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Leslie M Kay

Publications and source records attributed to Leslie M Kay.

10 recordsLinked to original sources
PubMed2006

An argument for an olfactory thalamus.

The mammalian olfactory system is unique in that sensory receptors synapse directly into the olfactory bulb of the forebrain without the thalamic relay that is common to all other sensory pathways. We argue that the olfactory bulb has an equivalent role to the thalamus, because the two regions have very similar structures and functions. Both the thalamus and the olfactory bulb are the final stage in sensory processing before reaching target cortical regions, at which there is a massive increase in neuron and synapse numbers. Thus, both structures act as a bottleneck that is a target for various modulatory inputs, and this arrangement enables efficient control of information flow before cortical processing occurs.

Animals↗
PubMed2006

When good enough is best.

In this issue of Neuron, Rinberg et al. show that mice use a speed-accuracy tradeoff in odor discrimination. Shorter sampling results in high performance for easy problems, and enforced longer sampling results in higher accuracy for difficult problems, but mice freely choose intermediate sampling durations and accuracy varies with difficulty. Reward value and task requirements may determine sampling time choice and performance levels.

Animals↗
PubMed2006

Grading odor similarities in a Go/No-Go task.

Recent studies show that some features of odor perception are predicted by olfactory receptor biophysics and olfactory bulb physiology. Those studies used a behavioral assay in which rodents dig in a dish of scented cage bedding after pretraining to associate a buried reward with an odorant. The advantage of the digging task is an intensity measure of similarity (number of seconds spent digging). The method has the disadvantages of odorant contamination and low control over concentration and timing, making it difficult to use in electrophysiology. We describe an operant task that avoids these disadvantages and provides a reliable intensity-based similarity measure. Odorants can be delivered with a standard air dilution olfactometer, and rats learn to lever press to one odorant and avoid pressing to another in a Go/No-Go (CS+/CS-) task with a partial reinforcement protocol. Generalization tests substitute a portion of the unrewarded CS+ trials with test odorants. The number of generalization trials on which a subject responds to a test odorant is the measure of odor similarity intensity. We present validation tests using mixture component recognition, which show high repeatability, little variability across subjects and no decrease in responding across sessions. The results match those obtained with the digging task in four of five mixtures tested. This method allows optimal control over stimulus parameters and is compatible with simultaneous electrophysiological recording.

Animals↗
PubMed2006

Information processing in the olfactory systems of insects and vertebrates.

Insects and vertebrates separately evolved remarkably similar mechanisms to process olfactory information. Odors are sampled by huge numbers of receptor neurons, which converge type-wise upon a much smaller number of principal neurons within glomeruli. There, odor information is transformed by inhibitory interneuron-mediated, cross-glomerular circuit interactions that impose slow temporal structures and fast oscillations onto the firing patterns of principal neurons. The transformations appear to improve signal-to-noise characteristics, define odor categories, achieve precise odor identification, extract invariant features, and begin the process of sparsening the neural representations of odors for efficient discrimination, memorization, and recognition.

Animals↗
PubMed2005

Theta oscillations and sensorimotor performance.

Performance and cognitive effort in humans have recently been related to amplitude and multisite coherence of alpha (7-12 Hz) and theta (4-7 Hz) band electroencephalogram oscillations. I examined this phenomenon in rats by using theta band oscillations of the local field potential to signify sniffing as a sensorimotor process. Olfactory bulb (OB) theta oscillations are coherent with those in the dorsal hippocampus (HPC) during odor sniffing in a two-odor olfactory discrimination task. Coherence is restricted to the high-frequency theta band (6-12 Hz) associated with directed sniffing in the OB and type 1 theta in the HPC. Coherence and performance fluctuate on a time scale of several minutes. Coherence magnitude is positively correlated with performance in the two-odor condition but not in extended runs of single odor conditional-stimulus-positive trials. Simultaneous with enhanced OB-HPC theta band coherence during odor sniffing is a significant decrease in lateral entorhinal cortex (EC)-HPC and OB-EC coherence, suggesting that linkage of the olfactory and hippocampal theta rhythms is not through the synaptic relay from OB to HPC in the lateral EC. OB-HPC coupling at the sniffing frequency is proposed as a mechanism underlying olfactory sensorimotor effort as a cognitive process.

Animals↗
PubMed2005

A redefinition of odor mixture quality.

Odor mixtures are perceived as different from (configural) or the same as (elemental) their components. Recent studies (L. M. Kay, C. A. Lowry, & H. A. Jacobs, 2003; C. Wiltrout, S. Dogra, & C. Linster, 2003) propose that component structural or perceptual similarities predict configural properties of binary mixtures. The authors evaluated this in rats using 4 binary mixtures with varying structural similarity (eucalyptol-benzaldehyde, eugenol-benzaldehyde, octanol-octanal, and [+/-]-limonene). The range of tested ratios for each mixture was determined by the components' vapor pressures. Three results are presented: (a) No mixture maintains purely elemental or configural properties for all concentration ratios, (b) structural similarity or dissimilarity does not predict configural or elemental perception, and (c) overshadowing is significant in responses to all odor sets. The authors offer more precise definitions of elemental and configural properties and overshadowing as they relate to odor mixture perception.

Animals↗
PubMed2003

Receptor contributions to configural and elemental odor mixture perception.

Odor mixture perception can be configural (the mixture is qualitatively different from the components) or elemental (the components are recognizable). Some have argued that configural properties are dependent on chemical similarity and possible overlap at the receptor level. The authors show that a binary mixture in which both components activate the same receptor (17) has a configural odor, whereas a mixture that suppresses overlap has elemental odor properties. Rats trained to recognize mixtures of citronellal and octanal (strong 17 agonists) in many ratios rarely recognize the components, supporting configural representation of the odor mixture. However, when trained to recognize mixtures of citral (partial 17 agonist, inhibitor) and octanal, rats recognize 1 or both components over a wide range of ratios.

Acyclic Monoterpenes↗
PubMed2003

A challenge to chaotic itinerancy from brain dynamics.

Brain hermeneutics and chaotic itinerancy proposed by Tsuda are attractive characterizations of perceptual dynamics in the mammalian olfactory system. This theory proposes that perception occurs at the interface between itinerant neural representation and interaction with the environment. Quantifiable application of these dynamics has been hampered by the lack of definable history and action processes which characterize the changes induced by behavioral state, attention, and learning. Local field potentials measured from several brain areas were used to characterize dynamic activity patterns for their use as representations of history and action processes. The signals were recorded from olfactory areas (olfactory bulb, OB, and pyriform cortex) and hippocampal areas (entorhinal cortex and dentate gyrus, DG) in the brains of rats. During odor-guided behavior the system shows dynamics at three temporal scales. Short time-scale changes are system-wide and can occur in the space of a single sniff. They are predictable, associated with learned shifts in behavioral state and occur periodically on the scale of the intertrial interval. These changes occupy the theta (2-12 Hz), beta (15-30 Hz), and gamma (40-100 Hz) frequency bands within and between all areas. Medium time-scale changes occur relatively unpredictably, manifesting in these data as alterations in connection strength between the OB and DG. These changes are strongly correlated with performance in associated trial blocks (5-10 min) and may be due to fluctuations in attention, mood, or amount of reward received. Long time-scale changes are likely related to learning or decline due to aging or disease. These may be modeled as slow monotonic processes that occur within or across days or even weeks or years. The folding of different time scales is proposed as a mechanism for chaotic itinerancy, represented by dynamic processes instead of static connection strengths. Thus, the individual maintains continuity of experience within the stability of fast periodic and slow monotonic processes, while medium scale events alter experience and performance dramatically but temporarily. These processes together with as yet to be determined action effects from motor system feedback are proposed as an instantiation of brain hermeneutics and chaotic itinerancy.

Animals↗
PubMed2003

Two species of gamma oscillations in the olfactory bulb: dependence on behavioral state and synaptic interactions.

Gamma oscillations (40-100 Hz), originally seen in the olfactory bulb (OB), have long been a defining characteristic of sensory coding in the olfactory system. This study proposes that gamma oscillations are of two types, associated with different behavioral features and synaptic origins within the OB. Local field potentials were recorded from rat and mouse OBs during various behavioral periods (immobility, alert motionlessness, exploration and odor discrimination). High frequency gamma activity (65-100 Hz) is shown to be correlated with the sniff cycle, initiated at the peak of inhalation and is called type 1 gamma. It is prominent during exploratory behavior, but also present during resting and trained odor discrimination. Low frequency gamma activity (35-65 Hz), called type 2 gamma, is not strongly correlated with the sniff cycle, is inhibited by the sniff onset and is prominent during alert immobility. Rest and alert immobility are characterized by alternating type 1 and type 2 gamma rhythms, while exploratory sniffing and odor discrimination show a dramatic decrease in type 2 gamma with a broadband increase in the power of type 1 gamma. Periods of alert immobility prior to odor discrimination in trained animals show dominance of type 2 gamma, with episodes lasting up to 0.5 second. Data from mice with selective deletion of granule cell inhibition in the OB show a selective loss of type 2 gamma with type 1 gamma dramatically enhanced during exploratory behavior, suggesting that mutual inhibition between granule cells or centrifugal inhibitory input drives type 2 gamma, and that the excitatory-inhibitory connections between mitral and granule cells likely drive type 1 gamma. Gamma activity is not a single type of oscillation, and the largest amplitude gamma bursts are often those associated with an attentive cognitive state rather than odor sniffing.

Action Potentials↗