Neural networks engaged in short-term memory rehearsal are disrupted by irrelevant speech in human subjects

Rehearsal mechanisms in human short-term memory are increasingly understood in the light of both behavioural and neuroanatomical findings. However, little is known about the cooperation of participating brain structures and how such cooperations are affected when memory performance is disrupted. In this paper we use EEG coherence as a measure of synchronization to investigate rehearsal processes and their disruption by irrelevant speech in a delayed serial recall paradigm. Fronto-central and fronto-parietal theta (4–7.5 Hz), beta (13–20 Hz), and gamma (35–47 Hz) synchronizations are shown to be involved in our short-term memory task. Moreover, the impairment in serial recall due to irrelevant speech was preceded by a reduction of gamma band coherence. Results suggest that the irrelevant speech effect has its neural basis in the disruption of left-lateralized fronto-central networks. This stresses the importance of gamma band activity for short-term memory operations

Spatiotemporal biases in manual interception: effects of visual and auditory information processing

This thesis assesses interrelations between spatial and temporal processing by investigating early psychophysical phenomena and implementing new empirical approaches on spatiotemporal processing in the context of movements. It consequently provides new perspectives to current theoretical debates on spatiotemporal processing. The processing of space and time is prone to distortions. For example, spatial length and temporal duration can impact the perception of each other (reciprocally). Longer lines are perceived to be presented for longer temporal intervals and (potentially) vice versa. Here it is argued that such spatiotemporal interrelations depend on the type of sensory input (e.g., visual or auditory), because the precision of spatial and temporal representations differs between sensory modalities. In summary, this thesis shows that i) spatiotemporal biases can transfer from perceptual judgements to motoric responses (i.e., interception and eye movements), that ii) the type of sensory input impacts these interrelations, and that iii) this effect of sensory modality might derive from differences in the acuity of the signal (and consequently representational noise). Thereby, the results indicate that seemingly contradictory theoretical predictions and related empirical findings might be explained by the involved sensory modalities, shed light on the potential impact of spatiotemporal biases on everyday tasks and add towards the debate on the perception-action dissociation, and more concretely on the discussions about visual illusions transferring to action

Filter effects and filter artifacts in the analysis of electrophysiological data

A commentary on Four conceptual fallacies in mapping the time course of recognition by VanRullen, R. (2011). Front. Psychol. 2:365. doi: 10.3389/fpsyg.2011.00365 Does filtering preclude us from studying ERP time-courses? by Rousselet, G. A. (2012). Front. Psychol. 3:131. doi: 10.3389/fpsyg.2012.0013

Segregating early physical and syntactic processes in auditory sentence comprehension

Auditory language comprehension involves physical as well as syntactic processing. The present study examined whether early physical and syntactic processes in spoken sentence comprehension can be segregated using event-related brain potentials (ERPs). In the physical manipulation condition, the terminal word of the sentence was presented either from the same or from a different location to the preceding sentence fragment. In the syntactic manipulation condition, the terminal word was either a syntactically correct continuation of the preceding sentence fragment or violated syntactic constraints. These two factors were completely crossed. Physical deviances elicited the mismatch negativity (MMN) and syntactic deviances the early syntax-related negativity, both deviance-related components of the ERP. Sentences which violated physical as well as syntactic constraints elicited a negativity which was larger than that elicited by only a physical or only a syntactic deviance. The elicitation of the MMN in connected speech demonstrates that this component can be used as a probe for auditory change-detection even in ecologically highly valid situations. The increase of deviance-related effects with double deviants suggests that the early physical and syntactic processing systems act, to a high degree, in parallel and independently of each other

Music matters: Preattentive musicality of the human brain

During listening to a musical piece, unexpected harmonies may evoke brain responses that are reflected electrically as an early right anterior negativity (ERAN) and a late frontal negativity (N5). In the present study we demonstrate that these components of the event-related potential can be evoked preattentively, that is, even when a musical stimulus is ignored. Both ERAN and N5 differed in amplitude as a function of music-theoretical principles. Participants had no special musical expertise; results thus provide evidence for an automatic processing of musical information in onmusicians.

Separate and concurrent symbolic predictions of sound features are processed differently: Separate and concurrent symbolic predictions of sound features areprocessed differently

The studies investigated the impact of predictive visual information about the pitch and location of a forthcoming sound on the sound processing. In Symbol-to-Sound matching paradigms, symbols induced predictions of particular sounds. The brain’s error signals (IR and N2b components of the event-related potential) were measured in response to occasional violations of the prediction, i.e. when a sound was incongruent to the corresponding symbol. IR and N2b index the detection of prediction violations at different levels, IR at a sensory and N2b at a cognitive level. Participants evaluated the congruency between prediction and actual sound by button press. When the prediction referred to only the pitch or only the location feature (Exp. 1), the violation of each feature elicited IR and N2b. The IRs to pitch and location violations revealed differences in the in time course and topography, suggesting that they were generated in feature-specific sensory areas. When the prediction referred to both features concurrently (Exp. 2), that is, the symbol predicted the sound´s pitch and location, either one or both predictions were violated. Unexpectedly, no significant effects in the IR range were obtained. However, N2b was elicited in response to all violations. N2b in response to concurrent violations of pitch and location had a shorter latency. We conclude that associative predictions can be established by arbitrary rule-based symbols and for different sound features, and that concurrent violations are processed in parallel. In complex situations as in Exp. 2, capacity limitations appear to affect processing in a hierarchical manner. While predictions were presumably not reliably established at sensory levels (absence of IR), they were established at more cognitive levels, where sounds are represented categorially (presence of N2b)

Within- and between-subject consistency of perceptual segmentation in periodic noise: A combined behavioral tapping and EEG study

The human auditory system is capable of learning unstructured acoustic patterns that occur repeatedly. While most previous studies on perceptual learning focused on seamless pattern repetitions, our study included several presentation formats, which are more typical for memory tasks (involving temporal delays or irrelevant information between pattern presentations), and probed active recognition of learned patterns more directly. We adapted an established implicit learning paradigm and presented three groups of listeners with the same acoustic patterns in different presentation formats, i.e., either back-to-back, separated by a silent interval or by a masker sound. Participants additionally completed an unexpected memory test after the learning phase. We found substantial learning in all groups, measured indirectly via the increased sensitivity in a perceptual task for patterns that occurred repeatedly (compared to patterns that occurred only once) and more directly via above-chance recognition performance in the memory test. Pattern learning and recognition were robust across presentation formats. Therefore, we propose that similar mechanisms might underlie memory formation for initially unfamiliar sounds in everyday listening situations. Moreover, memories for unstructured acoustic patterns that were acquired implicitly through perceptual learning enable subsequent active recognition

Separate and concurrent symbolic predictions of sound features are processed differently: Separate and concurrent symbolic predictions of sound features areprocessed differently

The studies investigated the impact of predictive visual information about the pitch and location of a forthcoming sound on the sound processing. In Symbol-to-Sound matching paradigms, symbols induced predictions of particular sounds. The brain’s error signals (IR and N2b components of the event-related potential) were measured in response to occasional violations of the prediction, i.e. when a sound was incongruent to the corresponding symbol. IR and N2b index the detection of prediction violations at different levels, IR at a sensory and N2b at a cognitive level. Participants evaluated the congruency between prediction and actual sound by button press. When the prediction referred to only the pitch or only the location feature (Exp. 1), the violation of each feature elicited IR and N2b. The IRs to pitch and location violations revealed differences in the in time course and topography, suggesting that they were generated in feature-specific sensory areas. When the prediction referred to both features concurrently (Exp. 2), that is, the symbol predicted the sound´s pitch and location, either one or both predictions were violated. Unexpectedly, no significant effects in the IR range were obtained. However, N2b was elicited in response to all violations. N2b in response to concurrent violations of pitch and location had a shorter latency. We conclude that associative predictions can be established by arbitrary rule-based symbols and for different sound features, and that concurrent violations are processed in parallel. In complex situations as in Exp. 2, capacity limitations appear to affect processing in a hierarchical manner. While predictions were presumably not reliably established at sensory levels (absence of IR), they were established at more cognitive levels, where sounds are represented categorially (presence of N2b)

Perceptual learning and recognition of random acoustic patterns

The human auditory system is capable of learning unstructured acoustic patterns that occur repeatedly. While most previous studies on perceptual learning focused on seamless pattern repetitions, our study included several presentation formats, which are more typical for memory tasks (involving temporal delays or irrelevant information between pattern presentations), and probed active recognition of learned patterns more directly. We adapted an established implicit learning paradigm and presented three groups of listeners with the same acoustic patterns in different presentation formats, i.e., either back-to-back, separated by a silent interval or by a masker sound. Participants additionally completed an unexpected memory test after the learning phase. We found substantial learning in all groups, measured indirectly via the increased sensitivity in a perceptual task for patterns that occurred repeatedly (compared to patterns that occurred only once) and more directly via above-chance recognition performance in the memory test. Pattern learning and recognition were robust across presentation formats. Therefore, we propose that similar mechanisms might underlie memory formation for initially unfamiliar sounds in everyday listening situations. Moreover, memories for unstructured acoustic patterns that were acquired implicitly through perceptual learning enable subsequent active recognition

Auditory Pattern Representations Under Conditions of Uncertainty—An ERP Study

The auditory system is able to recognize auditory objects and is thought to form predictive models of them even though the acoustic information arriving at our ears is often imperfect, intermixed, or distorted. We investigated implicit regularity extraction for acoustically intact versus disrupted six-tone sound patterns via event-related potentials (ERPs). In an exact-repetition condition, identical patterns were repeated; in two distorted-repetition conditions, one randomly chosen segment in each sound pattern was replaced either by white noise or by a wrong pitch. In a roving-standard paradigm, sound patterns were repeated 1–12 times (standards) in a row before a new pattern (deviant) occurred. The participants were not informed about the roving rule and had to detect rarely occurring loudness changes. Behavioral detectability of pattern changes was assessed in a subsequent behavioral task. Pattern changes (standard vs. deviant) elicited mismatch negativity (MMN) and P3a, and were behaviorally detected above the chance level in all conditions, suggesting that the auditory system extracts regularities despite distortions in the acoustic input. However, MMN and P3a amplitude were decreased by distortions. At the level of MMN, both types of distortions caused similar impairments, suggesting that auditory regularity extraction is largely determined by the stimulus statistics of matching information. At the level of P3a, wrong-pitch distortions caused larger decreases than white-noise distortions. Wrong-pitch distortions likely prevented the engagement of restoration mechanisms and the segregation of disrupted from true pattern segments, causing stronger informational interference with the relevant pattern informatio