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Plasma catecholamine responses to acute motion stress in laboratory rats.

Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in adult male Fischer 344 (F-344) laboratory rats exposed to acute motion stress. Two days prior to testing, rats were prepared with chronic tail artery catheters to permit remote sampling of blood from conscious, freely behaving animals. Animals remained in their home cages during the entire testing protocol. After collection of basal blood samples, cages were rotated at 45 revolutions per minute for a 10-minute period each hour for 5 consecutive hours. Additional blood samples were collected immediately after each of the 10-minute rotation stress sessions. Plasma levels of NE remained unchanged from baseline immediately following each of the rotation stress sessions. In contrast, plasma EPI increased significantly above baseline levels following each of the 5 rotation stress sessions. These data indicate that rotation stress provides a selective activation of epinephrine-containing adrenal chromaffin cells as reflected in an increase in plasma EPI but not NE. This stress model could prove valuable in examining the physiological and behavioral consequences of adrenal EPI release in freely behaving animals without the confounding effects of increases in circulating norepinephrine.

Adrenal Medulla↗

Visual-spatial functions persist following temporal and posterior parietal cortex lesions in rat.

Adult rats were prepared with either posterior parietal, temporal, or sham neocortical lesions. Gross kinetic functions and equilibrium were assessed on alternate days for 12 days following surgery by placing the animal on an elevated rod (3.5 cm diameter) oriented 20 degrees to horizontal and rating locomotor functions. Although all groups improved with experience and time postsurgery, rats with posterior parietal lesions exhibited a greater kinetic disturbance throughout the testing period. After a 3-week recovery period, the animals were trained on a visual-spatial task in which a visual stimulus located at the choice point cued whether the escape platform was located in the left or right arm of a T-maze. Animals were trained at a rate of 20 trials per day until a criterion of 18 correct responses in a series of 20 trials was observed. This task differed from that used in a similar previous study in this laboratory (1) in that stimulus saliency was increased and rats were punished for errors by confinement to the incorrect alley for 15 s when errors were made. All rats learned the task, and although there were subtle differences in the rate of acquisition between the groups, there were no gross differences on any of several measures of learning and performance. It is concluded that, under appropriate conditions, rats with injuries in these posterior association regions can learn and perform a task requiring the execution of different spatial responses on the basis of visual landmark cues that are spatially discontiguous from the escape site.

Animals↗

Motion-induced aversions during and after recovery from olfactory nerve section in mice.

Bilaterally nerve-sectioned male albino mice were given access to a novel food (almond) and then body rotated for 50 min. Two days later the mice were given a second access to almond. The procedures were repeated after recovery of olfactory function. Mice formed a presumably taste-mediated aversion while anosmic and a second flavor-mediated aversion (to the same food) after the return of olfactory function. Rotation control subjects formed only the standard flavor aversion subsequent to the first pairing of novel food and motion. It appears that olfaction is required for recognition of a food as novel.

Animals↗

Learning of leg position by cockroaches in response to light.

Learning by the cockroach Periplaneta americana was studied using an electronic device that turns off a light in response to leg position. Training and testing were modeled on the Horridge procedure, with the position of a leg of one cockroach (P) controlling stimulation of both itself and a yoked control (R) during training, and the legs of P and R controlling stimulation independently during testing. In addition, testing was followed by reversal, in which each cockroach had to avoid the trained position in order to prevent exposure to light. During half-hour training periods. P cockroaches learned to lift a mesothoracic leg to turn off light. This learning was most evident during reversal, when P cockroaches continued to keep the leg lifted and were therefore exposed to appreciably more light than were R cockroaches. Cockroaches were unable to learn to lower the mesothoracic leg to escape light with a similar procedure.

Animals↗

Reductions in body temperature and spontaneous activity in rats exposed to horizontal rotation: abolition following chemical labyrinthectomy.

The effect of horizontal rotation of male rats (70 rpm) on core temperature and spontaneous motor activity levels was examined. In Experiment 1, subjects were chemically labyrinthectomized (VNX) by intratympanic (IT) injections of sodium arsanilate and control rats (VNS) received IT injections of saline. Half of the rats in each group were subsequently rotated and the other half sham rotated. Measurement of body temperature prior to, immediately after, and 20 min following rotation revealed significant (all p < 0.01) reductions in temperature immediately after treatment, and 20 min later, in VNS rats. Sham-rotated VNS and all VNX rats failed to exhibit any significant changes in temperature following treatment. In Experiment 2, motor activity level was monitored in chemically labyrinthectomized (VNX) and control (VNS) rats prior to, and following, horizontal rotation. The VNS rats exhibited large (all p < 0.01) depressions in measures of horizontal and vertical spontaneous motor activity following rotation treatment, whereas VNX rats exhibited similar levels of activity in the pre- and postrotation period. These experiments show that, as in humans, exposing rats to horizontal rotation results in reduction of body temperature and motor activity, and that these physiological and behavioral changes require a functional vestibular system.

Animals↗

Retention of rotationally induced taste aversions.

Retention interval effects are seen in single-element taste-aversion learning when taste aversions are significantly weaker if testing occurs 1 day after conditioning compared to tests conducted 3 or more days after conditioning. Since all previous demonstrations of this phenomenon have occurred following conditioning with the drug lithium chloride (LiCl), it was necessary to determine if the increased drinking at the 1-day interval was due to the aftereffects of LiCl. The present experiment explored the presence of retention interval differences following the use of a nonpharmacological unconditioned stimulus (US), rotational stimulation. Following a saccharin-rotation pairing, a saccharin aversion was seen at a 5-day testing interval, and this aversion was significantly stronger than the aversion observed at a 1-day test. Thus, these results are clear in showing that the retention interval effect occurs following conditioning with a nonpharmacological US, and this outcome allows for the refutation of an aftereffects of LiCl hypothesis.

Animals↗

Pure agraphia and Gerstmann's syndrome as a visuospatial-language dissociation: an experimental case study.

A right-handed man suffered a left parieto-occipital cerebral infarction, causing agraphia with Gerstmann's syndrome but without major aphasia, alexia, or apraxia. Oral spelling was superior to written spelling. Experiments were performed involving (1) analysis of errors in writing, (2) tasks of visual imagery, and (3) identifying letters drawn without leaving a visual trace. The results suggest that the agraphia and Gerstmann's syndrome are due to a dissociation of language skills and visuospatial skills caused by a dominant parieto-occipital lesion.

Aged↗

Pantomime, praxis, and aphasia.

The production and comprehension of pantomimed movements by asphasic subjects were studied with respect to their relationship to the aphasic deficit on one hand and apraxia on the other. At issue was whether impaired use of pantomime is a manifestation of reduced symbolic capacity or purely a manifestation of an apraxic impairment of purposeful movement or both. Tests of pantomime included a Pantomime Recognition Test, a nonverbal Transitive Pantomime Production Test, and an Intransitive Pantomime Production Test (to oral command). Imitation of Nonmeaningful Movements served as a measure of apraxia, uncontaminated by symbolic or linguistic factors. Imitation of Meaningful Movements taken from the pantomime tasks was also tested. Independent measures of auditory comprehension, picture naming, and reading comprehension were used as indices of language impairment. Intellectual function was measured by the Performance scale of the WAIS. Thirty aphasic subjects were examined. Twenty healthy age-matched normals served to establish scoring standards for the pantomime tests. Multiple regression analysis revealed significant, independent contributions from both auditory comprehension and imitation of Nonmeaningful Movements to all of the tests of pantomime production and pantomime recognition. All measures of pantomime production and pantomime recognition were strongly intercorrelated. While the three language measures were strongly correlated with each other, auditory comprehension was the only one of them that was significantly and consistently related to the pantomime tests. None was related to the imitation of nonmeaningful movement. The results are taken as indicating (1) that pantomime production and imitation share common factors with both praxis and auditory comprehension; (2) apraxia entails impairment of both production and interpretation of purposeful movements. Possible theoretical accounts for these results are offered.

Aged↗

Pyridostigmine-induced inhibition of blood acetylcholinesterase (AChE) and resulting effects on manual ocular tracking performance in the trained baboon.

A method was developed to determine the effects of pyridostigmine on sensory-motor control in baboons trained to perform visuo-oculo-manual tracking tasks. The performance was evaluated in terms of accuracy, maximum smooth pursuit velocity, and gain. Administration of pyridostigmine (0.4-0.7 mg/kg intramuscularly) induced a dose-related decrease in smooth pursuit performance which appeared 10 to 30 min after injection and lasted about 1 h. If the animal was allowed to track the target with its hand or to move the target itself, the smooth pursuit performance increased significantly, returning to near normal values. The movement of the hand was not altered. The effect of intramuscular injections of pyridostigmine (0.5 mg/kg) was studied on blood acetylcholinesterase activity in alert baboons. Maximum inhibition of about 60% of baseline activity was observed 10 min after pyridostigmine injection. Subsequently the activity slowly tended to return to control level. Three hours after drug administration, acetylcholinesterase activity inhibition was still 34.1% of control value. In the baboon, the time-course of acetylcholinesterase activity recovery after injection is similar to that recorded in human. The similarity of the time-course of blood acetylcholinesterase activity and changes in smooth pursuit performance suggests a causal relationship between the two factors. A further experiment showed that pyridostigmine administered per os at a dose normally used as a prophylactic against organophosphates does not significantly alter sensorimotor performance as evaluated at the oculomanual tracking system level. When compared to the literature, our results suggest that the baboon can be used as a human experimental analog for pharmacological studies such as the action of acetylcholinesterase inhibitors.

Acetylcholine↗

Pavlovian conditioning of distinct components of Hermissenda's responses to rotation.

In two experiments with the nudibranch mollusk Hermissenda, distinct characteristics of conditioned and unconditioned responses to high-speed orbital rotation were examined. In Experiment 1, two principle unconditioned responses to rotation were identified, namely, reduced rate of locomotion and contraction of the foot. The magnitude of the foot contraction increased throughout a 20-s period of rotation, whereas locomotion was reduced immediately after the onset of the rotation and was maintained at this constant low rate throughout the stimulus presentation. These divergent response patterns suggest that the two responses emerge independently. In Experiment 2, a classical conditioning procedure was employed in which a light (CS) was paired with the rotation (US) employed in Experiment 1. In a subsequent test, it was found that the light had acquired the capability to evoke both foot contraction and decreased locomotion. Although the magnitude of these conditioned responses was reduced relative to the corresponding unconditioned response, the patterns of responding were virtually identical; that is, foot contraction developed gradually whereas locomotion decreased immediately. In contrast, animals that received unpaired presentations of the light and rotation, light alone, or no prior exposure to those stimuli exhibited foot extension in response to the light. These results illustrate a transfer of some of the response-evoking properties of the US to the CS as a result of conditioning, as well as the emergence of two independent conditioned responses. Moreover, these results suggest modulation of at least two distinct motor pathways as a function of learning.

Animals↗

What is area 3a?

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Afferent Pathways↗

Kinaesthetic signals and muscle contraction.

Signals generated both peripherally and centrally contribute to the group of sensations termed kinaesthesia. Many experiments report sensations of position and movement under passive relaxed conditions without muscle contraction. However, kinaesthetic acuity is probably of greater functional value when subjects are active rather than passive and, accordingly, movement detection is markedly improved by muscular contraction. One mechanism contributing to this enhancement is likely to involve muscle spindle volleys. When identical microstimulation techniques are applied to skin, joint and muscle spindle endings innervating the hand, some cutaneous afferents and some joint afferents elicit a sensation, but activation of certain other cutaneous afferents and muscle spindle afferents rarely does. Activity in more than one muscle spindle afferent may be required for kinaesthetic sensations, whereas some single cutaneous and joint afferents may have a more 'secure' central projection.

Animals↗

Delayed-alternation performance after selective lesions within the prefrontal cortex of the cat.

On the basis of new neuroanatomical findings on relationships between subregions of the mediodorsal thalamic nucleus and the prefrontal cortex of the cat, it was attempted to investigate the relative importance of prefrontal subfields with the aim of obtaining evidence in favor of a functional inequality of different prefrontal subfields. Four areas, named presylvian (PRS), proreal (PR), dorsomedial (DM), and orbito-insular (OI) sectors, were ablated successfully in 30 adult animals. Performance of a 10-sec delayed-alternation task was compared pre- and postoperatively. Furthermore, most of the cats had to learn an extension of this task postoperatively, using a 20-sec delay period, and lastly, these animals were subjected to an extinction test. Significant performance differences were obtained between cats of different groups in all three tasks. Lesions of subregion PR, and even more of subregion PRS, led to severe behavioral deterioration, whereas lesions of subregion OI were without effect, when compared with the behavior of a sham-operated control group. PRS-cats, furthermore, showed motor disturbances during the first postoperative week. The results obtained suggest that it is possible to subdivide the cat's prefrontal cortex functionally. In addition, it is hypothesized that behavioral changes in cats of groups PRS and PR are due to an inability to use kinesthetic information properly.

Animals↗

Perceptual and motor effects elicited by a moving visual stimulus below the forearm: an example of segmentary vection.

It has been shown in man that movement of a visual stimulus under the forearm may induce illusory sensations of movement (segmentary vection) and motor activity in the same direction, such that, for example, a sensation of elbow flexion is accompanied by EMG activity in biceps brachialis. The characteristics of these two types of activity, perceptual and motor, are analyzed and compared with analogous phenomena described for the whole body. These comparisons bring out two essential features: the effectiveness of stimuli of small surface area applied to central regions of the retina, and the non-compensatory character of the motor phenomena. The results are discussed with respect to the participation of vision in the control and regulation of limb movements.

Adult↗