Journal of comparative and physiological psychology最新文献

Investigation of and habituation to novel stimuli are part of exploratory behavior of rodents. They are necessary for assessing the environment in seeking food and sexual partners and in avoiding predators. Male and female gerbils were tested in the stimulus-elicited investigation paradigm in order to address several questions on three issues: (a) Gerbils initially showed preferences for odors of strange male bedding and for odors of home cage bedding and then habituated. There was no preference between these two odors, although they could be discriminated. The complex odor stimulus elicited more response than any of the components tested. (b) Memory of an object or of an odor was demonstrated up to 4 wk later. (c) Sensory deprivation by blinding, anosmizing, or removing somatosensation of the upper snout made only small differences in investigation. The removal of any two of these sensory inputs produced more interference with the response, but all of the gerbils investigated the stimulus. It is concluded that attention to novelty and habituation after repeated exposure are very robust behaviors and are mediated through multiple sensory channels.

The reinforcing strengths of foods were assessed in rhesus monkeys before and after bilateral radio-frequency lesions of the lateral amygdala (n = 4), basolateral amygdala (n = 4), and total amygdala (n = 3). None of these lesions altered preoperative preferences between three highly palatable foods. Moreover, the lesions had no discernible effect on the animals' responses to different food rewards as measured by a progressive ratio schedule, although performance on this schedule proved sensitive to the size and type of food reward and to the degree of deprivation. The results suggest that amygdalectomy leaves a normal appreciation of at least this one class of rewards, foods. The dietary changes typically seen after amygdalectomy, such as meat eating, which were also observed in the same animals, probably reflect a loss of neophobia.

Rhesus monkeys discriminated between two color-differentiated stimuli presented on a screen only when they fixated the center of the screen. The stimuli were presented 8 degrees, 20 degrees, or 32 degrees from the screen's center, for 2 sec or 100 msec, a duration too brief to permit their fixation. Performance declined when the response sites, located either centrally (8 degrees eccentricity) or peripherally (32 degrees eccentricity), were separated from the stimuli, whether they were presented for 2 sec or 100 msec. These findings suggest that the stimulus-response separation effect is due to selective attention to the response sites and not to fixating them during stimulus presentation. Following superior colliculus lesions, the monkeys were impaired in discriminating between peripheral stimuli, but only when they responded centrally. This deficit was not due to (a) a failure to fixate the stimuli, for it occurred when the stimuli were 100 msec or 2 sec or (b) reduced sensory capacities, for it disappeared when the subjects responded peripherally. This deficit may reflect deficient attentional shifts from the response sites to the stimuli.

Four studies were conducted to delineate potential neural processes involved in retention of a peripherally induced postural asymmetry. In the first experiment, dorsal and ventral spinal root section following varying intervals of stimulation successfully abolished peripherally induced hindlimb asymmetry. Experiment 2 revealed that 50 min of ventral root stimulation, in the absence of central connection, was not effective in producing asymmetry persistence. In an attempt to more closely delineate the time parameters involved in peripherally induced asymmetry retention, Experiment 3 was conducted. Asymmetry was found to consistently outlast a spinal transection if 40 min of stimulation was given. Finally, possible modulatory higher brain center influences on the retention processes were demonstrated in Experiment 4. Asymmetry persistence was consistently observed in animals that received 10, 20, 30, 40, or 50 min of hindlimb stimulation if 50 min were allowed to elapse between the onset of stimulation and spinal section. These results, when coupled with the findings of earlier studies, suggest an active involvement of spinal reflex centers in the fixation process. In addition, these studies indicate that the manner in which reflex activity is altered is not crucial as long as underlying time parameters are adhered to. Finally, the present studies demonstrate that higher center influences can modulate retention of a postural asymmetry in a complex manner.

Newborn rabbits show behavioral and physiological thermoregulatory responses within the first hours of life. Although the mother prepares a nest for her young, she does not stay with them. The hairless immature young survive by huddling together in the nest. In this study, ambient temperature had a powerful influence on the behavior of newborn rabbits, and, providing they were warm, they did not huddle. The rabbits were studied over the first 10 days of life during which time their fur grows rapidly and their body weight nearly trebles. As each day passed, their preferred environmental temperature fell. In these observations smell and contact with littermates did not appear to have a major effect.

A conditioned emotional response (CER) paradigm was presented to two groups of rats during intracranial self-stimulation (ICSS). One group bar pressed for medial forebrain bundle (MFB) stimulation reward; the other group bar pressed for septal stimulation reward. The MFB ICSS was found to be suppressed by the CER procedure, but this procedure failed to suppress septal ICSS. This difference between the two sites was found only when both MFB and septal ICSS current intensities were available at their optimal levels. When ICSS current intensities were lowered to either threshold or medium level, both groups exhibited the CER suppression effect. The animals were also tested for a possible analgesic effect produced by the ICSS. The MFB stimulation was found to produce some degree of analgesia, but septal stimulation failed to produce any analgesic effect. Thus, the possibility that the attenuation of the CER suppression effect in the septal group was due to analgesia was excluded. The difference in MFB and septal ICSS behavior during the presentation of the aversive stimulus suggested a possible qualitative distinction between the reward functions of these two sites, and a possible fear-reduction property of the septal area.

One-day-old rats learned aversions to a novel taste paired with lithium-induced distress and to a tactile stimulus paired with brief electric shocks. However, aversions did not develop when taste was paired with shock or when the tactile stimulus was paired with lithium treatment. The aversions occurred only when lithium treatment immediately followed taste exposure and when shock was concurrent with exposure to the tactile stimulus. These findings indicate that selective associations in aversion learning are mediated by innate mechanisms that govern conditioning in the absence of extensive ontogenetic experience. The present research also shows that selective associations are sufficient for the occurrence of long-delay learning.

Eye blinks were conditioned to either the visual or nonvisual element of a compound conditioned stimulus. The visual element consisted of a series of electrical pulses to the optic chiasma, and the averaged evoked potentials (AEPs) produced by this stimulus were recorded in the dorsal lateral geniculate nucleus and the visual cortex. The initial surface positive component of the cortical AEP was enhanced only when the eye blinks were conditioned to the visual stimulus, an effect that cannot be attributed to nonspecific mechanisms. The "postsynaptic" component of the geniculate AEP was also enhanced, but this occurred regardless of whether the eye blinks were conditioned to the visual or nonvisual stimulus, an effect that appears to be entirely nonspecific. Data from recovery cycles indicate that this enhancement effect cannot be attributed to an inhibition of inhibitory interneurons in the lateral geniculate nucleus.

A sham-feeding preparation utilizing rhesus monkeys was employed to investigate the anatomical site of origin of satiety signals in the gastrointestinal tract. A series of experiments in which food was diverted from the stomach, the small intestine, or both demonstrated that (a) food acting at the pregastric level is not sufficient to produce normal-sized meals, (b) the accumulation of food in the small intestine is necessary to produce normal-sized meals, and (c) a potent preabsorptive or postabsorptive satiety signal originates at the intestinal level. This unidentified satiety signal is sufficient to elicit satiety, can be dissociated from gastric emptying, and does not require the presence of gastric distention to operate.

Kittens with neonatal lesions of the marginal and posterolateral gyri, along with unoperated controls, were reared either in an enriched environment or in laboratory cages. Kittens with lesions were inferior to controls at learning mazes and at discriminating forms and gratings, whether they were raised in enriched or impoverished conditions. Enrichment did not facilitate form or grating discrimination by either normal or operated cats, although such experience facilitated maze learning by both groups. It is concluded that early enrichment of sensorimotor experience was probably not the cause of the complete sparing of pattern vision after neonatal damage of the visual cortex reported in earlier studies. Discussion centers on task variables and completeness of the lesions as reasons for sparing of vision.