Search PubMed⌕ Search

Biomedical subjects

Alan Gelperin

Publications and source records attributed to Alan Gelperin.

9 recordsLinked to original sources
PubMed2006

Sparse odor coding in awake behaving mice.

Responses of mitral cells represent the results of the first stage of odor processing in the olfactory bulb. Most of our knowledge about mitral cell activity has been obtained from recordings in anesthetized animals. We compared odor-elicited changes in firing rate of mitral cells in awake behaving mice and in anesthetized mice. We show that odor-elicited changes in mitral cell firing rate were larger and more frequently observed in the anesthetized than in the awake condition. Only 27% of mitral cells that showed a response to odors in the anesthetized state were also odor responsive in the awake state. The amplitude of their response in the awake state was smaller, and some of the responses changed sign compared with their responses in the anesthetized state. The odor representation in the olfactory bulb is therefore sparser in awake behaving mice than in anesthetized preparations. A qualitative explanation of the mechanism responsible for this phenomenon is proposed.

Anesthesia↗
PubMed2006

A neuronal network for the logic of Limax learning.

We construct a neuronal network to model the logic of associative conditioning as revealed in experimental results using the terrestrial mollusk Limax maximus. We show, in particular, how blocking to a previously conditioned stimulus in the presence of the unconditional stimulus, can emerge as a dynamical property of the network. We also propose experiments to test the new model.

Action Potentials↗
PubMed2006

Speed-accuracy tradeoff in olfaction.

The basic psychophysical principle of speed-accuracy tradeoff (SAT) has been used to understand key aspects of neuronal information processing in vision and audition, but the principle of SAT is still debated in olfaction. In this study we present the direct observation of SAT in olfaction. We developed a behavioral paradigm for mice in which both the duration of odorant sampling and the difficulty of the odor discrimination task were controlled by the experimenter. We observed that the accuracy of odor discrimination increases with the duration of imposed odorant sampling, and that the rate of this increase is slower for harder tasks. We also present a unifying picture of two previous, seemingly disparate experiments on timing of odorant sampling in odor discrimination tasks. The presence of SAT in olfaction provides strong evidence for temporal integration in olfaction and puts a constraint on models of olfactory processing.

Animals↗
PubMed2006

Olfactory neuronal dynamics in behaving animals.

More than 50 years have passed since the first recording of neuronal responses to an odor stimulus from the primary olfactory brain area, the main olfactory bulb. During this time very little progress has been achieved in understanding neuronal dynamics in the olfactory bulb in awake behaving animals, which is very different from that in anesthetized preparations. In this paper we formulate a new framework containing the main reasons for studying olfactory neuronal dynamics in awake animals and review advances in the field within this new framework.

Anesthesia↗
PubMed2005

DNA-decorated carbon nanotubes for chemical sensing.

We demonstrate a new, versatile class of nanoscale chemical sensors based on single-stranded DNA (ss-DNA) as the chemical recognition site and single-walled carbon nanotube field effect transistors (swCN-FETs) as the electronic read-out component. swCN-FETs with a nanoscale coating of ss-DNA respond to gas odors that do not cause a detectable conductivity change in bare devices. Responses of ss-DNA/swCN-FETs differ in sign and magnitude for different gases and can be tuned by choosing the base sequence of the ss-DNA. ss-DNA/swCN-FET sensors detect a variety of odors, with rapid response and recovery times on the scale of seconds. The sensor surface is self-regenerating: samples maintain a constant response with no need for sensor refreshing through at least 50 gas exposure cycles. This remarkable set of attributes makes sensors based on ss-DNA decorated nanotubes very promising for "electronic nose" and "electronic tongue" applications ranging from homeland security to disease diagnosis.

Base Sequence↗
PubMed2004

Volatile metabolic monitoring of glycemic status in diabetes using electronic olfaction.

The increased incidence of Type I and Type II diabetes among adults and adolescents is a growing public health concern worldwide. The primary objective of diabetes mellitus management involves keeping glycemia levels within the euglycemic range to prevent a variety of serious health complications. Unfortunately, daily self-monitoring is both a requirement and a problem for many patients with diabetes, particularly children and adolescents. Studies have shown that as many as 43% of adolescents and 30% of children (<14 years old) regularly forget to use glycemic tests and are significantly poorer at recognizing and reporting symptoms and signs of hypoglycemia/hyperglycemia. For this reason, methods for noninvasive, continuous monitoring that can signal glycemic status to a parent, teacher, or other caregiver would improve the care and management of symptoms of diabetes among these individuals. The goal of this review is to describe and evaluate electronic olfaction technology ("electronic nose") for monitoring the presence and levels of volatile chemicals from human body and breath that can be used to evaluate status of diabetes. The review is organized in four sections. The first section reviews the chemistry of the volatile signals that are produced by the body that are indicative of metabolic status. The second section provides an overview of novel sensor technology, e.g., "electronic olfaction," that mimics the biological olfactory system and can be used to monitor and identify complex plumes of volatiles that are signatures of metabolic states. The third section reviews studies that have employed electronic "nose" technology for diagnosis and monitoring of diabetes via urine and breath, and the final section discusses needed future directions for the development of olfactory-based metabolic monitoring, particularly among noncompliant populations.

Adolescent↗
PubMed2002

The nitric oxide/cyclic GMP pathway in the olfactory processing system of the terrestrial slug Limax marginatus.

To examine the distribution of nitric oxide (NO)-generative cells and NO-responsive cells in the tentacles and procerebral lobes (olfactory processing center) of terrestrial slugs, we applied NADPH diaphorase (NADPH-d) histochemistry and NO-induced cyclic GMP (cGMP)-like immunohistochemistry. We found that NADPH-d reactive cells/fibers and cGMP-like immunoreactive cells/fibers were different, but they were localized adjacent to each other, in both the tentacles and the procerebral lobes. Then, we measured the concentration of NO that was generated around the procerebral lobes using an NO sensitive electrode, when the olfactory nerve was electrically stimulated as a replacement for an odorant stimulus. Stimulation of the olfactory nerve evoked an increase in NO concentration at nanomolar levels, suggesting that binding of nanomolar concentrations of NO to the prosthetic heme group activates soluble guanylyl cyclase. Taken together with previously reported physiological data, our results, therefore, showed that the NO/cGMP pathways are involved in slug olfactory processing.

Animals↗
PubMedDate not supplied

Model for transition from waves to synchrony in the olfactory lobe of Limax.

A biophysical model for the interactions between bursting (B) cells and nonbursting (NB) cells in the procerebral lobe of Limax is developed and tested. Phase-sensitivity of the NB cells is exhibited due to the strong inhibition from the rhythmically bursting B cells. Electrical and chemical junctions coupled with a parameter gradient lead to sustained periodic waves in the lobe. Excitatory interactions between the NB cells, which rarely fire, lead to stimulus evoked synchrony in the lobe oscillations. A novel calcium current is suggested to explain the effects of nitric oxide (NO) on the lobe. Gap junctions are shown both experimentally and through simulations to be required for the oscillating field potentials.

Action Potentials↗