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[This corrects the article DOI: 10.3389/fresc.2023.1339072.]., (© 2024 Frontiers Production Office.)

Pain is one of the most common health problems and has a severe impact on quality of life. Yet, a suitable and efficient treatment is still not available for all patient populations suffering from pain. Interestingly, recent research shows that low threshold mechanosensory C-tactile (CT) fibres have a modulatory influence on pain. CT-fibres are activated by slow gentle stroking of the hairy skin, providing a pleasant sensation. Consequently, slow gentle stroking is known as affective touch. Currently, a clear overview of the way affective touch modulates pain, at a neural level, is missing. This review aims to present such an overview. To explain the interaction between affective touch and pain, first the neural basis of the affective touch system and the neural processing of pain will be described. To clarify these systems, a schematic illustration will be provided in every section. Hereafter, a novel model of interactions between affective touch and pain systems will be introduced. Finally, since affective touch might be suitable as a new treatment for chronic pain, possible clinical implications will be discussed.

Sharing an experience, without communicating, affects people’s subjective perception of the experience, often by intensifying it. We investigated the neural mechanisms underlying shared attention by implementing an EEG study where participants attended to and rated the intensity of emotional faces, simultaneously or independently. Participants performed the task in three experimental conditions: 1) alone (unshared), 2) simultaneously next to each other in pairs, without receiving feedback of the other’s responses (shared no feedback), and 3) simultaneously while receiving the feedback (shared with feedback). We focused on two face-sensitive ERP components: the amplitude of the N170 was greater in the shared with feedback condition compared to the unshared condition, reflecting a top-down effect of shared attention on the structural encoding of faces; while the EPN was greater in both shared context conditions compared to the unshared condition, reflecting an enhanced attention allocation in the processing of emotional content of faces, modulated by the social context. Behaviourally, we found a modulation of the perceived intensity for the neutral faces only, with an amplification of perceived neutrality in the shared feedback condition. Taken together, these results suggest that shared attention amplifies the neural processing of faces, regardless of the valence of facial expressions.

Counter-empathy significantly affects people’s social lives. Previous evidence indicates that the degree of counter-empathy can be either strong or weak. Strong counter-empathy easily occurs when empathizers are prejudiced against the targets of empathy (e.g. prejudice against outgroup members) and activates brain regions that are opposite to those activated by empathy. Weak counter-empathy may have different neural processing paths from strong ones, but its underlying neural mechanisms remain unclear. In this work, we used an unfair distribution paradigm, which can reduce participants’ prejudice against persons empathized with, and functional magnetic resonance imaging to explore the neural mechanisms underlying counter-empathy. Here, empathy and counter-empathy shared a common neural mechanism, induced by unfair distribution, in the right middle temporal gyrus. Counter-empathy activated distinct brain regions that differed from those of empathic responses in different situations. The functions of these brain regions, which included the middle frontal, middle temporal and left medial superior gyri, were similar and mostly related to emotional regulation and cognitive processing. Here, we propose a process model of counter-empathy, involving two processing paths according to whether or not prejudice exists. This study has theoretical significance and broadens our understanding of the cognitive neural mechanisms underlying empathy and counter-empathy.

Propagated activation of neurons through their network is an important process in the brain. Another crucial part of neural processing concerns adaptation over time of characteristics of this network such as connection strengths or excitability thresholds. This adaptation can be slow, as in learning from a multiple experiences, or it can be fast, as in memory formation. These adaptive network characteristics can be considered informational criteria for activation of a neuron. This then is viewed as a form of emergent information formation. Activation of neurons is determined by such information via a process termed criterial causation. In the current paper, the relationship of criterial causation with the principle of temporal factorisation for the dynamics of the world in general is explored. Temporal factorisation describes how the world represents information about its past in its present state, which then in turn determines the world’s future. In the paper, it is shown how these processes are analysed in more detail and modeled by (adaptive) network models.

Increased use of epidural Spinal Cord Stimulation (eSCS) for the rehabilitation of spinal cord injury (SCI) has highlighted the need for a greater understanding of the properties of reflex circuits in the isolated spinal cord, particularly in response to repetitive stimulation. Here, we investigate the frequency-dependence of modulation of short- and long-latency EMG responses of lower limb muscles in patients with SCI at rest. Single stimuli could evoke short-latency responses as well as long-latency (likely polysynaptic) responses. The short-latency component was enhanced at low frequencies and declined at higher rates. In all muscles, the effects of eSCS were more complex if polysynaptic activity was elicited, making the motor output become an active process expressed either as suppression, tonic or rhythmical activity. The polysynaptic activity threshold is not constant and might vary with different stimulation frequencies, which speaks for its temporal dependency. Polysynaptic components can be observed as direct responses, neuromodulation of monosynaptic responses or driving the muscle activity by themselves, depending on the frequency level. We suggest that the presence of polysynaptic activity could be a potential predictor for appropriate stimulation conditions. This work studies the complex behaviour of spinal circuits deprived of voluntary motor control from the brain and in the absence of any other inputs. This is done by describing the monosynaptic responses, polysynaptic activity, and its interaction through its input–output interaction with sustain stimulation that, unlike single stimuli used to study the reflex pathway, can strongly influence the interneuron circuitry and reveal a broader spectrum of connectivity. Supplementary Information The online version contains supplementary material available at 10.1007/s00221-021-06153-1.

Dogs, similarly to infants, have been shown to be sensitive to human speech especially when it is directed to them. However, what essential acoustic, paralinguistic and lexical features of dog-directed speech are responsible for this preference in dogs is largely unknown. In the present study, generalized dog (DDS)-, infant (IDS)- and adult (ADS)-directed speech stimuli were created by using prerecorded sentences of multiple female speakers and these composite (averaged) stimuli were then manipulated to control for linguistic content as well as to equalize their mean fundamental frequency (F0) value. All three possible pairwise combinations of these acoustic stimuli were then presented to adult dogs in a two-way choice task where two identical target objects were used to indicate the sound sources. We found a significant preference towards the target object associated with DDS in the DDS versus ADS condition and suggest that, for dogs, mean F0 difference is not essential for DDS–ADS discrimination. However, we did not find evidence of selection bias when IDS was simultaneously presented either with DDS or ADS. Interestingly, our results also showed that dogs were more willing to approach the ‘more prosodic’ location (i.e. DDS or IDS versus ADS) when the prosodically more prominent sound stimulus was presented on their left side which suggests right-hemispheric specialization for neural processing of prosodic sounds in this domestic species. We also found that dogs made their choice faster when the ‘more prosodic’ stimulus was given first which suggests that they can perceive the difference not only between DDS and ADS, but also between IDS and ADS and between IDS and DDS. In conclusion, the composite DDS, IDS and ADS stimuli in the present study proved to be an effective technique in exploring the acoustic determinants of dog-directed speech preference in dogs.

Our visual environment is highly dynamic, comprising changes in different parameters at multiple timescales in parallel. These changes inform us about the identities and movements of external objects, and at the same time depend on our own behavior. For us to efficiently interact with the environment, we therefore rely on visual representations that are as accurate as possible while also separating between different sources of information in the temporal domain. In my thesis, I studied the processing of continuous temporal information in the primate visual system. To this end, I used behavioral and electrophysiological measurements from human subjects, as well as neural recordings in two different primate animal models. The thesis comprises five experimental studies. In these, I investigated how temporal information is extracted from visual input, and how its neural representation depends on and enables motor behavior. The order of studies broadly follows the visual processing hierarchy, from representations of low-level information at early (studies I & II) and intermediate visual areas (III), to the processing of high-level information in visuomotor control (IV & V). In the first two studies, I investigated the response of primary visual cortex (area V1) to continuous random luminance sequences. The response properties of neurons in area V1 have long been described by an approximately linear impulse response, that is stable in the temporal domain even during continuous stimulation. Yet, recent human EEG studies showed that, when stimulated with broadband luminance sequences, area V1 selects a distinct temporal frequency (alpha, at approx. 10 Hz) from the input and propagates its information across cortical space in the form of a traveling wave (the “perceptual echo”; VanRullen and MacDonald, 2012; Lozano-Soldevilla and VanRullen, 2019). This non-linear response has been suggested to play a functional role in the active sampling of visual information, based on evidence from the human EEG. However, it had not been investigated how it is generated on a neural level, and a description of intracortical responses to the same stimulation in the animal model has been lacking. In the first study, I combined EEG recordings in human observers with two established behavioral paradigms to study if and how the echo response is modulated by shifts in the cortical excitation/inhibition balance. I could show that the echo response is enhanced when the excitatory gain to area V1 is increased globally, but not when this modulation is limited to the input from one eye. This suggests that the echo is a cortically distributed response associated with excitatory neural states, dissociating it from spontaneous alpha oscillations which depend rather on inhibitory feedback loops (Hindriks and van Putten, 2013). In my second study, I investigated the neural responses in primary visual cortex to the same broadband luminance stimulation. Using the marmoset monkey as an animal model, I showed that - unexpectedly - the local representations in area V1 are already highly selective for distinct frequency bands, comprising an alpha-band component that possibly represents a functional homologue of the human echo response. A comparison between responses from the anesthetized and the awake preparation showed that the frequency-selectivity is a signature of active visual processing, suggesting top-down modulatory signals as the driving mechanism. Together, my findings from the first two studies show that primary visual cortex actively extracts temporal information from continuous input at distinct frequencies, at the expense of information in other bands. The second study provides first, tentative evidence in the search for a neural correlate of the perceptual echo response. One of the challenges the visual system is faced with in maintaining accurate temporal representations is that the incoming visual input changes drastically every time we move our eyes. Previous investigations have identified distinct neural mechanisms that modulate responses around the time of saccadic eye-movements to counterbalance this instability. These modulations also affect the temporal domain of visual processing, as demonstrated by changes in neural response latencies (Reppas et al., 2002; Ibbotson et al., 2006) and illusory distortions of perceived time (Yarrow et al., 2001; Morrone et al., 2005; Knöll et al., 2013). Yet, substantial differences between areas as well as diverging perceptual effects have been difficult to reconcile thus far. To broaden our understanding of the neural signature of perisaccadic modulations of temporal encoding, in the third study I compared temporal information processing between fixation and perisaccadic time-windows in the ventral stream area V4 of macaque monkeys. By analyzing multi-unit responses to random sequential luminance stimulation I found that representations remained stable in temporal and spatial domains across saccades. However, the ratio of response amplitudes within a sequence was modulated by a global perisaccadic activity increase, in a way that could account for known perceptual effects. This finding newly introduces amplitude modulations as a neural correlate of perisaccadic distortions in the perception of time. The observation of stable representations in space and time contrasts with previously described perisaccadic spatial modulations in area V4 (Tolias et al., 2001). In light of evidence from other studies, we proposed that this disparity may partly reflect differences in processing between sequential and isolated visual stimulation. Taken together, the third study provided new insights on how temporal information processing is modulated by eye-movements, adding first findings for area V4 to existing evidence from other areas. The first three studies all considered temporal information contained in low-level visual features, such as luminance or contrast. Yet, in our natural visual input, changes in these features over time are often also linked to movements of objects or the environment relative to the observer. Using retinal velocity patterns (optic flow) as a cue, our visual system infers information about the body’s own movement in space from this input. Accordingly, early behavioral studies have demonstrated that humans, in stable stance, respond to visually simulated self-motion with compensatory postural adjustments (Lee, 1980). The final two studies in this thesis investigated how these responses are coupled to the temporal structure of self-motion information in the continuous visuomotor control of balance. The fourth study used measurements from a force-platform to characterize postural responses of human subjects to a visual environment that oscillated along the anterior-posterior axis, simulated in virtual reality. By applying an analysis procedure that was originally established in human EEG studies, we were able to show that postural responses coupled to the visual stimulus with high consistency. This coupling remained stable even for high temporal frequency (1.2 Hz) of the motion stimulus, suggesting that previous studies showing a selectivity for lower frequencies were biased by biomechanical constraints of the body through their analysis of response amplitude instead of phase. The fifth study extended this paradigm further by additional measurements from video-based full body tracking, in order to determine how the different body joints contribute to the observed postural responses. The findings revealed that the body’s balance control strategy depends greatly on the temporal frequency of the visual input. For higher frequencies, coupling was increasingly centered around the hip joint, matching model predictions by previous studies. Lastly, following up on the results from these two studies, we established a novel stimulation paradigm designed to provide a generalized mapping of visually evoked postural responses in the temporal domain. Applying the same approach as in the first two studies of this thesis, we used responses to broadband random self-motion sequences to investigate how the coupling behavior depended on temporal frequencies. The results revealed highly idiosyncratic response profiles for different subjects, possibly reflecting interindividual differences in visuomotor abilities as well as anthropometric factors. The frequency distributions of coupling surprisingly extended also towards very high frequencies (> 2 Hz). These components likely reflect a third, reflexive strategy that may be controlled by different motor pathways. Taken together, these findings show that the visuomotor system uses the temporal structure of self-motion information for the control of balance during standing, selecting different frequency bands for distinct motor outputs. In conclusion, with this thesis I have investigated how the visual system extracts and processes temporal information from continuous input. My findings from different subsystems of the visual hierarchy show that neural representations of temporal information are functionally specialized through their selectivity for distinct frequency bands. In the primate animal model, I identified possible neural correlates of this frequency selection and characterized their dynamics during active visual behavior. Future research could make use of these as measures by which to distinguish functionally between different sensory systems, as well as between individuals, e.g., for clinical applications., Unsere visuelle Umgebung ist dynamisch und umfasst, parallel, Änderungen verschiedener Parameter auf mehreren zeitlichen Skalen. Diese Änderungen geben uns Aufschluss über die Identität von Objekten sowie deren Bewegungen im Raum, werden gleichzeitig aber auch von unserem eigenen Verhalten bestimmt. Um uns eine effiziente Interaktion mit der Umgebung zu ermöglichen, benötigen wir daher visuelle Repräsentationen, die so präzise wie möglich sind, und dabei auch die Trennung verschiedener Informationsquellen in der zeitlichen Dimension ermöglichen. In meiner Arbeit habe ich die Verarbeitung von kontinuierlicher zeitlicher Information im visuellen System von Primaten untersucht. Dafür habe ich Verhaltens- und elektrophysiologische Messungen an humanen Versuchspersonen, sowie neuronale Messungen in zwei verschiedenen Primaten-Tiermodellen durchgeführt. Die Arbeit umfasst fünf experimentelle Studien. In diesen habe ich im Einzelnen untersucht, wie zeitliche Information aus visuellem Input extrahiert wird und wie dessen neuronale Repräsentation von motorischem Verhalten abhängt und dieses steuert. Die Reihenfolge der Studien folgt vereinfacht der Hierarchie der visuellen Verarbeitung im Gehirn, von Repräsentationen simpler Information in frühen (Studien I & II) und mittleren kortikalen Arealen des visuellen Systems (III), hin zur Verarbeitung komplexerer Information im visuomotorischen System (IV & V). In den ersten beiden Studien untersuchte ich die neuronalen Antworten des primären visuellen Kortex (Areal V1) auf kontinuierliche, zufällige Luminanz-Sequenzen. Die Antworteigenschaften von V1-Neuronen wurden lange durch eine näherungsweise lineare Impulsantwort beschrieben, die auch für kontinuierliche Stimulation über die Zeit stabil ist. Aktuelle humane EEG Studien haben jedoch gezeigt, dass V1 als Antwort auf Stimulation mit Sequenzen im Breitband-Frequenzbereich eine bestimmte zeitliche Frequenz (Alpha, ca. 10 Hz) selektiert und diese Information in Form von fortschreitenden Wellen über den Kortex propagiert (das “perzeptuelle Echo”; VanRullen and MacDonald, 2012; Lozano-Soldevilla and VanRullen, 2019). Ausgehend von Evidenz aus humanen EEG-Studien wird vermutet, dass diese nichtlineare Antwort eine Funktion im sampling (dem zeitlichen Abtasten) visueller Information einnimmt. Ihre Entstehung auf neuronaler Ebene, ebenso wie die intrakortikalen Antworten auf die gleiche Stimulation im Tiermodell, sind jedoch noch nicht beschrieben worden. In der ersten Studie kombinierte ich EEG-Messungen an humanen Versuchspersonen mit zwei etablierten behavioralen Paradigmen, um zu untersuchen, wie die Echo-Antwort durch Veränderungen der kortikalen Balance zwischen Exzitation und Inhibition moduliert wird. Ich konnte zeigen, dass die Antwort nach einer globalen Verstärkung der exzitatorischen Inputs erhöht ist. Dieser Effekt trat jedoch nicht auf, wenn die Modulation auf den Input eines Auges begrenzt war. Dies deutete darauf hin, dass das Echo eine globale Antwort darstellt, die an exzitatorische neuronale Aktivität gekoppelt ist. Dies unterscheidet es von spontanen Alpha-Oszillationen, die von inhibitorischen Mechanismen abhängen (Hindriks and van Putten, 2013). In meiner zweiten Studie untersuchte ich die neuronalen Antworten auf die gleiche Stimulation im primären visuellen Kortex im Primatenmodell (Weißbüschelaffe). Experimentell konnte ich zeigen, dass die lokalen Antworten in V1 bereits stark selektiv für einzelne Frequenzbänder sind und dabei auch eine Komponente im Alpha-Band beinhalten, die ein funktionales Homolog der humanen Echo Antwort darstellen könnte. Ein Vergleich der Antworten zwischen anästhesierten und wachen Tieren zeigte, dass die Frequenzselektivität ein Merkmal der aktiven visuellen Verarbeitung ist, was auf Modulation aus höheren Arealen (top-down) hinweist. Zusammengenommen zeigten die Ergebnisse der ersten beiden Studien, dass der primäre visuelle Kortex aktiv zeitliche Information in bestimmten Frequenzbändern aus kontinuierlichem Input herausfiltert und dabei die Information anderer Frequenzen abschwächt. Die zweite Studie lieferte zudem erste Hinweise auf ein neuronales Korrelat der perzeptuellen Echos. Die präzise Repräsentation zeitlicher Information im visuellen System wird u.a. dadurch erschwert, dass sich der visuelle Input bei jeder Augenbewegung drastisch verändert. Vergangene Studien haben verschiedene Mechanismen identifiziert, die diese Instabilität durch Modulation neuronaler Antworten im Zeitfenster um sakkadische Augenbewegung herum kompensieren. Diese Modulationen betreffen auch die zeitliche Dimension der visuellen Verarbeitung, wie aus Veränderungen neuronaler Antwortlatenzen (Reppas et al., 2002; Ibbotson et al., 2006) und illusorischen Verzerrungen der Zeitwahrnehmung (Yarrow et al., 2001; Morrone et al., 2005; Knöll et al., 2013) hervorgeht. Unterschiede der Verarbeitung zwischen Hirnarealen sowie gegenläufige Wahrnehmungseffekte haben eine kohärente Interpretation bislang jedoch erschwert. Mit dem Ziel, unser Verständnis perisakkadischer zeitlicher Modulationen über das visuelle System hinweg auszuweiten, untersuchte ich in der dritten Studie im Areal V4 des ventralen Pfads des Makaken, ob und ggf. wie sich die Verarbeitung zeitlicher Information zwischen Fixation und perisakkadischen Zeitfenstern verändert. Meine Analyse von neuronalen Antworten auf sequenzielle Luminanzkontrast-Stimulation ergab, dass die Repräsentationen in Bezug auf zeitliche und räumliche Antworteigenschaften stabil blieben. Dabei wurde jedoch das Verhältnis der Antwort-Amplituden innerhalb einer Sequenz durch eine unselektive Erhöhung der Aktivität in perisakkadischen Zeitfenstern moduliert. Dies könnte auf Amplitudenmodulation als ein neuronales Korrelat sakkadischer Wahrnehmungsverzerrungen hindeuten. Der Befund stabiler raum-zeitlicher Repräsentationen steht im Kontrast zu zuvor beschriebenen perisakkadischen Modulationen räumlicher Antworteigenschaften in V4 (Tolias et al., 2001). Im Kontext der Ergebnisse anderer Studien kann vermutet werden, dass dies durch Unterschiede in der Verarbeitung zwischen sequenzieller und isolierter visueller Stimulation zu erklären ist. Zusammengenommen konnte die dritte Studie neue Hinweise darauf bieten, wie zeitliche Informationsverarbeitung von Augenbewegungen moduliert wird, und die vorhandene Literatur um erste Ergebnisse aus dem Areal V4 erweitern. Die ersten drei Studien beschäftigten sich mit zeitlicher Information, die in basalen visuellen Parametern enthalten ist, wie z.B. Luminanz oder Kontrast. In unserem natürlichen Umfeld sind zeitliche Änderungen dieser Parameter jedoch häufig an Bewegungen einzelner Objekte oder der gesamten Umgebung relativ zum Betrachter gekoppelt. Optische Flussfelder auf der Retina ermöglichen es dem visuellen System, aus diesem Input Informationen über die Bewegung des eigenen Körpers zu gewinnen. Bereits frühe Studien haben gezeigt, dass Menschen im Stand auf visuell simulierte Eigenbewegung mit posturalen Korrekturbewegungen reagieren (Lee, 1980). Die abschließenden zwei Studien dieser Arbeit untersuchten, wie diese Reaktionen in der visuomotorischen Kontrolle der Balance an die zeitliche Struktur der wahrgenommenen Eigenbewegung gekoppelt sind. Die vierte Studie verwendete Messungen mit einer Kraftmessplatte und Virtual Reality, um die posturalen Antworten von Versuchspersonen auf visuell simulierte, sinusförmige Eigenbewegung in anterior-posteriorer Richtung zu beschreiben. Durch die Anwendung etablierter Analysemethoden aus humanen EEG-Studien konnten wir zeigen, dass die Antworten mit hoher Konsistenz an den Stimulus koppelten und dass diese Kopplung auch für hohe zeitliche Stimulus-Frequenzen (1.2 Hz) stabil blieb. Dies deutet darauf hin, dass Befunde vergangener Studien, die eine Selektivität für niedrige Frequenzen gezeigt hatten, durch die Analyse der Antwort-Amplitude statt deren Phase durch biomechanische Eigenschaften verzerrt waren. Die fünfte Studie erweiterte dieses Paradigma zusätzlich um ein video-basiertes Ganz-Körper-Tracking mit dem Ziel, die Anteile einzelner Körperpartien an der gesamten Antwort zu bestimmen. Die Ergebnisse zeigten, dass die Balance-Strategie des Körpers stark von der zeitlichen Frequenz des visuellen Inputs abhängt. Für höhere Frequenzen verlagerte sich die Kopplung zunehmend auf das Hüftgelenk. Dieser Befund bestätigt die Modellvorhersagen früherer Studien. Aufbauend auf den Ergebnissen dieser zwei Studien etablierten wir zusätzlich ein neues Paradigma, das eine generalisierte Beschreibung der zeitlichen Eigenschaften visuell-evozierter posturaler Antworten ermöglichen sollte. Basierend auf dem gleichen Prinzip wie in den ersten zwei Studien dieser Arbeit verwendeten wir zufällige Eigenbewegungs-Sequenzen im Breitband-Frequenzbereich, um die Abhängigkeit des Kopplungsverhaltens von der zeitlichen Frequenz zu untersuchen. Die Ergebnisse zeigten stark idiosynkratische Muster in den posturalen Antworten der einzelnen Versuchspersonen. Diese könnten sowohl auf interindividuelle Unterschiede in den visuomotorischen Fähigkeiten als auch anthropometrische Faktoren zurückzuführen sein. Die Frequenzverteilungen der Kopplung zeigten überraschend starke Anteile in sehr hohen Frequenzen (> 2 Hz), die vermutlich eine dritte, reflexive Strategie unter Kontrolle anderer motorischer Pfade repräsentieren. Diese Ergebnisse zeigen, dass das visuomotorische System die zeitliche Struktur von Eigenbewegung für die Kontrolle der Balance im Stand verwendet, und dabei bestimmte Frequenzbänder für unterschiedliche motorische Muster selektiert. Zusammenfassend habe ich in meiner Arbeit untersucht, wie das visuelle System zeitliche Information aus kontinuierlichem Input extrahiert und verarbeitet. Meine Befunde aus unterschiedlichen Sub-Systemen der visuellen Hierarchie zeigen, dass die neuronale Repräsentation zeitlicher Information durch ihre Selektivität für bestimmte Frequenzbänder funktionell spezialisiert sind. Im Primaten-Tiermodell konnte ich mögliche neuronale Korrelate dieser Frequenzselektivität identifizieren und ihre Dynamik während aktiven visuellen Verhaltens beschreiben. Diese könnten in zukünftigen Studien verwendet werden um unterschiedliche sensorische Systeme funktional voneinander zu trennen, sowie als Marker für die neuronale Verarbeitung einzelner Individuen in klinischen Anwendungen.

Rules and regularities of language are typically processed in an implicit and effortless way in the human brain. Individuals with developmental dyslexia have problems in implicit learning of regularities in sequential stimuli, but the neural basis of this deficit has not been studied. This study investigated extraction and utilization of a complex auditory rule at neural and perceptual levels in 18 adults with dyslexia and 20 typical readers. Mismatch negativity (MMN) and P3a responses to rule violations in speech stimuli, reflecting change detection and attention switch, respectively, were recorded with electroencephalogram. Both groups reported no or little explicit awareness of the rule, suggesting implicit processing. People with dyslexia showed deficient extraction of the rule evidenced by diminished MMNs estimated to originate particularly from the left perisylvian region. The group difference persisted in the attentive condition after the participants were told about the rule, and behavioral detection of the rule violations was poor in people with dyslexia, possibly suggesting difficulties also in utilizing explicit information of the rule. Based on these results, the speech processing difficulties in dyslexia extend beyond phoneme discrimination and basic auditory feature extraction. Challenges in implicit extraction and effortless adoption of complex auditory rules may be central to language learning difficulties in dyslexia.

The interlocking roles of lexical, syntactic and semantic processing in language comprehension has been the subject of longstanding debate. Recently, the cortical response to a frequency-tagged linguistic stimulus has been shown to track the rate of phrase and sentence, as well as syllable, presentation. This could be interpreted as evidence for the hierarchical processing of speech, or as a response to the repetition of grammatical category. To examine the extent to which hierarchical structure plays a role in language processing we recorded EEG from human participants as they listen to isochronous streams of monosyllabic words. Comparing responses to sequences in which grammatical category is strictly alternating and chosen such that two-word phrases can be grammatically constructed — cold food loud room — or is absent — rough give ill tell — showed cortical entrainment at the two-word phrase rate was only present in the grammatical condition. Thus, grammatical category repetition alone does not yield entertainment at higher level than a word. On the other hand, cortical entrainment was reduced for the mixed-phrase condition that contained two-word phrases but no grammatical category repetition — that word send less — which is not what would be expected if the measured entrainment reflected purely abstract hierarchical syntactic units. Our results support a model in which word-level grammatical category information is required to build larger units.

The iterated prisoner's dilemma (iPD) game is a well-established model for testing how people cooperate, and the neural processes that unfold after its distinct outcomes have been partly described. Recent theoretical models suggest evolution favors intuitive cooperation, which raises questions on the behavioral but also neural timelines involved. We studied the outcome/feedback stage of iPD rounds with electroencephalography (EEG) methods. Results showed that neural signals associated with this stage also relate to future choice, in an outcome-dependent manner: (i) after zero-gain "sucker's payoffs" (unreciprocated cooperation), a participant's decision thereafter relates to changes to the feedback-related negativity (FRN); (ii) after one-sided non-cooperation (participant wins at co-player's expense), by the P3; (iii) after mutual cooperation, by late frontal delta-band modulations. Critically, faster reciprocation behavior towards a co-player's choice to cooperate was predicted, on a single-trial basis, by players' P3 and frontal delta modulations at the immediately preceding trial. Delta-band signaling is discussed in relation to homeostatic regulation processing in the literature. The findings relate the early outcome/feedback stage to subsequent decisional processes in the iPD, providing a first neural account of the brief timelines implied in heuristic modes of cooperation.

Funder: College of Biological Sciences, University of Minnesota, Drosophila melanogaster has long been a popular model insect species, due in large part to the availability of genetic tools and is fast becoming the model for insect colour vision. Key to understanding colour reception in Drosophila is in-depth knowledge of spectral inputs and downstream neural processing. While recent studies have sparked renewed interest in colour processing in Drosophila, photoreceptor spectral sensitivity measurements have yet to be carried out in vivo. We have fully characterised the spectral input to the motion and colour vision pathways, and directly measured the effects of spectral modulating factors, screening pigment density and carotenoid-based ocular pigments. All receptor sensitivities had significant shifts in spectral sensitivity compared to previous measurements. Notably, the spectral range of the Rh6 visual pigment is substantially broadened and its peak sensitivity is shifted by 92 nm from 508 to 600 nm. We show that this deviation can be explained by transmission of long wavelengths through the red screening pigment and by the presence of the blue-absorbing filter in the R7y receptors. Further, we tested direct interactions between inner and outer photoreceptors using selective recovery of activity in photoreceptor pairs.

The common display of atypical behavioral responses to sounds by individuals with autism (ASD) suggests that they process sounds differently. Within ASD, individuals who are minimally or low verbal (ASD-MLV) are suspected to have greater auditory processing impairments. However, it is unknown whether atypical auditory behaviors are related to receptive language and/or neural processing of sounds in ASD-MLV. In Experiment 1, we compared the percentage of time 47 ASD-MLV and 36 verbally fluent (ASD-V) participants, aged 5-21, displayed atypical auditory or visual sensory behaviors during the administration of the Autism Diagnostic Observation Schedule (ADOS). In Experiment 2, we tested whether atypical auditory behaviors were more frequent in ASD-MLV participants with receptive language deficits. In Experiment 3, we tested whether atypical auditory behaviors correlated with neural indices of sensitivity to perceptual sound differences as measured by the amplitude of neural responses to nonspeech intensity deviants. We found that ASD-MLV participants engaged in atypical auditory behaviors more often than ASD-V participants; in contrast, the incidence of atypical visual behaviors did not differ between the groups. Lower receptive language skills in the ASD-MLV group were predicted by greater incidence of atypical auditory behaviors. Exploratory analyses revealed a significant negative correlation between the amount of atypical auditory behaviors and the amplitude of neural response to deviants. Future work is needed to elucidate whether the relationship between atypical auditory behaviors and receptive language impairments in ASD-MLV individuals results from disruptions in the brain mechanisms involved in auditory processing. LAY SUMMARY: Minimally and low verbal children and adolescents with autism (ASD-MLV) displayed more atypical auditory behaviors (e.g., ear covering and humming) than verbally fluent participants with ASD. In ASD-MLV participants, time spent exhibiting such behaviors was associated with receptive vocabulary deficits and weaker neural responses to changes in sound loudness. Findings suggest that individuals with ASD with both severe expressive and receptive language impairments process sounds differently. Autism Res 2020, 13: 1718-1729. © 2020 International Society for Autism Research and Wiley Periodicals LLC.

Color is a perceptual construct that arises from neural processing in hierarchically organized cortical visual areas. Previous research, however, often failed to distinguish between neural responses driven by stimulus chromaticity versus perceptual color experience. An unsolved question is whether the neural responses at each stage of cortical processing represent a physical stimulus or a color we see. The present study dissociated the perceptual domain of color experience from the physical domain of chromatic stimulation at each stage of cortical processing by using a switch rivalry paradigm that caused the color percept to vary over time without changing the retinal stimulation. Using functional MRI (fMRI) and a model-based encoding approach, we found that neural representations in higher visual areas, such as V4 and VO1, corresponded to the perceived color, whereas responses in early visual areas V1 and V2 were modulated by the chromatic light stimulus rather than color perception. Our findings support a transition in the ascending human ventral visual pathway, from a representation of the chromatic stimulus at the retina in early visual areas to responses that correspond to perceptually experienced colors in higher visual areas.

A prominent source of polarised and entrenched beliefs is confirmation bias, where evidence against one’s position is selectively disregarded. This effect is most starkly evident when opposing parties are highly confident in their decisions. Here we combine human magnetoencephalography (MEG) with behavioural and neural modelling to identify alterations in post-decisional processing that contribute to the phenomenon of confirmation bias. We show that holding high confidence in a decision leads to a striking modulation of post-decision neural processing, such that integration of confirmatory evidence is amplified while disconfirmatory evidence processing is abolished. We conclude that confidence shapes a selective neural gating for choice-consistent information, reducing the likelihood of changes of mind on the basis of new information. A central role for confidence in shaping the fidelity of evidence accumulation indicates that metacognitive interventions may help ameliorate this pervasive cognitive bias., People often ignore evidence that disconfirms their prior beliefs. Here, the authors investigate the underlying cognitive, computational and neuronal mechanisms of such confirmation bias, and show that high confidence induces a selective neural processing of choice-consistent information.

In the last two decades, a considerable amount of work has been devoted to investigating the neural processing and dynamics of the primary taste cortex of rats. Surprisingly, much less information is available on cortical taste electrophysiology in awake mice, an animal model that is taking a more prominent role in taste research. Here we present electrophysiological evidence demonstrating how the gustatory cortex (GC) encodes information pertaining the basic taste qualities (sweet, salty, sour, and bitter) when stimuli are actively sampled through licking, the stereotyped behavior by which mice control the access of fluids in the mouth. Mice were trained to receive each stimulus on a fixed ratio schedule in which they had to lick a dry spout six times to receive a tastant on the seventh lick. Electrophysiological recordings confirmed that GC neurons encode both chemosensory and hedonic aspects of actively sampled tastants. In addition, our data revealed two other main findings; GC neurons encoded information about taste identity in as little as 120 ms. Consistent with the ability of GC neurons to rapidly encode taste information, nearly half of the recorded neurons exhibited spiking activity that was entrained to licking at rates up to 8 Hz. Overall, our results highlight how the GC of mice processes tastants when they are actively sensed through licking, reaffirming and expanding our knowledge on cortical taste processing.NEW & NOTEWORTHYRelatively little information is available on the neural dynamics of taste processing in the mouse gustatory cortex (GC). In this study we investigate how the GC encodes information of the qualities and hedonics of a broad panel of gustatory stimuli when tastants are actively sampled through licking. Our results show that the GC neurons broadly encode taste qualities but also process taste hedonics and licking information in a temporally dynamic manner.

Background Deficient extinction learning has been suggested as an important mechanism involved in the etiology of posttraumatic stress disorder. A key feature of posttraumatic stress disorder, reexperiencing the trauma in form of intrusions, may be linked to deficient extinction learning. This link is investigated in a novel, functional magnetic resonance imaging–compatible fear conditioning procedure that uses trauma films. Based on previous results, we expected deficient fear extinction indexed by exaggerated responding in the anterior insula and dorsal anterior cingulate cortex to predict subsequent intrusions. Methods A total of 58 healthy participants underwent acquisition and extinction learning with faces as conditioned stimuli (CS) and highly aversive 16-second films depicting interpersonal violence as unconditioned stimuli. During the subsequent 3 days, participants reported intrusive memories on their smartphone. Results Successful fear acquisition was evidenced by differential (CS+ > CS−) activity (threat cues associated with trauma films > cues paired only with neutral films) of a widespread network, including the anterior insula and dorsal anterior cingulate cortex, whereas extinction was characterized exclusively by differential anterior insula activity. Differential conditioned responding during late extinction in the anterior insula and dorsal anterior cingulate cortex was positively related to intrusive memory frequency independent of unconditioned stimuli responding. Exploratory analysis also revealed intrusion sensitivity of the hippocampus, rostral anterior cingulate cortex, and ventromedial prefrontal cortex, among others. Conclusions Results support the role of extinction learning in intrusive memory formation; a failure to uncouple conditioned emotional responding from external threat cues was associated with subsequent intrusive memories, representing a potential risk marker for developing posttraumatic stress disorder symptomatology after trauma.

One fundamental function of social norms is to promote social coordination. Moreover, greater social coordination may be called for when tight norms govern social relations with others. Hence, the sensitivity to social norm violations may be jointly modulated by relational goals and a belief that the social context is tight (vs loose). We tested this analysis using an electrocortical marker of norm-violation detection (N400). Ninety-one young American adults were subliminally primed with either relational or neutral goals. Then they saw behaviors that were either norm-violating or normal. In the relational priming condition, the norm-violation N400 increased as a function of the perceived tightness of societal norms. In the control priming condition, however, the norm-violation N400 was weak regardless of perceived tightness. Thus, normative tightness was associated with increased neural processing of norm violations only when relational goals were activated. Implications for norm psychology are discussed.

During language comprehension, online neural processing is strongly influenced by the constraints of the prior context. Although the N400 event-related potential (ERP) response (300–500 ms) is known to be sensitive to a word’s semantic predictability, less is known about a set of late positive-going ERP responses (600–1,000 ms) that can be elicited when an incoming word violates strong predictions about upcoming content (late frontal positivity) or about what is possible given the prior context (late posterior positivity/P600). Across three experiments, we systematically manipulated the length of the prior context and the source of lexical constraint to determine their influence on comprehenders’ online neural responses to these two types of prediction violations. In Experiment 1, within minimal contexts, both lexical prediction violations and semantically anomalous words produced a larger N400 than expected continuations ( James unlocked the door/laptop/gardener), but no late positive effects were observed. Critically, the late posterior positivity/P600 to semantic anomalies appeared when these same sentences were embedded within longer discourse contexts (Experiment 2a), and the late frontal positivity appeared to lexical prediction violations when the preceding context was rich and globally constraining (Experiment 2b). We interpret these findings within a hierarchical generative framework of language comprehension. This framework highlights the role of comprehension goals and broader linguistic context, and how these factors influence both top-down prediction and the decision to update or reanalyze the prior context when these predictions are violated.

The roots of psychopathology frequently take shape during infancy in the context of parent-infant interactions and adversity. Yet, neurobiological mechanisms linking these processes during infancy remain elusive. Here, using responses to attachment figures among infants who experienced adversity as a benchmark, we assessed rat pup cortical local field potentials (LFPs) and behaviors exposed to adversity in response to maternal rough and nurturing handling by examining its impact on pup separation-reunion with the mother. We show that during adversity, pup cortical LFP dynamic range decreased during nurturing maternal behaviors, but was minimally impacted by rough handling. During reunion, adversity-experiencing pups showed aberrant interactions with mother and blunted cortical LFP. Blocking pup stress hormone during either adversity or reunion restored typical behavior, LFP power, and cross-frequency coupling. This translational approach suggests adversity-rearing produces a stress-induced aberrant neurobehavioral processing of the mother, which can be used as an early biomarker of later-life pathology., The roots of psychopathology take shape during adverse parent-infant interactions, shown through infant attachment quality. Using rodents, the authors show that blunted infant cortical processing of the mother determines attachment quality through a stress hormone-dependent mechanism.