Cholesterol Modifies Classical Conditioning of the Rabbit (Oryctolagus cuniculus) Nictitating Membrane Response.

Cholesterol plays an important role in synapse formation, receptor function, and synaptic plasticity, and animal studies show that modifying cholesterol may improve learning and memory. Other data show that feeding animals cholesterol can induce beta amyloid accumulation. Rabbits (Oryctolagus cuniculus) fed 2% cholesterol for 8 weeks were given trace conditioning of the nictitating membrane response using a 100-ms tone, a 700-ms trace, and periorbital electrical stimulation or airpuff. Rabbits fed cholesterol showed significant facilitation of trace conditioning to airpuff and conditioning-specific reflex modification to periorbital electrical stimulation and airpuff. The cholesterol-fed rabbits had beta amyloid accumulation in the cortex, but little in the hippocampus. The data suggest cholesterol had facilitative effects that outweighed potential amnesic effects of cortical beta amyloid. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of a Corneal Anesthetic on Extinction of the Classically Conditioned Nictitating Membrane Response in the Rabbit (Oryctolagus cuniculus).

Rabbits (Oryctolagus cuniculus) were presented with 7 daily sessions of tone-alone training after conditioning. Before the beginning of each of the first 4 extinction sessions, an artificial tear solution or tetracaine hydrochloride was administered to the cornea of rabbits in the control group (n=6) and experimental group (n=1), respectively. There were no between-group differences in the percentage of conditioned responses between both groups. However, the amplitude of the conditioned response was notably reduced in the tetracaine group (M=0.40, SEM±0.216) relative to the control group (M=1.32, SEM ±0.639) early in extinction. Results seem to suggest that although motor output has been found to play an important role in extinction, corneal sensory feedback is not necessary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial Prefrontal Lesions and Pavlovian Eyeblink and Heart Rate Conditioning: Effects of Partial Reinforcement on Delay and Trace Conditioning in Rabbits (Oryctolagus cuniculus).

Effects of continuous (100%) versus partial (25%) reinforcement were studied on Pavlovian delay and trace eyeblink conditioning in rabbits (Oryctolagus cuniculus) with either lesions to the medial prefrontal cortex (mPFC) or sham lesions. Concomitant heart rate changes evoked by the conditioned stimulus were also assessed. Partial reinforcement retarded eyeblink conditioning in both the trace and delay paradigm, but this impairment was greater during trace conditioning and in rabbits with mPFC lesions. Accompanying conditioned stimulus-evoked heart rate slowing was attenuated under all conditions by the mPFC lesions, although this result was not always statistically significant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Conditioning During Amygdalar Inactivation on Training-Induced Neuronal Plasticity in the Medial Geniculate Nucleus and Cingulate Cortex in Rabbits (Oryctolagus cuniculus).

This study addressed the amygdala's role in avoidance conditioning in rabbits (Oryctolagus cuniculus). Intra-amygdalar muscimol infusion before 60 or 120 conditioning trials blocked training-induced neuronal activity (TIA) in the medial geniculate (MG) nucleus. One hundred twenty trials with muscimol blocked TIA permanently, during conditioning with muscimol and then later without muscimol; 60 trials with muscimol blocked TIA only when muscimol was present. Cingulate cortical TIA was blocked only when muscimol was present. Behavioral learning did not occur with muscimol, but later learning was facilitated (i.e., savings occurred) in rabbits initially given muscimol plus training. These results define the time period wherein amygdalar processes initiate TIA in the MG nucleus and suggest that distinct forms of amygdalar processes induce TIA in the MG nucleus and cingulate cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A New Model for Sexual Conditioning: The Ring Dove (Streptopelia risoria).

Sexual conditioning investigations have primarily used rats and domestic quail as subjects. Although much has been learned from such experiments, the relative simplicity of rat and quail reproductive behavior prohibits investigation of certain experimental questions about sexual conditioning. In contrast, the reproductive behavior of male and female ring doves (Streptopelia risoria) is complex, involving courtship, bonding, and parental care. In the present experiment, male ring doves that were presented with a visual conditioned stimulus paired with access to their pair-bonded mate (the unconditioned stimulus) showed sexual conditioned responding in the presence of the conditioned stimulus. These results represent the first evidence of sexual conditioning in ring doves and illustrate the potential of ring doves as a useful model for future sexual conditioning investigations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttraining lesions of the medial prefrontal cortex impair performance of Pavlovian eyeblink conditioning but have no effect on concomitant heart rate changes in rabbits (Oryctolagus cuniculus).

The medial prefrontal cortex (mPFC) plays a critical role in conditioned autonomic adjustments but is not involved in classically conditioned somatomotor responses unless the training conditions include reversal or trace conditioning. The studies showing these effects have all used pretraining lesions. The present study assessed the effects of posttraining lesions on eyeblink (EB) and heart rate (HR) conditioned responses (CRs) in both delay and trace conditioning paradigms in the rabbit (Oryctolagus cuniculus). Posttraining lesions lowered the percentage of EB CRs during retesting compared with pretesting levels for both delay and trace conditioning. Control lesions and pretraining lesions produced no significant effects during retesting. Posttraining lesions had no effect on the HR CR. These findings suggest that a critical mechanism in the mPFC is involved in retrieval of information during EB conditioning but that the mPFC integration of autonomic and somatomotor processes is not critical to this retrieval process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies of binaural detection in the rabbit (Oryctolagus cuniculus) with Pavlovian conditioning.

A Pavlovian conditioned eyeblink response in rabbits (Oryctolagus cuniculus) was used to study psychoacoustical phenomena previously demonstrated in human listeners and other animals. This article contains the results of a tone-in-noise detection study to examine 2 psychoacoustical phenomena in rabbit and in human listeners: (a) the binaural masking level difference (BMLD) and (b) differential performance across reproducible noise masker waveforms. The rabbits demonstrated a BMLD comparable in size to other species. Significant differences in performance across reproducible noise masker waveforms were seen in the rabbits. This performance was compared with the performance of human listeners using the same set of waveforms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Stimulus Selection in Eyelid Conditioning in the Rabbit (Oryctolagus cuniculus)": Erratum.

Reports an error in the original article by Perry S. Kinkaide (Journal of Comparative and Physiological Psychology, 1974[Jun], 86[6], 1132-1140). The lower portion of Figure 3 on page 1138 should have represented the last two conditions for Group T as Test AV and reTest AV. The last sentence of the caption should have been deleted. (The following abstract of this article originally appeared in record 1979-05368-001) Conducted 2 experiments, using a total of 24 female New Zealand white rabbits, in which a "visual" stimulus (V), either flashes or electrical stimulation of the optic chiasma, was reinforced in compound with a differentially reinforced (CS+) or nonreinforced (CS-) nonvisual stimulus. Visual stimulus control of conditioned eyeblink activity was acquired if V was reinforced in compound with CS- but was "blocked" when reinforced in compound with CS+. Both effects were demonstrable within Ss and were independent of the method of visual stimulation. Extinction and backward conditioning of chiasmic stimulation preceded retraining of 6 Ss. The establishment and blocking of visual stimulus control were again evident within Ss. The data are interpretable in terms of either attentional or associative theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex, Age, and Training Modulate Spatial Memory in the Rhesus Monkey (Macaca mulatta).

The authors tested 90 rhesus monkeys (Macaca mulatta) on a task of spatial memory, the spatial Delayed Recognition Span Test. The results showed that performance declined significantly with age, males had greater scores than females, and the rate of apparent decline with age was greater in males than in females. Both working and reference memory declined with age, but only working memory showed sex differences. The authors compared these data with that of 22 monkeys who were trained on a simpler version of the task before formal testing. Training had no effect on males but dramatically improved working memory in young females. The results confirm a male advantage in spatial working memory at a young age and confirm a greater decline with age in males than in females. It is important to note that prior training completely reverses the deficits of young females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuron Production, Neuron Number, and Structure Size Are Seasonally Stable in the Hippocampus of the Food-Storing Black-Capped Chickadee (Poecile atricapillus).

Neuronal recruitment in the black-capped chickadee (Poecile atricapillus) hippocampus occurs at a higher rate in the fall than at other times of the year. As a means of determining whether this increase in recruitment results from greater neuron production, chickadees were caught in the wild between October and March and injected with the cell-birth marker 5-bromo-2'-deoxyuridine. Two weeks later, birds were killed by overdose, and hippocampal neuron production, apoptosis, neuron number, and hippocampal volume were determined. Chickadees collected in October, November, January, February, and March did not differ in neuron production, apoptosis, hippocampal volume, or neuron number. These findings indicate that increases in neuronal recruitment in the chickadee hippocampus in the fall do not result from increased neuron production, but instead, enhanced survival of new neurons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial Ability and Home-Range Size: Examining the Relationship in Western Men and Women (Homo sapiens).

In mammals, spatial sex differences may have coevolved with sex differences in the size of home ranges. This study first evaluated whether, in keeping with most mammals and traditional human (Homo sapiens) societies, home ranges are larger in male than in female Westerners. Second, it established whether navigation patterns are associated with a broader set of spatial abilities in men than in women. Results showed that current male home ranges surpass female home ranges. Ranging was also positively correlated with achievement in tests of mental rotation, surface development, and location memory among men only, whereas it was associated with embedded figures scores in both sexes. Overall, these findings substantiate the adaptive role of several spatial sex differences in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory Control and Response Selection in Problem Solving: How Cotton-Top Tamarins (Saguinus oedipus) Overcome a Bias for Selecting the Larger Quantity of Food.

When presented with a choice between 1 and 3 pieces of food in a type of reversed contingency task, 4 cotton-top tamarins (Saguinus oedipus) consistently chose the 3 pieces of food and received nothing, even though the choice of 1 piece would have yielded 3. However, in a task in which the tamarins received the 1 piece of food when they chose it, all subjects learned to select 1 over 3. Thus, the tamarins' prior failure on the reversed contingency task did not result entirely from an inherent inability to suppress the prepotent response of reaching to the larger of 2 quantities of food. After the experience of selecting the smaller quantity and receiving it, all of the tamarins solved the version of the reversed contingency task that they failed initially. These results suggest that the tamarins' initial failure may have reflected a difficulty with selecting an alternative response option. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reorientation in a Two-Dimensional Environment: II. Do Pigeons (Columba livia) Encode the Featural and Geometric Properties of a Two-Dimensional Schematic of a Room?

Pigeons (Columba livia) searched for a hidden target area in images showing a schematic rectangular environment. The absolute position of the goal varied across trials but was constant relative to distinctive featural cues and geometric properties of the environment. Pigeons learned to use both of these properties to locate the goal. Transformation tests showed that pigeons could use either the color or shape of the features, but performance was better with color cues present. Pigeons could also use a single featural cue at an incorrect corner to distinguish between the correct corner and the geometrically equivalent corner; this indicates that they did not simply use the feature at the correct corner as a beacon. Interestingly, pigeons that were trained with features spontaneously encoded geometry. The encoded geometric information withstood vertical translations but not orientation transformations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrete quantity judgments in the great apes (Pan paniscus, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus): The effect of presenting whole sets versus item-by-item.

The authors examined quantity-based judgments for up to 10 items for simultaneous and sequential whole sets as well as for sequentially dropped items in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), bonobos (Pan paniscus), and orangutans (Pongo pygmaeus). In Experiment 1, subjects had to choose the larger of 2 quantities presented in 2 separate dishes either simultaneously or 1 dish after the other. Representatives of all species were capable of selecting the larger of 2 quantities in both conditions, even when the quantities were large and the numerical distance between them was small. In Experiment 2, subjects had to select between the same food quantities sequentially dropped into 2 opaque cups so that none of the quantities were ever viewed as a whole. The authors found some evidence (albeit weaker) that subjects were able to select the larger quantity of items. Furthermore, the authors found no performance breakdown with the inclusion of certain quantities. Instead, the ratio between quantities was the best performance predictor. The authors conclude that quantity-based judgments rely on an analogical system, not a discrete object file model or perceptual estimation mechanism, such as subitizing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)