Edwin R Lewis

• PhD, Stanford University
• Professor Emeritus at University of California, Berkeley

We begin with premises about natural science, its fundamental protocols and its limitations. With those in mind, we construct alternative descriptive models of consciousness, each comprising a synthesis of recent literature in cognitive science. Presuming that consciousness arose through natural selection, we eliminate the subset of alternatives th...

In May, 2010, the University of Southern California's Biomedical Simulations Resource sponsored a one-day Focused Study Group to discuss the future rolls of multi-elecrode ensemble studies in brain research. Not being involved in such studies myself, I presumed that my job would be to provide some philosophical underpinnings for ensemble studies. I...

The filters of the vertebrate ear allow the acoustic areas of the brain to separate significant acoustic signals from one another as well as from background noise. In order to do this, those filters should exhibit very high resolution in both time and frequency. Comparative physiological data from Red-eared Turtle, American Bullfrog and Mongolian G...

Second-order reverse correlation (second-order Wiener-kernel analysis) was carried out between spike responses in single afferent units from the basilar papilla of the red-eared turtle and band limited white noise auditory stimuli. For units with best excitatory frequencies (BEFs) below approximately 500Hz, the analysis revealed suppression similar...

[AN ELECTRONIC REPRINT OF THE PUBLISHED ARTICLE IS AVAILABLE FROM lewis@eecs.berkeley.edu] <I have posted the "nearly final" draft of the paper because, in the final draft, a copy editor made seemingly small changes that obscured my original meaning and were embarrassing to me. And I was not offered a chance to approve them. What I have posted thus...

Insect prey of the Namib golden mole congregate beneath clumps of grass scattered among the sand dunes of the Namib Desert. In the presence of the light winds that typically blow over the Namib Desert, these grass clumps emit low-amplitude vibrations that are transmitted through the sand. While foraging in the sand-swimming mode (a few centimeters...

The spectro-temporal receptive field [Hear. Res 5 (1981) 147; IEEE Trans BME 15 (1993) 177] provides an explicit image of the spectral and temporal aspects of the responsiveness of a primary auditory afferent axon. It exhibits the net effects of the competition between excitatory and inhibitory (or suppressive) phenomena. In this paper, we introduc...

A brilliant mid-20th century physicist was said to have equated the relationship of philosophy of science to scientists and the relationship of ornithology to birds. The same fellow sculpted what remains the most precisely predictive model in science, made so by inclusion of steps in reverse time. I suspect he was, after all, a closet philosopher....

For understanding the physics of sound and the biophysics of acoustic sensors in animals, the concepts of impedance and admittance, impedance matching, transducer, transformer, passive and active, bidirectional coupling, and resonance are widely used. They all arise from the circuit-theory metamodel, which has been applied extensively in acoustics....

Comparative morphologists, physiologists, and neuroethologists (including the authors of this chapter) make observations at the level of phenotypes. It is natural for them to assume that observed phenotypic traits have been sculpted by evolution and therefore, somehow, have increased the fitnesses of the organisms in which they occur. Inferences ab...

The spectro-temporal receptive field [Hear. Res 5 (1981) 147; IEEE Trans BME 15 (1993) 177] provides an explicit image of the spectral and temporal aspects of the responsiveness of a primary auditory afferent axon. It exhibits the net effects of the competition between excitatory and inhibitory (or suppressive) phenomena. In this paper, we introduc...

Information about the tuning and timing of excitation in cochlear axons with low-characteristic frequency (CF) is embodied in the first-order Wiener kernel, or reverse correlation function. For high-CF axons, the highest-ranking eigenvector (or singular vector) of the second-order Wiener kernel often can serve as a surrogate for the first-order ker...

In response to white‐noise stimuli, AP afferent axons of Rana catesbeiana and R. esculenta exhibit excitation, adaptation, and suppression simultaneously. After eigendecomposition of the second‐order Wiener kernel, spectrotemporal properties of suppression and adaptation, in the individual axon, can be reconstructed by short‐term averaging taken pa...

Information about the tuning and timing of excitation, adaptation and suppression in an auditory primary afferent axon can be obtained from the second-order Wiener kernel. Through the process of singular-value decomposition, this information can be extracted from the kernel and displayed graphically in separate two-dimensional images for excitation...

Modern frogs and toads possess a structurally unique saccule, endowing them with seismic sensitivity greater than that observed so far in any other group of terrestrial vertebrates. In synchrony with their advertisement calls, approximately half of the calling males of one frog species, the Puerto-Rican white-lipped frog ( Leptodactylus albilabris...

We test Lowenstein’s dc bias hypothesis as an alternative mechanism for the phenomenon sometimes called ‘stochastic resonance’. Probe stimuli consisting of paired phase-locked tones at frequencies f1 and f2 (where f2−f1=800 Hz, f1>4.5 kHz) and at equal intensity were used to generate synchronous 800 Hz cochlear nerve activity (envelope responses)....

During the breeding season, each tympanic membrane of males of the Old World treefrog Petropedetes parkeri is decorated with a single, prominent, fleshy tympanic papilla. The tympanic papilla, located dorsally on the tympanic membrane, is covered by an epidermal surface and is composed of non-ossified, spongiform tissue containing a number of globu...

SYNOPSIS. Modern frogs and toads possess a structurally unique saccule, endowing them with seismic sensitivity greater than that observed so far in any other group of terrestrial vertebrates. In synchrony with their advertisement calls, approximately half or the calling males of one frog species, the Puerto-Rican white-lipped frog (Leptodactylus al...

The Namib Desert golden mole is a nocturnal, surface-foraging mammal, possessing a massively hypertrophied malleus which presumably confers low-frequency, substrate-vibration sensitivity through inertial bone conduction. Foraging trails are punctuated with characteristic sand disturbances in which the animal's head dips under the sand. The function...

We present examples of results from our studies of auditory primary afferent nerve fibers and populations of such fibers in the frog and gerbil. We take advantage of the natural dithering effect of internal noise, where it is sufficient, to construct highly predictive descriptive models (based on the Wiener series with kernels derived from white-no...

The ability of Wiener series to predict the time course of instantaneous spike rate (as given by the PSTH) in response to a novel stimulus of arbitrary complexity demonstrates that they provide faithful descriptive models of individual auditory nerve fibers–embodying, among other things, the essence of sprectro-temporal filtering. When such models...

An estimate of an auditory fiber's time course of instantaneous spike rate (ISR) in response to a novel sound stimulus is given by the peristimulus-time histogram (PSTH) taken over many repetitions of the stimulus. In this paper we address a bullfrog amphibian-papillar (AP) fiber with intermediate BEF. In such units, the PSTH includes both AC and D...

A singularity event in an acoustic waveform typically produces at most one extra spike in any cochlear neuron, but the synchrony of such spikes over a subpopulation often yields a distinct (whole-nerve) compound action potential, or CAP (Lewis and Henry, Hear. Res. 39 (1989) 209–224). Thus, while a single extra spike among the spontaneous spikes in...

Vocalizations of Boophis madagascariensis (Rhacophoridae) males were recorded in a mid-elevation rain forest in eastern Madagascar. Call notes made by males of this species were classi®ed into 28 types. This represents the largest known call repertoire of any amphibian. The calls range widely in spectral characteristics from a narrowband, nearly pu...

In the now-classical studies that defined the current state of knowledge about the stimulus-response properties of auditory afferent axons, the three fundamental phenomena-excitation, adaptation and suppression were examined independently with simple stimuli. The circumstances under which the predictions fail, and the nature of the failures, have r...

A commonly accepted physiological model for lateralization of low-frequency sounds by interaural time delay (ITD) stipulates that binaural comparison neurons receive input from frequency-matched channels from each ear. Here, the effects of hypothetical interaural frequency mismatches on this model are reported. For this study, the cat's auditory sy...

This ongoing work is concerned with what the gerbil's ear tells the gerbil's brain. The responses of over 600 auditory nerve fibers to band-limited Gaussian white noise were recorded, and a smoothed, linear estimate of each fiber's impulse response was derived using a reverse correlation procedure and a state space model. In this paper, we investig...

Axons from the basilar papilla of the American bullfrog (Rana catesbeiana) do not phase lock to stimuli within an octave of their best frequencies. Nevertheless, they show consistent temporal patterns of instantaneous spike rate (as reflected in peristimulus time histograms) in response to repeated stimuli in that frequency range. We show that the...

Vocalizations of Boophis madagascariensis (Rhacophoridae) males were recorded in a mid‐elevation rain forest in eastern Madagascar. Call notes made by males of this species were classified into 28 types. This represents the largest known call repertoire of any amphibian. Even considering all iambic notes as variants of one type, there remain eight...

Each tympanic membrane (TM) of males of the Old World frog Petropedetes parkeri is decorated with a single, prominent, fleshy papilla during the breeding season. The papilla is composed of a nonossified, spongiform tissue that contain fluid?filled canals that terminate at or near the papillar surface. Roughly three?quarters of the papillar mass is...

A mammal’s cochlea appears to be an array of band-pass filters with steep high-frequency band edges and overlapping pass bands, each covering a slightly different range of frequencies and each serving as a separate signal-processing channel. With the channels ordered according to their pass band peaks, the system’s response to a stimulus can be vis...

Various vertebrate inner-ear end organs appear to have switched their sensory function between equilibrium sensing and acoustic sensing over the courses of various lines of evolution. It is possible that all that is required to make this transition is to provide an end organ with access to the appropriate stimulus mode and frequency range. If, as w...

According to current classification, the living amphibians are distributed among three orders—Caudata (newts and salamanders, or urodeles), Gymnophiona (caecilians), and Anura (frogs and toads)—which often are grouped in a single subclass—Lissamphibia. A current summary of the biology of the Lissamphibia is found in Duellman and Trueb (1994). Among...

Banner-tailed kangaroo rats, Dipodomys spectabilis, footdrum to produce substrate-borne and airborne acoustic energy. Previous studies show that they communicate territorial ownership via airborne footdrumming signals. The research reported here used simulated footdrum patterns generated by an artificial 'thumper' to address the question of whether...

Multi-microelectrode silicon devices were developed for extracellular recording from multiple axons in regenerated eighth cranial nerves of American bullfrogs. Each includes a photolithographically defined array of holes and adjacent metal microelectrodes. A device is implanted within a transected eighth nerve; regenerating fibers grow through the...

Behavioral adaptations exhibited by two African fossorial mammals for the reception of vibrational signals are discussed. The Namib Desert golden mole (Eremitalpa granti namibensis) is a functionally blind, nocturnal insectivore in the family Chrysochloridae that surface forages nightly in the Namib desert. Both geophone and microphone recordings i...

Banner-tailed kangaroo rats, Dipodomys spectabilis, footdrum to produce substrate-borne and airborne acoustic energy. Previous studies show that they communicate territorial ownership via airborne footdrumming signals. The research reported here used simulated footdrum patterns generated by an arti®cial `thumper' to address the question of whether...

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Old World treefrogs in the family Rhacophoridae have complex vocalizations. The vocal repertoire of a population of endemic males, Boophis madagascariensis, was studied in the animals? natural habitat in Ranomafana National Park in eastern Madagascar. Twenty?eight calls and variations were recorded. This represents the largest call repertoire of an...

A common property of vertebrate acoustic sensors, including otoconial acoustic sensors in lower vertebrates, is steep slopes on the high- and low-frequency band edges of the amplitude tuning curves. Bullfrog otoconial acoustic fibers are responsive to sound and exquisitely responsive to substrate vibrations in the frequency range from 20 Hz to 300...

It is well known that, in a cochlear afferent axon with background spike activity, a sinusoidal stimulus (tone) of sufficiently low frequency will produce periodic modulation of the instantaneous spike rate, the alternating half cycles of which comprise excursions above and below the mean background spike rate. It also is known that if the amplitud...

The concept of temporal order, as embedded in the notions of before, after, and simultaneous, is useful for considering the activities of the individual organism and the effectiveness with which it interacts with the world in which it lives. The potential prey organism will be more likely to survive, for example, if it detects the presence of the p...

Les cris mâles du #Boophis madagascariensis$) (#Rhacophoridae$) ont été enregistrés dans son milieu naturel, la forêt tropicale humide de l'est de Madagascar. Nous les avons classés ensuite en 28 types différents. Bien que tous les cris "iambiques" soient considérés comme les variantes d'un même type, cette espèce en compte 8 à son actif, ce qui re...

A common property of vertebrate acoustic sensors, including otoconial acoustic sensors in lower vertebrates, is steep slopes on the high- and low-frequency band edges of the amplitude tuning curves. Bullfrog otoconial acoustic fibers are responsive to sound and exquisitely responsive to substrate vibrations in the frequency range from 20 Hz to 300...

The call repertoire of Boophis madagascariensis (Rhacophoridae) males was recorded in habitat of this animal-the rain forest in eastern Madagascar. We have classffied the calls by males of this species into 28 types. Even if all (iambic > calls are considered variants of one there are still 8 call types producedby this species. This represents the...

A clinical microwave device was used to heat the head and ear of the North American bullfrog in order to observe the temperature dependence of tuning in the sacculus, an organ known to possess the capability of electrical resonance in its hair cells. In tuning curves derived from reverse correlation analysis with noise stimuli, the temperature depe...

Modeling provides a bridge between the natural sciences (physics, chemistry, biology, and the like) and the axiomatic sciences (mathematics and statistics). Inductively-derived descriptive models map observations of physical processes into mathematical descriptions that can be treated as axioms (e.g., the various laws of physics). A synthetic model...

Signal processing in individual channels of the auditory periphery are modelled based on I/O data. Each channel comprises the outer and middle ear apparatus in cascade with a single cochlear filter served by several cochlear afferent nerve fibers. The input is an auditory stimulus and the output is a sequence of neural spike events recorded from co...

It is well known that, in a cochlear afferent axon with background spike activity, a sinusoidal stimulus (tone) of sufficiently low frequency will produce periodic modulation of the instantaneous spike rate, the alternating half cycles of which comprise excursions above and below the mean background spike rate. It also is known that if the amplitud...

Afferent axons of the gerbil cochlear nerve were studied with reverse correlation analyses carried out with movable time windows and with noise that was modulated with a 10-Hz trapezoidal envelope that switched the noise amplitude between two levels, 20 dB apart. At the time of switching, the attributes of the axonal tuning curves derived in this m...

A new process for the fabrication of regeneration microelectrode arrays for peripheral and cranial nerve applications is presented. This type of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafter held fixed with respect to the microelectrodes. The process describe...

If a spike trigger zone exhibits the same sort of accommodation that has been found universally in peripheral axons and is an emergent property of the Hodgkin-Huxley model and other synthetic models of axonal membrane (1,2), then spike production will be favored by steep positive slopes of the waveform of the current into the trigger zone. Thus, la...

Afferent axons of the gerbil cochlear nerve were studicd with revcrse correlation analyses carried out with movable time windows and with noise that was modulated with a 10-Hz trapezoidal envelope that switched thc noise amplitude bctwccn two levels, 20 dB apart. At the time of switching, the attributes of the axonal tuning curves derived in this m...

In this work we have looked at the effects of neuronal modeling parameters on the images generated by ensembles of neurons. It is clear that the parameters have an effect on the response behavior of single units and it is often not difficult to ascertain these effects quantitatively or through simple reasoning. The effects on neuronal populations a...

We have developed a model for the mammalian medial superior olive (MSO) based on the concept of neuronal cross-correlation. The input to the model is derived from a representation of the cochlea and auditory nerve. We show that the model is capable of discriminating the difference in the time of arrival of signals at the two ears not only for singl...

Many primary auditory neurons do not follow the temporal fine structure of waveforms within their passband; these are termed non-phase locked cells. Such cells do not encode the sound pressure waveform directly but rather some nonlinear functional of the waveform such as the envelope. But which definition of the envelope — or more generally which n...

We have developed an integrate-and-fire spike-initiation model based on that of Hill (1936), which comprises a pair of coupled, linear differential equations describing membrane potential and a threshold variable. In our version, we add an intrinsic noise source and explicit representation of the spike and its effect on threshold. The equations of...

All of an organism's knowledge about the acoustic world is coded in the spike trains of its auditory nerve fibers. Several fundamental aspects of this internal representation are not well understood: How much information is carried by the auditory nerve and how efficient is the coding of information? What is the role of nonlinearities in the coding...

One-tone rate suppression has been reported several times for auditory nerve fibers of mammalian and non-mammalian vertebrates. Because its properties are very similar to those of two-tone rate suppression, the possibility exists that one-tone rate suppression is the result of an interaction within the inner ear of the suppressing tonal stimulus an...

Among primary auditory axons with characteristic frequencies (CFs) below 2500 Hz, a substantial subpopulation was found in which spike activity was driven by cardiac events. The presence of cardiac-driven activity was inferred from cycle histograms triggered on the peak of the electrocardiogram (ECG). This driven activity was either like a simple o...

In modern frogs, the amphibian papilla exhibits a caudal extension whose shape, relative length, and proportion of hair cells vary markedly from species to species. Tuning in the caudal extension is organized tonotopically and evidently involves the tectorium. In terms of the proportion of amphibian-papillar hair cells in the caudal extension, we r...

Both seismic and auditory signals were tested for their propagation characteristics in a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by alternately drumming its hind legs on the burrow floor. Sign...

Abstract The senses of the vertebrate inner ear are divided into two categories: senses of balance, which convey information about orientation and motion of the head; and acoustic senses, which convey information about vibrations propagated to the ear from remote sources. In the mammalian inner ear, acoustic senses are concentrated in the cochlea,...

Many investigators believe that tuning in the acoustic sensors of lower vertebrates is accomplished by second order resonances, first described in turtle hair cells (Crawford and Fettiplace 1981) and subsequently found in the hair cells of two amphibian sensors (Pitchford and Ashmore 1987; Lewis and Hudspeth 1987). In contrast, acoustic nerve fiber...

We have developed a massively parallel modeling framework for the mammalian auditory front end (Gangnes, 1990). It comprises a set of linear cochlear filters each connected to a set of independently firing, noisy spike initiators. The model is a software (C) construction in which the number of filters, the number of spike initiators per filter, and...

On its sensory side, the nervous system has many modalities (vision, audition, olfaction, etc.), and in each case the central computing machinery appears to be organized as a series of layered structures. If the computing machinery in each case uses the same self-organization algorithm and we can discover that algorithm, then we will have a powerfu...

We present seismic and auditory frequency tuning curves of individual bullfrog, Rana catesbeiana, saccular and amphibian papilla axons that responded to both seismic and auditory stimuli. In this study we found:1) most saccular axons respond well to auditory stimuli with moderate signal strength (50–70 dB SPL) as well as to seismic stimuli; 2) most...

Intracellular microelectrode recording/labelling techniques were used to investigate vestibular afferent responses in the bullfrog, to very small amplitude (<0.5°p-p) sinusoidal rotations in the vertical plane over the frequency range of 0.063–4 Hz. The axis of rotation was congruent with the axis of the anterior semicircular canal. Robust response...

We present three models which have been used to model neuronal spike initiation and discuss their relative merits for inclusion in biological neural networks. We compare their versatility, efficiency of computation and general characteristics. We show that the model of Hill [I] has some advantages over those of Hodgkin and Huxley [Z] and FrankenMus...

Intracellular microelectrode recording/labelling techniques were used to investigate vestibular afferent responses in the bullfrog, to very small amplitude (<0.5 ° p-p) sinusoidal rotations in the vertical plane over the frequency range of 0.063-4 Hz. The axis of rotation was congruent with the axis of the anterior semicircular canal. Robust respon...

We present seismic and auditory frequency tuning curves of individual bullfrog, Rana catesbeiana, saccular and amphibian papilla axons that responded to both seismic and auditory stimuli. In this study we found: 1) most saccular axons respond well to auditory stimuli with moderate signal strength (50-70 dB SPL) as well as to seismic stimuli; 2) mos...

Within the bullfrog semicircular canal crista, hair cell tuft types were defined and mapped with the aid of scanning electron microscopy. Intracellular recording and Lucifer Yellow labeling techniques were used to study afferent responses and arborization patterns. Dye-filled planar afferent axons had mean distal axonal diameters of 1.6–4.9 μm, hig...

Single fiber recordings were made from auditory nerve fibers of the American bullfrog (Rana catesbeiana). As temperature was raised: (1) Best frequencies of fibers from the amphibian papilla (N = 15) increased. Below 600 Hz best frequency changes up to 0.06 oct/degrees C were found; above 600 Hz changes were less than 0.03 oct/degrees C. In the bas...

In recent years, data from individual hair cells have suggested that frequency selectivity in lower vertebrates is accomplished by the amplitude tuning peaks of underdamped electrical resonances (Crawford and Fettiplace, 1981; Lewis and Hudspeth, 1983; Pitchford and Ashmore, 1987). In the present study we have used the reverse-correlation (REVCOR)...

One way that discrete acoustic events may be signaled to the central nervous system is through spike synchrony over a subpopulation of cochlear axons. Each of the four corners of a trapezoidally modulated tone burst is such an event. Ordinarily, each comer comprises both an abrupt change in envelope slope and a singularity in the modulated waveform...

1. The call-timing algorithm of the white-lipped frog,Leptodactylus albilabris, was studied in the field using playback of conspecific advertisement calls (chirps) recorded with a digital electronic device developed for these studies. 2. A call refractory period is present. The interval between the onsets of successive chirps from one individual is...

Investigating theoretical conditions under which linearly-operating tuned structures produce click-like transient responses to onsets and offsets of trapezoidal tone bursts, we come to the following conclusions: (1) each of the four corners of the trapezoidal tone burst is capable of eliciting such a response; (2) the amplitude of the response and...

It is shown that noise can be an important element in the translation of neuronal generator potentials (summed inputs) to neuronal spike trains (outputs), creating or expanding a range of amplitudes over which the spike rate is proportional to the generator potential amplitude. Noise converts the basically nonlinear operation of a spoke initiator i...

1. The call-timing algorithm of the white-lipped frog, Leptodactylus albilabris, was studied in the field using playback of conspecific advertisement calls (' chirps ') recorded with a digital electronic device developed for these studies. 2. A call refractory period is present. The interval between the onsets of successive chirps from one individu...

A trapezoidal tone burst (Figure 1) is equivalent to a sum of four ramp-modulated sinusoids. The response of any linearly operating spectral filter (or tuning structure) to a single ramp-modulated sinusoid is made up of two families of components: (a) for each natural frequency of the filter itself, a transient excitation equivalent to that which w...

An early selective advantage of acoustic senses clearly was remote detection of predators (or other dangers) and prey. Therefore, one would expect evolution to have sculpted acoustic receptors for maximum sensitivity. The ultimate limitation on sensitivity is noise, and acoustic receptors must deal with both internal noise (arising from thermal ene...

In previous experiments, it was noted that a cochlear compound action potential (CAP) can be produced by the offset of a tone, provided that the amplitude of the tone is modulated by a trapezoid with slopes that are typically much steeper than required to produce onset responses. Subsequently, such trapezoidal tone bursts with steep slopes were use...

The vocalization behaviour of Leptodactylus albilabris was investigated using field playback experiments. To assess the response of males to pre-recorded natural ‘chirp’ (advertisement call) and natural ‘chuckle” (aggressive call) stimuli of gradually increasing broadcast intensity, three parameters (intensity, dominant frequency and repetition rat...

When electrical resonances were observed in acoustic sensory cells of lower vertebrates, the hearing research community was presented with the exciting possibility that tuning in the ears of those animals might be explained directly in terms of familiar molecular devices. It is reported here that in the frog sacculus, where electrical resonances ha...

Two of the most conspicuous and celebrated properties of human hearing - the abilities to discriminate pitch and to localize sound sources, may have been secondary derivations to which the ear was preadapted by having evolved in the inevitable presence of noise.