Transverse Patterning Research Articles

Impaired transverse patterning in human amnesia is a special case of impaired memory for two-choice discrimination tasks.

Three amnesic patients with damage limited to the hippocampal formation, a severely amnesic patient with extensive medial temporal lobe damage, and 9 controls were tested on the transverse patterning problem (A + B-, B + C-, and C + A-) and also on 2 control problems. One of the control problems was matched to the transverse patterning problem with respect to the number of pairwise decisions that were required. The 2nd control problem was matched to the transverse patterning problem with respect to the number of trials needed by controls to learn the task. The amnesic patients were impaired at solving both the transverse patterning problem and the control problems. The findings suggest that impaired learning of the transverse patterning problem by amnesic patients derives from their general impairment in declarative memory, which affects performance on most 2-choice discrimination tasks.

Impaired transverse patterning in human amnesia is a special case of impaired memory for two-choice discrimination tasks.

Three amnesic patients with damage limited to the hippocampal formation, a severely amnesic patient with extensive medial temporal lobe damage, and 9 controls were tested on the transverse patterning problem (A + B-, B + C-, and C + A-) and also on 2 control problems. One of the control problems was matched to the transverse patterning problem with respect to the number of pairwise decisions that were required. The 2nd control problem was matched to the transverse patterning problem with respect to the number of trials needed by controls to learn the task. The amnesic patients were impaired at solving both the transverse patterning problem and the control problems. The findings suggest that impaired learning of the transverse patterning problem by amnesic patients derives from their general impairment in declarative memory, which affects performance on most 2-choice discrimination tasks.

A neural network solution to the transverse patterning problem depends on repetition of the input code.

Using computer simulations, this paper investigates how input codes affect a minimal computational model of the hippocampal region CA3. Because encoding context seems to be a function of the hippocampus, we have studied problems that require learning context for their solution. Here we study a hippocampally dependent, configural learning problem called transverse patterning. Previously, we showed that the network does not produce long local context codings when the sequential input patterns are orthogonal, and it fails to solve many context-dependent problems in such situations. Here we show that this need not be the case if we assume that the input changes more slowly than a processing interval. Stuttering, i.e., repeating inputs, allows the network to create long local context firings even for orthogonal inputs. With these long local context firings, the network is able to solve the transverse patterning problem. Without stuttering, transverse patterning is not learned. Because stuttering is so useful, we investigate the relationship between the stuttering repetition length and relative context length in a simple, idealized sequence prediction problem. The relative context length, defined as the average length of the local context codes divided by the stuttering length, interacts with activity levels and has an optimal stuttering repetition length. Moreover, the increase in average context length can reach this maximum without loss of relative capacity. Finally, we note that stuttering is an example of maintained or introduced redundancy that can improve neural computations.

Regional pattern of retinoid X receptor-alpha gene expression in the central nervous system of the chicken embryo and its up-regulation by exposure to 9-cis retinoic acid.

We have investigated the expression of the retinoid X receptor-alpha (RXRalpha) gene in the developing chicken embryo by using nonradioactive wholemount in situ hybridization. At the earliest stage of development examined (stage 9; Hamburger and Hamilton [1951] J. Morphol. 88:49-92), we detect RXRalpha transcripts in a stretch of neuroepithelium corresponding roughly to the presumptive caudal hindbrain. Upon formation of the rhombomeres at stage 12, a strongly RXRalpha-positive region extends from a sharp rostral limit at the boundary between rhombomeres 6 and 7 caudad to at least the level of somite 9. This pattern of highest expression continues at least until stage 22 but with some variability in the caudal extent. A lower level of expression extends throughout the spinal cord. Transverse sections show that RXRalpha transcripts are expressed in a gradient, with the highest levels near the roof plate and decreasing toward the floor plate. At later stages, the level of expression is highest in the proliferative ventricular zone. However, at reduced levels, RXRalpha transcripts are also detectable in the mantle zone as well as outside the developing central nervous system, for example, in the neural crest and the limb buds. Nine-cis-retinoic acid up-regulates RXRalpha transcripts at stages 19.5-22.0 within a few hours, augmenting but not expanding the expression pattern. Northern blots demonstrate the potential expression of multiple RXRalpha isoforms in the central nervous system at posthatch stages. These results implicate the RXRalpha receptor in both rostrocaudal and transverse patterning of the neural tube.

Configural learning in humans: The transverse patterning problem

Most learning theorists concur that some sort of configural representation system is required for animals to solve certain compound discriminations. Transverse patterning (A+ vs. B−, B+ vs. C−, C+ vs. A−) is one example of a problem that requires a configurai solution. It has been reported in the past that adult humans are unable to solve this problem (Berch & Israel, 1971; Franks, 1976). We investigated the generality of these reports. Moreover, we examined whether a stepwise approach to training this problem would facilitate learning and at what stage in training subjects adopt a configurai strategy. We found that college-aged adults had little difficulty solving the transverse patterning problem, and that their learning was greatly facilitated by using the stepwise approach described by Alvarado and Rudy (1989). Moreover, we found that subjects seem to adopt a configural strategy when faced with ambiguous stimulus pairs even when an elemental strategy would suffice. These results provide insight into how humans solve configurai problems and also suggest some direct tests of the role of the hippocampus in configural associations.

Losing their configural mind. Amnesic patients fail on transverse patterning.

A configural theory of human amnesia is proposed. The theory predicts that amnesic patients will exhibit selective deficits on tasks that normal subjects perform by learning new configurations of stimulus elements. This prediction is supported by results for four amnesic patients who learned a nonconfigural control task but failed to learn the configural transverse patterning task even after extensive practice. Matched normal subjects easily learned both tasks. The theory provides unique and viable accounts of the central results in the human amnesia literature. Relations between the configural approach and other theories are discussed.

Fornix Lesions Can Facilitate Acquisition of the Transverse Patterning Task: A Challenge for “Configural” Theories of Hippocampal Function

Configural theories of hippocampal function predict that hippocampal dysfunction should impair acquisition of the transverse patterning task, which involves the concurrent solution of three discrimination problems: A+ versus B-; B+ versus C-; and C+ versus A-. The present study tested this prediction in rats using computer-graphic stimuli presented on a touchscreen. Experiment 1 assessed the effects of fornix lesions when the three problems were introduced sequentially (phase 1: A+ vs B-; phase 2: A+ vs B-, B+ vs C-; phase 3: A+ vs B-, B+ vs C-, C+ vs A-). Fornix lesions significantly facilitated acquisition of the complete transverse patterning task (phase 3) but had no effect on the number of sessions or errors required to attain criterion during phase 1 or phase 2. In experiment 2, in which all three problems were presented concurrently from the outset of training, fornix-lesioned animals outperformed control animals during the seventh block of acquisition trials and were not impaired during any stage of acquisition. Importantly, these same animals were significantly impaired on two allocentric spatial tasks: T-maze alternation (experiments 1 and 2) and the Morris Swim Task (experiment 1). These results contradict the predictions of configural theories of hippocampal function and cast doubt on the popular notion that spatial learning is a special case of configural learning.

The hippocampus and transverse patterning guided by olfactory cues.

Normal rats and rats with hippocampal system damage were trained on a novel, olfactory version of the transverse-patterning task that involved the concurrent learning and continued performance of 3 partially ambiguous discrimination problems (A+B-, B+C-, C+A-). Animals with lesions of the fornix or perirhinal-entorhinal cortex acquired at least as rapidly as normal rats these problems presented in sequential blocks of trials involving the same stimulus pair. All groups also performed well on an initial test session when the order of stimulus pair presentations was randomized. Normal rats continued to discriminate appropriately in additional testing sessions with trials presented in random order. By contrast, both groups with hippocampal system damage performed poorly in continued random-order testing. These results extend the generality of the deficit in transverse patterning to the olfactory modality and demonstrate that the deficit is equivalent in magnitude after fornix or perirhinal-entorhinal damage. Findings also suggest that the transverse-patterning problem can be acquired transiently without critical hippocampal involvement, although continued performance relies on hippocampal function.

The hippocampus and transverse patterning guided by olfactory cues.

The hippocampus and transverse patterning guided by olfactory cues.

Transverse patterning in pigeons

Pigeons were trained to choose between colored lights (A, B, C, and D), first in a two-pair ambiguouscue problem (A+B−, B+C−), and then, with all colors nondifferentially reinforced, in a three-pair loop problem (A+B−, B+C−, C+A−) followed by a four-pair loop problem (A+B−, B+D−, D+C−, C+A−). Systematic efforts were made to simulate the data with a variety of models incorporating one or another of three conceptions of stimulus compounding prominent in the literature on compound conditioning. One conception is that the components of a compound stimulus are altered by interaction; the second is that they are not altered, but only supplemented with a new (compound-unique) component generated in the interaction; and the third is that the components entirely disappear in a configurational transformation. The ambiguous-cue data could be simulated accurately with each of the models, but the loop data with none of them. A convincing explanation of performance in loop problems remains to be found.

Transverse patterning in pigeons

The ability of pigeons to form configural stimulus representations was assessed in two operant discrimination experiments. In Experiment 1 the transverse patterning problem of Spence (1952) was trained. In Phase 1, subjects had to choose stimulus A on A + B — trials; B + C — trials were added in Phase 2. In Phase 3, the first two pairs were combined with C + A — trials. The success of the subjects was simulated by a model assuming that elemental and configural stimulus representations coexist in a stable proportion, even in the phases of the experiment which do not require configural stimulus representations for successful solution. Experiment 2 replicated the first two phases of Experiment 1, but trained A + C — in Phase 3. Comparison of the results of this experiment with simulations of the model showed that elemental and configural stimulus representations coexisted in similar proportions as in Experiment 1, even though they were not necessary for successful task solution.

Observation of dihedral transverse patterning of Gaussian beams in nonlinear optics.

We present experimental evidence that the spontaneous transverse filamentation of a laser beam back reflected onto a thin Kerr optical medium can be strongly affected by the actual boundary conditions, namely the Gaussian shape of the beam. As the filament spacing is made to increase by moving the feedback mirror, well-known hexagonal patterns no longer grow up but rather the laser spot breaks up into lower dihedral symmetry patterns, such as pentagonal, rhombic, or triangular ones, in very good agreement with previous numerical predictions. Further increasing the laser intensity after the symmetry breaking leads to secondary bifurcations. The multistability, itineracy, and turbulence of those structures were also observed.

The effect of age on children's learning of problems that require a configural association solution

Elemental associations permit subjects to solve problems when the significance of the relevant stimulus elements are consistent from trial to trial but do not allow subjects to solve problems that require them to construct and use representations of stimulus conjunctions or configurations to guide their behavior. Recent research with brain-damaged and developing animals has led several theorists to propose that elemental and configural associations depend on different neural systems. Some evidence suggests that changes in children's learning that occur when they are about 4.5 years old may be partially due to developmental differences in access to the elemental and configural association systems. Two experiments are reported that support this hypothesis. Children at least 4.5 years old were able to solve the transverse patterning problem and a conditional discrimination, two problems that require configural association solutions. Younger children did not solve these problems but were able to solve problems constructed from the same stimulus materials that permitted an elemental association solution. These results suggest that children may not gain access to the configural association system until they are about 4.5 years old and support the hypothesis that the configural association system depends on different, later developing neural structures than does the elemental association system.

The effects of setting similarity on children's learning of the transverse patterning problem

A group of 15 fourth-graders were given training on the transverse patterning problem, a task consisting of three different geometric forms presented in pairs. Three other groups of 15 fourth-graders each received training on problems containing the same geometric forms, along with either one (color or size) or two (color and size) additional nonspatial dimensions varying among the settings comprising the different cue-cue patterns. Contrary to a prediction derived from Croll's (1967) extension of Spiker's (1963) theory of discrimination learning, none of the Ss solved the basic transverse patterning problem, nor was there any improvement in performance on this problem after 90 trials. Consistent with predictions derived from Spiker's theory, it was found that the addition of one nonspatial dimersion resulted in solution, and that the greater the number of nonspatial dimensions present, the better the learning.

Solution of the transverse patterning problem: Response to cue-cue relations

The transverse patterning problem was studied in adult human Ss. As hypothesized, the addition of a nonspatial dimension varying among the settings comprising the cue-cue patterns decreased the difficulty of this discrimination task. Contrary to Spence (1952), a number of Ss solved the problem by means of responding to the cue-cue patterns, even though the additional nonspatial dimension permitted solution on the basis of a less complex type of pattern.