Interictal epileptiform discharges contribute to word-finding difficulty in epilepsy through multiple cognitive mechanisms.

OBJECTIVE: Cognitive impairment often impacts quality of life in epilepsy even if seizures are controlled. Word-finding difficulty is particularly prevalent and often attributed to etiological (static, baseline) circuit alterations. We sought to determine whether interictal discharges convey significant superimposed contributions to word-finding difficulty in patients, and if so, through which cognitive mechanism(s). METHODS: Twenty-three patients undergoing intracranial monitoring for drug-resistant epilepsy participated in multiple tasks involving word production (auditory naming, short-term verbal free recall, repetition) to probe word-finding difficulty across different cognitive domains. We compared behavioral performance between trials with versus without interictal discharges across six major brain areas and adjusted for intersubject differences using mixed-effects models. We also evaluated for subjective word-finding difficulties through retrospective chart review. RESULTS: Subjective word-finding difficulty was reported by the majority (79%) of studied patients preoperatively. During intracranial recordings, interictal epileptiform discharges (IEDs) in the medial temporal lobe were associated with long-term lexicosemantic memory impairments as indexed by auditory naming (p = .009), in addition to their established impact on short-term verbal memory as indexed by free recall (p = .004). Interictal discharges involving the lateral temporal cortex and lateral frontal cortex were associated with delayed reaction time in the auditory naming task (p = .016 and p = .018), as well as phonological working memory impairments as indexed by repetition reaction time (p = .002). Effects of IEDs across anatomical regions were strongly dependent on their precise timing within the task. SIGNIFICANCE: IEDs appear to act through multiple cognitive mechanisms to form a convergent basis for the debilitating clinical word-finding difficulty reported by patients with epilepsy. This was particularly notable for medial temporal spikes, which are quite common in adult focal epilepsy. In parallel with the treatment of seizures, the modulation of interictal discharges through emerging pharmacological means and neurostimulation approaches may be an opportunity to help address devastating memory and language impairments in epilepsy.

Latent neural dynamics encode temporal context in speech.

Direct neural recordings from human auditory cortex have demonstrated encoding for acoustic-phonetic features of consonants and vowels. Neural responses also encode distinct acoustic amplitude cues related to timing, such as those that occur at the onset of a sentence after a silent period or the onset of the vowel in each syllable. Here, we used a group reduced rank regression model to show that distributed cortical responses support a low-dimensional latent state representation of temporal context in speech. The timing cues each capture more unique variance than all other phonetic features and exhibit rotational or cyclical dynamics in latent space from activity that is widespread over the superior temporal gyrus. We propose that these spatially distributed timing signals could serve to provide temporal context for, and possibly bind across time, the concurrent processing of individual phonetic features, to compose higher-order phonological (e.g. word-level) representations.

Phase Alignment of Low-Frequency Neural Activity to the Amplitude Envelope of Speech Reflects Evoked Responses to Acoustic Edges, Not Oscillatory Entrainment.

The amplitude envelope of speech is crucial for accurate comprehension. Considered a key stage in speech processing, the phase of neural activity in the theta-delta bands (1-10 Hz) tracks the phase of the speech amplitude envelope during listening. However, the mechanisms underlying this envelope representation have been heavily debated. A dominant model posits that envelope tracking reflects entrainment of endogenous low-frequency oscillations to the speech envelope. Alternatively, envelope tracking reflects a series of evoked responses to acoustic landmarks within the envelope. It has proven challenging to distinguish these two mechanisms. To address this, we recorded MEG while participants (n = 12, 6 female) listened to natural speech, and compared the neural phase patterns to the predictions of two computational models: an oscillatory entrainment model and a model of evoked responses to peaks in the rate of envelope change. Critically, we also presented speech at slowed rates, where the spectro-temporal predictions of the two models diverge. Our analyses revealed transient theta phase-locking in regular speech, as predicted by both models. However, for slow speech, we found transient theta and delta phase-locking, a pattern that was fully compatible with the evoked response model but could not be explained by the oscillatory entrainment model. Furthermore, encoding of acoustic edge magnitudes was invariant to contextual speech rate, demonstrating speech rate normalization of acoustic edge representations. Together, our results suggest that neural phase-locking to the speech envelope is more likely to reflect discrete representation of transient information rather than oscillatory entrainment.SIGNIFICANCE STATEMENT This study probes a highly debated topic in speech perception: the neural mechanisms underlying the cortical representation of the temporal envelope of speech. It is well established that the slow intensity profile of the speech signal, its envelope, elicits a robust brain response that "tracks" these envelope fluctuations. The oscillatory entrainment model posits that envelope tracking reflects phase alignment of endogenous neural oscillations. Here the authors provide evidence for a distinct mechanism. They show that neural speech envelope tracking arises from transient evoked neural responses to rapid increases in the speech envelope. Explicit computational modeling provides direct and compelling evidence that evoked responses are the primary mechanism underlying cortical speech envelope representations, with no evidence for oscillatory entrainment.

Anatomical and behavioral correlates of auditory perception in developmental dyslexia.

Developmental dyslexia (DD) is typically associated with difficulties in manipulating speech sounds and, sometimes, in basic auditory processing. However, the neuroanatomical correlates of auditory difficulties in DD and their contribution to individual clinical phenotypes are still unknown. Recent intracranial electrocorticography (ECoG) findings associated processing of sound amplitude rises and speech sounds with posterior and middle superior temporal gyrus (STG), respectively. We hypothesize that regional STG anatomy will relate to specific auditory abilities in DD and that auditory processing abilities will relate to behavioral difficulties. One hundred and ten children (78 DD, 32 typically developing, age 7-15 years) completed amplitude rise time (ART) and speech in noise discrimination (SiN) tasks. They also underwent a battery of cognitive tests. Anatomical MRI scans were used to identify regions in which local cortical gyrification complexity correlated with auditory tasks in DD. Behaviorally, ART but not SiN performance was impaired in DD. Neurally, ART and SiN performance correlated with gyrification in posterior STG and middle STG, respectively. Furthermore, ART significantly contributed to reading impairments in DD, while SiN explained variance in phonological awareness only. Finally, ART and SiN performance was not correlated, and each task was correlated with distinct neuropsychological measures, such that distinct DD subgroups could be identified. Overall, we provide a direct link between the neurodevelopment of the left STG and individual variability in auditory processing abilities in DD. The dissociation between speech and non-speech deficits supports distinct DD phenotypes and implicates different approaches to interventions.

Vowel and formant representation in the human auditory speech cortex.

Vowels, a fundamental component of human speech across all languages, are cued acoustically by formants, resonance frequencies of the vocal tract shape during speaking. An outstanding question in neurolinguistics is how formants are processed neurally during speech perception. To address this, we collected high-density intracranial recordings from the human speech cortex on the superior temporal gyrus (STG) while participants listened to continuous speech. We found that two-dimensional receptive fields based on the first two formants provided the best characterization of vowel sound representation. Neural activity at single sites was highly selective for zones in this formant space. Furthermore, formant tuning is adjusted dynamically for speaker-specific spectral context. However, the entire population of formant-encoding sites was required to accurately decode single vowels. Overall, our results reveal that complex acoustic tuning in the two-dimensional formant space underlies local vowel representations in STG. As a population code, this gives rise to phonological vowel perception.

Face masks drive increased rational decision-making.

Face masks play a pivotal role in the control of respiratory diseases, such as the novel coronavirus (COVID-19). Despite their widespread use, little is known about how face masks affect human social interaction. Using unique experimental data collected early on in the pandemic, we investigate how facial occlusion by face masks alters socio-economic exchange. In a behavioral economics study (N = 481), individuals accepted more monetary offers and lower offer amounts when interacting with a masked versus unmasked opponent. Importantly, this effect was mainly driven by faces covered with surgical masks relative to bandana-type masks. In the first weeks of mask use during the COVID-19 pandemic, motive attributions further moderated this effect: Participants who believed that mask wearers were seeking to protect others showed the highest acceptance rates. Overall, we describe a new phenomenon, the face-mask effect on socio-economic exchange, and show that it is modulated by contextual factors.

Risk perception and optimism during the early stages of the COVID-19 pandemic.

Slowing the spread of COVID-19 requires people to actively change their lives by following protective practices, such as physical distancing and disinfecting their hands. Perceptions about the personal risk of COVID-19 may affect compliance with these practices. In this study, we assessed risk perception and optimism about COVID-19 in a multinational (UK, USA and Germany), longitudinal design during the early stages of the pandemic (16 March 2020; 1 April 2020; 20 May 2020). Our main findings are that (i) people showed a comparative optimism bias about getting infected and infecting others, but not for getting severe symptoms, (ii) this optimism bias did not change over time, (iii) optimism bias seemed to relate to perceived level of control over the action, (iv) risk perception was linked to publicly available information about the disorder, (v) people reported adhering closely to protective measures but these measures did not seem to be related to risk perception, and (vi) risk perception was related to questions about stress and anxiety. In additional cross-sectional samples, we replicated our most important findings. Our open and partly preregistered results provide detailed descriptions of risk perceptions and optimistic beliefs during the early stages of the COVID-19 pandemic in three Western countries.

Parallel and distributed encoding of speech across human auditory cortex.

Speech perception is thought to rely on a cortical feedforward serial transformation of acoustic into linguistic representations. Using intracranial recordings across the entire human auditory cortex, electrocortical stimulation, and surgical ablation, we show that cortical processing across areas is not consistent with a serial hierarchical organization. Instead, response latency and receptive field analyses demonstrate parallel and distinct information processing in the primary and nonprimary auditory cortices. This functional dissociation was also observed where stimulation of the primary auditory cortex evokes auditory hallucination but does not distort or interfere with speech perception. Opposite effects were observed during stimulation of nonprimary cortex in superior temporal gyrus. Ablation of the primary auditory cortex does not affect speech perception. These results establish a distributed functional organization of parallel information processing throughout the human auditory cortex and demonstrate an essential independent role for nonprimary auditory cortex in speech processing.

Risk incidence of fractures and injuries: a multicenter video-EEG study of 626 generalized convulsive seizures.

OBJECTIVE: To evaluate the incidence and risk factors of generalized convulsive seizure (GCS)-related fractures and injuries during video-EEG monitoring. METHODS: We analyzed all GCSs in patients undergoing video-EEG-monitoring between 2007 and 2019 at epilepsy centers in Frankfurt and Marburg in relation to injuries, falls and accidents associated with GCSs. Data were gathered using video material, EEG material, and a standardized reporting form. RESULTS: A total of 626 GCSs from 411 patients (mean age: 33.6 years; range 3-74 years; 45.0% female) were analyzed. Severe adverse events (SAEs) such as fractures, joint luxation, corneal erosion, and teeth loosening were observed in 13 patients resulting in a risk of 2.1% per GCS (95% CI 1.2-3.4%) and 3.2% per patient (95% CI 1.8-5.2%). Except for a nasal fracture due to a fall onto the face, no SAEs were caused by falls, and all occurred in patients lying in bed without evidence of external trauma. In seven patients, vertebral body compression fractures were confirmed by imaging. This resulted in a risk of 1.1% per GCS (95% CI 0.5-2.2%) and 1.7% per patient (95% CI 0.8-3.3%). These fractures occurred within the tonic phase of a GCS and were accompanied by a characteristic cracking noise. All affected patients reported back pain spontaneously, and an increase in pain on percussion of the affected spine section. CONCLUSIONS: GCSs are associated with a substantial risk of fractures and shoulder dislocations that are not associated with falls. GCSs accompanied by audible cracking, and resulting in back pain, should prompt clinical and imaging evaluations.

The neurocognitive signature of focus alternatives.

Focus alternatives are words/phrases that can substitute for the focused constituent of an utterance. In "Carsten has picked [CHERRIES]F from the tree.", (marked by pitch focus on cherries), the speaker wants to not only convey the fact that Carsten has picked cherries, but also to contrast cherries with other fruit that could have been picked, such as plums. Although focus alternatives are key to understanding the implicit aspects of an utterance, nothing is known about their neural representation. We directly contrasted neural representations of lexico-semantic similarity and focus alternative status using fMRI. Semantic relatedness was reflected in decreased activation in the bilateral superior temporal gyri. By contrast, processing of focus alternatives induced increased activations in the precuneus and the fronto-median wall, two regions previously implicated in discourse processing. These results suggest that focus alternative status is processed separately from semantic relatedness, at the level of discourse integration.

The framing effect in a monetary gambling task is robust in minimally verbal language switching contexts.

Decision-making biases, in particular the framing effect, can be altered in foreign language settings (foreign language effect) and following switching between languages (the language switching effect on framing). Recently, it has been suggested that the framing effect is only affected by foreign language use if the task is presented in a rich textual form. Here, we assess whether an elaborate verbal task is also a prerequisite for the language switching effect on framing. We employed a financial gambling task that induces a robust framing effect but is less verbal than the classical framing paradigms (e.g., the Asian disease problem). We conducted an online experiment ( n = 485), where we orthogonally manipulated language use and language switching between trials. The results showed no effects of foreign language use or language switching throughout the experiment. This online result was confirmed in a laboratory experiment ( n = 27). Overall, we find that language switching does not reduce the framing effect in a paradigm with little verbal content and thus that language switching effects seem contingent on the amount of verbal processing required.

Low foreign language proficiency reduces optimism about the personal future.

Optimistic estimates about the personal future constitute one of the best-described and most-debated decision biases related to emotion. Nevertheless, it has been difficult to isolate manipulations that reduce optimistic estimates. Eliciting estimates in a foreign language is a promising candidate manipulation because foreign language use alters decision biases in scenarios with emotional components. Consequently, we tested whether foreign language use reduces optimistic estimates. In a laboratory experiment, participants ( n = 45) estimated their probability of experiencing life events either in their native language or a foreign language, in which they were highly proficient. We found no differences in these estimates or in the updating of these estimates after receiving feedback about the population baseline probability. Importantly, three online experiments with large sample sizes ( ns = 706, 530, and 473) showed that using a foreign language with low proficiency reduced comparative optimism. Participants in the online experiments had diverse proficiency levels and were matched on a variety of control metrics. Fine-grained analyses indicated that low proficiency weakens the coupling between probability estimates and rated arousal. Overall, our findings suggest that an important decision bias can be reduced when using a foreign language with low proficiency.

A speech envelope landmark for syllable encoding in human superior temporal gyrus.

The most salient acoustic features in speech are the modulations in its intensity, captured by the amplitude envelope. Perceptually, the envelope is necessary for speech comprehension. Yet, the neural computations that represent the envelope and their linguistic implications are heavily debated. We used high-density intracranial recordings, while participants listened to speech, to determine how the envelope is represented in human speech cortical areas on the superior temporal gyrus (STG). We found that a well-defined zone in middle STG detects acoustic onset edges (local maxima in the envelope rate of change). Acoustic analyses demonstrated that timing of acoustic onset edges cues syllabic nucleus onsets, while their slope cues syllabic stress. Synthesized amplitude-modulated tone stimuli showed that steeper slopes elicited greater responses, confirming cortical encoding of amplitude change, not absolute amplitude. Overall, STG encoding of the timing and magnitude of acoustic onset edges underlies the perception of speech temporal structure.

A hard-to-read font reduces the framing effect in a large sample.

How can apparent decision biases, such as the framing effect, be reduced? Intriguing findings within recent years indicate that foreign language settings reduce framing effects, which has been explained in terms of deeper cognitive processing. Because hard-to-read fonts have been argued to trigger deeper cognitive processing, so-called cognitive disfluency, we tested whether hard-to-read fonts reduce framing effects. We found no reliable evidence for an effect of hard-to-read fonts on four framing scenarios in a laboratory (final N = 158) and an online study (N = 271). However, in a preregistered online study with a rather large sample (N = 732), a hard-to-read font reduced the framing effect in the classic "Asian disease" scenario (in a one-sided test). This suggests that hard-read-fonts can modulate decision biases-albeit with rather small effect sizes. Overall, our findings stress the importance of large samples for the reliability and replicability of modulations of decision biases.

Second Language Use Facilitates Implicit Emotion Regulation via Content Labeling.

Previous studies reported that negative stimuli induced less affect in bilinguals when stimuli were presented in bilinguals' second, weaker language (L2) than when they were presented in their native language (L1). This effect of L2 use was attributed to increased emotional distance as well as to increased levels of cognitive control during L2 use. Here we investigated how explicit (cognitive reappraisal, i.e., reinterpreting the meaning of the emotional stimulus to alter its emotional impact) and implicit (content labeling, i.e., categorizing the content of the image; and emotion labeling, i.e., naming the emotion induced by the emotional stimulus) emotion regulation strategies are altered in an L2 (English) context in German native speakers with medium to high proficiency in their L2. While previous studies used linguistic stimuli, such as words, to induce affect, here we used images to test whether reduced affect could also be observed for non-linguistic stimuli when presented in an L2 context. We hypothesized that the previously implicated increase in emotional distance and cognitive control in an L2 would result in an L2 advantage in emotion regulation (i.e., leading to less negative emotions compared to an L1 context), by strengthening the effect of linguistic re-evaluation on the evoked emotions. Using a classic emotion regulation paradigm, we examined changes in subjective emotional state ratings during reappraisal, emotion labeling and content labeling in a L1 and L2 context. We found that the strength of evoked affective responses did not depend on the language context in which an image was presented. Crucially, content labeling in L2 was more effective than in L1, whereas emotion labeling did not differ between languages. Overall, evoked responses were regulated most effectively through explicit emotion regulation (reappraisal) in L1 and L2 context. These results demonstrate an L2 advantage effect for emotion regulation through content labeling and suggest that L2 context alters sub-processes implicated in content labeling but not emotion labeling.

Activation Patterns throughout the Word Processing Network of L1-dominant Bilinguals Reflect Language Similarity and Language Decisions.

A crucial aspect of bilingual communication is the ability to identify the language of an input. Yet, the neural and cognitive basis of this ability is largely unknown. Moreover, it cannot be easily incorporated into neuronal models of bilingualism, which posit that bilinguals rely on the same neural substrates for both languages and concurrently activate them even in monolingual settings. Here we hypothesized that bilinguals can employ language-specific sublexical (bigram frequency) and lexical (orthographic neighborhood size) statistics for language recognition. Moreover, we investigated the neural networks representing language-specific statistics and hypothesized that language identity is encoded in distributed activation patterns within these networks. To this end, German-English bilinguals made speeded language decisions on visually presented pseudowords during fMRI. Language attribution followed lexical neighborhood sizes both in first (L1) and second (L2) language. RTs revealed an overall tuning to L1 bigram statistics. Neuroimaging results demonstrated tuning to L1 statistics at sublexical (occipital lobe) and phonological (temporoparietal lobe) levels, whereas neural activation in the angular gyri reflected sensitivity to lexical similarity to both languages. Analysis of distributed activation patterns reflected language attribution as early as in the ventral stream of visual processing. We conclude that in language-ambiguous contexts visual word processing is dominated by L1 statistical structure at sublexical orthographic and phonological levels, whereas lexical search is determined by the structure of both languages. Moreover, our results demonstrate that language identity modulates distributed activation patterns throughout the reading network, providing a key to language identity representations within this shared network.

Slower Perception Followed by Faster Lexical Decision in Longer Words: A Diffusion Model Analysis.

Effects of stimulus length on reaction times (RTs) in the lexical decision task are the topic of extensive research. While slower RTs are consistently found for longer pseudo-words, a finding coined the word length effect (WLE), some studies found no effects for words, and yet others reported faster RTs for longer words. Moreover, the WLE depends on the orthographic transparency of a language, with larger effects in more transparent orthographies. Here we investigate processes underlying the WLE in lexical decision in German-English bilinguals using a diffusion model (DM) analysis, which we compared to a linear regression approach. In the DM analysis, RT-accuracy distributions are characterized using parameters that reflect latent sub-processes, in particular evidence accumulation and decision-independent perceptual encoding, instead of typical parameters such as mean RT and accuracy. The regression approach showed a decrease in RTs with length for pseudo-words, but no length effect for words. However, DM analysis revealed that the null effect for words resulted from opposing effects of length on perceptual encoding and rate of evidence accumulation. Perceptual encoding times increased with length for words and pseudo-words, whereas the rate of evidence accumulation increased with length for real words but decreased for pseudo-words. A comparison between DM parameters in German and English suggested that orthographic transparency affects perceptual encoding, whereas effects of length on evidence accumulation are likely to reflect contextual information and the increase in available perceptual evidence with length. These opposing effects may account for the inconsistent findings on WLEs.

Poor anchoring limits dyslexics' perceptual, memory, and reading skills.

The basic deficits underlying the severe and persistent reading difficulties in dyslexia are still highly debated. One of the major topics of debate is whether these deficits are language specific, or affect both verbal and non-verbal stimuli. Recently, Ahissar and colleagues proposed the "anchoring-deficit hypothesis" (Ahissar, Lubin, Putter-Katz, & Banai, 2006), which suggests that dyslexics have a general difficulty in automatic extraction of stimulus regularities from auditory inputs. This hypothesis explained a broad range of dyslexics' verbal and non-verbal difficulties. However, it was not directly tested in the context of reading and verbal memory, which poses the main stumbling blocks to dyslexics. Here we assessed the abilities of adult dyslexics to efficiently benefit from ("anchor to") regularities embedded in repeated tones, orally presented syllables, and written words. We also compared dyslexics' performance to that of individuals with attention disorder (ADHD), but no reading disability. We found an anchoring effect in all groups: all gained from stimulus repetition. However, in line with the anchoring-deficit hypothesis, controls and ADHD participants showed a significantly larger anchoring effect in all tasks. This study is the first that directly shows that the same domain-general deficit, poor anchoring, characterizes dyslexics' performance in perceptual, working memory and reading tasks.