About connections

Despite the attention attracted by "connectomics", one can lose sight of the very real questions concerning "What are connections?" In the neuroimaging community, "structural" connectivity is ground truth and underlying constraint on "functional" or "effective" connectivity. It is referenced to underlying anatomy; but, as increasingly remarked, there is a large gap between the wealth of human brain mapping and the relatively scant data on actual anatomical connectivity. Moreover, connections have typically been discussed as "pairwise", point x projecting to point y (or: to points y and z), or more recently, in graph theoretical terms, as "nodes" or regions and the interconnecting "edges". This is a convenient shorthand, but tends not to capture the richness and nuance of basic anatomical properties as identified in the classic tradition of tracer studies. The present short review accordingly revisits connectional weights, heterogeneity, reciprocity, topography, and hierarchical organization, drawing on concrete examples. The emphasis is on presynaptic long-distance connections, motivated by the intention to probe current assumptions and promote discussions about further progress and synthesis

Zinc-positive and zinc-negative connections of the claustrum

Three features often mentioned as characteristic of the claustrum are its widespread connections with cortical areas, the reciprocity of these connections in general, and the origin of cortico-claustral connections from a distinctive subtype of layer 6 pyramidal cells (Sherk, 1986; Katz, 1987; Tanne-Gariepy et al., 2002; Crick and Koch, 2005; Smythies et al., 2012). Another feature, often overlooked, is that a proportion of claustral-cortical neurons use synaptic zinc and that zinc+ terminations are moderately dense in the claustrum. This article will summarize data about zinc and the claustrum and present the case that cortico-claustral neurons might also be zinc-positive (Zn+). I conclude with comments on the likely implications for claustral identity and function

Colocalization of neurons in optical coherence microscopy and Nissl-stained histology in Brodmann’s area 32 and area 21

Published in final edited form as: Brain Struct Funct. 2019 January ; 224(1): 351–362. doi:10.1007/s00429-018-1777-z.Optical coherence tomography is an optical technique that uses backscattered light to highlight intrinsic structure, and when applied to brain tissue, it can resolve cortical layers and fiber bundles. Optical coherence microscopy (OCM) is higher resolution (i.e., 1.25 µm) and is capable of detecting neurons. In a previous report, we compared the correspondence of OCM acquired imaging of neurons with traditional Nissl stained histology in entorhinal cortex layer II. In the current method-oriented study, we aimed to determine the colocalization success rate between OCM and Nissl in other brain cortical areas with different laminar arrangements and cell packing density. We focused on two additional cortical areas: medial prefrontal, pre-genual Brodmann area (BA) 32 and lateral temporal BA 21. We present the data as colocalization matrices and as quantitative percentages. The overall average colocalization in OCM compared to Nissl was 67% for BA 32 (47% for Nissl colocalization) and 60% for BA 21 (52% for Nissl colocalization), but with a large variability across cases and layers. One source of variability and confounds could be ascribed to an obscuring effect from large and dense intracortical fiber bundles. Other technical challenges, including obstacles inherent to human brain tissue, are discussed. Despite limitations, OCM is a promising semi-high throughput tool for demonstrating detail at the neuronal level, and, with further development, has distinct potential for the automatic acquisition of large databases as are required for the human brain.Accepted manuscrip

Glutamatergic input from specific sources influences the nucleus accumbens-ventral pallidum information flow

The nucleus accumbens (NAc) is positioned to integrate signals originating from limbic and cortical areas and to modulate reward-related motor output of various goal-directed behaviours. The major target of the NAc GABAergic output neurons is the ventral pallidum (VP). VP is part of the reward circuit and controls the ascending mesolimbic dopamine system, as well as the motor output structures and the brainstem. The excitatory inputs governing this system converge in the NAc from the prefrontal cortex (PFC), ventral hippocampus (vHC), midline and intralaminar thalamus (TH) and basolateral nucleus of the amygdala (BLA). It is unclear which if any of these afferents innervate the medium spiny neurons of the NAc, that project to the VP. To identify the source of glutamatergic afferents that innervate neurons projecting to the VP, a dual-labelling method was used: Phaseolus vulgaris leucoagglutinin for anterograde and EGFP-encoded adenovirus for retrograde tract-tracing. Within the NAc, anterogradely labelled BLA terminals formed asymmetric synapses on dendritic spines that belonged to medium spiny neurons retrogradely labelled from the VP. TH terminals also formed synapses on dendritic spines of NAc neurons projecting to the VP. However, dendrites and dendritic spines retrogradely labelled from VP received no direct synaptic contacts from afferents originating from mPFC and vHC in the present material, despite the large number of fibres labelled by the anterograde tracer injections. These findings represent the first experimental evidence for a selective glutamatergic innervation of NAc neurons projecting to the VP. The glutamatergic inputs of different origin (i.e. mPFC, vHC, BLA, TH) to the NAc might thus convey different types of reward-related information during goal-directed behaviour, and thereby contribute to the complex regulation of nucleus accumbens functions.National Institutes of Health (U.S.) (Grants NS030549 and DA09158)GENADDICT Integrated Project (Grant LSHM-CT-2004-005166)National Office for Research and Technology (Hungary) (Grant CNK77793)Howard Hughes Medical Institute (Grant 55005608

Pyramidal neurons in the superficial layers of rat retrosplenial cortex exhibit a late-spiking firing property

The rodent granular retrosplenial cortex (GRS) is reciprocally connected with the hippocampus. It is part of several networks implicated in spatial learning and memory, and is known to contain head-direction cells. There are, however, few specifics concerning the mechanisms and microcircuitry underlying its involvement in spatial and mnemonic functions. In this report, we set out to characterize intrinsic properties of a distinctive population of small pyramidal neurons in layer 2 of rat GRS. These neurons, as well as those in adjoining layer 3, were found to exhibit a late-spiking (LS) firing property. We established by multiple criteria that the LS property is a consequence of delayed rectifier and A-type potassium channels. These were identified as Kv1.1, Kv1.4 and Kv4.3 by Genechip analysis, in situ hybridization, single-cell reverse transcriptase-polymerase chain reaction, and pharmacological blockade. The LS property might facilitate comparison or integration of synaptic inputs during an interval delay, consistent with the proposed role of the GRS in memory-related processes.RIKEN Brain Science Institut

Rastreio de desenvolvimento infantil : estudo exploratório do ASQ-2

O Ages and Stages Questionnaires (ASQ) é um instrumento referenciado pela bibliografia como facilitador da participação da família na avaliação. Os profissionais de educação e de saúde podem, através da utilização de instrumentos como o ASQ, auxiliar os pais no que respeita à detecção de factores de risco e à exploração de elementos de oportunidade para o desenvolvimento das competências de cada criança. O ASQ-2 é constituído por 19 questionários entre os 4 e os 60 meses de idade. Cada questionário é composto por 30 itens divididos por cinco áreas de desenvolvimento. O estudo do ASQ na amostra (n=339) da população portuguesa foi realizado, no sentido de observar as suas qualidades psicométricas, dando assim início à tradução e adaptação cultural para a população portuguesa. Os resultados obtidos respeitantes à sensibilidade, fiabilidade e validade do instrumento são atraentes para que se realize uma validação do ASQ para a população portuguesa, contribuindo assim, para o fornecimento de um instrumento de fácil compreensão por parte dos diferentes agentes educativos e de fácil preenchimento por parte dos pais. No que se refere ao rastreio de desenvolvimento realizado, o estudo identificou 129 crianças (38%) que necessitavam de avaliação mais específica de desenvolvimento e 39 pais preocupados com o desenvolvimento dos seus filhos

Comments and general discussion on “The anatomical problem posed by brain complexity and size: a potential solution”

Peer reviewedPeer Reviewe