study Gabors were briefly presented in succession. A green or red disc preceding each Gabor signified whether that Gabor should be remembered or ignored, respectively. With cue-stimulus intervals of 300, 600, or 900 ms presented in separate sessions, we found that the onset of posterior, pre-stimulus alpha oscillations varied with the length of the interval. Although stimulus onset time was entirely predictable, the longer the cue-stimulus interval, the earlier the increase in pre-stimulus alpha power. However, the alpha-band modulation was not simply locked to the cue offset. The temporal envelopes of posterior alpha-band modulation were strikingly similar for both cued attending and cued ignoring, and differed only in magnitude. This similarity suggests that cued attending includes suppression of task irrelevant, spatial processing. Supporting the view that alpha-band oscillations represent inhibition, our graded measure of recall revealed that when the stimulus to be ignored appears second in the sequence, peri-stimulus alpha power predicted the degree to which that irrelevant stimulus distorted subsequent recall of the stimulus that was to be remembered. These results demonstrate that timely deployment of attention-related alpha-band oscillations can aid short-term memory by filtering out task-irrelevant information.

Accumulating evidence suggests that top-down processes, reflected by frontal-midline theta-band (4-8 Hz) electroencephalogram (EEG) oscillations, strengthen the activation of a memory set during short-term memory (STM) retention. In addition, the amplitude of posterior alpha-band (8-13 Hz) oscillations during STM retention is thought to reflect a mechanism that protects fragile STM activations from interference by gating bottom-up sensory inputs. The present study addressed two important questions about these phenomena. First, why have previous studies not consistently found memory set-size effects on frontal-midline theta? Second, how does posterior alpha participate in STM retention? To answer these questions, the present study examined large-scale network connectivity during STM retention by computing EEG wavelet coherence during the retention period of a modified Sternberg task using visually-presented letters as stimuli. The results showed (a) increasing theta-band coherence between frontal-midline and left temporal-parietal sites with increasing memory load, and (b) increasing alpha-band coherence between midline parietal and left temporal/parietal sites with increasing memory load. These findings support the view that theta-band coherence, rather than amplitude, is the key factor in selective top-down strengthening of the memory set and demonstrate that posterior alpha-band oscillations associated with sensory gating are involved in STM retention by participating in the STM network.

Cortical alpha oscillations (8–13 Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4–7 Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta’s association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention.

Semantic richness refers to the amount of semantic information associated with a concept. Reaction-time (RT) studies have shown that words referring to rich concepts elicit faster responses than those referring to impoverished ones, suggesting that richer concepts are activated more quickly. In a recent functional neuroimaging study, richer concepts evoked less neural activity, which was interpreted as faster activation. The interpretations of these findings appear to conflict with event-related potential (ERP) studies showing no evidence that speed of concept activation is influenced by typical semantic variables. Resolution of this apparent contradiction is important because the interpretation of 40 years of semantic-memory RT studies depends on whether factors such as semantic richness influence the duration of initial concept activation or later decision and response processes. Consistent with previous studies of the effects of semantic factors on ERP, the present study shows that richness influences the magnitude, but not the latency, of the P2 and N400 ERP components (which are early relative to behavioral responses), suggesting that effects of richness on RT reflect temporal effects on downstream decision or response mechanisms rather than on upstream concept activation.