Discharge Patterns Of Single Fibers Research Articles

Laryngeal afferent inputs during vocalization in the cat.

To reveal the kind of information about the larynx which is transmitted to the central nervous system during vocalization, we studied discharge patterns of single fibers of the laryngeal afferent nerve during electrically induced vocalization in ketamine-anesthetized cats. Recorded fibers were classified into four types based on their discharge patterns. Type A fibers responded to vocal fold vibration during vocalization. Type B fibers increased their activity during vocalization without synchronization with vocal fold vibration. Type C fibers decreased their activity during vocalization. Type D fibers discharged only at the onset of vocal fold adduction and abduction. We discuss the functional properties of these afferents and the possibility that these afferent inputs participate in the feedback control of vocalization.

Variable effects of click polarity on auditory brain-stem response latencies: analyses of narrow-band ABRs suggest possible explanations.

The auditory brain-stem responses (ABRs) to rarefaction and condensation clicks were obtained for 12 normal-hearing subjects in quiet, and high-pass masking at 8, 4, 2, 1, and 0.5 kHz. Derived narrow-band wave V latency differences were analyzed with respect to (1) stimulus polarity, (2) absolute differences irrespective of polarity. The analyses revealed no significant stimulus polarity effects on latency for the derived bands. Absolute latency differences regardless of polarity tended to be greater for those derived bands having lower characteristic frequencies (CFs). However, these differences were smaller than the expected half-period of the theoretical CF. Further analyses in three additional subjects using repeated runs of the same polarity indicate that this increase in absolute latency difference with lower derived band CF does not reflect a simple half-period change owing to polarity, but rather to the increase variability in measuring the peak latency of the lower CF derived bands. The variability is consistent with variability of eighth nerve PST histograms behavior observed in animal work [Kiang et al., "Discharge patterns of single fibers in the cat's auditory nerve," Research Monograph No. 35 (MIT, Cambridge, MA, 1965)]. Thus claimed polarity effects observed in other ABR work using absolute values may have been affected by this variability. It appears from these current data that half-period latency shifts of wave V owing to stimulus polarity differences are not observed in derived bands responses initiated from frequency specific regions of the cochlea.

Unusual discharge patterns of single fibers in the pigeon's auditory nerve.

Extracellular recording from single auditory nerve fibers in the pigeon, Columba livia, revealed some unusual discharge patterns of spontaneous and evoked activity. Time interval histograms (TIHs) of spontaneous activity showed a random interval distribution in 73% of the auditory fibers (Fig. 1a). The remaining 27% revealed periodicity in the TIHs (Fig. 1b-e), determined by the characteristic frequency (CF) of a given fiber. Normally, those fibers had a CF less than 2.2 kHz. In both cases spontaneous activity was irregular. The time pattern of quasiperiodic spontaneous firing in different auditory fibers is described by three main types of autocorrelation histograms (ACHs; decaying, nondecaying, and modulated), reflecting the spontaneous oscillations of the hair cell membrane potential (Fig. 1b-d). Single-tone suppression in auditory fibers with quasi-periodic spontaneous activity was found (Figs. 2, 10) and it could be observed if the eighth nerve was cut. There was no suppressive effect in fibres with random spontaneous firing. The frequency selectivity properties of auditory fibers were studied by means of an automatic method. Both 'simple' (Fig. 4) and 'complex' (Figs. 7, 8) response maps were found. Apart from the usual excitatory area, complex response maps were characterized by suppressive areas lying either above (Fig. 7), below (Fig. 8e), or on both sides of the CF (Fig. 8a-c). Generally, complex response maps were observed for fibers showing quasiperiodic spontaneous activity (Figs. 7, 8). Input-output functions at frequencies evoking single-tone suppression were nonmonotonic, while they were always monotonic at frequencies near the CF (Fig. 12). No difference in sharpness was observed between normal frequency threshold curves (FTCs) and excitatory areas of 'complex' response maps (Fig. 9). 'On-off' responses evoked by suppressive stimuli were found (Figs. 2, 3). They had a periodic pattern determined by the CF and did not depend on the stimulus frequency (Fig. 3). Low-CF fibers were observed which changed their time discharge structure to tone levels about 45 dB lower than their thresholds at the CF (Fig. 6). The observed features of the discharge patterns of the pigeon's auditory fibers reflect the distinctive nature of the fundamental mechanisms of auditory analysis in birds that are connected with electrical tuning of the hair cells and probably with the micromechanics of the bird's cochlea.

Discharge patterns of single fibers in the pigeon auditory nerve

The discharge patterns of single fibers in the auditory nerve of ketamine anesthetized pigeons were studied and compared with unit responses in cats studied under similar conditions. All fibers show spontaneous activity; rates of spontaneous activity were generally higher than those in mammalian auditory nerve fibers. Temporal patterns of responses to tones were similar to those of mammalian fibers. Phase-locking of discharges was observed for tone frequencies at least as high as 4 kHz. For frequencies below 100 Hz, two or more spikes could occur per cycle. Tuning curves were similar in shape and sharpness to those of mammalian fibers. Characteristic frequencies were in the range 0.1–6.0 kHz. For CFs below 3.5 kHz, fiber thresholds followed behavioral thresholds quite closely; for higher CFs fiber thresholds were about 10 dB higher than behavioral thresholds. Maximum response rates to single tones were higher in pigeon than in cat. Two-tone inhibition was demonstrated. Spontaneous activity was not inhibited by acoustic stimuli. Click-response histograms showed multiple peaks separated by the reciprocal of fiber CF. Ten or more peaks could be observed in response to a single click. Click latencies were less than 1.4 msec for fibers with CFs greater than 1.8 kHz. For lower CFs, latency increased with decreasing CF. Iso-rate contours for single fibers showed evidence of non-linearity similar to that observed in the vibration patterns of the basilar membrane24. We conclude, therefore, that the structurally different avian and mammalian cochleae lead to auditory nerve discharge patterns which are similar in almost all details except average rates of activity.

Review of Discharge Patterns of Single Fibers in the Cat's Auditory Nerve.

Review of Discharge Patterns of Single Fibers in the Cat's Auditory Nerve.