Theta EEG neurofeedback promotes early consolidation of real life-like episodic memory.

Theta oscillations are believed to coordinate neuronal activity related to human cognition, especially for memory functions. Theta power during learning and retrieval has been found to correlate with memory performance success. Additionally, up-regulating theta oscillations during a post-encoding epoch crucial for memory consolidation was previously shown to benefit long-term memory for acquired motor sequences, pictures, and object-location associations. However, it remains to be determined whether such effects would be found for more ecological aspects of long-term episodic memory. Therefore, the current study assessed neurofeedback-based theta upregulation effects on movie memory. After viewing a 15-minute silent, narrative movie, participants engaged in neurofeedback-based theta/beta up-regulation, neurofeedback beta/theta up-regulation as an active control condition, or an unrelated passive control task. Memory was tested three times: once immediately after watching the movie (as baseline); 24 hours thereafter; and once again 1 week later. Memory performance 1 week after encoding was significantly enhanced in the theta/beta up-regulation group compared with the other groups. Additionally, changes in neurofeedback theta/beta ratio from baseline EEG recordings correlated with long-term memory gains in retrieving the movie's content. These findings highlight the relationship between post-learning theta oscillations and the consolidation of episodic memory for a naturalistic event.

The neural representations underlying asymmetric cross-modal prediction of words.

Cross-modal prediction serves a crucial adaptive role in the multisensory world, yet the neural mechanisms underlying this prediction are poorly understood. The present study addressed this important question by combining a novel audiovisual sequence memory task, functional magnetic resonance imaging (fMRI), and multivariate neural representational analyses. Our behavioral results revealed a reliable asymmetric cross-modal predictive effect, with a stronger prediction from visual to auditory (VA) modality than auditory to visual (AV) modality. Mirroring the behavioral pattern, we found the superior parietal lobe (SPL) showed higher pattern similarity for VA than AV pairs, and the strength of the predictive coding in the SPL was positively correlated with the behavioral predictive effect in the VA condition. Representational connectivity analyses further revealed that the SPL mediated the neural pathway from the visual to the auditory cortex in the VA condition but was not involved in the auditory to visual cortex pathway in the AV condition. Direct neural pathways within the unimodal regions were found for the visual-to-visual and auditory-to-auditory predictions. Together, these results provide novel insights into the neural mechanisms underlying cross-modal sequence prediction.

The Effects of Theta EEG Neurofeedback on the Consolidation of Spatial Memory.

How can the stability of a recently acquired memory be improved? Recent findings regarding the importance of theta frequency EEG activity in the hippocampus suggest that entraining neural activity in that frequency band might increase post-encoding waking replay, reinforcing learning-related plasticity. Our previous studies revealed that upregulating postlearning theta power using EEG neurofeedback (NFB) significantly benefitted procedural and episodic memory performance (both immediate and delayed), and may provide optimal conditions for stabilization of new memories. We have now explored whether memory benefits of theta NFB generalize to delayed spatial memory, an additional hippocampus-dependent process. Participants learned to associate object images with locations on a computer screen. NFB was used to enable participants to selectively increase scalp EEG theta power for 30 minutes. Visuo-spatial memory was tested one week later, with the theta NFB participants compared with 2 control groups (beta-augmentation NFB as an active control group, and an additional passive control group that did not engage in NFB). Theta upregulation was found to improve visuo-spatial memory, as reflected in reduced error distances in location marking and faster reaction time for correct answers by the theta group. This supports the contention that theta upregulation immediately after learning strengthens early consolidation of visuo-spatial memory. This intervention could potentially benefit various memory-challenged populations, as well as healthy individuals.

Enhancing early consolidation of human episodic memory by theta EEG neurofeedback.

Consolidation of newly formed memories is readily disrupted, but can it be enhanced? Given the prominent role of hippocampal theta oscillations in memory formation and retrieval, we hypothesized that upregulating theta power during early stages of consolidation might benefit memory stability and persistence. We used EEG neurofeedback to enable participants to selectively increase theta power in their EEG spectra following episodic memory encoding, while other participants engaged in low beta-focused neurofeedback or passively viewed a neutral nature movie. Free recall assessments immediately following the interventions, 24h later and 7d later all indicated benefit to memory of theta neurofeedback, relative to low beta neurofeedback or passive movie-viewing control conditions. The degree of benefit to memory was correlated with the extent of theta power modulation, but not with other spectral changes. Theta enhancement may provide optimal conditions for stabilization of new hippocampus-dependent memories.

Theta EEG neurofeedback benefits early consolidation of motor sequence learning.

Procedural learning is subject to consolidation processes believed to depend on the modulation of functional connections involved in representing the acquired skill. While sleep provides the most commonly studied framework for such consolidation processes, posttraining modulation of oscillatory brain activity may also impact on plasticity processes. Under the hypothesis that consolidation of motor learning is associated with theta band activity, we used EEG neurofeedback (NFB) to enable participants to selectively increase either theta or beta power in their EEG spectra following the acquisition phase of motor sequence learning. We tested performance on a motor task before and after training, right after the NFB session to assess immediate NFB effects, 1 day after NFB to assess interaction between NFB effects and overnight sleep-dependent stabilization, and 1 week after the initial session, to assess the effects of NFB on long-term stabilization of motor training. We also explored the extent of the influence of single-electrode NFB on EEG recorded across the scalp. Results revealed a significantly greater improvement in performance immediately after NFB in the theta group than in the beta group. This effect continued for testing up to 1 week following training. Across participants, post-NFB improvement correlated positively with theta/beta ratio change achieved during NFB. Additionally, NFB was found to cause widespread band-power modulation beyond the electrode used for feedback. Thus, upregulating postlearning theta power may yield contributions to the immediate performance and subsequent consolidation of an acquired motor skill.

Parietal lesion effects on cued recall following pair associate learning.

We investigated the involvement of the posterior parietal cortex in episodic memory in a lesion-effects study of cued recall following pair-associate learning. Groups of patients who had experienced first-incident stroke, generally in middle cerebral artery territory, and exhibited damage that included lateral posterior parietal regions, were tested within an early post-stroke time window. In three experiments, patients and matched healthy comparison groups executed repeated study and cued recall test blocks of pairs of words (Experiment 1), pairs of object pictures (Experiment 2), or pairs of object pictures and environmental sounds (Experiment 3). Patients' brain CT scans were subjected to quantitative analysis of lesion volumes. Behavioral and lesion data were used to compute correlations between area lesion extent and memory deficits, and to conduct voxel-based lesion-symptom mapping. These analyses implicated lateral ventral parietal cortex, especially the angular gyrus, in cued recall deficits, most pronouncedly in the cross-modal picture-sound pairs task, though significant parietal lesion effects were also found in the unimodal word pairs and picture pairs tasks. In contrast to an earlier study in which comparable parietal lesions did not cause deficits in item recognition, these results indicate that lateral posterior parietal areas make a substantive contribution to demanding forms of recollective retrieval as represented by cued recall, especially for complex associative representations.

Does this ring a bell? Music-cued retrieval of semantic knowledge and metamemory judgments.

Failed knowledge recall attempts are sometimes accompanied by a strong feeling of imminent success, giving rise to a "tip-of-the-tongue" (TOT) experience. Similar to successful retrieval (i.e., the Know state, K), a TOT commences with strong cue familiarity but involves only partial retrieval of related information. We sought to characterize the cognitive processes and temporal dynamics of these retrieval states and to extend the applicability of previous findings about TOT to the auditory modality. Participants heard 3-sec initial segments of popular songs and were asked to recall their names. EEG was recorded while participants indicated their retrieval state via button press. Stimulus-locked analyses revealed a significant early left fronto-central difference between TOT and K, at 300-550 msec postcue onset. Post hoc analysis revealed that, in this time window, TOT also differed from DK (Don't Know) responses, which themselves were similar to the K responses. This finding indicates that neural processes, which may reflect strategy selection, ease of semantic processing, familiarity-related processes, or conflict monitoring, are indicative of the fate of our knowledge judgments long before we actually execute them.

Neural sensitivity to human voices: ERP evidence of task and attentional influences.

In an earlier study, we found that human voices evoked a positive event-related potential (ERP) peaking at approximately 320 ms after stimulus onset, distinctive from those elicited by instrumental tones. Here we show that though similar in latency to the Novelty P3, this Voice-Sensitive Response (VSR) differs in antecedent conditions and scalp distribution. Furthermore, when participants were not attending to stimuli, the response to voices was undistinguished from other harmonic stimuli (strings, winds, and brass). During a task requiring attending to a feature other than timbre, voices were not distinguished from voicelike stimuli (strings), but were distinguished from other harmonic stimuli. We suggest that the component elicited by voices and similar sounds reflects the allocation of attention on the basis of stimulus significance (as opposed to novelty), and propose an explanation of the task and attentional factors that contribute to the effect.