From Fast Oscillations to Circadian Rhythms: Coupling at Multiscale Frequency Bands in the Rodent Subcortical Visual System

The subcortical visual system (SVS) is a unique collection of brain structures localised in the thalamus, hypothalamus and midbrain. The SVS receives ambient light inputs from retinal ganglion cells and integrates this signal with internal homeostatic demands to influence physiology. During this processing, a multitude of oscillatory frequency bands coalesces, with some originating from the retinas, while others are intrinsically generated in the SVS. Collectively, these rhythms are further modulated by the day and night cycle. The multiplexing of these diverse frequency bands (from circadian to infra-slow and gamma oscillations) makes the SVS an interesting system to study coupling at multiscale frequencies. We review the functional organisation of the SVS, and the various frequencies generated and processed by its neurons. We propose a perspective on how these different frequency bands couple with one another to synchronise the activity of the SVS to control physiology and behaviour.

Multimodal Gradient Mapping of Rodent Hippocampus

The hippocampus plays a central role in supporting our coherent and enduring sense of self and our place in the world. Understanding its functional organisation is central to understanding this complex role. Previous studies suggest function varies along a long hippocampal axis, but there is disagreement about the presence of sharp discontinuities or gradual change along that axis. Other open questions relate to the underlying drivers of this variation and the conservation of organisational principles across species. Here, we delineate the primary organisational principles underlying patterns of hippocampal functional connectivity (FC) in the mouse using gradient analysis on resting state fMRI data. We further applied gradient analysis to mouse gene co-expression data to examine the relationship between variation in genomic anatomy and functional organisation. Two principal FC gradients along a hippocampal axis were revealed. The principal gradient exhibited a sharp discontinuity that divided the hippocampus into dorsal and ventral compartments. The second, more continuous, gradient followed the long axis of the ventral compartment. Dorsal regions were more strongly connected to areas involved in spatial navigation while ventral regions were more strongly connected to areas involved in emotion, recapitulating patterns seen in humans. In contrast, gene co-expression gradients showed a more segregated and discrete organisation. Our findings suggest that hippocampal functional organisation exhibits both sharp and gradual transitions and that hippocampal genomic anatomy exerts a subtle influence on this organisation.

Functional Organisation of the Mouse Superior Colliculus

The superior colliculus (SC) is a highly conserved area of the mammalian midbrain that is widely implicated in the organisation and control of behaviour. SC receives input from a large number of brain areas, and provides outputs to a large number of areas. The convergence and divergence of anatomical connections with different areas and systems provides challenges for understanding how SC contributes to behaviours. Recent work in mouse has provided large anatomical datasets, and a wealth of new data from experiments that identify and manipulate different cells within SC, and its inputs and outputs. These data offer an opportunity to better understand the functional roles of SC. However, some of the observations appear, at first sight, to be contradictory. Here we review this recent work and suggest a simple framework which can capture the observations, and that requires only a small change to previous models. Specifically, the functional organisation of SC can be explained by supposing that three largely distinct circuits support three largely distinct classes of behaviour - arrest, turning towards, and the triggering of escape or pursuit. These behavioural classes are supported by the optic, intermediate and deep layers respectively.

І. Stravinsky’s orchestral writing of Neo-Classical and serial (late) periods: comparative analysis

Statement of the problem. Neo-Classical and serial (late) periods of I. Stravinsky’s creativity are marked by the shifts in his musical language, which found their reflection in his orchestral writing. “Universals” of style and genre (term of Savenko (2001: 105–163) retain their relevancy. Constant principles of orchestral writing (multi-figure composition, combinatorics and plastique) are used in different combinations. Analysis of recent research and publications. While there are numerous studies devoted to I. Stravinsky’s Neo-Classical and serial (late) periods, no works have composer’s orchestral thinking and orchestral writing as an object of special examination. Thus, scarce studies regarding aspects of composer’s orchestration become even more valuable: about orchestral texture (Schnittke, 1967; Schnittke, 1973, Savenko, 2001; Kashyrtsev, 2020), or interpretation of timbres (Savenko, 2001; Savenko, 2011, Kashyrtsev, 2020), or interconnection of orchestral and harmonically-modal thinking (Gurkov, 1987), or editions (Timofeev, 2014; Timofeev, 2019). The purpose of this article is an examination of specifics of I. Stravinsky’s orchestral writing from the standpoint of peculiarity of application of constant principles of orchestral writing (multi-figure composition, combinatorics and plastique) in the ballet “Jeu de cartes” and the Variations (Aldous Huxley in Memoriam). The novelty of the article is caused by: 1)reveal of beforementioned principles; 2) examination of their existence in evolutionary perspective; 3) bringing attention to relevant problems of orchestration in I. Stravinsky’s works of Neo-Classical and late periods of creativity; 4) formulation of original scholarly definition of the term “orchestral writing”. Methods. In this article stylistic method is used – to study evolutionary processes of composer’s style in dialectic unity of constant and innovative; functional – to examine specifics of functional organisation of orchestral texture; comparative – to reveal different ways in which constant principles of orchestral writing are used on different stages of composer’s evolution. Results and Conclusions. Constant principles of orchestral writing (multifigure composition, combinatorics and plastique), which have already emerged in the primary period, are present in the works of Neo-Classical and late periods in different configurations of their relations. In the ballet “Jeu de cartes” multi-figure composition loses its role in comparison to the early works and is applied hidden due to: 1) motive variants (with the motives being stressed by timbre, texture or register); 2) textural complementarity (which means that multiple figures are used in timbrally-textural algorithm); 3) creation of “protracted” melody, in which the role of motivic “formula” is reduced (which is typical for I. Stravinsky’s Neo-Classical period). At the same time, continuity emerging in Neo-Classical works meets the tendency towards discretion due to influence of such principles as combinatorics and plastique, which retain their relevancy, being realised in different variants in the conditions of functional “clarity” of a texture, as it is a trait of composer’s Neo-Classical musical idiom. The orchestral writing of the Variations (Aldous Huxley in Memoriam) is defined by the principle of combinatorics with the usage of plastique. Serial technique contributed to its reveal. At the same time, the role of multi-figure composition is reduced to a bare minimum, which was caused by rejection of melodic “formularity”.

White matter variability, cognition, and disorders: a systematic review.

Inter-individual differences can inform treatment procedures and - if accounted for - have the potential to significantly improve patient outcomes. However, when studying brain anatomy, these inter-individual variations are commonly unaccounted for, despite reports of differences in gross anatomical features, cross-sectional and connectional anatomy. Brain connections are essential to facilitate functional organisation and, when severed, cause impairments or complete loss of function. Hence the study of cerebral white matter may be an ideal compromise to capture inter-individual variability in structure and function. We reviewed the wealth of studies that associate functions and clinical symptoms with individual tracts using diffusion tractography. Our systematic review indicates that tractography has proven to be a sensitive method in neurology, psychiatry and healthy populations to identify variability and its functional correlates. However, the literature may be biased, as we determined that the most commonly studied tracts are not necessarily those with the highest sensitivity to cognitive functions and pathologies. Additionally, the side of the studied tract is often unreported, thus neglecting functional laterality and hemispheric asymmetries. Finally, we demonstrate that tracts, as we define them, are not usually correlated with only one, but rather multiple cognitive domains or pathologies. While our systematic review identified some methodological caveats, it also suggests that tract-function correlations might be a promising biomarker for precision medicine. It characterises variations in brain anatomy, differences in functional organisation, and predicting resilience or recovery in patients.

Direct and indirect effects of cathodal cerebellar TDCS on visuomotor adaptation of hand and arm movements

Adaptation of movements involving the proximal and distal upper-limb can be differentially facilitated by anodal transcranial direct current stimulation (TDCS) over the cerebellum and primary motor cortex (M1). Here, we build on this evidence by demonstrating that cathodal TDCS impairs motor adaptation with a differentiation of the proximal and distal upper-limbs, relative to the site of stimulation. Healthy young adults received M1 or cerebellar cathodal TDCS while making fast ‘shooting’ movements towards targets under 60° rotated visual feedback conditions, using either whole-arm reaching or fine hand and finger movements. As predicted, we found that cathodal cerebellar TDCS resulted in impairment of adaptation of movements with the whole arm compared to M1 and sham groups, which proved significantly different during late adaptation. However, cathodal cerebellar TDCS also significantly enhanced adaptation of hand movements, which may reflect changes in the excitability of the pathway between the cerebellum and M1. We found no evidence for change of adaptation rates using arm or finger movements following cathodal TDCS directly over M1. These results are further evidence to support movement specific effects of TDCS, and highlight how the connectivity and functional organisation of the cerebellum and M1 must be considered when designing TDCS-based therapies.

Multiple dimensions underlying the functional organisation of the language network

ABSTRACTUnderstanding the different neural networks that support human language is an ongoing challenge for cognitive neuroscience. Which divisions are capable of distinguishing the functional significance of regions across the language network? A key separation between semantic cognition and phonological processing was highlighted in early meta-analyses, yet these seminal works did not formally test this proposition. Moreover, organisation by domain is not the only possibility. Regions may be organised by the type of process performed, as in the separation between representation and control processes proposed within the Controlled Semantic Cognition framework. The importance of these factors was assessed in a series of activation likelihood estimation meta-analyses that investigated which regions of the language network are consistently recruited for semantic and phonological domains, and for representation and control processes. Whilst semantic and phonological processing consistently recruit many overlapping regions, they can be dissociated (by differential involvement of bilateral anterior temporal lobes and superior temporal gyri) only when using both formal analysis methods and sufficient data. Both semantic and phonological regions are further dissociable into control and representation regions, highlighting this as an additional, distinct dimension on which the language network is functionally organised. Furthermore, some of these control regions overlap with multiple-demand network regions critical for control beyond the language domain, suggesting the relative level of domain-specificity is also informative. Multiple, distinct dimensions are critical to understand the role of language regions. Here we present a proposal as to the core principles underpinning the functional organisation of the language network.SIGNIFICANCE STATEMENTTraditional theories of the organisation of the cortical language network separate areas based on the type of information processed, such as distinct regions representing the meaning of words or their sounds. Here, we re-analyse and update a seminal study, to directly compare these networks. This differentiates some language regions, yet a high degree of overlap is found, suggesting this division alone, does not provide a full mapping of the language network. Additional dimensions, reflecting different kinds of information, are demonstrated to underlie the functional organisation of the language network. First, representation and control processes engage distinct regions in each subdomain. Secondly, comparison outside of language highlights the importance of a ‘domain-specificity’ dimension, distinguishing subdomain-specific semantic control and domain-general control regions.