Functional Dissociation of θ Oscillations in the Frontal and Visual Cortices and Their Long-Range Network during Sustained Attention

Visual experience induces 4-8 Hz synchrony between V1 and higher-order visual areas

Visual perceptual experience induces persistent 4-8 Hz oscillations in the mouse primary visual cortex (V1), encoding visual familiarity. Recent studies suggest that higher-order visual areas (HVAs) are functionally specialized and segregated into information streams processing distinct visual features. However, whether visual memories are processed and stored within the distinct streams is not understood. We report here that V1 and lateromedial (LM), but not V1 and anterolateral, become more phase synchronized in 4-8 Hz after the entrainment of visual stimulus that maximally induces responses in LM. Directed information analysis reveals changes in the top-down functional connectivity between V1 and HVAs. Optogenetic inactivation of LM reduces post-stimulus oscillation peaks in V1 and impairs visual discrimination behavior. Our results demonstrate that 4-8 Hz familiarity-evoked oscillations are specific for the distinct visual features and are present in the corresponding HVAs, where they may be used for the inter-areal communication with V1 during memory-related behaviors.

Perceptual Integration Compensates for Attention Deficit in Elderly during Repetitive Auditory-Based Sensorimotor Task

Sensorimotor integration (SI) brain functions that are vital for everyday life tend to decline in advanced age. At the same time, elderly people preserve a moderate level of neuroplasticity, which allows the brain's functionality to be maintained and slows down the process of neuronal degradation. Hence, it is important to understand which aspects of SI are modifiable in healthy old age. The current study focuses on an auditory-based SI task and explores: (i) if the repetition of such a task can modify neural activity associated with SI, and (ii) if this effect is different in young and healthy old age. A group of healthy older subjects and young controls underwent an assessment of the whole-brain electroencephalography (EEG) while repetitively executing a motor task cued by the auditory signal. Using EEG spectral power and functional connectivity analyses, we observed a differential age-related modulation of theta activity throughout the repetition of the SI task. Growth of the anterior stimulus-related theta oscillations accompanied by enhanced right-lateralized frontotemporal phase-locking was found in elderly adults. Their young counterparts demonstrated a progressive increase in prestimulus occipital theta power. Our results suggest that the short-term repetition of the auditory-based SI task modulates sensory processing in the elderly. Older participants most likely progressively improve perceptual integration rather than attention-driven processing compared to their younger counterparts.

A review of visual sustained attention: neural mechanisms and computational models

Sustained attention is one of the basic abilities of humans to maintain concentration on relevant information while ignoring irrelevant information over extended periods. The purpose of the review is to provide insight into how to integrate neural mechanisms of sustained attention with computational models to facilitate research and application. Although many studies have assessed attention, the evaluation of humans' sustained attention is not sufficiently comprehensive. Hence, this study provides a current review on both neural mechanisms and computational models of visual sustained attention. We first review models, measurements, and neural mechanisms of sustained attention and propose plausible neural pathways for visual sustained attention. Next, we analyze and compare the different computational models of sustained attention that the previous reviews have not systematically summarized. We then provide computational models for automatically detecting vigilance states and evaluation of sustained attention. Finally, we outline possible future trends in the research field of sustained attention.

TMS Bursts Can Modulate Local and Networks Oscillations During Lower-Limb Movement

PURPOSE

Lower-limb motor functions involve processing information via both motor and cognitive control networks. Measuring oscillations is a key element in communication within and between cortical networks during high-order motor functions. Increased midfrontal theta oscillations are related to improved lower-limb motor performances in patients with movement disorders. Noninvasive neuromodulation approaches have not been explored extensively to understand the oscillatory mechanism of lower-limb motor functions. This study aims to examine the effects of repetitive transcranial magnetic stimulation on local and network EEG oscillations in healthy elderly subjects.

METHODS

Eleven healthy elderly subjects (67-73 years) were recruited via advertisements, and they underwent both active and sham stimulation procedures in a random, counterbalanced design. Transcranial magnetic stimulation bursts (θ-transcranial magnetic stimulation; 4 pulses/second) were applied over the midfrontal lead (vertex) before a GO-Cue pedaling task, and signals were analyzed using time-frequency methods.

RESULTS

Transcranial magnetic stimulation bursts increase the theta activity in the local ( p = 0.02) and the associated network during the lower-limb pedaling task ( p = 0.02). Furthermore, after task-related transcranial magnetic stimulation burst sessions, increased resting-state alpha activity was observed in the midfrontal region ( p = 0.01).

CONCLUSIONS

This study suggests the ability of midfrontal transcranial magnetic stimulation bursts to directly modulate local and network oscillations in a frequency manner during lower-limb motor task. Transcranial magnetic stimulation burst-induced modulation may provide insights into the functional roles of oscillatory activity during lower-limb movement in normal and disease conditions.

LPS-induced acute neuroinflammation, involving interleukin-1 beta signaling, leads to proteomic, cellular, and network-level changes in the prefrontal cortex of mice

Neuroinflammation induced by peripheral infections leads to various neuropsychiatric symptoms both in humans and laboratory animals, e.g., to the manifestation of sickness behavior that resembles some features of clinical depression. However, in addition to depression-like behavior, there are other symptoms of acute systemic inflammation that can be associated with the impairment of prefrontal cortex (PFC)-regulated cognitive functions. Thus, we investigated the electrophysiological and proteomic alterations of the PFC using brain slices and the lipopolysaccharide (LPS) model of acute peripheral infection in male mice. Based on the gene expression differences of the coreceptor (Il1rap) of interleukin-1 beta (IL-1β) between neuron types in our previous single-cell sequencing dataset, we first compared the electrophysiological effects of IL-1β on PFC pyramidal cells and interneurons. We found that pyramidal cells are more responsive to IL-1β, as could be presumed from our transcriptomic data. To examine the possible circuit-level correlates of the cellular changes, frontal electroencephalographic (EEG) activity and fronto-occipital functional connectivity were analyzed in LPS-treated mice and significant changes were found in the fronto-occipital EEG correlation and coherence in the delta and high-gamma frequency bands. The upregulation of the prefrontal IL-1 system (IL-1β and its receptor) after LPS treatment was revealed by immunoassays simultaneously with the observed EEG changes. Furthermore, we investigated the LPS-induced alterations of the synaptic proteome in the PFC using 2-D differential gel electrophoresis and mass spectrometry and found 48 altered proteins mainly related to cellular signaling, cytoskeletal organization, and carbohydrate/energy metabolism. Thus, our results indicate remarkable electrophysiological and molecular changes in the PFC related to acute systemic inflammation that may explain some of the concomitant behavioral and physiological symptoms.

Modulation of Neuronal Activity and Saccades at Theta Rhythm During Visual Search in Non-human Primates

Active exploratory behaviors have often been associated with theta oscillations in rodents, while theta oscillations during active exploration in non-human primates are still not well understood. We recorded neural activities in the frontal eye field (FEF) and V4 simultaneously when monkeys performed a free-gaze visual search task. Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials, and the phase-locking was dependent on saccade direction. The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response. V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases. Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing. Together, our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas, in addition to the theta phase locking caused by saccade-triggered responses.

Oscillatory dynamics underlying noun and verb production in highly proficient bilinguals

Words representing objects (nouns) and words representing actions (verbs) are essential components of speech across languages. While there is evidence regarding the organizational principles governing neural representation of nouns and verbs in monolingual speakers, little is known about how this knowledge is represented in the bilingual brain. To address this gap, we recorded neuromagnetic signals while highly proficient Spanish-Basque bilinguals performed a picture-naming task and tracked the brain oscillatory dynamics underlying this process. We found theta (4-8 Hz) power increases and alpha-beta (8-25 Hz) power decreases irrespectively of the category and language at use in a time window classically associated to the controlled retrieval of lexico-semantic information. When comparing nouns and verbs within each language, we found theta power increases for verbs as compared to nouns in bilateral visual cortices and cognitive control areas including the left SMA and right middle temporal gyrus. In addition, stronger alpha-beta power decreases were observed for nouns as compared to verbs in visual cortices and semantic-related regions such as the left anterior temporal lobe and right premotor cortex. No differences were observed between categories across languages. Overall, our results suggest that noun and verb processing recruit partially different networks during speech production but that these category-based representations are similarly processed in the bilingual brain.

The landscape of cognitive function in recovered COVID-19 patients

This study aims to evaluate the impacts of COVID-19 on cognitive functions in recovered patients and its relationship with inflammatory profiles. Twenty-nine patients recovered from COVID-19 as confirmed by negative nucleic tests for two consecutive times were recruited. A total of 29 age-, gender- and education-matched healthy controls were also recruited. The cognitive functions of all subjects were evaluated by the iPad-based online neuropsychological tests, including the Trail Making Test (TMT), Sign Coding Test (SCT), Continuous Performance Test (CPT), and Digital Span Test (DST). Blood samples from all patients were collected for examining inflammatory profiles, including interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and C-reactive protein (CRP). The relationship between cognitive functions and inflammatory profiles were analyzed by Pearson correlation. In results, although no significant differences were found in TMT, SCT, and DST between the two groups, patients with COVID-19 scored lower in the correct number of the second and third parts of CPT, they also scored higher in the missing number of the third part of CPT (all P < 0.05). In patients with COVID-19, there was a trend of significant difference for lower reaction time in the first and second parts of CPT (P = 0.050, and 0.051, respectively), as well as the lower correct number of the second part of CPT (P = 0.050). Correlation analysis showed that the reaction time for the first and second parts of CPT was positively correlated with the CRP levels (r = 0.557 and 0.410, P < 0.05). In conclusion, our findings indicated that cognitive impairments exist even in patients recovered from COVID-19, and might be possibly linked to the underlying inflammatory processes.

Alpha frequency rTMS modulates theta lagged nonlinear connectivity in dorsal attention network

Dorsolateral prefrontal cortex (DLPFC) is a key structure in dorsal attention network (DAN) that facilitates sustained attention by modulating activity in task related and unrelated regions of the brain. Alpha and theta frequency bands enhance connectivity among different parts of the attention network and these connections are facilitated by long-range nonlinear connectivity in theta and alpha frequency bands. This study is an investigation of the behavioral and electrophysiological effects of alpha and theta frequency repetitive transcranial magnetic stimulation (rTMS) over RDLPFC. 20 healthy participants were randomly assigned to two groups of theta (n = 11, f = 6 Hz) and alpha (n = 9, f = 10 Hz) rTMS. Electroencephalogram (EEG) was recorded before and after each session while resting and performing tasks. Current source density (CSD) and functional connectivity (FC) in DAN and default mode network (DMN) and their correlations with rapid visual information processing task (RVIP) scores were calculated . Alpha frequency rTMS resulted in significant changes in RVIP scores. Active theta rTMS caused an increase in CSD in Postcentral gyrus and active alpha rTMS resulted in significant CSD changes in inferior parietal lobule (IPL). Theta lagged nonlinear connectivity was mudulated by alpha rTMSand FC changes were observed in DAN and DMN. Positive correlations were observed between DAN regions and RVIP scores in the alpha rTMS group. Increased activity in theta frequency band in left aPFC and left DLPFC correlated positively with higher total hits in RVIP. This study showed for the first time that theta and alpha frequency rTMS are able to modulate FC in DAN and DMN in a way that results in better performance in a sustained attention task.

Spontaneous Feedforward Connectivity in Electrically Stimulated Retinal Degeneration Mice. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020;2020:3513-3516. [PMID: 33018761 DOI: 10.1109/embc44109.2020.9175231]

Retinal degeneration (Rd) is a neurodegenerative disorder primarily associated with the degeneration of the retina neurons and culminates in the eventual loss of visual perception or blindness. Decrease in fronto-, parietal and occipital brain connectivity have been reported in a number of neurodegeneration diseases involving cognitive decline. However, cortical communication in the brain of retinal degeneration patients remains largely unknown and strategies to remediate observed dysfunctional brain connectivity in such instance have not be thoroughly investigated. We used rd10 mice as a model to study brain connectivity in the human retinal degeneration disease, retinitis pigmentosa. Rd10 mice with sham matched controls were electrically stimulated at varying stimulation frequencies and the consequent perturbations in feedforward brain connectivity were studied in the visual cortex and pre-frontal cortex using electrocorticography (ECoG) and normalized symbolic transfer entropy (NSTE). Contra Vcx - contra PFx feed forward connectivity significantly (p<0.05) increased in theta, alpha and beta oscillatory bands of 2 Hz and 10 Hz stimulated rd10 respectively in comparison with sham group. Also, this increase was significantly maintained even after the end of the stimulation period.

The (Un)Conscious Mouse as a Model for Human Brain Functions: Key Principles of Anesthesia and Their Impact on Translational Neuroimaging

In recent years, technical and procedural advances have brought functional magnetic resonance imaging (fMRI) to the field of murine neuroscience. Due to its unique capacity to measure functional activity non-invasively, across the entire brain, fMRI allows for the direct comparison of large-scale murine and human brain functions. This opens an avenue for bidirectional translational strategies to address fundamental questions ranging from neurological disorders to the nature of consciousness. The key challenges of murine fMRI are: (1) to generate and maintain functional brain states that approximate those of calm and relaxed human volunteers, while (2) preserving neurovascular coupling and physiological baseline conditions. Low-dose anesthetic protocols are commonly applied in murine functional brain studies to prevent stress and facilitate a calm and relaxed condition among animals. Yet, current mono-anesthesia has been shown to impair neural transmission and hemodynamic integrity. By linking the current state of murine electrophysiology, Ca2+ imaging and fMRI of anesthetic effects to findings from human studies, this systematic review proposes general principles to design, apply and monitor anesthetic protocols in a more sophisticated way. The further development of balanced multimodal anesthesia, combining two or more drugs with complementary modes of action helps to shape and maintain specific brain states and relevant aspects of murine physiology. Functional connectivity and its dynamic repertoire as assessed by fMRI can be used to make inferences about cortical states and provide additional information about whole-brain functional dynamics. Based on this, a simple and comprehensive functional neurosignature pattern can be determined for use in defining brain states and anesthetic depth in rest and in response to stimuli. Such a signature can be evaluated and shared between labs to indicate the brain state of a mouse during experiments, an important step toward translating findings across species.