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PubMed1984

Neonatally bulbectomized rats with new olfactory-neocortical connections are anosmic.

Rats with one olfactory bulb removed when neonates and the second bulb removed when adults were tested on tone-light discrimination and odor detection tasks. On the neonatally operated side reconstituted olfactory receptor cell axons penetrated the frontal neocortex or portions of the anterior olfactory nucleus, and formed glomerular-like structures. On the adult operated side there was extensive scar formation which prevented in-growing sensory axons from contacting the brain. All experimental animals acquired the tone-light discrimination but failed to show any evidence of odor detection. These results indicate that reconstituted olfactory projections which terminate in the frontal neocortex or anterior olfactory nucleus do not support olfaction.

Acoustic Stimulation↗
PubMed1987

Multisensory convergence in the thalamus of the pigeon (Columba livia).

Neuronal activity was extracellularly recorded from the nucleus dorsolateralis posterior thalami (DLP) of anesthetized pigeons. The sensitivity of individual cells to stimuli of different sensory modalities: somatosensory, visual and auditory was investigated. A substantial population of the DLP neurons responded to mechanical stimulation of large, often bilateral areas of the animal's body surface. No somatotopic organization could be detected. The functional properties of these neurons resembled those described for mammalian nucleus posterior thalami neurons. The visually responsive cells could be driven from large areas of the visual field. Auditory sensitive neurons were optimally activated by wideband noise. Twenty-nine percent of the DLP recorded neurons showed polysensory properties responding either to somatosensory and visual or to somatosensory and auditory stimuli.

Acoustic Stimulation↗
PubMed1989

Responses of motor cortex neurons to visual stimulation in the alert monkey.

Evidence for visually evoked activity in single neurons of area 4 is presented. These neurons modulated their activity in relation to stimuli moving across the visual field of the monkey, without showing habituation. Some of them even had direction sensitivity. Their activity was independent of eye movements and unrelated to muscle contractions. The visually activated neurons were distributed throughout the depth of motor cortex.

Animals↗
PubMed1979

Diffuse noxious inhibitory controls (DNIC). I. Effects on dorsal horn convergent neurones in the rat.

(1) Sixty-eight convergent dorsal horn neurones have been recorded at the lumbar level in anaesthetized intact rats. All cells received prominent A alpha and C fibre afferents and correspondingly could be activated by high and low threshold stimuli applied to the peripheral excitatory receptive field. (2) The activity of 67/68 of these neurones was powerfully inhibited by noxious stimuli applied to various parts of the body. Since non-noxious stimuli were ineffective in this respect, the term "diffuse noxious inhibitory controls" (DNIC) is proposed. (3) DNIC could be evoked by noxious pinch applied to the tail, the contralateral hind paw, the forepaws, the ears and the muzzle; the most effective areas were the tail and muzzle. Noxious heat applied to and transcutaneous electrical stimulation of the tail were extemely effective in eliciting DNIC as was the intraperitoneal injection of bradykinin. (4) DNIC strongly depressed by 60-100% both the C fibre response following suprathreshold transcutaneous electrical stimulation and the responses to noxious radiant heat. (5) The spontaneous activity and the responses to low threshold afferents induced either by A alpha threshold electrical or natural stimulation were also powerfully inhibited. (6) In the majority of cases, long lasting post-effects directly related to the duration of conditioning painful stimulus were observed.

Animals↗
PubMed1990

Organization of the crossed tecto-reticulo-spinal projection in rat--II. Electrophysiological evidence for separate output channels to the periabducens area and caudal medulla.

The previous paper (Redgrave et al., Neuroscience 37, 571-584, 1990) presented anatomical evidence indicating there are at least two largely segregated components of the crossed tecto-reticulo-spinal pathway which project to the periabducens area and caudal medulla. An immediate question arising from this finding is whether tectal cells which project either to the periabducens area or to the caudal medulla have different electrophysiological response properties. An answer to this question would be relevant to the issue of whether different components of the tecto-reticulo-spinal system are specialized for the production of different classes of orienting movement. Accordingly, extracellularly recorded units in the superior colliculus of urethane anaesthetized rats were tested for antidromic activity following electrical stimulation of the periabducens area or the caudal medulla. When antidromic potentials were successfully recorded the sensory properties of the units were tested with a range of unimodal visual, somatosensory and auditory stimuli. The following results were obtained. (i) Tectal cells antidromically activated by stimulation of the caudal medulla were preferentially sensitive to somatosensory stimuli from the perioral region, while cells activated from the periabducens area were more frequently responsive to auditory stimuli. (ii) Tectal fibres activated by stimulation of the caudal medulla had significantly higher conduction velocities than the fibres activated by electrodes in the periabducens region. (iii) More than 90% of antidromically activated cells were located in stratum album intermediale or dorsal stratum profundum. These electrophysiological findings confirm and extend previous anatomical observations which indicate that components of the crossed descending projection of the colliculus may be functionally specialized for the production of different classes of orienting movements.

Acoustic Stimulation↗
PubMed1993

Acetylcholine, theta-rhythm and activity of hippocampal neurons in the rabbit--IV. Sensory stimulation.

Modifications of responses of hippocampal neurons to sensory stimuli at the background of increased endogenous acetylcholine level (injection of physostigmine) and during blocking by scopolamine were analysed in the chronic alert rabbit. A significant decrease of reactivity (about 40%) of hippocampal neurons to sensory stimuli occurred after physostigmine injection, inducing stable theta modulation. Suppression and decrease of inhibitory responses (including initial reset phase) and of some excitatory reactions (including on-effects) were observed. However, a limited group of excitatory responses was augmented and prolonged under physostigmine action. Scopolamine, which blocked electroencephalogram theta-rhythm, did not change the responsiveness of hippocampal neurons. Some of the inhibitory and excitatory effects of sensory stimuli, especially on-responses, were strongly facilitated. Tonic responses were shorter, but they were stably reproduced without typical gradual habituation. All these effects were also present in the hippocampus after basal undercutting of the septum, which eliminates ascending brainstem input. It is suggested that under normal conditions a new or significant sensory stimulus evokes, in the hippocampus, an initial inhibitory reset of neuronal activity with subsequent coordinated triggering of rhythmic theta modulation by the septal input and arrival of the cortical input signal phase-locked to it. During the period of theta triggered by the stimulus, its processing and fixation in memory occurs, while the other, interfering stimuli, which are not phase-locked to the ongoing theta activity, are actively filtered out. Thus, septohippocampal interactions may participate in the organization of selective attention as a necessary condition for memory trace formation.

Acetylcholine↗
PubMed1995

Increases in hippocampal and frontal cortical acetylcholine release associated with presentation of sensory stimuli.

In vivo microdialysis was employed to monitor acetylcholine release in the hippocampus and frontal cortex of freely behaving rats. Four stimuli were presented on separate occasions in the course of a dialysis session to rats with microdialysis probes implanted in the hippocampus or frontal cortex. Visual, auditory, olfactory and tactile stimuli elicited a number of different responses such as exploratory and consummatory behaviours. Presentation of two of the stimuli (auditory and tactile) also produced periods of alert immobility (freezing). All of the stimuli increased acetylcholine release in both the hippocampus and cortex: in the hippocampus, this increase was statistically significant with all except the olfactory stimulus, whereas in the cortex all but the visual stimulus resulted in significant increases. In the hippocampus, there were no significant differences between the increases in acetylcholine release produced by the four stimuli. In contrast, in the cortex, there was significant variation between the magnitude of acetylcholine release produced by the different stimuli: acetylcholine release elicited by tactile stimulation was greater than that produced by the other stimuli. There was no significant variation in the duration of increases in acetylcholine release produced by the stimuli in either the hippocampus or cortex. These results provide evidence that acetylcholine release is associated with a variety of behavioural responses to stimuli designed to produce arousal, and point to a role for cortical and hippocampal cholinergic mechanisms in arousal or attention. Further, the results suggest that under some circumstances cortical and hippocampal acetylcholine release may be regulated differentially.

Acetylcholine↗
PubMed1994

Discharge of identified deep cerebellar nuclei neurons related to eye blinks in the alert cat.

The activity of identified cerebellar nuclear neurons was recorded in the alert cat during blinks induced by corneal air puffs, light flashes and tones. Eyelid response to air puffs consisted of an early (16.5 +/- 2.7 ms) downward movement followed by two to three late downward steps. Blinks induced by flashes or tones presented longer latencies (52.6 +/- 4.8 and 50.1 +/- 8.0 ms). Type A neurons (n = 86) increased their spike activity in coincidence with the beginning of the blink, regardless of the stimulus modality. The late eyelid downward responses were accompanied by corresponding increases in the firing rate of the neuron. Type A neurons were activated mostly from the red nucleus (48/86) or the restiform body (24/86). Type B neurons (n = 30) fired a brief burst of spikes slightly preceding the blink, followed by a noticeable decrease in their firing rate. As for type A, the discharge response of type B neurons was always the same regardless of the sensory modality. These neurons were activated from the red nucleus (18/30), oculomotor complex (6/30) and restiform body (6/30). Although no precise temporal coupling was found between the beginning of the neuronal response and the start of either the stimulus or the motor response, linear regression analysis demonstrated significant relationships between mean firing rate of type A and B neurons and eyelid position, velocity and/or acceleration. Deep cerebellar nuclei neurons presented here seem to be directly involved in the execution of reflexively induced blinks following the smaller details of eyelid motor performance. The opposite behavior of type A and B cells suggests an interplay of reciprocal actions to determine the ongoing displacements of the lid. Finally, the cerebellum seems to influence blinks through a spread action on many brainstem sites and not exclusively on the red nucleus.

Acoustic Stimulation↗
PubMed1994

Sensory responsiveness of "broad-spike" neurons in the laterodorsal tegmental nucleus, locus coeruleus and dorsal raphe of awake rats: implications for cholinergic and monoaminergic neuron-specific responses.

Although cholinergic neurons in the laterodorsal and pedunculopontine tegmental nuclei have been shown to have a pivotal role in neural mechanisms of paradoxical sleep, their function during wakefulness is less understood. To examine the latter, we have recorded from "broad-spike neurons", which were distinguished by their long spike duration, in the laterodorsal tegmental nucleus of undrugged, head-restrained rats, and examined their response properties to sensory stimuli such as light touch to the tail, air puff to the face, 2 kHz pure tone and flashes of light. Broad-spike neurons from the locus coeruleus and dorsal raphe nucleus were studied for comparison; these neurons have been demonstrated to be noradrenergic and serotonergic, respectively. The broad-spike neurons in the laterodorsal tegmental nucleus have also been suggested to be cholinergic. There were two kinds of responses: (1) a simple increase or decrease in firing, reflecting an elevated level of vigilance; and (2) a phasic response composed of a single spike or brief, high frequency burst, usually diminishing or disappearing upon repetition of the stimulus. When two or more types of stimuli were effective in a neuron, they evoked responses of the same quality. Most of the dorsal raphe neurons displayed only the simple increase of firing, whereas the locus coeruleus neurons gave a phasic response with rather weak attenuation upon repetition. Compared with these, the laterodorsal tegmental neurons were heterogeneous: about one-quarter showing only a simple change of firing (half increasing, half decreasing); and two-thirds displaying phasic responses. The latter response of many neurons attenuated strongly upon repetition. The laterodorsal tegmental neurons were classified into several groups according to their spontaneous firing behavior during sleep and wakefulness, but every neuron in a group did not show the same type of response. For example, some of the neurons which were most active during paradoxical sleep and essentially silent during wakefulness decreased or stopped firing upon sensory stimulation, while others in this group had strong phasic responses. These results suggest that putative cholinergic neurons in the laterodorsal tegmental nucleus have heterogenous properties not only with respect to their spontaneous activity during sleep and wakefulness but also with respect to their response to sensory stimulation. Some of these neurons may function to induce a global attentive state in response to a novel stimulus.

Acoustic Stimulation↗
PubMed1995

Neuronal responsiveness to various sensory stimuli, and associative learning in the rat amygdala.

Neuronal activities were recorded from the amygdala and amygdalostriatal transition area of behaving rats during discrimination of conditioned auditory, visual, olfactory, and somatosensory stimuli associated with positive and/or negative reinforcements. Neurons were also tested with taste solution and various sensory stimuli that were not associated with reinforcement. Of the 1195 neurons tested, 475 responded to one or more sensory stimuli. Of these, 256 neurons responded exclusively to a unimodal sensory stimulus, 128 to multimodal sensory stimuli, and the remaining 91 could not be classified. Distribution of unimodal neurons was correlated with anatomical projections to the amygdala from sensory thalamus or sensory cortices. Multimodal neurons were located mainly in the basolateral and central nuclei of the amgydala. Response latencies of neurons in the basolateral nucleus were longer than those in other nuclei and neurons in the central nucleus had both short and long latencies. Neurons responsive to a given stimulus were more frequently encountered in the amygdalas of the trained rats than in those of the rats not trained to associate that stimulus with a reinforcement. Multimodal neurons that responded to conditioned and/or unconditioned stimuli used in the associative learned tasks were concentrated in the basolateral and central nuclei. The results indicate that some amygdalar neurons receive exclusive single sensory information, and the others receive information from two or more sensory inputs. Considering the long latencies and multimodal responsiveness, the basolateral and central nuclei of the amygdala might be foci where various kinds of sensory information converge. It is also suggested that the basolateral and central nuclei of the amygdala have critical roles in associative learning to relate sensory information to reinforcement or affective significance.

Acoustic Stimulation↗
PubMed1996

Changes in eye blink responses following hypoglossal-facial anastomosis in the cat: evidence of adult mammal motoneuron unadaptability to new motor tasks.

Hypoglossal-facial anastomosis is used in humans to restore the activity of the mimic musculature following irrecoverable facial nerve lesions. As eyelid movement kinetics is very well known, we have used this experimental model in cats to follow the evolution of blink responses and the adaptability of hypoglossal motor pools to new motor tasks. Although the electromyographic activity of the orbicularis oculi muscle in response to corneal air puffs, flashes of light or electrical stimulation of the supraorbital nerve was not recovered in the seven months following this crossed anastomosis, reflex blinks were got back by the increased activity of the retractor bulbi and extraocular recti muscles. The lid of the anastomosed side oscillated in perfect synchronization with tongue movements during licking, while it was severely affected in its motor function during optokinetic stimulation because of the spontaneous appearance of tongue-related hypoglossal activity. Present results suggest that adult mammal motoneurons are unable to readapt their motor programs to the kinetic needs of new motor targets and that most of the functional recovery observed in the cat was achieved by the compensatory hyperactivity of motor systems not directly affected by the surgery.

Adaptation, Physiological↗
PubMed1982

Cigarette smoking, manifest anxiety and somatic symptoms.

Fifty smokers and fifty non-smokers were administered the MMPI's Manifest Anxiety Scale (MAS). Mean MAS scores for smokers were significantly higher than those of non-smokers. Item analysis revealed that smokers obtained higher scores than non-smokers on significantly more items in which anxiety is manifested by a physical symptom rather than a psychological symptom. It is possible that physical stimulation by nicotine may contribute to a more ready arousal to anxiety in smokers.

Adult↗
PubMed1977

Responsiveness to stimulation during paradoxical sleep in infants.

11 healthy children were repeatedly studied during 2 sleep cycles in 2 sessions at 2,6, 12 and 20 wk of life. Three acoustic stimuli, light and tactile stimulus were applied in a randomized order in intervals ranging randomly from 30 to 120 sec. Continuous polygraphic recordings were made of respiration, REMs, EEG and EMG of biceps and triceps brachii. The effect of stimuli on the length of paradoxical sleep, REMs and EMG was assessed. There were age-related changes in the number of REMs after stimuli. At 2 and 6 wk no stimulus elicited any change. At 12 wk the children responded with an increased number of rapid eye movements to acoustic stimuli, at 20 wk they responded to acoustic stimuli and light. The conclusion is that, as far as REMs are concerned, responsiveness during paradoxical sleep changes with age. There was a difference in the incidence of EOG responses and EMG responses. These findings show that it is not possible to assess responsiveness in infants during PS by one measure only.

Acoustic Stimulation↗
PubMed1993

Functional brain imaging at 1.5 T using conventional gradient echo MR imaging techniques.

There is considerable interest in the use of MR imaging to study brain function. Recently, it has been demonstrated that small changes in signal intensity occur in the visual cortex in T2*-weighted imaging in response to appropriate visual stimuli. Similar responses to activation have also been recorded in motor cortex as well as frontal lobes. To date most of these studies have been carried out at very high field strength or they have used echo planar imaging. We report our preliminary results showing that the effects of activation of visual and motor areas of the brains of normal volunteers can be recorded using conventional MR imaging methods on a standard 1.5 T clinical scanner. Using gradient-echo imaging sequences, we have been able to map activated visual and motor cortex with high spatial resolution in multiple planes, and are using this technique to examine the relationship between physiological response and stimulus parameters. Signal changes of the order of 2-12% in images with TE = 45 msec, TR = 120 msec, and alpha = 40 degrees, permit excellent depiction of the regions affected.

Brain↗
PubMedDate not supplied

Effects of toluene, styrene, trichloroethylene, and trichloroethane on the vestibulo-and opto-oculo motor system in rats.

The acute effects of inhalation of four solvents on the central vestibular system of rats were analyzed by recording eye movements upon different stimuli. The dose-response relationship was investigated. Optokinetic stimulation was obtained by placing the animals in front of a surrounding visual pattern, moving at different velocities. The slow-phase eye velocity (SPV) of nystagmus was calculated and divided by the stimulus velocity, giving the gain. All the solvents caused a decrease of the gain. Vestibular stimulation was performed on a turntable by an angular acceleration/deceleration in darkness. The SPV and the duration of the post-stimulatory nystagmus were calculated. The shape of the SPV dose-response curves differed among the four solvents. Toluene, styrene, and trichloroethylene prolonged the duration of nystagmus while trichloroethane did not. A conflicting vestibular and optokinetic stimulation was performed by an angular acceleration/deceleration with a surrounding visual pattern moving with the turntable. All solvents decreased the ability to cancel nystagmus, elicited by vestibular stimulation in conflict with a visual input. Quick movements of the eyes, saccades, were elicited by tactile stimulation. Toluene, styrene, and trichloroethylene changed the generation of the saccades while trichloroethane did not. Most of the findings indicate a common site of action in the central vestibular system, viz, the cerebellar-vestibular circuit. However, within this domain, there are evident differences in the effects among the solvents. This findings, together with previous results obtained in other experimental models of the central nervous system (CNS), suggest that different solvents should be considered as individual compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Alcohol seeking in C57BL/6 mice induced by conditioned cues and contexts in the extinction-reinstatement model.

We have recently shown that the alcohol self-administration context can reinstate extinguished responding for alcohol when that extinction occurs in a different context [Burattini, C., Gill, T. M., Aicardi, G., & Janak, P. H. (2006)]. The ethanol self-administration context as a reinstatement cue: acute effects of naltrexone. Neuroscience, in press; Zironi, I., Burattini, C., Aicardi, G., & Janak, P. H. (2006). Context is a trigger for relapse to alcohol. Behav Brain Res 167, 150-155). Here, we test whether the C57BL/6 mice will also show context-induced reinstatement for alcohol, and whether presentation of an alcohol-associated cue will alter the observed responding. Male C57BL/6 mice were trained to lever press on a fixed ratio-3 schedule for a 10% ethanol solution in a context made distinctive using visual, tactile, and olfactory stimuli. Each ethanol delivery was paired with a compound tone-light stimulus. After training, extinction sessions were given in a distinct context, comprised of different visual, tactile, and olfactory stimuli; the compound cue and the alcohol were not available during these sessions. In Experiment 1, after response extinction, subjects were tested by placement into both the alcohol self-administration context and, on a subsequent test, by response-contingent presentation of the cue following placement into the alcohol self-administration context. In Experiment 2, after response extinction, subjects were tested in both of these conditions, with the addition of a test of the effects of response-contingent presentation of the cue in the extinction context. The results indicate that the alcohol self-administration context produces a mild increase in responding at the alcohol lever, and that presentation of the alcohol-associated cue in the alcohol context, but not the extinction context, strongly increases responding on the alcohol lever. These findings suggest that the power of an alcohol-associated cue can be modulated by the context. The observed effects of alcohol contexts and cues on alcohol-seeking behavior in the C57BL/6 mouse suggest that this reinstatement model may be useful for understanding the neurobiological and genetic mechanisms of relapse triggered by conditioned environmental stimuli.

Alcohol Drinking↗
PubMed2005

Behavioral, cognitive and biochemical responses to different environmental conditions in male Ts65Dn mice, a model of Down syndrome.

Ts65Dn mouse is the most widely accepted model for Down syndrome. We previously showed that environmental enrichment improved spatial learning in female but deteriorated it in male Ts65Dn mice. This study analyzed the factors contributing to the disturbed cognition of male Ts65Dn mice after enriched housing, by allocating male control and Ts65Dn mice in four conditions after weaning: small (n = 2-3) and large group (n = 8-10) housing, and enriched housing in small (2-3) and large groups (8-10). Learning, aggressive behavior, anxiety-like behavior and biochemical correlates of stress were evaluated when Ts65Dn and control mice were 4-5 months old. Environmental enrichment in large mixed colonies of Ts65Dn and diploid littermates disturbed behavioral and learning skills of Ts65Dn mice in the Morris water maze. ACTH and testosterone levels were not modified in any group of mice. Ts65Dn and control mice subjected to enriched housing in large groups and Ts65Dn mice housed in large groups showed higher corticosterone levels. Aggressive behavior was evaluated by measuring the number of attacks performed in the presence of an intruder. Ts65Dn mice performed less attacks than controls in all conditions, especially after enriched housing, indicating subordination. In the plus maze, cognitive aspects (i.e. risk assessment) and motor components (open arm avoidance) of anxiety behavior were evaluated; no difference in any condition was found. It is suggested that an excess of social and/or physical stimulation in Ts65Dn mice may affect cognition by disturbing the emotional and behavioral components of the learning process.

Adrenocorticotropic Hormone↗