The neurobiology of infant maternal odor learning

Infant rats must learn to identify their mother’s diet-dependent odor. Once learned, maternal odor controls pups’ approach to the mother, their social behavior and nipple attachment. Here we present a review of the research from four different laboratories, which suggests that neural and behavioral responses to the natural maternal odor and neonatal learned odors are similar. Together, these data indicate that pups have a unique learning circuit relying on the olfactory bulb for neural plasticity and on the hyperfunctioning noradrenergic locus coeruleus flooding the olfactory bulb with norepinephrine to support the neural changes. Another important factor making this system unique is the inability of the amygdala to become incorporated into the infant learning circuit. Thus, infant rats appear to be primed in early life to learn odors that will evoke approach responses supporting attachment to the caregiver.

Generalization of temporal order detection skill learning: two experimental studies of children with dyslexia

The objective of this study was to investigate the phenomenon of learning generalization of a specific skill of auditory temporal processing (temporal order detection) in children with dyslexia. The frequency order discrimination task was applied to children with dyslexia and its effect after training was analyzed in the same trained task and in a different task (duration order discrimination) involving the temporal order discrimination too. During study 1, one group of subjects with dyslexia (N = 12; mean age = 10.9 ± 1.4 years) was trained and compared to a group of untrained dyslexic children (N = 28; mean age = 10.4 ± 2.1 years). In study 2, the performance of a trained dyslexic group (N = 18; mean age = 10.1 ± 2.1 years) was compared at three different times: 2 months before training, at the beginning of training, and at the end of training. Training was carried out for 2 months using a computer program responsible for training frequency ordering skill. In study 1, the trained group showed significant improvement after training only for frequency ordering task compared to the untrained group (P < 0.001). In study 2, the children showed improvement in the last interval in both frequency ordering (P < 0.001) and duration ordering (P = 0.01) tasks. These results showed differences regarding the presence of learning generalization of temporal order detection, since there was generalization of learning in only one of the studies. The presence of methodological differences between the studies, as well as the relationship between trained task and evaluated tasks, are discussed.

Tipologia de erros de leitura de escolares brasileiros considerados bons leitores / Reading errors typology of Brazilian students considered good readers

BACKGROUND: assessment of oral reading. AIM: to characterize, according to the variables of public or private school and literacy, the types of errors in word reading presented by typical elementary/middle school students considered competent readers by their teachers. METHOD: participants of this study were 151 students with ages ranging between 8 and 12 years, from the 4th to the 7th grade of public and private schools. The students read a list of 38 words. The oral readings were transcribed and the errors analyzed according to their frequency. The frequency of errors was calculated based on the possibilities of errors presented by the used word list. RESULTS: the obtained results gave evidence to the errors presented by typical students of both public and private schools from all of the tested grades. There was a statistically significant progressive reduction in errors of orthographic decoding according to literacy (p<0.0001). Considering the groups, students from private schools presented fewer errors of global orthographic decoding when compared to students from public schools (p < 0.0001). CONCLUSION: the results suggest that reading errors are part of the learning process of orthographic decoding rules. These errors are progressively overcome with literacy. The domain of orthographic decoding independent of the context occurred more prematurely than that which is dependent of the grapheme context.

TEMA: avaliação da leitura oral. OBJETIVO: caracterizar, segundo as variáveis rede de ensino e escolaridade, os tipos de erro na leitura de palavras isoladas, apresentados por escolares típicos do ensino fundamental, considerados competentes por seus professores. MÉTODO: participaram da pesquisa 151 escolares com idade entre oito e doze anos, matriculados do quarto ao sétimo ano do ensino fundamental das redes pública e particular. Os escolares leram uma lista com 38 palavras. As leituras orais foram transcritas e os erros analisados, segundo a freqüência de erros cometidos calculada com base na possibilidade de erros oferecida pela lista apresentada. RESULTADOS: os resultados encontrados evidenciaram a presença de erros quando analisadas as leituras dos escolares típicos de ambas as redes de ensino e de todas as séries estudadas. Houve redução progressiva e estatisticamente significante dos erros de decodificação ortográfica em função da progressão da escolaridade (p < 0,0001). Considerando a rede de ensino, os escolares da rede particular apresentaram menor número de erros que os de escola pública quando comparado o desempenho na decodificação ortográfica global na prova de leitura de palavras (p < 0,0001). CONCLUSÃO: os resultados demonstraram que os erros de leitura fazem parte do aprendizado das regras de decodificação ortográfica e são superados, progressivamente, com o aumento da escolaridade. O domínio da decodificação da ortografia independente do contexto ocorreu mais precocemente que o da dependente do contexto grafêmico.

Plasticity in primary somatosensory cortex resulting from environmentally enriched stimulation and sensory discrimination training

We studied primary-somatosensory cortical plasticity due to selective stimulation of the sensory periphery by two procedures of active exploration in adult rats. Subjects, left with only three adjacent whiskers, were trained in a roughness discrimination task or maintained in a tactile enriched environment. Either training or enrichment produced 3-fold increases in the barrel cortex areas of behaviorally-engaged whisker representations, in their zones of overlap. While the overall areas of representation expanded dramatically, the domains of exclusive principal whisker responses were virtually identical in enriched vs normal rats and were significantly smaller than either group in roughness discrimination-trained rats. When animals were trained or exposed to enriched environments with the three whiskers arrayed in an are or row, very equivalent overlaps in representations were recorded across their greatly-enlarged whisker representation zones. This equivalence in distortion in these behavioral preparations is in contradistinction to the normal rat, where overlap is strongly biased only along rows, probably reflecting the establishment of different relations with the neighboring cortical columns. Overall, plasticity phenomena are argued to be consistent with the predictions of competitive Hebbian network plasticity.

Operant serial feature-positive conditional discrimination with composite features and different topography responses

In a serial feature-positive conditional discrimination procedure the properties of a target stimulus A are defined by the presence or not of a feature stimulus X preceding it. In the present experiment, composite features preceded targets associated with two different topography operant responses (right and left bar pressing); matching and non-matching-to-sample arrangements were also used. Five water-deprived Wistar rats were trained in 6 different trials: X-R arrow right Ar and X-L arrow right Al, in which X and A were same modality visual stimuli and the reinforcement was contingent to pressing either the right (r) or left (l) bar that had the light on during the feature (matching-to-sample); Y-R arrow right Bl and Y-L arrow right Br, in which Y and B were same modality auditory stimuli and the reinforcement was contingent to pressing the bar that had the light off during the feature (non-matching-to-sample); A- and B- alone. After 100 training sessions, the animals were submitted to transfer tests with the targets used plus a new one (auditory click). Average percentages of stimuli with a response were measured. Acquisition occurred completely only for Y-L arrow right Br+; however, complex associations were established along training. Transfer was not complete during the tests since concurrent effects of extinction and response generalization also occurred. Results suggest the use of both simple conditioning and configurational strategies, favoring the most recent theories of conditional discrimination learning. The implications of the use of complex arrangements for discussing these theories are considered.

Context and Pavlovian conditioning

Procedurally, learning has to occur in a context. Several lines of evidence suggest that contextual stimuli actively affect learning and expression of the conditional response. The experimental context can become associated with the unconditional stimulus (US), especially when the US is presented in a context in the absence of a discrete conditional stimulus (CS). Moreover, context can modulate CS-US associations. Finally, it appears that context can become associated with the CS when it is presented before the CS-US training. The purpose of the present paper is to review some of the relevant literature that considers the context as an important feature of Pavlovian conditioning and to discuss some of the main learning theories that incorporate the context into their theoretical framework. The paper starts by mentioning historical positions that considered context an important variable in conditioning and then describes how the approach to contextual conditioning changed with the modem study of Pavlovian conditioning. Various forms of measurement of context conditioning are presented and the associative strength attached to context in several experimental paradigms is examined. The possible functions that context may acquire during conditioning are pointed out and related to major learning theories. Moreover, the effect of certain neurological manipulations on context conditioning is presented and these results are discussed in terms of possible functions that the context might acquire during Pavlovian conditioning. It is concluded that contextual stimuli acquire different functions during normal conditioning. A procedure in which animals are exposed to an aversive US immediately after they are placed in the experimental context is suggested as a useful control for the study of context conditioning.

Operant discrimination learning in detelencephalated pigeons (Columba livia)

Operant discrimination learning was analyzed in pigeons after massive telencephalic lesions. Twenty-one pigeons were divided into the three groups: non-lesioned (N=6), sham-lesioned (N=5) and telencephalon lesioned (N=10). Lesion surgeries were carried out before any experimental training. Learning procedures were run in the same sequence for all groups and under a food deprivation of 80 percent of the ad libitum weight. Successive discrimination was programmed by the alternation of red and yellow lights in the right key of a standard operant chamber: the red key was correlated with extinction. Sessions were run until steady-state key peck rates were obtained. The following results demonstrate discrimination learning required a larger number of sessions for lesioned pigeons (P<0.05). They showed increased response rates in red (26.43 +/- 2.59) and yellow (11.17 +/- 2.86) components...

Effect of nutritional and environmental restrictions on discrimination learning behaviour of juvenile rats.

Effects of nutritional and environmental restrictions on discrimination learning in a single unit black/white T-maze were studied in albino rats. Nutritional restrictions were imposed by 25 and 50% dietary restriction and environmental restrictions were given for 3 and 6 weeks. Both the restrictions were imposed at 46th day after birth. Long-term (6 weeks) environmental restriction significantly impaired the original and reversal discrimination learning, however, short-term (3 weeks) restriction had no effect. Nutritional (dietary) restrictions, on the other hand, had no effect on both learning performances. Interaction between these two variables was also statistically insignificant.