Reduced Interference and Serial Dependency Effects for Naming in Older but not Younger Adults after 1 Hz rTMS of Right Pars Triangularis

1 Hz rTMS was used to decrease excitability of right pars triangularis (R PTr) to determine whether increased R PTr activity during picture naming in older adults hampers word finding. We hypothesized that decreasing R PTr excitability would reduce interference with word finding, facilitating faster picture naming. 15 older and 16 younger adults received two rTMS sessions. In one, speech onset latencies for picture naming were measured after both sham and active R PTr stimulation. In the other session, sham and active stimulation of a control region, right pars opercularis (R POp), were administered before picture naming. Order of active vs. sham stimulation within session was counterbalanced. Younger adults showed no significant effects of stimulation. In older adults, a trend indicated that participants named pictures more quickly after active than sham R PTr stimulation. However, older adults also showed longer responses during R PTr than R POp sham stimulation. When order of active vs. sham stimulation was modeled, older adults receiving active stimulation first had significantly faster responding after active than sham R PTr stimulation and significantly faster responding after R PTr than R POp stimulation, consistent with experimental hypotheses. However, older adults receiving sham stimulation first showed no significant differences between conditions. Findings are best understood, based on previous studies, when the interaction between the excitatory effects of picture naming and the inhibitory effects of 1 Hz rTMS on R PTr is considered. Implications regarding right frontal activity in older adults and for design of future experiments are discussed.

Electrophysiological correlates of confidence differ across correct and erroneous perceptual decisions

Every decision we make is accompanied by an estimate of the likelihood that our decision is accurate or appropriate. This likelihood estimate is termed our degree of decision confidence. Recent work has uncovered event-related potential (ERP) correlates of confidence both during decision formation and after a decision has been made. However, the interpretation of these findings is complicated by methodological issues related to ERP amplitude measurement that are prevalent across existing studies. To more accurately characterise the neural correlates of confidence, we presented participants with a difficult perceptual decision task that elicited a broad range of confidence ratings. We identified a frontal ERP component within an onset prior to the behavioural response, which exhibited more positive-going amplitudes in trials with higher confidence ratings. This frontal effect also biased measures of the centro-parietal positivity (CPP) component at parietal electrodes via volume conduction. Amplitudes of the error positivity (Pe) component that followed each decision were negatively associated with confidence for trials with decision errors, but not for trials with correct decisions. We provide evidence for both pre- and post- decisional neural correlates of decision confidence that are observed in trials with correct and erroneous decisions, respectively. Our findings suggest that certainty in having made a correct response is associated with frontal activity during decision formation, whereas certainty in having committed an error is instead associated with the post-decisional Pe component. We additionally show that some previously reported associations between decision confidence and CPP/Pe component amplitudes are (at least partly) a consequence of ERP amplitude measurement-related confounds.

Words and Faces on Left and Right: Perceptual Asymmetries as a Marker for SSRI Responsiveness

<p>Vulnerability to depression has been associated with greater relative right hemisphere frontal activity, as measured by EEG recordings of alpha activity. However, there is much heterogeneity in the patterns of hemispheric asymmetries in people at risk for depression. These different patterns of hemispheric asymmetries may be related to whether an individual responds to Selective Serotonin Reuptake Inhibitor (SSRI) medication. Response to SSRIs is associated with a pattern of overall relative LH activity, whereas non-response to SSRIs is associated with a pattern of overall relative RH activity. Very little is known about how these asymmetries in neural activity relate to asymmetries in cognition. The current study investigated hemispheric differences in the processing of emotional faces and words, in individuals not vulnerable to depression (a Never Depressed group) and in individuals vulnerable to depression (a Previously Depressed group). In the chimeric faces task, the Previously Depressed group had a significantly larger left hemispatial bias compared to the Never Depressed group. This may reflect relatively greater posterior RH activity/arousal in the Previously Depressed group. No differences were found between SSRI Responders and Non-responders in the chimeric faces task. In the divided visual field task, hemispheric differences in the processing of emotional words were found between the SSRI Responders and SSRI Non-responders. In contrast to SSRI Responders and Never Depressed controls, SSRI Non-responders showed a relative advantage for negative over positive words when they were presented to their LVF/RH; and an advantage for negative words presented to their LVF/RH compared to their RVF/LH. Additionally, they were more sensitive to perceiving the valence of a word that was presented to their LVF/RH. This suggests that their RH semantic systems may differ from that of SSRI Responders and Never Depressed controls. Genetic, hormonal and cognitive factors are discussed in relation to these patterns of hemispheric asymmetries and responsiveness to SSRI medication.</p>

Words and Faces on Left and Right: Perceptual Asymmetries as a Marker for SSRI Responsiveness

<p>Vulnerability to depression has been associated with greater relative right hemisphere frontal activity, as measured by EEG recordings of alpha activity. However, there is much heterogeneity in the patterns of hemispheric asymmetries in people at risk for depression. These different patterns of hemispheric asymmetries may be related to whether an individual responds to Selective Serotonin Reuptake Inhibitor (SSRI) medication. Response to SSRIs is associated with a pattern of overall relative LH activity, whereas non-response to SSRIs is associated with a pattern of overall relative RH activity. Very little is known about how these asymmetries in neural activity relate to asymmetries in cognition. The current study investigated hemispheric differences in the processing of emotional faces and words, in individuals not vulnerable to depression (a Never Depressed group) and in individuals vulnerable to depression (a Previously Depressed group). In the chimeric faces task, the Previously Depressed group had a significantly larger left hemispatial bias compared to the Never Depressed group. This may reflect relatively greater posterior RH activity/arousal in the Previously Depressed group. No differences were found between SSRI Responders and Non-responders in the chimeric faces task. In the divided visual field task, hemispheric differences in the processing of emotional words were found between the SSRI Responders and SSRI Non-responders. In contrast to SSRI Responders and Never Depressed controls, SSRI Non-responders showed a relative advantage for negative over positive words when they were presented to their LVF/RH; and an advantage for negative words presented to their LVF/RH compared to their RVF/LH. Additionally, they were more sensitive to perceiving the valence of a word that was presented to their LVF/RH. This suggests that their RH semantic systems may differ from that of SSRI Responders and Never Depressed controls. Genetic, hormonal and cognitive factors are discussed in relation to these patterns of hemispheric asymmetries and responsiveness to SSRI medication.</p>

Frontal Alpha Asymmetry: a potential biomarker of approach-withdrawal motivation towards pain.

Pain-related catastrophising is a maladaptive coping strategy known to have a strong influence on clinical pain outcomes and treatment efficacy. Mounting evidence suggests catastrophising is associated with resting-state EEG frontal alpha asymmetry (FAA) patterns reflective of greater relative right frontal activity, thought to underly withdrawal motivation and negative affect. Notwithstanding, knowledge on the neurophysiological basis of catastrophising remains limited. The present study aims to investigate whether such relationship occurs in the situational context of experimental pain, and how FAA is modulated by pain and placebo treatment. 35 participants completed the Pain Catastrophising Scale (PCS) questionnaire prior to EEG recordings during cold pressor test (CPT)-induced tonic pain with or without prior application of placebo cream. There was a negative correlation between FAA and PCS-subscale helplessness scores, but not rumination or magnification, during the pre-placebo CPT condition. Moreover, FAA scores were shown to increase significantly in response to pain, indicative of greater relative left frontal activity that relates to approach-oriented behaviours. Placebo treatment elicited a decrease in FAA in low helplessness scorers, but no significant effects in individuals scoring above the mean on PCS-helplessness. These findings suggest that, during painful events, FAA may reflect the motivational drive to obtain reward of pain relief, which may be diminished in individuals who are prone to feel helpless about their pain. This study provides valuable insights into biomarkers of pain-related catastrophising and prospects of identifying promising targets of brain-based therapies for chronic pain management.

Neural dynamics of illusory tactile pulling sensations

The sensation of directional forces and their associated sensorimotor commands are inextricably intertwined, complicating the identification of brain circuits responsible for tactile pulling sensations. One hypothesis is that, like tactile frequency discrimination, pulling sensations are generated by early sensory-frontal activity. Alternatively, they may be generated later in the somatosensory association cortex. To dissociate these accounts and uncouple the pulling sensation from unrelated but correlated sensory and motor processing, we combined high-density EEG with an oddball paradigm and asymmetric vibration, which creates an illusory sensation of the hand being directionally pulled. Oddballs that created a pulling sensation in the opposite direction to common stimuli were compared to the same oddballs in the context of neutral common stimuli (symmetric vibration) and to neutral oddballs. Brain responses to having directional pulling expectations violated by directional stimuli were therefore isolated. Contrary to the sensory-frontal account, frontal N140 brain activity was actually larger for neutral than pulling oddballs. Instead, pulling sensations were associated with amplitude and latency modulations of midline P200 and P3b potentials, and specifically, to contralateral parietal lobe activity 280ms post-stimulus. The timing of this activity suggested pulling sensations involve spatial processing, such as tactile remapping between coordinate frames. Source localization showed this activity to be centered on the postcentral sulcus, superior parietal lobule and intraparietal sulcus, suggesting that pulling sensations arise via the processing of body position, tactile orientation and peripersonal space. Our results demonstrate how tactile illusions can uniquely disambiguate parietal contributions to somatosensation by removing unrelated sensory processing.

Association between pain, anxiety, and alpha2 frontal activity in women with fibromyalgia

Fibromyalgia is a disorder of the central nervous system, with the presence of chronic generalized pain, fatigue, morning stiffness, anxiety and depression symptoms. Higher amplitudes of the frequency band alpha2 have been associated with higher relaxation in this population. In the present study, we analysed the association between pain, anxiety, and the spectral power of alpha2 frontal in women with fibromyalgia. Thirty-one women diagnosed with fibromyalgia, for at least three months, took part in the study. Results revealed a statistically significant positive relationship between pain and anxiety levels. However, we found no association between the spectral power of alpha2 in the frontal cortex and the measures between anxiety and pain in the patients. Present findings emphasize the importance of understanding the cortical activity and the central control mechanisms in fibromyalgia.

Real-time synthesis of imagined speech processes from minimally invasive recordings of neural activity

Speech neuroprosthetics aim to provide a natural communication channel to individuals who are unable to speak due to physical or neurological impairments. Real-time synthesis of acoustic speech directly from measured neural activity could enable natural conversations and notably improve quality of life, particularly for individuals who have severely limited means of communication. Recent advances in decoding approaches have led to high quality reconstructions of acoustic speech from invasively measured neural activity. However, most prior research utilizes data collected during open-loop experiments of articulated speech, which might not directly translate to imagined speech processes. Here, we present an approach that synthesizes audible speech in real-time for both imagined and whispered speech conditions. Using a participant implanted with stereotactic depth electrodes, we were able to reliably generate audible speech in real-time. The decoding models rely predominately on frontal activity suggesting that speech processes have similar representations when vocalized, whispered, or imagined. While reconstructed audio is not yet intelligible, our real-time synthesis approach represents an essential step towards investigating how patients will learn to operate a closed-loop speech neuroprosthesis based on imagined speech.

Emotional Modulation of Frontal Alpha Asymmetry - a Novel Biomarker of Mild Traumatic Brain Injury

Objective findings of brain injury or dysfunction are typically lacking in mild traumatic brain injury (MTBI) despite prolonged post-concussion symptoms in some patients. Thus, there is a need for objective biomarkers of MTBI that reflect altered brain physiology underlying subjective symptoms. We have previously reported increased attention to threat-related stimuli in subjects with MTBI, suggesting a physiological vulnerability to depression. Vulnerability to depression has been linked with relatively greater activity of the right than left frontal cortex reflected in inverse pattern in frontal alpha with greater power on the left than right. We investigated whether patients with previous MTBI show this pattern of frontal activity reflected in more negative frontal alpha asymmetry (FAA) scores. Furthermore, in search for potential biomarkers of MTBI, we created a novel index, emotional modulation of FAA (eFAA) and investigated whether it correlates with subjective symptoms. EEG was recorded while subjects with previous MTBI and controls performed a computer-based reaction time task integrating different cognitive executive functions and containing either threat-related or emotionally neutral visual stimuli. Post-concussion symptoms and depression were assessed using the Rivermead Post-Concussion Symptoms Questionnaire (RPQ) and Beck’s depression inventory (BDI). Task-induced FAA was assessed and eFAA calculated by subtracting FAA in the context of neutral stimuli from FAA in the context of emotional stimuli. The MTBI group showed FAA scores reflecting relatively greater right-sided frontal activity compared to healthy controls. eFAA differentiated the symptomatic MTBI from non-symptomatic MTBI group and from healthy controls. eFAA also correlated with RPQ and BDI scores. In conclusion, FAA pattern previously linked with vulnerability to depression, was observed in patients with previous MTBI. Furthermore, eFAA has potential as a biomarker of altered affective brain functions in MTBI.

Time distribution of thunderstorms observed at Odesa AMSC at the beginning of the 21st century

The article presents the results of the research of thunderstorm activity at Odesa AMSC for the period of 2000-2019. Under conditions of intense warming, thunderstorm activity responds to the changes of temperature, humidity, radiation regime and atmospheric composition. Modern climate changes that are characterized by rising air temperatures have a decisive influence on the conditions under which dangerous weather phenomena are formed, thus monitoring of the thunderstorms formation in Ukraine is of great importance. The research includes the analysis of synoptic conditions of thunderstorm activity formation such as air-mass processes, frontal activity, and studies daily and daytime variability of the number of thunderstorm cases for the given period. The results of everyday meteorological observations of atmospheric phenomena conducted by Odesa AMSC within the period of 2000-2019 were used as input data to determine the characteristics of thunderstorm activity over city of Odesa. In order to identify the presence, time and duration of thunderstorm activity aviation weather diaries AV-6 were also reviewed. Certain synoptic materials were used to analyze the types of phenomena. Such materials include interactive database ARMsyn, surface synoptic charts for the periods of observation before and during the thunderstorms. It was established that during the period under study air-mass thunderstorms were formed in 370 cases of thunderstorm activity observed at the given observation post. Frontal thunderstorms occur less often: 241 cases over 20 years. The largest number of such thunderstorms is cold front thunderstorms amounting to 129 cases. 75 of them were identified as occlusion front thunderstorms. The least frequent were warm front thunderstorms – only 37 cases constituting 15% of the total number of frontal formations. During the studied period a total number of 620 thunderstorm cases was recorded, 195 of which are dry thunderstorms. Considerable attention is paid to the daily and daytime variability of thunderstorm cases number recorded by Odesa AMSC. With relation to the daily variation, more thunderstorms are observed during daytime amounting to 393 cases, 130 of which are dry thunderstorms. Night thunderstorms amount to 227 cases, 65 of which are dry thunderstorms. With relation to daytime distribution, more thunderstorms were detected in the afternoon.