31) Taking a look at memory retrieval: investigating the relationship of eye-movements and alpha/beta desynchronization
Tara Beilner1, Xiongbo Wu1, Tobias Staudigl1
1Ludwig-Maximilians-Universität in Munich, Germany
Humans mainly rely on vision to obtain knowledge about the world. Research has repeatedly identified links between eye-movements – such as saccades, fixations and their sequential patterns – and episodic memory. Successful memory formation has been associated with more visual exploration and alpha/beta (~8-30Hz) power decreases during initial viewing of a stimulus. Recent studies additionally observed a positive correlation between eye-movements and alpha/beta desynchronization in various tasks. Here, we investigate whether this link holds true during memory retrieval. In a free-viewing episodic memory task, participants were asked to visually explore naturalistic scenes. After a distractor task, they judged the novelty of both the previously seen (old) and new scenes. EEG and eye-tracking data were recorded simultaneously throughout the task. In line with the so-called repetition effect, less saccades were observed for old as opposed to new scenes. Participants also made less saccades during hits (correctly recognized old scenes) as compared to correct rejections (correctly recognized new scenes) and misses (not recognized old scenes). EEG time-frequency analyses revealed the typical alpha/beta desynchronization after stimulus onset. However, we did not observe robust differences in the previously mentioned contrasts. These findings indicate that the relationship between alpha/beta desynchronization and eye-movements found during encoding might not generalize to recognition memory tests. To further elucidate the relationship of eye-movements and electrophysiology during different memory processes, we are analyzing similarities of eye-movements patterns. Previous studies suggested that gaze pattern reinstatement facilitates remembering, but whether and how these similarities are reflected in alpha/beta activity is not known.
32) A Novel Thalamic Oscillation distinguishes Natural Brain States in Humans
Aditya Chowdhury1, Thomas Schreiner1, Elisabeth Kaufmann1, Jan Remi1, Tobias Staudigl1
1Ludwig-Maximilians-Universität in Munich, Germany
The thalamus plays a key role in regulating brain states by gating the flow of information between the sensory periphery and the cortex as well as between the different regions of the cortex. However, electrophysiological correlates of such regulating mechanisms remain severely underexplored, especially in humans. We here used the rare opportunity to record from the human thalamus in epilepsy patients implanted with Deep Brain Stimulation electrodes to probe the thalamus across different brain states - wakefulness, Rapid Eye Movement (REM) sleep, and Non Rapid Eye Movement (NREM) sleep. In line with previous literature, we find that the mesoscale thalamic field potential during NREM sleep is dominated by sleep spindles. However, during wakefulness and REM sleep, sleep spindles are replaced by a hitherto unreported oscillatory signal at ~25-50 Hz. This mesoscale oscillatory signal is robustly detected in the individual thalamic recordings of 14 participants. The thalamic oscillations during wake and REM sleep occur in bursts, much like sleep spindles. Indeed we find that the duration and shape of the bursts during REM sleep and wake correlate with those of sleep spindles during NREM sleep, indicative of a generation mechanism common to both oscillations. We further find that the strength of the oscillation correlates strongly with eye movement during phasic REM but anti-correlates with eye blinks during wakefulness. Overall, the presence of this hitherto unreported thalamic oscillation distinguishes natural states of consciousness and likely plays a role in regulating the flow of information during both wakefulness and phasic REM.
33) Motor planning is necessary and sufficient to bias subsequent motor performance
Christian Seegelke1, Tobias Heed1
1University of Salzburg, Austria
It is well established that our motor actions are influenced by recent, previous movements. These motor history effects are evident as biases in movement characteristics (e.g., reach direction, movement speed) and in response latencies. The prevailing but untested view holds that these effects emerge from prior planning-related activity. Here, we provide experimental evidence that planning but not executing a movement is critical for the emergence of history-dependent effects. For two successive movements, the second movement is initiated faster when the same hand is used (“hand repetition effect”). First, in an effector-choice reaching task, the hand repetition effect manifested only if the preceding movement was actively planned and executed, but not when it was passively performed by a robotic device (execution only); it manifested, albeit in reduced size, when the first movement was inhibited (planning only). Second, in an obstacle-avoidance reaching task, reach trajectories were strongly biased by obstacle location, both when the previous movement was planned and executed and when it was only planned. Bias declined with increasing response latencies and was absent when no motor plan was created, suggesting that it reflects a temporal decay of planning-related activity. These results support the view that motor planning is necessary and can even be sufficient to bias subsequent motor performance.
34) Miniature head movements reflect successful remembering
Merve Kutlu1, Thomas Schreiner1, Tobias Staudigl1
1Ludwig-Maximilians-Universität in Munich, Germany
Recent studies indicated a functional relationship between microscopic movements (e.g., microsaccades) and cognitive processes during attention and working memory tasks. It is, however, not known whether similar links exist between micromovements and long-term memory processes in humans. In this study, we asked whether micromovements reflect successful remembering in human episodic memory. Twenty-five healthy subjects participated in a scalp EEG study. They learned to associate 168 items (images of objects) with distinct head orientations by turning their head to face one of four screens where the image appeared. After a night of sleep, their memory for items was tested in a recognition test followed by an associative memory test where they were asked to recall the head orientation corresponding to the items. Importantly, participants looked straight ahead during the entire memory test. During recognition memory, alpha-beta desynchronization distinguished between retrieving familiar stimuli and processing new stimuli. Additionally, a significant difference in beta desynchronization for hits versus misses was found. During associative memory retrieval, microscopic head movements indicated successful remembering, as captured by motion-tracking signals and increased high-frequency EEG power. Event-related potentials also differed between items that were presented on left side screens and items presented on right side screens during learning. This difference correlated with the participants’ memory performance. Together, these findings suggest that experience-related muscle activities are recapitulated during remembering, indicating their putative reactivation from memory. Our study aims to contribute to the understanding of successful reactivation of spatial memories, particularly highlighting the role of microscopic movements for cognitive processes.
35) Mechanisms underlying sustained visual entrainment.
Aaron Kaltenmaier1,2, Quirin Gehmacher1,2, Peter Kok2, Matthew H. Davis3, Clare Press1,2
1University College London, University of London, United Kingdom, 2Wellcome Centre for Human Neuroimaging, University College London, University of London, United Kingdom, 3MRC Cognition and Brain Sciences Unit, University of Cambridge, United Kingdom
The functional role of neural oscillations across frequency bands is poorly understood, and interestingly, different claims have predominated across sensory domains. In the auditory domain, with speech as its prominent example, one exciting proposal is that low-frequency (delta, theta) oscillations ‘entrain’ to the dynamics of the input stream such that peaks of processing align with peaks of information. In vision, it is proposed instead that low-frequency oscillations are fixed across time, individuals, and species, but these conclusions are derived from studies with no information fluctuations across time. The present MEG study examines whether we could obtain visual low-frequency entrainment. We also ask whether such entrainment hinges on the sensory rhythm remaining relevant beyond its conclusion. To measure entrainment during and after visual stimulation, participants will fixate on 7 or 8 cycles of Gabors flashing at either 1.3 or 2Hz, before a 'silent' interval with the length of a further 3 cycles. We will test whether the frequency of stimulation determines oscillatory processing in the silent window and thereby whether visual low-frequency entrainment can be obtained. Each trial finishes with a target Gabor which, depending on the block, participants have to judge in terms of its orientation or timing. By comparing entrainment between these two tasks, we will test whether (sustained) entrainment requires the rhythm to be task-relevant. Our findings will determine importantly whether and how dynamic information flow determines the function of oscillations in the visual system, and provide a stepping stone to understanding oscillatory function across domains.
36) How do enhancement and suppression interactively shape selective attention?
Max Schulz1, Malte Wöstmann1, Jonas Obleser1
1University of Lübeck, Germany
Human environments comprise a plethora of auditory events, some of which are relevant targets while others are irrelevant distractors. In auditory attention research, our understanding of capture and suppression in distractor processing is premature. A suitable control condition to delineate target enhancement from distractor suppression has often been missing. We fill this gap by introducing a baseline and directly comparing neural and behavioral responses between neutral versus task-irrelevant and target sounds, inferring mechanisms of target enhancement, distractor suppression and capture. Additionally, negative priming, the impaired processing of a target that shares features with a previous distractor, serves as a sensitive index of active distractor suppression.
In a behavioral pilot study (N=7), listeners reported the pitch direction of an amplitude-modulated (AM) contour. Three different contour types (target, non-/salient distractor) were presented by assigning trial-wise unique temporal and spatial positions. Distraction was evidenced by lower accuracy in trials with the salient distractor present versus absent. Distractor suppression was indicated by lower accuracy when the current target appeared at the position of the previous distractor (i.e., negative priming).
Building on these findings, we are currently establishing a novel electroencephalography (EEG) paradigm: Participants report the identity of an AM target sound while ignoring simultaneously presented salient and non-salient distractors from three separate spatial locations. We will leverage neural signatures associated with attention capture (e.g., N1 amplitude) and distractor suppression (e.g., Pd amplitude, alpha oscillations) to investigate how neural enhancement and suppression interactively shape selective attention.
37) Mu-desynchronization during motor imagery of a motor sequence task - preliminary results
Annika Etzler1, Sophia Schnelzer1, Kerstin Hödlmoser1
1University of Salzburg, Austria
Aim: Investigating EEG mu-desynchronization (8-13 Hz) during motor imagery (MI) of a gross- motor-sequence-learning task as a potential marker of imagery ability and sleep-related performance gain.
Design: 31 younger (x̄=22.2, SD=2.54, 19 females) and 9 older adults (x̄=70.7, SD=3.91, 8 females) were tested over 7 days, including two nights of ambulatory polysomnography. Participants learned a sequential footstep task, either in the morning (AM-group) or in the evening (PM-group). Following the training participants of the MI-group practiced the sequence via MI, while the control-group listened to an audiobook. Physical performance was tested before (pre-test) and after MI/audiobook (post-test 1) and retested 12 (post-test 2) and 24 hours (post-test 3) later, followed by a second MI-session within the MI-group. EEG activity was recorded throughout all sessions. Mu-desynchronisation was computed as a decline in spectral mu-power during MI compared to mu-power during rest. MI-ability was assessed via questionnaires.
Results: Mu-desynchronisation during MI was strongest over parietal sites. Only subjects in the MI-group practicing in the evening increased their performance from post-test 1 to post-test 3 (t(25)=-6.79; p<.001). Mu-desynchronisation during the second MI correlated positively with sleep-related performance gain (r(13)=.45; p=.094). Both, immediate (r(13)=.55; p=.034) and delayed motor performance gain (r(13)=.58; p=.03) correlated with kinesthetic MI ability of the second MI session.
Conclusion: MI-training, accompanied by parietal mu-desynchronization, promotes performance gain, especially when followed by sleep compared to wakefulness. Results suggest that improvements in physical task execution benefits task imagery ability and can be reflected in changes of the EEG mu-rhythm during MI.
38) Tactile entrainment reveals a detailed categorization of digit representation and lateralization
Nicolò Castellani1, Alessandra Federici1, Marta Fantoni1, Emiliano Ricciardi1, Francesca Garbarini2, Davide Bottari1
1IMT School for Advanced Studies Lucca, Italy, 2University of Turin, Italy
Tactile interactions involve continuous processing of non-stationary inputs that change in location, duration, and intensity. Here, we aimed to demonstrate the possibility of objectively measuring how the somatosensory system synchronizes to continuous and unpredictable tactile stimulation. We computed a Temporal Response Function (TRF) at the individual level and investigated whether this measure of stimulus-brain synchronization could dissociate digit representation and digit lateralization, a pivotal feature of the somatosensory cortex.
Twenty-seven young adults (F=15) were passively stimulated with a random series of continuous and gentle brushes on single fingers of each hand, which were covered from view. An encoding model measured the degree of synchronization between brain activity and these continuous series of tactile inputs.
A clear TRF emerged for each fingers even when accounting for auditory and visual confounds. Results highlighted a central and contralateral positive response (50-170ms) a central bilateral negativity (200-300ms) (pclusts<0.05). Our results highlighted that TRF topographies clearly dissociated neural synchronization for stimulations to left and right-hand thumbs and pinkies between 50 and 380 ms (pclusts<0.05). Strikingly, topographies of the tactile TRF were also sensitive to finger stimulations within each hand between 50 and 250 ms (pclusts<0.05).
Our results demonstrated for the first time the possibility of using EEG to measure the neural synchronization or neural tracking of an ecological, unpredictable, and continuous stimulation in the somatosensory domain. Crucially, this method distinguishes digit lateralization and representation, linking the activity of the somatosensory system with individualized, idiosyncratic stimulations of a specific finger.
39) The mediating role of childhood motor skills on the association between error correction and social pragmatic communication in adulthood
Peter Bang1, Kajsa Igelström1, Johan Pieslinger1
1Linköping University Hospital, Sweden
Early motor function is important for emerging social pragmatic communication (SPC) skills in both typical and atypical development. However, the nature of motor impairments relevant for higher-level communication is not well understood. Inefficient cerebellar error correction might directly cause both developmental coordination disorder (DCD) symptoms and SPC difficulties, through the extensive communication between cerebellar zones and brain-wide sensorimotor and higher-order networks. DCD symptoms related to cerebellar deficits could also impact SPC through affecting the developmental trajectory of social development, which requires motor skills. This study aimed to test the hypothesis that error correction deficits affect SPC outcomes through childhood DCD symptoms, by using contemporary causal inference methodology. We used a finger tapping task and computational modeling to measure cerebellar error correction in adult participants (n = 138), and quantified childhood DCD symptoms and SPC skills using psychometric measures. The results confirmed that error correction ability likely affects SPC skills, and indicated that childhood motor skills significantly mediated this. These results argue against a direct effect of domain-general error correction deficits on SPC, and instead suggest that cerebellum-related DCD symptoms affect sociocommunicative development more directly through motor deficits during development. Further research is required to test whether cerebellar error correction could be used as an early marker to identify children in need for early SPC interventions.
40) Familiarization with previously unknown music leads to decreased theta and gamma ERD
Alireza Malekmohammadi1
1Technical University of Munich, Germany
Repeated listening to unknown music leads to gradual familiarization with musical sequences. Passively listening to musical sequences could involve an array of dynamic neural responses in reaching familiarization with the musical excerpts. This study elucidates the dynamic brain response and its variation over time by investigating the electrophysiological changes during familiarization with initially unknown music. Twenty subjects were asked to familiarize themselves with previously unknown 10 s classical music excerpts over three repetitions while their electroencephalogram was recorded. Time-frequency analyses reveal sustained theta event-related desynchronization (ERD) in the frontal-midline and the left prefrontal electrodes, which decreased gradually from the 1st to the 3rd time repetition of the same excerpts. Similarly, sustained gamma ERD decreased in the frontal-midline and bilaterally frontal/temporal areas. During familiarization, the decrease of theta ERD is superior in the first part (1–5 s), whereas the decrease of gamma ERD is superior in the second part (5–9 s) of music excerpts. The results suggest that decreased theta ERD is associated with successfully identifying familiar sequences, whereas decreased gamma ERD is related to forming unfamiliar sequences.