All the other codes discussed here have been single-cell codes, or answers to the question: how does one cell represent information through the pattern of its spiking? The first ALSR representation was for steady-state vowels;  ALSR representations of pitch and formant frequencies in complex, non-steady state stimul were later demonstrated for voiced-pitch,  and formant representations in consonant-vowel syllables. Temporal coding refers to temporal precision in the response that does not arise solely from the dynamics of the stimulus, but that nevertheless relates to properties of the stimulus. One other avenue of argument against rate coding is to point to extremely low jitter, or variance around a mean, in spike timings across multiple presentations of the same stimulus, in systems like the retina. Selectivity for stimulus direction, speed, and orientation". But a single nerve cell can not signal at a rate of 20, Hz. We now know that the cochlear microphonic arises from the sum of electrical potentials in the hair cells of the cochlea. Both the low and high frequencies evoke responses at both positions, but there are more action potentials in response to the high frequency. Additionally, if low firing rates on the order of ten spikes per second must be distinguished from arbitrarily close rate coding for different stimuli, then a neuron trying to discriminate these two stimuli may need to wait for a second or more to accumulate enough information. Correlation structure can increase information content if noise and signal correlations are of opposite sign.
This type of temporal coding has been shown also in the the difference between two bitter tastants, such as quinine and denatonium).
Video: Relationship between place code and temporal codes Classification of Codes
higher-order processing taking place in the brain. Jan 14, Partisans of temporal coding think the sclerotic orthodoxy of rate which put even the slowest-firing neurons of the H-W rate model in the top correlation ( more precisely, calculations of mutual information) than on causation.
With outer hair cell loss, we cannot rely on rate-place coding as much timing and is a representation of the amount of neurons firing in relation to sound waves .
Wever suggested that while one neuron alone could not carry the temporal code for a 20, Hz tone, 20 neurons with staggered firing rates could.
When auditory nerve neurons fire action potentials, they tend to respond at times corresponding to a peak in the sound pressure waveform, i.
The frequency components then shift upward gradually, increasing in frequency over time, but with the amplitude of each component constrained to be that specified by the fixed, non-shifting envelope. They may be characterized by firing rates, rather than as specific spike sequences. The result of this is that there are a bunch of neurons firing near the peak of each and every cycle of a pure tone.
RatePlace and Temporal Codes Understanding the Ear and Outer Hair Cell Loss
However, the interspike interval could be used to encode additional information, which is especially important when the spike rate reaches its limit, as in high-contrast situations.
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|For this reason, temporal coding may play a part in coding defined edges rather than gradual transitions.
Some points are displaced up and others down. If r t varies slowly with time, the code is typically called a rate code, and if it varies rapidly, the code is called temporal.
This is a schematic diagram of the uncurled cochlea. Different auditory nerve fibers attach to different portions of the basilar membrane. What you need for temporal code theory, and to explain the cochlear microphonic is for the neural activity to look just like the sound pressure waveform.
Place and Temporal Code Theories of Pitch Perception. Place coding is weak below Hz because of a broad pattern of oscillation of the basilar. 5 Frequency coding in cochlear nerve fibres. Place code.
Video: Relationship between place code and temporal codes Pitch Discrimination Place Theory
We know that each hair cell occurs in a localised region of the cochlea, and that auditory nerve. HSTJ – Neural Coding and Perception of Sound.
Perception Lecture Notes Frequency Tuning and Pitch Perception
Neural coding of pitch: Temporal and place (Map?) Rate-place or population- rate code. Temporal- place code (all information) . modulation gain is the ratio of the modulation depth.
The cochlea is not a homogeneous piece of tissue. In most sensory systems, the firing rate increases, generally non-linearly, with increasing stimulus intensity. If you shift the tone complex to higher frequencies e.
This is appealing from a metabolic perspective: less energy is used when fewer neurons are firing. Principles of Neural Science 3rd ed.
Revisiting place and temporal theories of pitch
The sparse code is when each item is encoded by the strong activation of a relatively small set of neurons. The dashed lines indicate the envelope of the membrane modulation, the maximum excursion of that bit of membrane throughout the duration of the traveling wave.
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|Main article: Phase precession.
Sparse coding may be a general strategy of neural systems to augment memory capacity. If each spike is independent of all the other spikes in the train, the temporal character of the neural code is determined by the behavior of time-dependent firing rate r t. This figure shows the displacement of the basilar membrane over time, in response to a pure tone stimulus. The image projected onto the retinal photoreceptors changes therefore every few hundred milliseconds.
The sparse code is when each item is encoded by the strong activation of a relatively small set of neurons.