Figure 8 - uploaded by Ignacio González-Burgos
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Diagram of the neural circuits that underlie procedural memory, mediated by the activity of the cerebellum. Panel A: cortico-pontine-cerebellum-thalamus-cortical circuit, involved in learning new habits and skills. 1) primary sensory neocortex; 2) pontine nuclei; 3) neocortex of the cerebellum; 4) neocerebellar dentate nucleus; 5) red nucleus; 6) nuclei of the thalamus; 7) premotor and motor neocortex. Panel B: spinocerebellum-rubrospinal circuit, involved in sensory-motor adaptations to those habits already acquired or to skills already learned. 1) spinal cord; 2) paleocortex of the cerebellum; 3) paleocerebellar globose and emboliform nuclei; 4) red nucleus; 5) spinal cord.
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... neuroanatomical participants in the organization of procedural implicit memory are diverse, but the cortico-cerebellum-thalamus-cortical and spinocerebellum-rubrospinal pathways (Figure 8) on the one hand, and the cortico-striatum-thalamus-cortical (Figure 9) pathway, on the other, participate in both the formation and improvement of habits and skills. It is widely believed that the cerebellum is involved in the learning and adaptation of motor sequences associated with the execution of the habits and skills required for the performance of procedural memory (Gaytán-Tocavén and Olvera-Cortés, 2004), while the striatum is particularly important as an integrating center for already learned information (Packard and Knowlton, 2002). ...
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... The information associated specifically with cognitive functions is processed by neurons that possess dendritic spines, the major sites for glutamate-mediated excitatory synaptic contacts in spiny neurons. E2mediated plastic changes in dendritic spines are closely related to the synaptic modulation of synaptic activity and cognitive performance (González-Burgos, 2009, 2022González-Burgos and Vázquez-Hernández, 2023). ...
... Their synaptic-related functioning is modulated by several extrasynaptic compounds, including steroid hormones that may induce various kinds of plastic changes (Luine and Frankfurt, 2023) including spine neoformation, pruning, and conformational changes among the different types of spines: thin, mushroom, stubby, wide, branched, and double (González-Burgos, 2022;González-Burgos and Velázquez-Zamora, 2023). Based on their geometric structure, typical spines are characterized by the presence of two regions: the head and neck (Harris and Stevens, 1989) that confer distinct functional properties to these spines (Gulledge, 2023). ...
... The upper region of the spine head and the area below the cell membrane contain terminals where intracellular transmembrane proteins that act as receptors are inserted in an organized way, together with proteins associated with the actin cytoskeleton and various biomolecules (González-Tapia and Flores-Soto, 2023) that are related to the signaling pathways of presynaptic stimuli (Zagrebelsky, 2023). Plastic changes in the latter lead to differential translation of cognition-related synaptic inputs , 2020González-Burgos, 2022). ...
The morphophysiology of the nervous system changes and adapts in response to external environmental inputs and the experiences of individuals throughout their lives. Other changes in the organisms internal environment can also contribute to nervous system restructuring in the form of plastic changes that underlie its capacity to adapt to emerging psychophysiological conditions. These adaptive processes lead to subtle modifications of the organisms internal homeostasis which is closely related with the activity of chemical messengers, such as neurotransmitters and hormones. Hormones reach the brain through the bloodstream, where they activate specific receptors through which certain biochemical, physiological, and morphological changes take place in numerous regions. Fetal development, infancy, puberty, and adulthood are all periods of substantial hormone-mediated brain remodeling in both males and females. Adulthood, specifically, is associated with a broad range of life events, including reproductive cycles in both sexes, and pregnancy and menopause in women. Events of this kind occur concomitantly with eventual modifications in behavioral performance and, especially, in cognitive abilities like learning and memory that underlie, at least in part, plastic changes in the dendritic spines of the neuronal cells in cerebral areas involved in processing cognitive information. Estrogens form a family that consists of three molecules [17β-estradiol (E2), estrone, estriol] which are deeply involved in regulating numerous bodily functions in different stages of the life-cycle, including the modulation of cognitive performance. This review addresses the effects of E2 on the dendritic spine-mediated synaptic organization of cognitive performance throughout the life span.
... Dendritic spines are cytoplasmic protrusions specialized in mediating excitatory synaptic activity. They have been associated with learning and memory processes in various brain structures [19,[35][36][37], including the mPFC and NAcc. Descriptions show that the geometric morphology of the dendritic spines can change depending on the characteristics of synaptic activity. ...
... Descriptions show that the geometric morphology of the dendritic spines can change depending on the characteristics of synaptic activity. Thin spines are involved in the most efficient transmission of excitatory synaptic impulses, which supports the acquisition of new information [35,38,39], while mushroom spines have been associated with the slow transmission of afferent synaptic information, which translates into its consolidation [35,40,41]. Thus, in addition to spine density, some other synaptic-related factors, such as the type of spines, could be associated with mnemonic information processing during the acquisition of sexual experience and this, in turn, could explain certain features of the pattern of male sexual behavior after repeated mating. ...
... Descriptions show that the geometric morphology of the dendritic spines can change depending on the characteristics of synaptic activity. Thin spines are involved in the most efficient transmission of excitatory synaptic impulses, which supports the acquisition of new information [35,38,39], while mushroom spines have been associated with the slow transmission of afferent synaptic information, which translates into its consolidation [35,40,41]. Thus, in addition to spine density, some other synaptic-related factors, such as the type of spines, could be associated with mnemonic information processing during the acquisition of sexual experience and this, in turn, could explain certain features of the pattern of male sexual behavior after repeated mating. ...
Sexual experience improves copulatory performance in male rats. Copulatory performance has been associated with dendritic spines density in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAcc), structures involved in the processing of sexual stimuli and the manifestation of sexual behavior. Dendritic spines modulate excitatory synaptic contacts, and their morphology is associated with the ability to learn from experience. This study was designed to determine the effect of sexual experience on the density of different types or shapes of dendritic spines in the mPFC and NAcc of male rats. A total of 16 male rats were used, half of them were sexually experienced while the other half were sexually inexperienced. After three sessions of sexual interaction to ejaculation, the sexually-experienced males presented shorter mount, intromission, and ejaculation latencies. Those rats presented a higher total dendritic density in the mPFC, and a higher numerical density of thin, mushroom, stubby, and wide spines. Sexual experience also increased the numerical density of mushroom spines in the NAcc. In both the mPFC and NAcc of the sexually experienced rats, there was a lower proportional density of thin spines and a higher proportional density of mushroom spines. Results show that the improvement in copulatory efficiency resulting from prior sexual experience in male rats is associated with changes in the proportional density of thin and mushroom dendritic spines in the mPFC and NAcc. This could represent the consolidation of afferent synaptic information in these brain regions, derived from the stimulus-sexual reward association.
Pentylenetetrazol (PTZ) blocks the inhibitory action of GABA, triggering a Glu-mediated hyperexcitation of the dendritic spines in hippocampal CA1 pyramidal neurons that leads to the generation of epileptiform seizures. The aim of this work was to determine the effect of PTZ on the electrical activity of the hippocampal pyramidal neurons in male rats. Bipolar electrodes were implanted stereotaxically in the right and left hippocampal CA1 fields of adults, and PTZ (65 mg/kg) was administered i.p. Simultaneous recordings of the field activity and the firing rate (multiunitary activity, MUA) were analyzed at 10, 20, and 30 min post-administration of PTZ. Only rats that presented tonic-clonic seizures during the first 1–5 min after PTZ treatment were included in the study. The recordings of the field activity were analyzed in 4 frequency bands. In both the right and left hippocampal CA1 fields, the relative power corresponding to the slow waves (4–7 Hz) increased, while in the bands 13–30 Hz and 31–50 Hz, it decreased at 10, 20, and 30 min post-PTZ. MUA recordings were analyzed at four levels. The highest levels corresponded to larger amplitudes of the action potentials in the pyramidal neurons. The firing rates of the PTZ-treated rats did not differ from baseline but presented a significant decrement at 10, 20, and 30 min post-PTZ. The decreased firing rate of the hippocampal CA1 pyramidal neurons after PTZ treatment could be associated with plastic changes of dendritic spines along with some microenvironmental adaptations at synaptic level, after neuronal PTZ-mediated hyperexcitation.
