Behavioral and neuronal attributes of short- and long-term habituation in the crab Chasmagnathus

Investigations using invertebrate species have led to a considerable progress in our understanding of the mechanisms underlying learning and memory. In this review we describe the main behavioral and neuronal findings obtained by studying the habituation of the escape response to a visual danger stimulus in the crab Chasmagnathus granulatus. Massed training with brief intertrial intervals lead to a rapid reduction of the escape response that recovers after a short term. Conversely, few trials of spaced training renders a slower escape reduction that endures for many days. As predicted by Wagner’s associative theory of habituation, long-term habituation in the crab proved to be determined by an association between the contextual environment of the training and the unconditioned stimulus. By performing intracellular recordings in the brain of the intact animal at the same time it was learning, we identified a group of neurons that remarkably reflects the short- and long-term behavioral changes. Thus, the visual memory abilities of crabs, their relatively simple and accessible nervous system, and the recording stability that can be achieved with their neurons provide an opportunity for uncovering neurophysiological and molecular events that occur in identifiable neurons during learning.     

Cholinergic septo-hippocampal innervation is required for trace eyeblink classical conditioning

We studied the effects of a selective lesion in rats, with 192-IgG-saporin, of the cholinergic neurons located in the medial septum/diagonal band (MSDB) complex on the acquisition of classical and instrumental conditioning paradigms. The MSDB lesion induced a marked deficit in the acquisition, but not in the retrieval, of eyeblink classical conditioning using a trace paradigm. Such a deficit was task-selective, as lesioned rats were able to acquire a fixed-interval operant conditioning as controls, and was not due to nonspecific motor alterations, because spontaneous locomotion and blink reflexes were not disturbed by the MSDB lesion. The deficit in the acquisition of a trace eyeblink classical conditioning was reverted by the systemic administration of carbachol, a nonselective cholinergic muscarinic agonist, but not by lobeline, a nicotinic agonist. These results suggest a key role of muscarinic denervation on the acquisition of new motor abilities using trace classical conditioning procedures. It might also be suggested that muscarinic agents would be useful for the amelioration of some associative learning deficits observed at early stages in patients with Alzheimer's disease.     

Classical conditioning of eyelid and mystacial vibrissae responses in conscious mice

The murine vibrissae sensorimotor system has been scrutinized as a target of motor learning through trace classical conditioning. Conditioned eyelid responses were acquired by using weak electrical whisker-pad stimulation as conditioned stimulus (CS) and strong electrical periorbital stimulation as unconditioned stimulus (US). In addition, conditioned vibrissal protraction was obtained pairing either weak electrical whisker-pad stimulation or a tone as CS, with a strong electric shock delivered in the whisker-pad as US. This finding suggests that evolutionary pressure has selected a sensorimotor system capable of constructing conditioned responses on the basis of temporal relationships of stimuli, independently of any putative functional purpose.     

Learning-dependent potentiation in the vibrissal motor cortex is closely related to the acquisition of conditioned whisker responses in behaving mice

The role of the primary motor cortex in the acquisition of new motor skills was evaluated during classical conditioning of vibrissal protraction responses in behaving mice, using a trace paradigm. Conditioned stimulus (CS) presentation elicited a characteristic field potential in the vibrissal motor cortex, which was dependent on the synchronized firing of layer V pyramidal cells. CS-evoked and other event-related potentials were particular cases of a motor cortex oscillatory state related to the increased firing of pyramidal neurons and to vibrissal activities. Along conditioning sessions, but not during pseudoconditioning, CS-evoked field potentials and unitary pyramidal cell responses grew with a time-course similar to the percentage of vibrissal conditioned responses (CRs), and correlated significantly with CR parameters. High-frequency stimulation of barrel cortex afferents to the vibrissal motor cortex mimicked CS-related potentials growth, suggesting that the latter process was due to a learning-dependent potentiation of cortico-cortical synaptic inputs. This potentiation seemed to enhance the efficiency of cortical commands to whisker-pad intrinsic muscles, enabling the generation of acquired motor responses.     

Cognition-Oriented Treatments for Older Adults: a Systematic Overview of Systematic Reviews

Neuropsychology Review - Cognition-oriented treatments – commonly categorized as cognitive training, cognitive rehabilitation and cognitive stimulation – are promising approaches for...     

Unplanned pregnancy and risk of maternal depression: secondary data analysis from a prospective pregnancy cohort

Purpose: to evaluate the relationship between unplanned pregnancy (UP), a common problem in high and low income countries and maternal depression (MD). Methods: Secondary analysis of data from a prospective cohort study with pregnant women recruited from 10 primary care clinics of the public sector in São Paulo, Brazil. Participants were questioned about pregnancy intention at 20–30 weeks of gestation. The Self Report Questionnaire score >7 was used to evaluated the presence of depression during pregnancy and 11 months after childbirth. Four groups of MD were defined: never; antenatal only; postnatal only; persistent (both antenatal/postnatal). Multinomial logistic regression was used to assess the relationship between UP and MD, controlling for confounding. Results: Data were analysed for 701 at the postpartum period. Five hundred and sixty-two (67.8%) women did not plan the pregnancy. Women with UP had 2.5 more risk of being depressed during both assessments (during pregnancy and postpartum) when compared to women with a planned pregnancy (RR: 2.5; 95% CI: 1.47:4.30). In the adjusted models, women with UP were significantly more likely to have persistent depression (RR: 2.3; 95% CI: 1.2:4.3). Conclusion: UP is an independent risk factor for persistent depression, but not for postpartum depression     

Early language outcomes in Argentinean toddlers: Associations with home literacy,screen exposure and joint media engagement

This study aimed to analyse the contribution of mothers' home literacy beliefs and practices and the quantity and quality of screen media exposure on Argentinean toddler's language. In addition, we considered parent–child joint engagement, as well as adult scaffolding behaviours during the use of electronic devices. A total of 465 mothers of 18–36 months old children completed an online survey including: the MacArthur Bates CDI, home literacy, screen exposure, joint engagement and scaffolding questionnaires. We observed positive effects of literacy beliefs, PC times and verbal scaffolding on language outcomes. TV exposure contributed negatively to vocabulary and, along with educational content, to sentence use. Shared reading and screen media experiences can be an opportunity for language stimulation, provided there is dialogue and joint engagement. Passive screen exposure and inadequate content may be detrimental for toddlers' language outcomes, probably by displacement of socially significant interactions.