F. Robert Treichler

Discrete-Trial Training Techniques and Stimulus Variables

Publisher Summary This chapter presents the factors known to govern the efficiency with which the nonhuman primates learn in situations that involve a trial-by-trial approach. The variables of interest are the nature of the cues, their modes of presentation to the subject, and the spatiotemporal relations of cues to responses and rewards. There now is a most substantial body of research related to this group of variables, and it has been shown that very powerful effects can be produced by their manipulation. The chapter also presents methods that involve the use of discriminanda and presents experiments in which the visual cues are of a fairly complex nature.

Concurrent conditional discrimination tests of transitive inference by macaque monkeys: list linking.

Processing of serial information was assessed by training six macaques on a five-item list of objects arranged into the four conditional pairs, A-B+, B-C+, C-D+, and D-E+. An analogous list (F through J) was similarly trained. Subsequently, both lists were linked by training on E-F+, a pair that provided adjacent elements from each list. Then, all unique and trained object pairs from both lists were presented as a test. Results indicated that the objects were retained as a single, linearly organized list with choice accuracy directly related to interitem distance between paired objects. A second experiment explored the consequences of incidence of conflicting information on list organization. In both experiments, selections depended on representational processes and supported the view that monkeys and pigeons retain serial lists in qualitatively different ways.Processing of serial information was assessed by training six macaques on a five-item list of objects arranged into the four conditional pairs, A-B+, B-C+, C-D+, and D-E+. An analogous list (F through J) was similarly trained. Subsequently, both lists were linked by training on E-F+, a pair that provided adjacent elements from each list. Then, all unique and trained object pairs from both lists were presented as a test. Results indicated that the objects were retained as a single, linearly organized list with choice accuracy directly related to interitem distance between paired objects. A second experiment explored the consequences of incidence of conflicting information on list organization. In both experiments, selections depended on representational processes and supported the view that monkeys and pigeons retain serial lists in qualitatively different ways.

Linking of serially ordered lists by macaque monkeys (Macaca mulatta): List position influences

Five monkeys (Macaca mulatta) were trained on 2 sets of 3 5-item serially ordered lists. Then, each set was either linked or not in a counterbalanced, within-subject design. Linking entailed training on the 2 pairs that ordered the 3 5-item lists into a single overall 15-item series. Choices on novel pairings after linking conditions attempted to define the unique contributions of knowledge of within-list ordinal position and between-lists link training. With linkage, the series was immediately treated as a 15-item ordered list. Without linkage, choices reflected list positions from initial learning, but continued testing with directional reward yielded gradual ordering into a 15-item list. Apparently, monkeys remembered and used initial list-position information, but linkage allowed inference of an integrated serial relationship among items. Results supported primate list memory as an organizational process.

An analysis of von Economo neurons in the cerebral cortex of cetaceans, artiodactyls, and perissodactyls.

Von Economo neurons (VENs) are specialized projection neurons with a characteristic spindle-shaped soma and thick basal and apical dendrites. VENs have been described in restricted cortical regions, with their most frequent appearance in layers III and V of the anterior cingulate cortex, anterior insula, and frontopolar cortex of humans, great apes, macaque monkeys, elephants, and some cetaceans. Recently, a ubiquitous distribution of VENs was reported in various cortical areas in the pygmy hippopotamus, one of the closest living relatives of cetaceans. That finding suggested that VENs might not be unique to only a few species that possess enlarged brains. In the present analysis, we assessed the phylogenetic distribution of VENs within species representative of the superordinal clade that includes cetartiodactyls and perissodactyls, as well as afrotherians. In addition, the distribution of fork cells that are often found in close proximity to VENs was also assessed. Nissl-stained sections from the frontal pole, anterior cingulate cortex, anterior insula, and occipital pole of bowhead whale, cow, sheep, deer, horse, pig, rock hyrax, and human were examined using stereologic methods to quantify VENs and fork cells within layer V of all four cortical regions. VENs and fork cells were found in each of the species examined here with species-specific differences in distributions and densities. The present results demonstrated that VENs and fork cells were not restricted to highly encephalized or socially complex species, and their repeated emergence among distantly related species seems to represent convergent evolution of specialized pyramidal neurons. The widespread phylogenetic presence of VENs and fork cells indicates that these neuron morphologies readily emerged in response to selective forces,whose variety and nature are yet to be identified.

Training requirements and retention characteristics of serial list organization by macaque monkeys

Abstract This work evaluated the prospect that organizational accounts of the retention of list information by monkeys might be an artifact of familiarity with conditional relationships. Seven sophisticated macaques were trained on four five-item lists. Each acquisition selectively excluded one of the internal conditional pairs of the typical four-problem sequence (AB,BC,CD,DE) that defines a five-item serially ordered list. Then, all possible novel pairings and the trained pairs appeared together in a test. After this, the previously omitted pair was trained and animals were retested. On all tasks, initial tests revealed little organization and much intersubject variability of characteristic choice strategies, but subsequent inclusion of all four conditional pairs always yielded organized serial choice. On both the four-problem tests and in a later retention, errors were directly related to interitem distance between the objects paired on test trials. These results helped to specify the conditions required for demonstration of non-human primate analogs of transitivity, and showed that even sophisticated monkeys organize information in retention only if they know all interitem relationships.

Two-stage frontal lesion influences upon severity of delayed-response deficit

Seven groups of monkeys (total n = 33) underwent one- or two-stage bilateral aspirative removal of frontal cortical areas after acquisition of 5-sec spatial delayed response. Some animals were tested for retention as normals, and all were eventually tested under some postoperative condition. Relative to normal retention, one-stage dorsolateral removals produced severe deficits. Two-stage removals, divided into zones above or below the principal sulcus, generally yielded lesser severity, but this property was also influenced by the order and, to a lesser degree, the extent of these lesions. Some potential bases for the consequences of serial removals were discussed.

The influence of delay interval on severity of the spatial alternation deficit in frontal monkeys.

Summary Five normal and five dorsolaterally frontal-lesioned rhesus macaques were tested in an automated apparatus on non-correctional spatial delayed alternation using ITI’s of .75, 2, 3, and 4 sec. in ascending and descending order. Six hundred trials were presented at each delay, and while performance improved within testing at the various delays, there were significant influences of both delays and lesions. Further, although the lesion influence was generally more marked at the longer delays, the rapidity of adjustment to the presence of delay might have been greater for normals than for frontals. It was concluded that frontal alternation deficit is highly dependent upon task variables.

Serial list combination by monkeys (Macaca mulatta): test cues and linking

This investigation assessed prospective bases of non-human primate cognitive operations that support serial list memory. Four macaques learned 3-, 5-item ordered lists of objects (as two-choice problems) and then either did or did not (in a within-subject design) receive training on pairs that linked the three original lists into a 15-item serial order. Next, subjects experienced selective exposure trials on object pairs that either maintained or contrasted to the serial position relationships seen during original learning. Subsequent comprehensive tests assessed the interactive effects of linking and exposure conditions on choosing in accord with a combined 15-item serial order. Linking readily induced monkeys to merge lists into a 15-item order, but restricting early exposure to pairs with the same positional relationships as original training slowed, but did not prevent, list combination. Exposure to positional relationships congruent with the combined (15-item) list and different from those of original 5-item training aided both expression of the linking effect and acquisition after no link training. Thus, list linking facilitated serial reorganization by inducing release from error derived from memory for prior learned positional relationships. The task was recommended as a prospective evaluator of continuity of cognitive processes among species.

Long-term retention of concurrent discriminations by monkeys

Five rhesus macaques were measured over a 10-month period on the acquisition and retention of 124 concurrent, simultaneous, two-choice object discriminations. Distinctive properties of acquisition by naive subjects, retention after various intervening training conditions, and additions of new problems to an existing store of information were all issues investigated in various phases of the program of research. The pervasive characteristic observed in all behavioral measures was proficient performance in both acquisition and retention despite large numbers of problems or long retention intervals. Some potential bases and implications of such extensive and durable memory capacities were considered.

Effects of age and ingestive experience on air-drinking behavior in the rat

Thirsty rats 18, 23, 30, or 40 days old received a brief air puff when they licked at a tube. Air-drinking occurred even in 18 day Ss, and increased significantly as a function of age. In a second experiment, rat pups reared without access to a water bottle were similarly tested for air-drinking behavior at 18 or 23 days. Operant level of tube licking was determined for litter mates. Significantly greater tube licking occurred in air reinforced Ss, indicating that prior experience with drinking water from a tube was not a necessary condition for the establishment of air-drinking behavior.