Biomedical subjects

R P Akers

Publications and source records attributed to R P Akers.

4 recordsLinked to original sources

PubMed1997

Coding properties of peak and average response rates in American cockroach olfactory sensory cells.

The response of phasic neurons is often measured in terms of average spiking rates over arbitrarily selected time intervals. Averages taken over inappropriate intervals may severely reduce the information content of data, as we show here using response data from female American cockroach peripheral olfactory cells. We demonstrate that a 100-ms period around the peak response contains the best information for discriminating among odors at moderate to high concentrations. Further, the 100-ms post-peak response period contains the best information at low concentrations, as well as in situations where it is important to minimize errors in misidentifying the quality of an odor. Averaging the data over the full 0.5 s stimulus period degrades the odor separation qualities of the data.

Action Potentials↗

PubMed1995

Partitioning non-linearities in the response of honey bee olfactory receptor neurons to binary odors.

In many organisms, of which honey bees are one example, a general (i.e., non-pheromonal) olfactory receptor neuron may respond to some odorants by increasing its firing rate and to others by decreasing its firing rate. In the latter case, this decrease will be with respect to a background firing rate determined by intrinsic (internal noise) and extrinsic (background odors) factors. To analyse receptor neurons of this complexity, we extend Beidler's model of receptor protein activation dynamics to account for the competition between depolarizing and hyperpolarizing pathways and couple the model to a phenomenological description of the non-linear relationship between the proportion of activate membrane receptors and the receptor cell spike generation rates. We then examine the implications of this theory for predicting the response of receptor neurons to odor mixtures based on their response to pure odorants at concentrations matched to the mixture. We derive inequalities that must be satisfied under our normative model, and propose that deviations from the model be designated as synergisms and inhibitions, depending on the direction in which various equalities and inequalities are violated. We then apply our inequalities to identifying synergisms and inhibitions in data analysed in a different way elsewhere (Akers, R.P. and Getz, W.M. Response of olfactory receptor neurons in honey bees to odorants and their binary mixtures. J. Comp. Physiol. (in press)). In these data regarding the response of honey bee placode sensilla to a number of odorants and their binary combinations, we demonstrate the presence of synergisms and inhibitions--that is, elevated or repressed responses that are not due to competitive interactions of mixture component odorants for receptor sites or Beidler (Beidler, L.M., 1962. Taste receptor stimulation. Prog. Biophys. Biophys. Chem. 12, 107-151) saturation mechanisms.

Animals↗

PubMed1994

Honeybee olfactory sensilla behave as integrated processing units.

Honeybee placode sensilla contain 18-35 olfactory receptor neurons. In insects, such neurons are thought to not interact with one another before reaching the central nervous system. Extracellular, multiunit recordings were made from the placodes and separated into spike shape classes, termed subplacode units. An analysis of the response spectra of subplacode units demonstrated that subplacode units with similar response spectra were more likely to be found in different placodes than in the same placode. An analysis was made of the mean interspike intervals and its variation for whole placodes and subplacode units. The coefficient of variation for whole placodes was less than that for subplacode units. Whole placode spike trains are therefore more uniform than subplacode spike trains, indicating that neurons might not be firing independently of each other.

Animals↗

PubMed1988

The contribution of olfactory receptor neurons to the perception of pheromone component ratios in male redbanded leafroller moths.

(Z)-11-tetradecenyl acetate (Z-11, 14:AC) must be in a 100:9 ratio with (E)-11-tetradecenyl acetate (E-11,14:AC) to produce maximal wing fanning and attraction in male redbanded leafrollers. Earlier electrophysiological studies had indicated that mixtures of these pheromone components elicited responses from olfactory receptor neurons that appeared to differ from those expected on the basis of the responses to the individual components. Here we evaluate whether the behavioral sensitivity to particular ratios of Z- and E-11,14:AC has a correlate in the response properties of olfactory receptor neurons. The stimuli included the ratios of Z- and E-11,14:AC used in earlier behavioral work plus several different mixtures of the seven components found in the pheromone blend, and equivalent amounts of the individual components. These stimuli were presented over a range of intensities to individual trichoid sensilla on the male antenna. In common with earlier results, the receptor neuron with the larger amplitude action potential responded most strongly to Z-11,14:AC, whereas the companion receptor neuron in the sensillum responded most strongly to E-11,14:AC. In contrast with earlier results, each receptor neuron responded exclusively to its own most effective stimulus, without regard to the presence of any other compound. They failed to respond uniquely to any of the other five compounds in the female pheromone blend, or to any of the tested combinations of these compounds. These minor components also failed to modulate the responses elicited in receptor neurons by appropriate ratios of Z- and E-11,14:AC. Thus, the responses of the two types of olfactory receptor neurons found in trichoid sensilla failed to show an optimum at the pheromone ratio known to elicit peak behavioral activity.

Action Potentials↗