Dorsal striatum coding for the timely execution of action sequences.

The automatic initiation of actions can be highly functional. But occasionally these actions cannot be withheld and are released at inappropriate times, impulsively. Striatal activity has been shown to participate in the timing of action sequence initiation and it has been linked to impulsivity. Using a self-initiated task, we trained adult male rats to withhold a rewarded action sequence until a waiting time interval has elapsed. By analyzing neuronal activity we show that the striatal response preceding the initiation of the learned sequence is strongly modulated by the time subjects wait before eliciting the sequence. Interestingly, the modulation is steeper in adolescent rats, which show a strong prevalence of impulsive responses compared to adults. We hypothesize this anticipatory striatal activity reflects the animals' subjective reward expectation, based on the elapsed waiting time, while the steeper waiting modulation in adolescence reflects age-related differences in temporal discounting, internal urgency states, or explore-exploit balance.

Spatial memory deficits in Alzheimer's disease and their connection to cognitive maps' formation by place cells and grid cells.

Whenever we navigate through different contexts, we build a cognitive map: an internal representation of the territory. Spatial navigation is a complex skill that involves multiple types of information processing and integration. Place cells and grid cells, collectively with other hippocampal and medial entorhinal cortex neurons (MEC), form a neural network whose activity is critical for the representation of self-position and orientation along with spatial memory retrieval. Furthermore, this activity generates new representations adapting to changes in the environment. Though there is a normal decline in spatial memory related to aging, this is dramatically increased in pathological conditions such as Alzheimer's disease (AD). AD is a multi-factorial neurodegenerative disorder affecting mainly the hippocampus-entorhinal cortex (HP-EC) circuit. Consequently, the initial stages of the disease have disorientation and wandering behavior as two of its hallmarks. Recent electrophysiological studies have linked spatial memory deficits to difficulties in spatial information encoding. Here we will discuss map impairment and remapping disruption in the HP-EC network, as a possible circuit mechanism involved in the spatial memory and navigation deficits observed in AD, pointing out the benefits of virtual reality as a tool for early diagnosis and rehabilitation.

Acute/subacute paracoccidioidomycosis with associated eosinophilia

Paracoccidioidomycosis is an endemic mycosis whose initial diagnosis may be difficult, as it shares the clinical characteristics of granulomatous and neoplastic diseases. Although its chronic form is the most frequent, we present the case of a young patient with an acute/ subacute presentation with lymphadenopathy, peripheral eosinophilia and a false-positive hepatitis C serology. The diagnosis was confirmed by histopathology and tissue culture, and he was treated with amphotericin B due to clinical deterioration secondary to progression of systemic involvement. (Acta Med Colomb 2021; 46. DOI: https://doi.org/10.36104/amc.2021.1921).

La paracoccidiodomicosis es una micosis endémica cuyo diagnóstico inicial puede ser difícil al compartir características clínicas de enfermedades granulomatosas y neoplásicas. Aunque su forma más frecuente es la crónica presentamos el caso de un paciente joven con un cuadro agudo/subagudo con linfadenopatías, eosinofilia periférica y una serología para hepatitis C falsamente positiva. El diagnóstico fue confirmado por histopatología y cultivo de tejidos y se dio manejo con anfotericina B ante el deterioro clínico por progresión del compromiso sistémico.

A Pilot Study of Facial Nerve Stimulation on Cerebral Artery Vasospasm in Subarachnoid Hemorrhage Patients.

BACKGROUND: The objective of this pilot study was to assess the safety and efficacy of VitalFlow stimulation in aneurysmal subarachnoid hemorrhage (aSAH) patients with vasospasm for the purpose of guiding the design of larger, controlled studies in vasospasm patients, a largely untreated condition [1]. METHODS: Six patients with angiographic vasospasm developing post-aSAH were treated with VitalFlow stimulation. Digital subtraction angiograms were obtained at the time of diagnosis (baseline) and then 30 minutes post-stimulation. A single 2-minute period of stimulation was delivered to the patients using parameters previously shown to be safe, tolerable, and effective at increasing cerebral blood flow (CBF) in healthy volunteers. RESULTS: VitalFlow stimulation improved tissue perfusion as assessed by parenchymography and reversed the constriction of vasospastic arteries. Two patients had only partial improvement and so were treated with intraarterial nimodipine after VitalFlow stimulation, whereas four patients had complete resolution of the vasospasm after VitalFlow stimulation per the treating neuroendovascular surgeon's evaluation. Clinical examination showed improvement in Hunt and Hess Scale scores assessed post-stimulation. CONCLUSIONS: Non-invasive magnetic stimulation of the facial nerve with the VitalFlow stimulator appears to be a safe and effective means to reverse angiographic vasospasm in aSAH patients. Clinical Impact: This study provides Class IV evidence that non-invasive magnetic stimulation of the facial nerves reduce angiographic vasospasm in aSAH patients.

Memory consolidation and expression of object recognition are susceptible to retroactive interference.

With the aim of analyzing if object recognition long-term memory (OR-LTM) formation is susceptible to retroactive interference (RI), we submitted rats to sequential sample sessions using the same arena but changing the identity of a pair of objects placed in it. Separate groups of animals were tested in the arena in order to evaluate the LTM for these objects. Our results suggest that OR-LTM formation was retroactively interfered within a critical time window by the exploration of a new, but not familiar, object. This RI acted on the consolidation of the object explored in the first sample session because its OR-STM measured 3h after training was not affected, whereas the OR-LTM measured at 24h was impaired. This sample session also impaired the expression of OR memory when it took place before the test. Moreover, local inactivation of the dorsal Hippocampus (Hp) or the medial Prefrontal Cortex (mPFC) previous to the exploration of the second pair of objects impaired their consolidation restoring the LTM for the objects explored in the first session. This data suggests that both brain regions are involved in the processing of OR-memory and also that if those regions are engaged in another process before finishing the first consolidation process its LTM will be impaired by RI.

Retroactive interference of object-in-context long-term memory: role of dorsal hippocampus and medial prefrontal cortex.

Retroactive interference (RI) is a type of amnesia in which a new learning experience can impair the expression of a previous one. It has been studied in several types of memories for over a century. Here, we aimed to study in the long-term memory (LTM) formation of an object-in-context task, defined as the recognition of a familiar object in a context different to that in which it was previously encountered. We trained rats with two sample trials, each taking place in a different context in association with different objects. Test sessions were performed 24 h later, to evaluate LTM for both object-context pairs using separate groups of trained rats. Furthermore, given the involvement of hippocampus (Hp) and medial prefrontal cortex (mPFC) in several recognition memories, we also analyzed the participation of these structures in the LTM formation of this task by the local infusion of muscimol. Our results show that object-in-context LTM formation is sensitive to RI by a different either familiar or novel object-context pair trial, experienced 1 h later. This interference occurs in a restricted temporal window and works on the LTM consolidation phase, leaving intact short-term memory expression. The second sample trial did not affect the object recognition part of the memory. Besides, muscimol treatment before the second sample trial blocks its object-in-context LTM and restores the first sample trial memory. We hypothesized that LTM-RI amnesia is probably caused by resources or cellular machinery competition in these brain regions when they are engaged in memory formation of the traces. In sum, when two different object-in-context memory traces are being processed, the second trace interferes with the consolidation of the first one requiring mPFC and CA1 dorsal Hp activation.

The tagging and capture hypothesis from synapse to memory.

The synaptic tagging and capture theory (STC) was postulated by Frey and Morris in 1997 and provided a strong framework to explain how to achieve synaptic specificity and persistence of electrophysiological-induced plasticity changes. Ten years later, the same argument was applied on learning and memory models to explain the formation of long-term memories, resulting in the behavioral tagging hypothesis (BT). These hypotheses are able to explain how a weak event that induces transient changes in the brain can establish long-lasting phenomena through a tagging and capture process. In this framework, it was postulated that the weak event sets a tag that captures plasticity-related proteins/products (PRPs) synthesized by an independent strong event. The tagging and capture processes exhibit symmetry, and therefore, PRPs can be captured if they are synthesized either before or after the setting of the tag. In summary, the hypothesis provides a wide framework that gives a solid explanation of how lasting changes occur and how the interaction between different events leads to promotion, reinforcement, or impairment of such changes. In this chapter, we will summarize the postulates of STC hypothesis, the common features between synaptic plasticity and memory, as well as a detailed compilation of the findings supporting the existence of BT process. At the end, we pose some questions related to BT mechanism and LTM formation, which probably will be answered in the near future.

Memory in Elementary School Children Is Improved by an Unrelated Novel Experience.

Education is the most traditional means with formative effect on the human mind, learning and memory being its fundamental support. For this reason, it is essential to find different strategies to improve the students performance. Based on previous work, we hypothesized that a novel experience could exert an enhancing effect on learning and memory within the school environment. Here we show that novel experience improved the memory of literary or graphical activities when it is close to these learning sessions. We found memory improvements in groups of students who had experienced a novel science lesson 1 hour before or after the reading of a story, but not when these events were 4 hours apart. Such promoting effect on long-term memory (LTM) was also reproduced with another type of novelty (a music lesson) and also after another type of learning task (a visual memory). Interestingly, when the lesson was familiar, it failed to enhance the memory of the other task. Our results show that educationally relevant novel events experienced during normal school hours can improve LTM for tasks/activities learned during regular school lessons. This effect is restricted to a critical time window around learning and is particularly dependent on the novel nature of the associated experience. These findings provide a tool that could be easily transferred to the classroom by the incorporation of educationally novel events in the school schedule as an extrinsic adjuvant of other information acquired some time before or after it. This approach could be a helpful tool for the consolidation of certain types of topics that generally demand a great effort from the children.

Memory traces compete under regimes of limited Arc protein synthesis: implications for memory interference.

Recently encoded information can be lost in the presence of new information, a process called 'retrograde interference'. Retrograde interference has been extensively described for more than a century; however, little is known about its underlying mechanisms. Different approaches agree on the need of the synthesis of plasticity related proteins (PRPs) to consolidate a long-term memory (LTM). Our hypothesis is that when PRPs are limited, interference of a task over LTM formation of another may be due to the utilization of protein resources common to both tasks. Here, by combining the tasks of inhibitory avoidance (IA) and open field (OF) exploration in rats, we show that memory traces compete for their stabilization if PRPs are limited. As a result, LTM is formed for only one of the tasks with a consequent decrease in the memory for the other. Furthermore, infusing Arc antisense oligonucleotide into the dorsal hippocampus, we found that Arc is necessary for LTM formation of these two types of learning tasks and is one of the PRPs that can be shared between them when animals are trained in both OF and IA. In sum, these findings suggest that under conditions of reduced protein availability, a learning task interferes with LTM formation of another by using the available PRPs.

Identification of transmitter systems and learning tag molecules involved in behavioral tagging during memory formation.

Long-term memory (LTM) consolidation requires the synthesis of plasticity-related proteins (PRPs). In addition, we have shown recently that LTM formation also requires the setting of a "learning tag" able to capture those PRPs. Weak training, which results only in short-term memory, can set a tag to use PRPs derived from a temporal-spatial closely related event to promote LTM formation. Here, we studied the involvement of glutamatergic, dopaminergic, and noradrenergic inputs on the setting of an inhibitory avoidance (IA) learning tag and the synthesis of PRPs. Rats explored an open field (PRP donor) followed by weak (tag inducer) or strong (tag inducer plus PRP donor) IA training. Throughout pharmacological interventions around open-field and/or IA sessions, we found that hippocampal dopamine D1/D5- and ß-adrenergic receptors are specifically required to induce PRP synthesis. Moreover, activation of the glutamatergic NMDA receptors is required for setting the learning tags, and this machinery further required α-Ca(2+)/calmodulin-dependent protein kinase II and PKA but not ERK1/2 activity. Together, the present findings emphasize an essential role of the induction of PRPs and learning tags for LTM formation. The existence of only the PRP or the tag was insufficient for stabilization of the mnemonic trace.

Behavioral tagging is a general mechanism of long-term memory formation.

In daily life, memories are intertwined events. Little is known about the mechanisms involved in their interactions. Using two hippocampus-dependent (spatial object recognition and contextual fear conditioning) and one hippocampus-independent (conditioned taste aversion) learning tasks, we show that in rats subjected to weak training protocols that induce solely short term memory (STM), long term memory (LTM) is promoted and formed only if training sessions took place in contingence with a novel, but not familiar, experience occurring during a critical time window around training. This process requires newly synthesized proteins induced by novelty and reveals a general mechanism of LTM formation that begins with the setting of a "learning tag" established by a weak training. These findings represent the first comprehensive set of evidences indicating the existence of a behavioral tagging process that in analogy to the synaptic tagging and capture process, need the creation of a transient, protein synthesis-independent, and input specific tag.

Efecto de la transferencia distal del recto anterior en la marcha de niños con parálisis cerebral espástica

Con base en el análisis fílmico de la marcha en niños con parálisis cerebral espástica, diagnosticamos coespasticidad en 14 rodillas que fueron sometidasa transferencia distal del recto anterior a los isquiotibiales. Obtuvimos aumento en la flexión de la rodilla en la fase de balanceo en todos los apcientes e igualmente mejoró la extensión antes del apoyo y durante el mismo. Nuestros resultados son comparables a los de la literatura. El análisis fílmico de la marcha es de utilidad para determinar la presencia de coespasticidad en algunos niños con parálisis cerebral espástica

Patrones morfológicos de las arcadas dentarias primarias: trabajo descriptivo-estadístico. Estudio preliminar / Morphologic patterns of dental arches. A descriptive-statistic work. Preliminary study

Se estudia la arcada normal de 50 niños entre tres y cinco años, clínicamente sanos, sin anomalías dentarias y con maxilares esqueléticamente equilibrados para obtener patrones descriptivos de la oclusión primaria en nuestra población. La referencia utilizada en la práctica responde a una población extranjera, por lo que consideramos necesario conocer las particularidades de nuestro fenotipo. Los resultados muestran que el maxilar superior es mayor transversalmente que el inferior, presentando un overjet perimétrico que permanece casi constante en caninos, primeros y segundos molares. Las separaciones interdentarias de los arcos dentarios se presentan en la versión de generalizados tanto en el maxilar superior (46 por ciento) como en el maxilar inferior (41 por ciento). El entrecruzamiento horizontal (92 por ciento) y vertical (86 por ciento) a nivel anterior es importante, con un overbite del tercio gingival o sobremordida severa (40 por ciento). Los elementos dentarios temporarios presentan un tamaño generalmente mayor a los obtenidos en otras poblaciones extranjeras. La relación canina y molar indican un 96 por ciento de clase I canina y 84 por ciento de plano terminal recto. Se describe un índice de la arcada temporaria al relacionar el ancho y el largo máximo

Patrones morfológicos de las arcadas dentarias primarias: trabajo descriptivo-estadístico. Estudio preliminar / Morphologic patterns of dental arches. A descriptive-statistic work. Preliminary study

Se estudia la arcada normal de 50 niños entre tres y cinco años, clínicamente sanos, sin anomalías dentarias y con maxilares esqueléticamente equilibrados para obtener patrones descriptivos de la oclusión primaria en nuestra población. La referencia utilizada en la práctica responde a una población extranjera, por lo que consideramos necesario conocer las particularidades de nuestro fenotipo. Los resultados muestran que el maxilar superior es mayor transversalmente que el inferior, presentando un overjet perimétrico que permanece casi constante en caninos, primeros y segundos molares. Las separaciones interdentarias de los arcos dentarios se presentan en la versión de generalizados tanto en el maxilar superior (46 por ciento) como en el maxilar inferior (41 por ciento). El entrecruzamiento horizontal (92 por ciento) y vertical (86 por ciento) a nivel anterior es importante, con un overbite del tercio gingival o sobremordida severa (40 por ciento). Los elementos dentarios temporarios presentan un tamaño generalmente mayor a los obtenidos en otras poblaciones extranjeras. La relación canina y molar indican un 96 por ciento de clase I canina y 84 por ciento de plano terminal recto. Se describe un índice de la arcada temporaria al relacionar el ancho y el largo máximo (AU)