scholarly journals Corticofugal Modulation of the Paradoxical Latency Shifts of Inferior Collicular Neurons

2008 ◽  
Vol 100 (2) ◽  
pp. 1127-1134 ◽  
Author(s):  
Xiaofeng Ma ◽  
Nobuo Suga
Keyword(s):  
Electric Stimulation ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Cortical Stimulation ◽  
Auditory Neurons ◽  
Response Latencies ◽  
Distance Information ◽  
Specific Frequency ◽  
Latency Shift ◽  
Corticofugal Feedback

The central auditory system creates various types of neurons tuned to different acoustic parameters other than a specific frequency. The response latency of auditory neurons typically shortens with an increase in stimulus intensity. However, ∼10% of collicular neurons of the little brown bat show a “paradoxical latency-shift (PLS)”: long latencies to intense sounds but short latencies to weak sounds. These neurons presumably are involved in the processing of target distance information carried by a pair of an intense biosonar pulse and its weak echo. Our current studies show that collicular PLS neurons of the big brown bat are modulated by the corticofugal (descending) system. Electric stimulation of cortical auditory neurons evoked two types of changes in the PLS neurons, depending on the relationship in the best frequency (BF) between the stimulated cortical and recorded collicular neurons. When the BF was matched between them, the cortical stimulation did not shift the BFs of the collicular neurons and shortened their response latencies at intense sounds so that the PLS became smaller. When the BF was unmatched, however, the cortical stimulation shifted the BFs of the collicular neurons and lengthened their response latencies at intense sounds, so that the PLS became larger. Cortical electric stimulation also modulated the response latencies of non-PLS neurons. It produced an inhibitory frequency tuning curve or curves. Our findings indicate that corticofugal feedback is involved in shaping the spectrotemporal patterns of responses of subcortical auditory neurons presumably through inhibition.

Representation of Spectral and Temporal Sound Features in Three Cortical Fields of the Cat. Similarities Outweigh Differences

1998 ◽  
Vol 80 (5) ◽  
pp. 2743-2764 ◽  
Author(s):  
Jos J. Eggermont
Keyword(s):  
Auditory Cortex ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Primary Auditory Cortex ◽  
Temporal Coding ◽  
Modulation Transfer ◽  
Temporal Response ◽  
Response Latencies ◽  
Response Properties ◽  
Sound Features

Eggermont, Jos J. Representation of spectral and temporal sound features in three cortical fields of the cat. Similarities outweigh differences. J. Neurophysiol. 80: 2743–2764, 1998. This study investigates the degree of similarity of three different auditory cortical areas with respect to the coding of periodic stimuli. Simultaneous single- and multiunit recordings in response to periodic stimuli were made from primary auditory cortex (AI), anterior auditory field (AAF), and secondary auditory cortex (AII) in the cat to addresses the following questions: is there, within each cortical area, a difference in the temporal coding of periodic click trains, amplitude-modulated (AM) noise bursts, and AM tone bursts? Is there a difference in this coding between the three cortical fields? Is the coding based on the temporal modulation transfer function (tMTF) and on the all-order interspike-interval (ISI) histogram the same? Is the perceptual distinction between rhythm and roughness for AM stimuli related to a temporal versus spatial representation of AM frequency in auditory cortex? Are interarea differences in temporal response properties related to differences in frequency tuning? The results showed that: 1) AM stimuli produce much higher best modulation frequencies (BMFs) and limiting rates than periodic click trains. 2) For periodic click trains and AM noise, the BMFs and limiting rates were not significantly different for the three areas. However, for AM tones the BMF and limiting rates were about a factor 2 lower in AAF compared with the other areas. 3) The representation of stimulus periodicity in ISIs resulted in significantly lower mean BMFs and limiting rates compared with those estimated from the tMTFs. The difference was relatively small for periodic click trains but quite large for both AM stimuli, especially in AI and AII. 4) Modulation frequencies <20 Hz were represented in the ISIs, suggesting that rhythm is coded in auditory cortex in temporal fashion. 5) In general only a modest interdependence of spectral- and temporal-response properties in AI and AII was found. The BMFs were correlated positively with characteristic frequency in AAF. The limiting rate was positively correlated with the frequency-tuning curve bandwidth in AI and AII but not in AAF. Only in AAF was a correlation between BMF and minimum latency was found. Thus whereas differences were found in the frequency-tuning curve bandwidth and minimum response latencies among the three areas, the coding of periodic stimuli in these areas was fairly similar with the exception of the very poor representation of AM tones in AII. This suggests a strong parallel processing organization in auditory cortex.

scholarly journals Augmentation of Plasticity of the Central Auditory System by the Basal Forebrain and/or Somatosensory Cortex

2003 ◽  
Vol 89 (1) ◽  
pp. 90-103 ◽  
Author(s):  
Xiaofeng Ma ◽  
Nobuo Suga
Keyword(s):  
Somatosensory Cortex ◽  
Auditory System ◽  
Basal Forebrain ◽  
Cortical Neurons ◽  
Electric Stimulation ◽  
Cortical Plasticity ◽  
Frequency Tuning ◽  
Cortical Stimulation ◽  
Cholinergic Basal Forebrain ◽  
Stimulation Of

Auditory conditioning (associative learning) or focal electric stimulation of the primary auditory cortex (AC) evokes reorganization (plasticity) of the cochleotopic (frequency) map of the inferior colliculus (IC) as well as that of the AC. The reorganization results from shifts in the best frequencies (BFs) and frequency-tuning curves of single neurons. Since the importance of the cholinergic basal forebrain for cortical plasticity and the importance of the somatosensory cortex and the corticofugal auditory system for collicular and cortical plasticity have been demonstrated, Gao and Suga proposed a hypothesis that states that the AC and corticofugal system play an important role in evoking auditory collicular and cortical plasticity and that auditory and somatosensory signals from the cerebral cortex to the basal forebrain play an important role in augmenting collicular and cortical plasticity. To test their hypothesis, we studied whether the amount and the duration of plasticity of both collicular and cortical neurons evoked by electric stimulation of the AC or by acoustic stimulation were increased by electric stimulation of the basal forebrain and/or the somatosensory cortex. In adult big brown bats ( Eptesicus fuscus), we made the following major findings. 1) Collicular and cortical plasticity evoked by electric stimulation of the AC is augmented by electric stimulation of the basal forebrain. The amount of augmentation is larger for cortical plasticity than for collicular plasticity. 2) Collicular and cortical plasticity evoked by AC stimulation is augmented by somatosensory cortical stimulation mimicking fear conditioning. The amount of augmentation is larger for cortical plasticity than for collicular plasticity. 3) Collicular and cortical plasticity evoked by both AC and basal forebrain stimulations is further augmented by somatosensory cortical stimulation. 4) A lesion of the basal forebrain tends to reduce collicular and cortical plasticity evoked by AC stimulation. The reduction is small and statistically insignificant for collicular plasticity but significant for cortical plasticity. 5) The lesion of the basal forebrain eliminates the augmentation of collicular and cortical plasticity that otherwise would be evoked by somatosensory cortical stimulation. 6) Collicular and cortical plasticity evoked by repetitive acoustic stimuli is augmented by basal forebrain and/or somatosensory cortical stimulation. However, the lesion of the basal forebrain eliminates the augmentation of collicular and cortical plasticity that otherwise would be evoked by somatosensory cortical stimulation. These findings support the hypothesis proposed by Gao and Suga.

scholarly journals Corticofugal Feedback for Collicular Plasticity Evoked by Electric Stimulation of the Inferior Colliculus

2005 ◽  
Vol 94 (4) ◽  
pp. 2676-2682 ◽  
Author(s):  
Yongkui Zhang ◽  
Nobuo Suga
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Acetylcholine Receptors ◽  
Electric Stimulation ◽  
Frequency Tuning ◽  
Acoustic Stimulus ◽  
Acoustic Stimulation ◽  
Muscarinic Acetylcholine Receptors ◽  
Corticofugal Feedback ◽  
Stimulation Of

Focal electric stimulation of the auditory cortex, 30-min repetitive acoustic stimulation, and auditory fear conditioning each evoke shifts of the frequency-tuning curves [hereafter, best frequency (BF) shifts] of cortical and collicular neurons. The short-term collicular BF shift is produced by the corticofugal system and primarily depends on the relationship in BF between a recorded collicular and a stimulated cortical neuron or between the BF of a recorded collicular neuron and the frequency of an acoustic stimulus. However, it has been unknown whether focal electric stimulation of the inferior colliculus evokes the collicular BF shift and whether the collicular BF shift, if evoked, depends on corticofugal feedback. In our present research with the awake big brown bat, we found that focal electric stimulation of collicular neurons evoked the BF shifts of collicular neurons located near the stimulated ones; that there were two types of BF shifts: centripetal and centrifugal BF shifts, i.e., shifts toward and shifts away from the BF of stimulated neurons, respectively; and that the development of these collicular BF shifts was blocked by inactivation of the auditory cortex. Our data indicate that the collicular BF shifts (plasticity) evoked by collicular electric stimulation depended on corticofugal feedback. It should be noted that collicular BF shifts also depend on acetylcholine because it has been demonstrated that atropine (an antagonist of muscarinic acetylcholine receptors) applied to the IC blocks the development of collicular BF shifts.

scholarly journals Selective Corticofugal Modulation on Sound Processing in Auditory Thalamus of Awake Marmosets

2021 ◽  
Author(s):  
Yuanqing Zhang ◽  
Xiaohui Wang ◽  
Lin Zhu ◽  
Siyi Bai ◽  
Rui Li ◽  
...  
Keyword(s):  
Sensory Processing ◽  
Frequency Tuning ◽  
Signal To Noise Ratio ◽  
Medial Geniculate Body ◽  
Primary Auditory Cortex ◽  
Medial Geniculate ◽  
Auditory Response ◽  
Corticofugal Feedback ◽  
Corticothalamic Feedback

Cortical feedback has long been considered crucial for modulation of sensory processing. In the mammalian auditory system, studies have suggested that corticofugal feedback can have excitatory, inhibitory, or both effects on the response of subcortical neurons, leading to controversies regarding the role of corticothalamic influence. This has been further complicated by studies conducted under different brain states. In the current study, we used cryo-inactivation in the primary auditory cortex (A1) to examine the role of corticothalamic feedback on medial geniculate body (MGB) neurons in awake marmosets. The primary effects of A1 inactivation were a frequency-specific decrease in the auditory response of MGB neurons coupled with an increased spontaneous firing rate, which together resulted in a decrease in the signal-to-noise ratio. In addition, we report for the first-time that A1 robustly modulated the long-lasting sustained response of MGB neurons which changed the frequency tuning after A1 inactivation, e.g., neurons with sharp tuning increased tuning bandwidth whereas those with broad tuning decreased tuning bandwidth. Taken together, our results demonstrate that corticothalamic modulation in awake marmosets serves to enhance sensory processing in a way similar to center-surround models proposed in visual and somatosensory systems, a finding which supports common principles of corticothalamic processing across sensory systems.

The Study of Spatial Frequency Channels for Human Visual System

2019 ◽  
Vol 33 (06) ◽  
pp. 1955007
Author(s):  
Xiangyang Xu ◽  
Qiao Chen ◽  
Ruixin Xu
Keyword(s):  
Receptive Field ◽  
Spatial Frequency ◽  
Visual System ◽  
Human Visual System ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Vision System ◽  
Human Vision ◽  
Psychophysical Experiment ◽  
Human Vision System

Similar to auditory perception of sound system, color perception of the human visual system also presents a multi-frequency channel property. In order to study the multi-frequency channel mechanism of how the human visual system processes color information, the paper proposed a psychophysical experiment to measure the contrast sensitivities based on 17 color samples of 16 spatial frequencies on CIELAB opponent color space. Correlation analysis was carried out on the psychophysical experiment data, and the results show obvious linear correlations of observations for different spatial frequencies of different observers, which indicates that a linear model can be used to model how human visual system processes spatial frequency information. The results of solving the model based on the experiment data of color samples show that 9 spatial frequency tuning curves can exist in human visual system with each lightness, R–G and Y–B color channel and each channel can be represented by 3 tuning curves, which reflect the “center-around” form of the human visual receptive field. It is concluded that there are 9 spatial frequency channels in human vision system. The low frequency tuning curve of a narrow-frequency bandwidth shows the characteristics of lower level receptive field for human vision system, the medium frequency tuning curve shows a low pass property of the change of medium frequent colors and the high frequency tuning curve of a width-frequency bandwidth, which has a feedback effect on the low and medium frequency channels and shows the characteristics of higher level receptive field for human vision system, which represents the discrimination of details.

The effect of threshold on the relationship between the receptive-field profile and the spatial-frequency tuning cure in simple cells of the cat's striate cortex

1989 ◽  
Vol 3 (5) ◽  
pp. 445-454 ◽  
Author(s):  
Y. Tadmor ◽  
D. J. Tolhurst
Keyword(s):  
Fourier Transform ◽  
Spatial Frequency ◽  
Fourier Transforms ◽  
Frequency Tuning ◽  
Weighting Function ◽  
Tuning Curve ◽  
Spatial Summation ◽  
Response Threshold ◽  
Simple Cells ◽  
Spatial Frequency Tuning

AbstractIt is believed that spatial summation in most simple cells is a linear process. If this were so, then the Fourier transform of a simple cell's line weighting function should predict the cell's spatial frequency tuning curve. We have compared such predictions with experimental measurements and have found a consistent discrepancy: the predicted tuning curve is much too broad. We show qualitatively that this kind of discrepancy is consistent with the well-known threshold nonlinearity shown by most cortical cells. We have tested quantitatively whether a response threshold could explain the observed disagreements between predictions and measurements: a least-squares minimization routine was used to fit the inverse Fourier Transform of the measured frequency tuning curve to the measured line weighting function. The fitting procedure permitted us to introduce a threshold to the reconstructed line weighting function. The results of the analysis show that, for all of the cells tested, the Fourier transforms produced better predictions when a response threshold was included in the model. For some cells, the actual magnitude of the response threshold was measured independently and found to be compatible with that suggested by the model. The effects of nonlinearities of spatial summation are considered.

Spatial map of frequency tuning-curve shapes in the mouse inferior colliculus

Neuroreport ◽  
2003 ◽  
Vol 14 (10) ◽  
pp. 1365-1369 ◽  
Author(s):  
Günter Ehret ◽  
Marina Egorova ◽  
Steffen R. Hage ◽  
Birgit A. Müller
Keyword(s):  
Inferior Colliculus ◽  
Frequency Tuning ◽  
Tuning Curve

Comparison of contrast-normalization and threshold models of the responses of simple cells in cat striate cortex

1997 ◽  
Vol 14 (2) ◽  
pp. 293-309 ◽  
Author(s):  
D. J. Tolhurst ◽  
D. J. Heeger
Keyword(s):  
Receptive Field ◽  
Striate Cortex ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Threshold Model ◽  
Output Stage ◽  
Simple Cells ◽  
Neurophysiological Data ◽  
Contrast Normalization ◽  
The Relationship

AbstractIn almost every study of the linearity of spatiotemporal summation in simple cells of the cat's visual cortex, there have been systematic mismatches between the experimental observations and the predictions of the linear theory. These mismatches have generally been explained by supposing that the initial spatiotemporal summation stage is strictly linear, but that the following output stage of the simple cell is subject to some contrast-dependent nonlinearity. Two main models of the output nonlinearity have been proposed: the threshold model (e.g. Tolhurst & Dean, 1987) and the contrast-normalization model (e.g. Heeger, 1992a, b). In this paper, the two models are fitted rigorously to a variety of previously published neurophysiological data, in order to determine whether one model is a better explanation of the data. We reexamine data on the interaction between two bar stimuli presented in different parts of the receptive field; on the relationship between the receptive-field map and the inverse Fourier transform of the spatial-frequency tuning curve; on the dependence of response amplitude and phase on the spatial phase of stationary gratings; on the relationships between the responses to moving and modulated gratings; and on the suppressive action of gratings moving in a neuron's nonpreferred direction. In many situations, the predictions of the two models are similar, but the contrast-normalization model usually fits the data slightly better than the threshold model, and it is easier to apply the equations of the normalization model. More importantly, the normalization model is naturally able to account very well for the details and subtlety of the results in experiments where the total contrast energy of the stimuli changes; some of these phenomena are completely beyond the scope of the threshold model. Rigorous application of the models' equations has revealed some situations where neither model fits quite well enough, and we must suppose, therefore, that there are some subtle nonlinearities still to be characterized.

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