scholarly journals Nonlinear temporal receptive fields of neurons in the dorsal cochlear nucleus

2013 ◽  
Vol 110 (10) ◽  
pp. 2414-2425 ◽  
Author(s):  
Sharba Bandyopadhyay ◽  
Eric D. Young
Keyword(s):  
Cochlear Nucleus ◽  
Receptive Fields ◽  
Sound Level ◽  
Second Order ◽  
Dorsal Cochlear Nucleus ◽  
Spectral Processing ◽  
Low Contrast ◽  
Response Properties ◽  
First Order ◽  
Order Components

Studies of the dorsal cochlear nucleus (DCN) have focused on spectral processing because of the complex spectral receptive fields of the DCN. However, temporal fluctuations in natural signals convey important information, including information about moving sound sources or movements of the external ear in animals like cats. Here, we investigate the temporal filtering properties of DCN principal neurons through the use of temporal weighting functions that allow flexible analysis of nonlinearities and time variation in temporal response properties. First-order temporal receptive fields derived from the neurons are sufficient to characterize their response properties to low-contrast (3-dB standard deviation) stimuli. Larger contrasts require the second-order terms. Allowing temporal variation of the parameters of the first-order model or adding a component representing refractoriness improves predictions by the model by relatively small amounts. The importance of second-order components of the model is shown through simulations of nonlinear envelope synchronization behavior across sound level. The temporal model can be combined with a spectral model to predict tuning to the speed and direction of moving sounds.

scholarly journals Receptive Field for Dorsal Cochlear Nucleus Neurons at Multiple Sound Levels

2007 ◽  
Vol 98 (6) ◽  
pp. 3505-3515 ◽  
Author(s):  
Sharba Bandyopadhyay ◽  
Lina A. J. Reiss ◽  
Eric D. Young
Keyword(s):  
Receptive Field ◽  
Cochlear Nucleus ◽  
Weighting Function ◽  
Sound Level ◽  
Second Order ◽  
Dorsal Cochlear Nucleus ◽  
Low Contrast ◽  
Spectral Contrast ◽  
Natural Stimuli ◽  
Frequency Components

Neurons in the dorsal cochlear nucleus (DCN) exhibit nonlinearities in spectral processing, which make it difficult to predict the neurons’ responses to stimuli. Here, we consider two possible sources of nonlinearity: nonmonotonic responses as sound level increases due to inhibition and interactions between frequency components. A spectral weighting function model of rate responses is used; the model approximates the neuron's rate response as a weighted sum of the frequency components of the stimulus plus a second-order sum that captures interactions between frequencies. Such models approximate DCN neurons well at low spectral contrast, i.e., when the SD (contrast) of the stimulus spectrum is limited to 3 dB. This model is compared with a first-order sum with weights that are explicit functions of sound level, so that the low-contrast model is extended to spectral contrasts of 12 dB, the range of natural stimuli. The sound-level–dependent weights improve prediction performance at large spectral contrast. However, the interactions between frequencies, represented as second-order terms, are more important at low spectral contrast. The level-dependent model is shown to predict previously described patterns of responses to spectral edges, showing that small changes in the inhibitory components of the receptive field can produce large changes in the responses of the neuron to features of natural stimuli. These results provide an effective way of characterizing nonlinear auditory neurons incorporating stimulus-dependent sensitivity changes. Such models could be used for neurons in other sensory systems that show similar effects.

Effects of Stimulus Spectral Contrast on Receptive Fields of Dorsal Cochlear Nucleus Neurons

2007 ◽  
Vol 98 (4) ◽  
pp. 2133-2143 ◽  
Author(s):  
Lina A. J. Reiss ◽  
Sharba Bandyopadhyay ◽  
Eric D. Young
Keyword(s):  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Receptive Fields ◽  
Poor Performance ◽  
Nerve Fibers ◽  
Dorsal Cochlear Nucleus ◽  
Good Prediction ◽  
Spectral Processing ◽  
Spectral Contrast ◽  
Spectrotemporal Receptive Field

Neurons in the dorsal cochlear nucleus (DCN) exhibit strong nonlinearities in spectral processing. Low-order models that transform the stimulus spectrum into discharge rate using a combination of first- and second-order weighting of the spectrum (quadratic models) usually fail to predict responses to novel stimuli for principal neurons in the DCN, even though they work well in ventral cochlear nucleus. Here we investigate the effects of spectral contrast on the performance of such models. Typically, the models fail for stimuli with natural-sound–like spectral contrasts (∼12 dB), but have good prediction performance at small (3-dB) contrasts. The weights also typically increase substantially in amplitude at smaller spectral contrast. These changes in weight size with contrast are partly inherited from similar effects seen in auditory nerve fibers, but there must be additional effects from inhibitory circuits in the DCN. These results provide insight into the reasons for the poor performance of spectrotemporal receptive field (STRF) models in predicting responses of auditory neurons. Because the general shapes of the weights do not change between low and high contrast, they also suggest that STRFs may capture meaningful properties of neural receptive fields, even though they do not do well at predicting responses.

scholarly journals Dyslexic children show altered temporal structure of the nonlinear VEP

2019 ◽  
Author(s):  
Sheila Crewther ◽  
Jacqueline Rutkowski ◽  
David Crewther
Keyword(s):  
Visual Field ◽  
Change Detection ◽  
Second Order ◽  
Lower Visual Field ◽  
Perceptual Speed ◽  
Auditory Temporal Processing ◽  
Low Contrast ◽  
First Order ◽  
Upper Visual Field ◽  
Order Kernel

AbstractThe neural basis of dyslexia remains unresolved, despite many theories relating dyslexia to dysfunction in visual magnocellular and auditory temporal processing, cerebellar dysfunction, attentional deficits, as well as excessive neural noise. Recent research identifies perceptual speed as a common factor, integrating several of these systems. Optimal perceptual speed invokes transient attention as a necessary component, and change detection in gap paradigm tasks is impaired in those with dyslexia. This research has also identified an overall better change detection for targets presented in the upper compared with lower visual fields. Despite the magnocellular visual pathway being implicated in the aetiology of dyslexia over 30 years ago, objective physiological measures have been lacking. Thus, we employed nonlinear visual evoked potential (VEP) techniques which generate second order kernel terms specific for magno and parvocellular processing as a means to assessing the physiological status of poor readers (PR, n=12) compared with good readers (GR, n=16) selected from children with a mean age of 10yr. The first and second order Wiener kernels using multifocal VEP were recorded from a 4° foveal stimulus patch as well as for upper and lower visual field peripheral arcs. Foveal responses showed little difference between GR and PR for low contrast stimulation, except for the second slice of the second order kernel where lower peak amplitudes were recorded for PR vs GR. At high contrast, there was a trend to smaller first order kernel amplitudes for short latency peaks of the PR vs GR. In addition, there were significant latency differences for the first negativity in the first two slices of the second order kernel. In terms of peripheral stimulation, lower visual field response amplitudes were larger compared with upper visual field responses, for both PR and GR. A trend to larger second/first order ratio for magnocellularly driven responses suggests the possibility of lesser neural efficiency in the periphery for the PR compared with the GR. Stronger lower field peripheral response may relate to better upper visual field change detection performance when target visibility is controlled through flicking masks. In conclusion, early cortical magnocellular processing at low contrast was normal in those with dyslexia, while cortical activity related to parvocellular afferents was reduced. In addition, the study demonstrated a physiological basis for upper versus lower visual field differences related to magnocellular function.

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