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PubMed1997

Individual differences in neural sensitization and the role of context in illness from low-level environmental chemical exposures.

This paper summarizes the clinical phenomenology of multiple chemical sensitivity (MCS), outlines the concepts and evidence for the olfactory-limbic, neural sensitization model for MCS, and discusses experimental design implications of the model for exposure-related research. Neural sensitization is the progressive amplification of responsivity by the passage of time between repeated, intermittent exposures. Initiation of sensitization may require single toxic or multiple subtoxic exposures, but subsequent elicitation of sensitized responses can involve low or nontoxic levels. Thus, neural sensitization could account for the ability of low levels of environmental chemicals to elicit clinically severe, adverse reactions in MCS. Different forms of sensitization include limbic kindling of seizures (compare temporal lobe epilepsy and simple partial seizures) and time-dependent sensitization of behavioral, neurochemical, immunological, and endocrinological variables. Sensitized dysfunction of the limbic and mesolimbic systems could account in part for many of the cognitive, affective, and somatic symptoms in MCS. Derealization (an alteration in perception making familiar objects or people seem unfamiliar or unreal) is a common MCS symptom and has been linked with limbic dysfunction in clinical neuroscience research. Sensitization is distinct from, but interactive with, other neurobiological learning and memory processes such as conditioning and habituation (compare adaptation or tolerance). In previous studies, hypotheses for MCS involving sensitization, conditioning, and habituation (adaptation) have often been considered in isolation from one another. To design more appropriate chemical exposure studies, it may be important to integrate the various theoretical models and empirical approaches to MCS with the larger scientific literature on individual differences in these potentially interactive phenomena.

Adaptation, Physiological↗

PubMed1981

A 40-Hz auditory potential recorded from the human scalp.

Computer techniques readily extract from the brainwaves an orderly sequence of brain potentials locked in time to sound stimuli. The potentials that appear 8 to 80 msec after the stimulus resemble 3 or 4 cycles of a 40-Hz sine wave; we show here that these waves combined to form a single, stable, composite wave when the sounds are repeated at rates around 40 per sec. This phenomenon, the 40-Hz event-related potential (ERP), displays several properties of theoretical and practical interest. First, it reportedly disappears with surgical anesthesia, and it resembles similar phenomena in the visual and olfactory system, facts which suggest that adequate processing of sensory information may require cyclical brain events in the 30- to 50-Hz range. Second, latency and amplitude measurements on the 40-Hz ERP indicate it may contain useful information on the number and basilar membrane location of the auditory nerve fibers a given tone excites. Third, the response is present at sound intensities very close to normal adult thresholds for the audiometric frequencies, a fact that could have application in clinical hearing testing.

Auditory Pathways↗

PubMed1992

Visual, somatosensory, olfactory, and gustatory hallucinations.

Hallucinations that involve any of the sensory modalities may accompany a number of functional and organic conditions. Although characteristics of the hallucinations are not specific, they are characteristic and suggestive of specific disorders. Appropriate evaluation and treatment require consideration of the past psychiatric, neurologic, and medical history; assessment of accompanying psychiatric and neurologic signs and symptoms; and degree of response to conventional therapy. Any patient with hallucinations of recent onset or presenting a significant change in the nature of prior hallucinations, particularly when the patient does not respond to conventional therapy, deserves an evaluation to rule out treatable organic factors.

Female↗

PubMed2004

Differences between recognition memory and remote memory for olfactory and visual stimuli in nondemented elderly individuals genetically at risk for Alzheimer's disease.

Recognition and remote memory for olfactory and visual stimuli were assessed in nondemented elderly individuals positive for the apolipoprotein E 4 allele and in 4 negative controls to examine whether the 4 allele differentially affects recognition and/or remote memory depending on the modality of stimulus to be remembered. Compared to controls, 4 positive individuals committed more false positive recognition memory errors for olfactory but not visual stimuli suggesting that 4 positive individuals may show false positive errors for olfactory stimuli before deficits for other stimuli are detectable. There were no significant differences in familiarity ratings (a proposed measure of remote memory) suggesting that brain areas involved in remote memory are not affected in nondemented 4 positive individuals. The results suggest that neuropathological changes in nondemented individuals genetically at risk for Alzheimer's disease may differentially affect memory processes.

Aged↗

PubMed1976

[An attempt to prognosticate the rehabilitation of patients who have sustained closed brain injury].

The authors studied at the early and remote stages of the disease the adaptational function of analyzers (visual, acoustic, olfactory) and constructive practical actions in 82 patients who had suffered from closed brain traumas in peace-time. The same studies were conducted in 59 patients with remote sequealae of brain injuries during the wartime (barotraumas) for comparison. The authors compared the results of the studies on patients with different outcomes of rehabilitation and different kinds of brain injury and depicted some indices and manifestations unfavourable or relatively favourable for a social and occupational prognosis.

Adaptation, Physiological↗

PubMed1981

Behavioral characteristics of vasopressin-deficient rats (Brattleboro strain).

A group of vasopressin-deficient rats (Brattleboro strain--DI) and a group of normal Long-Evans rats were successively evaluated on visual discrimination, olfactory discrimination, delayed alternation at short and long intertrial intervals (ITIs), approach-avoidance conflict in a straight runway, and open-field behavior. It was found that DI rats adapted more slowly than normal rats in the T-maze, in the straight runway, and they were slower to emerge into the open field. The DI rats were impaired relative to normal animals on the discrimination tasks (visual and olfactory), but they were not impaired on delayed alternation (at least for short ITIs). DI rats also showed better retention of the punishment effect in the approach-avoidance conflict test than normal animals. It is suggested that DI rats have defective reference-memory mechanisms, fairly intact working-memory processes and altered adaptability (timidity or cautiousness).

Animals↗

PubMed1989

Sensory systems and behavior of premetamorphic and metamorphic leptocephalous larvae.

The superorder Elopomorpha (orders Anguilliformes, Elopiformes and Notacanthiformes) is characterized by the presence of a unique larval stage termed the leptocephalus. The basic morphology, chemical composition, developmental pattern, and behavior of premetamorphic and metamorphic leptocephali are reviewed. The eyes, olfactory organs and pores of the lateral-line system are well developed, suggesting that these sensory structures play an important role in larval behavior. Premetamorphic larvae are pelagic and in some elopomorphs subsequent development is associated with migration to coastal waters where metamorphosis takes place. The factors controlling onshore migration, as well as the metamorphic trigger(s), are unknown. The possible relationships between sensory systems and behavioral changes during the different phases of larval development are presented.

Animals↗

PubMed1997

Implications of immediate-early gene induction in the brain following sexual stimulation of female and male rodents.

Induction of immediate-early genes (IEGs), such as c-fos, has been widely used to mark the activation of brain regions following different types of sexual stimulation and behavior. A relatively common set of hormone-concentrating basal forebrain and midbrain structures in female and male rodents is activated by copulatory stimulation, in particular, stimulation of sensory nerves that innervate the penis or vagina/cervix, olfactory or pheromonal stimuli, and conditioned sexual incentives. These regions include the preoptic area, lateral septum, bed nucleus of the stria terminalis, paraventricular hypothalamus, ventromedial hypothalamus, medial amygdala, ventral premammillary nuclei, ventral tegmentum, central tegmental field, mesencephalic central gray, and peripeduncular nuclei. Regions that do not contain classic intracellular steroid receptors, such as the ventral and dorsal striatum or cortex, are also activated. IEGs have also been colocalized with cytoplasmic proteins like GnRH and oxytocin, and have been used in conjunction with retrograde tracers to reveal functional pathways associated with different sexual behaviors. Steroid hormones can also alter the ability of sexual stimulation to induce IEGs. Despite the many similarities, some differences in IEG induction between sexes have also been found. We review these findings and raise the question of what IEG induction in the brain actually means for sexual behavior, that is, whether it indicates the perception of sexual stimulation, commands for motor output, or the stimulation of a future behavioral or neuroendocrine event related to the consequences of sexual stimulation. To understand the role of a particular activated region, the behavioral or neuroendocrine effects of lesions, electrical stimulation, drug or hormone infusions, must also be known.

Animals↗

PubMed1993

Altered synaptic plasticity and memory formation in nitric oxide synthase inhibitor-treated rats.

Nitric oxide (NO) is a messenger molecule that is produced in the brain from the metabolism of L-arginine to L-citrulline. Growing evidence suggests a physiological role for NO in long-term potentiation (LTP). Since LTP is a form of synaptic plasticity thought to be involved in learning and memory, we have tested whether inhibition of endogenous NO production affects memory capacities of rats. We found that the NO synthase [L-arginine, NADPH:oxygen oxidoreductase (nitric oxide-forming), EC 1.14.13.39] inhibitor N omega-nitro-L-arginine, at doses blocking LTP in hippocampal slices, impairs spatial learning in a radial arm maze and olfactory memory in a social recognition test. In contrast, N omega-nitro-L-arginine left shock-avoidance learning unaffected. These results indicate that NO is involved in some but not all forms of memory and further support the existence of a causal link between LTP and spatial learning.

Amino Acid Oxidoreductases↗

PubMed1999

[Hearing loss, disorders of sound localization with the preservation ofsmell and taste in diabetics].

Diabetes is often complicated by serious medical conditions which could be related to the development of auditory system and cranial nerves lesions, disorder of sound localisation and decreased olfactory and taste ability. Cranial nerve palsies in diabetes are considered as an integral part of the main disease. Twenty nine children with diabetes and non-diabetics control group, without a history of exposure to noise, ototoxic drugs, or ear disease aged 4-19 years old were examined. Hearing impairment may be present in children with disease duration above 3-5 years and in children with other complications. Sound localisation tests were performed by the method of Zakrzewski from a free auditory field, measuring the angle of directional hearing acuity in 35 diabetics age from 16 to 78 years. Longer duration of diabetes was associated with higher directional hearing acuity. Higher hearing loss was observed with higher directional values in diabetics. The authors investigated smell and taste in 35 diabetics. All patients were treated with insulin. Impairment value of smell identification thresholds was much more frequent than impairment of smell perception. In no case raised threshold of taste perception.

Adolescent↗

PubMed1979

Olfactory and visual differentiation of synthetically scented surrogates by infant squirrel monkeys.

Twelve infant squirrel monkeys were reared with distinctively colored and scented inanimate surrogates (Green/Floral or Black/Clove) and tested monthly from 1 to 6 months of age in 3 paired-comparison conditions that assessed the efficacy of synthetic olfactory cues and color cues as attractive properties of the surrogates. The infants developed specific attractions to both the rearing odor and color of the surrogates by approximately the end of Month 4, although substantial differences existed between the 2 rearing groups, particularly with respect to color responsiveness. When compared with previous findings on infant squirrel monkeys reared with naturally scented surrogates, odor preferences developed relatively late, suggesting that natural, species-typical odors may have inherently stronger attractive properties for Saimiri than arbitrary synthetic odors.

Age Factors↗

PubMed1990

Brain mechanisms underlying motor skill learning in the rat.

Young rats subjected to bilateral brain lesions were subsequently tested for acquisition of eight puzzle-box problems. Lesions to 12 of the 37 brain sites investigated (anterior pretectal area, subthalamus, posterolateral hypothalamus, frontocingulate cortex, anterior thalamus, mediodorsal thalamus, ventromedial thalamus, parafascicular nucleus, mamillary bodies, cerebellum, olfactory bulb, and ventromedial hypothalamus) retarded puzzle-box learning. This study, combined with earlier investigation of 11 additional brain sites, show that 21 of the 48 total brain structures are involved in motor skill learning. These findings suggest that motor skill learning requires the integrity of a nonspecific mechanism and several specific mechanisms, such as vestibular-proprioceptive-kinesthetic discrimination mechanism and probably also response flexibility, visuospatial attentional, visual discrimination and place learning mechanisms.

Animals↗

PubMed1975

Acquisition of verbal associations to olfactory stimuli of varying familiarity and to abstract visual stimuli.

Two paired-associate (PA) learning studies observed the acquisition performance of 85 college students with either odors or abstract figures as stimuli and numbers as responses. In both studies visual PA acquisition was reliably superior to olfactory learning. Since the second study was designed to maximize the learning of associations to the odors and minimize the learning of associations to the figures, it appears that the sense of smell is not as well suited to the PA task as vision when essentially naive subjects are involved. In a third experiment, the familiarity of odors and figures was judged and reported as a graphic magnitude estimation response. These judged stimulus familiarities were used to select stimuli for the PA task. Subsequently, PA acquisition was facilitated by the use of highly familiar odors.

Adolescent↗

PubMed1988

Symbolic cross-modal transfer in two species of chimpanzees.

2 common chimpanzees and 1 pygmy chimpanzee, all of whom were proficient lexigram symbol users, were tested on symbolic cross-modal tasks. Previous cross-modal work with nonhuman primates has been limited to nonsymbolic matching tasks. None of these chimpanzees received any advance training on cross-modal tasks prior to the testing reported here. The common chimpanzees, Sherman and Austin, were tested on visual to haptic, visual-symbolic to haptic, haptic to visual-symbolic, and olfactory to visual-symbolic matching tasks. The pygmy chimpanzee, Kanzi, was tested on auditory-symbolic to pictorial and auditory-symbolic to visual-symbolic matching tasks. All subjects were able to match stimuli across the tested dimensions with no training. These results indicate that chimpanzees who have received symbol training can perform symbolic cross-modal tasks similar to those that are typically used with human subjects. These tasks require not only cross-modal associations but also the transformation of information from symbolic to representational modes.

Animals↗

PubMedDate not supplied

[Cartilaginous torus epithelium of the vomeronasal organ of swine and sheep].

The vomeronasal organ consists of receptor cells of microvillous type, supporting and basal cells. According to their ultrastructural organization the microvillar cells are analogous to those in the main olfactory organ in the pig and have all signs of the receptor cell: microvilli at the top and centrioles in cytoplasm, as well as the central process getting off the cell body. Both in the pig and in the sheep the supporting cells contain in their apical region a number of basal bodies with cilia, getting them off. In the receptor zones of epithelium albuminous glands predominate, in the respiratory zones--mucous ones. A great amount of liquid mucus, excreted on the surface of the epithelium by numerous glands and supporting cells, apparently, facilitates adsorption and desorption of odorous molecules from the receptor cells after their stimulation. The cilia of the supporting cells probably from the stream of the vomeronasal mucus. The cartilagenous torus epithelium of the vomeronasal organ of the pig and sheep has in general a similar structural organization. This demonstrates general for Vertebrata receptor mechanisms of odorous substances, evidently connected with perception of feramones or contact olfaction.

Animals↗

PubMed2005

Functional interaction between the associative parietal cortex and hippocampal place cell firing in the rat.

The hippocampus and associative parietal cortex (APC) both contribute to spatial memory but the nature of their functional interaction remains unknown. To address this issue, we investigated the effects of APC lesions on hippocampal place cell firing in freely moving rats. Place cells were recorded from APC-lesioned and control rats as they performed a pellet-chasing task in a circular arena containing three object cues. During successive recording sessions, cue manipulations including object rotation in the absence of the rat and object removal in the presence of the rat were made to examine the control exerted by the objects or by non-visual intramaze cues on place field location, respectively. Object rotations resulted in equivalent field rotation for all cells in control rats. In contrast, a fraction of place fields in APC-lesioned rats did not rotate but remained stable relative to the room. Object removal produced different effects in APC-lesioned and control rats. In control rats, most place fields remained stable relative to the previous object rotation session, indicating that they were anchored to olfactory and/or idiothetic cues. In APC-lesioned rats, a majority of place fields shifted back to their initial, standard location, thus suggesting that they relied on uncontrolled background cues to maintain place field stability. These results provide strong evidence that the hippocampus and the APC cooperate in the formation of spatial memory and suggest that the APC is involved in elaboration of a hippocampal map based on proximal landmarks.

Action Potentials↗

PubMed2004

Age- and sex-related disturbance in a battery of sensorimotor and cognitive tasks in Kunming mice.

A battery of tasks, i.e. beam walking, open field, tightrope, radial six-arm water maze (RAWM), novel-object recognition and olfactory discrimination, was used to determine whether there was age- and sex-related memory deterioration in Kunming (KM) mice, and whether these tasks are independent or correlated with each other. Two age groups of KM mice were used: a younger group (7-8 months old, 12 males and 11 females) and an older group (17-18 months old, 12 males and 12 females). The results showed that the spatial learning ability and memory in the RAWM were lower in older female KM mice relative to younger female mice and older male mice. Consistent with this, in the novel-object recognition task, a non-spatial cognitive task, older female mice but not older male mice had impairment of short-term memory. In olfactory discrimination, another non-spatial task, the older mice retained this ability. Interestingly, female mice performed better than males, especially in the younger group. The older females exhibited sensorimotor impairment in the tightrope task and low locomotor activity in the open-field task. Moreover, older mice spent a longer time in the peripheral squares of the open-field than younger ones. The non-spatial cognitive performance in the novel-object recognition and olfactory discrimination tasks was related to performance in the open-field, whereas the spatial cognitive performance in the RAWM was not related to performance in any of the three sensorimotor tasks. These results suggest that disturbance of spatial learning and memory, as well as selective impairment of non-spatial learning and memory, existed in older female KM mice.

Age Factors↗

PubMed2002

Autonomic nervous system responses to odours: the role of pleasantness and arousal.

Perception of odours can provoke explicit reactions such as judgements of intensity or pleasantness, and implicit output such as skin conductance or heart rate variations. The main purpose of the present experiment was to ascertain: (i) the correlation between odour ratings (intensity, arousal, pleasantness and familiarity) and activation of the autonomic nervous system, and (ii) the inter-correlation between self-report ratings on intensity, arousal, pleasantness and familiarity dimensions in odour perception. Twelve healthy volunteers were tested in two separate sessions. Firstly, subjects were instructed to smell six odorants (isovaleric acid, thiophenol, pyridine, L-menthol, isoamyl acetate, and 1-8 cineole), while skin conductance and heart rate variations were being measured. During this phase, participants were not asked to give any judgement about the odorants. Secondly, subjects were instructed to rate the odorants on dimensions of intensity, pleasantness, arousal and familiarity (self-report ratings), by giving a mark between 1 (not at all intense, arousing, pleasant or familiar) and 9 (extremely intense, arousing, pleasant or familiar). Results indicated: (i) a pleasantness factor correlated with heart rate variations, (ii) an arousal factor correlated with skin conductance variations, and (iii) a strong correlation between the arousal and intensity dimensions. In conclusion, given that these correlations are also found in other studies using visual and auditory stimuli, these findings provide preliminary information suggesting that autonomic variations in response to olfactory stimuli are probably not modality specific, and may be organized along two main dimensions of pleasantness and arousal, at least for the parameters considered (i.e. heart rate and skin conductance).

Adult↗