Olfactory adaptation and recovery in man as measured by two psychophysical techniques

Olfactory adaptation and recovery was investigated in man, using two psychophysical procedures: modified category scaling and threshold detection. Both procedures yielded similar qualitative information regarding loss and recovery of olfactory sensitivity as a function of time and concentration of adapting stimuli. However, quantitative differences were observed that could be partially attributed to artifacts inherent in each procedure. Often more than 50% adaptation (and recovery) occurred within the first 2 min with either test procedure. In all experiments the rate of adaptation and recovery was greater at the higher of two adapting concentrations (10 × and 20 × the detection threshold I_t). Recovery occurred more rapidly than adaptation. The usefulness of both techniques is discussed in terms of the overall problem of characterizing the olfactory adaptation and recovery process in man.     

Autoshaping as a psychophysical paradigm: Absolute visual sensitivity in the pigeon

A classical conditioning procedure (autoshaping) was used to determine absolute visual threshold in the pigeon. This method provides the basis for a standardized visual psychophysical paradigm.     

Olfactory dysfunction in man: anatomical and behavioral aspects

We reviewed studies examining the olfaction of patients with brain damage for the purpose of discerning correlations between disordered structure and function. Patient samples included those with neurological disorders and neurosurgical interventions and recording of spontaneous or elicited neuronal activity. Brain areas involved in olfaction include the olfactory bulbs, the orbitofrontal and medial temporal cortices, the thalamus, and the amygdala. Despite recent advances in olfactory anatomy, understanding of how these structures are related to olfactory detection, discrimination, and recognition continues to be limited. Inadequate localization of brain lesions and lack of comprehensive behavioral assessment have thus far prevented a detailed account of the organization of olfaction in the human brain.     

Olfactory detection thresholds in man under conditions of rest and exercise

Detection thresholds for seilen odorants were measured under conditions of rest and exercise. The test panel comprised six males with previous experience in odor detection. Exercise was maintained constant by using a modified bicycle positioned within the context of an air-dilution olfactometer. The effects of exercise were idiosyncratic for Ss: odor sensitivity was increased in some Ss, decreased in some, and not changed in others. Results of these experiments are discussed in terms of intra-subject variance within sessions and from session to session. In addition, two test techniques—one a fixed series and the other a tracking procedure—were evaluated for rapid estimation of an odor threshold. The tracking procedure facilitated prompt detection of changes in sensitivity for individual Ss.     

Changes in psychophysical parameters in relation to computer screen control work sites

Exceptionally high demands on the psychonervous system of those engaged in certain regulatory capacities at the fluorescent screen are the order of the day. In such work, reliability of performance depends on the state of activation of the ions. Findings from the simultaneous measurement of critical fusion frequency and heartbeat frequency can be used to map out the state of activation of the ions. Optimum performance may be maintained at work for a period of up to five hours. After five hours under especially exacting working conditions, flicker frequency and heartbeat frequency were found to go into opposing phases.     

On the psychophysical law and estimation procedures in psychophysical scaling

A general formulation of the power law is presented which has two special features: (1) negative exponents are admissible; and (2) the log law is a special limiting case. Estimation procedures, which provide joint estimates of the exponent and the absolute threshold, are derived for the direct ratio scaling methods. A solution is provided for theaveraging problem for ratio production and bisection scaling, two methods generating observations on the physical scale, and Monte Carlo methods are used to evaluate the resulting estimators.     

Adaptive psychophysical procedures, loss functions, and entropy

In this article, we present a new strategy for locating a point on a psychometric function (threshold determination) for yes-no procedures, called EntFirst. Our results show that it performs better than many existing strategies for estimating the 50% threshold that are commonly used in nonlaboratory settings. We also provide a review of existing algorithms for finding thresholds, with an emphasis on identifying the types of problems for which each algorithm is useful. Finally, we address a number of issues that are not adequately covered in the literature, including choosing an appropriate loss function to evaluate the performance of an algorithm for a given problem.     

Monotonicity,convexity, and other qualitative psychophysical laws

General methods are described for directly testing qualitative psychophysical laws, such as monotonicity and convexity. These methods consist of estimating lower and higher orders of derivatives and procedures for verifying qualitative laws involving these derivatives. The quantitative power law hypothesis is compared for goodness of fit with the qualitative hypothesis that the psychophysical function is monotone and convex, in application to bisection brightness data. Other topics include discussion of a possible topological formulation of the distinction between qualitative and quantitative laws; the search for psychophysical invariants; and the failure of qualitative laws such as convexity to conform to Luce's invariance-theoretic principles of theory construction.     

Marking, memory and superstition in the pigeon

Learning is generally poor if reinforcement is delayed, but it improves substantially if a brief stimulus is presented immediately after the response to be learned. The marking hypothesis suggests that the unexpected stimulus triggers a backward memory search, which effectively marks the preceding response in memory, making it more likely that it will be recalled when food is presented. In the present study, pigeons were occasionally reinforced after a 10-sec delay for pecking a split key. Reinforcement was presented regardless of which side was pecked, but for one group a marker followed a peck to the left half of the key during the delay preceding food, and for the other group a peck to the right. On non food trials these contingencies were reversed. Subjects developed a significant preference for the side marked on food trials, despite the absence of any contingency between responding to this side and food. In addition to providing further support for the marking hypothesis, these results favour theories of reinforcement emphasizing contiguity rather than contingency. Contiguity, however, needs to be interpreted within a memory framework. What is crucial is the contiguity of events within working memory, rather than in the real world.     

Weber laws,the Weber law,and psychophysical analysis

In failing to define the units in which the stimulus is to be measured, the Weber law might seem to make no definite assertion, and indeed, it is shown that any single empirical function, supposed to relate a given stimulus intensity with that intensity which is just noticeably greater, can be put into the Weber form by a suitable change of scale in which the stimulus intensity is to be measured. Nevertheless, it turns out that if different individuals have different Weber functions, when the intensities are measured on a given scale, then it is by no means always possible to transform the scale so that all of the functions can take on the Weber form. Some necessary conditions are given for the possibility of such a transformation when there is at hand a finite number of functions, and when the functions depend upon a single parameter the necessary and sufficient condition is easily derived. The same discussion leads to a generalization of Thurstone's psychophysical scale and shows that such a scale is always possible.     

Olfactory stimulation induces filial preferences for huddling in rat pups.

Rat pups of all ages huddle with conspecifics, but the senosory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present experiments indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in pups from both scented and nonscented litters. Pups from scented nests preferred to huddle with a scented stimulus rat, whereas control pups preferred a nonadulterated rat stimulus. Additional testing indicated that the affiliative preferences were specific to rearing odor and were not based on decreased aversion to test scents, or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation.     

Olfactory fear conditioning induces field potential potentiation in rat olfactory cortex and amygdala

The widely used Pavlovian fear-conditioning paradigms used for studying the neurobiology of learning and memory have mainly used auditory cues as conditioned stimuli (CS). The present work assessed the neural network involved in olfactory fear conditioning, using olfactory bulb stimulation-induced field potential signal (EFP) as a marker of plasticity in the olfactory pathway. Training consisted of a single training session including six pairings of an odor CS with a mild foot-shock unconditioned stimulus (US). Twenty-four hours later, the animals were tested for retention of the CS as assessed by the amount of freezing exhibited in the presence of the learned odor. Behavioral data showed that trained animals exhibited a significantly higher level of freezing in response to the CS than control animals. In the same animals, EFPs were recorded in parallel in the anterior piriform cortex (aPC), posterior piriform cortex (pPC), cortical nucleus of the amygdala (CoA), and basolateral nucleus of the amygdala (BLA) following electrical stimulation of the olfactory bulb. Specifically, EFPs recorded before (baseline) and after (during the retention test) training revealed that trained animals exhibited a lasting increase (present before and during presentation of the CS) in EFP amplitude in CoA, which is the first amygdaloid target of olfactory information. In addition, a transient increase was observed in pPC and BLA during presentation of the CS. These data indicate that the olfactory and auditory fear-conditioning neural networks have both similarities and differences, and suggest that the fear-related behaviors in each sensory system may have at least some distinct characteristics.