Павлова Анна Александровна

Intensive language-action therapy combined with anodal tDCS leads to verb generation improvements in non-fluent post-stroke aphasia

2019 · CHAPTER · en

Action-initiation brain circuitry is entrained by verb retrieval from semantic memory

2018 · CHAPTER · en

Stronger beta (15-30 Hz) suppression in higher-order areas of motor cortex accompanies more difficult search in semantic memory during verb generation task.

Combined CIAT-tDCS Therapy in Chronic Post-Stroke Aphasia Improves Neural Speech Processing: Neurophysiological and Behavioral Outcomes

2018 · CHAPTER · en

Intensive speech therapy was shown to lead to plastic changes reflected by lexical mismatch negativity (MMN) responses in aphasic patients (Mohr et al., 2016). Since many studies point to the role of the right hemisphere (RH) in aphasia recovery, noninvasive brain stimulation techniques (TMS, tDCS; Shah et al. 2013) usually target RH to facilitate this process. However, individual variance in stimulation-induced neural changes and resulting therapy outcomes are not understood. Here, 14 patients with chronic non-fluent mild-to-moderate aphasia caused by a left middle-cerebral artery stroke underwent Intensive Language-Action Therapy (ILAT, Pulvermüller, 2008) combined with anodal tDCS over the left IFG. To assess speech comprehension mechanisms, lexical MMN paradigm (120 deviant words vs. 487 standard pseudowords) was applied in MEG, before and after therapy for patients and once for a group of 10 controls. To improve the SNR of the responses, we applied a noise bootstrapping procedure with individual noise level computation. We found that the average power of the MMN response in the LH was significantly higher in the patients comparing to the healthy controls (p=0.01). Moreover, the variance of the MMN power increased significantly in the patient group after the treatment. This increase correlated with the behavioural improvements measured as a change of accuracy in a verb generation task (p=0.002). These changes were also associated with clinical improvements in speech comprehension measured by Russian Aphasia Test: scores in a sentence repetition subtest significantly increased after therapy (p = 0.035). No effects were found for the RH. Our results point to the compensatory role of the left hemisphere in the chronic stage of aphasia. They also highlight the role of individual variability in recovery of the language function, suggesting considerable individual differences in the recovery potential. The study continues to investigate these effects in larger samples.

Simultaneous processing of noun cue and to-be-produced verb in verb generation task: Electromagnetic evidence

2017 · ARTICLE · en

A long-standing but implicit assumption is that words strongly associated with a presented cue are automatically activated in the memory through rapid spread of activation within brain semantic networks. The current study was aimed to provide direct evidence of such rapid access to words’ semantic representations and to investigate its neural sources using magnetoencephalography (MEG) and distributed source localization technique. Thirty-three neurotypical subjects underwent the MEG recording during verb generation task, which was to produce verbs related to the presented noun cues. Brain responses evoked by the noun cues were examined while manipulating the strength of association between the noun and the potential verb responses. The strong vs. weak noun-verb association led to a greater noun-related neural response at 250–400 ms after cue onset, and faster verb production. The cortical sources of the differential response were localized in left temporal pole, previously implicated in semantic access, and left ventrolateral prefrontal cortex (VLPFC), thought to subserve controlled semantic retrieval. The strength of the left VLPFC’s response to the nouns with strong verb associates was positively correlated to the speed of verbs production. Our findings empirically validate the theoretical expectation that in case of a strongly connected noun-verb pair, successful access to target verb representation may occur already at the stage of lexico-semantic analysis of the presented noun. Moreover, the MEG results suggest that contrary to the previous conclusion derived from fMRI studies left VLPFC supports selection of the target verb representations, even if they were retrieved from semantic memory rapidly and effortlessly. The discordance between MEG and fMRI findings in verb generation task may stem from different modes of neural activation captured by phase-locked activity in MEG and slow changes of blood-oxygen-level-dependent (BOLD) signal in fMRI.

Not all reading is alike: Task modulation of magnetic evoked response to visual word

2017 · ARTICLE · en

Background. Previous studies have shown that brain response to a written word depends on the task: whether the word is a target in a version of lexical decision task or should be read silently. Although this effect has been interpreted as an evidence for an interaction between word recognition processes and task demands, it also may be caused by greater attention allocation to the target word. Objective. We aimed to examine the task effect on brain response evoked by nontarget written words. Design. Using MEG and magnetic source imaging, we compared spatial-temporal pattern of brain response elicited by a noun cue when it was read silently either without additional task (SR) or with a requirement to produce an associated verb (VG). Results. The task demands penetrated into early (200-300 ms) and late (500-800 ms) stages of a word processing by enhancing brain response under VG versus SR condition. The cortical sources of the early response were localized to bilateral inferior occipitotemporal and anterior temporal cortex suggesting that more demanding VG task required elaborated lexical-semantic analysis. The late effect was observed in the associative auditory areas in middle and superior temporal gyri and in motor representation of articulators. Our results suggest that a remote goal plays a pivotal role in enhanced recruitment of cortical structures underlying orthographic, semantic and sensorimotor dimensions of written word perception from the early processing stages. Surprisingly, we found that to fulfil a more challenging goal the brain progressively engaged resources of the right hemisphere throughout all stages of silent reading Conclusion. Our study demonstrates that a deeper processing of linguistic input amplifies activation of brain areas involved in integration of speech perception and production. This is consistent with theories that emphasize the role of sensorimotor integration in speech understanding.

Visual word recognition differs in silent reading and verb generation tasks: An MEG study

2017 · CHAPTER · en

Previous studies showed that the brain response to a written word depends on whether the word is a target of a lexico-semantic task or is only read. Here we aimed to examine whether the task that uses the presented word not as the target but a cue to produce another word still modifies its recognition process. Using MEG and magnetic source imaging, we compared the spatio-temporal pattern of the brain responses elicited by a noun cue when it was read silently, either without an additional task (SR) or with a requirement to produce an associated verb (VG). We found that the task demands penetrated into early (200 - 300 ms) and late (500 - 800 ms) stages of written word processing by enhancing the brain response under the VG versus SR condition. The cortical sources of the early differential response were localized to the bilateral inferior occipito-temporal and anterior temporal cortices, suggesting elaborate orthographic and lexico-semantic analysis in the VG task. A late effect was observed in the middle and superior temporal gyri and the motor representation of articulators bilaterally and can be associated with enhanced sensorimotor transformations under the VG condition. Overall, our results suggest that written word processing depends on the task goal while intensified linguistic processing recruits bilaterally lateralized networks.

The task demands and retrieval success shape the MEG evoked response to noun cue in the verb generation task.

2016 · CHAPTER · en

A crucial process for speech production is the retrieval of a target words from mental lexicon. People are remarkably fast and accurate in this process: when we speak we correctly retrieve the intended word from a repository containing several thousand items less than in half a second.

Исследование соотношения автоматических и контролируемых процессов обработки информации у больных шизофренией

2015 · ARTICLE · ru

С целью исследовать нарушения внимания при шизофрении 15 пациентам с диагнозом F20.0 «Параноидная шизофрения» и 15 здоровым испытуемым были предложены 2 типа заданий на зрительный поиск. Значимых различий в эффективности зрительного поиска обнаружено не было ни для автоматических, ни для контролируемых процессов обработки информации. Была предпринята попытка объединить оба типа заданий в парадигме «слепота по невниманию». В апробации на 9 испытуемых получить эффект «слепоты» не удалось