Compensatory Hippocampal Neurogenesis in the Absence of Cognitive Impairment Following Experimental Hippocampectomy in Adult Rats.

Temporal lobe epilepsy (TLE) is the commonest type of focal epilepsy in adult humans, and hippocampal sclerosis (HS) is the main pathological finding in this type of epilepsy. In refractory TLE, patients are indicated for unilateral resection of the affected hippocampus by a surgical procedure called hippocampectomy which generally does not cause any cognitive impairment. Once adult hippocampus is a region of endogenous neurogenesis, even in elderly people, we have hypothesized that a compensatory increase in hippocampal neurogenesis might occur in the remaining hippocampus after unilateral hippocampectomy. To test this hypothesis, we performed unilateral hippocampectomy in adult Wistar rats, which were perfused at 15 (G15) and 30 (G30) days post-surgery. Eighteen Wistar rats were randomly distributed in the following experimental groups: control (no surgery, N = 6), G15 (N = 6), and G30 (N = 6). Adjacent cortex and hippocampus of the left hemisphere were completely removed. Behavioral procedures were performed to address possible cognitive impairments. Brains were collected and fixed from animals belonging to all experimental groups. Gross histopathology was performed using thionine staining. Neuroblasts and mature neurons were immunolabeled using anti-doublecortin (DCX) and anti-NeuN antibodies, respectively. Numbers of DCX and NeuN positive cells were quantified for all experimental groups. Animals submitted to hippocampectomy did not present any cognitive impairment as evaluated by eight-arm radial maze behavioral test. The remaining hippocampus presented a higher number of DCX positive cells compared to control (p < 0.001, ANOVA-Tukey) at both G15 and G30. A higher number of NeuN positive cells were present in the granular layer of dentate gyrus at G30 compared to control and G15 (p < 0.001, ANOVA-Tukey). The data suggest that unilateral hippocampectomy induces compensatory neurogenic effect in the contralateral hippocampus. This may underlie the reported absence of significant cognitive impairment and parallels the findings in human patients submitted to unilateral hippocampectomy to treat refractory TLE.

Generalized Identity Matching to Sample after Multiple-Exemplar Training in Capuchin Monkeys.

A multiple-exemplar identity matching-to-sample baseline was established to encourage development of generalized IDMTS performances in three adult male capuchins. Mask (blank comparison) or Shuffled S- procedures were used to promote select (sample-S+) control in baseline relations and to assess stimulus control relations in generalized IDMTS tests. The IDMTS baseline comprised eight 3-stimulus sets or four 4-stimulus sets. Probe trials with new stimulus sets were substituted for baseline sets in successive testing sessions and subsequently converted to new baseline relations. All monkeys exhibited high accuracy on generalized IDMTS tests. A monkey who was given the Mask procedure in training and tests showed generalized IDMTS with select relations predominating. Two monkeys who were given training and testing with the Shuffled S- procedure performed somewhat better on Shuffled S- IDMTS test trials than on test trials that contained non-shuffled test IDMTS trials thus suggesting that exclusion of familiar nonmatching comparison stimuli from baseline in Shuffled S-test trials contributed to the higher accuracy scores with the former procedures. Development of select relations appeared to be a positive predictor of development of generalized IDMTS.

Expansão de repertório de relações arbitrárias em Sapajus sp. via exclusão / Expanding arbitrary relations repertoire by exclusion in Sapajus sp

O procedimento de exclusão pode expandir repertório relacional arbitrário de crianças, em condições de aprendizagem sem erros. Embora a escolha por exclusão esteja presente em diversas espécies não humanas, ela nem sempre resulta na aprendizagem de novas relações. O objetivo deste trabalho foi verificar a escolha por exclusão em um macaco-prego e a aquisição das novas relações arbitrárias como um resultado do contexto de exclusão. O sujeito apresentava um repertório de 5 relações arbitrárias A-B e suas simétricas B-A adquirido em estudo prévio, em um procedimento de pareamento ao modelo com atraso, envolvendo cinco ou mais escolhas como comparações. Neste estudo, usando o procedimento de pareamento ao modelo com duas escolhas, novas relações arbitrárias A-C foram introduzidas, usan-do-se estímulos B como S-, para verificar exclusão. O sujeito respondeu corretamente nas tentativas de exclusão excluindo o estímulo B e escolhendo o estímulo C. A aprendizagem das novas relações A-C foi avaliada em tentativas compostas apenas por comparações do Conjunto C, e o sujeito respondeu incorretamente nessas tentativas. Um treino com comparação vazia visando estabelecer controle por seleção e rejeição nas relações A-C não foi efetivo em gerar relações de controle por seleção. Em estudos futuros serão usadas mais de duas escolhas por tentativa no treino A-C, em contexto de exclusão, visando obter a aprendizagem das novas relações.

The procedure of exclusion may expand children's repertoire of arbitrary relations resulting in errorless learning, but although choice by exclusion has been reported in a variety of species, it is not followed by learning of the new relations. The objective of this paper was to verify if capuchins would choose by exclusion, and if they subsequently would acquire the new arbitrary relations as outcome of exclusion. The capuchin monkey had previously acquired a repertory of 5 A-B and their symmetric B-A arbitrary relations in delayed-matching to-sample (DMTS) with five or more choices. Using a two-choice DMTS, new A-C relations were introduced using non paired B stimuli as S- to verify exclusion. The subject excluded non paired B and chose the new C stimuli. However, performance was disrupted in trials with only C stimuli as comparisons; training with a blank stimulus substituting either comparison in turns was ineffective. Further studies using trials with more than two comparison stimuli will verify arbitrary relations' learning in capuchins after exclusion.

Expansão de repertório de relações arbitrárias em Sapajus sp. via exclusão

O procedimento de exclusão pode expandir repertório relacional arbitrário de crianças, em condições de aprendizagem sem erros. Embora a escolha por exclusão esteja presente em diversas espécies não humanas, ela nem sempre resulta na aprendizagem de novas relações. O objetivo deste trabalho foi verificar a escolha por exclusão em um macaco-prego e a aquisição das novas relações arbitrárias como um resultado do contexto de exclusão. O sujeito apresentava um repertório de 5 relações arbitrárias A-B e suas simétricas B-A adquirido em estudo prévio, em um procedimento de pareamento ao modelo com atraso, envolvendo cinco ou mais escolhas como comparações. Neste estudo, usando o procedimento de pareamento ao modelo com duas escolhas, novas relações arbitrárias A-C foram introduzidas, usan-do-se estímulos B como S-, para verificar exclusão. O sujeito respondeu corretamente nas tentativas de exclusão excluindo o estímulo B e escolhendo o estímulo C. A aprendizagem das novas relações A-C foi avaliada em tentativas compostas apenas por comparações do Conjunto C, e o sujeito respondeu incorretamente nessas tentativas. Um treino com comparação vazia visando estabelecer controle por seleção e rejeição nas relações A-C não foi efetivo em gerar relações de controle por seleção. Em estudos futuros serão usadas mais de duas escolhas por tentativa no treino A-C, em contexto de exclusão, visando obter a aprendizagem das novas relações.(AU)

The procedure of exclusion may expand children's repertoire of arbitrary relations resulting in errorless learning, but although choice by exclusion has been reported in a variety of species, it is not followed by learning of the new relations. The objective of this paper was to verify if capuchins would choose by exclusion, and if they subsequently would acquire the new arbitrary relations as outcome of exclusion. The capuchin monkey had previously acquired a repertory of 5 A-B and their symmetric B-A arbitrary relations in delayed-matching to-sample (DMTS) with five or more choices. Using a two-choice DMTS, new A-C relations were introduced using non paired B stimuli as S- to verify exclusion. The subject excluded non paired B and chose the new C stimuli. However, performance was disrupted in trials with only C stimuli as comparisons; training with a blank stimulus substituting either comparison in turns was ineffective. Further studies using trials with more than two comparison stimuli will verify arbitrary relations' learning in capuchins after exclusion.(AU)

Restricted Stimulus Control in Stimulus Control Shaping with a Capuchin Monkey.

Teaching the first instances of arbitrary matching to sample to nonhumans can prove difficult and time consuming. Stimulus control relations may develop that differ from those intended by the experimenter - even when stimulus control shaping procedures are used. This paper reports efforts to identify sources of shaping program failure with a capuchin monkey. Procedures began with a baseline of identity matching. During subsequent shaping trials, compound comparison stimuli had two components - one identical to and another different from the sample. The identical component was eliminated gradually by removing portions across trials (i.e., subtracting stimulus elements). The monkey performed accurately throughout shaping. At a late stage in the program, probe tests were conducted: (1) arbitrary matching trials that had all elements of the identical comparison removed and (2) other trials that included residual elements. During the test, the monkey performed at low levels on the former trials and higher levels on the latter. These results suggested that higher accuracy was due merely to continued control by the residual elements: the target arbitrary matching relations had not been learned. Thus, it appears that procedures that gradually transform identity matching baselines into arbitrary matching can fail by inadvertently shaping restricted control by residual elements. Subsequent probes at the end of the shaping series showed a successful transfer of stimulus control from identity to arbitrary matching after further programming steps apparently overcame the restricted stimulus control.

Sample stimulus control shaping and restricted stimulus control in capuchin monkeys: a methodological note.

This paper reports use of sample stimulus control shaping procedures to teach arbitrary matching-to-sample to 2 capuchin monkeys (Cebus apella). The procedures started with identity matching-to-sample. During shaping, stimulus features of the sample were altered gradually, rendering samples and comparisons increasingly physically dissimilar. The objective was to transform identity matching into arbitrary matching (i.e., matching not based on common physical features of the sample and comparison stimuli). Experiment 1 used a two-comparison procedure. The shaping procedure was ultimately effective, but occasional high error rates at certain program steps inspired a follow-up study. Experiment 2 used the same basic approach, but with a three-comparison matching task. During shaping, the monkey performed accurately until the final steps of the program. Subsequent experimentation tested the hypothesis that the decrease in accuracy was due to restricted stimulus control by sample stimulus features that had not yet been changed in the shaping program. Results were consistent with this hypothesis, thus suggesting a new approach that may transform the sample stimulus control shaping procedure from a sometimes useful laboratory tool to a more general approach to teaching the first instance of arbitrary matching performances to participants who show protracted difficulties in learning such performances.