Neural representation of phonological wordform in temporal cortex.

While the neural bases of the earliest stages of speech categorization have been widely explored using neural decoding methods, there is still a lack of consensus on questions as basic as how wordforms are represented and in what way this word-level representation influences downstream processing in the brain. Isolating and localizing the neural representations of wordform is challenging because spoken words activate a variety of representations (e.g., segmental, semantic, articulatory) in addition to form-based representations. We addressed these challenges through a novel integrated neural decoding and effective connectivity design using region of interest (ROI)-based, source-reconstructed magnetoencephalography/electroencephalography (MEG/EEG) data collected during a lexical decision task. To identify wordform representations, we trained classifiers on words and nonwords from different phonological neighborhoods and then tested the classifiers' ability to discriminate between untrained target words that overlapped phonologically with the trained items. Training with word neighbors supported significantly better decoding than training with nonword neighbors in the period immediately following target presentation. Decoding regions included mostly right hemisphere regions in the posterior temporal lobe implicated in phonetic and lexical representation. Additionally, neighbors that aligned with target word beginnings (critical for word recognition) supported decoding, but equivalent phonological overlap with word codas did not, suggesting lexical mediation. Effective connectivity analyses showed a rich pattern of interaction between ROIs that support decoding based on training with lexical neighbors, especially driven by right posterior middle temporal gyrus. Collectively, these results evidence functional representation of wordforms in temporal lobes isolated from phonemic or semantic representations.

Neural representation of phonological wordform in bilateral posterior temporal cortex.

While the neural bases of the earliest stages of speech categorization have been widely explored using neural decoding methods, there is still a lack of consensus on questions as basic as how wordforms are represented and in what way this word-level representation influences downstream processing in the brain. Isolating and localizing the neural representations of wordform is challenging because spoken words evoke activation of a variety of representations (e.g., segmental, semantic, articulatory) in addition to form-based representations. We addressed these challenges through a novel integrated neural decoding and effective connectivity design using region of interest (ROI)-based, source reconstructed magnetoencephalography/electroencephalography (MEG/EEG) data collected during a lexical decision task. To localize wordform representations, we trained classifiers on words and nonwords from different phonological neighborhoods and then tested the classifiers' ability to discriminate between untrained target words that overlapped phonologically with the trained items. Training with either word or nonword neighbors supported decoding in many brain regions during an early analysis window (100-400 ms) reflecting primarily incremental phonological processing. Training with word neighbors, but not nonword neighbors, supported decoding in a bilateral set of temporal lobe ROIs, in a later time window (400-600 ms) reflecting activation related to word recognition. These ROIs included bilateral posterior temporal regions implicated in wordform representation. Effective connectivity analyses among regions within this subset indicated that word-evoked activity influenced the decoding accuracy more than nonword-evoked activity did. Taken together, these results evidence functional representation of wordforms in bilateral temporal lobes isolated from phonemic or semantic representations.

Abstract representations in temporal cortex support generative linguistic processing.

Generativity, the ability to create and evaluate novel constructions, is a fundamental property of human language and cognition. The productivity of generative processes is determined by the scope of the representations they engage. Here we examine the neural representation of reduplication, a productive phonological process that can create novel forms through patterned syllable copying (e.g. ba-mih → ba-ba-mih, ba-mih-mih, or ba-mih-ba). Using MRI-constrained source estimates of combined MEG/EEG data collected during an auditory artificial grammar task, we identified localized cortical activity associated with syllable reduplication pattern contrasts in novel trisyllabic nonwords. Neural decoding analyses identified a set of predominantly right hemisphere temporal lobe regions whose activity reliably discriminated reduplication patterns evoked by untrained, novel stimuli. Effective connectivity analyses suggested that sensitivity to abstracted reduplication patterns was propagated between these temporal regions. These results suggest that localized temporal lobe activity patterns function as abstract representations that support linguistic generativity.

A Secondary Analysis on Effects of Theta Burst Transcranial Magnetic Stimulation to Reduce Anger in Veterans With Posttraumatic Stress Disorder.

INTRODUCTION: Anger is an important clinical feature of posttraumatic stress disorder (PTSD) that can hamper recovery. We recently reported that intermittent theta burst stimulation (iTBS) demonstrated preliminary efficacy to reduce symptoms of posttraumatic stress disorder and major depression; here, we performed a secondary analysis testing whether iTBS reduced symptoms of anger over the course of iTBS treatment and compared to sham stimulation. MATERIALS AND METHODS: Fifty veterans with chronic PTSD received ten daily sessions of sham-controlled, double-blind iTBS (1800 pulses/session, once per weekday) targeting the right dorsolateral prefrontal cortex (intent-to-treat = 25 per group). Participants who completed the double-blind phase were offered another ten sessions of unblinded iTBS. Participants completed the Dimensions of Anger Reactions scale at pre-iTBS baseline, treatment midpoints, and endpoints of the blinded and unblinded phases, and at one-month after the last stimulation session. Correlations between anger, PTSD, depression, and sleep were also explored. RESULTS: After the first week, during the double-blind phase, participants randomized to active stimulation reported significantly reduced anger compared to sham stimulation (p = 0.04). Participants initially randomized to sham appeared to catch-up to the point they no longer differed from those initially randomized to active iTBS when they received iTBS during the unblinded phase (p = 0.14). Anger reduction was maintained at one-month after iTBS in participants initially randomized to active stimulation (i.e., total of four weeks of iTBS). CONCLUSIONS: This secondary analysis suggests that iTBS might reduce anger in veterans with PTSD. Future studies focused on more granular level anger outcomes and effects of number of stimulation sessions are needed.

Non-invasive Brain Stimulation for Alcohol Use Disorders: State of the Art and Future Directions.

Alcohol use disorders remain one of the leading causes of mortality and morbidity across the world, yet despite this impact, there are few treatment options for patients suffering from these disorders. To this end, non-invasive brain stimulation, most commonly utilizing technologies including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has recently emerged as promising potential treatments for alcohol use disorders. Enthusiasm for these interventions is fueled by their non-invasive nature, generally favorable safety profile, and ability to target and modulate brain regions implicated in substance use disorders. In this paper, we describe the underlying principles behind these commonly used stimulation technologies, summarize existing experiments and randomized controlled trials, and provide an integrative summary with suggestions for future areas of research. Currently available data generally supports the use of non-invasive brain stimulation as a near-term treatment for alcohol use disorder, with important caveats regarding the use of stimulation in this patient population.