RESUMEN
ANATOMY OF MEMORY. Memory phenomena involve neuron circuits and neurogenesis processes at the microscopic level. Nevertheless, the central role played by some key structures such as the hippocampus and the limbic lobe requires a good knowledge of their macroscopic anatomy. This article summarizes an overview of the anatomical organization of these structures and of their abundant connections.
ANATOMIE DE LA MÉMOIRE. Les phénomènes mnésiques mettent en jeu à l'échelle microscopique des circuits neuronaux et des processus de neurogenèse. Néanmoins, le rôle central joué par certaines structures clés comme l'hippocampe ou le lobe limbique impose une bonne connaissance de leur anatomie macroscopique. Cet article propose une synthèse de l'organisation anatomique de ces structures et de leurs riches connexions.
Asunto(s)
Hipocampo , Lóbulo Límbico , Memoria , Humanos , Hipocampo/anatomía & histología , Lóbulo Límbico/anatomía & histologíaRESUMEN
Olfactory function, and specifically semantic olfactory memory (i.e., odor identification), has frequently been shown to predict cognitive functioning across multiple domains in old age. This observation suggests that olfactory function can serve as a marker for the integrity of temporolimbic cortical networks, but a clear delineation of this association is still missing. To address this issue, the present study employed voxel-based morphometry in a region of interest-based design to determine the extent to which gray matter volumes of core olfactory and memory areas are associated with olfactory memory performance in an aging population free from neurodegenerative disease. We further aimed to determine potential overlap in structural anatomical correlates, and differences in association strength, for semantic and episodic olfactory memory. Structural magnetic resonance imaging (MRI), episodic and semantic odor memory and episodic and semantic verbal memory data were collected in 422 participants from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), all aged â≥ â60 years. Controlling for age and education, semantic, but not episodic, olfactory memory was positively related to gray matter volume in a cluster extending from the anterior hippocampus and amygdala into the posterior piriform cortex. The observed associations remained even when verbal memory performance was controlled for, supporting a link between the olfactory memory domain and cortical volume over and above more generalized memory abilities. As such, our data provide evidence for distinct functional-structural associations for semantic odor memory, supporting the idea of temporolimbic integrity as a neurobiological substrate linking olfactory function to cognitive health in old age.
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Envejecimiento/fisiología , Sustancia Gris/anatomía & histología , Lóbulo Límbico/anatomía & histología , Memoria/fisiología , Red Nerviosa/anatomía & histología , Corteza Olfatoria/anatomía & histología , Percepción Olfatoria/fisiología , Lóbulo Temporal/anatomía & histología , Anciano , Anciano de 80 o más Años , Femenino , Sustancia Gris/diagnóstico por imagen , Encuestas Epidemiológicas , Humanos , Lóbulo Límbico/diagnóstico por imagen , Imagen por Resonancia Magnética , Masculino , Memoria Episódica , Persona de Mediana Edad , Red Nerviosa/diagnóstico por imagen , Corteza Olfatoria/diagnóstico por imagen , Semántica , Suecia , Lóbulo Temporal/diagnóstico por imagenRESUMEN
Psychostimulant use is an ever-increasing socioeconomic burden, including a dramatic rise during pregnancy. Nevertheless, brain-wide effects of psychostimulant exposure are incompletely understood. Here, we performed Fos-CreERT2-based activity mapping, correlated for pregnant mouse dams and their fetuses with amphetamine, nicotine, and caffeine applied acutely during midgestation. While light-sheet microscopy-assisted intact tissue imaging revealed drug- and age-specific neuronal activation, the indusium griseum (IG) appeared indiscriminately affected. By using GAD67gfp/+ mice we subdivided the IG into a dorsolateral domain populated by γ-aminobutyric acidergic interneurons and a ventromedial segment containing glutamatergic neurons, many showing drug-induced activation and sequentially expressing Pou3f3/Brn1 and secretagogin (Scgn) during differentiation. We then combined Patch-seq and circuit mapping to show that the ventromedial IG is a quasi-continuum of glutamatergic neurons (IG-Vglut1+) reminiscent of dentate granule cells in both rodents and humans, whose dendrites emanate perpendicularly toward while their axons course parallel with the superior longitudinal fissure. IG-Vglut1+ neurons receive VGLUT1+ and VGLUT2+ excitatory afferents that topologically segregate along their somatodendritic axis. In turn, their efferents terminate in the olfactory bulb, thus being integral to a multisynaptic circuit that could feed information antiparallel to the olfactory-cortical pathway. In IG-Vglut1+ neurons, prenatal psychostimulant exposure delayed the onset of Scgn expression. Genetic ablation of Scgn was then found to sensitize adult mice toward methamphetamine-induced epilepsy. Overall, our study identifies brain-wide targets of the most common psychostimulants, among which Scgn+/Vglut1+ neurons of the IG link limbic and olfactory circuits.
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Mapeo Encefálico , Encéfalo/metabolismo , Regulación de la Expresión Génica , Lóbulo Límbico/metabolismo , Animales , Axones/metabolismo , Encéfalo/diagnóstico por imagen , Dendritas/metabolismo , Femenino , Glutamato Descarboxilasa/genética , Humanos , Interneuronas/metabolismo , Lóbulo Límbico/anatomía & histología , Lóbulo Límbico/efectos de los fármacos , Ratones , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Bulbo Olfatorio/metabolismo , Factores del Dominio POU/genética , Factores del Dominio POU/metabolismo , Secretagoginas/genética , Secretagoginas/metabolismo , Proteína 1 de Transporte Vesicular de Glutamato/genética , Proteína 1 de Transporte Vesicular de Glutamato/metabolismo , Proteína 2 de Transporte Vesicular de Glutamato/genética , Proteína 2 de Transporte Vesicular de Glutamato/metabolismo , Ácido gamma-Aminobutírico/metabolismoRESUMEN
Training-induced neuroplasticity has been described in athletes' population. However, it remains largely unknown how regular training and sports proficiency modifies neuronal circuits in the human brain. In this study, we used voxel-based morphometry and stepwise functional connectivity (SFC) analyses to uncover connectivity changes in the functional stream architecture in student-athletes at early stages of sensorimotor skill training. Thirty-two second-year student-athletes whose major was little-ball sports and thirty-four nonathlete controls were recruited for the study. We found that athletes showed greater gray matter volume in the right sensorimotor area, the limbic lobe, and the anterior lobe of the cerebellum. Furthermore, SFC analysis demonstrated that athletes displayed significantly smaller optimal connectivity distance from those seed regions to the dorsal attention network (DAN) and larger optimal connectivity distance to the default mode network (DMN) compared to controls. The Attention Network Test showed that the reaction time of the orienting attention subnetwork was positively correlated with SFC between the seeds and the DAN, while negatively correlated with SFC between the seeds and the DMN. Our findings suggest that neuroplastic adaptations on functional connectivity streams after motor skill training may enable novel information flow from specific areas of the cortex toward distributed networks such as the DAN and the DMN. This could potentially regulate the focus of external and internal attention synchronously in athletes, and consequently accelerate the reaction time of orienting attention in athletes.
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Adaptación Fisiológica/fisiología , Atletas , Atención/fisiología , Cerebelo , Corteza Cerebral/fisiología , Conectoma/métodos , Sustancia Gris/anatomía & histología , Destreza Motora/fisiología , Red Nerviosa/fisiología , Plasticidad Neuronal/fisiología , Adulto , Cerebelo/anatomía & histología , Cerebelo/diagnóstico por imagen , Cerebelo/fisiología , Corteza Cerebral/anatomía & histología , Corteza Cerebral/diagnóstico por imagen , Sustancia Gris/diagnóstico por imagen , Humanos , Lóbulo Límbico/anatomía & histología , Lóbulo Límbico/diagnóstico por imagen , Imagen por Resonancia Magnética , Red Nerviosa/diagnóstico por imagen , Corteza Sensoriomotora/anatomía & histología , Corteza Sensoriomotora/diagnóstico por imagen , Corteza Sensoriomotora/fisiología , Adulto JovenRESUMEN
Previous studies of trait emotional awareness (EA) have not yet examined whether differences in cortical structure might account for differences in EA. Based on previous research on the relationship between EA and both emotion conceptualization and visceromotor control processes, we tested two hypotheses in a sample of 26 healthy participants: that higher EA would be predicted by greater cortical thickness within (1) regions of the default mode network (DMN; linked with conceptualization processes), and/or (2) regions of the limbic network (linked with affect generation and visceromotor control processes). A non-significant correlation was found between EA and cortical thickness in the DMN. In contrast, a significant positive correlation was observed between EA and cortical thickness within the limbic network. These findings suggest that the structural integrity of cortical regions involved in the generation of affective bodily reactions may play a more important role in explaining differences in EA than previously thought.
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Concienciación/fisiología , Emociones/fisiología , Lóbulo Límbico/anatomía & histología , Imagen por Resonancia Magnética/métodos , Red Nerviosa/anatomía & histología , Personalidad/fisiología , Corteza Prefrontal/anatomía & histología , Adulto , Femenino , Humanos , Lóbulo Límbico/diagnóstico por imagen , Lóbulo Límbico/fisiología , Masculino , Red Nerviosa/diagnóstico por imagen , Red Nerviosa/fisiología , Corteza Prefrontal/diagnóstico por imagen , Corteza Prefrontal/fisiología , Adulto JovenRESUMEN
The limbic lobe defined by Broca is a cortical region with highly diverse structure and functions, and comprises the paleo-, archi-, and neocortices as well as their transitional zones. In the limbic lobe, Brodmann designated areas 27, 28, 34, 35, and 36 adjacent to the hippocampus, and areas 23, 24, 25, 26, 29, 30, 31, 32, and 33 around the corpus callosum. In the current literature, areas 27 and 28 correspond to the presubiculum and entorhinal cortex, respectively. Area 34 represents the cortico-medial part of the amygdaloid complex. Areas 35 and 36 roughly cover the perirhinal and parahippocampal cortices. Areas 24, 25, 32, and 33 belong to the anterior cingulate gyrus, while areas 23, 26, 29, 30, and 31 to the posterior cingulate gyrus. Areas 25, 32, and the anteroinferior portion of area 24 are deeply involved in emotional responses, particularly in their autonomic functions, through reciprocal connections with the amygdaloid complex, anterior thalamus and projections to the brainstem and spinal visceral centers. Areas 29 and 30 have dense reciprocal connections with areas 23 and 31, the dorsolateral prefrontal areas, and the regions related to the hippocampus. They play pivotal roles in mediating spatial cognition, working memory processing, and episodic memory formation.
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Cognición/fisiología , Lóbulo Límbico/fisiología , Memoria Episódica , Percepción Espacial/fisiología , Animales , Mapeo Encefálico , Humanos , Lóbulo Límbico/anatomía & histología , Red NerviosaRESUMEN
Mind-wandering has a controversial relationship with cognitive control. Existing psychological evidence supports the hypothesis that episodes of mind-wandering reflect a failure to constrain thinking to task-relevant material, as well the apparently alternative view that control can facilitate the expression of self-generated mental content. We assessed whether this apparent contradiction arises because of a failure to consider differences in the types of thoughts that occur during mind-wandering, and in particular, the associated level of intentionality. Using multi-modal magnetic resonance imaging (MRI) analysis, we examined the cortical organisation that underlies inter-individual differences in descriptions of the spontaneous or deliberate nature of mind-wandering. Cortical thickness, as well as functional connectivity analyses, implicated regions relevant to cognitive control and regions of the default-mode network for individuals who reported high rates of deliberate mind-wandering. In contrast, higher reports of spontaneous mind-wandering were associated with cortical thinning in parietal and posterior temporal regions in the left hemisphere (which are important in the control of cognition and attention) as well as heightened connectivity between the intraparietal sulcus and a region that spanned limbic and default-mode regions in the ventral inferior frontal gyrus. Finally, we observed a dissociation in the thickness of the retrosplenial cortex/lingual gyrus, with higher reports of spontaneous mind-wandering being associated with thickening in the left hemisphere, and higher repots of deliberate mind-wandering with thinning in the right hemisphere. These results suggest that the intentionality of the mind-wandering state depends on integration between the control and default-mode networks, with more deliberation being associated with greater integration between these systems. We conclude that one reason why mind-wandering has a controversial relationship with control is because it depends on whether the thoughts emerge in a deliberate or spontaneous fashion.
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Encéfalo/fisiología , Individualidad , Intención , Pensamiento/fisiología , Adulto , Encéfalo/anatomía & histología , Mapeo Encefálico , Femenino , Lóbulo Frontal/anatomía & histología , Lóbulo Frontal/fisiología , Humanos , Lóbulo Límbico/anatomía & histología , Lóbulo Límbico/fisiología , Imagen por Resonancia Magnética , Masculino , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiología , Lóbulo Parietal/anatomía & histología , Lóbulo Parietal/fisiología , Lóbulo Temporal/anatomía & histología , Lóbulo Temporal/fisiología , Adulto JovenRESUMEN
The superior colliculus (SC) is a midbrain structure central to orienting behaviors. The organization of descending projections from sensory cortices to the SC has garnered much attention; however, rarely have projections from multiple modalities been quantified and contrasted, allowing for meaningful conclusions within a single species. Here, we examine corticotectal projections from visual, auditory, somatosensory, motor, and limbic cortices via retrograde pathway tracers injected throughout the superficial and deep layers of the cat SC. As anticipated, the majority of cortical inputs to the SC originate in the visual cortex. In fact, each field implicated in visual orienting behavior makes a substantial projection. Conversely, only one area of the auditory orienting system, the auditory field of the anterior ectosylvian sulcus (fAES), and no area involved in somatosensory orienting, shows significant corticotectal inputs. Although small relative to visual inputs, the projection from the fAES is of particular interest, as it represents the only bilateral cortical input to the SC. This detailed, quantitative study allows for comparison across modalities in an animal that serves as a useful model for both auditory and visual perception. Moreover, the differences in patterns of corticotectal projections between modalities inform the ways in which orienting systems are modulated by cortical feedback. J. Comp. Neurol. 524:2623-2642, 2016. © 2016 Wiley Periodicals, Inc.
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Corteza Auditiva/anatomía & histología , Lóbulo Límbico/anatomía & histología , Corteza Motora/anatomía & histología , Corteza Somatosensorial/anatomía & histología , Colículos Superiores/anatomía & histología , Corteza Visual/anatomía & histología , Animales , Corteza Auditiva/fisiología , Vías Auditivas/anatomía & histología , Vías Auditivas/fisiología , Gatos , Femenino , Lóbulo Límbico/fisiología , Corteza Motora/fisiología , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiología , Corteza Somatosensorial/fisiología , Colículos Superiores/fisiología , Corteza Visual/fisiologíaRESUMEN
Paul Broca's concept of the "great limbic lobe" has had a huge impact on neuroscience. In this commentary, which accompanies the first English translation of the original paper, we comment on Broca's contribution and its influence on the understanding of the brain bases of emotion.
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Lóbulo Límbico/anatomía & histología , Lóbulo Límbico/fisiología , Sistema Límbico/anatomía & histología , Sistema Límbico/fisiología , Animales , Historia del Siglo XIX , Historia del Siglo XX , Humanos , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiología , Neuroanatomía/historiaRESUMEN
Several lines of evidence indicate that the dorsal hippocampus (dH) and medial prefrontal cortex (mPFC) regulate contextual fear conditioning. The prelimbic (PrL), infralimbic (IL) and the anterior cingulate cortex (ACC) subregions of the mPFC likely play distinct roles in the expression of fear. Moreover, studies have highlighted the role of serotonin (5-hydroxytryptamine, 5-HT)- and γ-aminobutyric acid (GABA)-mediated mechanisms in the modulation of innate fear in the mPFC. The present study characterized dH-mPFC pathways and investigated the role of serotonergic and GABAergic mechanisms of the PrL, IL and ACC-area 1 (Cg1) in the elaboration of contextual fear conditioning using fear-potentiated startle (FPS) and freezing behavior in Rattus norvegicus. The results of neurotracing with microinjections of biotinylated dextran amine into the dH revealed a neural link of the dH with the PrL and ACC. Intra-PrL injections of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and the GABAA receptor-selective agonist muscimol reduced contextual FPS and freezing responses. Intra-Cg1 injections of muscimol but not 8-OH-DPAT decreased FPS and freezing responses. However, neither intra-IL injections of a 5-HT1A agonist nor of a GABAA agonist affected these defensive responses. Labeled neuronal fibers from the dH reached the superficial layers of the PrL cortex and spread to the inner layers of PrL and Cg1 cortices, supporting the pharmacological findings. The present results confirmed the involvement of PrL and Cg1 in the expression of FPS and freezing responses to aversive conditions. In addition, PrL serotoninergic mechanisms play a key role in contextual fear conditioning. This study suggests that PrL, IL and Cg1 distinctively contribute to the modulation of contextual fear conditioning.