Serotonergic Modulation of the Excitation/Inhibition Balance in the Visual Cortex.

Serotonergic neurons constitute one of the main systems of neuromodulators, whose diffuse projections regulate the functions of the cerebral cortex. Serotonin (5-HT) is known to play a crucial role in the differential modulation of cortical activity related to behavioral contexts. Some features of the 5-HT signaling organization suggest its possible participation as a modulator of activity-dependent synaptic changes during the critical period of the primary visual cortex (V1). Cells of the serotonergic system are among the first neurons to differentiate and operate. During postnatal development, ramifications from raphe nuclei become massively distributed in the visual cortical area, remarkably increasing the availability of 5-HT for the regulation of excitatory and inhibitory synaptic activity. A substantial amount of evidence has demonstrated that synaptic plasticity at pyramidal neurons of the superficial layers of V1 critically depends on a fine regulation of the balance between excitation and inhibition (E/I). 5-HT could therefore play an important role in controlling this balance, providing the appropriate excitability conditions that favor synaptic modifications. In order to explore this possibility, the present work used in vitro intracellular electrophysiological recording techniques to study the effects of 5-HT on the E/I balance of V1 layer 2/3 neurons, during the critical period. Serotonergic action on the E/I balance has been analyzed on spontaneous activity, evoked synaptic responses, and long-term depression (LTD). Our results pointed out that the predominant action of 5-HT implies a reduction in the E/I balance. 5-HT promoted LTD at excitatory synapses while blocking it at inhibitory synaptic sites, thus shifting the Hebbian alterations of synaptic strength towards lower levels of E/I balance.

Cáncer de mama y su relación con el manejo de las emociones y el estrés / Breast cancer and its relationship with the management of emotions and stress

Resumen

Introducción: las emociones son breves alteraciones del ánimo que se presentan de manera abrupta y con manifestaciones físicas. Los sentimientos son las percepciones de cómo se siente el cuerpo en medio de una emoción. Los sentimientos y las emociones se modifican según la sociedad, la cultura, el contexto y se moldean de acuerdo con la personalidad.

Objetivo: identificar la relación entre las emociones-sentimientos y el estrés con el cáncer de mama (CaMa) y cuál es el nivel de evidencia de las investigaciones publicadas.

Metodología: se hizo una búsqueda sistemática con los siguientes algoritmos: a) cáncer de mama AND etiología AND emociones, b) cáncer de mama AND etiología emocional, c) cáncer de mama AND etiología AND estrés, en español e inglés; en bases de datos: BVS regional, Medline, SciELO, CINAHL, Cochrane.

Resultados: se encontraron artículos que sugieren que la etiología del cáncer de mama puede relacionarse con situaciones estresantes vividas en la infancia, represión de sentimientos, tensión crónica, depresión, ansiedad y estrés.

Conclusiones: hay coincidencias en cuanto a que los problemas vividos durante la niñez pueden influir en la vulnerabilidad a desarrollar diversas enfermedades, incluido el cáncer de mama en la edad adulta.

Abstract

Introduction: Emotions are rapid mood swings which occur abruptly and with physical manifestations. Feelings are the perceptions of how the body feels in the midst of an emotion. Feelings and emotions are modified according to society, culture, context, and are shaped according to personality.

Objective: To identify the relationship between emotions-feelings and stress, with breast cancer and what is the level of evidence of published research.

Methods: It was carried out a systematic search with the following algorithms: a) breast cancer AND etiology AND emotions, b) breast cancer AND emotional etiology, c) breast cancer AND etiology AND stress, in Spanish and English, in regional BVS, Medline, SciELO, CINAHL and Cochrane databases.

Results: We found articles that suggest that the etiology of breast cancer can be related to stressful situations experienced in childhood, repression of feelings, chronic tension, depression, anxiety and stress.

Conclusions: There are coincidences in which it is stated that the problems experienced during childhood may trigger the vulnerability to develop various diseases, including breast cancer in adulthood.

Daily maternal separations during stress hyporesponsive period decrease the thresholds of panic-like behaviors to electrical stimulation of the dorsal periaqueductal gray of the adult rat.

The present study examined whether early life maternal separation (MS), a model of childhood separation anxiety, predisposes to panic at adulthood. For this purpose, male pups were submitted to 3-h daily maternal separations along postnatal (PN) days of either the 'stress hyporesponsive period' (SHRP) from PN4 to PN14 (MS11) or throughout lactation from PN2 to PN21 (MS20). Pups were further reunited to conscious (CM) or anesthetized (AM) mothers to assess the effect of mother-pup interaction upon reunion. Controls were subjected to brief handling (15 s) once a day throughout lactation (BH20). As adults (PN60), rats were tested for the thresholds to evoke panic-like behaviors upon electrical stimulation of dorsal periaqueductal gray matter and exposed to an elevated plus-maze, an open-field, a forced swim and a sucrose preference test. A factor analysis was also performed to gain insight into the meaning of behavioral tests. MS11-CM rather than MS20-CM rats showed enhanced panic responses and reductions in both swimming and sucrose preference. Panic facilitations were less intense in mother-neglected rats. Although MS did not affect anxiety, MS11-AM showed robust reductions of defecation in an open-field. Factor analysis singled out anxiety, hedonia, exploration, coping and gut activity. Although sucrose preference and coping loaded on separate factors, appetite (adult weight) correlated with active coping in both forced swim and open-field (central area exploration). Concluding, whereas 3h-daily maternal separations during SHRP increased rat's susceptibility to experimental panic attacks, separations throughout lactation had no effects on panic and enhanced active coping.

Métodos experimentales de estudio de la percepción temprana del habla / Métodos experimentais de estudo da percepção precoce da fala / Experimental study techniques for the early speech perception

El estudio de la percepción temprana del habla surgió a comienzos de la década de los setenta, pero solo se desarrolló plenamente diez años después, debido a la aparición y adaptación de nuevos métodos empíricos y herramientas tecnológicas. En este artículo se presenta una revisión de los métodos experimentales que pueden ser utilizados para el estudio de la percepción del habla en niños menores de un año. También se refieren algunas de las conclusiones teóricas más relevantes que se han alcanzado gracias a su aplicación. Se pretende brindar un panorama delestado metodológico y teórico del estudio de la percepción del lenguaje hablado durante el primer año de vida...

The early speech perception began to be studied at the beginning of the 1970s, but only developed fully ten years later due to the appearance and adaptation of new empirical methods and technological tools. The article reviews the experimental methods that can be used to study early speech perception in children under the age of one, and discusses some of the most relevant theoretical conclusions reached thanks to their application. The objective is to provide an overview of the methodological and theoreticalsituation of the study of speech perception during the first year of life...

O estudo da percepção precoce da fala surgiu no começo da década de 1970, mas só se desenvolveu plenamente dez anos depois, devido ao aparecimento e adaptação de novos métodos empíricos e ferramentas tecnológicas. Neste artigo, apresenta-se uma revisão dos métodos experimentais que podem ser utilizados para o estudo da percepção da fala em crianças menores de um ano. Também se referem algumas das conclusões teóricas mais relevantes que se alcançaram graças à sua aplicação. Pretende-se oferecer um panorama do estado metodológico e teórico do estudo da percepção da linguagem falada durante o primeiro ano de vida...

Nutritional restriction of omega-3 fatty acids alters topographical fine tuning and leads to a delay in the critical period in the rodent visual system.

The development and maturation of sensory systems depends on the correct pattern of connections which occurs during a critical period when axonal elimination and synaptic plasticity are involved in the formation of topographical maps. Among the mechanisms involved in synaptic stabilization, essential fatty acids (EFAs), available only through diet, appear as precursors of signaling molecules involved in modulation of gene expression and neurotransmitter release. Omega-3 fatty acids, such as docosahexaenoic acid (DHA), are considered EFAs and are accumulated in the brain during fetal period and neonatal development. In this study, we demonstrated the effect of omega-3/DHA nutritional restriction in the long-term stabilization of connections in the visual system. Female rats were fed 5 weeks before mating with either a control (soy oil) or a restricted (coconut oil) diet. Litters were fed until postnatal day 13 (PND13), PND28 or PND42 with the same diets when they received an intraocular injection of HRP. Another group received a single retinal lesion at the temporal periphery at PND21. Omega-3 restriction induced an increase in the optical density in the superficial layers of the SC, as a result of axonal sprouting outside the main terminal zones. This effect was observed throughout the SGS, including the ventral and intermediate sub-layers at PND13 and also at PND28 and PND42. The quantification of optical densities strongly suggests a delay in axonal elimination in the omega3(-) groups. The supplementation with fish oil (DHA) was able to completely reverse the abnormal expansion of the retinocollicular projection. The same pattern of expanded terminal fields was also observed in the ipsilateral retinogeniculate pathway. The critical period window was studied in lesion experiments in either control or omega-3/DHA restricted groups. DHA restriction induced an increased sprouting of intact, ipsilateral axons at the deafferented region of the superior colliculus compared to the control group, revealing an abnormal extension of the critical period. Finally, in omega-3 restricted group we observed in the collicular visual layers normal levels of GAP-43 with decreased levels of its phosphorylated form, p-GAP-43, consistent with a reduction in synaptic stabilization. The data indicate, therefore, that chronic dietary restriction of omega-3 results in a reduction in DHA levels which delays axonal elimination and critical period closure, interfering with the maintenance of terminal fields in the visual system.

Periodic maternal separation decreases hippocampal neurogenesis without affecting basal corticosterone during the stress hyporesponsive period, but alters HPA axis and coping behavior in adulthood.

Although not directly evaluated, the early rise of glucocorticoid (GC) levels, as occur after exposure to adverse early life experience, are assumed to affect hippocampal ontogeny by altering the hippocampus negative feedback on adult HPA axis. To test whether hippocampal ontogeny is affected by early exposure to stress we estimated the survival of recently formed hippocampal granule cells in rat pups subjected to periodic maternal separation (180 min/day; MS180) from postnatal days (PND) 1 to 14. Accordingly, MS180 pups injected with bromodeoxyuridine (BrdU, 50 mg/kg, ip) at PND 5 showed decreased density of doublecortin (DCX) positive BrdU-labeled cells at PND 15. MS180 and AFR pups showed similar corticosterone (CORT) basal levels between PND 3 and 12, whereas adult MS180 rats presented with higher CORT levels than AFR adults. Nonetheless, both AFR and MS180 pups and adults showed similar transient increments of CORT levels in response to stress. In addition, MS180 had no effect on the adult anxiety-like behavior evaluated in the elevated plus maze, but evoked a passive coping strategy in the forced swimming test. The data show that the decrease in hippocampal neurogenesis is an early onset phenomenon, and suggests that adverse experiences alter hippocampal ontogeny without chronic elevation of GC levels.

Effect of nonlinguistic auditory training on phonological and reading skills.

OBJECTIVE: To analyze the effect of nonverbal auditory training on reading and phonological awareness tasks in children with dyslexia and the effect of age in relation to post-training learning considering the ages from 7 to 14. METHODS: In experiment 1, one group with dyslexia (total = 12) was trained and compared with a group of untrained dyslexic subjects (total = 28). In experiment 2, the performance of the trained dyslexic group (total = 18) was compared at three different moments: 2 months before, at the beginning, and at the end of training. Training was carried out for 2 months using a computer program responsible for training discrimination skills. RESULTS: The group receiving nonverbal auditory training demonstrated significant improvements (mainly for the group from 7 to 10 years old), not only in the nonverbal auditory skills trained (p < 0.001), but also in phonological awareness syllable tasks (synthesis, segmentation, manipulation and syllable transposition) in experiment 1 (p < 0.003), and phonemic tasks (p < 0.001) and text reading (p < 0.001) in experiment 2. CONCLUSION: The results suggest a link between verbal and nonverbal skills, in addition to corroborating studies regarding the existence of a critical learning period.

Hormonal acceleration of song development illuminates motor control mechanism in canaries.

In songbirds, the ontogeny of singing behavior shows strong parallels with human speech learning. As in humans, development of learned vocal behavior requires exposure to an acoustic model of species-typical vocalizations, and, subsequently, a sensorimotor practice period after which the vocalization is produced in a stereotyped manner. This requires mastering motor instructions driving the vocal organ and the respiratory system. Recently, it was shown that, in the case of canaries (Serinus canaria), the diverse syllables, constituting the song, are generated with air sac pressure patterns with characteristic shapes, remarkably, those belonging to a very specific mathematical family. Here, we treated juvenile canaries with testosterone at the onset of the sensorimotor practice period. This hormone exposure accelerated the development of song into stereotyped adultlike song. After 20 days of testosterone treatment, subsyringeal air sac pressure patterns of song resembled those produced by adults, while those of untreated control birds of the same age did not. Detailed temporal structure and modulation patterns emerged rapidly with testosterone treatment, and all previously identified categories of adult song were observed. This research shows that the known effect of testosterone on the neural circuits gives rise to the stereotyped categories of respiratory motor gestures. Extensive practice of these motor patterns during the sensorimotor phase is not required for their expression.

Maternal stress induces long-lasting Purkinje cell developmental impairments in mouse offspring.

A number of clinical studies suggest that prenatal stress can be a risk factor in the development of various psychopathologies, including schizophrenia, depression, anxiety, and autism. The cerebellar vermis has been shown to be involved in most of these disorders. In the present study, therefore, we evaluate the effect of maternal stress on long-term alterations in vermal Purkinje cell morphology. Furthermore, to discern whether these structural changes are associated with anxious behavior, the exploratory drive in the elevated plus maze was evaluated. Pregnant CF-1 mice were randomly assigned to control (n = 14) or stressed (n = 16) groups. Dams of the stressed group were subjected to restraint stress between gestational days 14 and 20, while control pregnant dams remained undisturbed in their home cages. Anxious behavior and Purkinje cell morphology were evaluated in three ontogenetic stages: postweaning, adolescence, and adulthood. Although exploratory behavior in the elevated plus maze was unaffected by prenatal stress, the Purkinje cell morphology showed a transient period of abnormal growth (at postweaning and juvenile stages) followed by dramatic dendritic atrophy in adulthood. In conclusion, prenatal stress induced significant long-lasting bimodal changes in the morphology of vermal Purkinje cells. These structural alterations, however, were not accompanied by anxious behaviors in the elevated plus maze.

High ethanol dose during early adolescence induces locomotor activation and increases subsequent ethanol intake during late adolescence.

Adolescent initiation of ethanol consumption is associated with subsequent heightened probability of ethanol use disorders. The present study examined the relationship between motivational sensitivity to ethanol initiation in adolescent rats and later ethanol intake. Experiment 1 determined that ethanol induces locomotor activation shortly after administration but not if tested at a later post-administration interval. In Experiment 2, adolescent rats were assessed for ethanol-induced locomotor activation on postnatal Day 28. These animals were then evaluated for ethanol-mediated conditioned taste aversion and underwent a 16-day-long ethanol intake protocol. Ethanol-mediated aversive effects were unrelated to ethanol locomotor stimulation or subsequent ethanol consumption patterns. Ethanol intake during late adolescence was greatest in animals initiated to ethanol earliest at postnatal Day 28. Females that were more sensitive to ethanol's locomotor-activating effects showed a transient increase in ethanol self-administration. Blood ethanol concentrations during initiation were not related to ethanol-induced locomotor activation. Adolescent rats appeared sensitive to the locomotor-stimulatory effects of ethanol. Even brief ethanol exposure during adolescence may promote later ethanol intake.

Desarrollo psicológico del niño sordo. Momentos críticos / Psychological development of deaf children. Critical moments

Se describen los momentos más críticos del desarrollo psicológico del niño sordo. Sucesivamente se aborda: el establecimiento de relaciones psicológicas precoces, la orientación lingüística del niño y sus consecuencias cognitivas, el encuentro con los escrito, las elecciones de identidad en la adolescencia, y el ingreso a la vida profesional.

Nous décrovins les moments les plus critiques du développement psychologique de l’ enfant sourd. Sont successivement abordés: l’ etablissement des relations psychologiques précoces, l’ orientation linguistique de l’ enfant et ses consequences cognitive, la recontre avec l’ écrit, les choix identitaries à l’ adolescence, et la rentré dans la vie professionnelle.

The most critical moments of the psychological development of the deaf child are described. The following topics are discussed: establishment of psychological precocious relations, the linguistic orientation of the child and its cognitive consequences, the encounter with the written text, the choices of identity in the adolescence, and the beginning of the professional life.

Language promotes false-belief understanding: evidence from learners of a new sign language.

Developmental studies have identified a strong correlation in the timing of language development and false-belief understanding. However, the nature of this relationship remains unresolved. Does language promote false-belief understanding, or does it merely facilitate development that could occur independently, albeit on a delayed timescale? We examined language development and false-belief understanding in deaf learners of an emerging sign language in Nicaragua. The use of mental-state vocabulary and performance on a low-verbal false-belief task were assessed, over 2 years, in adult and adolescent users of Nicaraguan Sign Language. Results show that those adults who acquired a nascent form of the language during childhood produce few mental-state signs and fail to exhibit false-belief understanding. Furthermore, those whose language developed over the period of the study correspondingly developed in false-belief understanding. Thus, language learning, over and above social experience, drives the development of a mature theory of mind.

A detailed analysis of open-field habituation and behavioral and neurochemical antidepressant-like effects in postweaning enriched rats.

Our previous work has shown that male Sprague-Dawley rats reared in social isolation, standard housing and environmental enrichment differ in their spontaneous open-field activity and in some neurobehavioral depressive-like parameters. Here, we extended this evidence by using a shorter postweaning rearing period (1 month) and including additional evaluations. First, in order to obtain a better characterization of the exploratory strategies among rearing conditions we analyzed in detail the spontaneous activity at the first minute and during the 10-min session. Second, we asked whether the changes in open-field activity were related with basal anxiety levels in the elevated plus-maze. Third, behavior in the forced-swimming test was analyzed and afterward, the tissue levels of hippocampal norepinephrine and serotonin were assessed. The possible relationship between neurotransmitters and forced-swimming behavior were explored through correlation analyses. We found that rearing conditions (i) differed on locomotor habituation and on sensory-motor exploration at the first minute and during the 10-min session without modifying the plus-maze behavior; (ii) affected differentially the grooming time, its sequential components, and the relationship between grooming and locomotor parameters; (iii) modified forced-swimming behavior and the hippocampal concentration of norepinephrine, serotonin, and its turnover; and (iv) produced different correlation patterns between both neurotransmitters and forced-swimming behaviors. Overall, environmental enrichment accelerated open-field habituation and led to behavioral and neurochemical antidepressant-like effects. In contract, isolation rearing strongly impaired habituation and simple information processing, but showed marginal effects on depressive-like behavior and on hippocampal neurochemistry. The current results suggest that differential rearing is not only a useful procedure to study behavioral plasticity or rigidity in response to early experience, but also to modeling some developmental protective or risk factors underlying depressive disorders.

Neonatal maternal separation affects endocrine and metabolic stress responses to ether exposure but not to restraint exposure in adult rats.

We investigated prolactin secretion and metabolic changes in stress response in adult male rats submitted to periodic maternal separation (MS; 180 min/day) at 2 weeks of life. Restraint and ether exposure were randomly performed when the animals were 10-12 weeks of age. Restraint exposure: the animals were placed into plastic tubes (21 cm long, 4.5 cm diameter) for 20 min. Ether exposure: the rats were exposed to ether for 10 min. Atrial cannulation for blood sampling was performed through the jugular vein 5 days before the experiments. In both protocols, blood samples were taken immediately before (0), and 5, 15 and 20 min after the beginning of stress exposure. Ours results showed attenuated endocrine and metabolic responses to ether exposure in the maternal separation (MS) group compared to the control group. The measured metabolic parameters, plasma glucose, prolactin, lactate, and insulin secretion, were 32%, 55%, 41%, 73% lower (P < 0.01), respectively, in MS than in control animals. On the other hand, the endocrine and metabolic stress responses to restraint exposure were not affected by maternal separation. There was no difference between the MS and the control groups in any of the parameters studied. Our data demonstrated that early life experiences affect the hormonal systems beyond the hypothalamic-pituitary-adrenal axis, such as the central neuronal pathways, and their activities related to hormonal and metabolic responses to stress in adulthood. More importantly, these modifications were specific, but dependent on stress situation affecting mainly the circuitry related to the stress response to ether exposure.

Long-term exposure to environmental enrichment since youth prevents recognition memory decline and increases synaptic plasticity markers in aging.

Aging-associated brain changes include functional alterations that are usually related with memory decline. Epidemiological reports show that a physically and intellectually active life provides a protective effect on this decline and delays the onset of several neurodegenerative diseases. The cellular mechanisms behind the behavioral-based therapies, such as environmental enrichment (EE) exposure, as a method for alleviating age-related memory impairments, are still unknown. Although some reports have shown the benefits of EE exposure in cognitive outcomes in old mice and in animals with experimental neurodegenerative conditions, the effects of lifelong animal exposure to EE have not been explored in detail. In the present work we tested in a rat model the effects of intermittent lifelong exposure since youth to EE on behavioral performance, object recognition memory and anxiety level, as well as on some morphological and biochemical markers of brain plasticity such as hippocampal neurogenesis, synaptophysin content and synaptic morphology. We found that environmental factors have a positive impact on short-memory preservation, as well as on the maintenance of synapses and in the increase in number of new generated neurons within the hippocampus during aging.

Nicaraguan Sign Language and Theory of Mind: the issue of critical periods and abilities.

BACKGROUND: Previous studies in the literature report that deaf individuals who experience late access to language perform poorly on false belief tests of Theory of Mind (ToM) compared with age-matched deaf and hearing controls exposed to language early. METHODS: A group of 22 deaf Nicaraguans (aged 7 to 39 years) who learned Nicaraguan Sign Language (ISN) at different ages were tested on a false belief and a nonverbal cartoon retell task designed to elicit talk about the contents of character's mental states. RESULTS: Access to sign language by 10 years of age with possible advantages in language fluency was a strong predictor of performance on both the false belief task and mental state narrative task. However, a comparison of performance on the two tests indicated that children and adults who learned sign after the age of 10 were still able to demonstrate a more general ability to use mental state expressions in narratives. Results are discussed in terms of late access to language and critical periods for the parallel development of Theory of Mind and language. CONCLUSIONS: The findings point to age 10 years as a crucial period when lack of language exposure can lead to long-lasting deficits in false belief abilities. Late exposure to sign language does not, however, rule out all aspects of the ability to consider others' mental states. This paper also highlights the need to take into consideration a variety of communication responses when evaluating deaf children's ToM reasoning.

Different dopamine D1 and D2 receptors expression after motor activity in the striatal critical period.

Circling training during rat striatum postnatal critical period (PN30 to 37 days) induces a life-lasting co-reduction of muscarinic acetylcholine receptors (mAChR) and dopamine D2 receptors (D2R) binding. Here, we evaluated the expression of D1R and D2R under similar experimental conditions. Trained rats showed a decrease of 40% in D2R binding sites (p<0.01) and of 45% in the D2R mRNA expression which involve short (p<0.05) and long (p<0.01) isoforms. In contrast, D1R binding sites nor its mRNA expression levels were affected by training, indicating a differential synaptic refinement during this ontogenetically fixed period.

[Neuronal plasticity and the scientific bases of neurohabilitation]. / Plasticidad neuronal y las bases científicas de la neurohabilitación.

INTRODUCTION: The validity of methods of neurological habilitation and rehabilitation has long been questioned by a large proportion of the medical profession. This sceptical attitude was partly due to lack of scientific confirmation of the theories on which methods of habilitation-rehabilitation were based, and the absence of reliable studies of the follow-up of such treatment, designed on strict statistical criteria. DEVELOPMENT: Advances in recent years in understanding neuronal plasticity have permitted better understanding of the mechanisms which come into action following brain damage and the factors which help or hinder recovery, and the various possible patterns involved in the reorganization of neuronal circuits. A review of studies of animal experiments, and recently in humans (using techniques of functional imaging and magnetic exploration) show that by sensory stimulation and exercise it is possible to modify the structure and function of the brain, after its somatotopical organization, increase synaptic connections, influence the orientation of the dendrites, number of receptors etc. There are critical periods in development during which these plastic properties of the brain become fully developed and subsequently the possibility of recovery is considerably less. CONCLUSIONS: The findings of neurobiological investigation show that there are good prospects for the recovery of a damaged nervous system by means of embryonic neurone implantation, axon bridges, transference of genes producing trophic factor, enzymes, neurotransmitters etc. In any case, therapeutic intervention and rehabilitation teaching continue to be useful for the functional recovery of these patients.

Períodos críticos ou sensíveis: revistar um tema polêmico à luz da investigaçäo empírica / Critical or sensitive periods: revisting a polemic theme in the light of the empiric investigation

O objetivo deste trabalho é analisar o conceito de período crítico à luz da investigaçäo empírica disponível. Em primeiro lugar apresenta-se o conceito de período crítico e faz-se uma resenha histórica acerca da sua evoluçäo. Em seguida analise-se o problema da determinaçäo dos períodos críticos sendo apresentado os resultados das poucas investigaçöes realizadas nesta temática no âmbito das aptidöes motoras. Os resultados destas investigaçöes evidenciam alguma contradiçäo nas suas conclusöes. Posteriormente é analisada a questäo da treinabilidade e da sua dependência genética. Conclui-se: a) que existe uma grande falta de estudos empíricos que abordem a questäo dos períodos críticos ou sensíveis, näo estando confirmada ou reprovada a idéia da sua existência no treino de aptidöes motoras e aprendizagem de habilidades; b) o grau de treinabilidade é influenciado pelo genótipo, verificando-se uma forte interaçäo genótipo X envolvimento, ocasionando uma grande variaçäo inter-individual no grau de sensibilidade ao treino e instruçäo