Topographical maps of orientation specificity

A spatially congruent framework for orientation encoding in the primate striate visual cortex is proposed and discussed. This framework, which is based on the foot-of-normal representation of straight lines, not only provides a reasonable explanation for the centric organization of the orientation specificity in the primate striate visual cortex but also accounts for a series of experimentally verified intriguing phenomena such as the lack of orientation specificity around the centres of the orientation modules (i.e. the singularities), the increased neural activity at these same places, and the relatively uniform distribution of the singularities along the ocular dominance columns. The proposed framework can also explain and predict the possible existence of centric modules in other cortical regions containing topographical maps of two-dimensional sensory spaces (e.g. pre-striate and somatic sensory cortex). A simple one-layer neural model of the basic centric module in the framework is presented, and simulation results are discussed.     

Semantic knowledge influences prewired hedonic responses to odors

Background

Odor hedonic perception relies on decoding the physicochemical properties of odorant molecules and can be influenced in humans by semantic knowledge. The effect of semantic knowledge on such prewired hedonic processing over the life span has remained unclear.

Methodology/Principal Findings

The present study measured hedonic response to odors in different age groups (children, teenagers, young adults, and seniors) and found that children and seniors, two age groups characterized by either low level of (children) or weak access to (seniors) odor semantic knowledge, processed odor hedonics more on the basis of their physicochemical properties. In contrast, in teenagers and young adults, who show better levels of semantic odor representation, the role of physicochemical properties was less marked.

Conclusions/Significance

These findings demonstrate for the first time that the biological determinants that make an odor pleasant or unpleasant are more powerful at either end of the life span.     

Olfactory receptor cell responses of pigeon to some odors

A preparation has been developed in the pigeon which allows recording of the electrical activity from an olfactory nerve twig containing the nonmyelinated axons of a small group of olfactory receptor cells. The pigeon's response to n-amylacetate is vigorous and stable, like that of other air-breathing animals. Responses in the olfactory receptor cells in the pigeon increased in magnitude with increase in the odor concentration. An olfactory nerve twig produced a different magnitude of responses to the various odor stimuli. When an odor stimulation was applied to the olfactory mucosa, the two different olfactory nerve twigs which were separated from the same olfactory nerve bundle produced a different magnitude of responses. The differences may be dependent on several factors.     

Dynamic characteristics of the human resonance EEG responses to rhythmic photostimulation

The development of the resonance EEG responses of the left and right occipital areas was studied in right-handed men during prolonged (12 or 120 s) rhythmic, photostimulation with the intensity of 0.7 J and frequencies of 6, 10, and 16 Hz. Analysis of the EEG fine spectral structure was applied to compare the accumulated baseline EEG spectra and EEG spectra during photostimulation, to observe the dynamics of the short-term spectra and to detect power changes in the EEG narrow spectral band sharply coincident with the stimulation frequency. The more pronounced EEG responses to photostimulation were observed in subjects with the initially low EEG baseline, α-rhythm. Two-minute flash trains produced a substantial increase in the EEG power within the stimulation frequency with superposed oscillatory processes with different periods. These fluctuations are considered a reflection of intricate interaction between the adaptive and resonance EEG responses to the presented intermittent stimulation. Under 12-s stimulation the resonance EEG responses are steadily recorded within the first 3 s of stimulation and immediately after the flash cessation EEG power at the stimulation frequency returns to the initial level. The resonance EEG responses were more pronounced in the right hemisphere than in the left one, especially, at the stimulation frequencies of 6 and 16 Hz. With increasing the stimulation frequency, the maximum of resonance EEG responses was reached earlier. Under the stimulation frequency of 6 Hz, the maximal response was recorded 9–12 s after the beginning of flashes, at the frequencies of 10 and 16 Hz, it was recorded within 3–6 and 3 s, respectively.     

Combined mapping of human auditory EEG and MEG responses

Auditory electric and magnetic P50(m), N1(m) and MMN(m) responses to standard, deviant and novel sounds were studied by recording brain electrical activity with 25 EEG electrodes simultaneously with the corresponding magnetic signals measured with 122 MEG gradiometer coils. The sources of these responses were located on the basis of the MEG responses; all were found to be in the supratemporal plane. The goal of the present paper was to investigate to what degree the source locations and orientations determined from the magnetic data account for the measured EEG signals. It was found that the electric P50, N1 and MMN responses can to a considerable degree be explained by the sources of the corresponding magnetic responses. In addition, source-current components not detectable by MEG were shown to contribute to the measured EEG signals.     

Facial EMG responses to odors in solitude and with an audience

Two experiments were undertaken to examine whether facial responsesto odors correlate with the hedonic odor evaluation. Experiment1 examined whether subjects (n = 20) spontaneously generatedfacial movements associated with odor evaluation when they aretested in private. To measure facial responses, EMG was recordedover six muscle regions (M. corrugator supercilii, M. procerus,M. nasalis, M. levator, M. orbicularis oculi and M. zygomaticusmajor) using surface electrodes. In experiment 2 the experimentalgroup (n = 10) smelled the odors while they were visually inspectedby the experimenter sitting in front of the test subjects. Thecontrol group (n = 10) performed the same experimental conditionas those subjects participating in experiment 1. Facial EMGover four mimetic muscle regions (M. nasalis, M. levator, M.zygomaticus major, M. orbicularis oculi) was measured whilesubjects smelled different odors. The main findings of thisstudy may be summarized as follows: (i) there was no correlationbetween valence rating and facial EMG responses; (ii) pleasantodors did Dot evoke smiles when subjects smelled the odors inprivate; (iii) in solitude, highly concentrated malodors evokedfacial EMG reactions of those mimetic muscles which are mainlyinvolved in generating a facial display of disgust; (iv) thosesubjects confronted with an audience showed stronger facialreactions over the periocular and cheek region (indicative ofa smile) during the smelling of pleasant odors than those wbosmelled these odors in private; (v) those subjects confrontedwith an audience showed stronger facial reactions over the M.nasalis region (indicative of a display of disgust) during thesmelling of malodors than those who smelled the malodors inprivate. These results were taken as evidence for a more socialcommunicative function of facial displays and strongly mitigatesthe reflexive-hedonic interpretation of facial displays to odorsas supposed by Steiner.     

Topographical EEG Mapping in a Case of Recurrent Sleep Terrors

Sleep terrors are characterized by marked CNS arousal and typically occur during stage 3-4 sleep within the first NREM cycle. Studies of the EEG during sleep terrors suggest that delta power and synchrony in the EEG may be important physiological markers of sleep terror presence and intensity. An EEG mapping study was undertaken with a single participant who experienced three sleep terror episodes in the laboratory. A one-minute section of EEG was sampled immediately prior to the onset of each of the three sleep terrors. Similar EEG sections were taken from 10 healthy sex- and age-matched controls. The sleep tenors and control (normative) data were then compared topographically with z-scores (z-mapping). The z-maps indicated that all three sleep terrors contained more total and delta power in central and frontal areas than the control EEG sections. Moreover, relative delta power in these areas for the three sleep terrors was proportional to the subjective intensity of the episode. Although this pre-arousal EEG pattern may be related to ongoing slow-wave sleep mentation that may sometimes trigger sleep terror episodes, its functional significance remains an open question. The results demonstrate the utility of EEG mapping for the quantification of brain activation during sleep terror attacks and suggest that discrete activity profiles are identifiable for different types of dreaming-related arousal.     

Modification of responses of newly hatched snails by exposure to odors during development

Predatory marine snail larvae and embryos were exposed to preyodors (oyster, mussel and barnacle) during development. Whenjuvenile snails hatched they were tested by bioassay to determineeffects of this prior odor exposure. Juvenile snails were testedwith oyster, mussel and barnacle odors and with partially purifiedbarnacle odor of known attractiveness. Independent of priorodor exposure, only solutions containing barnacle odor wereattractive. Snails exposed during development to prey odorsnot in themselves attractive were more responsive to barnacleodors than snails that developed in barnacle odors. Snails notexposed to prey odors during development were intermediate intheir responsiveness. Field bioassays showed detectable attractantlevels in an environment containing barnacles. Attractant activitywas not detected in an environment where barnacles were absent.Responses of snails that developed in field odor conditionswere similar to those of snails that developed in the presenceof barnacles. Odor exposure during development is importantin determining future responses of these predatory snails toprey odors. ¹Duke University Marine Laboratory, Pivers Island, Beaufort,NC 28516, USA ²University of Miami RSMAS/MAC 4600 Rickenbacker Causeway, Miami,FL 33149, USA ³Suffolk University, Department of Biology, Beacon Hill, Boston,MA 02114, USA     

Mapping the semantic space for the subjective experience of emotional responses to odors

Two studies were conducted to examine the nature of the verbal labels that describe emotional effects elicited by odors. In Study 1, a list of terms selected for their relevance to describe affective feelings induced by odors was assessed while participants were exposed to a set of odorant samples. The data were submitted to a series of exploratory factor analyses to 1) reduce the set of variables to a smaller set of summary scales and 2) get a preliminary sense of the differentiation of affective feelings elicited by odors. The goal of Study 2 was to replicate the findings of Study 1 with a larger sample of odorant samples and participants and to validate the preliminary model obtained in Study 1 by using confirmatory factor analysis. Overall, the findings point to a structure of affective responses to odors that differs from the classical taxonomies of emotion such as posited by discrete or bidimensional emotion theories. These findings suggest that the subjective affective experiences or feelings induced by odors are structured around a small group of dimensions that reflect the role of olfaction in well-being, social interaction, danger prevention, arousal or relaxation sensations, and conscious recollection of emotional memories.     

Antennal and locomotor responses to attractive and aversive odors in the searching cockroach

The behavioral responses to attractive and aversive odors were examined in blinded adult male cockroaches under tethered-walking conditions. A sex pheromone-like stimulant derived from adult virgin females and artificially synthesized limonene were used as attractive and aversive odor sources, respectively. When a searching animal was stimulated with the attractive female-derived odor, the horizontal deflections of both the antennae were increased, and in most cases the vertical antennal positions were shifted downward. The stimulation also significantly decreased the walking speed of the animal. These behavioral changes imply a careful search in the immediate surroundings. The aftereffect of the sex pheromone was more pronounced on locomotion than on antennal movement. On the other hand, stimulation with the aversive odor (limonene) tended to suppress active antennal movement, and also increased the walking speed. Immediately after the withdrawal of the aversive odor, the active movement of the antennae was resumed, and the walking speed rapidly decreased to a level approximately the same as that of the control period. These results indicate that the responses to the qualitatively opposite types of odor are reciprocal to each other with regard to both antennal movement and locomotion.     

Remote detection of algae by copepods: responses to algal size, odors and motility

Selective feeding on large algae by copepods involves remotedetection of individual particles and subsequent active captureresponses In this study we use radiotracer experiments to quantifythe clearance rates of five coexisting freshwater copepods andto investigate the relative merits of the chemoreception andmechanoreception hypotheses of remote detection Tropocyclopsand three diaptomid copepods exhibited relatively high clearancerates when feeding on low concentrations of large algae, suggestingthat most previous studies with freshwater copepods have underestimatedmaximal clearance rates and the degree of size selectivity.All five species of copepods exihibited strong selection foran intermediate-sized flagellate (25 µm Cartena) or alarge-sized nonmotile alga (80 µ.m Pediastrum) over asmall-sized flagellate (6 µ.m Chlamydomonas). The weight-specificclearance rate for Tropocylops prasmus feeding on motile Cartena(271 ml mg^–1 h^–1) was about twice that of threediaptomid copepods and more than an order-of-magnitude higherthan the estimate for Epischura lacustris feeding on its preferredalga, Pediastrum Assuming that distance chemoreception (‘smell’)is important in remote detection, we predicted that the additionof high concentrations of ‘algal odors’ would obscureany chemical gradients emanating from individual algal cellsand would thereby hinder the remote detection and active captureof large algae Contrary to this hypothesis, the addition ofamino acids, sucrose, and algal extracts had no effect on theclearance rates and selectivity of Diaptomus birgei. These results,together with recent cinematographic studies (Vanderploeg etal.,1990), suggest that mechanoreception is the primary mechanismfor the remote detection of large particles by diaptomid copepods.A raptorial cyclopoid, Tropocyclops prasinus, exhibited strongpreferences for motile algae, whereas a suspension-feeding calanoid,D birgei, did not select between motile and nonmotile cells.Motility appears to be an important factor in algal detectionfor small cyclopoid copepods but not for suspension-feedingdiaptomids     

Olfactory responses of Aphidius gifuensis to odors of host plants and aphid‐plant complexes

Abstract The olfactory responses of Aphidius gifuensis to odors from two host plants (Nicotiana tabacum and Brassica napus ssp.) and their complexes with different infestation levels of two host aphids (Myzus persicae and Lipaphis erysimi) were respectively examined in an olfactometer. The results showed that female A. gifuensis did not respond to odors of undamaged or mechanically damaged host plants, but significantly responded to odors of aphid/plant complexes. Moreover, A. gifuensis responded significantly to odors of both M. persicae and L. erysimi/plant complexes when host plants were infested by high levels of aphids, suggesting that quantity of aphid‐induced volatiles could be important for attracting A. gifuensis. When tested between aphid/plant complexes, A. gifuensis did not show its preference for either complex. The efficiency of A. gifuensis against aphids in open fields potentially could be improved by using its olfactory response to aphid/plant complexes.     

Individual differences in thresholds and quality reports of human subjects to various odors

Sixty-three subjects were selected on the basis of their relativeability (n = 30) or inability (n = 33) to detect the intenseurine–sweaty odor of the diastereoisomeric ketone, cis-4-(4'-t-butylcyclohexyl)-4-methyl-2-pentanone (pemenone). Absolute thresholds were determined,and quality reports and hedonic ratings were obtained for near-thresholdconcentrations of pemenone and five other odorous compounds.Several of these compounds were selected because large individualdifferences in sensitivity (specific anosmias) were known toexist. A principal compound analysis of threshold concentrationsindicated that three orthogonal factors well described the relationshipsbetween sensitivities to the compounds. Threshold concentrationsof pemenone and androstenone were highly correlated and thefirst factor was defined by relationships between those odorantsand isovaleric acid, all modally putrid-smelling compounds.Subjects relatively osmic for pemenone generally reported aputrid odor for pemenone, but anosmics reported mostly otherqualities. These relationships between relative sensitivityand the quality reports elicited by the different compoundsare consistent with a multiple-profile model of odor qualityperception. That model postulates that most odor molecules interactwith more than one perceptual channel (receptor process) andthat any individual alteration in the relative specificity ordeletion in the number of such receptor processes could alterthe pattern of interaction and thus should give rise to alterationsin the quality or intensity of the resulting odor perception.     

Differential endocrine responses to infant odors in common marmoset (Callithrix jacchus) fathers

Olfactory cues can exert priming effects on many mammalian species. Paternally experienced marmosets, Callithrix jacchus, exposed to direct isolated olfactory contact with their own infant's scent show rapid decreases in testosterone levels within 20 min, whereas paternally inexperienced males do not. The following study tests whether there is a differential steroid response to exposure of infant scent from dependent infants (own and novel) and independent infants (own and novel). We examined the serum levels of estradiol, estrone, testosterone, dihydrotestosterone (DHT), and combined estrogens and androgens in eight male marmosets 20 min after exposure to isolated infant scent. Testosterone and androgen levels combined were significantly lower with exposure to own infant scent than a novel infant scent when the infants were at a dependent age but not at an independent age. Estrogen levels elevated significantly in response to own infant scent when the infants were at a dependent age but not at an independent age. These results suggest that marmoset fathers are more responsive to priming cues from related infants and hormonal responses from fathers are greatest when the infant is at a dependent age.     

A human SHC-related sequence maps to chromosome 17, the SHC gene maps to chromosome 1

The SHC gene encodes a protein that is thought to act as an adapter in many signal transduction pathways; the SHC protein probably facilitates the activation of RAS proteins in response to a variety of factors. We have mapped the human SHC gene and have identified a new SHC-related sequence. We have sequenced the region corresponding to the SHC 3 UTR from both loci and have mapped cosmids by fluorescence in situ hybridization. The human SHC gene maps to the proximal long arm of chromosome 1 and the SHC-related sequence maps to the proximal long arm of chromosome 17. A number of cancers have been positioned in the proximal long arm of chromosome 1; this is of interest given the oncogenic potential of the SHC protein.     

Attention and regulation of EEG alpha-attenuation responses

Two experiments with 16 normal adults of both sexes tested the hypothesis that inattention to a biofeedback display is associated with increased variability of those physiological processes that had been regulated by the biofeedback. Each experiment was a repeated-measures-on-independent-subjects-design. Dependent variables were the time durations and the mean rms power of two mutually exclusive segments of the parietal-occipital EEG: alpha and not-alpha segments. Independent variables were combination of counting tasks and instructions to look at, listen to, and count visual and auditory flashes and clicks. The durations of alpha and not-alpha segments were controlled or regulated by means of an alpha-contingent visual feedback stimulus, Attention to the feedback stimulus was challenged by instructions to count other, noncontingent stimuli. Control of alpha and not-alpha segments was least for conditions of (1) “sham” feedback, and (2) feedback with instructions to count noncontingent auditory clicks, which were presented 3/sec while the feedback visual stimuli were occurring. A new EEG test of attention and distraction was suggested.