Coherent theta activity in the medial and orbital frontal cortices encodes reward value

This study examined how the medial frontal (MFC) and orbital frontal (OFC) cortices process reward information. We simultaneously recorded local field potentials in the two areas as rats consumed liquid sucrose rewards. Both areas exhibited a 4–8 Hz ‘theta’ rhythm that was phase-locked to the lick cycle. The rhythm tracked shifts in sucrose concentrations and fluid volumes, demonstrating that it is sensitive to differences in reward magnitude. The coupling between the rhythm and licking was stronger in MFC than OFC and varied with response vigor and absolute reward value in the MFC. Spectral analysis revealed zero-lag coherence between the cortical areas, and found evidence for a directionality of the rhythm, with MFC leading OFC. Our findings suggest that consummatory behavior generates simultaneous theta range activity in the MFC and OFC that encodes the value of consumed fluids, with the MFC having a top-down role in the control of consumption.

Theta-Range Oscillations in Stress-Induced Mental Disorders as an Oscillotherapeutic Target

Emotional behavior and psychological disorders are expressed through coordinated interactions across multiple brain regions. Brain electrophysiological signals are composed of diverse neuronal oscillations, representing cell-level to region-level neuronal activity patterns, and serve as a biomarker of mental disorders. Here, we review recent observations from rodents demonstrating how neuronal oscillations in the hippocampus, amygdala, and prefrontal cortex are engaged in emotional behavior and altered by psychiatric changes such as anxiety and depression. In particular, we focus mainly on theta-range (4–12 Hz) oscillations, including several distinct oscillations in this frequency range. We then discuss therapeutic possibilities related to controlling such mental disease-related neuronal oscillations to ameliorate psychiatric symptoms and disorders in rodents and humans.

Preferred auditory temporal processing regimes and auditory-motor synchronization

Decoding the rich temporal dynamics of complex sounds such as speech is constrained by the underlying neuronal-processing mechanisms. Oscillatory theories suggest the existence of one optimal perceptual performance regime at auditory stimulation rates in the delta to theta range (< 10 Hz), but reduced performance in the alpha range (10–14 Hz) is controversial. Additionally, the widely discussed motor system contribution to timing remains unclear. We measured rate discrimination thresholds between 4 and 15 Hz, and auditory-motor coupling strength was estimated through a behavioral auditory-motor synchronization task. In a Bayesian model comparison, high auditory-motor synchronizers showed a larger range of constant optimal temporal judgments than low synchronizers, with performance decreasing in the alpha range. This evidence for optimal processing in the theta range is consistent with preferred oscillatory regimes in auditory cortex that compartmentalize stimulus encoding and processing. The findings suggest, remarkably, that increased auditory-motor synchronization might extend such an optimal range towards faster rates.

Hemispheric differences in altered reactivity of brain oscillations at rest after posterior lesions

A variety of evidence supports the dominance of the right hemisphere in perceptual and visuo-spatial processing. Although growing evidence shows a strong link between alpha oscillations and the functionality of the visual system, asymmetries in alpha oscillatory patterns still need to be investigated. Converging findings indicate that the typical alpha desynchronization occurring in the transition from the eyes-closed to the eyes-open resting state might represent an index of reactivity of the visual system. Thus, investigating hemispheric asymmetries in EEG reactivity at the opening of the eyes in brain-lesioned patients may shed light on the contribution of specific cortical sites and each hemisphere in regulating the oscillatory patterns reflecting the functionality of the visual system. To this aim, EEG signal was recorded during eyes-closed and eyes-open resting state in hemianopic patients with posterior left or right lesions, patients without hemianopia with anterior lesions and healthy controls. Hemianopics with both left and right posterior lesions showed a reduced alpha reactivity at the opening of the eyes, suggesting that posterior cortices have a pivotal role in the functionality of alpha oscillations. However, right-lesioned hemianopics showed a greater dysfunction, demonstrated by a reactivity reduction more distributed over the scalp, compared to left-lesioned hemianopics. Moreover, they also revealed impaired reactivity in the theta range. This favors the hypothesis of a specialized role of the right hemisphere in orchestrating oscillatory patterns, both coordinating widespread alpha oscillatory activity and organizing focal processing in the theta range, to support visual processing at the opening of the eyes.

Hold your horses: Differences in EEG correlates of inhibition in cancelling and stopping an action

Behavioral adaptation to changing contextual contingencies often requires the rapid inhibition of planned or ongoing actions. Inhibitory control has been mostly studied using the stop–signal paradigm, which conceptualizes action inhibition as the outcome of a race between independent GO and STOP processes. Inhibition is predominantly considered to be independent of action type, yet it is questionable whether this conceptualization can apply to stopping an ongoing action. To test the claimed generality of action inhibition, we investigated behavioral stop–signal reaction time (SSRT) and scalp electroencephalographic (EEG) activity in two inhibition contexts: Using variants of the stop–signal task, we asked participants to cancel a prepared–discrete action or to stop an ongoing–rhythmic action in reaction to a STOP signal. The behavioral analysis revealed that the discrete and rhythmic SSRTs were not correlated. The EEG analysis showed that the STOP signal evoked frontocentral activity in the time and frequency domains (Delta/Theta range) in a task–specific manner: The N2 and P3 STOP–signal event–related potentials correlated distinctively to rhythmic and discrete SSRT, respectively. These findings do not support a conceptualization of inhibition as action–independent but rather suggest that the differential engagement of both components of the N2/P3–complex as a function of the action type pertains to functionally independent inhibition subprocesses.

Rhythmic Accessibility to Sequential Working Memory in a Theta Phase-Dependent Manner

Working memory is active short-term memory storage that is easily accessible and underlies various activities, such as maintaining phone numbers in mind for a short period [1,2]. There is accumulating theoretical and physiological evidence that memorized items are represented rhythmically by neural oscillation in the theta range (4-7 Hz) [3,4]. However, the impact of this process on human behavior is yet to be examined. Here we show that simply memorizing sequential information affects a behavioral index (i.e., reaction time, RT) in a rhythmic manner. In the main experiment (Experiment 1), we measured RTs to a visual probe that appeared at one of two sequentially memorized locations after a random interval. Consequently, RTs to the first and second probes each fluctuated in the theta range as a function of the random interval, and the phases of the two theta fluctuations were not in phase or anti-phase, but shifted by approximately 270 degree. Interestingly, the 270 degree phase difference corresponded to the rhythm of "phase coding", where sequential information is represented on the specific phase of theta oscillation [5-7]. These relationships were not observed in tasks simply requiring attention (Experiment 2) or memorization (Experiment 3) of spatial locations without sequential order. In conclusion, the current results demonstrate that our behavior fluctuates when recalling memorized sequential items in the theta-range, suggesting that accessibility to sequential working memory is rhythmic rather than stable, possibly reflecting theta-phase coding.

Применение анализа совместных рекуррентностей к оценке фазовой синхронизации физиологических сигналов

Based on the analysis of joint recurrences, differences in phase synchronization between rhythmic photostimulation and brain responses were revealed in individuals with atrial fibrillation of paroxysmal and persistent types. As a measure of phase synchronization between two signals, the cross-correlation coefficient between the probabilities of recurrences of the corresponding phase trajectories is considered. With a lengthening of the lifetime of atrial fibrillation and an increase in the degree of decline in cognitive functions, the value of this coefficient increases for brain responses to theta-range frequencies.

Preferred auditory temporal processing regimes and auditory-motor interactions

Decoding the rich temporal dynamics of complex sounds such as speech is constrained by the underlying neuronal processing mechanisms. Oscillatory theories suggest the existence of one optimal perceptual performance regime at auditory stimulation rates in the delta to theta range (<10 Hz), but reduced performance in the alpha range (10-14 Hz) is controversial. Additionally, the widely discussed motor system contribution to timing remains unclear. We measured rate discrimination thresholds between 4-15 Hz, and auditory-motor coupling strength was estimated through auditory-motor synchronization. In a Bayesian model comparison, high auditory-motor synchronizers showed a larger range of constant optimal temporal judgments than low synchronizers, with performance decreasing in the alpha range. This evidence for optimal auditory processing in the theta range is consistent with preferred oscillatory regimes in auditory cortex that compartmentalize stimulus encoding and processing. The findings suggest, remarkably, that increased auditory-motor interaction might extend such an optimal range towards faster rates.

Temporal binding of Visual and Motor cortical oscillations revealed by BOLD response in Humans

SummaryAction and perception need to be coordinated continuously over time, and neural oscillations may be instrumental in achieving such synchronization. Here we demonstrate that behavioral visual discrimination and the BOLD activity of V1 oscillates rhythmically in the theta range (around 5 Hz), synchronized to motor action (button press). The oscillations are present in V1 even when participants do not make a visual discrimination, suggesting an automatic modulation in synchrony with action onset. The amplitude of the oscillation in V1 is predicted by the activity in M1 before action onset, and functional connectivity between V1 and M1 change as a function of stimulus-delay. The results are well modelled by considering that V1 BOLD is modulated by preparatory motor signal and by rhythmic gain modulation in phase with action onset. They suggest that synchronous oscillatory activity between V1 and M1 mediates the strong temporal binding fundamental for active visual perception.