144 research outputs found
Topological specification of connections between prefrontal cortex and hypothalamus in rhesus monkey
No full textThe hypothalamus is a subcortical brain region whose limits and constituent nuclei lack consensus. The hypothalamus has been linked to emotion and different states of stress, providing critical feedback about the internal environment to the prefrontal cortex, a region known for executive function within the cortex of humans. An understanding of the developmental origin of the hypothalamus can provide a basis for defining which limits and nuclei are ontologically hypothalamic, and which are not, as well as a framework for understanding its connectional relationship with other brain regions.
The Prosomeric Model (Rubenstein et al. 1994; Puelles and Rubenstein 2003; Nieuwenhuys and Puelles 2016; Puelles 2018) explains the embryological development of the central nervous system (CNS) shared by all vertebrates as a Bauplan. As a primary event, the early neural plate is patterned by intersecting longitudinal plates and transverse segments, forming a mosaic of progenitor units. The hypothalamus is specified by three prosomeres [hp1, hp2, and the acroterminal domain (At)] of the secondary prosencephalon with corresponding alar and basal plate parts, which develop apart from the diencephalon. Mounting evidence suggests that progenitor units within alar plate and basal plate parts of hp1 and hp2 give rise to distinct hypothalamic nuclei, which preserve their relative invariant positioning (topology) in the adult brain. Nonetheless, the principles of the Prosomeric Model have not been applied to the hypothalamus of adult primates.
The Structural Model (Barbas 1986; Barbas and Rempel-Clower 1997) highlights the variation of laminar structure in the grey matter of the prefrontal cortex as a basis for predicting specific cortico-cortical connections. The areas of the prefrontal cortex vary along a spectrum by number of layers, laminar definition, and cellularity of those layers. The systematic laminar patterns of different areas of the prefrontal cortex seem to be associated with differential rates of development or maturation. A topographical analysis of bidirectional projections between the prefrontal cortex and the hypothalamus was previously applied using the Structural Model (Rempel-Clower and Barbas 1998). The authors found the prefrontal cortex has highly specific projections to the hypothalamus, originating mostly from limbic orbital and medial prefrontal areas, which have lower laminar definition than other prefrontal areas. In addition, the hypothalamus has relatively specific patterns of projection to the prefrontal cortex.
We previously lacked an organizing principle to examine the specific pattern of connections between the hypothalamus and prefrontal cortex in adult rhesus monkey. In the present study, hypothalamic nuclei in the rhesus monkey (Macaca mulatta) were parcellated using classic architectonic boundaries and stains. The topological relations of hypothalamic nuclei and adjacent hypothalamic landmarks were then analyzed with homology across rodent and primate species to trace the origin of adult hypothalamic nuclei to the alar or basal plate components of hp1 and hp2. A novel atlas of the hypothalamus of the adult rhesus monkey was generated with developmental ontologies for each hypothalamic nucleus. This atlas was then applied to a topological analysis of the strength and pattern of connections between the hypothalamus and prefrontal cortex in the adult rhesus monkey. The result is a systematic reinterpretation of the adult hypothalamus of the rhesus monkey whose prosomeric ontology was used to study connections and neuraxial pathways linking the hypothalamus and prefrontal cortex. The convergence of the Prosomeric and Structural Models provides a framework through development to explain the structural patterns found in the adult primate cortex and hypothalamus, and the likely consequences of their disruption
Humour, satire et absurde dans <i>Um homem de barbas</i> de Manuel de Lima
No full textInternational audienceManuel de Lima (1915–1976), violinist, painter and music critic, began his writing career in 1944 with the long short-story Um homem de barbas [A man with a beard]. It was the middle of the Second World War and the Salazar dictatorship was well established in officially neutral Portugal. A few years before the belated emergence of Portuguese surrealism, to which he was linked, and in the midst of the development of neorealism, a protest movement followed mainly by the young writers of the time,Manuel de Lima asserted himself from the outset as a very singular writer. Um homem de barbas is a narrative of a love triangle that ends with the spectacular disappearance of the three protagonists. In this first work placed under the sign of the absurd, which mixes satire, marvelous, and burlesque and in which, according to Almada Negreiros' 1944 preface, the author uses realism to "undo realism", we will study the place and role of humor, as well as the various devices used.Manuel de Lima (1915–1976), violoniste, peintre et critique musical, initie sa carrière d’écrivain en 1944 avec la nouvelle Um homem de barbas [Un homme à barbe]. On est alors en pleine Seconde guerre mondiale et, au Portugal, officiellement neutre, la dictature salazariste est bien implantée. Quelques années avant l’apparition, tardive, du surréalisme portugais, auquel il sera rattaché, et en plein développement du néoréalisme, voie contestataire majoritairement suivie par les jeunes écrivains de l’époque, Manuel de Lima s’affirme dès ses débuts comme un écrivain très singulier. Um homem de barbas est le récit d’un triangle amoureux qui se termine par la disparition spectaculaire des trois protagonistes. Dans ce premier opus placé sous le signe de l’absurde, qui mêle satire, merveilleux et burlesque et où, selon le préfacier Almada Negreiros (1944), l’auteur se sert du réalisme pour "défaire le réalisme", nous étudierons la place et le rôle de l’humour ainsi que les divers procédés utilisés
The cortical connections of area 25 and its interactions with areas involved in emotion and cognition
No full textThe equilibrium between cognition and emotion among shifting prefrontal networks is necessary for flexible behavior in the primate, but the organization of the circuitry involved is largely unknown. The subgenual cingulate area 25 (A25) has been strongly associated with affect and somatic states based on clinical evidence and functional studies in non-human primates. The dorsolateral prefrontal cortex (DLPFC), on the other hand, is associated with cognition and executive function. Both areas are robustly connected with pregenual cingulate area 32 (A32), implicated in both affective and cognitive functions. A32 may thus be positioned to balance activity between these two functionally disparate prefrontal regions. This issue was addressed by mapping the largely unidentified cortical connectome of A25 to understand its position in prefrontal networks. A25 was most strongly connected with other ventromedial and posterior orbitofrontal areas associated with emotions and internal homeostasis. Connectional patterns showed that A25 is a major prefrontal feedback system, positioned to exert a widespread influence on other areas. A25 was also robustly connected with auditory association areas, memory-related medial temporal cortices, and with the interoceptive-related anterior insula. Connectional patterns with memory-related medial areas, the posterior orbitofrontal cortex, and the anterior insula suggest that activity is initiated in A25 and flows in a feedforward pattern to these areas. Weak to sparse connections linked the DLPFC and A25. To determine how affective signals from A25 and cognitive signals from the DLPFC may be integrated in prefrontal circuits, high resolution mapping techniques revealed that A32 densely targeted modulatory inhibitory neurons in the superficial layers and strong inhibitory neurons in the deep layers of A25. These data suggest that A32 can tune activity in A25 cortical columns and convey signals pertaining to ongoing prefrontal processes. The sequential pathway from the DLPFC to A32 may help dampen A25 output by predominant innervation of the strong inhibitory microsystem in the deep layers of A25. These findings indicate that A32 is positioned to recruit or reduce activity in A25 as needed, demonstrating a circuit mechanism for the delicate integration of cognition and emotion and its potential disruption in mood disorders
Pathways linking amygdala, hippocampus and anterior cingulate cortex in emotion, cognition and memory
No full textThe interaction of emotion and memory is necessary for establishing a cognitive
map including current context and past experiences, which is used by prefrontal cortex to
regulate the internal state and guide goal directed actions and decision making. The
amygdala, hippocampus and anterior cingulate cortex (ACC) play critical roles in these
processes, but the organization of pathways between them is largely unknown in
primates. This issue was addressed using neural tracers in rhesus monkeys to label the
bidirectional pathways between amygdala and hippocampus and the unidirectional
pathway from hippocampus to ACC. The amygdala sent a robust projection to
hippocampus that formed large and closely spaced dual synapses on spines from the same
dendritic segment, suggesting a strong influence. Further, amygdalar axon boutons
innervated some disinhibitory calretinin neurons in CA1, suggesting enhanced excitatory
influence. In contrast, in CA3 the amygdala pathway innervated calretinin and some of
the powerful parvalbumin inhibitory neurons, which may help enhance memory of
affective events. The reverse pathway from hippocampus densely and mainly targeted the
ventro-medial part of the amygdala, including the basolateral (BL) and paralaminar
basolateral (PLBL) nuclei. Hippocampal terminations formed synapses mostly on spines
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of presumed excitatory neurons. Some hippocampal terminations innervated inhibitory
neurons in BL and PLBL and showed a rank of preference, by targeting mostly calretinin,
and then calbindin and least parvalbumin inhibitory neurons. This pattern of innervation
may allow contextual information represented by hippocampus to influence affective
processes in the amygdala. The hippocampus sent strong projections to ACC (A32, A24a
and A25) and targeted particularly A25, suggesting a role in affective and autonomic
regulation. About 90% of hippocampal terminations in A25 innervated excitatory
neurons, suggesting strong excitatory effects. The hippocampal pathway had a close
relationship with postsynaptic D1 receptors in A25, especially in the deep layers.
Dopamine has a strong influence in goal-directed actions, rewards, and attention in
prefrontal cortex in primates, and may facilitate contextual information from the
hippocampus to A25 to influence emotional regulation. The pathways studied were
distinct, and suggest specific roles in emotional memory by the amygdala in
hippocampus, in flexible learning and forgetting fear based on context transmitted from
hippocampus to the amygdala, and in the synthesis of current context and past experience
carried out by the hippocampal pathway to ACC to influence adaptive goal directed
behavior.2021-09-27T00:00:00
Direction selectivity of neurons in the visual cortex is non‐linear and lamina‐dependent
No full textNeurons in the visual cortex are generally selective to direction of movement of a stimulus. Although models of this direction selectivity (DS) assume linearity, experimental data show stronger degrees of DS than those predicted by linear models. Our current study was intended to determine the degree of non-linearity of the DS mechanism for cells within different laminae of the cat's primary visual cortex. To do this, we analysed cells in our database by using neurophysiological and histological approaches to quantify non-linear components of DS in four principal cortical laminae (layers 2/3, 4, 5, and 6). We used a DS index (DSI) to quantify degrees of DS in our sample. Our results showed laminar differences. In layer 4, the main thalamic input region, most neurons were of the simple type and showed high DSI values. For complex cells in layer 4, there was a broad distribution of DSI values. Similar features were observed in layer 2/3, but complex cells were dominant. In deeper layers (5 and 6), DSI value distributions were characterized by clear peaks at high values. Independently of specific lamina, high DSI values were accompanied by narrow orientation tuning widths. Differences in orientation tuning for non-preferred vs. preferred directions were smallest in layer 4 and largest in layer 6. These results are consistent with a non-linear process of intra-cortical inhibition that enhances DS by selective suppression of neuronal firing for non-preferred directions of stimulus motion in a lamina-dependent manner. Other potential mechanisms are also considered
Neural architecture of Area 25 of the anterior cingulate cortex and its potential disruption in stage II chronic traumatic encephalopathy
No full textChronic Traumatic Encephalopathy (CTE) is a neurodegenerative disorder that is associated with repetitive head injury (RHI), which includes both traumatic and subclinical brain injuries. Early CTE is a tauopathy that has patchy distribution of hyperphosphorylated tau within the depths of sulci which progressively spreads. Recent studies of RHI show that deep areas of the brain are most affected during head impacts, with strain due to shearing forces peaking at deep brain regions on the midline. The anterior cingulate cortex (ACC), which is directly on the midline, is likely one of the first regions to be affected by shearing forces yet there have been few studies of the cellular irregularities in the ACC at early stages of CTE. The present study investigated the proportions of inhibitory to excitatory neurons in a midline ACC area, Area 25 (A25), in neurotypical and stage II CTE cases using immunohistochemistry and Nissl staining to investigate neuronal subpopulation densities. Inhibitory neuron subpopulations in the human cortex can be labeled by three calcium binding proteins: parvalbumin (PV), calbindin (CB), and calretinin (CR). CB and PV interneurons differentially inhibit excitatory neurons while CR neurons in the upper cortical layers inhibit other inhibitory neurons, resulting in a disinhibitory effect. The results showed that the density of CB neurons significantly decreased in stage II CTE. In addition, CR neuron density may also be reduced but results for PV neurons were inconclusive. The disruption of inhibitory neurons in A25 may be an early change and may contribute to the early clinical presentation of CTE. A25 of the ACC is known to be involved in affective disorders and specifically is overactive in major depressive disorder, which is also experienced by individuals in the early stages of CTE.2026-09-26T00:00:00
Effects of sequential lesions of the visual cortex on relearning of pattern or brightness discriminations in the rat
No full textDigitized by Kansas Correctional Industrie
Connections underlying the synthesis of cognition, memory, and emotion in primate prefrontal cortices
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