Neural Discharge Patterns Research Articles

Transient changes in neural discharge patterns may enhance the separation of concurrent vowels with different fundamental frequencies

Two vowels presented concurrently are better identified by human listeners when their fundamentals (F0’s) differ. Neurophysiological correlates of this phenomenon were investigated using single fiber recordings from the auditory nerve of anesthetized cats. Results show that aggregate interspike interval distributions (the summed autocorrelation histograms of many fibers with different CF’s) contain sufficient information to characterize single vowels. When two concurrent vowels have the same F0, the resulting interval distributions resemble that of one ‘‘dominant’’ vowel constituent. When the two vowels have different F0’s, running interval distributions additionally show short time segments when they resemble the other, ‘‘nondominant’’ vowel. These short time segments and accompanying changes in interval distributions are associated with shifting relative onset times of vowel periods (i.e., changes in vowel period alignments) created by the different F0’s. Particular period alignments can enhance or diminish the similarity of the interval distribution with that of either vowel constituent. These results along with recent psychophysical findings [P. Assmann and Q. Summerfield, J. Acoust. Soc. Am. 95, 471–484 (1994)] suggest that differences in F0 may allow the auditory system to ‘‘hear out’’ each vowel in moments when period alignments are favorable. [Work supported by NIH DC00119.]

Reaction time distributions and their relationship to the transient/sustained nature of the neural discharge

Reaction time distributions (RTDs) were determined in response to near-threshold increments of long duration. Stimulus parameters were selected to isolate the chromatic and achromatic systems. The RTDs for the achromatic system peak sooner and are more narrow than those obtained for the chromatic system. These results are analyzed in terms of the neural discharge pattern of parvo and magno pathways.

Neural correlates of nonmonotonic temporal acuity for voice onset time

Human and chinchilla listeners exhibit nonmonotonic temporal acuity for speech sounds differing in voice onset time (VOT). Characteristics of the neural discharge pattern or of the stimuli themselves that might account for the pattern of temporal acuity have not been described. Responses of chinchilla auditory-nerve fibers to syllables from an alveolar VOT continuum were measured. Peak discharge rates and peak response latencies elicited by the syllables with the shortest and longest VOTs were highly variable across groups of neurons with similar characteristic frequencies. For VOTs from the middle of the continuum, peak responses were larger, and response latencies were nearly constant across the same group of neurons. Overall, the magnitude and temporal variability of the responses of populations of primary auditory neurons varied nonmonotonically with VOT, consistent with the pattern of psychophysical temporal acuity for these syllables exhibited by humans and chinchillas. Spectral analyses suggested by the pattern of neural responses indicated that synchronous or correlated spectral cues were available over a wider bandwidth for those syllables from the middle of the continuum for which the neural representation was least variable.

The representation of the spectra and fundamental frequencies of steady-state single- and double-vowel sounds in the temporal discharge patterns of guinea pig cochlear-nerve fibers

Psychophysical results using double vowels imply that subjects are able to use the temporal aspects of neural discharge patterns. To investigate the possible temporal cues available, the responses of fibers in the cochlear nerve of the anesthetized guinea pig to synthetic vowels were recorded at a range of sound levels up to 95 dB SPL. The stimuli were the single vowels /i/ [fundamental frequency (f0) 125 Hz], /a/ (f0, 100 Hz), and /c/ (f0, 100 Hz) and the double vowels were /a(100),i(125)/ and /c(100),i(125)/. Histograms synchronized to the period of the double vowels were constructed, and locking of the discharge to individual harmonics was estimated from them by Fourier transformation. One possible cue for identifying the f0's of the constituents of a double vowel is modulation of the neural discharge with a period of 1/f0. Such modulation was found at frequencies between the formant peaks of the double vowel, with modulation at the periods of 100 and 125 Hz occurring at different places in the fiber array. Generation of a population response based on synchronized responses [average localized synchronized rate (ALSR): see Young and Sachs [J. Acoust. Soc. Am. 66, 1381-1403 (1979)] allowed estimation of the f0's by a variety of methods and subsampling the population response at the harmonics of the f0 of the constituent vowel achieved a good reconstruction of its spectrum. Other analyses using interval histograms and autocorrelation, which overcome some problems associated with the ALSR approach, also allowed f0 identification and vowel segregation. The present study has demonstrated unequivocally that the timing of the impulses in auditory-nerve fibers provides copious possible cues for the identification of the fundamental frequencies and spectra associated with each of the constituents of double vowels.

Superposition models of the discharge patterns of units in the lower auditory system.

Superposition of point processes has often been suggested as an abstract model for the generation of neural discharge patterns due to its simplicity (input spike trains are simply merged and then retransmitted by the model neuron). The properties of the superposition of two renewal processes are examined in relation to the properties of its components. A satisfactory condition is found so that the superposition of two renewal processes possesses negative serial dependence of intervent intervals. However, the imposition of a dead time of approximately the same duration as that of the components on their superposition process is shown to remove much of this dependence. Thus, the adequacy of the simple superposition of renewal processes as a model for discharge patterns from regions that are typified by negative serial dependence (such as the lateral superior olive) may be limited, but may suffice for the discharges of primary-like units.

Brainwave signatures — An index reflective of the brain's functional neuroanatomy: Further findings on the effect of EEG sensorimotor rhythm biofeedback training on the neurologic precursors of learning disabilities

Eight boys, ages 7 years 11 months to 15 years 3 months, were provided withlong-term—symptom duration—sensorimotor rhythm biofeedback training for the remediation of their learning disabilities. Concurrently, the simultaneous recording of five frequency bands of brainwave activity (5 Hz, 7 Hz, 10 Hz, 12 Hz and 14 Hz), from one active electrode equidistant from reference and ground, was intended to provide a glimpse of the ‘brainwave signature’ reflective of the dynamic and synergistic processes involved in such cerebro-neural activation and the brain's global response to such an alteration in the sensorimotor subnetwork. Overall, the main effect of this procedure, for the biofeedback and subsequent conditioning of increased 14 Hz neural discharge patterns over the central Rolandic cortex in a clinical office setting, seems to be increase bilateral sensorimotor transactions resulting in substantive remediation of the learning disabilities of the recipients of such training—by way of internally exercising of, and/or recruitment of additional neural activation within, the sensorimotorsubnetwork/matrix. Observation of the changing brainwave signatures showed a tendency for decreased slow were activity concommitant with increases in fast wave activity, for cases with a Full Scale I.Q. within the range of 76 and 85; with those cases with a Full Scale I.Q. within the range of 102 and 116 exhibiting increased amplitudes over most of the monitored bands, but with the increases being much less at the slower frequencies. It is noteworthy that those four subjects with either a significant Verbal greater than Performance, or Performance greater than Verbal, I.Q. Score discrepancy exhibited no less than a 40% greater increase in the lower of the two I.Q. scores; indicating that this SMR training procedure also resulted in an increased symmetry in the interhemispheric interactions reflective of the higher cortical functions for these no longer learning disabled boys.

Serial dependence in a superposition of renewal processes

Superposition of point processes has often been suggested [I. Gath, Math. Biosci. 22, 211–222 (1974); C. E. Molnar and R. R. Pfeiffer, Proc. IEEE 56, 993–1004 (1968)] as a model for neural discharge patterns due to its intuitive appeal (input spike trains are simply merged and then retransmitted), and the tendency for successive interspike intervals in the superposition to be negatively correlated. Discharge patterns in the lateral superior olive (LSO) of the cat often display such negative serial dependence. The properties of the superposition of two identical renewal processes are examined in relation to the properties of its components. Components with increasing intensity functions are proven to yield a superposition process having negative serial dependence. However, the imposition of a dead time on a superposition process is shown to remove much of the serial dependence. For this reason, it is suggested that superposition of renewal processes is not a good model for discharge patterns having both a dead time and significant serial dependence, such as LSO discharge patterns.

Ontogeny of neural discharge patterns in the ventral cochlear nucleus of the Mongolian gerbil

Discharge patterns were recorded extracellularly from single neurons in the ventral cochlear nucleus (VCN) of Mongolian gerbils ranging in age from 10 days after birth (DAB) to adult, a period which includes the onset of responsiveness to acoustic stimulation. At 10 DAB none of the neurons encountered within the VCN responded to acoustic stimulation. At 12 DAB approximately 15% of the neurons isolated in VCN were responsive. This coincided with the earliest cochlear microphonic potentials and preceded the appearance of the cochlear compound action potential (AP) by two days. At 14 DAB, or older, the great majority of neurons isolated in VCN responded to acoustic stimulation. Most parameters of VCN neural function exhibited significant changes between 12 and 18 DAB: neural thresholds improved approximately 100 dB; mean spontaneous discharge rate increased; the high-frequency range of characteristic frequency (CF) values increased from 10.0 to 24.0 kHz; the upper limit for phase locking increased from 0.8 kHz to 3.0 kHz; dynamic range increased from 16 dB to 44 dB, and the proportion of units with well-defined initial onset peaks in their post-stimulus-time (PST) response patterns increased from 40% to 100% of units. Most of the neural parameters examined achieved adult characteristics by 18 DAB. Frequency tuning (Q10dB) matured earlier for high-CF units. The most sharply tuned neurons with high CFs (>4 kHz) at 12 DAB had Q10dB values equal to those for adults. None of the neurons with low CFs (<4 kHz) had Q10dB values greater than 1.2 at this age. Classical ‘on’ PST response patterns were not seen at 12 and 14 DAB. A unique PST response type, characterized by very long latency phasic discharge, was observed only at 12 DAB. None of the VCN neurons recorded from 12 DAB subjects displayed rhythmic ‘bursting’ or ‘pulsing’ PST response patterns, as has been reported at the earliest stages of functional development in the VCN of the cat. Most units were capable of sustained discharge, even with long stimulus durations. Units with ‘primary-like’ PST response patterns at 12 exhibited greater variability in first spike latency and less pronounced initial rates of firing than was characteristic in adults, resulting in poorly defined onset peaks. In contrast, units with chopper PST response patterns showed well-defined onset peaks.

EEG sensorimotor rhythm biofeedback training: Some effects on the neurologic precursors of learning disabilities

This study presents a clinical treatment regime for pathological interhemispheric dysfunction with respect to a population of learning disabled boys. The results obtained replicate and extend earlier findings with respect to operantly conditioned increases in amplitude of sensorimotor transactions and its positive effect on learning disability. Specifically, the biofeedback, and subsequent conditioning, of increased 14 Hz neural discharge patterns (sensorimotor rhythm — SMR) over the central Rolandic cortex, appeared to increase bilateral sensorimotor transactions resulting in substantive reduction/remediation in the learning disabilities of the recipients of such EEG biofeedback training.

Initial mechanisms basic to olfactory perception

Animal experimentation has proposed three mechanisms at the olfactory mucosa that may underlie olfactory discrimination. First, the olfactory receptor cells appear selectively tuned to different odorants. Second, in a gas chromatographic-like process, the molecules of different odorants appear to be distributed in different sorption patterns across the mucosal surface. Third, different regions of the mucosa appear to have different selective sensitivities. These three mechanisms could complement each other by together generating a greater number of neural discharge patterns to encode the odorants passing over the mucosal surface. In this interplay, the mucosal distribution patterns could differentially limit the receptor cells and mucosal regions to which different odorants have access. The mucosal distribution pattern could thereby affect the odorant analyses made by these other mechanisms as well as contribute its own analysis. The mucosal distribution patterns appear fairly stable in the face of rather wide variations in the pertinent variables characterizing the nasal airflow (namely, odorant concentration, flow rate, volume, and duration). There are, however, limits to these variables beyond which significant shifts in the molecular distributions and neural discharge patterns can be produced. Thus, in humans any naturally occurring or surgically induced alteration in the nasal airflow which appreciably alters these variables may affect olfactory perception. Olfaction in a laryngectomized patient is discussed as an example.

Response Characteristics of Cochlear Nucleus Neurons to Vowel Sounds

Most studies in auditory neurophysiology have utilized tonal stimuli to determine the coding properties of neurons in the cochlear nuclei. In this investigation of the kangaroo rat, cochlear nuclei, neuronal responses to vowel sounds, as well as tones, were studied. The vowel sounds, each about 40 msec in duration were: see article. Five were linked together to form a 200 msec stimulus and various combinations of five vowel sounds provided us with 18 different stimuli. The results show that neurons in the cochlear nuclei are remarkably sensitive and selective to vowel sounds. Furthermore, the responses of these neurons to pure tones do not provide a complete basis to predict the types of responses to the vowel sounds. More significant is the finding that the neural discharge rate and pattern of discharge to a particular vowel may depend on where the vowel appears in the stimulus and what other vowel precedes it. This vowel positional effect is not the same for every neuron. We have called this phenomenon a neural "set".

Response of neurons of the dorsal and posteroventral cochlear nuclei of the cat to acoustic stimuli of long duration.

Response of neurons of the dorsal and posteroventral cochlear nuclei of the cat to acoustic stimuli of long duration.J M Goldberg, and D D GreenwoodJ M Goldberg, and D D GreenwoodPublished Online:01 Jan 1966https://doi.org/10.1152/jn.1966.29.1.72MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySpectral Composition of Concurrent Noise Affects Neuronal Sensitivity to Interaural Time Differences of Tones in the Dorsal Nucleus of the Lateral LemniscusIda Siveke, Christian Leibold, and Benedikt Grothe1 November 2007 | Journal of Neurophysiology, Vol. 98, No. 5Noise Shaping by Interval Correlations Increases Information Transfer25 February 2004 | Physical Review Letters, Vol. 92, No. 8Regularity of Firing of Neurons in the Inferior ColliculusAdrian Rees, Ali Sarbaz, Manuel S. Malmierca, and Fiona E. N. Le Beau1 June 1997 | Journal of Neurophysiology, Vol. 77, No. 6Increment detection of bandlimited noises in the chinchillaHearing Research, Vol. 66, No. 1The intensitive DL of tones: Dependence of signal/masker ratio on tone level and on spectrum of added noiseHearing Research, Vol. 65, No. 1-2Critical bandwidth and consonance in relation to cochlear frequency-position coordinatesHearing Research, Vol. 54, No. 2Critical bandwidth and consonance: Their operational definitions in relation to cochlear nonlinearity and combination tonesHearing Research, Vol. 54, No. 2Auditory nerve of the normal and jaundiced rat. I. Spontaneous discharge rate and cochlear nerve histologyHearing Research, Vol. 54, No. 1Separate mechanisms control spike numbers and inter-spike intervals in transient responses of cat auditory cortex neuronsHearing Research, Vol. 53, No. 1Cochlear nonlinearity and gain control as determinants of the response of primary auditory neurons to harmonic complexesHearing Research, Vol. 32, No. 2-3Ontogeny of neural discharge patterns in the ventral cochlear nucleus of the Mongolian gerbilDevelopmental Brain Research, Vol. 17, No. 1-2Noise masking of tone responses and critical ratios in single units of the mouse cochlear nerve and cochlear nucleusHearing Research, Vol. 14, No. 1Single unit analysis of the posteroventral cochlear nucleus of the decerebrate catNeuroscience, Vol. 7, No. 8Intensity coding in the auditory periphery of the cat: Responses of cochlear nerve and cochlear nucleus neurons to signals in the presence of bandstop masking noiseHearing Research, Vol. 7, No. 3A comparison of acoustic nerve and cochlear nucleus responses during acoustic habituationBrain Research, Vol. 173, No. 3Chopper units recorded in the cochlear nucleus of the awake catNeuroscience Letters, Vol. 7, No. 4Postnatal maturation of the cochlear nuclei in the cat: A neurophysiological studyBrain Research, Vol. 83, No. 2Discharge charateristics of neurons in anteroventral and dorsal cochlear nuclei of catBrain Research, Vol. 64Response of cat cochlear nucleus neurons to frequency and amplitude modulated tonesBrain Research, Vol. 45, No. 2A chronically implantable multiple micro-electrode system with independent control of electrode positionsElectroencephalography and Clinical Neurophysiology, Vol. 29, No. 6Tone response patterns of the auditory nuclei during normal wakefulness, paralysis, and anesthesiaBrain Research, Vol. 15, No. 2A computer simulated model of a second order sensory neuroneKybernetik, Vol. 6, No. 4A biological model of the excitation of a second order sensory neuroneKybernetik, Vol. 6, No. 4Progressive alterations in cochlear nucleus, inferior colliculus, and medial geniculate responses during acoustic habituationExperimental Neurology, Vol. 25, No. 1A technique for the chronic implantation of multiple movable micro-electrodesElectroencephalography and Clinical Neurophysiology, Vol. 27, No. 2Poststimulus-time response patterns in the nuclei of the cat superior olivary complexExperimental Neurology, Vol. 23, No. 2 More from this issue > Volume 29Issue 1January 1966Pages 72-93 https://doi.org/10.1152/jn.1966.29.1.72PubMed5901613History Published online 1 January 1966 Published in print 1 January 1966 Metrics

Properties of synaptic activities and spike potentials of neurons in immature neocortex.

Properties of synaptic activities and spike potentials of neurons in immature neocortex.