Tones Of Different Frequencies Research Articles

Response in tonic type neurons of the cat auditory cortex to tones of different frequencies and intensities

In experiments on immobilized cats, intra- and extracellular response in tonic type neurons to tones of differing frequencies and intensities were investigated, as well as the organizational pattern of receptive fields in these units. Tonic type neurons were encountered at different cortical layers, but mostly (93% of the total) were located at a depth of 1.0–2.2 mm. Minimum thresholds required for response in these neurons were on average 7.7 dB below that found in neurons generating a phasic reaction in response to a tone. "Tonic" differed from "phasic" neurons in their inferior frequency-discriminative ability, with a Q10 value averaging 4.1±0.4 as against 9.1±0.7 in phasic neurons. Size of receptive fields in tonic neurons (as revealed by occurrence of spike response in these units) was 3.5 times that observed in phasic cells. Length of action potentials in the majority (80%) of tonic neurons was about one and a half times to twice that found in phasic units. Tonic neurons also displayed a high degree of sensitivity to changes in the duration and intensity of acoustic stimulation.

Parasagittal thalamic knife-cuts and cardiac changes

Rabbits received knife-cuts either medial or lateral to the mediodorsal nucleus of the thalamus (MD), and had stimulating electrodes implanted in MD. These animals were compared to animals with sham knife-cuts for (1) the cardiac component of the orienting reflex (OR) to novel tone stimuli; (2) differential pavlovian heart rate (HR) conditioning, utilizing tones of different frequencies as CSs and paraorbital shock as the US; and (3) heart rate, blood pressure, electromyographic activity, and respiration changes elicited by electrical stimulation in MD. Medial knife-cuts led to faster habituation of the OR, and to somewhat attenuated HR conditioning, but had no effect on stimulation-elicited changes. Lateral knife-cuts, on the other hand, enhanced the stimulation-elicited HR response, but had little effect on the HR OR. The HR CR was unaffected by lateral cuts during an initial conditioning session, but was attenuated in both knife-cut groups during a second session, compared to sham control animals.

Responses of single auditory cortical neurons to tone sequences

The responses of single neurons in the primary and secondary auditory cortex of cat were recorded during the presentation of sequences consisting of five tones of different frequencies. Discharges to tones within these sequences usually (84%) exhibited a dependence on the ‘direction’ of the sequence (ascending, descending, or mixed frequencies). For sequences consisting of 5 tones of identical frequency (monotone) the response often depended on serial position, including cases in which the neuron only responded to later tones in the sequence. Comparison of responses to heterogeneous and monotone sequences showed that response dependence on serial position was a factor in response dependence on sequence direction. Auditory cortical neurons can exhibit stronger responses to a tone presented in a sequence than to the same tone presented alone. Hence, the responses to tones within sequences may not be highly predictable from the responses to isolated tones.

Mediodorsal thalamic lesions impair differential Pavlovian heart rate conditioning.

Rabbits with bilateral ibotenic acid or vehicle injections into the mediodorsal nucleus of the thalamus (MD) received differential Pavlovian heart rate (HR) conditioning in which tones of different frequencies served as conditioned stimuli (CSs) and a paraorbital electric shock train was the unconditioned stimulus (US). Rabbits with ibotenic acid lesions of MD demonstrated impaired differential HR conditioning, due primarily to enhanced responding to the non-reinforced CS-. The magnitude of the HR conditioned response (CR) was somewhat enhanced in lesioned animals compared to vehicle control animals, as was the HR component of the orienting response to non-reinforced tones. These results are consistent with a role for MD in some aspect of association formation, possibly through its mediation of the late-occurring sympathetic component of the conditioned HR response. These data also demonstrate that MD does not participate in the vagal drive that produces Pavlovian conditioned bradycardia.

Tropical Forest Bird Counts and the Effect of Sound Attenuation

Tropical Forest Bird Counts and the Effect of Sound Attenuation

Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. II. Responses to band-pass filtered noises.

1. We studied cells in the central nucleus of the inferior colliculus of the cat that were sensitive to interaural time delays (ITDs) in order to evaluate the influence of the stimulus spectrum of noise signals. Stimuli were sharply filtered low-, high-, and band-pass noise signals whose cutoff frequencies and bandwidths were systematically varied. The responses to ITDs of these noise signals were compared with responses obtained to ITDs of broadband noise and pure tones. 2. The discharge rate in response to band-pass noise as a function of ITD was usually a cyclic function with decreasing peak amplitudes at longer ITDs. The reciprocal of the mean interval between adjacent peaks indicated how rapidly the response rate varied with ITD and was termed the response frequency (RF). This RF was approximately equal to the median frequency of the stimulus spectrum filtered by the cell's sync-rate curve, which was the product of the synchronization to interaural phase and the discharge rate plotted against frequency. This suggests that the RF was determined by all the spectral components in the stimulus that fell within the frequency range in which the cell's response was synchronized. The contribution of each component was proportional to the sync-rate for that frequency. 3. The central peak of the ITD function usually fell within the physiological range of ITDs (+/- 400 microseconds). The location of this peak did not vary significantly with changes in stimulus spectrum by comparison with responses to tones of different frequency. Its shape also remained constant, except for a decrease in width when high-frequency components within the range of the sync-rate curve were added to the stimulus. A few cells responded with a minimal discharge instead of a maximal near-zero ITD, and this central minimum had similar properties as the central peak. The amplitude of the secondary peaks of the ITD function decreased as the stimulus bandwidth that overlapped the sync-rate curve broadened. 4. The sum of the ITD functions to two band-pass signals was similar to that of a broadband signal whose spectrum was composed of the sum of the band-pass spectra. 5. From these binaural responses we could make inferences about the response characteristics of the monaural inputs to binaural neurons. We then verified these predictions by studying responses of low-frequency trapezoid body fibers to band-pass noises.

Developmental stability of the tonotopic organization of the chick's basilar papilla.

In the past, the damage patterns produced on the papilla of the chick by loud pure tones of different frequencies have been used to study the development of sound analysis by the hair cells of the basilar papilla. One conclusion from these data was that the best response frequency of individual hair cells changes substantially with age. However, this method has been criticized as unreliable. Now experiments have been performed in which single characterized nerve fibers were stained with horseradish peroxidase to permit the unequivocal localization of specific frequency responses in the papillae of chicks of different ages (2 and 21 days after hatching). There was no statistically significant change in the tonotopic organization of the papilla between the two groups of animals.

Acoustic sensitivity and bimodal properties of cells in the anterior suprasylvian gyrus of the cat.

The properties of acoustically responsive neurons were studied in the anterior part of the gyrus suprasylvius (ASG) of the cat. The most important features of the responses given to pure tones of different frequencies were: short latency, sharp tuning curves with well definable best frequency (BF). In these respects the cells showed a close resemblance to those of primary acoustic area (AI), and at the same time they proved to be true bimodal cells (responding to somatosensory stimuli, too) like those of the associative areas.

Interspecific acoustic interactions of the neotropical treefrog Hyla ebraccata

Hyla ebraccata, H. microcephala and H. phlebodes commonly occur together in Panama. The three species have calls exhibiting broad frequency overlap and call during the same season and time of day from similar microhabitats, frequently in close proximity. The vocal repertoires of the three species are structurally and functionally similar. All employ multi-part advertisement and aggressive calls which consist of a primary note followed by a variable number of clicks. H. ebraccata males often responded to heterospecific calls with multi-note synchronized responses, and calls with primary notes greater than 150–200 ms were most effective in eliciting synchrony. Playback experiments with synthetic 1-note advertisement calls of different durations and both synthetic 1-note advertisement calls and 200 ms tones of different frequencies demonstrated that H. ebraccata males will synchronize with stimuli which are similar in frequency and duration to conspecific calls. Data from a two-choice experiment with female H. ebraccata demonstrate that calls of individual H. microcephala can reduce the attractiveness of a H. ebraccata male's calls if primary notes overlap. By synchronizing response calls to those of H. microcephala, a H. ebraccata may reduce the chances that his calls are rendered less attractive to potential mates.

Intracellular responses of primary auditory cortical neurons to tones of different frequencies and to electrical stimulation of spiral ganglion fibers in cat

Experiments on cats anesthetized with pentobarbital showed that, depending on the intensity and frequency of acoustic stimulation, neurons in auditory area AI give responses of EPSP, EPSP-spike-IPSP, EPSP-IPSP, and IPSP type. Presentation of a tone of characteristic or near-characteristic frequency and above-threshold intensity, and also electrical stimulation of nerve fibers of the spiral ganglion, innervating the central zone of the receptive field of the neuron, evoke in most cases a response of EPSP-spike-IPSP type. Tone differing considerably in frequency from the characteristic, and electrical stimulation of peripheral zones of the receptive field, evoked responses of EPSP-IPSP or IPSP type. The range of frequencies of tones to which, at threshold intensity, an action potential is generated by the neuron is considerably narrower than the range of frequencies of tones evoking an EPSP and IPSP. Above the intensity of tone threshold IPSP is an invariable component of the response of most neurons in area AI. The appearance of an IPSP in the neuron is accompanied by depression of spontaneous activity and the neuronal response to testing stimulation. Two types of IPSP were distinguished: One type is a component of the EPSP-spike-IPSP response and arises during excitation of auditory receptors located in the central part of the receptive field of the neuron, the other arises during excitation of receptors located at the periphery of the field, and which project to neurons with other characteristic frequencies. The former arise after spike excitation of the neuron, the latter after EPSP or primarily.

Responses of cat auditory cortical neurons to tones of different frequencies and electrical stimulation of corresponding regions of the cochlea

Characteristic frequencies of neurons in the cat auditory cortex (area AI) whose receptive fields are located in different parts of the basilar membrane of the cochlea were determined in cats anesthetized with pentobarbital. The higher the characteristic frequency of a neuron in area AI, the nearer its receptive field lies to the base of the cochlea. Receptive fields of neurons with a characteristic frequency higher than 4 kHz lie on the first 10 mm of the basilar membrane. Receptive fields of neurons with a characteristic frequency below 4 kHz lie on the remaining 11–12 mm of the membrane. The effect of electrical stimulation of the center of the receptive field of a neuron corresponds to its response to a tone of characteristic frequency. The more the frequency of the acting tone differs from the characteristic frequency, or the further the point of stimulation from the center of the receptive field of the neuron, the less likely is the neuron to respond with an action potential. Neurons with a low characteristic frequency have wider receptive fields than neurons with a high characteristic frequency. Receptive fields of neurons with close characteristic frequencies on the basilar membrane overlap considerably. It was shown by the method of paired stimulation that excitation evoked in neurons in area AI by the action of a tone of a particular frequency is followed by long-lasting inhibition. This inhibition lasts longest and is most effective if a tone of the characteristic frequency is used.

Event-related potentials during selective attention to speech sounds

Event-related potentials (ERPs) were recorded from subjects while they selectively attended to sequences of stop-consonant syllables or sequences of tone pips of different frequencies. The ERP difference waveforms that distinguished attended from unattended speech sounds were highly similar in morphology and scalp distribution to the difference waveforms elicited by the tone pips. These results suggest that the attention mechanisms brought into play when selecting complex phonetic stimuli for further analysis are similar to those engaged when selecting between tones of different frequencies, in contrast with previous theoretical interpretations. Latency differences observed between the attention-related ERPs to simple and complex stimuli were attributed to differences in the duration of processing that makes these stimulus features available to attention mechanisms.

Hippocampal lesions and Pavlovian cardiovascular conditioning.

New Zealand albino rabbits received either sham, cortical control, or hippocampal lesions and were subjected to differential Pavlovian conditioning in which tones of different frequencies served as conditional stimuli (CSs), and a brief paraorbital electric shock train served as the unconditional stimulus. Heart rate (HR), blood pressure (BP), and electromyographic (EMG) conditional responses (CRs) were recorded. Animals with cortical and hippocampal damage or animals with cortical damage alone revealed attenuated bradycardiac CRs, but HR CRs of the former two groups did not significantly differ. BP changes were minimal; reliable differences were not obtained between CS+ and CS-. However, these changes consisted of small but reliable depressor responses, which were not affected by either cortical or hippocampal lesions. Few EMG CRs were obtained. These data, combined with those of previous experiments, suggest that forebrain structures may modulate higher level processing of stimulus information, perhaps in terms of assessing the biological significance of such stimulation.

Cingulate damage attenuates conditioned bradycardia

New Zealand albino rabbits received either sham, midline cortical, lateral cortical, or combined medial-lateral cortical lesions, and were subjected to differential Pavlovian conditioning in which tones of different frequencies served as the conditioning stimulus and a brief paraorbital electric shock train served as the unconditioned stimulus. Heart rate conditioned responses were recorded. Damage to medial but not lateral neocortex abolished the heart rate conditioned response. These data suggest that midline cortical structures may modulate higher level processing of stimulus information.

Lateral septal lesions enhance conditioned bradycardia in the rabbit.

New Zealand albino rabbits received sham lesions or complete, medial, lateral, or posterior septal lesions and were subjected to differential conditioning in which tones of different frequencies served as conditioned stimuli and paraorbital electric shock was the unconditioned stimulus. Electromyographic (EMG), heart rate (HR), and blood pressure (BP) conditioned responses (CRs) as well as hippocampal rhythmic slow wave activity (RSA) were recorded. Lateral or complete septal lesions enhanced the bradycardiac HR CR but had no effect on the BP depressor response. Both unconditioned and conditioned EMG responses occurred infrequently and were unaffected by any lesion. Unconditioned HR responses and somatomotor threshold determinations to unsignaled electric shock were also unaffected by the lesions. Complete septal lesions increased locomotor activity relative to sham or other septal lesions. Little hippocampal RSA was detected in animals with medial lesions, but the HR CR was unimpaired in these animals. These data implicate the septo-hippocampal circuit in classical conditioning of cardiovascular changes and further suggest that diencephalic forebrain structures may modulate forebrain processing of sensory stimulation, perhaps in terms of assessing its biological significance.

Theoretical basis for the perception of acoustic stimuli by the mammalian brain: CNS-endogenous microwave fields

Endogenous microwave fields are those radiated by changes in rotational energy state of proteins integral to neural membranes. Previous electromagnetic analysis [P. L. Stocklin and B. F. Stocklin, T.-I.-T. J. Life Sci. 9, 29–51 (1979)] and data review [P. L. Stocklin and B. F. Stocklin, Physiol. Chem. Phys. 13, 175–177 (1981)] have developed properties of characteristic modes supported by the adult human brain/skull cavity, whose frequencies lie within the protein rotational frequency band. Basic physical theory is reviewed, then applied to acoustic stimulus perception. When neurally stimulated, the primary auditory cortex (AI) acts as a modal source region. Within AI, tonotopicity matches the orderly variation of mode energy partitioning as source location is changed. Elsewhere within the auditory cortex, modal properties support the absence of strict tonotopicity. Transverse electric field modal patterns and rank-ordered modal energy analysis are used to relate modal properties to the following properties of hearing: perceived difference between acoustic tones of different frequency, two-tone consonance/dissonance, and frequency variation of minimum audible signal level.

STIMULUS GENERALIZATION OF SCHEDULE‐INDUCED POLYDIPSIA

Five rats were exposed to an intradimensional discrimination by associating two tones of different frequency with the components of a multiple random-time 30-sec, extinction schedule of food presentation. After schedule-induced polydipsia developed and the intermittent schedule of food presentation established stable differential licking rates during the stimuli associated with the multiple schedule, a stimulus generalization test was conducted. When generalization testing was conducted by presenting stimuli that varied on the frequency dimension during the random-time 30-sec component of the multiple schedule, all five rats demonstrated moderately sloping symmetrical gradients. Thus, schedule-induced polydipsia can be brought under the control of stimuli other than the food pellet.

An electrical tuning mechanism in turtle cochlear hair cells.

1. Intracellular recordings were made from single cochlear hair cells in the isolated half-head of the turtle. The electrical responses of the cells were recorded under two conditions: (a) when the ear was stimulated with low-intensity tones of different frequencies and (b) when current steps were injected through the intracellular electrode. The aim of the experiments was to evaluate the extent to which the cochlea's frequency selectivity could be accounted for by the electrical properties of the hair cells.2. At low levels of acoustic stimulation, the amplitude of the hair cell's receptor potential was proportional to sound pressure. The linear tuning curve, which is defined as the sensitivity of the cell as a function of frequency when the cell is operating in its linear range, was measured for a number of hair cells with characteristic frequencies from 86 Hz to 425 Hz.3. A rectangular current passed into a hair cell elicited a membrane potential change consisting of a damped oscillation superimposed on a step. Small currents produced symmetrical oscillations at the beginning and end of the pulse. Larger currents increased the initial ringing frequency if depolarizing and decreased it if hyperpolarizing.4. For small currents the frequency of the oscillations and the quality factor (Q) of the electrical resonance derived from the decay of the oscillations were close to the characteristic frequency and Q of the hair-cell linear tuning curve obtained from sound presentations.5. The hair cell's membrane potential change to small-current pulses or low-intensity tone bursts could be largely described by representing the hair cell as a simple electrical resonator consisting of an inductance, resistor and capacitor.6. When step displacements of 29-250 nm were applied to a micropipette, placed just outside a hair cell in the basilar papilla, an initial periodic firing of impulses could be recorded from single fibres in the auditory nerve. Currents of up to 1 nA, injected through the same micropipette, failed to produce any change in the auditory nerve discharge. The experiment demonstrates that current injection does not produce gross movements of the electrode tip.7. The contribution of the electrical resonance to hair-cell tuning was assessed by dividing the linear tuning curve by the cell's impedance as a function of frequency. The procedure assumes that the electrical resonance is independent of other filtering stages, and on this assumption the resonance can account for the tip of the acoustical tuning curve.8. The residual filter produced by the division was broad; it exhibited a high-frequency roll-off with a corner frequency at 500-600 Hz, similar in all cells, and a low-frequency roll-off, with a corner frequency from 30 to 350 Hz which varied from cell to cell but was uncorrelated with the characteristic frequency of the cell.9. The phase of the receptor potential relative to the sound pressure at the tympanum was measured in ten cells. For low intensities the phase characteristic was independent of the sound pressure. At low frequencies the receptor potential led the sound by 270-360 degrees , and in the region of the characteristic frequency there was an abrupt phase lag of 90-180 degrees ; the abruptness of the phase change depended upon the Q of the cell.10. The calculated phase shift of the electrical resonator as a function of frequency was subtracted from the phase characteristic of the receptor potential. The subtraction removed the sharp phase transition around the characteristic frequency, and in this frequency region the residual phase after subtraction was approximately constant at +180 degrees . This is consistent with the idea that the hair cells depolarize in response to displacements of the basilar membrane towards the scala vestibuli. The high-frequency region of the residual phase characteristic was similar in all cells.11. It is concluded that each hair cell contains its own electrical resonance mechanism which accounts for most of the frequency selectivity of the receptor potential. All cells also show evidence of a broad band-pass filter, the high frequency portion of which may be produced by the action of the middle ear.

Temporal ordering deficits following anterior temporal lobectomy

Subjects were required to report the pitch sequence of two 10-msec tones of different frequency presented monaurally while the stimulus onset asynchrony (SOA) between the two tones was varied. The value of the SOA at which the subjects achieved an 80% correct sequence report was determined by an adaptive procedure without feedback. This measure was compared in the right and left ears, on subjects with a right or left anterior temporal lobectomy and on a normal control group. The results reveal an elevated threshold for performing temporal order judgments in the ear contralateral to the surgical lesion.

Ear dominance and sequential interactions.

When two tones of different frequency are simultaneously presented, one to each ear, a single pitch may be heard that corresponds to the frequency delivered to one ear rather than to the other. That is, the frequency information delivered to one ear may be followed and to the other ear suppressed. The present study explored the sequential conditions under which this effect occurs. Clear ear dominance was obtained in sequences where the two ears received the same frequency in succession. However, ear dominance was absent in sequences where successive dichotic chords were composed of different frequencies. From these and other findings a basis for ear dominance is proposed.