Bats and frogs and animals in between: evidence for a common central timing mechanism to extract periodicity pitch (original) (raw)
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Timing in the Auditory System of the Bat
Annual Review of Physiology, 1999
Echolocating bats use audition to guide much of their behavior. As in all vertebrates, their lower brainstem contains a number of parallel auditory pathways that provide excitatory or inhibitory outputs differing in their temporal discharge patterns and latencies. These pathways converge in the auditory midbrain, where many neurons are tuned to biologically important parameters of sound, including signal duration, frequency-modulated sweep direction, and the rate of periodic frequency or amplitude modulations. This tuning to biologically relevant temporal patterns of sound is created through the interplay of the time-delayed excitatory and inhibitory inputs to midbrain neurons. Because the tuning process requires integration over a relatively long time period, the rate at which midbrain auditory neurons respond corresponds to the cadence of sounds rather than their fine structure and may provide an output that is closely matched to the rate at which motor systems operate.
Dynamic temporal signal processing in the inferior colliculus of echolocating bats
Frontiers in neural circuits, 2012
In nature, communication sounds among animal species including humans are typical complex sounds that occur in sequence and vary with time in several parameters including amplitude, frequency, duration as well as separation, and order of individual sounds. Among these multiple parameters, sound duration is a simple but important one that contributes to the distinct spectral and temporal attributes of individual biological sounds. Likewise, the separation of individual sounds is an important temporal attribute that determines an animal's ability in distinguishing individual sounds. Whereas duration selectivity of auditory neurons underlies an animal's ability in recognition of sound duration, the recovery cycle of auditory neurons determines a neuron's ability in responding to closely spaced sound pulses and therefore, it underlies the animal's ability in analyzing the order of individual sounds. Since the multiple parameters of naturally occurring communication sound...
Journal of Comparative Physiology A, 2011
Frequency tuning, temporal response pattern and latency properties of inferior colliculus neurons were investigated in the big fruit-eating bat, Artibeus jamaicensis. Neurons having best frequencies between 48-72 kHz and between 24-32 kHz are overrepresented. The inferior colliculus neurons had either phasic (consisting in only one response cycle at all stimulus intensities) or long-lasting oscillatory responses (consisting of multiple response cycles). Seventeen percent of neurons displayed paradoxical latency shift, i.e. their response latency increased with increasing sound level. Three types of paradoxical latency shift were found: (1) stable, that does not depend on sound duration, (2) duration-dependent, that grows with increasing sound duration, and (3) progressive, whose magnitude increases with increasing sound level. The temporal properties of paradoxical latency shift neurons compare well with those of neurons having long-lasting oscillatory responses, i.e. median inter-spike intervals and paradoxical latency shift below 6 ms are overrepresented. In addition, oscillatory and paradoxical latency shift neurons behave similarly when tested with tones of diVerent durations. Temporal properties of oscillation and PLS found in the IC of fruiteating bats are similar to those found in the IC of insectivorous bats using downward frequency-modulated echolocation calls.
Time and frequency domain processing in the inferior colliculus of echolocating bats
Hearing Research, 1981
Tone bursts and frequency-modulated (FM) signals were presented to Mexican free-tailed bats and tuning curves, discharge patterns, and discharge latencies of single units in the inferior colliculus were recorded. Cells were broadly tuned to tone bursts, with most Q 10 values ranging from 3 to 20. However, in response to FM stimulation the discharges of neurons were closely synchronized to the time of occurrence of restricted frequency components within the FM sweep. These excitatory frequencies (EFs) were generally unaffected by changes in the starting frequency or intensity of the stimulus. Thus, in response to FM signals, the cells exhibited a much greater frequency selectivity than that observed following tone burst stimulation. Across the population of neurons sampled, EFs covering a wide frequency range were found, and the different EFs were represented in a systematic fashion within the colliculus. The frequencies in an FM biosonar signal or echo will thus be neurally represented both by the time of occurrence of neuronal discharges and by the location of the discharging cells within the nucleus. The potential role of this dual frequency coding in spectral and temporal processing of biosonar signals and echoes is discussed, with emphasis on the neural coding of target range.
Journal of Comparative Physiology A, 1991
Response characteristics of 130 single neurons in the superior olivary nucleus of the northern leopard frog (Rana pipiens pipiens) were examined to determine their selectivity to various behaviorally relevant temporal parameters [rise-fall time, duration, and amplitude modulation (AM) rate] of acoustic signals. Response functions were constructed with respect to each of these variables. Neurons with different temporal firing patterns such as tonic, phasic or phasic-burst firing patterns, participated in time domain analysis in specific manners. Phasic neurons manifested preferences for signals with short rise-fall times, thus possessing low-pass response functions with respect to this stimulus parameter; conversely, tonic and phasic-burst units were nonselective and possessed all-pass response functions. A distinction between temporal firing patterns was also observed for duration coding. Whereas phasic units showed no change in the mean spike count with a change in stimulus duration (i.e., all-pass duration response functions), tonic and phasic-burst units gave higher mean spike counts with an increase in stimulus duration (i.e., primary-like high-pass response functions). Phasic units manifested greater response selectivity for AM rate than did tonic or phasic-burst units, and many phasic units were tuned to a narrow range of modulation rates (i.e., band-pass). The results suggest that SON neurons play an important role in the processing of complex acoustic patterns; they perform extensive computations on AM rate as well as other temporal parameters of complex sounds. Moreover, the response selectivities for rise-fall time, duration, and AM rate could often be Abbreviations: SON superior olivary nucleus; DMN dorsal medullary nucleus; TS torus semicircularis; FTC frequency threshold curve; BF best excitatory frequency; PAM pulsatile amplitude modulation; SAM sinusoidal amplitude modulation; SQAM square-wave amplitude modulation; MTF modulation transfer function; PSTH peri-stimulus time histogram shown to contribute to the differential responses to complex synthetic and natural sounds.