Piia Astikainen

Cortical and subcortical visual event-related potentials to oddball stimuli in rabbits.

&NA; Event‐related potentials (ERPs) to changes in the visual environment were recorded in rabbits. In the oddball condition, infrequently presented (deviant) stimuli occurred in a series of frequently presented (standard) stimuli. In the deviant‐alone condition, standards were omitted. ERPs to oddball‐deviants differed from those to standards in all recording sites (cerebellar cortex, visual cortex, dentate gyrus). No corresponding differences were found between ERPs to deviants in the oddball condition and those in the deviant‐alone condition. However, because ERPs to deviants in the deviant‐alone condition and those to standards did not differ either, ERPs to stimulus changes in the oddball condition seemed to be dependent on the presence of standards, thus representing an analogue to mismatch negativity (MMN) in humans.

Automatic auditory intelligence: an expression of the sensory-cognitive core of cognitive processes.

In this article, we present a new view on the nature of cognitive processes suggesting that there is a common core, viz., automatic sensory-cognitive processes that form the basis for higher-order cognitive processes. It has been shown that automatic sensory-cognitive processes are shared by humans and various other species and occur at different developmental stages and even in different states of consciousness. This evidence, based on the automatic electrophysiological change-detection response mismatch negativity (MMN), its magnetoencephalographic equivalent MMNm, and behavioral data, indicates that in audition surprisingly complex processes occur automatically and mainly in the sensory-specific cortical regions. These processes include, e.g. stimulus anticipation and extrapolation, sequential stimulus-rule extraction, and pattern and pitch-interval encoding. Furthermore, these complex perceptual-cognitive processes, first found in waking adults, occur similarly even in sleeping newborns, anesthetized animals, and deeply sedated adult humans, suggesting that they form the common perceptual-cognitive core of cognitive processes in general. Although the present evidence originates mainly from the auditory modality, it is likely that analogous evidence could be obtained from other sensory modalities when measures corresponding to those used in the study of the auditory modality become available.

Visual mismatch negativity for changes in orientation : a sensory memory-dependent response

It remains unclear whether the mismatch negativity of event‐related potentials (ERPs) in vision resembles its auditory counterpart in terms of memory relatedness. We recorded ERPs to visual bars in adult humans engaged in an auditory task. In one condition, a bar (‘standard’) repeated at 400‐ or 1100‐ms non‐stimulated intervals was rarely (P = 0.1) replaced by another bar of a different orientation (‘deviant’). In the other condition (400‐ms intervals), the occurrences of the standards were replaced by 10 (P = 0.1 each) bars of different orientations, including that of the deviant (‘control‐deviant’). Deviants shifted ERPs towards negative polarity relative to standards in occipital electrodes and towards positive polarity in frontal electrodes at 185–205 ms post‐stimulus but only when 400‐ms non‐stimulated intervals were applied. Furthermore, the shift existed even relative to ERPs to control‐deviants. The findings suggest that, as in audition, vision supports the detection of voluntarily unattended changes per se within the constraints of sensory memory. The findings also pave the way for the future exploration of both intact and impaired memory‐based visual processing and memory capacity.

Visuospatial attention shifts by gaze and arrow cues: an ERP study.

Orienting of visual attention can be automatically triggered not only by illumination changes occurring in the visual periphery but also by centrally presented gaze and arrow cues. We investigated whether the automatic shifts of visuospatial attention triggered by centrally displayed gaze and arrow cues rely on the same neural systems. To this end we measured event-related potentials (ERPs) time-locked to the cue and target onsets while the participants (n=17) performed a spatial cuing task. In the task, the participants detected and responded to laterally presented targets preceded by centrally presented, non-predictive, gaze or arrow cues. Manual reaction times and target-triggered ERP data showed that both gaze and arrow cues automatically oriented attention and facilitated subsequent processing of target stimuli. However, the cue-triggered electrophysiological data indicated that the ERPs elicited by the gaze and arrow cues were different at lateral parietal and fronto-central electrode sites. Most notably, for the arrows, we found a typical early attention direction negativity (EDAN) effect occurring 220-260 ms after the cue onset. The ERPs were shifted in the negative direction when the arrows pointed to a direction which was contralateral to the recorded hemisphere as compared to arrows with ipsilateral direction. This effect was not observed for the gaze stimuli. These results provide further support for earlier behavioral and neuroimaging studies indicating that automatic orienting of attention by arrow cues and gaze cues are based on different neural mechanisms.

Tensor decomposition of EEG signals: a brief review.

Electroencephalography (EEG) is one fundamental tool for functional brain imaging. EEG signals tend to be represented by a vector or a matrix to facilitate data processing and analysis with generally understood methodologies like time-series analysis, spectral analysis and matrix decomposition. Indeed, EEG signals are often naturally born with more than two modes of time and space, and they can be denoted by a multi-way array called as tensor. This review summarizes the current progress of tensor decomposition of EEG signals with three aspects. The first is about the existing modes and tensors of EEG signals. Second, two fundamental tensor decomposition models, canonical polyadic decomposition (CPD, it is also called parallel factor analysis-PARAFAC) and Tucker decomposition, are introduced and compared. Moreover, the applications of the two models for EEG signals are addressed. Particularly, the determination of the number of components for each mode is discussed. Finally, the N-way partial least square and higher-order partial least square are described for a potential trend to process and analyze brain signals of two modalities simultaneously.

The human brain processes visual changes that are not cued by attended auditory stimulation.

Event-related potentials (ERPs) to visual stimuli were recorded from the scalp of eight adult humans performing a task in which they counted vowels from a heard story. In the oddball condition, a repeated (standard) light bar of 50 ms in duration was rarely (P = 0.1) replaced by a (deviant) one differing in orientation from the standard. In the control condition, standards were simply omitted from the series and only (alone-) deviants retained. In both conditions, visual stimuli were asynchronous with auditory-task-relevant stimuli. ERPs to deviants significantly differed in amplitude from those to standards in the midline electrodes centrally, parietally and occipitally at 160-200 ms from stimulus onset. Occipitally, such a difference was absent between ERPs to alone-deviants and those to standards. The occipital differential ERPs to deviants, which thus could be found only when standards were present in the series, are discussed in the context of the mismatch negativity (MMN).

Memory-based mismatch response to frequency changes in rats.

Any occasional changes in the acoustic environment are of potential importance for survival. In humans, the preattentive detection of such changes generates the mismatch negativity (MMN) component of event-related brain potentials. MMN is elicited to rare changes (‘deviants’) in a series of otherwise regularly repeating stimuli (‘standards’). Deviant stimuli are detected on the basis of a neural comparison process between the input from the current stimulus and the sensory memory trace of the standard stimuli. It is, however, unclear to what extent animals show a similar comparison process in response to auditory changes. To resolve this issue, epidural potentials were recorded above the primary auditory cortex of urethane-anesthetized rats. In an oddball condition, tone frequency was used to differentiate deviants interspersed randomly among a standard tone. Mismatch responses were observed at 60–100 ms after stimulus onset for frequency increases of 5% and 12.5% but not for similarly descending deviants. The response diminished when the silent inter-stimulus interval was increased from 375 ms to 600 ms for +5% deviants and from 600 ms to 1000 ms for +12.5% deviants. In comparison to the oddball condition the response also diminished in a control condition in which no repetitive standards were presented (equiprobable condition). These findings suggest that the rat mismatch response is similar to the human MMN and indicate that anesthetized rats provide a valuable model for studies of central auditory processing.

MULTI-DOMAIN FEATURE EXTRACTION FOR SMALL EVENT-RELATED POTENTIALS THROUGH NONNEGATIVE MULTI-WAY ARRAY DECOMPOSITION FROM LOW DENSE ARRAY EEG

Non-negative Canonical Polyadic decomposition (NCPD) and non-negative Tucker decomposition (NTD) were compared for extracting the multi-domain feature of visual mismatch negativity (vMMN), a small event-related potential (ERP), for the cognitive research. Since signal-to-noise ratio in vMMN is low, NTD outperformed NCPD. Moreover, we proposed an approach to select the multi-domain feature of an ERP among all extracted features and discussed determination of numbers of extracted components in NCPD and NTD regarding the ERP context.

N170 response to facial expressions is modulated by the affective congruency between the emotional expression and preceding affective picture.

Does contextual affective information influence the processing of facial expressions already at the relatively early stages of face processing? We measured event-related brain potentials to happy and sad facial expressions primed by preceding pictures with affectively positive and negative scenes. The face-sensitive N170 response amplitudes showed a clear affective priming effect: N170 amplitudes to happy faces were larger when presented after positive vs. negative primes, whereas the N170 amplitudes to sad faces were larger when presented after negative vs. positive primes. Priming effects were also observed on later brain responses. The results support an early integration in processing of contextual and facial affective information. The results also provide neurophysiological support for theories suggesting that behavioral affective priming effects are based, at least in part, on facilitation of encoding of incoming affective information.

Auditory Cortical and Hippocampal-System Mismatch Responses to Duration Deviants in Urethane-Anesthetized Rats

Any change in the invariant aspects of the auditory environment is of potential importance. The human brain preattentively or automatically detects such changes. The mismatch negativity (MMN) of event-related potentials (ERPs) reflects this initial stage of auditory change detection. The origin of MMN is held to be cortical. The hippocampus is associated with a later generated P3a of ERPs reflecting involuntarily attention switches towards auditory changes that are high in magnitude. The evidence for this cortico-hippocampal dichotomy is scarce, however. To shed further light on this issue, auditory cortical and hippocampal-system (CA1, dentate gyrus, subiculum) local-field potentials were recorded in urethane-anesthetized rats. A rare tone in duration (deviant) was interspersed with a repeated tone (standard). Two standard-to-standard (SSI) and standard-to-deviant (SDI) intervals (200 ms vs. 500 ms) were applied in different combinations to vary the observability of responses resembling MMN (mismatch responses). Mismatch responses were observed at 51.5–89 ms with the 500-ms SSI coupled with the 200-ms SDI but not with the three remaining combinations. Most importantly, the responses appeared in both the auditory-cortical and hippocampal locations. The findings suggest that the hippocampus may play a role in (cortical) manifestation of MMN.