Reward-Based Decision-Making Engages Distinct Modes of Cross-Frequency Coupling

ROSE: A Neurocomputational Architecture for Syntax

A comprehensive model of natural language processing in the brain must accommodate four components: representations, operations, structures and encoding. It further requires a principled account of how these different components mechanistically, and causally, relate to each another. While previous models have isolated regions of interest for structure-building and lexical access, and have utilized specific neural recording measures to expose possible signatures of syntax, many gaps remain with respect to bridging distinct scales of analysis that map onto these four components. By expanding existing accounts of how neural oscillations can index various linguistic processes, this article proposes a neurocomputational architecture for syntax, termed the ROSE model (Representation, Operation, Structure, Encoding). Under ROSE, the basic data structures of syntax are atomic features, types of mental representations (R), and are coded at the single-unit and ensemble level. Elementary computations (O) that transform these units into manipulable objects accessible to subsequent structure-building levels are coded via high frequency broadband γ activity. Low frequency synchronization and cross-frequency coupling code for recursive categorial inferences (S). Distinct forms of low frequency coupling and phase-amplitude coupling (δ-θ coupling via pSTS-IFG; θ-γ coupling via IFG to conceptual hubs in lateral and ventral temporal cortex) then encode these structures onto distinct workspaces (E). Causally connecting R to O is spike-phase/LFP coupling; connecting O to S is phase-amplitude coupling; connecting S to E is a system of frontotemporal traveling oscillations; connecting E back to lower levels is low-frequency phase resetting of spike-LFP coupling. This compositional neural code has important implications for algorithmic accounts, since it makes concrete predictions for the appropriate level of study for psycholinguistic parsing models. ROSE is reliant on neurophysiologically plausible mechanisms, is supported at all four levels by a range of recent empirical research, and provides an anatomically precise and falsifiable grounding for the basic property of natural language syntax: hierarchical, recursive structure-building.

[Features of the reward-based decision-making in patients with alcohol use disorders]

Foreign studies increasingly emphasize the role of reward-based cognitive decision-making and its contribution to alcohol and drug abuse. Unfortunately, such studies are extremely few in Russia. Given the importance of the insufficiency of cognitive functions, primarily the decision-making process based on reward, among the risk factors of addictive pathology, increasing the severity of alcoholism, reducing the effectiveness of its therapy and rehabilitation, research in this direction is extremely relevant. This review summarizes and systematizes current data on the features of the cognitive decision-making process based on reward in patients with alcohol dependence. An analysis of the literature has shown that reward-based decision making is an important component of addictive behavior. Patients with alcohol dependence, as well as people, who abuse alcohol, demonstrate clear impairment of this cognitive function. Thus, the relative value of diagnosing disorders in decision-making in modern psychiatry is beyond doubt. It is recommended to include the above tests in the diagnostic complex of a psychiatrist, along with standard psychometric tools.

[Features of decision-making in patients with alcohol dependence]

OBJECTIVE

To identify electroencephalographic correlates of decision-making features in patients with alcohol dependence.

MATERIAL AND METHODS

Forty men with alcohol dependence were examined as the main group. Thirty people were examined as a control group. The Cambridge Gambling Task and the Iowa Gambling Task were used to study decision-making functions. Additionally, a background electroencephalogram was recorded with the calculation of absolute spectral power indicators.

RESULTS

In the main group, the relatively higher indicators of decision-making logic (65 [50; 80]%, p<0.05) were associated with larger values of the spectral power of the theta and alpha rhythm of the electroencephalogram in the central and parietal-occipital leads (R=0.426, p=0.019; R=0.418, p=0.022; R=0.394, p=0.028 and R=0.445, p=0.014; R=0.458, p=0.011; R=0.382, p=0.035, respectively). Difficulties in making decisions based on emotional learning in patients with alcohol dependence were associated with larger values of the spectral power of the beta rhythm of the electroencephalogram in the temporal leads.

CONCLUSIONS

The study showed that the deficit of decision-making functions in patients with alcohol dependence may be due to an imbalance of the excitation/inhibition mechanisms in the brain.

Comparison of event-related modulation index and traditional methods for evaluating phase-amplitude coupling using simulated brain signals

The investigation of brain oscillations and connectivity has become an important topic in the recent decade. There are several types of interactions between neuronal oscillations, and one of the most interesting among these interactions is phase-amplitude coupling (PAC). Several methods have been proposed to measure the strength of PAC, including the phase-locking value, circular-linear correlation, and modulation index. In the current study, we compared these traditional PAC methods with simulated electroencephalogram signals. Further, to assess the PAC value at each time point, we also compared two recently established methods, event-related phase-locking value and event-related circular-linear correlation, with our newly proposed event-related modulation index (ERMI). Results indicated that the ERMI has better temporal resolution and is more tolerant to noise than the other two event-related methods, suggesting the advantages of utilizing ERMI in evaluating the strength of PAC within a brain region.

Amplitude modulating frequency overrides carrier frequency in tACS-induced phosphene percept

The amplitude modulated (AM) neural oscillation is an essential feature of neural dynamics to coordinate distant brain areas. The AM transcranial alternating current stimulation (tACS) has recently been adopted to examine various cognitive functions, but its neural mechanism remains unclear. The current study utilized the phosphene phenomenon to investigate whether, in an AM-tACS, the AM frequency could modulate or even override the carrier frequency in phosphene percept. We measured the phosphene threshold and the perceived flash rate/pattern from 12 human subjects (four females, aged from 20-44 years old) under tACS that paired carrier waves (10, 14, 18, 22 Hz) with different envelope conditions (0, 2, 4 Hz) over the mid-occipital and left facial areas. We also examined the phosphene source by adopting a high-density stimulation montage. Our results revealed that (1) phosphene threshold was higher for AM-tACS than sinusoidal tACS and demonstrated different carrier frequency functions in two stimulation montages. (2) AM-tACS slowed down the phosphene flashing and abolished the relation between the carrier frequency and flash percept in sinusoidal tACS. This effect was independent of the intensity change of the stimulation. (3) Left facial stimulation elicited phosphene in the upper-left visual field, while occipital stimulation elicited equally distributed phosphene. (4) The near-eye electrodermal activity (EDA) measured under the threshold-level occipital tACS was greater than the lowest power sufficient to elicit retinal phosphene. Our results show that AM frequency may override the carrier frequency and determine the perceived flashing frequency of AM-tACS-induced phosphene.