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D S Reich

Publications and source records attributed to D S Reich.

10 recordsLinked to original sources
PubMed2001

Independent and redundant information in nearby cortical neurons.

In the primary visual cortex (V1), nearby neurons are tuned to similar stimulus features, and, depending on the manner and time scale over which neuronal signals are analyzed, the resulting redundancy may mitigate deleterious effects of response variability. We estimated information rates in the short-time scale responses of clusters of up to six simultaneously recorded nearby neurons in monkey V1. Responses were almost independent if we kept track of which neuron fired each spike but were redundant if we summed responses over the cluster. Redundancy was independent of cluster size. Summing neuronal responses to reduce variability discards potentially useful information, and the discarded information increases with cluster size.

Action Potentials↗
PubMed2001

Formal and attribute-specific information in primary visual cortex.

We estimate the rates at which neurons in the primary visual cortex (V1) of anesthetized macaque monkeys transmit stimulus-related information in response to three types of visual stimulus. The stimuli-randomly modulated checkerboard patterns, stationary sinusoidal gratings, and drifting sinusoidal gratings-have very different spatiotemporal structures. We obtain the overall rate of information transmission, which we call formal information, by a direct method. We find the highest information rates in the responses of simple cells to drifting gratings (median: 10.3 bits/s, 0.92 bits/spike); responses to randomly modulated stimuli and stationary gratings transmit information at significantly lower rates. In general, simple cells transmit information at higher rates, and over a larger range, than do complex cells. Thus in the responses of V1 neurons, stimuli that are rapidly modulated do not necessarily evoke higher information rates, as might be the case with motion-sensitive neurons in area MT. By an extension of the direct method, we parse the formal information into attribute-specific components, which provide estimates of the information transmitted about contrast and spatiotemporal pattern. We find that contrast-specific information rates vary across neurons-about 0.3 to 2.1 bits/s or 0.05 to 0.22 bits/spike-but depend little on stimulus type. Spatiotemporal pattern-specific information rates, however, depend strongly on the type of stimulus and neuron (simple or complex). The remaining information rate, typically between 10 and 32% of the formal information rate for each neuron, cannot be unambiguously assigned to either contrast or spatiotemporal pattern. This indicates that some information concerning these two stimulus attributes is confounded in the responses of single neurons in V1. A model that considers a simple cell to consist of a linear spatiotemporal filter followed by a static rectifier predicts higher information rates than are found in real neurons and completely fails to replicate the performance of real cells in generating the confounded information.

Action Potentials↗
PubMed2001

Temporal coding of contrast in primary visual cortex: when, what, and why.

How do neurons in the primary visual cortex (V1) encode the contrast of a visual stimulus? In this paper, the information that V1 responses convey about the contrast of static visual stimuli is explicitly calculated. These responses often contain several easily distinguished temporal components, which will be called latency, transient, tonic, and off. Calculating the information about contrast conveyed in each component and in groups of components makes it possible to delineate aspects of the temporal structure that may be relevant for contrast encoding. The results indicate that as much or more contrast-related information is encoded into the temporal structure of spike train responses as into the firing rate and that the temporally coded information is manifested most strongly in the latency to response onset. Transient, tonic, and off responses contribute relatively little. The results also reveal that temporal coding is important for distinguishing subtle contrast differences, whereas firing rates are useful for gross discrimination. This suggests that the temporal structure of neurons' responses may extend the dynamic range for contrast encoding in the primate visual system.

Action Potentials↗
PubMed2000

Interspike intervals, receptive fields, and information encoding in primary visual cortex.

In the primate primary visual cortex (V1), the significance of individual action potentials has been difficult to determine, particularly in light of the considerable trial-to-trial variability of responses to visual stimuli. We show here that the information conveyed by an action potential depends on the duration of the immediately preceding interspike interval (ISI). The interspike intervals can be grouped into several different classes on the basis of reproducible features in the interspike interval histograms. Spikes in different classes bear different relationships to the visual stimulus, both qualitatively (in terms of the average stimulus preceding each spike) and quantitatively (in terms of the amount of information encoded per spike and per second). Spikes preceded by very short intervals (3 msec or less) convey information most efficiently and contribute disproportionately to the overall receptive-field properties of the neuron. Overall, V1 neurons can transmit between 5 and 30 bits of information per second in response to rapidly varying, pseudorandom stimuli, with an efficiency of approximately 25%. Although some (but not all) of our results would be expected from neurons that use a firing-rate code to transmit information, the evidence suggests that visual neurons are well equipped to decode stimulus-related information on the basis of relative spike timing and ISI duration.

Action Potentials↗
PubMed1998

The power ratio and the interval map: spiking models and extracellular recordings.

We describe a new, computationally simple method for analyzing the dynamics of neuronal spike trains driven by external stimuli. The goal of our method is to test the predictions of simple spike-generating models against extracellularly recorded neuronal responses. Through a new statistic called the power ratio, we distinguish between two broad classes of responses: (1) responses that can be completely characterized by a variable firing rate, (for example, modulated Poisson and gamma spike trains); and (2) responses for which firing rate variations alone are not sufficient to characterize response dynamics (for example, leaky integrate-and-fire spike trains as well as Poisson spike trains with long absolute refractory periods). We show that the responses of many visual neurons in the cat retinal ganglion, cat lateral geniculate nucleus, and macaque primary visual cortex fall into the second class, which implies that the pattern of spike times can carry significant information about visual stimuli. Our results also suggest that spike trains of X-type retinal ganglion cells, in particular, are very similar to spike trains generated by a leaky integrate-and-fire model with additive, stimulus-independent noise that could represent background synaptic activity.

Action Potentials↗
PubMed1997

Response variability and timing precision of neuronal spike trains in vivo.

We report that neuronal spike trains can exhibit high, stimulus-dependent temporal precision even while the trial-to-trial response variability, measured in several traditional ways, remains substantially independent of the stimulus. We show that retinal ganglion cells and neurons in the lateral geniculate nucleus (LGN) of cats in vivo display both these aspects of firing behavior, which have previously been reported to be contradictory. We develop a simple model that treats neurons as "leaky" integrate-and-fire devices and show that it, too, can exhibit both behaviors. We consider the implications of our findings for the problem of neural coding.

Animals↗
PubMed1996

Methods of sedation for auditory brainstem response testing.

Young children and those who are mentally impaired frequently require sedation to attain accurate results when testing for auditory brainstem response (ABR). There have been no previous studies of appropriate methods of sedation, and there is no consensus on pharmacotherapy, monitoring equipment, facilities, or personnel necessary for safe and effective ABR testing. To obtain a national census of current practice, we sent a survey to 149 free-standing children's hospitals in the US. A prospective study was also conducted to assess the effects of sedation utilized to perform ABR testing at The Children's Hospital of Alabama. Oral chloral hydrate (50 mg/kg) was administered for sedation in an outpatient setting with a registered nurse and audiologist present, while vital signs, skin color, and oxygen saturation were continuously monitored. The cost of testing in an audiology or other outpatient suite was compared with the cost of performing the study in the operating room. Results of the survey illustrated the present lack of national uniformity in sedation administered, as well as various problems and complications encountered with such testing. We found that 50 mg/kg chloral hydrate administered in this setting is safe and effective for children requiring sedation for audiologic testing. Further, the ability to perform ABR's in an outpatient suite in a monitored setting is more cost-effective than testing in the operating room.

Adolescent↗
PubMed1995

Upper airway obstruction in Sturge-Weber and Klippel-Trenaunay-Weber syndromes.

Sturge-Weber syndrome is a rare congenital angiomatosis of unknown cause that is defined by the following triad: facial port-wine stain, leptomeningeal vascular anomalies, and choroidal vascular lesions associated with glaucoma. Klippel-Trenaunay-Weber syndrome is a related disease with questionable hereditary factors diagnosed by the following triad: superficial nevus of the lower extremity, ipsilateral varicose veins, and hypertrophy of the soft and bony tissues of the lower limb. The two conditions rarely have been reported to coexist. Upper airway obstruction is not a prominent feature of either of these two diseases. We present two patients with both of these angiomatoses in whom severe upper airway obstruction necessitated tracheotomy.

Airway Obstruction↗
PubMed1991

A comparison of speech results after the pharyngeal flap and the dynamic sphincteroplasty procedures.

Eighty-five patients underwent surgery to reduce velopharyngeal incompetence with either a pharyngeal flap (n = 75) or a dynamic sphincteroplasty (n = 10) performed between April 1958 and August 1989, and were evaluated preoperatively and postoperatively by a plastic surgeon, speech pathologist, and otolaryngologist. Improvement in speech was noted in 75% (n = 56) of the patients with pharyngeal flaps and 70% (n = 7) of the patients with dynamic sphincteroplasties postoperatively. Thirty percent of the patients in both groups showed no improvement postoperatively in speech. Three patients (4%) who underwent pharyngeal flap procedures developed sleep apnea postoperatively. Persistent velopharyngeal incompetence may be treated effectively with either a pharyngeal flap or a dynamic sphincteroplasty. Either procedure appears to result in improved speech in most patients.

Adolescent↗